BB Mopar "906" Head Rebuild, Costs vrs Flow/Perf Potential

[Challenger340]

Going to post this here, as we rebuild a set of vintage 2843906 Cast Iron BB Heads.
It would seem warranted for comparison sake, given the costs of Parts & Labor rebuilding much of the old Cast Iron stuff these days, and the Performance "potential" when done.... versus, what can be easily purchased in the many aftermarket Aluminum offerings available today.

NOT saying what we do is right,  nor what anybody else does is wrong, just that..... this is the way we do it and we have had good success over the years.
I am also NOT going to get into costs of doing so, because that can also vary greatly according to prevalent Labor rates by geographical locations, "Regional Economics" I think it's called ?

Nonetheless,
I think it's fair to post Labor time incurred Hourly ? with the Machines/Operations performed for comparison sake where-ever if a fella undertakes the same endeavor ?
We will Flow the Heads as we get to various stages for Labor breakdown time-wise.
We will also be going directly to a Big Valve 2.14"/1.81" format for the rebuild, as an easy way to restore Valve Seat Height to factory parameters without installation of hardened Valve Seats, because, during our testing anyways when we Dyno/Break-in & Tune, has indicated no Seat recession with available lead substitute additives. Again here.... YOUR Machinist may prefer new Exhaust Seats, no right or wrong, just say'in we haven't seen the need as yet when we Dyno & Tune.

* Dis-assemble 2 Heads, Hot-Tank clean castings.
* Discard old parts complete.
* Glass Bead Heads, Mag Heads "No Evidence Found"
* Thread Chase all bolt holes... Good
* Install Bronze Wall Guide Liners, Broach to .371", Spot face Guide ends, done manually by Hand on Bench Top
2.5 Hours

* Setup Mill for Cutting/Enlarging Valve Seats for Big Valves (2.14" & 1.81"), Bridgeport Mill with acme Nuts deleted, rigid W/no backlash, Seats "formed" with Sunnen VGS20 Tooling... NO "Stones"
* Rough out V/Seats Intake & Exhaust 30*/45*/60*/75* Throat (No Trick Radius Cutters for easy repeatability anywhere)
* Switch Mill(ACME nut conversion) for CBN Surfacing, minimum cut @ .005", Heads Floor to Floor 2 times including above Seat work.
2.5 Hours

Ordered Ferrea Valves, 5000 Street Series 2.14" and 1.81"

Here is where we sit after 5 Hours Labor and now waiting Parts.
When the Valves arrive.... we will Hone the Guides to Size, Lap/Verify a base Seat contact, and do an initial Flow Test to see "where we are" before proceeding.
BTW,
NOT canvassing any work on here, too dam busy as is, these Heads are for a Customer's resto/numbers project and spoken for already.

[BSB67]

Thanks Bob.  Looking forward to updates.

I get the labor rate thing.  But, can you post the cost for purchased materials?

[Challenger340]

Thanks Bob.  Looking forward to updates.

I get the labor rate thing.  But, can you post the cost for purchased materials?

Yeah Russ, that's a great idea to keep a parts Price List, and I will make to sure to keep it updated which may be a real eye-opener to the investment.

Good suggestion.

[RCCDrew]

Subscribed!

[Challenger340]

Parts List:
$50.00    (2) BB Mopar Cast Iron Heads, Casting #2843906 from Core Stock(could be high or low depending on location)
$82.37     8 Ferrea 2.14" 5000 Series Street Intake Valves, Part #F5052-8 (our "cost" on account, no markup)
$80.06     8 Ferrea 1.81" 5000 Series Street Exhaust Valves, Part #F5053-8 (our "cost" on account, no markup)
$12.53     Freight
$16.00   (16) 3/8" Bronze Valve Guide Liners
_____________________________________________________________________
$240.96 Sub Total (Thus far)

[PRH]

Will the amount of porting done to these heads be based on a cfm target or a price point?

I can tell you this, what you did in that first 2.5hrs, would cost more than 2.5hrs labor in my shop.
Most of that stuff is sort of "flat rate" at my shop.

Actually, I guess I would say the same thing about the second 2.5hrs as well.

When you get all done, I'll try and figure a price on what I would have charged for the complete job.
Be interesting to see how close the price is to yours.

[70 sublime]

Parts List:
$50.00    (2) BB Mopar Cast Iron Heads, Casting #2843906 from Core Stock(could be high or low depending on location)
$82.37     8 Ferrea 2.14" 5000 Series Street Intake Valves, Part #F5052-8 (our "cost" on account, no markup)
$80.06     8 Ferrea 1.81" 5000 Series Street Exhaust Valves, Part #F5053-8 (our "cost" on account, no markup)
$12.53     Freight
$16.00   (16) 3/8" Bronze Valve Guide Liners
_____________________________________________________________________
$240.96 Sub Total (Thus far)

Since it says you are in Calgary for your location are these $$ amounts in Canadian money ?

[Challenger340]

Will the amount of porting done to these heads be based on a cfm target or a price point?

I can tell you this, what you did in that first 2.5hrs, would cost more than 2.5hrs labor in my shop.
Most of that stuff is sort of "flat rate" at my shop.

Actually, I guess I would say the same thing about the second 2.5hrs as well.

When you get all done, I'll try and figure a price on what I would have charged for the complete job.
Be interesting to see how close the price is to yours.

Given it's a comparison Iron Head Vrs entry level Aluminum's that can be had ? I thinking best to go to comparable CFM Flows.
I Flowed some OOTB Stealth's and Sidewinder's last week, both around the 265-270 @ .600", so right in that Ballpark.

I'm guessing it will take me a full 8 hour day porting with some short turn work involved ?  (Marty Bailed on doing Cast Iron)

We give estimates based on how long I think it will take ?
We just keep track of our time, and charge it against the Invoice ?  It's just always seemed the fairest way for us, and the Customer ?
If I run into something unexpected I get PAID for it.... and if it ends up being LESS work than I expected ? why should a Customer pay extra ?
That said,
I am NOT posting our Hourly rate, but we earn a decent living and keep the lights on with no shortage of work.

Lots of work to do yet, and don't think we are anywhere near done ! Not even close !
The Mill is very fast for cutting Seats, and then being able to Surface the Head on the same setup, but it's still just a start ?
We always go back and touch up the seats with Stones after Honing Guides before done, Lap & verify edge of Valve, Backcut, Cut for Seals, Wash Thoroughly, Measure/Set V/Spring Pressures, etc., you know the drill ?
I think people may be surprised with the Total hours at the end ?

[Challenger340]

Parts List:
$50.00    (2) BB Mopar Cast Iron Heads, Casting #2843906 from Core Stock(could be high or low depending on location)
$82.37     8 Ferrea 2.14" 5000 Series Street Intake Valves, Part #F5052-8 (our "cost" on account, no markup)
$80.06     8 Ferrea 1.81" 5000 Series Street Exhaust Valves, Part #F5053-8 (our "cost" on account, no markup)
$12.53     Freight
$16.00   (16) 3/8" Bronze Valve Guide Liners
_____________________________________________________________________
$240.96 Sub Total (Thus far)

Since it says you are in Calgary for your location are these $$ amounts in Canadian money ?

NOPE, I import all our Parts from the U.S., so U.S. DOLLARS !

[Challenger340]

.

[PRH]

Do you actually sell the parts for your cost?

8 Hrs, 260-ish+ cfm from 906's with 2.14 valves...... Seems about right.

I can't get to that number without some short turn work on a 906.

At my shop, complete ready to bolt on 260+ cfm big valve 906's would cost more than complete, prepped, blended, ready to bolt on 285cfm Sidewinders.

[Troy]

Do you actually sell the parts for your cost?

Hrs, 260-ish+ cfm from 906's with 2.14 valves...... Seems about right.

I can't get to that number without some short turn work on a 906.

At my shop, complete ready to bolt on 260+ cfm big valve 906's would cost more than complete, prepped, blended, ready to bolt on 285cfm Sidewinders.

I believe that's the point!

This thread was spawned from some other discussions about the real cost of rebuilding old heads vs just buying a snazzy new set of aluminum ones off the shelf (for the average guy I assume). This is where it started (I think):

Apologies for the hijack, but I have debated doing a set of 906's with big valves(2.14" /1.81") in my nogg'in for awhile now, if for no other reason than to show why NOT to do it anymore ? not to mention the expense in rebuilding them properly these days ?
You know... a "step by step" thing with photos, Flow as we go, up to a Bowl Port & Gasket match level.
We would stop at that point, as very obviously the expense going further would far exceed just buying any of the entry level aluminum head options on the market, nonetheless, we could drag some very old and much higher developed iron castings out for comparison up to the 300 cfm level.

Should it be posted here on this thread ? or start a new thread ?
What say you all ?

Bob @ rmp
PS: problem being, WTF are we going to do with a set of 906's these days ? It seems the parts/valves etc. may be worth more than the Heads when done ?

There's a lot more after that initial post.

Troy

[BSB67]

I'm very glad to see Bob willing to do all this for our benefit.  So I do feel a little sheepish asking for more, but I still will.   I know Bob will put me in my place if I go too far, so here goes:

1) Will you post the flow of both the Sidewinder/Stealth and ultimately the 906's at 0.10" lift increments? The often forgotten 0.10" through .050" flow numbers should matter more to many on this forum.

2) In the end, can you break it down to two 906 head levels - one as a set of "good" heads (i.e. parts and labor short of porting) and then the ported 260 ish head? 

3) Flow both the 'good" head, and the ported head.

Thanks

[Challenger340]

Do you actually sell the parts for your cost?

Hrs, 260-ish+ cfm from 906's with 2.14 valves...... Seems about right.

I can't get to that number without some short turn work on a 906.

At my shop, complete ready to bolt on 260+ cfm big valve 906's would cost more than complete, prepped, blended, ready to bolt on 285cfm Sidewinders.

I NEVER sell part's for cost, because I need to be paid for my time and expertise to bring in the RIGHT parts ? and the accounting in maintenance of direct accounts for access.
Otherwise customer's can supply their own parts, which, if any of them are wrong, hold me up, or I am just plain NOT comfortable with ? Then once again back to the I get paid HOURLY ?

I only Posted our "cost" on the parts for this project, so people can SEE that even with as cheap as it gets parts pricing.... what the true imputs are for Shops are to do a proper rebuild on Iron Heads, before they make nickel one to keep the lights on ?

From what I remember, the high floor 915/906 will do fine until a point, then not just "stall", but maybe even DROP as it goes sonic at higher Lifts over the short turn ? hence for 260'ish I guess I'll have to lay it back a bit = TIME !!

I'm just going to keep track of my Hours, Charge accordingly, but I can't remember the last time I personally touched or Ported a set of BB Mopar Iron Heads ? 10 ? 15 years ?

LOL ! I'm guessing the Done & Finished Sidewinder's for the money will end up looking like a smok'in deal compared to when I am done with these Iron's !

[Challenger340]

I'm very glad to see Bob willing to do all this for our benefit.  So I do feel a little sheepish asking for more, but I still will.   I know Bob will put me in my place if I go too far, so here goes:

1) Will you post the flow of both the Sidewinder/Stealth and ultimately the 906's at 0.10" lift increments? The often forgotten 0.10" through .050" flow numbers should matter more to many on this forum.

2) In the end, can you break it down to two 906 head levels - one as a set of "good" heads (i.e. parts and labor short of porting) and then the ported 260 ish head? 

3) Flow both the 'good" head, and the ported head.

Thanks

Yeah I'll try Russ, gimme a kick on here if I miss any of what you are after OK ?
Time is getting limited heading into January, a couple of big projects coming up.... probably very little time to play with 46 year old metal bin salvages nobody cares about anymore, except for one resto Guy who wants these and that's the only reason they are being done.

[PRH]

I only Posted our "cost" on the parts for this project, so people can SEE that even with as cheap as it gets parts pricing.... what the true imputs are for Shops are to do a proper rebuild on Iron Heads, before they make nickel one to keep the lights on ?

I hadn't looked at it that way, but I see what you're trying to show.

I would have just used the resale prices, since that's what the customer will end up paying.

This thread was spawned from some other discussions about the real cost of rebuilding old heads vs just buying a snazzy new set of aluminum ones off the shelf (for the average guy I assume).

Trust me, I understand the logic behind this thread.
I have had this same conversation with people calling to have some stock heads done up, thinking it's going to cost way less than buying new heads. They're usually shocked when I tell them it'll cost less to just buy new heads.

I just ran some numbers quick.....
Using the same Ferrea 5000 series valves, Comp Cams springs, retainers, locks, spring cups, Viton seals, shims......
And doing the same type of job Bob is doing here, only I included installing hardened ex seats......
It all adds up to about $75 less than I would sell a set of ready to bolt on Sidewinders for, that flowed 285+cfm.

Oh....... And that's before any porting or blending is done on the stock heads....... And using your supplied cores.

[cdr]

last set of 906 I did was in 1992, they were for a 440 Dragster, if I remember correct they flowed 260ish, they also cracked later on & created a BAD mess for the 440 block.

[BSB67]

I only Posted our "cost" on the parts for this project, so people can SEE that even with as cheap as it gets parts pricing.... what the true imputs are for Shops are to do a proper rebuild on Iron Heads, before they make nickel one to keep the lights on ?

I hadn't looked at it that way, but I see what you're trying to show.

I would have just used the resale prices, since that's what the customer will end up paying.

This thread was spawned from some other discussions about the real cost of rebuilding old heads vs just buying a snazzy new set of aluminum ones off the shelf (for the average guy I assume).

Trust me, I understand the logic behind this thread.
I have had this same conversation with people calling to have some stock heads done up, thinking it's going to cost way less than buying new heads. They're usually shocked when I tell them it'll cost less to just buy new heads.

I just ran some numbers quick.....
Using the same Ferrea 5000 series valves, Comp Cams springs, retainers, locks, spring cups, Viton seals, shims......
And doing the same type of job Bob is doing here, only I included installing hardened ex seats......
It all adds up to about $75 less than I would sell a set of ready to bolt on Sidewinders for, that flowed 285+cfm.

Oh....... And that's before any porting or blending is done on the stock heads....... And using your supplied cores.

And this is actually why, in part,  I asked Bob for item #2 in my post above, i.e. the amount of work and parts cost for a preparing "good" heads with out port work.  It is common for guys on this and other forums that are looking for more power, or building a motor, stating that they are starting with a good set of  XXXXXX factory heads.  My though is always "Really?" Either someone took a bath on those heads, or for the $500 spent (as an example), you don't have good heads.  Is it possible, sure.  Just unlikely.

[PRH]

I have had many reconditioned OE heads come through my shop, often times before they have even been run on a motor.
They came with a motor or other parts someone buys, or the plans get changed before the motor gets assembled, or the owner starts questioning whether the place they had do them did them correctly for a performance build.

The overall fit, finish, and performance potential(flow) is often not really that good, yet they have had "everything" done, and have all new parts........ and they didn't usually get that way with a bargain basement price either.

Unfortunately, I don't think cost is a very good gauge for how "good" a particular set of rebuilt stock heads are.

While the chances of coming across a set of unmolested OE cores that don't need "everything" is getting slimmer by the day....... If one did happen to have a really nice set of 346/902/452 castings, and was looking to do something on a "budget".......   You could have fairly good performing heads(250-260cfm) for relatively cheap money(under $1000).
Like I said, those type of cores don't show up often....... But I leave the possibility of that happening open.

For the most part, I think Stealth heads for $1000 with the absolute minimum of tweaking are going to give most people the "most for the least".

And this is actually why, in part,  I asked Bob for item #2 in my post above, i.e. the amount of work and parts cost for a preparing "good" heads with out port work.

In my shop, to do the type of job Bob is doing here, including the parts but without any porting, would be several hundred $$$ more than buying assembled Stealth heads.

[Challenger340]

The Valves must have showed up late last night, as I saw them sitting in the inbox this morning ?
Had a couple Hrs to my self today, so Honed the Guides, Washed & Dried them, Lapped a few seats just for a reference, (remember here, I redo/touch up with Stones as Final, so more time later), but I was able to then Flow the Heads for a baseline with only the initial work done as in the photos above, NO Porting yet.
Again, no time is being charged for Flowing, as it's just a side project for here.

1.5 Hours  Mic Valves, Hone Guides for Clrc @ .0014" Intake and .0016" Exhaust, Lap Seat O.D. Contact @ 2.100" & 1.79", Wash Heads & Dry

Hey Russ.... I think this is the numbers you were looking in your question above ?  As if a Customer had just got the Heads "rebuilt" with Big Valves, no porting ?

28" H2O Test Pressure. Clay Inlet, No Pipe
                         CFM
Lift            Intake          Exhaust
.050"         37.1                30.1
.100"         66.0                54.1
.150"       100.2                80.5
.200"       136.6               100.6
.250"       171.5               123.0
.300"       196.3               137.5
.350"       217.6               149.6
.400"       232.0               157.0
.450"       237.5               162.1
.500"       240.9               165.8
.550"       240.7               168.7

I think the depth of the 75* Throat Cut helped immensely, it extends ~.375" up into the port past the 60*.

Seat Angles used:
30* @ .045" wide
45* @ .039" wide
60* @ .090" wide
75* @ ~ .375" up into port.              

[Challenger340]

OK, so now time to do some Porting ?

* Blend the 75* Cutter ridge in the Intake Bowls all the way up beside the Guide
* Blend the Intake short turn very mildly to make it "round" same as the 75* cut.
* Cleanup the Intake port entrance, enlarge the pushrod Pinch from .990" before to 1.050" now, but stock port window UN-enlarged.
* Shape & Cleanup The Exhaust ports, stock window UN-enlarged

45 Minutes to do 1 Intake Port & 1 Exhaust Port


The NEW Flow after the work is below in Bold for comparison.
28" H2O Test Pressure. Clay Inlet, No Pipe
                         CFM
Lift            Intake                      Exhaust
.050"         37.1  36.9            30.1   30.5
.100"         66.0  67.7            54.1   54.8
.150"       100.2 101.8            80.5   82.5
.200"       136.6 138.7           100.6 102.4
.250"       171.5 172.9           123.0 127.0
.300"       196.3 201.1           137.5 144.8
.350"       217.6 227.5           149.6 158.7
.400"       232.0 248.2           157.0 169.6
.450"       237.5 258.8           162.1 179.4
.500"       240.9 251.2           165.8 186.9
.550"       240.7 252.5           168.7 192.7

Intake was doing fine until .450" Lift, after which, you could audibly "hear" the airflow separating over the too High short turn ?

I will have to go back in and fix that Intake Port Short turn.

Couple of Pics of what was done, nothing fancy nor pretty.

[Challenger340]

I went back in and rolled the Intake Short turn back a bit, just enough to make a very nice .500" Lift Head.  Left the Exhaust "as is" for now.

#1  Intake Port Original w/Big Valves Machine Cut
#2  Intake Port with 45 Minutes Porting time.(Int & Exh)
#3  Intake Port after another 15 Minutes fixing the Short turn.

Lift            #1     #2       #3                    
.050"         37.1  36.9      37.3        
.100"         66.0  67.7      67.0          
.150"       100.2 101.8    100.5        
.200"       136.6 138.7    138.9      
.250"       171.5 172.9    172.8          
.300"       196.3 201.1    201.8          
.350"       217.6 227.5    228.7          
.400"       232.0 248.2    254.0          
.450"       237.5 258.8    268.7          
.500"       240.9 251.2    275.3        
.550"       240.7 252.5    269.4

Before I go any further, here is a Flow comparison of:

Lift            OOTB Stealth      Stealth W/10 Hrs Porting      OOTB Sidewinder         Our test "906" Iron (assuming 10 Hrs Porting)
             Int           Exh             Int              Exh             Int             Exh             Int          Exh
.100"      64.1         56.4            72.8            63.2            69.7           57.7            67.0        54.8
.200"     131.9       107.3          144.1           122.5          146.0          107.0          138.9      102.4
.300"     196.0       145.4          205.9           159.3          209.8          143.7          201.8      144.8
.400"     235.7       170.2          258.1           186.5          244.8          166.9          254.0      169.6
.500"     253.7       183.2          285.1           204.7          260.6          177.3          275.3      186.9
.600"     265.4       192.0          295.5           216.7          270.0          183.0          272.1**   197.5**   (.600" Flowed after on 906 Iron for comparison)

All done with Clay Inlet Radius, No Pipe Exhaust.
     

[Challenger340]

Now just for fun..... dug out an old 915 Iron, one Intake Port Hogged Out 80's style, 2.14" Valve

28" H2O, Clay Inlet, No Pipe
             Int              
.100"      79.4
.200"     141.9
.300"     208.2
.400"     252.1
.500"     283.2
.600"     298.5
.700"     302.1

[cdr]

very nice Bob !!!   

[BSB67]

Excellent Bob.  Thank you very much!.

Will the low lift numbers get better when you put the finished valve/seat grind in? What do you use for finished seat widths?

[PRH]

I tightened up the columns as it was all jumbled up on my small screen on the phone.

A- OOTB Stealth    
B- Stealth W/10 Hrs Porting      
C- OOTB Sidewinder        
D- Our test "906" Iron (assuming 10 Hrs Porting)

--------------A----------------B---------------C----------------D
            Int     Exh       Int    Exh        Int      Exh      Int     Exh
.100"      64.1 /56.4      72.8 /63.2      69.7/ 57.7      67.0/ 54.8
.200"     131.9/107.3   144.1/122.5   146.0/107.0   138.9/102.4
.300"     196.0/145.4   205.9/159.3   209.8/143.7   201.8/144.8
.400"     235.7/170.2   258.1/186.5   244.8/166.9   254.0/169.6
.500"     253.7/183.2   285.1/204.7   260.6/177.3   275.3/186.9
.600"     265.4/192.0   295.5/216.7   270.0/183.0   272.1/197.5**
 
**(.600" Flowed after on 906 Iron for comparison)

-----------------------------------------------------------------

IMO, the 906 high lift flow you have there is quite good for that amount of time invested.
If I did a 10hr porting job on 906/915 heads, I doubt I'd be at 275cfm.

[Challenger340]

Excellent Bob.  Thank you very much!.

Will the low lift numbers get better when you put the finished valve/seat grind in? What do you use for finished seat widths?

We'll see when done I guess ? I will Flow at the end when done with Pics of Final Seats & widths
That said,
I am not applying any targeted fatter low-mid Lift seat preps here(custom Radius cutters, etc), those are proprietary.... I am using just the std 30/45/60/75 valve seat angles that would be commonly found and easily repeatable in the marketplace at any Shop.

What I think is getting interesting ?
Is if a fella starts "estimating" where he will end up for pricing by the time these things are Done ?

I mean let's face it here ? IMO, People should be starting to see by now, that these old Irons in Parts & Labor are going to cost as much, or more ?? for LESS performance potential....
versus,
than what can be purchased in an Aluminum Head and then spending wisely to have prepped properly ?






   

[cdr]

looking forward to see the low lift flow after back cut.

[Challenger340]

I tightened up the columns as it was all jumbled up on my small screen on the phone.

A- OOTB Stealth    
B- Stealth W/10 Hrs Porting      
C- OOTB Sidewinder        
D- Our test "906" Iron (assuming 10 Hrs Porting)

--------------A----------------B---------------C----------------D
            Int     Exh       Int    Exh        Int      Exh      Int     Exh
.100"      64.1 /56.4      72.8 /63.2      69.7/ 57.7      67.0/ 54.8
.200"     131.9/107.3   144.1/122.5   146.0/107.0   138.9/102.4
.300"     196.0/145.4   205.9/159.3   209.8/143.7   201.8/144.8
.400"     235.7/170.2   258.1/186.5   244.8/166.9   254.0/169.6
.500"     253.7/183.2   285.1/204.7   260.6/177.3   275.3/186.9
.600"     265.4/192.0   295.5/216.7   270.0/183.0   272.1/197.5**
 
**(.600" Flowed after on 906 Iron for comparison)

-----------------------------------------------------------------

IMO, the 906 high lift flow you have there is quite good for that amount of time invested.
If I did a 10hr porting job on 906/915 heads, I doubt I'd be at 275cfm.

Yeah, I was a little perplexed at that "275" as well ? So I went back and re-did it.... same same ?
I kind of expected mid 260's @ .500" and maybe touching "270" by .550" which IMO would be pretty darn good 906's for me and what's in them ?

Dunno what's up with that, we'll have to see if it stays or is still close in other ports tested when done. Before going any further I'll do a re-cal / FlowCom leakage again etc., just didn't want to stop as in a hurry yesterday and time is limited anyways on this project ?  Long story short I may have a "Blooper" there.  
Stay tuned and we'll revisit a few Lifts to Final against that "275".

[Challenger340]

looking forward to see the low lift flow after back cut.

Lots of work left touching/adjusting the V/Seats with Stones... lapp contacts, before I get to a Final and can Back-cut the Valves.

Gotta stop and go back, do a re-Cal/FlowCom/leakage etc. again, and re-Flow before proceeding, I was suspicious of that "275" number @ .500" for what's there ? but had limited time.
Maybe get a velocity probe and see what's going on between .500" and .550" if it stays after retest.

[PRH]

I'd probably leave it for the time being if it were me, and see if that number (or something really close to it) shows up on another cylinder, before I questioned the test equipment.

I was testing an Indy CNC 345 the other day, and the .200-.300 numbers looked a little better than normal.
I stopped right there and tested for a leak...... But didn't find one.

This particular set of heads had a slightly smaller bowl ID as rec'd from Indy, and that gave me a little more room to get the valve seats and approach angles the way I like them..... And that's why the heads were better than "usual".

Frankly, when I test a head that flows particularly good....  Or bad....... it's very rarely(as in almost never) the equipment.

[cdr]

Nice Flow bench set up you have now Bob, I am out of the porting businesses, but I still have my toy bench that I have had since 1990, I mess with my own stuff some.

[PRH]

I also had a SF-110 I bought new in 1992. Used it a ton, and finally got something bigger (Saenz S-600) in 2007.

I learned a lot using that little bench.

[cdr]

I am really enjoying what Bob is doing here.

[chargerbr549]

Very interesting, lots of good information!

[Challenger340]

Nice Flow bench set up you have now Bob, I am out of the porting businesses, but I still have my toy bench that I have had since 1990, I mess with my own stuff some.

IMO, the SF110's are great machines Charlie, lots of Shops still using them, they work extremely well and provides lots of useful information 
We only went new and larger as tired of fixing, and for the sensitivity to small changes on larger heads, just easier to see.

[Challenger340]

I'd probably leave it for the time being if it were me, and see if that number (or something really close to it) shows up on another cylinder, before I questioned the test equipment.

I was testing an Indy CNC 345 the other day, and the .200-.300 numbers looked a little better than normal.
I stopped right there and tested for a leak...... But didn't find one.

This particular set of heads had a slightly smaller bowl ID as rec'd from Indy, and that gave me a little more room to get the valve seats and approach angles the way I like them..... And that's why the heads were better than "usual".

Frankly, when I test a head that flows particularly good....  Or bad....... it's very rarely(as in almost never) the equipment.

As time permits,(Cast Iron feels like an after school detention project), I'm just going to do all 8 ports and test a few more to see the consistency.

After giving it some some thought ?

I think it's more a "volume" problem above the Valve with the FAT guide intact, and it hits a "sweet spot"(275) before going unhappy.
Needs some added roof Volume/"Time" for it the air to turn.  I might have to narrow the guide a bit.
Back in the day we always did guide shaping as a std prep... just never thought it would have that much impact on these Heads ?

[tan top]

 interesting info guys , thanks for sharing 

[PRH]

Bob,
The only 906's I've ever tested that flowed good at high lifts, and still retained most of the short turn height were ones CNC ported by Jeff at Modern.
He did have the guide boss mostly gone, and the bowl was pretty big as well.
I was never able to get that to work for me, even after seeing how his were shaped.

Even with the bowl at the same diameter, and the guide boss removed, I've always had to really knock down and lay back the short turn to not have the numbers back up(too bad) above around .550 lift.

The best 906 I've had on my bench were some of the "312cfm" CNC ported ones that MM was selling a few years ago.
I'm pretty sure they were done by Modern, and they looked the same as the ones I knew had come from there.
The MM ones had 2.19" 11/32 stem intake valves in them, and after polishing the CNC lines out of them flowed 297cfm.

[Challenger340]

Thanks for the info Duane, much appreciated 

From what I remember about the old high floor 915/906's, just as you describe, they hit a wall without rolling the short back, and then it becomes a "timing" thing to the floor where all of a sudden Flow dramatically increases at the higher lifts ?
But it's alot of work getting in there to get those short turns right, and difficult, so I was hoping just to "keep it simple stupid" narrowing the guide boss a bit and see what happens ?
I can't remember what more volume in the bowl does without also rolling the short back more than the minimal I've done ? could be the "275" blooper I saw just before it goes sonic ?

These 906 Heads being (hopefully) still a decent pair for a resto deal, I didn't want to get too carried away, no point having gunga Flow @ .500"+ for a short Cam ?
But what the heck....
it's a 10 Hr Porting project, so I'll see where I'm at time-wise, and see where it goes on the short-turns. I can always shelve these for posterity and do the guy another set, LOL !

I won't have any time until next weekend, gotta keep the lights on because these 906's sure won't !

[PRH]

My "path"  to get 906's into the 260-ish range is to blend the machined areas of the bowls into the cast areas, slightly bullet nose the guide boss, and roll the sort turn back, along with opening the pinch about like what you did.
For this amount of flow I don't do any trimming to try and reduce the bulk of the guide boss itself.
Without a ton of work in the bowl or pinch area, I've found the best bang for your porting buck(time) is spent properly contouring the short turn.
I don't start reducing the mass of the guide boss until I start looking for flows in the 270+ range.
For me at least, it's a pretty big jump in the amount of time invested to get a 906 port to go from say 260-265, up to 275+.

The 346/902/452 have almost no guide boss to begin with, so very little time needs to be spent there even for pretty high effort heads, and they also have basically no short turn, so again..... It just takes less time to rework those areas of the port.

[500Jon]

Just love the '906' porting work Guys!

I ran a 440 '906' motor some twenty years ago that made approx. 600hp.
The heavily ported 'Rob Loring ICE-UK' heads were the best I've ever seen.
1/2'' raised ports with channelled port floors to make the intakes the normal '906' size again.
5/8'' ali spacers screwed onto the intake faces to allow normal intake fitment.

Sorry no pics as I sold the motor about 15 years back, she was a beaut, REAL OLD SKOOL...

I'm going to get someone to Flow-test my UK-Weslake Ovalport/D-port 1969 iron-heads soon for a '906' comparison.
Open chamber design with Motorhome extra water passages, 2.250 intake and 1.800 exhausts.
Also has 'taper-seat' plugs as per MH too, thought those mods weren't introduced till the mid 70's?
Extra-thick deck around the exterior bolt holes for better strength.

[500Jon]

Found a blurred pictures of the ICE port!

[PRH]

Wow!!
Those oval port bb heads are pretty cool!!

On the 906's, with that material added to the floor and the roof raised, you get a much better approach to the short turn.
I bet those worked pretty well.

[500Jon]

They made approx 600hp and ran a 440 dart into the nines without NOS! (ex Sixpack 69 1/2 engine)
The ports were raised so high they broke out at the top, just visible in the lower picture.

Its good to see Folks still spending time and effort on 50 year old iron heads!

The 440 engine and its derivatives have fueled UK drag racing for most of our lives!
Only a handful of 426 iron hemi's have ever been run in the street classes due to costs.
Without the humble iron-headed 440, European drag racing for Mopars probably wouldn't exist!

Aluminum plate added to intake flange, with a Team 'G' highly ported Domi manifold.
Runners were welded and rasied to improve flow too, this is how it was in the 80's-90's.
MAKE DO AND MEND!

[500Jon]

I just remembered, this wonderful 440 engine was removed from a 69 1/2 Sixpack Superbee in the 80's!

Fortunately someone realised and the engine was re-united with her again about ten years back.
When the engine was rebuilt with another block, IT BROKE into many pieces!!!

SP Superbee is now in France...with her original NINE second Rob Loring 'ICE' engine lol...

God moves in mysterious ways...

[PRH]

I'm in the final stages of getting a set of OE heads done for a customer.
For what he's doing with the car, aftermarket heads aren't an option....... So reworked OE it is.

I'm not going to get into specifics on what each thing costs, but for these heads.......complete and ready to bolt on....... Steel retainers and budget friendly roller springs, Ferrea 1.81/2.14 valves, ported to flow 278/211 @ .600, 281/215 @ .700, milled to 78cc and the intake side corrected accordingly ......... They cost just about the same as two sets of ootb RPM heads(at the current Summit price).
In the porting, flow testing, and general deburring and clearancing for pushrods(1.6 rockers), there's about 20hrs of labor in just that part of it(which is just about the cost of one set of RPM heads).

Just figured I'd give this post a little bump.

[BSB67]

What would you think the crack potential is?

[c00nhunterjoe]

What was the flow at .450 and .500???

[Challenger340]

Yeah I gotta get back on those 906's as soon as time permits, awefully sorry 'bout that fellas, just so damn busy right now.  The guy who's getting the 906's ain't in a hurry, so other priorities for Spring right now.

[tan top]

 

[PRH]

What would you think the crack potential is?

They aren't "maxed out", but a lot of metal comes out of the valve seat area when you install the bigger valves and do some bowl cutting.
The two most common areas I see for cracking is externally under the 2 center exhaust ports, and across the intake seats from the chamber down into the bowls.

The more power you make........  The more likely they seem to crack.
The chambers "oil can" and fail where they're thin.
I think the area under the exhaust ports gets brittle from localized thermal cycling, and when your making power, the head is trying to be "lifted off" the block, and sort of pulls the head open in that area.
Ive seen heads that had 2-3" cracks in that area that didnt leak at all until the motor was under power.

So, the porting and larger valves definitely reduce the reliability of the head(IMO), and the heads being milled .050 takes some overall rigidity away from the casting, although I'm not sure if that has a big impact on the cracking under the exhaust.
I haven't done anything to this set of heads that should make them more crack prone than other sets that flow similarly....... And some of those have cracked, while others have lasted years and years.
For the most part, I feel it's just a crap shoot whether they crack or not(unless you have tune-up or cooling system issues).

The way I see it is, if "high reliability" is pretty far up the priority list....... Leave them at std valve size, don't port them all that much, and keep the milling to something reasonable.
Std valve size heads with mild porting(260-270cfm), and 84cc's or so with aftermarket valves would be my suggestion for keeping the reliability(reasonably) high.

I guess we'll just see how these hold up.


Flow at lower lifts:
Lift------I/E
.300---210.7/152.2
.400---244.6/187.8
.450---255.4/199.6
.500---268.5/203.7
.550---275.6/208.3

[aerolith]

 

[C500]

I just remembered, this wonderful 440 engine was removed from a 69 1/2 Sixpack Superbee in the 80's!

Fortunately someone realised and the engine was re-united with her again about ten years back.
When the engine was rebuilt with another block, IT BROKE into many pieces!!!

SP Superbee is now in France...with her original NINE second Rob Loring 'ICE' engine lol...

Aerolite / aerolith... aka 500jon???

[aerolith]

Hi C500,

Yep one and the same!
My computer died and I had password probs so I re-stated again as 'Aerolith'.

As I am a Dodge Dionsaur I needed to match my neolithic heritage, so I found an archaic name for myself,  Aerolith or Aerolite depending on the dictionary used lol...

Meteorite is more modern talk, which I think is apt for my Aero, crusty but very quick!

[aerolith]

Good points there PRH!

I have a good collection of BB iron heads, some ported in the UK and some from the US of A.
I would say the ICE heads were easily the most unique but a set of 452 Koffels I had were pretty trick too!
Yep the flatter ports of the post 906 era heads are easier do, but I ave some 915's that will deffo go into the 300's.
They are 'old-skool' hogged out to the max and have the closed chamber of desirability.
The Koffels were machined to the max and when you picked them up, they felt uncannily light!
Probably machined over 100thou off the mating face and a small quench recess re-machined back in to give 'zero deck pistons' some room to play.
Then I found another pair of luvly 906's on my infamous drag-Charger 'LFN 7', the tops of the runners were welded up just before the valve guide.
Then they were ported to the max not unlike the hogged 915's but much higher around the guide boss.

Now they are all just 'talking points' in the era of Cheapo Chinese aluminum heads.
You can't stop progress, but you don't have to destroy the past, to make way for it...

Aerolith