Compression test results - Where to go now?

[toupee]

Hi all,

Some of you may have seen my recent thread about the noise I heard coming from what I thought was the passenger side of my motor.  Well, I decided to go ahead and do a compression test since I thought maybe it would reveal something about that problem.  In case it matters to anyone I let each cylinder go through 6 compression strokes before I took my readings.  Here are the results I got when doing the test:
#1 - 130 psi
#2 - 120
#3 - 30
#4 - 125
#5 - 135
#6 - 130
#7 - 133
#8 - 125

No, that's not a typo.  #3 had 30 psi on the first test.  I thought something had to be wrong so i rethreaded the tester in and got 40 psi the second time. 
After trying it a total of three times I was convinced I wasn't goofing anything up.. the cylinder is just messed up.  I tried a wet test and got 50 psi. 
I started listening more intently when turning it over and I've noticed that there is a sound like compressed air being relieved when the going through the compression stroke.  Guessing that means I have problem with at least my exhaust valve. 
Anyways, so, I'm looking for suggestions on what I should do now.  I suppose I'll have to pull the head? 

[firefighter3931]

Yep, the head needs to come off....bent/sticking valvestem or burnt valve seats are the likely culprit(s) 



Ron

[toupee]

So, I'm wondering since I'm gonna have to pull the head off anyways if this wouldn't be a good time to just take the other head off as well and have them gone through since I don't even know if they have hardened valve seats on them.  Is there a way to tell just by looking at the head if the seats are hardened?   The valves should be stainless if they are, right? 
Maybe my thinking is wrong, but since I'm not totally sure what the build of the motor is ( I was told it was just rebuilt but I am not real inclined to believe that anymore after finding this ) I could take this opportunity to replace some parts and at least be sure of the bore and top end components.
Is my thinking logical here or am I just going to get myself into more work than I need to?

[craigandlynda]

pull both heads.you already are unhooking the top end and buying gaskets...this is the time...

[oldschool]

pull both heads.you already are unhooking the top end and buying gaskets...this is the time...

[toupee]

I have decided that I will definitely be taking off both heads. 
Say, hypothetically, that since I'll have the top half of the motor disassembled anyways I decide I want to start from scratch on the heads, intake, cam, rockers, carb, etc so that I know exactly what is in the engine (no bottom end work if not necessary).  I'd love to hear some suggestions on what I could go with that would make an awesome street machine that retains my p/s, p/b, a/c. 

[1969chargerrtse]

So, I'm wondering since I'm gonna have to pull the head off anyways if this wouldn't be a good time to just take the other head off as well and have them gone through since I don't even know if they have hardened valve seats on them.  Is there a way to tell just by looking at the head if the seats are hardened?   The valves should be stainless if they are, right? 
Maybe my thinking is wrong, but since I'm not totally sure what the build of the motor is ( I was told it was just rebuilt but I am not real inclined to believe that anymore after finding this ) I could take this opportunity to replace some parts and at least be sure of the bore and top end components.
Is my thinking logical here or am I just going to get myself into more work than I need to?

I'll probably get beat up for saying this but I have had  at least 25+ big block muscle cars 1970  LS6 454/450hp, 1970 440/6, 1969 396/375hp 1969 302/275hp  etc...and never had the seats done.  I ran all types of gas and never had an issue.  I'm just not a believer in the harden seats/ unleaded gas logic but thats just my experience.    I'd certainly pull both heads at least, better to be the top end than bottom end. 

[craigandlynda]

i have to agree with chargerrtse, i have built and raced and ran the poop out of NUMEROUS  440's, and never worried about the lack of lead...in fact, we used to use Amoco clear unleaded on many occasions to race with...back in the days of hi octane gasoline at the pumps, we switched between sunoco 260, a high- lead gasoline, and amoco clear, another hi octane gas, and both ran great and never saw any seat damage.i bought a new 67 GTX, and ran it over 40,000 miles in the first year, and another 40,000 before trading it, completely on amoco clear premium.... i know it's an accepted theory, but to me it's still theory til i see it for myself on my own engine...

[toupee]

In 67' I was still 14 years from even being born 

[Steve P.]

We will need more info on your motor/tranny/gear/want from the car, to better be able to help you.

Yes, pull both heads. Let us know what heads you have and what you find. Then we can better help.

Lean conditions tend to take out seats and valves. I was of the opinion that hardened seats were not a big deal till I cooked one.... A crack in the seat sucks....   

[rt green]

hell've a good time to cook up a hot street recipe

[craigandlynda]

my guess , without being there, is that the head and seat are ok, but the exhaust valve has a burnt area along the edge, maybe even missing some metal...bet the three angles are rounded over...

[craigandlynda]

In 67' I was still 14 years from even being born 

i think i would be speaking for many of us 50-somethings, in saying that we were extremely fortunate to be teenagers in the days of cheap horsepower, cheap gas, and drive-in restaurants with 15 cent burgers...but mostly being able to enjoy the hi-po mopars when new and in the showrooms....my first car was a NEW 1966 barracuda...which i beat badly and traded in a year later for a new GTX...

i'm just glad for you young-uns that see the magic and majesty of mother MoPar, and are willing to preserve and perpetuate these wonderful and spirited cars- "our fathers magic carpets made of steel."

[oldschool]

In 67' I was still 14 years from even being born 

i think i would be speaking for many of us 50-somethings, in saying that we were extremely fortunate to be teenagers in the days of cheap horsepower, cheap gas, and drive-in restaurants with 15 cent burgers...but mostly being able to enjoy the hi-po mopars when new and in the showrooms....my first car was a NEW 1966 barracuda...which i beat badly and traded in a year later for a new GTX...

i'm just glad for you young-uns that see the magic and majesty of mother MoPar, and are willing to preserve and perpetuate these wonderful and spirited cars- "our fathers magic carpets made of steel."

craig,very well said!!!!

[toupee]

Thanks for the replies guys! 

Cars are in my blood - my grandpa was a mechanic and my uncle bleeds Hemi orange.  Unfortunately my dad doesn't know gasoline from engine oil so I've pretty much had to learn the little i know by myself 

Anyways, what I know so far about my car -

71 satellite - sorry not a charger    Is trying to be a roadrunner 

68' 383 block. 
727 with a cheetah auto/manual valve body I put in.
8 3/4" rear end.  I believe it has 3.23 gears as near as I can tell from watching the driveshaft rotate while I spin the tires. 
275/60 15 rear tires (biggest I could fit  )
Has to have a factory stall because it is low.
906 heads
Hydraulic cam and lifters - don't know specs.  Was told the engine was built to HP spec... but I was also told it was just rebuilt and I doubt that now!
Should be standard crank/stroke according to what I was told
Hedman street headers - 1 3/4 primaries
Eddy DP4B intake
I currently have two carbs sitting around - a 600 Eddy performer and a 670 Holley street avenger. 
Power steering
A/C
Nice aluminum radiator

As far as what I would want to do with it... well, I don't race.  I would just want build it for as much reliable power that i could make on the street while keeping all the accessories working.  Basically just going for a value/coolness factor.  I know myself and I would bet that i will sell the car at some point, but I want it to be done well so that whoever I sell it to can know they are getting something quality and not get bit in the rear like I kinda did lol

On a side note, my column has a cruise control setup... is there any way that was factory?

[toupee]

Hey all!
I got the head off today and thought I would post my pictures here so that maybe someone can let me know if they see anything wrong!

[craig]

hmmmmmmmm...what did the gasket look like between that # 3 and #5 cylinder?

[firefighter3931]

Hey all!
I got the head off today and thought I would post my pictures here so that maybe someone can let me know if they see anything wrong!

The heads look fine on the chamber side....no sunk valves. 

That doesn't rule out a bent or sticking valve....or a bad head gasket.

Check the heads for warpage as well.


Ron

[Challenger340]

Dunno, looks like time to pull the valves outa the heads.

#3 does look like the fuel was washing the chamber "slightly" by the plug area, but that would be normal poor cold firing @ 30-50 psi.

I'm another non-believer in the need for hardened seats / Valves.

If you're worried about it, just add a few ounces "top end Oil" to a tank of gas,
That,
and keep it tuned properly so the Valve seats don't "weld" themselves to the Valves which causes the recession.

[Rolling_Thunder]

hmmmmm      well it doesnt look like there is anything obvious wrong with the heads...     My experience with getting heads redone is this...    if you take them to a machine shop and have the heads completely redone including stainless valves, locks, keepers, springs, magging, milling, and mild porting...       with the new heads from 440 Source it is almost cheaper in most instances - plus you get added compression and a more efficient head for the $$$... 

[toupee]

hmmmmmmmm...what did the gasket look like between that # 3 and #5 cylinder?

As near as I can tell the gasket is ok.  It just looks like it's been pressed from tightening the heads down but I don't see any damage to it.

That doesn't rule out a bent or sticking valve....or a bad head gasket.

Check the heads for warpage as well.


Ron

How do you check for warpage on the heads?  The surface looks fairly smooth to me but I guess just by eye I might be missing something.

Another thing.  Are the flat top pistons that are in there like the oem ones?  There seems to be carbon build up about a 1/4" from the top down in each cylinder.  I'm guessing that means the pistons don't go to deck height.

[firefighter3931]

How do you check for warpage on the heads?  The surface looks fairly smooth to me but I guess just by eye I might be missing something.

Lay a straightedge across the heads and also across the deck of the block....it should sit flush with no airgaps visible. You can use a drop light to help see things better 

Another thing. Are the flat top pistons that are in there like the oem ones? There seems to be carbon build up about a 1/4" from the top down in each cylinder. I'm guessing that means the pistons don't go to deck height.

That buildup is normal....the top ring will never be even with the deck surface because there is too much heat up there. Try and get the piston to TDC and measure the piston to deck clearance. This will help us to calculate your compression ratio.



Ron

[craigandlynda]

they told you this motor was just rebuilt? hmmmmmmmm....must be those new carbon-top pistons i heard were being developed...

[toupee]

Yeah, I would be mad about all this, but, honestly, it's partially my fault.  I haven't been around these things for years like some have, but I really should have went with my gut instinct when I first met the guy selling the car.  Oh well, I'm a trusting soul and I don't imagine this will change that.

I like to look at things in a positive light.  If the car didn't have engine problems then i wouldn't be learning like I am.

I was told though, that the "engine had just been rebuilt by the guy that had the car before the guy I bought it from".  And he reassured me that he hadn't driven it any to speak of.  Now I know why! 

I'll try and get those measurements for TDC.  I already checked the balancer with a piston stop and it is right on so it should take much to measure deck to piston top distance.

[firefighter3931]

See if you can get a few pics of the cylinder walls for us to see. I'm wondering if there is any cross hatch visible on the walls ? 

FWIW, a rich mixture will create a carbon buildup like you're seeing in the chamber and on the tops of the cylinders....this engine could very well have a few thousand miles on it and look that way because of carb jetting. 

Report back with your piston to deck measurements and if possible a combustion chamber volume.



Ron

[toupee]

See if you can get a few pics of the cylinder walls for us to see. I'm wondering if there is any cross hatch visible on the walls ? 

Report back with your piston to deck measurements and if possible a combustion chamber volume.



Ron

Here are some more pictures of the pistons.

I spun the engine until #1 was at TDC.  Here's what I got.




Pics of #7 cylinder....



Pics of #3 cylinder



#5


#1




Straightedged the deck and didn't see any gaps



Straightedged the heads and there is a little gap... don't know if it's normal or not.  I would think the gasket would fill it.



OK, now for the measurements.  Don't know if all of these are needed but I figured more is better than less.

Bore = 4.25" = 10.795 cm
Piston to deck at TDC = 0"
Piston to deck at bottom of stroke = 8.55 cm = 3.366"
Total diameter of piston = 10.6 cm = 4.173"
Flat top of piston diameter = 10.2 cm = 4.016"
Width of countersunk area at edge of piston = .2 cm = .079"
Depth of countersunk area at edge of piston = .1 cm = .039"
Distance from edge of piston to cylinder bore = .1 cm = .039"
Small recessed area in each piston is 4 mm from edge of piston and 1 mm deep

I didn't know how to measure the heads since they aren't a perfect circle and the depth is graduated.  If they are stock 906 heads they should have an area of 84 cc's right?

[toupee]

Well, don't know if I'm even close or not but using my #'s I come up with a compression ratio of about 9.1:1. 

[firefighter3931]

Excellent pics 

The cylinder walls look fine and this is not a high milage engine. There is visible cross hatch in the bores so it has been rebuilt in the recent past....the carbon buildup is from a rich mixture. 

The pistons being at Zero deck is good news for your compression ratio.  Some of the earlier 68-69 hp 383's had positive deck pistons (+ .010) 


The "normal" chamber volume for a 906 casting is 88-90cc if they haven't been cut. Yours look like they have some warpage between the cylinders which will definately contribute to head gasket sealing issues. That should be corrected before you bolt it back together.

Take the heads in to a shop and have them look over the valves/seats etc... and get them to measure the chamber volume.


The calculations assuming an 88cc chamber are 9.02:1 static compression with the .040 Felpro permatorque head gasket which most engine rebuilders use.

With a stock style .020 steel shim head gasket it comes out to 9.42:1 which is what most HP engines came with even though they were commonly called 10:1 engines. 


So, you have a few options ;

(1) Mill the heads just enough to clean them up and use the felpro gasket which will yield a very small increase.

(2) Mill the heads just enough to clean up and use the steel shim gaskets which will bump it up .2-.3 of a point.

(3) Mill the heads .030 and use the felpro gasket for a 9.4:1 ratio


Of those three options i like #3 the best. The felpro 1009 head gasket is an excellent piece and as long as both surfaces are clean and straight it will seal up just about anything....even blower builds running 12-15lbs of boost. 




Ron

[toupee]

I was talking to my uncle today and he said he knew a local guy that did some head work to his 915 heads.  He guestimated about $400 for the 906's.
I'm not so sure what to do.  Aerohead racing has rebuilt 915's for $599.  They seem to be more desireable and it would bump up my compression.  I've also thought about just spending the extra $$$ and going with a set of stealth aluminum heads or eddy rpms.
I am going to go ahead and change the cam while I have the top end of the engine apart.  That way I will know exactly what's in there.
I think I might go with a comp extreme energy 268 cam and lifters.  From what I've gathered that's a good street cam and still makes enough vacuum for accessories to run.  I also have seen the lunati voodoo cams recommended on here, but their 268 seems like it is more radical than the comp one.  Anyone with any experience/advice?

[firefighter3931]

The Comp 268 is an OK cam for a mild build with iron heads but you can do better. 

The right cam depends on several factors ; weight of the car/stall speed/rear end gearing/intake & Carb/vacuum requirements for brakes etc...

How about a rundown on the whole deal 


Ron

[toupee]

The Comp 268 is an OK cam for a mild build with iron heads but you can do better. 

The right cam depends on several factors ; weight of the car/stall speed/rear end gearing/intake & Carb/vacuum requirements for brakes etc...

How about a rundown on the whole deal 


Ron

71' Plymouth Satellite. 3640 lbs according to some web site I found.

68' 383 block. Bore and such everyone knows from the above posts

727 with a cheetah auto/manual valve body

8 3/4" rear end.  I believe it has 3.23 gears.

275/60 15 rear tires

Low stall.. factory I'm guessing.

906 heads NOW, but I am open to suggestions!

Hedman street headers - 1 3/4 primaries

Eddy DP4B intake - Like the car this intake is older than me!    Open to change

I currently have two carbs sitting around - a 600 Eddy performer and a 670 Holley street avenger, will go bigger if need be. 

Power steering

Power brakes

A/C
.......................................................................................................................................................................

I have a budget of roughly $2000.  What this really means is this is the amount of money that I have set aside to goof off with and if I go beyond this I will then be in my "family" money and my wife will become less than pleased with me 

I was planning on buying a mini starter as I hate the large factory one and considering an aluminum water pump.  Though those things aren't really gonna affect the build that much.

Just looking to make as mean of a street cruiser as I can without havening to tear apart the bottom end of the motor. 

[firefighter3931]

Ok, that's a pretty good description & breakdown of the combination in question. 

With that budget i would concentate on the heads and do a cam swap. The 906's flow well enough for a hot street 383 build so just get them milled .030 to bump up the compression a bit. Have the valvejob inspected and corrected if necessary.

The 262* Voodoo split pattern grind would work well in that engine and really wake things up under the hood. Lots of manifold vaccum for power brakes and easy tuning.  You'll want to upgrade the valvesprings while the heads are off. A double roller timing set unless there's allready one in there.

The DP4B is an excellent dual plane and the 670 avenger is perfect....no need to change either of them.

I would like to see a little more stall and gear in the car to get it moving....a PTC 11in street converter and a set of 3.91 gears would really help it launch.

Tuning the ignition is allways worth the effort and it costs very little.

All this should easily be do-able within the budget and make a noticable increase in torque and horsepower.



Ron

[toupee]

Well,

I ordered my 262 voodoo cam with lifters today.    
Say Ron, I noticed lunati suggests roller rockers with the cam I ordered.  Won't make that big a difference if I don't have them will it?

Talked to the local machine shop about my heads.  Here's what I got-

$35 dollars per head to check them for cracks, etc. = $70

To mill the heads = $40 per head for the chamber side and $40 per head for the intake side.... ran into a problem though.  They don't think they can do the intake side at the local shop so the nearest place they THOUGHT might be able to do it is 60 miles. 
Anyways...
Milling = $160

Valves = $160

Valve job/cleaning = $110

So, that means I'm sitting at $500 without valve springs.  Seems like an awful lot to me.   

[firefighter3931]

Well,

I ordered my 262 voodoo cam with lifters today.    
Say Ron, I noticed lunati suggests roller rockers with the cam I ordered.  Won't make that big a difference if I don't have them will it?

No need for roller rockers...the stock pieces are fine. 

Talked to the local machine shop about my heads. Here's what I got-

$35 dollars per head to check them for cracks, etc. = $70

To mill the heads = $40 per head for the chamber side and $40 per head for the intake side.... ran into a problem though. They don't think they can do the intake side at the local shop so the nearest place they THOUGHT might be able to do it is 60 miles.
Anyways...
Milling = $160

Valves = $160

Valve job/cleaning = $110

So, that means I'm sitting at $500 without valve springs. Seems like an awful lot to me.

Here's what i would do with the heads :

Hot tank and magnaflux + pressure test. If there are no problems have them check the guides and valves. If it needs new guides/valves/springs and some milling to raise the compression...this is where it gets expensive. 

If the guides are good and it only needs a valvejob & springs then it's worth doing. Taking .030 off the deck surface doesn't require the intake face to be milled so you can eliminate that machining expense.  Don't assume that the valves need replacing because they might not need to be. 

Basicly, the best course of action will be to get a good estimate before deciding. It might end up being more economical to go with a set of Stealth heads but you won't know that until you see the estimate.

Get pricing on a 3 angle valvejob when you talk to them next.



Ron

[jdscofield]

just curious.  referring back to your comment about being trusting pertaining to the previous owner telling you it had a fresh rebuild.  Did you buy it from a guy named dave in south bend Indiana?  I was like you, trusting.  My fresh rebuild had a blown head gasket, and a blown rear main seal, LOL.  looked rebuilt.  fresh paint on the block except under the motor mounts.  I didn't catch it because I picked it up and hauled it out of state.