cc's per thousandth milled?

[i c e b l u e]

Does anyone know the amount of cc's lost per ".001 decked from 906 heads. My heads cc'd to 91 cc's and i am looking to get them to around 87cc's

    Marcus

[is_it_EVER_done?]

C.C. change for each THOUSANDTH cut is impossible to even guess at, much less quantify. Due to the extreme amount of core/casting shift in a stock head, the chamber volumes and shapes are not predictable. some (stock) heads measure out at around 88CC to other identical castings being in the low 90's

Also, there is no way on earth you could tell the difference in power output from a 91cc head to an 87cc head. in fact, you could possibly decrease performance a bit by bringing the quench area closer without actually getting into a "real" quench dimension, so you should error on the side of caution (not to mention saving money) by skipping the head milling and using them as cast.

I honestly doubt that you would be changing the power level of your engine by even 3 HP one way or another with the ultra slight increase in compression.

For such a minimum desired change, you will spend hundreds, and cause tighter lifter pre-loads (less power, and possible burned valves), plus you will most likely increase the engines propensity to ping, which could cost you dozens of HP to cure Through reduced ignition timing, or higher octane fuel.

You will be far ahead by choosing a cam based on the non milled compression.

[Challenger340]

Approx. 2.4 cc per .010" milled on a 906 head.

[i c e b l u e]

Challenger340

Thanks, I would also like to thankyou again for the pictures of your 915's, I just flowed one of my 906 cylinder heads and I got 273 cfm on the intake and 230cfm out the exhaust, so now I have to get back into gear and finish my other head

is_it_EVER_done?

First, I completely understand how each head can very. I probably should have rephrased my question as to an estimate or general rule of thumb for example look at challenger340's response. I have also seen 906 heads range anywhere from 87cc's to 90cc's mine started at 88 and then by deshrouding them with the serdi and polishing the chambers they are now at 91cc's

Secondly, I never said i was doing this for performance gains, so in case you were wondering, I will be squaring up my heads because they are warped by about  .001(I didn't blow a head gasket i just checked them while I have them off for porting and it turned out they were a little off) Since I will be doing this myself and it will only cost me time, I will bring the cc's down to keep me from milling the block of having to offset bush my rods. Milling the heads will also help me terms of quench as they are all exactly .095 away from the deck.

On a street engine with steel rods you can run a quench of .040. therefore with the pistons .055 in the hole with a .039 compressed head gasket and .095 or less in the heads adds up to .189. Since the comp. dome on the piston is .135 (.189-.135=.054)there fore my maximum tolerance for quench is .054 and either by milling my head, or offset bushing my rods I can achieve a .040 quench with 9.5 to 1 compression

As far as lifter preloads, I am using comp promagnum rocker arms which are adjustable, and who said anything about selecting a cam???

Also from my experience with this piston choice 9.8 to 1 compression is capable on 93 octane and no signs of predetonation. In fact on our dyno we found by taking a three degrees of timing away to a total advance of 29 we only lost 2hp but gained 12 ft lbs of torque. Thanks for your concern about my time and money though

[is_it_EVER_done?]

I never said i was doing this for performance gains,

Actually you did by posting the question in the Performance section instead of the General section.

I apologize if my response didn't address your question, but given the question and section it was posted in, I responded based on someone who was trying to gain performance through a 1/10th or so increase in compression.

and who said anything about selecting a cam???

That would be me that made the suggestion. Again it was based on your original question and section it was posted in.

Good luck on your build.

[jg68]

Iceblue, i agree with chally340, figure about 2.3cc for every .010 milled, if i might ask, why are you only wanted to go to 87cc , thats not really even worth doing unless you just want to clean the up

[i c e b l u e]

jg68, here's a little snapshot and update on my build

Block: 440, (4.350).030 over thus 446

Rotating: stock forged crank, ly rods with arp hardware both rods and mains
              Kb p# 184's (have adv .140 comp dome(actually only .135)

Heads: ported 906 heads that i just finished flowing today, 2.14/1.81
(chambers are 91 cc's currently with .095 quench area(i matched))

Finally flow #'s (68* F, 30.1 B. P., 55% Humidity) Superflow 300 w/ flow com and calibrated at 28"
Also: hand formed clay radius and exhaust tube

int lift/cfm
.100/67.5
.200/135.4
.300/199.8
.350/227.2
.400/252,5
.450/270.9
.500/271.2
.550/272.7
.600/267.5(after .550 port was saturated)

don't have the exhaust #'s on me but they came to 220cfm and .5 and maxed out at 235 cfm at 650 or so but is pointless as my cam lift has only .525 with 1.5 to 1 rockers, see below

Cam: comp cam xtreme high lift(spces int/ex) lift .525/.525 dur@ .5  231/237 lsa 108

intake: Stock(heavy smothering hp 4bbl)

Carb: (currently 750 speed demon w/ vacuum secondaries) But my go to 750 or 850 qft with mechanical
       secondaries

Exhaust: 1 and 7/8th tt1 headers to 2.5 with x pipe and dynamax super turbos

trans: 727 rebuilt with 2300-2500 precision converter

Diff: 8 and 3/4 with 3.55 suregrip

Tires: 295/50/15's grade A, but if i can afford it may some mt street radials(they would also be taller) Need better 60fts 2.06 isn't good(but bog also contributed)

Et: was a 13.502 @103.55 and hope to hit mid 12's (the heads only flowed 245 cfm, plus burning oil and no quench)

See below for further details and explanation for an 86 cc combustion chamber:


For Compression Ratio                                                               For Piston Protrusion Height
            
4.350   Bore      6.768   Rod Length
3.750   Stroke      1.992   Piston Compression Height
3.500   Piston Dome or Dish No. (in cc's) (dome = above (+), dish = below (-))      1.875   1/2 of Stroke
86.000   Cylinder Head Volume (in cc's)                                                                      10.635   Stack Total
0.039   Head Gasket Thickness         
4.410   Gasket Bore Diameter                                                                                      10.695   Actual Deck Height
8.000   Number of Cylinders         
-0.060   Piston Protrusion (Stack Total)                                                                      1.805   Rod to stroke
                                                                                                        -0.060   Piston Protrusion Height
9.566   Compression Ratio Calculation                                                                     -0.099   Squish Area(Wo/O cha)

with comp dome, and .020 off my heads i should be at .046(at most .043 at least as stock rods c to c length can vary and I have checked all piston protrusion heights) for quench and 9.5-9.6 to 1 comp ratio!

[jg68]

Now i see why, sounds like i nice combo, check this out, i ran 10.9s @ 122+ with bone stock 906s with no quench , but that was in my 3100 lb. A body

[i c e b l u e]

 :owow, even if every 100lbs is a tenth thats still fast, must of had some impressive 60fts, i hope to see mid to low 12's with some street slicks so i guess i will find out this summer

[jg68]

:owow, even if every 100lbs is a tenth thats still fast, must of had some impressive 60fts, i hope to see mid to low 12's with some street slicks so i guess i will find out this summer

Hey ice, my 60fts were horrible, 1.58-1.62s, after i did some tweaking to the heads & put on a TR, it pulled off a 10.87 @ 123.58 on a 1.61 , it was easily a 10.7 car, the guy i sold it too got it to break 124 mph  , & he's a big boy, not bad for a lame 906 build.

[firefighter3931]

Nice work on the heads....those are excellent numbers !  You should have enough for 12's if you can get it to bite at the track. 


Ron

[i c e b l u e]

Hey ice, my 60fts were horrible, 1.58-1.62s, after i did some tweaking to the heads & put on a TR, it pulled off a 10.87 @ 123.58 on a 1.61 , it was easily a 10.7 car, the guy i sold it too got it to break 124 mph  , & he's a big boy, not bad for a lame 906 build.

Horrible?, i know its apples to oranges but my 60ft was 2.06 where i have seen guys in the 1.8's to 1.9's.  do you have the specs on that build? as it sounds pretty impressive number wise.

Nice work on the heads....those are excellent numbers !  You should have enough for 12's if you can get it to bite at the track. 

Ron

Thanks ron, after spending about 35 hours on those heads, it made me never wan't to do that again and just let our cylinder head porter do it. But i guess now that i look back at it, I learned a lot and i can say i did it. but I also couldn't have done it without the help from this board too, so thanks again everyone.
As far as hooking up is concerned does anyone know if these
(6641 28X12.00R15LT 31 8.5-10.0 10.0 12.1 10.4 28.0 )
mt's will fit in a 2nd gen on a 15 by 10 rim with 5 in backspacing? I currently have 295/50/15's and looks like i still have more room to play with, just curious if anyone has already done this?

Or these(325/50/15's) http://www.bfgoodrichtires.com/specs/g-force-t-a-drag-radial/1161.html

I will be sure to post back with dyno numbers once its back together, and eventually et #s when it warms up!

[firefighter3931]

Have a look at the Mickey Thompson drag radials....they hook awesome and are well suited to a heavier car. Radial design with a stiff sidewall. Some 10.5in tire guys are running into the 7 sec ET range with these skins ! 



Ron

[i c e b l u e]

thanks firefighter, i will definately check them out

[jg68]

Have a look at the Mickey Thompson drag radials....they hook awesome and are well suited to a heavier car. Radial design with a stiff sidewall. Some 10.5in tire guys are running into the 7 sec ET range with these skins ! 



Ron

, i put some 275/60/15s on the back of my 440 powered D100, them suckers HOOK even with a 125 shot

[jg68]

Ice, here are the specs, never been on a dyno, so i don't know what the HP #s were, really didn't care, it ran good no matter what it had

75 400 block, bored .030
440 steel crank (counterweights turned down)
440 LY prepped rods, arp wave locks
Ross FTs, 1009 gaskets .009 below deck, final comp. 9.73
Milidon 7 qt. with windage
Bone stock un-ported 906s, new stainless 2.08/1.74 valves, 10 deg. locks, isky 8005A springs, 90cc chambers.
XE284H cam, pro-magnum lifters, crane ductile iron 1.5s
M1 single, swap meet 750dp with PF MB, 74,82 jets
MP dizzy (mallory plate) 14* int. 35* total, all in at 2200
PTC 9.5 4100 flash stall, 4.11s, SS springs
Best run with this set-up: 10.91 @ 120.56 on a decent 1.51 60ft. in mine shaft air.

Changed to a comp. custom solid: 543/529 gross lift, 250/256 @ 50 on a 108 LSA
Caltracs.
Best: 10.94 @ 122.72 on a 1.58 60ft. in the same good air.

Pulled heads, spent 25+ hrs. working them , same small valves, weiand TR with 2 swap meet 600 1850s.

Off the trailer with no tuneing  in 90* heat, the first & only run.
10.87 @ 123.58 on a 1.61