help with big block heads - Team Camaro Tech
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post #1 of 11 (permalink) Old Mar 11th, 10, 01:02 PM Thread Starter
floyd
 
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help with big block heads

hi,new guy here. i'm putting togther a 402 for my 71 camaro.it has the factory dome pistons in it. i have acquired two pairs of heads. first pair is casting#3964290 closed chamber 100cc wich i think will put my compression at about 10.25. and the other set is casting 350349 122cc open chamber wich would put compression at about 8.3 . for a daily driver with near stock cam, to run on a normal grade of gas i would think the 4290s would be too high a compression. but would the 0349s be too low ? any ideas ?

71 camaro 402,4speed
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post #2 of 11 (permalink) Old Mar 11th, 10, 02:05 PM
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Wink Re: help with big block heads

I think you've transposed the open chamber head numbers
And I believe the measured volume is closer to 112~114cc - which may help your decision ...

you can use a clever cam choice to tailor the DCR to you use needs

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post #3 of 11 (permalink) Old Mar 11th, 10, 02:11 PM Thread Starter
floyd
 
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Re: help with big block heads

i wonder if there would be any piston to valve clearance issues useing the open chamber head ?

71 camaro 402,4speed
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post #4 of 11 (permalink) Old Mar 11th, 10, 02:22 PM
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Re: help with big block heads

Only measurements will tell

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post #5 of 11 (permalink) Old Mar 11th, 10, 03:10 PM
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Re: help with big block heads

The 402 normally used Open Chamber Heads and corresponding Open Chamber Pistons. You can use Closed Chamber heads on Open Chamber Pistons BUT you must ensure there is no Clearance Issues, some work some Interfere and you MUST Mock the System using Plumber Putty. It only takes a little messaging to the Domes to make them FIT.

10.25 Static Compression is IDEAL for a Pump Gas BBC. Choose a Cam to give you a 8.2 DCR. Recommend the Comp Cams XM278H-12.

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post #6 of 11 (permalink) Old Mar 11th, 10, 03:41 PM
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Re: help with big block heads

Hey Floyd. Welcome? Do you need help with DCR?
But don't listen to Ron.

One owner 69 Camaro,(yep, bought it new
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post #7 of 11 (permalink) Old Mar 12th, 10, 01:24 AM Thread Starter
floyd
 
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Re: help with big block heads

i'll get some putty and check it.

71 camaro 402,4speed
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post #8 of 11 (permalink) Old Mar 12th, 10, 01:44 AM Thread Starter
floyd
 
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Re: help with big block heads

i never heard of dcr till now. i only knew about the static compression ratio. the cam i'm looking at getting is the lunati voodo 60211. think that would go better with the closed chamber heads?

71 camaro 402,4speed
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post #9 of 11 (permalink) Old Mar 12th, 10, 06:03 AM
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Re: help with big block heads

I've seen open chamber heads all the way to 130cc's, never had any come in under 119. The 290's are semi-closed chamber, should be around 106 or so. True closed chambers are 702's, they're around 100cc's. I've measured a bunch, these aren't just figures I've pulled out of the air.
Being on the coast, the dynamic compression calculator applies to you. It doesn't work well for folks at elevation since it doesn't take it into account.

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post #10 of 11 (permalink) Old Mar 12th, 10, 11:36 AM
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Re: help with big block heads

Along with the Putty Check, bolt the head to the Block and Scribe the Bore Diameter onto the Cylinder head then Grind to that dimension - You will find that you have to Radius the Combustion Chamber around the Exhaust Valve for better Flow as it is tight there.

I Scribe all my Heads to Bore, BBC or SBC.

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post #11 of 11 (permalink) Old Mar 12th, 10, 01:27 PM
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Re: help with big block heads

Ron! Where were you with that tip when my rotating assembly was out?????

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TH400 (CX) with Coan 8" converter, GV-OD, 8 track still on console and best et 10.495,
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1000cfm AED and HD Harold-Lunati SR, 725 lift with shaft rockers too.
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