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  #1  
Old Aug 6th, 08, 1:52 AM
joespc37 joespc37 is offline
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joe
 
Join Date: Jul 2008
Location: wash state
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Default 402 bbc engine

ok guys i have a 72 passanger 402 looking just to make some streetable tork not for strip,motor is all stock with standard bore need to this cheap, suggestion ppl are telling me to get closed chamber heads instaed of these oval open chembered heads that are stock to this motor, if thats true what heads should i be looking for i see all these different number and to be truthfull it will get a guy lost, planning on a smaller cam either hydralic or solid i like sound of the solids,setting motor to run up to 5500 or so nothing crazy but like the thumpper sound and like to do smoke shows help please also running turbo 400 with 12 bolt posi and 308 s
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  #2  
Old Aug 6th, 08, 11:45 AM
kettbo kettbo is offline
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George
 
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Location: Lakewood, WA
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Default Re: 402 bbc engine

Joe, Joe, Joe,

OK, saw your other post on heads....
Your 292 oval open chamber heads are fine....
8.5:1 CR 240 horse/345 ft lbs torque NET ratings with accessories, right?

Everything is relative....cost and time.

Cheap is to re-use what you have...it is a runner, right?
Have a 3-angle valve job done by a reputable shop. Have them install springs to match your cam. Get some bowl clean-up under the valves.
Have them shave the heads a bit to true them up and also decrease the chamber size.
Run a shim head gasket like the MR GASKET 1302. (think this is not right...1131 IS the right number) They feature .018-.020" compressed thickness compared to most head gaskets which compress to about .040". You will have to apply spray-on sticky stuff and you will have to re-torque the heads after you fire the engine.

Shaving the heads and the shim gasket will bump your CR closer to 9:1
Let's use the KB compression calculator for the 402" piston KB-160
http://kb-silvolite.com/performance....tails&P_id=105
119cc chamber is 8.5:1 (caution here, chamber size varies)
115cc chamber (equivalent of shaving the deck and the shim gasket)=8.8:1
Now take the small chamber 385206 head from 1966 era has 97cc, shaved to 95cc no issue.... CR comes out 10.6:1
Roughly 4% per 1 pt in CR.....10.6 - 8.5 = 2 pts, 8% increase
Figure 300 horse x 1.08 = 324 horses....gain of 24 horse. You can really feel that.

Thing is, high compression/small cam combo means detonation.
Probably a better gain from the compression is that more CR supports a bigger cam, no soggy bottom end. Low compression/modest cam; medium compression/healthy cam; lotsa compression/stupid cam....

So, cheapest route, fix your 292 ovals...run a modest perf cam....
hmmm, small solid preferred....
No time now to go looking for cam grinds.....
Modest compression, 3.08 gears...street, limited rpm...
Something solid 225* roughly at .050" lift, lift will come out at .520-.540", 108 LSA

Though a smaller Voodoo Hydraulic 60201 or the Summit brand hyd 1301 (same as the Edelbrock Performer cam 214/218* .500/.500" 114 LSA) would work well....
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Last edited by kettbo; Aug 6th, 08 at 2:49 PM. Reason: gasket number corrected
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  #3  
Old Aug 6th, 08, 1:30 PM
Bubba's 69 Bubba's 69 is offline
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Marty
 
Join Date: Jan 2008
Location: Virden,IL
Posts: 479
Default Re: 402 bbc engine

You said cheap, how about this. Throw some shim head gaskets in it, intake, cam, and headers and you will have power to spare. I run a lunati 00024 230@.050 .544 lift. I wish the powerband was shifted a little lower. If I were to pick a different cam that would allow me to keep the lumpy idle, I would go with this one.....http://store.summitracing.com/partde...4&autoview=sku


CCA-CL11-600-4 Camshaft/Lifters, Hydraulic Flat Tappet, Advertised Duration 279/296, Lift .498/.483, Chevy, Big Block $215.95

MRG-1131 Head Gaskets, Steel Shim, 4.370 in. Bore, .018 in.-.020 in. Compressed Thickness, Chevy, Big Block, Pair $19.95

SUM-226024 Intake Manifold, Stage 2, Dual Plane, Aluminum, Natural, Square Bore, Chevy, Big Block, Oval Ports, Each $179.95

SUM-G9010 Headers, Full-Length, Steel, Painted, Chevy, Camaro/Chevelle, 396/402/427/454, Pair $89.95

How's $500 for cheap. Of course you will need gaskets and other odds and ends so figure on another couple hundred for misc stuff.

I think with only .498 lift you could reuse your stock springs, but while its out you had better measure and install new seals.
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Old Aug 6th, 08, 3:57 PM
OLDED OLDED is offline
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Ed
 
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Default Re: 402 bbc engine

I have a similar set-up 402+ .030 and about 9.5 comp. and wouldn't trade the Lunati 60203 kit for anything else I have seen, felt and heard in a mild, low cost 402. It sounds REAL healthy out the 2 1/2" pipes and is just plain fun. He will make 375 - 400 flywheel HP.
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