402 bbc engine - Chevelle Tech
Engine AdvertisementGeneral Engine Discussion.

LinkBack Thread Tools Search this Thread Display Modes
post #1 of 4 (permalink) Old Aug 6th, 08, 1:52 AM Thread Starter
Tech Team
Join Date: Jul 2008
Location: wash state
Posts: 163
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
joespc37 is offline  
Sponsored Links
post #2 of 4 (permalink) Old Aug 6th, 08, 11:45 AM
Lifetime Premium Member
Join Date: Mar 2006
Location: Lakewood, WA
Posts: 11,215
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
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....

George Kettler
o SOLD 8/2016 my beloved 1970 Elky 496.
o 68 Vette 427/M-20/3.36 23 year owner
o 68 Camaro Vert 327 project, painted, assembly stage http://www.camaros.net/forums/showth...183654&page=55

Last edited by kettbo; Aug 6th, 08 at 2:49 PM. Reason: gasket number corrected
kettbo is offline  
post #3 of 4 (permalink) Old Aug 6th, 08, 1:30 PM
Tech Team
Join Date: Jan 2008
Location: Virden,IL
Posts: 480
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.
Bubba's 69 is offline  
post #4 of 4 (permalink) Old Aug 6th, 08, 3:57 PM
Team Member
Join Date: Feb 2003
Location: Marietta, Ga.,USA
Posts: 3,128
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.

OLDED - It's STOCK if it's made by GM and it fits!

*65 Elky, Gen VI 496 BBC, TH400
*59 Vette, 283/270 hp. T5 5 spd., 4:11 posi.
*Harley - 06 Street Bob
*Life Member - Team Chevelle & Team ElCamino
*Peach State Chevelle Member
*Retired June 1, 2014****
OLDED is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Old Thread Warning
This Thread is more than 3246 days old. It is very likely that it does not need any further discussion and thus bumping it serves no purpose.
If you still feel it is necessary to make a new reply, you can still do so though.

Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome