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402 rebuild

SShultz

SShultz

1/2 ton status
Joined
Jan 16, 2008
Posts
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Location
New Mexico, Fort Campbell KY. (currently Iraq)
OK now that you wonderful people helped me out with my 400 vs 402 issue, I need to know what needs to go into this 402 to make it as good of a motor as it can be on a budget. Any bigblock tips and tricks?
Thanks
SShultz
 
Once 4X4HIGH checks this thread, you'll have all the info you need...

:usaflag:
 
SShultz, not to hijack your thread, but thank you for your service to your country. When will your second tour be over?
 
Going to need more info on what you're wanting to do with this engine. Are you wanting a torque engine, or HP. Is it going to be carbed or FI?
 
I would suggest you find a set of "781" heads and install the larger 2.19/1.88 valves and keep compression close to 9:1 and choose a conservative (smaller) Comp 4X4 grind cam. Use an intake manifold that is low profile and a carb that's around 750cfm. If you decide to go FI later down the road you'll need to swap to a FI friendly cam. A good set of headers as well. I suggest a single 3" exhaust to help produce good low end torque.
 
They are in most big blocks from mid 70's to mid 80's . 10 bucks says your local shop has a set on hand at any given moment :thumb:

They are pretty good heads for lower rpm motors , or budget builds . Many guys on the Chevelle site I lurk on run them . Some of those guys make 500 hp or so with em .
 
"781" refers to the casting number on the head itself.

They are under the valve cover area, and 781 is the last three digits of a longer sequence number.

For the complete number, you can look at:

www.mortec.com

Pretty much the bible for Chevy casting numbers (blocks & heads)

Here's what you'll see:

336781 (73-85...oval...OPEN...454, 118cc chamber, 256/114cc ports)



Might also want to look at this thread:

http://coloradok5.com/forums/tags.php?tag=781
 
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I'm running a BBC 402.
Stay with a moderate cam with an RPM profile 1500-5000 RPM and avoid one with a lot of overlap unless you intend to flog the upper RPM areas.
Match piston type with heads - OC/CC and shoot for 9-9.2:1 on premium or less on lower octane. You can always mill the heads for the compression range you're looking for provided the manifold fit is addressed as well.
Pocket porting is a decent investment on a good set of heads. Oversize valves not strictly necessary unless the seats are shot or you will be going with a higher RPM range or 454/stroker block.
Edelbrock RPM series manifold
 
OK just two questions left. Headers or stock exaust manifolds? And as far as a cam goes I've decided on the COMP Xtrene energy 4x4 kit, but should I go with 1000-5000rpm or more in the range of 1500-5500rpm? I really want this truck to be as dependable as it is usable.
SShultz
 
I agree with the smaller of the cams, alot more usable for what you've stated your intended usage is.
 
OK then! Thanks for all your help 4x4HIGH and the rest of ya'll too!:bow: I'm confident that this build is going to turn out great for the truck. I'll make sure to keep you posted on the entire truck build when I get home from this place. Thanks again!
SShultz
 
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