396 big block...some questions... - Team Camaro Tech
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post #1 of 4 (permalink) Old Dec 29th, 05, 10:57 AM Thread Starter
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Question 396 big block...some questions...

I have a 68 coupe with a 396 big block conversion...done some time back so I don't really know what's in the engine. It has oval port heads, big hooker header pipes (2" I think), roller cam/rockers, Edelbrock performer intake and holley D/P carb. I know this is a guess, but what should a healthy big block be able to safely rev to...with so many unknowns?
I know we should strip the engine to check it out but that's a job for down the line...so any advice appreciated.

I have also found out from my mechanic that it has had a Pontiac TH400 dropped in behind the engine- with some sort of plate to adapt it to the Chevy block (with 4 bolts instead of 6). Feels fine and shifts great, but is this likely to become a weak spot?...has anyone else performed this swap?

One other quick thing....my mechanic has set timing etc without vacuum advance- as he can't set that up without knowing which cam is installed..he does know his stuff so I trust him (!) but will this create problems with idle/cruising?


Last edited by Lol_uk; Dec 29th, 05 at 11:08 AM.
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post #2 of 4 (permalink) Old Dec 29th, 05, 11:34 AM
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Re: 396 big block...some questions...

As far as revving, on the highway in 2nd gear, slowly rev up to the point where she starts to lose power or rev up to the point of valve float (will start to miss) and set your red-line a bit below that. If she starts to break up in lower rpms, 4000 for instance, you'll need to diagnose problems with timing and/or fuel delivery first.

You'll need vacuum advance for ordinary street driving,.. esp cruise and idle. it will run better, better mileage, and stronger too.

As far as setting the timing, buy a timing light and learn to do this yourself because it's a trial and error thing with these old cars. Do a search on this site,..I'm sure there's instructions,..it's easy.

The BOP adapter for the tranny doesn't worry me.

Good luck with your new ride!
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post #3 of 4 (permalink) Old Dec 29th, 05, 11:46 AM
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Re: 396 big block...some questions...

I would put in a fresh set of plugs first because an old set could also miss at high rpms.
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post #4 of 4 (permalink) Old Dec 29th, 05, 10:32 PM
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Re: 396 big block...some questions...

I have built a few big blocks . I tell by cust. with stock crank/rods rod bolts do not rev over 5000 . thoses motors was not designed for high rpms
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