Author Topic: Looking for some Experienced Engine Cam/Heads combos. Poncho 400 build  (Read 540 times)

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Offline 1978 TArdboat

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I'm trying to squeeze more power from my 400 poncho motor. It's a 1978 with 6x-8 heads, exhaust manifolds, RPM intake and edelbrock carb and an Auto Trans. 180hp factory car. AC, PS, PB.

I recently bought a set of 1976 6x-4 heads that need a full rebuild, I really couldn't pass up $100 for the pair.
STOCK PISTONS AND BOTTOM END. 15K ON FULL REBUILD
These are the things I want to do and want opinions on:

1) How to get these 6x-4 heads machined
2) Which cam to run with the heads after machining process.

I am also upgrading to headers, that's a given.


The machinist said to bring in my cam specs so they can build the heads to work well with the cam, but I have no clue which cam to choose. SOOOO Many options out there, good lord!

I'm not looking for a drag car, not at all. I'm also doing a full front end suspension rebuild too. I have stock gears *1978 trans am 400 car 180hp factory* (which will be the next modification)

I'd like a decent red light car, just be able to light the tires from a stop. Looking for 400hp ish, slightly lower or higher.

This site has been very good to me so far and i appreciate everyone's input and time.

Offline 72blackbird

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Re: Looking for some Experienced Engine Cam/Heads combos. Poncho 400 build
« Reply #1 on: January 21, 2014, 02:26:31 PM »
Getting 350-400 hp from a 400 with ported 6x-4's is possible, but using an existing shortblock with unknown specs makes reaching your hp goal more difficult. It all depends on how well the short block was built- quality short blocks have file fit rings with consistent ring gaps, zero to .010" piston-to- deck clearance, blueprinted oil clearances, decked and align honed main saddle, and a balanced rotating assembly. Unless you know all of these steps were taken and know the shortblock specs you won't even know if the pistons and rings will adequately seal the added compression from milled and ported heads, or if the block has good oil clearances. If you chance it and add ported/milled heads and a cam to the existing shortblock, there's a possibility the performance will fade due to shortcuts in machine work and/or cheap internals.

There are so many variables involved in an engine build to get a specific hp output- the builder of your engine needs to pick the cam, set the SCR, and pick the right internals. You should ask him what he thinks is the best cam for the job- if he doesn't know, you should find a builder that does and has a reputation for good work, as well as has references. If he can't port the heads, have them done by a porter who knows how to do Pontiac heads- the current Pontiac books on Pontiac engine building are good reference guides.

Geno