Thread: 400 small block buildup

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I am building a 400 ci. small block, I already have an edelbrock rpm intake, 750 holley carb.,and edelbrock rpm heads with 64cc chambers. I was going to go with a comp cam xe274. I am looking for 425-450 horsepower, does anyone have any cam suggestions, and am I heading in the right direction with this buildup and my expectations.

The 400, due to it's long stroke, is sensitive to changes in the combustion area. You are going to need pistons with a large dish to keep your compression ratio down to a level that will let you run pump gas. I have Edelbrock RPM heads with 70c.c. chambers on my 406 with flat top pistons and can run pump gas without having to back off the timing too much.
The 400 also likes more camshaft than a 350. This has something to do with the stroke and the cylinder diameter, it's really engineer stuff, just remember that you get to have a bigger cam and be happy. That Comp XE274 is going to feel like a stock cam. If you want to stay with a Comp cam check out the XE284 as a mild street cam or step up to a bit more of a dual purpose cam with the XE294. My 406 is a weekend only driver on the street and at the dragstrip and I'm using a Lunati solid lifter cam that is 300 / 308 seat to seat. Part of the reason that I'm running that much cam is to bleed off some dynamic compression. You can read about and download a program from this site that will help you determine what you need as far as compression ratio and camshaft.

What can I do to lower my compression other than changing my heads. I did not plan on running more than 10.5 to1 cr.. My other cam choice was a comp cam 292 or 305., are any of those cams similar to your lunati. My car will also be a weekend only driver, but I want to be able to drive it to the track and back on 93 or 94 octane, and the track is 2 hours away.

If you've read the page that I posted earlier and downloaded the program you can see from the program that retarding the timing by 4 degree will decrease your dynamic compression ratio. The 292 cam that you listed may be a good choice for you. I assume that you are looking at the XE292 camshaft. Try running the numbers for that cam in the dynamic compression ratio program and if it's still too high try retarding it 4 degrees.
If you haven't built up this engine yet then using 400 pistons with a dish will help a bunch. In fact this is the best solution to drop the compression ratio. There are pistons avaiable with a D shaped dish from 16 to 30 c.c.s, these will lower the static compression ratio and let you be a bit more selective in choosing a camshaft. Do not use a head gasket thicker than .032 inchs thick if you can avoid it.

I called the comp cam tech line and they were the ones that recomended the cam. It is part of their magnum cams, and not their extreme series. I bought the engine assembled from a friend of a friend as a short block, so new pistons are not in my budget at the moment. I will download the program and run the numbers, and see where I stand. Thanks.

You can find the cam card information for the 292 Magnum here http://www.compcams.com/Technical/Se...umber=12-213-3 It should be a good choice.