400 sbc build

[CHRIS.O]

can I run a 406 on regular pump gas. I havent made a concrete descision because I want the 406 but this will turn into a expensive build if I go this way. My first idea was too go with a stock rebuid with a comp 292. Will this give me a little more horsepower and I really want the cam sound! Is this possible with just a stock rebuild plus flat tops and 5.7 rods w/small base circle 292?

Running it off of pump gas is determined by your compression ratio. You need to figure out what your compression ratio is going to be before you pick anything else really. Your compression ratio has to do with what cam you will use as well. I would personally shoot for a compression ratio between 9 and 9.5:1. Also shoot for a quench of about .040. Those two measurements will allow you to run it off of cat piss if needed.

 

[chevy2480]

With 9.5:1 compression you would want to run plus or better. The fuel today is not as good as it use to be. I wouldnt run regular in my lawnmower.

 

[CHRIS.O]

With a .040 quench or close he should be able to run it with proper timing. 9:1 is still acceptable. Just get out of that 8:1 range. I agree, today's gas is garbage. Even some of the higher octanes.

 

[87ttop]

I always run mid grade or higher anyways is that fine I know I want the comp 292 small base circle, flat tops, 5.7 rods original 400 crank (turned?, polished?) headers, im not sure if I should go with my factory heads or get new ones. I just wont have a lot of funds until income tax, what do you guys think on internals and any suggestions on heads new one? or rebuilt stocks (72 year model) capprice

 

[DRIVEN]

If you have your heart set on the 292 cam then you will need 9.5 or better CR. That means you probably won't get away with regular fuel. You could run stock CR and run regular but that cam won't be happy and you'll end up with a blubbering gas hog with disappointing power. I just went back over your thread and at the beginning you were saying that all you want is "nice and powerful with a hard thump". That's not really specific, honestly. Performance engines have certain requirements. Just putting a 400 in place of any factory Gbody engine will feel like a performance improvement. That's due to the increase in torque. This is very different than an increase in horsepower. It sounds to me like you still aren't really sure what you want. Is it really just a lumpy sound? Do you really just want a poser engine that sounds good but can't back it up?
I will make the same suggestion I made 3 pages back -- focus on torque. That's what 400s are good at. If you were building a 327 or a higher compression 350 with good heads I might be more excited about your cam choice. I like the Xtreme Energy line for engines like yours for a couple reasons. They don't need much CR to run right. Their lobe profile was developed to emulate that of a roller cam - higher lift with less duration. You'll get a snappier throttle response and higher vacuum. Good vacuum requires no special carb tuning and doesn't effect power brakes. If you look at some of the dyno sheets you'll see the don't post huge HP numbers but they do make nice fat torque. Torque moves your car. Torque is fun on the street. Torque gets better MPG. Take a look here:
http://www.compcams.com/Content/StaticC ... eSupport=1
It's your car and your money but I think you owe it to yourself to be honest about where you want to end up.

 

[drogg1]

I agree with DRIVEN that that cam is rather large for a street car. Bigger is not always better etc., etc. However, if you have you're heart set on that cam/duration, I will disagree with DRIVEN in that I think you will be able to get away with MORE compression due to the bleed off caused by the late intake closing point. So, you very well may be able to have 10:1 compressions and run just premium gas with the proper tuning. He is right that the Comp Xtreme Energy cams are good all around street cams. I'm running a XE282 solid in my 383 but I'm also running forged parts, 13:1 compression, and E85. Even with my high compression I think the duration is in the top range for a street cam for a 383.

All in all, do your research, make an informed decision, and you'll get the results you want.

 

[DRIVEN]

^^Good points there^^. I think it'll be fine on pump gas (plus or premium) even up to 10.0, like you said. What I meant was that regular (cheap) gas might be out of the question. Maybe my wording was a little ambiguous :lol: . I agree 100% that it would run if tuned correctly. There's probably enough duration in there to run fine. I guess the point I was trying to make was that a stockish 400 wouldn't fully appreciate that 292 cam. If it were a more performance oriented engine than it'd be a different story. Hope that makes more sense. I guess none of our speculation really matters much until 87ttop makes a final decision about what he really want to end up with.

 

[chevy2480]

From talking to him personally. He is going to go with 5.7 rods, flat top pistons and the 292h cam. With flat tops he should be somewhere around 9.5. Depending on a few other veriables. But I can tell you with experience that the 292h has very good street manners and produces plenty of vacumn. I have used that cam in a bunch of sbc with compression rangeing from 9:1 to 10.5:1. Non of those motors where dogs at all. I think he will be perfectly fine with that cam speaking from what i know. But as anyone who builds motors you can build three identical motors and non of them will run the same.

 

[DRIVEN]

Sounds like a solid foundation. I think it deserves better heads.

 

[CHRIS.O]

I think it deserves better heads.

I agree. That bottom end combo will be a nice set up. Be a shame to see low performance heads go back on it.