400 Hp

[z7199]

I pulled the motor again on the old 72' and am going to do it right this time. I want 400 HP or more but at least 400. So I am asking you guys how do I get there what all do I need to do and be specific (not just cam) what size and everything. I have never done this but can read and follow directions. Also I am pretty good with most vehicles just a little worried. Oh and its a 402 BBC

[70rs/ss]

Start with the heads, have them flowed on a flow bench. Port work will help and not cost too much. Once you have a cfm number on the heads and at what lift, then pick the cam that matches. Motors are big air pumps, piston goes down pulls air in, squishes it, and then pushes it out. The key to power is get more air in, squish it tighter (higher compression) and get it out faster. The air flow is handled by the heads (they limit how much air comes in and out) then the cam lifts the valves to let that air in and out. If you match the cam to the heads, half the high hp battle is won, then look at compression. with iron heads 9-9.5 is as high as you want to go. It should make 400 hp easy, that only 1 hp per cubic inch.

[z7199]

Okay well I guess the head shop will be able to give me the CFM's on the heads after they are done with them? Also what will give it higher compresion the heads or pistons or what?

[70rs/ss]

You will need to know the cc's of the head, and them pick the piston accordingly. shaving the heads will gain compression, but 9-9.5 is all you want with pump gas and iron heads. Your heads are probably a 118cc head, which will need a popup piston to get the comp up there. I bought a set of gen VI heads, and if you are putting any kind of $$$ into you old heads you are way better off with the newer heads, as they have the heart shaped chamber for better flow, they are 100cc's and they flow a ton of air compared to the stockers you have. Bare castings can be had cheap (brand new) which means less $$ on machine work. The flow numbers are readily available for those heads, so then you call up a cam company and ask for the lifts you need and away you go. My 454 put out well over 500hp and is very tame because of the cam and heads. If I was building a BBC from scratch I would spend the bulk of the cash on heads, because that is where the power is made.

[Billla]

400HP is pretty conservative for a 402. Just about any well-matched combo will deliver that level of power. Need a bit more information before there's an easy answer:

• How much do you want to spend?
• Transmission (auto/man, type)
• Anticipated rear-end gears?
• Use of the truck

The last is probably the most important point - do you want a drag monster, something VERY streetable or somewhere in-between. Think about it before you answer - there's nothing worse than an engine that's very good at one thing only to be (ab)used for another. I'll desktop dyno the answers until we get what you want

[70rs/ss]

Hey I'll shoot a pict of the Vortec chamber. My machine shop guy helped me pick my parts and said he had built several combos like mine except that my vortec heads were way better than the ones he had used in the past, and those motors pulled 500+hp. Mine should be in the high 500hp range and is very streetable. I think 400hp out of a 402 should be very obtainable and streetable as well.

[z7199]

Well I just thought 400 was a good low number that I could get to pretty easy. The more the better but price will have something to do with it. If I can do 400hp for 500 dollars then great but if I could do 500hp for 600 dollars then that will be it. I have the turbo 400 auto tranny and I belive 4:10 maybe even 4:56 rear-end It is the stock gear. I was also thinking about a little bit bigger bore maybe I took the heads off yesterday and the cylinder walls look pretty good but I was thinking a little bigger to clean them up.

Here is the link to some pics

http://www.cardomain.com/ride/456511/8

[bigjimzlll]

400HP from a .030 over 396 should be pretty doable. It is however double stock HP raiting. Making 1 hp per cube is the bench mark and the realistic goal that most hotrodders shoot for(or should).

The BBC valve train is so heavy that it is best to try to make all of your power under 6000 rpm. This is where the larger cube BBC have the advantage. They can make more power down lower.

Don't forget that GM, back in the day, made close to 400HP from a 396. This was with 11-1cr and a solid flat tappet cam.

Don't get wrapped up in the HP wars. Build a solid engine that will run in the intended rpm range...tune it...and buy stock in your favorite tire manafactuer.

[Billla]

I agree overall with Bigjim. For the price you're looking at I would do a *very* straight rebuild with a few upgrades. Invest a bit in the valve job with a good port match and light porting, a good cam/intake combo (Edelbrock ain't the best, but for your price range and intended use, it ain't bad), headers and a carb overhaul. A CR in the 9.5 range (hyper pistons) should produce 425 - 450 very streetable HP for a total overhaul cost of around $2000.

[71Dragtruck]

Originally Posted by Billla

I agree overall with Bigjim. For the price you're looking at I would do a *very* straight rebuild with a few upgrades. Invest a bit in the valve job with a good port match and light porting, a good cam/intake combo (Edelbrock ain't the best, but for your price range and intended use, it ain't bad), headers and a carb overhaul. A CR in the 9.5 range (hyper pistons) should produce 425 - 450 very streetable HP for a total overhaul cost of around $2000.

I don't want to start a huge debate, but I would have to say it's not happening as easy as that. I have a 40 over 396, closed chamber oval port heads ( stock ) that were fully ported, undercut SS valves 2.19 and 1.88's. 10.1:1 forged pistons, a solid roller cam 246@50 and 622 lift, roller rockers and a ported RPM Air Gap intake. Plus all the other race goodies to make and handle power, I was thinking it was makeing the high side of 450-500, the shop that built my new motor figures more like 450hp. This was not classed as a street motor, unless you don't mind running a 3500 plus stall and 4.10 gears spinning it to 6500rpm. ( I ran a 4500 stall ) Making big horse power with small cubes is not that easy, if most people dynoed thier suposed 500hp engines they would likely cry, and the other half allready have from the bill after building a DEPENDABLE 500hp, I'm talking a bracket race motor that will run all season and then some.

Not trying to hurt feelings, but be very realistic on what you need, and what it will cost to get it. I went through the same thing, and after making calls to reputable shops found out horse power is not cheap, and if it is it will not last. Poor machineing and cheap parts fly apart when pushed to the limit. But what would I know, I've only spent about $20,000 on 2 motors, the first was my $8,000 396, that started out as a $4,000 to get a easy 500hp motor. That's not including all the changes I made over time either.

[tripleblack]

i want to see it when its done

[bigjimzlll]

Hey dragtruck....that post looks just like the ones I used to post. I know where your coming from. On a side note..I am tired of hearing all the racers on the net say that there pump gas 383's in a chevelle are running low 10's. I've said enuff...don't need to get into trouble.

[71Dragtruck]

Originally Posted by bigjimzlll

Hey dragtruck....that post looks just like the ones I used to post. I know where your coming from. On a side note..I am tired of hearing all the racers on the net say that there pump gas 383's in a chevelle are running low 10's. I've said enuff...don't need to get into trouble.

Well as long as I'm on the same page as a guy that also knows better I've also said enough. Pump gas ya, I pump in some 91 octane on top of my 1/2 tank of C12 all the time.

[john@thepier]

Go with aluminum heads and intake if you can swing the $ this will save you on the unsprung weight and give you enhanced handling. I work part time in an engine shop and have to sling both cast iron and aluminum heads all the time. Guess which I prefer.

[Billla]

Why not start a big debate? :-D I wonder if the confusion is FWHP vs RWHP...big difference. If you can't make ~ 1HP/CI FWHP for reasonable dollars then something doesn't seem right to me. I haven't built a 396 or 454, but I've built 4 427s and more 350s (never done a stroker than I can count and been able to get right in there without going on the extreme end of the universe.

I'm open for a call of B.S.

[cduster]

I'm with 71 Dragtruck on this one. If a 500 hp rebuild could be had for 600 bucks, everyone would have 500 horse. I put almost $600 in pistons in the motor I just did. I think if you price parts and machine work, then add extra for stuff you forgot about you would be suprised. This is just a guess, but looking at those heads, you are going to need some bigger valves put in. I believe that the heads are what makes or breaks an engine. If it can't suck it in, it can't put it out.

Dan

[bigjimzlll]

Originally Posted by Billla

Why not start a big debate? :-D I wonder if the confusion is FWHP vs RWHP...big difference. If you can't make ~ 1HP/CI FWHP for reasonable dollars then something doesn't seem right to me. I haven't built a 396 or 454, but I've built 4 427s and more 350s (never done a stroker than I can count and been able to get right in there without going on the extreme end of the universe.

I'm open for a call of B.S.

Billa, debates always seem to end up in pissin contest....I was told that to oppose the status quo (debate the normal opinion) is concidered trolling. I will not get caught up in a debate again.

[stllookn]

I must be doing something wrong...I can barely price a stock rebuild for a small block at $500...especially if it needs new pistons!

[junior219]

would cast pistons be ok for 400hp range? or would I be looking for some forged ones?? I am also dong the same with the 402 but I have new set of cast pistons. I understand that on some 402's the intake was restrictive, so if you went with a good aftermarket intake or a bb corvette intake would make the engine breathe better and exhaust too.

[Billla]

Originally Posted by bigjimzlll

Billa, debates always seem to end up in pissin contest....I was told that to oppose the status quo (debate the normal opinion) is concidered trolling. I will not get caught up in a debate again.

Ah, OK. I wasn't planning on that, but we'll agree to disagree. No offense intended.

[bigjimzlll]

none taken

[Billla]

Originally Posted by cduster

I'm with 71 Dragtruck on this one. If a 500 hp rebuild could be had for 600 bucks, everyone would have 500 horse. I put almost $600 in pistons in the motor I just did. I think if you price parts and machine work, then add extra for stuff you forgot about you would be suprised. This is just a guess, but looking at those heads, you are going to need some bigger valves put in. I believe that the heads are what makes or breaks an engine. If it can't suck it in, it can't put it out. Dan

To be clear, at no time did I suggest 500 HP for 600 bucks. I did suggest that a good rebuild with the right parts could be done for around 2K if he sticks with what he has and does as much of the work himself as possible. I agree that's probably a bit low...but I have built a "budget" 427 for < 3K (not including the engine with all "non-disposable" parts rebuildable) - and made over 440 *FWHP*. I do agree with sinking bigger valves - within reason - for a budget engine.

Heads are only one piece of the pie - mondo heads aren't going to do anything without the intake, carb, exhaust and cam to match. I see sucky engines all the time where a guy builds a stock lower end then puts expen$ive AFR heads on top and wonders why it won't go. This is one of those "while I'm in there discussions", and I agree that this is where rebuild prices go insane. You figure a really big cam...so you need better springs...those retainers look iffy...roller rockers are a good idea...those hot pushrods look like a good buy...REALLY big valves (not just what you can sink in a stock head)...

Then you're sitting on that 5K bill from Summit Racing and wondering what the hell happened

For $600, you'll get a J.C. Whitney rebuild if you're very lucky and maybe 275 or so FWHP.

I ran a quick Desktop Dyno on a stock 402, 9.5:1, mild street hyd. cam, mild port with valves, dual-plane with a 750 carb, small-tube headers and mufflers and got 417fwhp and 398 ft. lbs at 5500 RPM. Changing to rectangular ports with porting raised this to 452/432 but the curves weren't very nice lower down. And not to continue the debate to extremes, but there's about an 18% power loss between FWHP and RWHP on a stock auto...so. And finally before the debate starts, I'm clear on DD's limitations but it's a good tool for thinkin'

I think we're kind of in agreement - my 425 fwhp was a bit optimistic, but IMHO attainable (pretty close with a buget overhaul and ending up with about 375 or so at the rear wheels.

DD numbers (all 9.5:1 CR, all FWHP, all dual-plane/750):
Bone stock 402: 275hp@3500, 461tq@2000 rpm
"HP street" cam: 302hp@4000, 420tq@3500
Stage1-type port, biggest stock valves: 417hp@5500, 398tq@4000

And just for fun:
10:1, tunnel ram, 850, mondo heads, street/strip cam: 726@7000, 621@5000

<putting on my Nomex>

[COBRO]

70 ss/rs whats the casting # on those vortec heads your using?:::::::CB

[70rs/ss]

400 hp is as easy as picking the right parts, not $$$. If that was the case these ricers would be rocket ship for all the $$$ thrown at them.

[cduster]

Hey Billla, that wasnt directed at you, or anyone in particular. Those numbers came from post #7, and I just thought I would use them.

Dan