HP/Torque guess on this 400 build?

[TwoFiftyShifter]

Wanted to get some estimates on what you think this 400 would produce, gonna try to build it over the winter. Just looking for a 350ish HP street engine.

1971 400 4-Bolt
Comp cams xtreme 262 cam
350 heads rebuilt
Keep the stock flat top pistons
edelbrock performer rpm intake, 750 holley
some good headers
msd distributor

[t&tkennels]

im thinking 300-325. just a guess.

[Marv D]

Somewhere between 200 and 300 would be my guess. The 262 is a horribly mild cam for any performance build, let along the big cubes of a 400. What is the 262,, something like 206° @ 0.050" ? Be very cautious that you don't build a octane hungry animal here. Most smogger era heads are 76cc chamber. 76cc, add 3or-so cc for valve reliefs in a flat top, 400 bore and stroke and your at a MINIMUM of 9.8:1 compression with a standard composit gasket. If there is any milling done to the block deck, or the heads to flatten them out, and your over 10:1 in a heartbeat. If it happens to be any of the 64cc heads your above 11:1 without a doubt. Iron heads, 11:1, a mild 262 cam is going to be a detonating SOB that you will have to run 110 octane fuel in (and I mean 110 motor octane as in a leaded race fuel ONLY). Either go back to the dished pistons and get compression down to high 8's or low 9:1 range, or get a BOATLOAD more cam, or step up to a good aluminum head. Aluminum heads pull heat out of the combustion chamber and allow you to run more compression with less octane than is acceptable for an iron chamber that holds heat. Not to mention the benifit of addef flow from most all aluminum heads. But to take advantage of a improved head your still going to want to use more cam than the little 262.

Just my 2cents

[TwoFiftyShifter]

Thanks, I'm new to this stuff. I'd like to not drop $600 on bare heads, I was thinking getting vortech heads, how will those work? Also what cam would you reccomend?

[Marv D]

Vortec heads are generally even smaller chambers. They would work GREAT if you would swap the flat tops for a set of 11c "D-dish" pistons.

If you want the muscle car sound you need to get 0.050" valve timing up around 220. if you want the agressive 'hot rod" sound more like 235-240, and unless you want to be buying race fuel,,, 250 and up is best reserved for 11 and 12:1 race motors.

A Vortec 400 is a kick butt motor! You can build for low end torque and pull the horns off the devil himself, or build for upper end HP and go around surprising the BBC pickups. It's just cam, induction and exhaust.

Check in to the RHS vortec heads. Much better design and castings than the stock crack prone castings. No,,, none of this is cheap. But remember rule #1,, only a rich man can aford to buy cheap parts, because only a rich man can afford to replace them again and again and again.

After 15 years of being in service the GM vortec castings are getting a reputation of cracks radiating from the exhaust seats, and cracks across the deck. This is really inherant to any light weight casting so popular,, there is going to be failures. But I'm hearing this more and more. Take that for whatever grains of salt you like.

What kind of power / ET are you looking for, and what kind of budget are you working with, and what are you wanting to do with the truck. I think the guys here can offer a LOT more if we are armed with some details.

[BossHogg69]

we love details - and don't forget the pics too!!

[TwoFiftyShifter]

I'll try to fill you in. I want a street truck. Pump Gas, no slicks, that kind of thing. Driveable. I'd like 350ish HP. I also want to build a lower RPM torque motor, for the street I would rather not have to rev past 5500 to make the full power. The truck itself is a short bed 64 GMC, should only weigh 3600 lbs with me in it, so it's not TOO heavy. My budget will probably grow once I get into the thing, but I'd like to spend just around $1200 for parts. If there are gains to be had for more money, I can do that. I'm not an engine builder, so basically what I'm looking for is a 350-400 HP small block 400 template. Thanks!

[Marv D]

My 66 backhalved with a Alston 4link kit, fiberglas front fenders, fiberglass hood and .065 aluminum covering all the places that 'used to be' wood.. weighs 3380 with my 190 pounds. 3600 may be a little optimistic, let's figure 3800+ to be safe.

Budget is tight at $1200. I mean we could sopend that in heads and have nothing left for anything else. I think Vortecs are out of the question here. The heads may be had for $300 to $400 but then you need a vortec specific intake (the Edelbrock item is nearly $400, add a set of centerbolt valve covers, and self guiding rockers. Vortec specific intake gaskets,, you will easily spend more on ' other required items' than you will the used GM Vortecs to begin with. And all those 'must have's apply to the aftermarket too.

So,, start looking on the net for a set of used 885 castings. There a large chamber head that will work decent up to 4500 in a mild 400 motor. Cam ought to be no more than the Comp XE274, with compression at 9.x (let's hope the block isn't going to need decking)
ANy performer or clone intake ought to work, and a nice little 750 Carter would make for a nice street truck.

Any other thoughts?????

[Super73]

Originally Posted by TwoFiftyShifter

I also want to build a lower RPM torque motor, for the street I would rather not have to rev past 5500 to make the full power.

The truck itself is a short bed 64 GMC, should only weigh 3600 lbs with me in it, so it's not TOO heavy.

400ci (4" bore 3.98" Stroke)
10-1 cr
Patriot performance 185cc Vortec heads (can use standard or Vortec intake and are $600 complete)
Edelbrock Performer RPM intake
750 Vacum carb
1 5/8" x 30" long headers
Production waterpump with flex fan
234/240 .560/.560 lift (Using a 1.5 rocker) 106 intake center 118 exhaust center making it a 112 lsa
Factoy windage and bearing tolerances


Engine Anaylyzer says it should make:
460ftlbs from 4000-4300rpm
427hp from 5300-5600rpm
(Best to shift roughly 200-300 past peak power, so figure 6k ish)




My 64 weighed in a 3,840 with me in it, and half tank of gas last time at the track. This is with an aluminum block and alum heads, drag lites, slicks, 205/75 front tire. My trans is heavy but it's going to be some work to get it that light. I'll b happy to b 3,540 next time I'm in mine with race seats and a full 1 piece glass front end.

[TwoFiftyShifter]

Hmm, I guess engine building does cost a lot, I'll have to save my money. What do you think it makes stock? 200HP?

[olblue81]

Originally Posted by Marv D

So,, start looking on the net for a set of used 885 castings.

Do you mean 882 castings?

[Marv D]

Originally Posted by olblue81

Do you mean 882 castings?

DOH, wish I could blame that on pfhat fingers,, but the 5 is a LONG ways from the 2 aint it LOL
Yes, the 333882 castings from mid-late 70's are what I was refering to. Thanks for catching that.