I'm building a 350 and was wondering if a set of 76cc 1.94/1.50 heads that have been ported and polished and have 1.5 full roller rockers installed would support roughly 350HP. The motor is all stock inside other than a Comp Cams 270H cam, oh it also a holley 600, edelbrock 2101 intake and 1 5/8 headers. Thanks.

What casting number are they?
There are some 76cc heads that are just plain junk.

Well I found out the heads I have are the shitty 462624 heads with 1.72 intake valves, so i'm hunting down a set with 1.94s. Any late 60s to late 70s car or truck would have half ass heads on it right?.

Why not just look into new heads?
World products Trick Flow etc.

SBC heads are pretty cheap anymore. When you add up the cost of rebuilding and porting 30 year old heads....its hardly worth it.

Ya true, I found a set on new aluminum 64cc 2.02s heads with 190CC runners on ebay for $650, so I might go that route instead.

Keep in mind that 99% of the new SBC aluminum heads on the market don't have the center exhaust port to heat the intake manifold.Their really intended for a dry manifold- port fuel injection. Carb may or may not work fine, it depends on a few things.

Keep in mind that 99% of the new SBC aluminum heads on the market don't have the center exhaust port to heat the intake manifold.Their really intended for a dry manifold- port fuel injection. Carb may or may not work fine, it depends on a few things.

That wont be an issue.
Unless your running a seventies early eighties factory choke.

The heat crossover passage was designed for choke pulloff...which was a spring that was heated as the engine warmed up by the exhaust gasses passing through the intake manifold from the center ports.

A most obsolete design.

vortec heads are a good solid head... they are more than capable of making 350hp and they're cheap. Dart iron eagles would be another good and not too expensive alternative.

That wont be an issue.
Unless your running a seventies early eighties factory choke.

The heat crossover passage was designed for choke pulloff...which was a spring that was heated as the engine warmed up by the exhaust gasses passing through the intake manifold from the center ports.

A most obsolete design.

The heat crossover is there to keep the manifold warm so the fuel doesn't condense too badly on the intake walls....It does make quite a difference. You may notice that many of the aftermarket carb manifolds don't have this and they are all rated at higher RPM and not low RPM. It's the low RPM range where this COULD be a problem...

Unless you have the shut off valve(forget the exact term as you just don't see them anymore) there is no way for the heat to get forched thru the manifold. In its origional design--the valve would close forcing exhaust gas's thru that chamber in the manifold--otherwise the only way heat is going to get into the chamber is by radient absorbtion. But you also rarely saw it on alum. manifolds--saw it alot on the older cast iron ones.... And this is carbed stuff not tbi stuff...

Unless you have the shut off valve(forget the exact term as you just don't see them anymore) there is no way for the heat to get forched thru the manifold. In its origional design--the valve would close forcing exhaust gas's thru that chamber in the manifold--otherwise the only way heat is going to get into the chamber is by radient absorbtion. But you also rarely saw it on alum. manifolds--saw it alot on the older cast iron ones.... And this is carbed stuff not tbi stuff...


The butterfly valve on the exhaust was there to help warm the manifold a bit faster. Once the exhaust warms up (OK the exhaust pushes it open but it still has resistance)the valve opens and exhaust still heats the manifold, just not as much exhaust goes through....Try sticking your finger on that port with the engine running and see. Better yet use a IR thermometer.
TBI needs the heated manifold too just like a carb. Their both wet manifolds.

TBI needs the heated manifold too just like a carb. Their both wet manifolds.

I disagree.
Heat to an intake manifold for performance purposes should always be kept to a minimum.

I disagree.
Heat to an intake manifold for performance purposes should always be kept to a minimum.

Exactly! It's not a performance issue, it's a drivability issue. Idle, low RPM off idle transitions is where you'll see the issues....Obviously anyone can build what they want, I'm going through this right now with a TBI.

Exactly! It's not a performance issue, it's a drivability issue. Idle, low RPM off idle transitions is where you'll see the issues....Obviously anyone can build what they want, I'm going through this right now with a TBI.


Prairepounder's main concern is performance....

No where did he ask for idle quality
So like I stated.
Its not an issue:flipoff2:

The butterfly valve on the exhaust was there to help warm the manifold a bit faster. Once the exhaust warms up (OK the exhaust pushes it open but it still has resistance)the valve opens and exhaust still heats the manifold, just not as much exhaust goes through....Try sticking your finger on that port with the engine running and see. Better yet use a IR thermometer.
TBI needs the heated manifold too just like a carb. Their both wet manifolds.

4.3 tbi doesn't have one. The 2.8 tbi doesn't have one and I don't ever recall seeing on on the 5.7 tbi--but its been a while since I have had one off..

All the carb cast iron manifolds from the 80's era has had them...

The vortec head is probably best bang for your buck at that power level. If you are stepping up to an aluminum head its kind of a waste if you are only looking for 350hp at the crank.

The vortec head is probably best bang for your buck at that power level. If you are stepping up to an aluminum head its kind of a waste if you are only looking for 350hp at the crank.

Ya, I was looking in to getting a set of vortecs. I found a set locally with a aluminum intake for $600. I also found a set of camel humps for $500. So I dont know which ones I wanna go with:confused:. Oh ya and the whole heated intake thing, ya its not a issue, i'm running a edelbrock and holley anyway.

4.3 tbi doesn't have one. The 2.8 tbi doesn't have one and I don't ever recall seeing on on the 5.7 tbi-...

Where do they get the exhaust for the EGR?

The Camel Humps are what....20 year old technology? IMO, go with the Vortec iron head for 350hp....Alum. as stated would be overkill for "only" 350hp.

Go with the vortec heads. Go to youtube and look up "Wes kean bounty hill". That is a dish piston 350 with a stock set of vortec heads. It has a comp. cams 274 hyd. cam and 1.6 roller rockers with a RPM Airgap intake. Thats it!

most of your camel hump style early model cylinder heads will not have accessory bracket mounting provisions on them. There are exceptions, of course.

The Vortec head flows better without modification, and has accessory provisions.

For $100 difference I'd go with the Vortec's. However, the so-called camel hump heads still have good flow ratings are are great for today's low rpm bottom end torque builds and would work great with TPI.
The 461, and 462 castings are the early ones without accessory holes because they came on short waterpump versions. They're plenty of 186, 187, and 292 castings that have accessory holes.
The Vortec's have 170cc intake runner volume, but require a special intake. The camel humps are 165cc and are really under-rated and over shadowed by today's aftermarket heads.
You can run too big of a head if you're not careful and actually lose on the low rpm intake charge.
Remember: Most street races are won in the first 60', and for most wheeling you want the power on the bottom~!

Well the Vortec heads I found are the 10239906 casting and I quote from Chevyhiperformance.com "be forewarned that some ¾- and 1-ton trucks came with Vortec heads equipped with a specially hardened exhaust seat that kills low- and mid-lift flow. Casting number 10239906 should be avoided.". So I'm a little worried about that, plus I heard that vortec heads can only handle about a 0.420 lift cam, is this true:confused:, so my Magnum 270H is too big (0.470 lift). I'm leaning towards the camel heads, which are the 186, because is a simple bolt and they are already machined with screw in studs and have guidleplates. One last thing I thought was which ever head I choose is far better than my current boat anchors (462624).

I'm leaning towards the camel heads, which are the 186, because is a simple bolt and they are already machined with screw in studs and have guidleplates. (462624).

FWIW not all 186 heads have screw in studs or guide plates and there are a couple different valve sizes to look for. Seats won't be hardened for unleaded gas unless someone had them swaped out.Their good heads, I just bought a set the other day.

FWIW not all 186 heads have screw in studs or guide plates and there are a couple different valve sizes to look for. Seats won't be hardened for unleaded gas unless someone had them swaped out.Their good heads, I just bought a set the other day.

The owner with the 186s has had screw in studs and guideplates already installed so that saves me from doing it and they have the 1.94 valves which is a plus.

The 186's with 1.94 valves are a great choice for a streetable application. You might want to verify that the springs are correct for your cam. probably a spring good to .550 lift, but if they're stronger you may consider new ones.

I think I'll change the springs reguardless. I was thinking of going with Comps #981-16 springs, which is what is recommended by them.

The 981-16 is what I use too! Keep in mind that the 186 is a 64cc chamber and will increase your compression too! As long as you've got flat tops you'll be fine, and even have more power because of it.
You should run a cast valve cover vs a stamped steel to minimize oil leakage.

I used the 906 casting heads and they worked great. I also used the comp. cams behive springs, locks and retainers. I had enough clearance for .550 lift with no machine work.

Well the Vortec heads I found are the 10239906 casting and I quote from Chevyhiperformance.com "be forewarned that some ¾- and 1-ton trucks came with Vortec heads equipped with a specially hardened exhaust seat that kills low- and mid-lift flow. Casting number 10239906 should be avoided.".

An update on that info from Gilbert Chevrolet's page (where I assume that info came form):

Please Note: The casting number myth debunked:
The myth is that there is a difference in the head performance produced by these two castings.
This myth was started by some Magazines that didn't do their homework before publishing their articles.
This is the truth the whole truth and nothing but the truth. So sayith the Grand Wizard GM and his Apprentice Wizard GILBERT CHEVROLET.
10239906 casting has one large single hump.
12558062 casting has 3 small humps.
If either of these two castings have not been altered by GM and the part number changed from 12558060 or altered by someone else (previous owner, etc.), the heads produced by either casting will be identical except for the external cosmetic difference. Both castings are used to make the 12558060 Vortec heads which are the true unaltered Vortec heads.
Heads from both castings come out of their cast IDENTICAL except for the minor cosmetic external differences!!!!!!!!

Hmm very interesting thanks for posting.

I believe you can go with any 5.7L Vortec casting you can find.....and not worry about it.....keep in mind though that either casting (same) will only safely accept about .460 lift....and I say safely because many lifts have been stated and it comes down to how much of a "safety" margin you're willing to put up with.....I am running .463 on the exh. without problems.

Edit: I've read anywhare from .460 to .480......of course measure 1st!!

just remember heads are part of building an engine, I put 1.94 int 1.5 exh intermediat smog heads on a 350 bored 30 over with a edelbrock performance pack intake and cam 750 carter carb and the cam was adjusted 2* advanced. that motor would lite up 38" tires with 4.11 gears and an sm465 trans starting out in 2nd (standing start not dumping the clutch) oh yeah and an msd 6al ignition controler (I think there under 200 bucks now, they are worth the money)

tourque turns tires, horse power beats ricers:)

It's the valveseats on the exhaust side that can be an issue on the high GVWR Vortec heads. People go round and round about it, but I've seen the two side by side. There is a difference. Will it matter? I don't know. The "bad" heads had a single angle valves on the exhaust side. It really shouldn't be an issue. The 062 heads were a single year only AFAIK ('98?).

SDPC sells all the stuff you need to run higher lift and it will only require minor machining to do. You end up using LT4 retainers with their "Z-28" springs with the dampers pulled out. The machine ship just needs to cut down the boss enough to clear the amount of lift you want to run. I had mine done for up to .525 lift with .060 clearance between the retainer and the seal, but could have easily gone to .550 if I wanted. Total cost shipped on the parts was right around $50 and it cost me another $50 to have the heads machined and even assembled for me. It's a cheap mod.