BBC oem cylinder head debate

[houser45]

Shop debate. Expert bbc guys give your imput.

Three engine scenarios. 1. low rpm truck or stockish street engine under 5000 rpm. 2. street high performance every day driver build.1500-6000 rpm 3. street/strip 7000 rpm engine

All 396 inch engines with hydraulic camshafts and 10.5 to 1 compression for pump fuel. Same cams, same compression ratio Oval port heads. Early closed chamber vs. semi closed 781 type heads. Who makes more horsepower and torque in each of the three combinations?

[PackardV8]

Then, the question arises, who builds a 396" today? Can't remember the last one we did.

[F-BIRD'88]

Agree 100% Find a 454 to build for either both purposes.
The open chamber bbc heads work better .
Sell/give the 396 to someone who is restoring or does not know any better.

[PackardV8]

Agree 100% Find a 454 to build for either both purposes.
The open chamber bbc heads work better .
Sell/give the 396 to someone who is restoring or does not know any better.

Since the Chicom forged strokers became good enough and cheap enough, I can't remember the last 454".

[Tom68]

Shop debate. Expert bbc guys give your imput.

Three engine scenarios. 1. low rpm truck or stockish street engine under 5000 rpm. 2. street high performance every day driver build.1500-6000 rpm 3. street/strip 7000 rpm engine

All 396 inch engines with hydraulic camshafts and 10.5 to 1 compression for pump fuel. Same cams, same compression ratio Oval port heads. Early closed chamber vs. semi closed 781 type heads. Who makes more horsepower and torque in each of the three combinations?

The biggest head makes the most torque and horsepower.

The smallest head makes the least peak numbers, but it makes more earlier, then fall on its ass.

[mag2555]

Unless your building a motor that has a intended rpm range above 8K and also with a narrow 1500 rpm wide power band then it's not helpful as has been posted to run the biggest port volume head and Intake by any means, and this failed type of logic has been proven so over and over, and especially so with only 396 cid!

What you want to nail down in all three cases is the rpm range your willing to live with and then build for the highest average torque and hp numbers within a 2500 to 3000 rpm wide power band.

Even in your number 3 case it's still the average numbers that contribute the most to getting a vehicle to accelerate the mass that it has.

[1980RS]

That's an easy one, the open chamber will make more power over the closed chamber heads in most applications. I did this swap years ago when swapped out a set of 290 closed for a set of 781 both sets with stock valve sizes. Car was noticeably quicker and faster with the 781 open heads even with less compression. Same deal on my peanut port head test I did in 2019, the 215's were way slower than my 360 PP heads with a lot less compression. Go with the 781's and enjoy more power on less octane fuel.

[vortecpro]

I did a 396 a few months back, it was .040 over, 10.5 comp, I used a 802 casting GM oval port closed chamber head, 2.190 intake, 1.780 exhaust, ported. The cam was a solid flat tappet 264 @ .050 on a 108. Performer RPM air gap intake. The oil pan was worked over, it made 551 HP and I believe around 512 TQ. I did a L78 375 HP 396 with some work before the oval port build, it had the factory cam and was done @ 471 HP, the cam was the cork. Hope this helps.

[1980RS]

I did a 396 a few months back, it was .040 over, 10.5 comp, I used a 802 casting GM oval port closed chamber head, 2.190 intake, 1.780 exhaust, ported. The cam was a solid flat tappet 264 @ .050 on a 108. Performer RPM air gap intake. The oil pan was worked over, it made 551 HP and I believe around 512 TQ. I did a L78 375 HP 396 with some work before the oval port build, it had the factory cam and was done @ 471 HP, the cam was the cork. Hope this helps.

Mark what do you think the power difference would be with the 802's you did vs a set of 781's ported with the big valves. For sure that factory 375hp cam was a pooch put in by GM back then. My milder Comp 282-S was a little more lift, less duration and LCA and the 375hp engine I had picked up a lot from that cam swap.

[vortecpro]

I'm not sure. A 840 rectangle port head doesn't even start flowing until after .500 lift, after that it gets going.

[Walter R. Malik]

Shop debate. Expert bbc guys give your imput.

Three engine scenarios. 1. low rpm truck or stockish street engine under 5000 rpm. 2. street high performance every day driver build.1500-6000 rpm 3. street/strip 7000 rpm engine

All 396 inch engines with hydraulic camshafts and 10.5 to 1 compression for pump fuel. Same cams, same compression ratio Oval port heads. Early closed chamber vs. semi closed 781 type heads. Who makes more horsepower and torque in each of the three combinations?

Personally, I would go with the 049 heads using larger intake valves.

[pamotorman]

OC heads fitted on a closed chamber race engine made 29 more HP even with less CR. this test was done at gulf research in pittsburgh

[pamotorman]

OC cast iron oval port heads were available on 1974 454 1/2 ton PU engines

[In-Tech]

OC heads fitted on a closed chamber race engine made 29 more HP even with less CR. this test was done at gulf research in pittsburgh

OC cast iron oval port heads were available on 1974 454 1/2 ton PU engines

1973 454 even Isn't pittsburgh where you are from? You probably were involved in that test

[Walter R. Malik]

Shop debate. Expert bbc guys give your imput.

Three engine scenarios. 1. low rpm truck or stockish street engine under 5000 rpm. 2. street high performance every day driver build.1500-6000 rpm 3. street/strip 7000 rpm engine

All 396 inch engines with hydraulic camshafts and 10.5 to 1 compression for pump fuel. Same cams, same compression ratio Oval port heads. Early closed chamber vs. semi closed 781 type heads. Who makes more horsepower and torque in each of the three combinations?

Personally, I would go with the 049 heads using larger intake valves.

We used the 820 heads with the stock size valves, (which are oval port with kind-of a half open chamber, also having a large relief in the quench around the exhaust valve), in many 402 size engines with great success however, the 454 size engines preferred the 049's with a 2.19 diam. intake valve.

These engines road tested were 9 to 9.5 to 1 compression ratio street engines.