Best 396 heads?

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pdq67
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Re: Best 396 heads?

Post by pdq67 »

Are the -820 and -241 BBC heads the smog heads with the squared-off side that is inline with the intake valve by the exhaust valves? Almost quenchless...

One head here that is a good head, although a smaller head is the l-29 head that has the heart-shaped chambers with a point that probably would need to be trimmed back a bit and 100 cc chambers.

Although a real large oval head, the intake ports are down around 230 or so cc's vs regular large ovals being like 255 to above 260 cc's.

Might want to watch head gaskets here though?? For possible water leakage due to M IV, Gen V, and Gen VI deck cooling hole configurations is all...

I think Victor Reinz Gaskets has all this covered so please check..

http://www.hotrodders.com/forum/bbc-l29 ... 71714.html ----------

-------- "Victor Reinz has designed two Nitroseal® head gaskets to specifically allow for this conversion. The installation requires Victor Reinz part number 4918 be installed on the right cylinder bank to maintain proper coolant circulation, and part number 4923 to be installed on the left cylinder bank for the correct coolant flow. "

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Re: Best 396 heads?

Post by tt 383 »

Yes, almost looks like the exhaust was drilled in the wrong place.
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Re: Best 396 heads?

Post by Bob Hollinshead »

GOSFAST wrote:
Bob Hollinshead wrote:Thanks for the info everybody! Gary, what diameter valves work good? 2.10 intake?
Hi Bob, just about all these heads we set up (on these platforms) get a 2.125" SBC intake valve and a 1.810 BBM exhaust valve. These exhaust valves are from the "Indy" heads. If we are "chasing" a bit more HP we will go up to the 2.150" on the intakes and work the (intake) ports over a bit more!

We have on occasion stayed with the .375" stem OEM BBC 1.720" exhaust's but this is our 2nd choice. Takes a bit more port work to get the same numbers as the 1.810" Mopar valves.

With the LS-5 "820" heads ('71 Vettes) we are at 525 HP with the 100% stock-appearing builds with ALL the original components, Q-jet carb, stock exh manifolds, and 9.7:1 C.R. But these are also NOT 396" builds.

Thanks, Gary in N.Y.

P.S. I would add also we use ONLY the Ferrea valves on almost all our builds, occasionally will do Manley's but only when the Ferrea's aren't available. A while back we had a Cloyes BBC "Tru-Roller" literally explode up at about 7000, bent 14 of the 16 Ferrea valves, but not a single one broke!!

Thanks for the info, sounds like you have done a lot of testing on this and feel the stock HP 2.19 intake valve size must be a little too big for the closed chamber? Too much shrouding? I wonder how a 2.15 with 50* seat would do?
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Bob Hollinshead
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Re: Best 396 heads?

Post by Bob Hollinshead »

Alan Roehrich wrote:Depends on the piston. If you use a flat top, you can't even approach decent compression with any open chamber head. A closed chamber cast iron head yields good compression and good thermal efficiency. They're even good up to a 4.250" stroke 496.
I was thinking he may be able to get close to 10-1 compression on a 496 flattop build...
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Re: Best 396 heads?

Post by swampbuggy »

I was thinking that the 375 HP 396 which was offered in 1969 had rectangular ports, this head was probably too big IMHO for the application, does anybody know what Combustion chamber these heads had? I think this motor was 11 to 1 static compression? Thanks Mark.
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Re: Best 396 heads?

Post by pdq67 »

swampbuggy wrote:I was thinking that the 375 HP 396 which was offered in 1969 had rectangular ports, this head was probably too big IMHO for the application, does anybody know what Combustion chamber these heads had? I think this motor was 11 to 1 static compression? Thanks Mark.
Reading right along here...

"does anybody know what Combustion chamber these heads had?"

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Re: Best 396 heads?

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Closed
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Re: Best 396 heads?

Post by ClassicComp »

Closed chamber 106cc 396/375
results speak for themselves
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Re: Best 396 heads?

Post by Keith Morganstein »

Most of the time I buy in that flat top is better than a dome.

With the BBC engine, open chamber heads and a domed piston makes great power and torque. I think the chamber shape and increase in compression with a dome more than makes up for any possible loss in airflow because of the dome. Maybe the dome actually helps promote turbulence/burn in the chamber. You don't see evidence of a poor burn even with a large dome.

I also find more power in the BBC increasing compression with a dome VS milling the heads to get to the same comp ratio.

I use the open chamber (454)heads on the 396 (with the 2.19" int valve) . I use a dome piston and shift the head over with offset dowels. These engines perform very well!
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Re: Best 396 heads?

Post by vortecpro »

With the BBC engine, open chamber heads and a domed piston makes great power and torque. I think the chamber shape and increase in compression with a dome more than makes up for any possible loss in airflow because of the dome. Maybe the dome actually helps promote turbulence/burn in the chamber. You don't see evidence of a poor burn even with a large dome.

I also find more power in the BBC increasing compression with a dome VS milling the heads to get to the same comp ratio.

I use the open chamber (454)heads on the 396 (with the 2.19" int valve) . I use a dome piston and shift the head over with offset dowels. These engines perform very well!



I couldn't agree more!
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Re: Best 396 heads?

Post by Old School »

Keith Morganstein wrote:Most of the time I buy in that flat top is better than a dome.

With the BBC engine, open chamber heads and a domed piston makes great power and torque. I think the chamber shape and increase in compression with a dome more than makes up for any possible loss in airflow because of the dome. Maybe the dome actually helps promote turbulence/burn in the chamber. You don't see evidence of a poor burn even with a large dome.

I also find more power in the BBC increasing compression with a dome VS milling the heads to get to the same comp ratio.

I use the open chamber (454)heads on the 396 (with the 2.19" int valve) . I use a dome piston and shift the head over with offset dowels. These engines perform very well!
How much offset do you use on the dowel? Do you have to modify the head bolt holes in the head?
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Re: Best 396 heads?

Post by pdq67 »

Gary,

What are your thoughts on mildly worked over -206's, the way early, 96.7 to 98 cc true bathtub chambered heads?

I know they will shroud the valves some, but still due to the small chamber's, use flat-top pistons and .020" thick or so steel shim head gaskets here.

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Re: Best 396 heads?

Post by Keith Morganstein »

Old School wrote:
How much offset do you use on the dowel? Do you have to modify the head bolt holes in the head?
Depends on the "mock-up" but always at least the .030" and sometimes the .050". I set the head on parallels in my Bridgeport and plunge mill the head bolt holes. Pretty easy, only about 30 min a head.
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Re: Best 396 heads?

Post by gnicholson »

does the 2.19 in intake help that much for performance on a 396 even when you offset it?
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Re: Best 396 heads?

Post by vortecpro »

gnicholson wrote:does the 2.19 in intake help that much for performance on a 396 even when you offset it?
The offset is done on a NHRA stocker build (375 HP 396) the offset is done by moving the bore over. There is a power increase, I believe it to be around 10 HP.
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