NOT ANOTHER CAM THREAD!!

[PRHeads]

I’d look over the combo in post #14, and see how that might fit in with your goals.
Almost 400hp(and as pointed out, it would be 400+ with 2 simple changes).

The overall gist of my first post was to focus on how the car will be used, and all the other items that the motor has to get along with, like exhaust manifolds, a low stall speed, power brakes, etc....... and select components based on those criteria instead of an arbitrary hp number.
Put together a nice package........ and the hp just “is what it is”.

 

[Challenger340]

I just had a 383 dynoed today I built for a friend. Forged flat tops about 10 thou down, with 906 heads came out to 8.8 to 1 with fel pro gaskets. Heads have 2.14, 1.81 stainless valves, I touched up the valve pockets a bit with a die grinder. It's balanced, has a windage tray, stock 1970 intake, 750 quick fuel carb. Cam is a Comp Xe268. I recurved the mopar performance distributor too. With headers it made 382hp and 421 ft lbs torque. 20 thou Steel head gaskets and a better intake would get it close to 400 hp.

Yeah it ain't 'sexy' to say so.....
especially with so many people these days seeming to preach what I call "re-invention of the wheel" with smaller Cam Grinds and different manufacturers ?
So all I'm gonna say is we've seen very similar results on the Dyno..... and we've been very happy with both the Comp XE268H and CROWER 271HPD
with,
possibly the Crower offering slightly better vacuum for P/Brakes being ground on the 112 LSA for the 383
and,
the XE268H offering slightly better few HP midrange, still OK for P/Brakes.

 

[Challenger340]

I’d look over the combo in post #14, and see how that might fit in with your goals.
Almost 400hp(and as pointed out, it would be 400+ with 2 simple changes).

The overall gist of my first post was to focus on how the car will be used, and all the other items that the motor has to get along with, like exhaust manifolds, a low stall speed, power brakes, etc....... and select components based on those criteria instead of an arbitrary hp number.
Put together a nice package........ and the hp just “is what it is”.

As always Dwayne... you about nailed it, GREAT advice !

BTW, I really like MABEL in the Video !

 

[Red63440]

Thanks, I’m pretty happy with her.

 

[Red63440]

I just had a 383 dynoed today I built for a friend. Forged flat tops about 10 thou down, with 906 heads came out to 8.8 to 1 with fel pro gaskets. Heads have 2.14, 1.81 stainless valves, I touched up the valve pockets a bit with a die grinder. It's balanced, has a windage tray, stock 1970 intake, 750 quick fuel carb. Cam is a Comp Xe268. I recurved the mopar performance distributor too. With headers it made 382hp and 421 ft lbs torque. 20 thou Steel head gaskets and a better intake would get it close to 400 hp.

What was the CC of the chambers on the 906 heads and are the 906 better than the 452’s?

 

[Red63440]

So with the flat tops that are in the 70 383 am I after a smaller chamber for better compression or am I after a larger chamber?

 

[PRHeads]

Ideally, you’d want a closed chamber head that flows well, and the piston to head clearance between .040-.060, and have that work out to give you the CR you’re after.

For example....... flat tops at zero deck, 80cc Stealth heads, 1009 gasket ........ puts it right at 9.7cr, with good flow and great quench.

Or, pistons down the hole say .020, steel shim gasket, 516’s or 915’s milled to 80cc....... same quench, same CR.

Swapping to an 88cc open chamber head drops the CR to 9.0, and eliminates any quench........ so that’s kind of a lose/lose.

 

[Red63440]

Can I use an open chamber 78cc 906 head with a steel shim head gasket with the bigger valves? What would that give me?

 

[PRHeads]

You have to know the piston deck clearance to calculate the actual CR.

 

[Red63440]

Its .018 in the hole.....

 

[PRHeads]

Looks like you’d end up right about 9.9:1 ....... probably with a quench distance of around .090”(no quench).

 

[Red63440]

So if I used it with a .040 head gasket I would be at a good place.

 

[furious70]

Your cr would be where you want, but no quench

 

[PRHeads]

Your cr would be where you want, but no quench

This is true....... but is pretty much the case with any 383 being run with open chamber heads........ that isn’t using custom quench dome pistons.

 

[toolmanmike]

Meet Mabel...

Beauty! You are a lucky guy.

 

[Red63440]

Thanks Mike

 

[Red63440]

This is true....... but is pretty much the case with any 383 being run with open chamber heads........ that isn’t using custom quench dome pistons.

Wait, weren’t all 1970 factory 383’s made with flat tops with open chamber heads, where was the concern for quench then?

 

[PRHeads]

You mean back when there was 98 octane fuel available everywhere?

My point was, just about every 383 built with open chamber heads has no quench.
Some of those combos will have a problem with ping as a result...... some won’t.

 

[Red63440]

Ok, understood...

 

[Dennis H]

Comp 275HL.