Factory cast Z11 heads flow and horse power vs ported?

[1964SuperStocker]

Just wondering. I know the McQuillen Z12 heads will top 900+hp with 600ci. Just wondering about the Factory Z11 cast iron heads. What was the flow numbers on those from the factory and what can be had with some porting? I was thinking I read 400cfm for factory cast or slightly better but not sure now.

 

[BSL409]

I was thinking I read 400cfm for factory cast or slightly better but not sure now. you would be lucky at 360 ish

 

[Blk61409]

Just wondering. I know the McQuillen Z12 heads will stop 900hp with 600ci. Just wondering about the Factory Z11 cast iron heads. What was the flow numbers on those from the factory and what can be had with some porting? I was thinking I read 400cfm for factory cast or slightly better but not sure now.

Here is an aluminum 509 cu in block with a pair of original 63 Z-11 cast iron heads and intake. A pair of Demon carbs. Built by Lamar and Rob Walden.

755hp, 618 ft lbs of torque. Certainly can’t attribute the heads to all the HP, but they certainly generated a considerably portion.

 

[63 dream'n]

I believe I had read that they were very comparable to big block rectangular port heads………

 

[benchseat4speed]

Thats incredible. 755hp with parts designed in 1962, and that thing will fit under a flat hood. Bet they aren't spinning it to 7 grand to get that number either I do believe that's the first time I've ever seen original Z stuff on a dyno. Would like to see the car that's going in. Dig that blank water pump!

 

[La Hot Rods]

Think Tony said the stroked 409 with his worked over 690 heads made 750 HP

 

[Phil Reed]

Probably!!!!!!!!

 

[FS560]

Is the 755 hp “corrected”?

 

[Phalen409]

Stroker block, stock heads, intake and vintage carbs, hyd roller, by Carl McQuillen. 9.6 to 1 compression

 

[benchseat4speed]

Man that's impressive too! You could drive that thing every day on 91 and probably still get 15mpg plus on the highway. Z11 heads are incredible pieces. Chevrolet had some fantastic engineers in that era.

Pinnacle of W development and...GM scrapped it

 

[FS560]

A quote from an article by Doug Marion ln Chevy Rumble.
"Even then they knew”.

 

[region rat]

Think Tony said the stroked 409 with his worked over 690 heads made 750 HP

Tony flowed stock Z-11 heads and I think he said they flowed about 320. After porting, 355. If everything matched 750 should be possible. 1 cfm can give you the ability to make 2.125 hp.

 

[region rat]

Using the moroso magic slide rule my old stock stroke with Z-11 top bone stock made 520 ish
3900# 11.30/120. Heads would probably respond better on a larger motor.

 

[region rat]

Stroker block, stock heads, intake and vintage carbs, hyd roller, by Carl McQuillen. 9.6 to 1 compression
View attachment 118995View attachment 118996View attachment 118997View attachment 118998

those are likely real numbers.

 

[region rat]

I was told stock Z-11 flowed 320-330. Tony Schafer ported his brother's and got them to 355. I never heard of anyone getting that much.
I've had at least 10 shops port mine and get to 350. Best was 373. Nick Smithberg. My raised port can flow even more.