Jon Kaase SR71 Cylinder Heads

The AFR heads have different valve locations than the Ford SCJ and P-51. I took the easy way and cut the intake pockets in the block. Not pretty but it works great and I was able to run two different size engines this weekend, cutting pistons in both

Go back to the end of page 3 for the first picture

The lower pierce points are the AFR heads. The uppers are SR-71

Everything I ran used both an 1150 and then a big billet carb from Bob Book {BRE}
all tests used dyno headers from Hedman, 2 1/4". They were for big block Chevy and we put the SCJ/P-51 flanges on them

in all cases the carb was 10-15HP better

Switching the heads out from the 598 to the 521

Then the 521 on the dyno

The AFR 315 is the best they offer that I know of. I bought them from Motor State for the purpose of dyno testing.

We ran the heads on our 598 and 521 test engines and beat on them pretty hard to find the best timing and jetting.

It will be tomorrow before I can get all these dyno sheets organized and posted.

We ran both engines with the AFR 315's and manifold, the P-51's with the Trick Flow manifold, and the SR71's with the Trick Flow intake.

The AFR heads uses only their intake manifold, as the ports are rectangular but also the port spacing is way different than all the Ford SCJ style heads.
"
Ford heads are 4.8" from cyl 1 to 2, then 5.0" from 2 to 3, then 4.8" from 3 to 4 (no they are not evenly spaced)

AFR heads are 4.65" then 5.2", then 4.65"

In the one picture you can see the Fel-Pro 1231 gaskets on the intake surface. I lost the gaskets that came with the manifold! But you can see why the SCj intakes would have a huge mismatch.

All i can say is WOW!!!!!  ...

I will not get a wink of sleep till i see the results!!!..

jonkaase wrote: It will be tomorrow before I can get all these dyno sheets organized and posted.

We ran both engines with the AFR 315's and manifold, the P-51's with the Trick Flow manifold, and the SR71's with the Trick Flow intake.

The AFR heads uses only their intake manifold, as the ports are rectangular but also the port spacing is way different than all the Ford SCJ style  heads.
"
Ford heads are 4.8" from cyl 1 to 2, then 5.0" from 2 to 3, then 4.8" from 3 to 4  (no they are not evenly spaced)

AFR heads are 4.65" then 5.2", then 4.65"

Jon,can't wait for the dyno results thanks for all the pictures and information!!!

This is going to be Epic!!!!!       can't wait to see the results of what i believe will be an unbiased fair test.

After 4 revision's from the Original factory iron CJ head design under Jon's guidance..i think we have reached the peak of the Cobra Jet head Evolution..

Thanks to Jon,  I believe the SR-71 is going to be a Game Changer!...Especially for guys that really want to chase some serious HP without cutting up there classic old muscle car engine bays.

This is the 521. The AFR tests were this weekend, 60 degrees outside with .5 vapor pressure
the P-51 and SR-71 tests were early Sept, 95 degrees and .75 vapor pressure. The correction usually does well with these types of engines.

Here are the 598 tests. I will give the specs on the engines shortly

Lets start with the 521"
This engine came to us from Ford Motorsport in 1999 in the form of a CJ crate engine. We used it when testing the original SCJ heads that we sold to Ford. Then the P-51 testing followed by all the Boss 9 testing. It is the Finger in the Port engine that had all the videos done for my AETC presentation, as well as anything we have ever needed to run and punish. Then came all the SR-71 tests. It was a re-manufactured block when Ford supplied it. I would like to know the history of this block before Ford got it!
It is a 70 block with main studs and 8 lifter bushings. no fill. The bore is 4.390, (+.030")
Callies 4.3 crank, Lunati 6.8 rods, The cam is Comp 273-280, 109CL  .460" lobe, 1.73 Comp  rockers.
Pistons are Diamond shelf flat top with 1/16, 1/16, 3/16 rings. No gas ports. .020" deck clearance. It's all pretty tame stuff
Compression is 12.4

The 598.

It's a Ford Motorsport block, 4.600 bore. stock babbit cam bearings.
Lunati 4.500 crank, Lunati 6.7 rods. Diamond flat top pistons with side gas ports, .043, .043, 3MM rings
Compression is 14.9. It has .008" deck and .040 Cometic gasket. The cam is Comp, 285-298, 112CL, .471" lobe with 1.73 Comp rockers

Impressive, Mr. Kaase, very impressive.

Was any porting done to the P-51 or SR-71 heads?

They are as cast except we always hand grind right under the seats where the valve job ends and the aluminum starts.

The 1150 carb used on the 521 tests

Testing with the SR-71. When these heads are used on a 4.390 bore we have to reduce the exhaust valve size so it doesn't scrape the edge of the bore. The seat work on the head stays the same and the valve just  has a narrower seat. Here I back to backed the two different exhaust valve sizes to  make sure that there was no power loss with the smaller and narrower valve seat

Hose to Vacuum pump, and SR-71, 521" on dyno

What an Awesome 'Clash of the Titan's' .. I think it's safe to say the Bar has been set to almost Tower of Babel status by the SR-71 head..

And you can only imagine what a max effort 2x4 sheet metal, ported heads etc.. are going to do.. you gotta love it..

It was interesting that the AFR headed deal flat lined at 6400RPM till 7000rpm..

And the P51 did surprisingly well in the high RPM Range to give it's big brother a run for it's money..

dfree383 wrote:Thanks for Sharing Jon, Your work is outstanding.

I gotta agree with Dave .. I'm so glad your on our team..

I have run this HRE intake already

The plan is to see how much power we can make with mostly unported heads. So I have another cam coming with more ex duration and wider lobe center. It's 287-310, 115 CL, .483" lobes. Also raise the compression to 16+

So the goal here is to make 1200 HP with unported heads and stud rockers... Wish I had a 4.750 crank for it!