Jon Kaase SR71 Cylinder Heads

Dave De

Thanks for your input I've been watching your journey with great interest through the years.. as i am going down a similar path E85 588ci SR-71 build and another probably E85 or maybe race gas 598ci Boss9 i'm revamping.

I have a TFS Mafia for the SR-71 Build that i'll run.. personally haven't had much luck with ( ported Victors "by me" i did my best) holding power up top of the rpm on previous builds that i have dynoed (pumpgas engines). but i believe someone with a real knowledge of the Victor manifold could make it work better.

Interesting what you said about fuel distribution improvement with the Victor and SR-71 Heads you observed in your race track stuff..that's encouraging some of my friends have noticed weird plug readings lean or fat cylinders as well with Victors and the other low port CJ Head offerings.

Although the Mafia i believe is a good fit for the SR-71 Head..maybe the Air Boss for the people who have the room might be an improvement.. configured to work with either the SR-71 or the Boss9 head.

I know the head intake flange angles are different 45* to 52'5* and the port spacing is a little bit different but might be a worthy addition for either head if possible..

Or as Jon alluded too "if viable" a Cast Tunnel Ram for the SR-71 Head..(maybe possibly) to work with both heads would be Awesome!.. inmo i think a sheetmetal intake ruins the classic look of the Boss 9. I'd personally rather run a highly modified old cast Weiand Tunnel Ram if it could be made to work..

Did some mucking around today with the SR-71 heads.. a different perspective Looking down a 4.562 Bore..

Good job.

It appears that the exh. side of the chamber is wider that the 4.562" bore. Is that the case?

Lem Evans wrote:It appears that the exh. side of the chamber is wider that the 4.562" bore. Is that the case?

Yes that is correct there is a slight over hang of the bore into the exh side of the chamber maybe about .020" or 0.30" or so.. i'd say a 4.600" bore would have little or no overhang into the chamber.. I did put the dowels in the deck to make sure the head was square.  

when i get a chance out of curiosity i'll do a dummy up with cam, lifters, rocker etc..and see how much exhaust valve clearance there is from the bore when the valve is open..

nascar429 wrote:

Lem Evans wrote:It appears that the exh. side of the chamber is wider that the 4.562" bore. Is that the case?

Yes that is correct there is a slight over hang of the bore into the exh side of the chamber maybe about .020" or 0.30" or so.. i'd say a 4.600" bore would have little or no overhang into the chamber.. I did put the dowels in the deck to make sure the head was square.  

when i get a chance out of curiosity i'll do a dummy up with cam, lifters, rocker etc..and see how much exhaust valve clearance there is from the bore when the valve is open..

That being the case, a guy needs to get a head gasket that fits the chamber rather than the bore. The TFS A460 heads are the same way in that regard.

Lem Evans wrote:

nascar429 wrote:

Lem Evans wrote:It appears that the exh. side of the chamber is wider that the 4.562" bore. Is that the case?

Yes that is correct there is a slight over hang of the bore into the exh side of the chamber maybe about .020" or 0.30" or so.. i'd say a 4.600" bore would have little or no overhang into the chamber.. I did put the dowels in the deck to make sure the head was square.  

when i get a chance out of curiosity i'll do a dummy up with cam, lifters, rocker etc..and see how much exhaust valve clearance there is from the bore when the valve is open..

That being the case, a guy needs to get a head gasket that fits the chamber rather than the bore. The TFS A460 heads are the same way in that regard.

Do you think .030" offset dowel holes would be enough for a 4.390" bore using the normal 4.500" bore gaskets...?

That being the case, a guy needs to get a head gasket that fits the chamber rather than the bore. The TFS A460 heads are the same way in that regard. [/quote]

Have to admit this is beyond my scope of knowledge up to this point but i'm learning..if you ran a 4.500 head gasket on say a 4.390 to 4.440 bore would the gasket hanging into the combustion chamber possibly burn up the the head gasket or create a hot spot?..

You'll need a gasket bigger than the 4.562" bore to keep the fire ring out of the chamber. Put the dowels in the head and lay the gasket on the head to make sure any gasket is not in the chamber.

Lem Evans wrote:You'll need a gasket bigger than the 4.562" bore to keep the fire ring out of the chamber. Put the dowels in the head and lay the gasket on the head to make sure any gasket is not in the chamber.

Thanks

That was my plan to run either a 1028 head gasket or a 1099 gasket depending on where the piston ends up deck height wise.

I'll post up 2 pictures of a gasket on a head with dowels the first with a standard Felpro 4.500 bore gasket.

And the second with a 1099 Felpro 4.660 bore gasket.

My question for the guys that want to run the SR-71 head on a smaller 4.390 to 4.440 bore..to you think it would be preferable to run the bigger head gasket 4.660 etc.. on the (smaller bore sizes) to keep the head gasket out of the chamber ?

My Bad I got it wrong guys with the 4.500 bore head gasket on the head with dowels..the head gasket overhangs into the chamber more like .055" .060".

The 4.50" bore head gasket will not work with those chambers. There will be no clamping force on that fire ring.
Perhaps Kaase has a different CNC combustion chamber for small bore blocks?

That combustion chamber will need the 4.66 head gasket.

Cheers

I had some edelbrock rpm small block ford heads with the same problem. I just used a cometic with out the fire ring

We stock the Cometic head gaskets with a 4.640" bore if you go with a MLS style gasket. .040", 045" and .051" thick.

"My question for the guys that want to run the SR-71 head on a smaller 4.390 to 4.440 bore..to you think it would be preferable to run the bigger head gasket 4.660 etc.. on the (smaller bore sizes) to keep the head gasket out of the chamber ?"

I would run a bigger bore gasket on the small bore stuff. The 1018 felpro units that I have measured are more like 4.480" rather than the 4.50" that is published.

Why even talk about using a junk Felpro Head gasket with a nice set of heads like this? Use Cometic and get on with it!

I've never had any problems with felpro head gaskets but felpro intake gaskets that's a different story!!

Lem Evans wrote:
"My question for the guys that want to run the SR-71 head on a smaller 4.390 to 4.440 bore..to you think it would be preferable to run the bigger head gasket 4.660 etc.. on the (smaller bore sizes) to keep the head gasket out of the chamber ?"

I would run a bigger bore gasket on the small bore stuff. The 1018 felpro units that I have measured are more like 4.480" rather than the 4.50" that is published.

If a “small” bore head gasket is in the chamber then wouldn’t the cylinder wall be in the chamber on a “small” bore engine? So what difference would it make on performance? Other than burning the gasket.

stanger68 wrote:

Lem Evans wrote:
"My question for the guys that want to run the SR-71 head on a smaller 4.390 to 4.440 bore..to you think it would be preferable to run the bigger head gasket 4.660 etc.. on the (smaller bore sizes) to keep the head gasket out of the chamber ?"

I would run a bigger bore gasket on the small bore stuff. The 1018 felpro units that I have measured are more like 4.480" rather than the 4.50" that is published.

If a “small” bore head gasket is in the chamber then wouldn’t the cylinder wall be in the chamber on a “small” bore engine? So what difference would it make on performance? Other than burning the gasket.

Failing the gasket is the biggest issue.

I know I'm late to the party on this thread, but with the poor flow of the heads in stock form(not yours Jon, Ford's), why not increase the exhaust valve diameter to 1.88"?

mitch huested wrote:I know I'm late to the party on this thread, but with the poor flow of the heads in stock form(not yours Jon, Ford's), why not increase the exhaust valve diameter to 1.88"?

The simple reasoning is that increasing the intake valve size does more good than increasing the exhaust valve size.

I agree that the increase in intake valve helps, but it still needs to evacuate the cumbustion gases and the exhaust ports on standard heads are pretty bad. By increasing the exhaust valve with a bit of porting, one can evacuate the combustion gases with less resistance.

Ask Jon Kaase where he spends most of his time.
Intake or exhaust. Hint…it ain’t the exhaust.

mitch huested wrote:I agree that the increase in intake valve helps, but it still needs to evacuate the cumbustion gases and the exhaust ports on standard heads are pretty bad. By increasing the exhaust valve with a bit of porting, one can evacuate the combustion gases with less resistance.

Exhaust is way different than the intake charge, it’s super hot and under real pressure, a big port and valve isn’t needed.

Just curious how much more power the SR71's make over the P51's and how much less they make compared to the Kaase Boss 429 Heads?