Dyno tomorrow

Finally, after several years delay and waiting! Going to dyno the "re-tuned" 552. Different heads (SR71), different cam, updated carburetor, BBC header adapters for better headers. Last time made around 910 hp. Excited to finally hear run again!

what heads did you run before?

I was using (still have on shelf) p51 heads, main problem was the dyno headers we had to use were very small for the engine size and rpm.

well good luck on the dyno pulls.i am very intrested as i have a 598 with ported p51 and would like to see if the sr71s make a big jump in hp.i consider them as well,but have to much other stuff to do.910 with a 552 is nothing to sneeze at for sure.what cam and compression?
street or race engine?

Thanks! Has a 1969 C9 block, 14:1 compression, new cam is around 282 duration and .830 lift. The 1150 Holley was sent out to get updated boosters and metering blocks. 112 race fuel. Mafia intake and tapered and open spacers. Header adapters from Charlie Evans. Going to try 2.25 headers with o2 sensors on dyno to get tuned. Had to switch to a MSD dizzy to clear the sr71 1" spacer for intake manifold. I enlarged the valve reliefs a bit for the new intake valve size. Lots of baffles in a deeper stock oil pan and aluminum pump.

2 1/4 headers are good,but be sure to use 18" collector extensions.they are always worth hp and torque.i think it should make 1050 or more depening how high you rev it!

We are leaving at 6am to drive to the place in Twin Falls Idaho. I do not have a vacuum pump on it, and regular 1/16 rings. Will be interesting to see how it goes. Using 15w-50 gibbs oil. We hit about 7200 rpm last time in 2019.

Got results back this afternoon. Good news, made much better overall numbers. Bad news, did not peak as high hp as we anticipated. Area under curve was better everywhere, did not flatline like last time. Peak hp was 6900 rpm. Will try and get sheet posted. Overall happy to have it running again, sounded great.

Where the P-51's ported?

What size exhaust valves in the SR-71's?

Nice numbers. It's too bad Kaase did not make a nice tunnel ram for those heads like the A460 heads have.

The p51 heads were ported with the 2.30" intake valve size. Exhaust valve on these sr71 is the 1.70" if I remember correctly. The dyno owner was commenting on the plenum size of intake manifold, showed me a sniper BBC intake that was much larger plenum size. I really don't know if that means anything.

I would think more intake and/or a larger carburetor would help. Run it by Charlie, see what he allows. Also a 4.5/4.6" inch bore with the big exhaust valve surely would.

My question is will it Hook Up what you have now?

Did you see this build?

https://www.yellowbullet.com/threads/572-bbf-with-sr-71-heads.2641389/

Air Boss Next to Mafia Port.

https://www.yellowbullet.com/attachments/nw6n3rr-jpg.145449/

I like yours better, the above one is too much pain and not enough gain to me. It's the Big V type intake and 1,300 cfm, more cubes, bigger cam and more compression, not to mention bore size and a vacuum pump.

so if the p51 heads were ported, i see that helped.did you changed cam? looks like it went well on the dyno.

^ He said he did in post #5.

It's kind of interesting comparing the numbers to Kaase's 521. It made a little more torque and about the same HP at 200 more RPM than yours. In the pictures in the Kaase thread he says the vacuum pump was used on the 521, and you can see a line from the valve cover, but, only wrote it on the 598 dyno sheets. It's not real clear in the write up on that?

https://www.yellowbullet.com/attachments/screenshot_2018-11-05-23-27-54-jpg.145065/

He also claimed the BooK carburetor was 10-15HP better then the 1150 but, not real clear on specific's or back to back dyno sheets.

For Kaase's 598 SR-71 to hang with Keith's 618 A460 Interceptor 7 years later and the cost difference is pretty wild.

https://www.429-460.com/t16558-keith-fulp-s-618-a-head-interceptor



Did you try an open spacer with a 4 hole shaped spacer on top of it?

I suspect that the 2-3/8" headers could have hurt the tq a little.

We did have a Jomar tapered spacer, with an open spacer below that. No stud girdle (yet), using blp 114 jets with the 112 supreme fuel. These things sound awesome at 7000 rpm with open headers

Engine is going back in my '69 Mach 1 I've had since December 1982.

69 mustang nice! i have 3.

Horsepower peak will probably not be at much higher RPM, if ever, with 1/16" rings at almost 90 ft.per second mean piston speed.

They will begin to lose ring seal around that RPM point.

Very interesting about the rings, did not know that. Especially when using stock block like mine vs Motorsport block that is heavier casting.

Nice numbers on that package. Just like you my 69 Mustang had worked over P-51's that was changed to SR's. I had minimal gains as well with maybe 5/100ths in the 1/4 mile. Now we can improve our SR's if we want more.

glenevans wrote:Very interesting about the rings, did not know that. Especially when using stock block like mine vs Motorsport block that is heavier casting.

The block does not make much difference at all there except for some bore distortion. The stroke is what controls mean piston speed and ring flutter is mostly controlled by that and the weight of that ring; so bore size does matter a little.

I thank all those who help and give advice/ experience on this site. Pretty cool a guy can build a 900 plus hp motor in a garage these days. Thanks again!