My motor dynoed 982 hp at 7600 rpm . We advanced the cam and picked up 5 hp in the midrange, lost it at 7600. Dyno pic is of after advancing cam to 108 from 110.
549 cubic inch, 4.315 stroke, 4.50 bore. 15.5 compression. Rods are 7.10 long best timing is 34.5 degrees. Torque maxed out at lowest part of pulls, 5600 rpm. I am considering going from the current converter which stalls at 6400 rpm, to a newer converter by Coan, which i understand could be set up with a higher stall, yet be very efficient with excellent lockup on top . Current headers are two step, 2 1/8 to 2 1/4 , 14.5 inch length in both steps. I have a merge collecter with 3.5 choke, 4 inch exit. Would there be any benefit to shortening the larger step? If they can build a converter to stall 6800 and decent lockup by 7400 i am thinking maybe 7000 rpm should be the target for best scavenging?
Best times were 8.50s at 157 mph, 2930 lbs, da maybe 2200? I run methanol.

from what I know about it, run your engine through pipemax program. And I think it depends on how much you want to spend to gain just a few HP. As much power as your engine is making, I would think tuning the chassis will gain you more ET than picking at a few HP with headers. In my drag racing experience it is amazing how much a converter that really matches an engine can give you, as well as a chassis that uses all the HP provided. And I think about how many times I built an engine with 100 more HP and then chased the converter and chassis to really make use of the added HP.

Agree if you buy anything and the converter is as 'off' as you are saying, that's what I'd do. Just the same there's plenty of 8.3s with your MPH and tuning IMO. Based on how I read charts your MPH is pretty reflective of your power especially considering you haven't wrung things out.

549 cid Pontiac???? How much is that corn converter Greg. I’m thinking of changing also.

I called Coan, got schooled a bit. According to what i was told, my performance isn't that far off, and a new 8 inch would be built to stall at the same 6400 i have now. My slip is 6.5 percent, acceptable according to Coan, and gains from a new converter would be at best only a few hundreths, and a little increase in mph? The cost of a converter now is about $1700. So if you are chasing every last hundreth, it might be worth trying if your current unit isn't well matched to your power curve.

My pipemax program refuses to work? Maybe my license is corrupted?

Gains can be realized easily by adjusting the collector length. An air/pressure chamber, which can be just a very small(relative) no guts muffler, can increase TQ/HP. Also, tuning the length of the collector itself has worth. As per the old days, adding a long collector and running a colored crayon down the length can give you a quick guideline. Where the wax stopped melting, that's your initial length and move back towards the motor in graduations of 1".

There is a BIG difference between 8.50 and 8.30. That would take over 50hp at the current weight.
Doug

I agree. I think the mph i have run of 157.5 at 2200 da is decent, and i am guessing leaving so soft is costing me maybe .04 in 60 ft? 1.224 best, launching at 4000 rpm part throttle on a CO2 throttle controller. But it leaves so consistant i may stay there, as i am too lite on front weight at about 50 %. It leaves pretty flat and doesn't pull the front wheels off the ground till about two feet out, when at 5,000 launch it would hit the bars and unload the back tires. So my guess is i may see a high 8.4? at some point.

160 MPH is plenty adequate for 8.3x...doesn't your sig and previous posts say you went 160? Was that as efficient of a pass as your chassis has already made?

157.5 is enough to tun a high .30, wont be easy, but a good clean efficient pass its plenty. It is certainly plenty to go a low low low .40.

We were worried about the headers we had already for our 493 when dad built the 588. Chuck & Pete were pretty skeptical also as they had a real nice set of dyno headers. As you can see in the dyno sheets, the difference was fairly marginal at peak difference (15HP & 12 ft-lbs tq). The dyno sheet with 1033HP @ 7200 was their dyno headers,the 1028HP was our headers.I can't see that making a huge difference converter wise. Now the side exits pictured in the next post were never on a dyno, or this 588 yet, but absolutely killed the low end of the 493".

Side exits that lost almost a full tenth to the 60'.

A combo has got to be pretty scienced out to go a .30 below 160. Even tracking yhe NMCA All Motor class. Not many that are that slow can get to that ET at 157-160. Obviously most are quicker. I would consder that those cars to have way more money, tuning, and parts thrown at them then a good home built one man band car.
Doug

Plenty have said, I'm a dumb monkey including me. I too have a home-built car with plenty of inefficiencies but I plan to do about the same. I believe you'll get there Greg!

Take a look at SS And Comp for your answer. We have been 7.95 at 167. Ran 8.30’s years ago at 156-7. All about efficiency and maximizing what you have.

Although i have a time slip that says 160 mph, i suspect the fin i have under the front valance tripped the first mph beam, then the tires tripped the second . The little bit of distance (1+ ft?) equals about 1.5 mph differance, and my other best passes were never better than 157.5 to a best of 158.5. so unless i see another 160, i may accept what i suspect as true.
Thanks for everybodys thoughts. I think at this point the headers are best left as is, since if a change took power away, I only have one good set of headers. Not to mention my headers made more tq and hp by about 7 each, over the dyno headers. Due to my exit angle, i can't add collecter length either. So thanks again for thoughts.

I agree fully. These are maxed out or close to maxed out combos. The only unsupercharged S/S cars that come even close are SS/AH. The SS/AH car at Indy that had the best run was 8.396@159.82. I crewed on Comp car for several years. The amount of dyno testing was never ending. Neither of those are one man band efforts. Nor is Ryans Vette. Those are well sorted out as you would know. More money spent on engines and converters than most have in their entire operartion. I don't know how many here have seen the inside of a AH/SS Hemi. Moved lifter bores, intake faces angle milled so the intake nearly falls thru, Hundreds of hours in head development. Share virtuaally nothing with aProduction Gen 2 Hemi. What I'm getting at is that is fot the average racer is that an 8.3x @160 or less would be a very steep mountain to climb.
Doug

Just takes time and effort. Your car is a perfect example. And you are right. Ryan’s car is a two man band not one. Just takes the time and effort. The current D/SA record is 8.39/157. That’s a 300ish inch engine in a 2550ish pound car Depending on exact engine size. Factory body as well. I was not speaking specifically at his et goal when talking about efficiency. That is just an example of what 157 can do. I was referring to efficientvy and what COULD happen with that MPH.