Peak torque move puzzling?

[gtca9014]

I got a question that have not got a good answer for that maybe someone here could help me out with. I have a super stock BBC that dynoed 652hp@7500 493tq@6300. We knew it was down on power and found a main bearing going. Fixed that with no other change 674hp@7200 525tq@5800. Same dyno that is reliable. Previous similar engines dynoed are in the 6100-6400 peak range. Question is how did peak torque move down 500rpm? What factors can move peak torque that much? Feel like if can get peak back up there the thing will fly.

[Walter R. Malik]

I got a question that have not got a good answer for that maybe someone here could help me out with. I have a super stock BBC that dynoed 652hp@7500 493tq@6300. We knew it was down on power and found a main bearing going. Fixed that with no other change 674hp@7200 525tq@5800. Same dyno that is reliable. Previous similar engines dynoed are in the 6100-6400 peak range. Question is how did peak torque move down 500rpm? What factors can move peak torque that much? Feel like if can get peak back up there the thing will fly.

I suspect that the torque is about the same near 6,300 RPM just that it now made more below that.

Was there a header change or something similar to that ...?

[gtca9014]

I got a question that have not got a good answer for that maybe someone here could help me out with. I have a super stock BBC that dynoed 652hp@7500 493tq@6300. We knew it was down on power and found a main bearing going. Fixed that with no other change 674hp@7200 525tq@5800. Same dyno that is reliable. Previous similar engines dynoed are in the 6100-6400 peak range. Question is how did peak torque move down 500rpm? What factors can move peak torque that much? Feel like if can get peak back up there the thing will fly.

I suspect that the torque is about the same near 6,300 RPM just that it now made more below that.

Was there a header change or something similar to that ...?

Thanks for the reply. 518tq@6300, the bearing was holding it back. No header changes. Is really puzzling. If can figure this out, should be big. What type of changes can move torque peak 500 rpm?

[1972ho]

So how much torque is making at 6300 since the bearing change a lot less or pretty close.Could the valve springs be giving up a little with that radical superstock camshaft.

[Frankshaft]

Sure the cam went back in at same spot?

[gtca9014]

So how much torque is making at 6300 since the bearing change a lot less or pretty close.Could the valve springs be giving up a little with that radical superstock camshaft.

518tq@6300 after bearing fix. Springs checked out. Not sure that would make a 500rpm peak move at that low of rpm but?

[gtca9014]

Sure the cam went back in at same spot?

Thought of this also but builder says it is same. How much would it have to be off for a 500 rpm peak move?

[John Wallace]

Why not just post the dyno sheets?

Easier to see the whole picture than one RPM segment.
(plus the BSFC, weather conditions, etc)

What was the HP peak RPM on both?
Did it change also?

[Frankshaft]

I am guilty of this too, but, read the threads. All the redundant questions. It's all been said by op. Peak power 7500 before fix, 7200 after. Peak tq 493 at 6300 before, 518 6300 after, 525 peak at 5800. Sounds to me like cam isn't installed the same. If the engine was fighting itself, doesn't make sense it lost rpm, makes sense it's up power.

[Stan Weiss]

7500 - 7200 = 300

6300 - 5800 = 500

500 - 300 = 200

So in the new test peak torque only moved 200 RPM relative to peak HP, which drop 300 RPM.

As was ask why not post up the dyno sheets?

Stan

[gtca9014]

Here are dyno sheets

[gtca9014]

7500 - 7200 = 300

6300 - 5800 = 500

500 - 300 = 200

So in the new test peak torque only moved 200 RPM relative to peak HP, which drop 300 RPM.

As was ask why not post up the dyno sheets?

Stan

First pull stopped at 7500, peak could have been higher.

[canada1]

Water temps look much cooler on the dyno chart which made more power.
What fuel are you using?

Cheers

[gtca9014]

Water temps look much cooler on the dyno chart which made more power.
What fuel are you using?

Cheers

Yeah, we were trying to find problem first time. But the oil temp was cooler than we like on the final pull which should help with offset improvement of cooler water.

[LSP]

#236 peanut port combo?