Peak torque move puzzling?
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Peak torque move puzzling?
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.
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Re: Peak torque move puzzling?
I suspect that the torque is about the same near 6,300 RPM just that it now made more below that.gtca9014 wrote: ↑Tue Dec 05, 2017 9:18 am 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.
Was there a header change or something similar to that ...?
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Re: Peak torque move puzzling?
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?Walter R. Malik wrote: ↑Tue Dec 05, 2017 9:38 amI suspect that the torque is about the same near 6,300 RPM just that it now made more below that.gtca9014 wrote: ↑Tue Dec 05, 2017 9:18 am 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.
Was there a header change or something similar to that ...?
Re: Peak torque move puzzling?
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.
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Re: Peak torque move puzzling?
518tq@6300 after bearing fix. Springs checked out. Not sure that would make a 500rpm peak move at that low of rpm but?
Re: Peak torque move puzzling?
Thought of this also but builder says it is same. How much would it have to be off for a 500 rpm peak move?
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Re: Peak torque move puzzling?
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?
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?
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Re: Peak torque move puzzling?
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.
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Re: Peak torque move puzzling?
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
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
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Re: Peak torque move puzzling?
Here are dyno sheets
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Re: Peak torque move puzzling?
First pull stopped at 7500, peak could have been higher.Stan Weiss wrote: ↑Tue Dec 05, 2017 12:32 pm 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
Re: Peak torque move puzzling?
Water temps look much cooler on the dyno chart which made more power.
What fuel are you using?
Cheers
What fuel are you using?
Cheers
Re: Peak torque move puzzling?
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.