Powerglide, 8" Converter and 9" rear with 31x14 tire - would a loss of 10% HP be a reasonable assumption?
Take for an example any car that runs better than it should, meaning it's optimized. To calculate the standard percentage.
Wallace has a calculator that figures flexplate HP and back tire separately according to inputs of weight and et.
Calculate any other similar car for tolerances in comparison to the standard.
10% is probably a bit light.
I've used 15% since auto mechanics in vo-tech and it's pretty close.
A ford 9" is about 94-95% efficient due to its high offset of pinion to ring gear.
The PG from the input shaft rearward is probably around 94-97% efficient in high gear at best due to the two sets of bevel gears in the planetary.
The 8" convertor is the wild card - this would need to be estimated by the temp increase in the oil from start to finish of the run.
If you go by slip %, then it could be about 8% slip, or 92% efficient.
Now multiply them all together:
Optimistically, .95 x .97 x .92 = 85% efficient.
Which brings in a question from me. When building up a powerglide, what do you guys do to reduce parasitic drag? I have Carl's book and have read it, but do you guys use the practices that he's written?
I think there are a few things you can do that help, whether they are truly measurable might be questionable.
I always mod the back of the pump for a torrington bearing instead of the normal bushing. And I think the roller bearing rear support is another drag reducing trick. I also remember reading something about putting pieces of 0-ring rubber in the main clutch pack? - I'm probably off by a mile here but maybe somebody else can shed some light on that one.
Run a good synthetic fluid. Like Allison 295 fluid
That's a helluva book. I talked to Carl (rip) about that book once, and he said he wished there were a little more profit in writing it, like maybe he regretted writing it possibly. Carl didn't say that and I may have read him wrong. But I told Carl one thing is for sure, no matter what,,,,, your name will live on.
And here we are keeping Carl alive, I think it's pretty cool.
He tells everything in there to do, it's up to you to read between the lines of what he's saying, in order to take it a step further.
My little 3200 lb sbc street car Nova can go double 0's on a .370 pro tree. That book of Carl's is responsible for a lot of the reason why.
I do most of the "tricks" in his book and as stared above each mod may be hard to measure but I think the sum is worth doing. It is a good book.
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