quote:

Originally posted by blowerman:
I have a 5.13 in the car now and thinkng about 4.88 or 4.56.Right now the car is crossing at 7100. I think that is to much.I am thinking about a 4.56. What everybody think. Converter flash to 6400. Thanks

quote:

Originally posted by blowerman:
The converter is spragless and the car has 14x32 M/t. Car is good I just want to lower the finish line RPM.Thanks

The OP is concerned about his current RPM & wants to lower it. If he does lower it, he will have to be worried about the 6400-flash stall being higher.

Blowerman, have you decided what you're going to do? Just asking out of curiosity.

2BKING

I've run 4.11's, 4.33's, and 4.56's with a couple of different converters, and it's never moved anything but the 60' time, and finish line RPM's.

Converter doesn't know what the rear gear is when it comes off the brake.

What Goob said…. imho, he won’t see more than 25 rpm gain at most in flash going to 4.57. What he might see is a reduction in the rpm dip after flash. The dip could become less and possibly flat line. This isn’t bad and personally I’d bet just as consistent as prior.

I think flashing to 400-500 of max hp great for consistency and produces faster ET.

This photo is my car using a 4.40 gear in the green trace (run 0478). I switch to a 5.14 gear in red trace (run 0481). Look at the flash rpm (Cur2 in red at 0.500 after launch) between these two……. almost exactly the same. Now look at the 5.14 gear with converter re-stalled in the black trace (run 0482). The black trace is the fastest run of the three. Cur1 in blue is the Launch rpm.

That brand new converter was stalled incorrectly from day 1 and the re-stall was just as bad. I ran that converter the entire year because they said it’d loosen up, it didn’t, they agreed to fix it and in the end it was finally correct in what I initially requested.

quote:

Originally posted by B KING:
We made a rear gear change at the beginning of 2025. It was for the same basic reasons as the OP. Our combo is totally different than Blowerman's.

Our Camaro is 3100 lbs. & was going through the traps 1/4 mile around 7,400 with a 30" radial. Anyway, we decided to switch from the 3.89 to a 3.55. We lost around 300 rpm & we gained 300-400 rpm in converter stall.

This was one of the best changes we did with this combo/race program. More to come in a different thread.

I guess you guys need to tell my convertor it's wrong & needs to go back to its old ways. Plus, tell Kevin at Hughes he doesn't know what he's talking about. He called it before I made the change.

I understand combos are different but the basic rule of thumb in this change will increase the stall in most cases.

It really doesn't matter what our combos do or don't do. It only matters that the OP gets his RPMs lowered, but he needs to determine where it needs to be with or without our help.

Most of us are experts on our own combinations or at least we think we are & that's what we revert back to.

2BKING

Here’s a recent planetary change using the same 5.14 rear gear. The SLR changes considerably (by 0.82) but the flash remains the same. What does change is the dip after the flash. The reduced SLR will flatten that dip out as I wrote prior.

The converter (2025) in this planetary change example is a spragless. The converter (2020) in the prior rear gear change example is a sprag type. Both examples show similar results given the same HP. The SLR changes, the flash remains the same and the dip after flash changes.

I’m showing what I see changing SLR multiple ways with different style converters using the exact same HP engine. Converters are voodoo and believe anything is possible.

quote:

Originally posted by B KING:

quote:

Originally posted by B KING:
We made a rear gear change at the beginning of 2025. It was for the same basic reasons as the OP. Our combo is totally different than Blowerman's.

Our Camaro is 3100 lbs. & was going through the traps 1/4 mile around 7,400 with a 30" radial. Anyway, we decided to switch from the 3.89 to a 3.55. We lost around 300 rpm & we gained 300-400 rpm in converter stall.

This was one of the best changes we did with this combo/race program. More to come in a different thread.

I guess you guys need to tell my convertor it's wrong & needs to go back to its old ways. Plus, tell Kevin at Hughes he doesn't know what he's talking about. He called it before I made the change.


2BKING

Boosted is another totally different world than us 500-650 HP N/A deals.
You're also talking about gear ratios way out of our ballparks.
Terminology is important too.

Stall= Brake on, to the wood max RPM.
Flash= RPM at brake released.
Fallback= RPM after shift. ("stall"?)

Not here to argue, just reporting my results from my rudimentary data recording assets, over 25 years of running / refining the same basic junk.

quote:

Originally posted by Goob:
Boosted is another totally different world than us 500-650 HP N/A deals.
You're also talking about gear ratios way out of our ballparks.
Terminology is important too.

Stall= Brake on, to the wood max RPM.
Flash= RPM at brake released.
Fallback= RPM after shift. ("stall"?)

Not here to argue, just reporting my results from my rudimentary data recording assets, over 25 years of running / refining the same basic junk.

Goob,

I don't take it as arguing, I take it as good debate & opinions! Better than my way is the only way, we've heard that before.

I'm not only talking about my boosted gear ratios. I've been street & bracket racing with over 40 years of experience. The vast majority was NA & some nitrous, in the ballpark of 500-650 HP.

As for terminology, I agree. All the terminologies changed with a boosted gear change & I agree it was to the extreme. I didn't believe it would change that much when Hughes (Kevin) told me that. My data logs confirmed what he stated almost verbatim.

As for my vast experience racing NA & discussions with converter manufacturers over the years. Changing gear ratios like the OP posted in the vast majority of circumstances will raise the stall & going the other direction will lower it. It's all mute, as far as the original posters post. He or she was only worried about lowering the rpm & a gear change as he stated will do that.

Then I, you & others interjected our opinions. While trying to be helpful, I think we failed to answer the OP's objective. Blowerman needs to figure out the RPM that's acceptable for what he wants. Change it & either live with, make another change or put it back where it was.

2BKING is more than happy with his gear change. Only pluses & no negatives that I can figure out anyway.

for each gear change usually 250 rpm, just another multiple year opinion

quote:

Stall= Brake on, to the wood max RPM.

To claim that RPM will change with the rear gear ratio is ludicrous.
That RPM will not change if you throw the driveshaft on the floor, let alone change rear gear ratio.
That number will only change with HP, fluid viscosity / temp, or converter modification.

Your experience or view may vary. Mine won't.

quote:

Originally posted by Goob:

quote:

Stall= Brake on, to the wood max RPM.

To claim that RPM will change with the rear gear ratio is ludicrous.
That RPM will not change if you throw the driveshaft on the floor, let alone change rear gear ratio.
That number will only change with HP, fluid viscosity / temp, or converter modification.

Your experience or view may vary. Mine won't.

Easy Goob, you're ready to blow a gasket!

I used the wrong terminology, sorry. I have no reason the check "Stall= Brake on, to the wood max RPM.". My Flash & Fallback RPM changes with rear gear changes both NA & boosted during my 40 years of experience. I hope I worded that right for you.

2BKING

goob if you are referring to my statement i was answering the op for finish line rpm

Based on what the OP wrote I estimate this for 1/8 mile finish line rpm reduction.
5.00 @ 107 less rpm
4.86 @ 222
4.57@ 460
Converter flash rpm remains same for all gears.

This message has been edited. Last edited by: markemark,

slippage in 1/8 is tricky

Speaking of gears for door car. I would like to find a 9in third member. 35 spline spool with a 4:30 gear if anybody might know where one is somebody would part with. Aluminum or nodular will work.

ep

quote:

slippage in 1/8 is tricky

Agreed. The OP 6400 flash is very close to what I’m seeing with a spragless and used 13% slip.

quote:

Originally posted by rusty:
goob if you are referring to my statement i was answering the op for finish line rpm

I would agree entirely, as that has been my experience.