converter/gear ratio question

70Camaro406

Veteran Member
May 4, 2006
740
Cadillac, MI
Change the converter. I ran 121 mph (11.0's) with 4.10's, 28" tall tires, and was only turning 6400-6500 rpms thru the lights (shifting at 6500). I was running a 10" 4000 stall converter (Darrell Young), and was still pulling low 1.5 60' times (1.509 best). I think that your converter is just too loose. What's the size and stall? With that big of a smallblock, you would be fine with a 3500-4000 stall.
 
Last edited:

70RS_L48

Veteran Member
Mar 4, 2010
386
Seattle Area
D72CamaroZ28 said:
Thats just it bud. I am wondering if my slip percentage will go up if I go to a 3.90 gear? I would hate to change the gear and still go through at the same rpm because of slippage?

Your slippage won't change noticeably at the top end... 7000rpm, 6500rpm... the converter is as coupled up as it's gonna be at that rpm... unless your running a 6500 stall lol. It will flash a little higher at the line. The taller gears will load the converter up a bit more.

70Camaro406 said:
Change the converter. I ran 121 mph (11.0's) with 4.10's, 28" tall tires, and was only turning 6400-6500 rpms thru the lights (shifting at 6500). I was running a 10" 4000 stall converter (Darrell Young), and was still pulling low 1.5 60' times (1.509 best). I think that your converter is just too loose. What's the size and stall? With that big of a smallblock, you would be fine with a 3500-4000 stall.

I'm wondering about your stall too. What are you running? Stall/diameter/brand?

Love Bandimere btw. Ran my car there a bunch of times back in the day... only 13.8's though. :)
 
Last edited:

D72CamaroZ28

Veteran Member
Lifetime Gold Member
Mar 26, 2006
185
The Mile high City
Thanks guys for your help! Its a Continenal 8in an stalls 4800-5200rpm. I was running a 8in that was about 3800-4000 best 60ft was a 1.60 ran 11.36 at 122mph so raised the stall and now its 1.50 60ft an 11.20 at 118mph? And by the way 13's arnt that bad on the mountain bud :)
 
Last edited:

70RS_L48

Veteran Member
Mar 4, 2010
386
Seattle Area
Might sound like an odd suggestion, but I'd see if you can get the same stall built up in a 9"-9.5" converter. The larger diameter converter has more inertia, but it will also couple more efficiently (less slippage) with a given stall. All this assumes you're using quality, application-specific stators and vanes, not a milled down stator in a tiny case.

I swapped a Vigilante 9.5" into my TH700-R4 back in '94, and man does that thing rock. I can cruise it all day without raising the trans temps, and it still flashes a consistent 3200 off-idle. I'm only 1.81 60' but you get the idea. Hits hard down low but doesn't waste RPMs at the top end.

A larger converter alone should bring down your rpm crossing the line. I know that Precision can build a 9.5" Vigilante up to 6500 stall, so your 4800-5200 range is very possible. Not inexpensive... mine cost me $895, but they'll re-stall the thing once for free if you don't like your first. And I haven't had mine out of the car since it was installed! Fluid is still pink, and smells like the day I filled it. Unreal quality.
 

D72CamaroZ28

Veteran Member
Lifetime Gold Member
Mar 26, 2006
185
The Mile high City
70RS_L48 said:
Might sound like an odd suggestion, but I'd see if you can get the same stall built up in a 9"-9.5" converter. The larger diameter converter has more inertia, but it will also couple more efficiently (less slippage) with a given stall. All this assumes you're using quality, application-specific stators and vanes, not a milled down stator in a tiny case.

I swapped a Vigilante 9.5" into my TH700-R4 back in '94, and man does that thing rock. I can cruise it all day without raising the trans temps, and it still flashes a consistent 3200 off-idle. I'm only 1.81 60' but you get the idea. Hits hard down low but doesn't waste RPMs at the top end.

A larger converter alone should bring down your rpm crossing the line. I know that Precision can build a 9.5" Vigilante up to 6500 stall, so your 4800-5200 range is very possible. Not inexpensive... mine cost me $895, but they'll re-stall the thing once for free if you don't like your first. And I haven't had mine out of the car since it was installed! Fluid is still pink, and smells like the day I filled it. Unreal quality.



Unfortunetly this is a new converter only about ten passes on it and it was 1100$! from contintal. It was only stalling about 3800rpm and so I sent it back an told them I needed about 1000 more rpm. They sent it back to me and it is what I asked for - 4800-5000. They told me I would loose effecency and I did lol. It was about 4% when I sent it to them and now its 9. The real problem I was having was the engine quit making power at 6400 an started nosing over. My buddy told me to pull the heads and take to machine shop insted of worring about the gear because my 440 sbc should pull hard to seven! So i did and found out my valve springs weren't good enough and were on there way out. We also found out that the rocker studs were not sealed and the oil and air was getting into the intake runners causing a vacume leak not to mention trying to oil foul my plugs. He also noted that one head had 68.3cc chambers and the other had 67.2cc. I purchased these heads new from dart and they should have both been 64cc? The machine shop also found that the rocker stud holes on cylinder 2 were off by by .014! So maybe were on to somthing here and will find out after the heads are fixed and we can make some passes before talking about gear. OH and by the way I called Dart and asked them about the cc of the heads being so far off and the studs not being correctly spaced and they told me that the measurements we found were all within spec! there are going to be variations in every head even though my heads were stamped 64cc its ok for them to be 68?:eek:
 




Latest posts

Top