Don Terrill’s Speed-Talk

I don't want to broad brush here; but with that tall of a tire, ideally you're going to want something in the 10.5-12 as far as total gear reduction (what some people call 'starting line ratio'). Torque converter stall comes in to play here, along with your launch RPM, track prep suspension etc. With your 4.88 and a 1.76 glide; thats only 8.6:1 without even factoring in the tire height. For comparisons sake a TH350 has a 2.48 1st gear. Use John's calculator. http://www.wallaceracing.com/calc-slr.php
Set your tire height to 26" and the NEW tire height to your current height.

Im surprised no one said throw a 3speed automatic in it LOL. All things considered; you've got a great combo, you just haven't got it optimized for the eighth mile yet.

cgarb wrote:Sounds like steve needs a faster horse to pull his buggy.

Working on it.! Lol. How acurrate is that formula? According to it we way over geared for 1/8th.? I thought i was same as john need way more gear

autogear wrote:I don't want to broad brush here; but with that tall of a tire, ideally you're going to want something in the 10.5-12 as far as total gear reduction (what some people call 'starting line ratio'). Torque converter stall comes in to play here, along with your launch RPM, track prep suspension etc. With your 4.88 and a 1.76 glide; thats only 8.6:1 without even factoring in the tire height. For comparisons sake a TH350 has a 2.48 1st gear. Use John's calculator. http://www.wallaceracing.com/calc-slr.php
Set your tire height to 26" and the NEW tire height to your current height.

Im surprised no one said throw a 3speed automatic in it LOL. All things considered; you've got a great combo, you just haven't got it optimized for the eighth mile yet.

I was thinking a 3 speed, but we bracket race so I like consistency as much as speed.....almost lol

if you go to a 5.57 from your 4.88 gears it will add about 1000 rpm to your 1/8 mile rpm. if you have it go for it

steve316 wrote:if you go to a 5.57 from your 4.88 gears it will add about 1000 rpm to your 1/8 mile rpm. if you have it go for it

I have the rpm for sure. I was shifting at 7400 and not sure what I go through the traps at. I can figure it out from my 111mph speed. Any guesses how much the 31" tires grow at top end? I'm really interested to see how violent the launch will be. I do believe I will install the wheelie bars I have sitting here.

Only one way to find out...get that wallet out and buy some gears.

cgarb wrote:Only one way to find out...get that wallet out and buy some gears.

Yes, nothing but money stopping me now lol. I figured the roundy round guys around here would have piles of that stuff but nothing yet.

David or Bruce tell you to use 40 degrees?

Ed Wright wrote:David or Bruce tell you to use 40 degrees?

I called R/M once and couldnt get much info on their old 412s. I just went off the pdf file I found for their 427s they build now. The bore is the same and the heads are the same and they say 38-42 degrees. It seems a bit high to me and I think I will go back to 36 and work my way up while watching MPH. What do you recommend?

Hi never had a 410" or 412" SBC that liked over 32 or 34 degrees. They were 14.5-1 on methanol. Brodix -12RI heads.
Must be much different than what are building. LOL
If those guys told me a pizz ant could pull a freight train, I would be trying to figure out how to hook that little sucker up.

Ordered 5.67 gears. Putting wheelie bars on tomorrow gears in Tuesday and will see how good it works on Saturday.

In 1986 I was running a 55 Chevy that weighed 3400 lbs with a 468 bbc. Average times were 6.30s in the 1/8. Car had a 1.76 glide, 4.88, 14x32 slick, converter around 5500.
I went from the 4.88 to a 5.57 and gained basically nothing, maybe 3 or 4 hundredths. Finish line rpm did not go up as much as the math said it would because the converter was slipping with the 4.88. Best I remember the gain in finish line rpm was maybe 400 more.

Hope your change gets you more than I got but there are a lot of similarites. Just my experience. I thought with the weight I was pulling the mechanical advantage of the gear would be more beneficial.

Old School wrote:In 1986 I was running a 55 Chevy that weighed 3400 lbs with a 468 bbc. Average times were 6.30s in the 1/8. Car had a 1.76 glide, 4.88, 14x32 slick, converter around 5500.
I went from the 4.88 to a 5.57 and gained basically nothing, maybe 3 or 4 hundredths. Finish line rpm did not go up as much as the math said it would because the converter was slipping with the 4.88. Best I remember the gain in finish line rpm was maybe 400 more.

Hope your change gets you more than I got but there are a lot of similarites. Just my experience. I thought with the weight I was pulling the mechanical advantage of the gear would be more beneficial.

Well my car is 800lbs lighter and only has a smallblock pushing it. So I hope it gains some. I'm not into spending money for zero results lol.

So got it to the track. Air DA was around 4000. It ran 6.18@110mph. The launch is way more violent and it took a few passes to get wheelie bars set to keep me steered straight. I was shifting it at 7000. I think I should have tried higher but not enough time. Timing was still better at 41. 37 degrees lost me 2.5mph. I think I will try a 1050 Dominator next season. It has a 4150 style 950 now. I am happy so far with the limited passes I have done it feels pretty good and shows the tail lights to alot of BIG big blocks