Wicked69

I am running the On3 70mm twin turbo's with my JY 5.3. I am planning to continue to use my XER273 cam (specs in signature). My car did have a hard time spooling off the line with the PT62's (twins). I have a Th400, PTC3400 Stall, and 3.90 rear end gear, and plan to run 315/60 (30" tall tire) However, may be forced to continue to run the 28" tall tire. The problem is that if I go taller than 3.73 I will have to change out the carrier. Seeing how this is a street car first I think a much taller gear will help with spooling and actually let the car ET better. Also, I ran out of gear when I did run the 1/4 and don't want that to happen.

So, since I will have to change out the carrier anyways I want to know what rear gear ratio would be the best for performance in the 1/8 and still work in the 1/4. Anything taller will help it to run better on the street and I think I can't go to tall because my car weighs almost 3900lbs.

I was thinking 3.23, 3.31, or 3.42. Performance only with the 5.3 and these turbo's which gear would be the best to help make my combo better?

Still running E85 and meth but plan to go to 100% meth for next year. The reason is now a lot of local pumps are running a minimum of 51% Ethanol instead of 70% and I don't run an intercooler and have no plans to.

Let's hear your opinions. Remember, my car is not light....it's heavy as hell!

LilJohn

Id try the 3.42 or 3.31 first....

It SHOULD make the converter act a touch looser down low... if not... talk to Lane about trying a couple hundred more rpm on the stall to help get the turbos lit off.

Do you remember where you installed that camshaft at?

redcam622

I Agree ...Lane fixed my spooling poblem..went from 1.35 60' to 1.17 with a converter tweek..3.42s should be fine

Wicked69

cam shaft was installed straight up.

Wicked69

Man, I would hate to touch the convertor. It's hard to beat 118mph in the 1/8th with the set up I had. That's about 10mph faster than I thought I would get. The taller gear sure will make it much nicer to drive.

LilJohn

And if you get the gearing and converter right.... itll go 120...

Define straight up for me. Did you use a degree wheel or are you talking dot to dot?

Do you know if the cam had any advance ground into it?

Wicked69

I installed it dot to dot. The cam is in my signature. It was a used cam.

Sales@Tick

iTrader: (3)

3.42 gear. I had a 3.55 in my 3900lb turbo car with the same trans gearing and wish I had went higher.

Wicked69

I know that a 3.23 would be better for the street and am willing to try the 3.42 but just have a question. Would the 3.23 normally work better but because my car is heavier the 3.42 would work better or is it a combination of the weight of my car, trans, size turbo, and cam I am using? Just trying to understand why the 3.42 would be better over the 3.23.

Also, I am assuming I can expect that any of those will make the car run faster over the 3.90's that I am currently running. And again just to make sure I am getting this correctly. Is it because the steeper gear does NOT allow it to pull as hard or spool as quick than a taller gear would?

Thanks.

LilJohn

The 3.90 provides more mechanical advantage.... thus reducing load on the motor... that load is what we need to make the turbos work. So we take away the mechanical advantage.. load the turbo harder...which then works the converter harder and we pick up power.

You have to balance the mechanical advantage with the weight. If you were 3300-3400... id say 3.23...but because of the extra weight... id let it have a little more help running the 3.42.

Do you have a degree wheel and know how to check your installed centerline?

Im really curious... and believing that cam might not be in the right spot....

Wicked69

thanks for explaining that. I do not know how to check with the degree wheel, but can probably find someone to help me. Where do you think I should install it?

LilJohn

That cam should have had some advance ground into it.... but its never dead on doing the dot to dot thing..

It SHOULD be in on a 110 if things are right... odds are they arent. Moving it to a 107 will give that motor alittle more *** down low.

Id like to see you check the cam first just to verify its installed centerline before ya tear into the rear.

Sales@Tick

iTrader: (3)

John is right, giving it more advance will help spool, help torque production down low, and help make a broader power curve by opening the exhaust valve sooner.

All these things can help a turbo car, especially a heavy turbo car get up into boost quicker and run faster on the street and at the track.

Wicked69

I will see if I can get someone to help me check the cam and advance it.

Turbomanx

Also if you have any tire spin it will be more prone to blowing the tires off
With a taller gear!

Wicked69

No tire spin. Check out the picture in my signature. Suspension works really well.

I think I will see if I can trade someone my 3.90's and 4 series carrier for a taller gear and 3 series carrier for a 12 bolt rear....Assuming theirs is also in excellent condition.

skinnies

iTrader: (33)

Even at that weight, a 3.23 should be enough to get it 60ft in the low 1.30 range at that weight IF those 70's will spool quick enough and it'll drive better on the street. I say put in as lil gear as you can for a STREET car. My ltd at over 4000lbs with a glide and 2.73's and 27" tires been 1.5 60ft on street tires(not drag radials), on a 26x8.5 slick I'd be upset if it didn't go 1.3 60fts. It's all in power management and making suspension work.

Wicked69

What is interesting is I can't find anything taller than 3.42? I have been searching for hours. I have a 12 bolt with 33 spline axles, full spool. I guess I will have to see if someone wants to swap a tall gear, spool and carrier.

skinnies

iTrader: (33)

Yeah we swapped spools in my buddies car so could run a 3.08 gear from the 4.10's it had.

71 chevy

iTrader: (18)

i agree with this.