Gear Ratio Tire Size

[stevec]

Just wondering what you guys are running for rear gears and tire size??

My combo is a 3.23 with 2755015 drag radials(25"). I have been shifting the motor 274 Stage II at 6800 and going through the traps at ~7000 with the conv locked up mph is 142.

I believe my engine combo will max out at around 7500 with 236/236 cam and 30 psi boost. Should put the MPH around 146. The conv is 4200 stall.

The reason is were are going to a 9" ford and may try more gear and taller tire.

Thanks

SteveC

 

[John Wilde]

Chris Chow is using a 29.5 tall tire and 3.89s with a turbo 400 and 5000 Plus stall. He goes through around 7000 and 150mph.

I have used 28.5 with 3.90 and a 200. It would need around 6200 rpm and 130 plus mph. It never made a full pass, long story.

 

[turbobuick]

Hey Steve,
Have you thought about going to the 325/50/15 BFG DR? I believe that tire is a true 28x10 and would provide some much needed traction over the 25x10 you are running. I would think the 28x10 and a 3:90 would put you in the ball park. Also, why are you going to a 9"? With the DR and the 200r4 w/o a brake I doubt you would ever have a problem with the 8.5" not worth all the expense IMO unless you plan to break down and finally run slicks and a T-brake. I thought you had a 400? Are you running a LU conv with the 400? If so I would like to know more about it.
Chris Lyons

 

[RobCrisafulli]

The trans is a 400 with lockup from PI. Ask for Vickie she can give you more info. They make a no brake and trans brake model. No suprise it is not cheap. I have one of the first ones and we have punish it for years now. We use it like an extra gear and need it to get down the track. If I showed you the Felpro run it hits as hard 1-2 or 2-3 shift, you could not tell the difference.

I am going to a 9" for piece of mind. The car weighs over 3800 when we race it and I do not want to tear up the car if the rear breaks. With the short tire we need a small gear to get down the quarter. It is a lot of load on the pinion. The original 3.42's were cracked quite a bit when they cam out with less motor and 60 foot.

Once the 9" is in we can wick it up all the way and not worry. Do get me wrong, I have seen guys run mid 9's on the bumper with 10 bolts but they are 3300-3400 pounds, with 35 spline axels and spools. The car is just to heavy.

Robert

 

[turbobuick]

Are you going to try and gear the car for the LU or are you going to try and lock the convertor earlier in the run. At what rpm do you engage the clutch and where are you in the run? Where is the car in the traps w/o the LU? Just curious.

The stock 3:42's are pretty weak especially when you get into the 10's. The aftrermarket gear sets seems to be alot beefier and take more abuse. Rumor has it Moser is going to coming out with a pro gear for the 8.5". My understanding is the 8.5" pinion has the same diameter pinion as a 12 bolt and they seem to be strong enough. If you have the 35 spilne axles and spool I wouldn't worry even at that wieght. But then again I can totally understand the piece of mind issue especially at that speed. That is a nice car and I would also hate to see it torn up.
Chris Lyons

 

[RobCrisafulli]

We hit the lockup at 6800-7000 top of 3rd. Without the lockup the car would run out of rpm before the finish line.

The rear is a stock posi, Moser 28 spline axle with clip eliminator. My problem is lack of pinion support with the 10 bolt.

Hopefully, the 9" will be in the car in the next month and we can beat on it again. We got plenty of work to do on the TTA in the mean time.

Robert

 

[John Wilde]

Rob,

Could you tell us more about your car please?
Are your racing with the NMCA or any other class racing??


Thanks in advance.

 

[RobCrisafulli]

The car is a stock appearing 87 Limited with 30k miles. Full weight 3800+. Stage 2 274, 6.5 rods, 3.625, GN1R one of the first sets (no problem so far), BG intake, PTE 88 3 bolt, ATR headers, HKS wastegate, custom 3.5 dp, ATR 3" dual 3" exhaust, 160#, Felpro tuned by self, Weldon pump, sumped stock tank, regular PTE FM, 236 solid roller, MSD, column shift 400 lockup from PI, 4000 stall, 3.23 10 bolt, 275/50/15 drag radials on factory T wheel, Wolfe sway bar, QA1 shocks, 5 point swing out bar.

The car was built to run low 10's on drag radials and run in TSE 3 years ago. We just recently upgraded to the PTE 88. The car is legal to 10.0. Technically we can get booted out becuase it runs 139-142mph and we have not wicked it all the up. I think it can run 145-147. The tracks in Maryland are very strict but I think we can get away with high 9's.

Basically, it is the same motor you see guys running low 9's high 8's but without the big ass slicks sticking out the fenders, trans brake and 3300-3400 weight. It drives great on the street and we cruise it to the local spots.

It would be nice to try to run NMCA/NSCA MSD true street, its a cruise and 3 runs averaged closest to 10.0

Here are some pics from the Nats thanks to warped:

http://users3.ev1.net/~lmarlett/buick/thurnats/image64.htm
http://users3.ev1.net/~lmarlett/buick/thurnats/image65.htm
http://users3.ev1.net/~lmarlett/buick/thurnats/image66.htm

Robert

 

[John Wilde]

Thanks Rob,

That is one sick street car.
Let me know how it goes when you turn the boost up!
Are you running the Nitto's or BFG's?
What kind of 60s are you getting???

Thanks in advance

 

[S2V6RACER]

Originally posted by RobCrisafulli
The car is a stock appearing 87 Limited with 30k miles. Full weight 3800+. Stage 2 274, 6.5 rods, 3.625, GN1R one of the first sets (no problem so far), BG intake, PTE 88 3 bolt, ATR headers, HKS wastegate, custom 3.5 dp, ATR 3" dual 3" exhaust, 160#, Felpro tuned by self, Weldon pump, sumped stock tank, regular PTE FM, 236 solid roller, MSD, column shift 400 lockup from PI, 4000 stall, 3.23 10 bolt, 275/50/15 drag radials on factory T wheel, Wolfe sway bar, QA1 shocks, 5 point swing out bar.

The car was built to run low 10's on drag radials and run in TSE 3 years ago. We just recently upgraded to the PTE 88. The car is legal to 10.0. Technically we can get booted out becuase it runs 139-142mph and we have not wicked it all the up. I think it can run 145-147. The tracks in Maryland are very strict but I think we can get away with high 9's.

Basically, it is the same motor you see guys running low 9's high 8's but without the big ass slicks sticking out the fenders, trans brake and 3300-3400 weight. It drives great on the street and we cruise it to the local spots.

It would be nice to try to run NMCA/NSCA MSD true street, its a cruise and 3 runs averaged closest to 10.0

Here are some pics from the Nats thanks to warped:

http://users3.ev1.net/~lmarlett/buick/thurnats/image64.htm
http://users3.ev1.net/~lmarlett/buick/thurnats/image65.htm
http://users3.ev1.net/~lmarlett/buick/thurnats/image66.htm

Robert

I would be interested in one of you datalogs and GCT file if you wouldn't mind. I have a off-center that will be an EXACT duplicate of your motor. I only plan on running the PT-76 4 bolt though.

Can't blame you on the 9" That's what I got, and it's nice to not worry about anything.

E-mail me if you would.

Ted

 

[RobCrisafulli]

Running BFG's. Check back in a month. The car used to low 1.5 when it was a stock block 10.50 ride. We are only low 1.6 high 1.5's right now with a few pounds of boost on the line. We were worried about the rear and after seeing Cotton blow his up, that was enough of a reminder to do it right. I think 1.4's are do able at a well prepped track.

Robert

 

[EightSecV6]

Steve/Rob,
Lemme know if you have not already bought the 9", I can take care of you guys on the Moser stuff.
Bill

 

[RobCrisafulli]

Thanks I will keep that in mind. What is the ETA on your car?

Robert