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Discussion Starter #1
First: I will be installing a p600 procharger/intercooler and was wondering what other modifications will be needed. I'm making 350 rwhp and 400 rwtq before the s/c. new injectors etc...?

Second: what is the current final drive ratio? 2.59 or 3.07? its a convertible, where can i find the info?

Third: Do you guys suggest going with a 3.54, 3.73 etc, with the s/c? or stay with the stock gearing? its an automatic.

Thanks
 

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If you are already making 350hp/400tq, what mods do you have on the car already. I would say that you already upgraded the injectors to get that kinda power out of an L98. Also, which intake are you running. That would be a good place to start as well as headers and a good flowing exhaust.

Your gears are easy to figure out. Look under the door of the center console and the RPO code sheet should be stuck there. Search the forums for rpo decoding for a c-4 and you will find what gears you have. If its auto, 98% were 2.59 gears. The 3.07 usually only came in the nash manual cars.
 

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Discussion Starter #3
ported alum. heads, headers, cam, filter, 52 mm maf, edelbrock runners, filter w/ lid, borla full stainless system, 24# injectors, msd ignition
 

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If you are already making 350hp/400tq, what mods do you have on the car already. I would say that you already upgraded the injectors to get that kinda power out of an L98. Also, which intake are you running. That would be a good place to start as well as headers and a good flowing exhaust.

Your gears are easy to figure out. Look under the door of the center console and the RPO code sheet should be stuck there. Search the forums for rpo decoding for a c-4 and you will find what gears you have. If its auto, 98% were 2.59 gears. The 3.07 usually only came in the nash manual cars.
My 85 is an automatic, and it has 3.07s.
 

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If you are going with the kit from ATI, it comes with a new pump and their product literature says that no new injectors are required. If you bought the supercharger only, you may want to give them a call and get the rest of the kit.
 

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its an automatic.
I'm betting you have the 2.59. Going up to a 3.54 or 3.73 in just NA form will be VERY noticeable. Throw a SC into the mix and you might want to buy stock in your favorite tire company. :laughing:

Is your trans already beefed up? Mine didn't last very long w/ just a cam, headers and 3.54. I would have it beefed up to handle at least 100 hp more than what you project it to be.

24# injectors should be fine and like RTGordon said, a new fuel pump should be included in the kit.

Are you doing the install yourself?
 

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Discussion Starter #7
thanks for the advice. I will either install it myself, or have Doug Rippie install it, depends how much time I will have this summer.

As for the final drive, what if i went with just the 3.07 or something not as drastic as the 3.54/3.73? Basically, I don't want to be fixing it more than I am driving it, but i want to utilize all the power the supercharger will pack.
 

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The reason I asked if you were going to install it was if you do, TAKE YOUR TIME! It's easy enough to do. Sometimes the instructions can be wishy washy. Keep the tech line # handy just in case. IMHO, they could put more photos in the instructions as well as making them bigger and clearer. Also, the belt might be super tight so 2 people would be needed to install that if it is. Also if you do DIY, if you don't have an auto x-ray or something similar, get ahold of one. You want to at least make sure the injectors are running properly. You want to check the injector pulses and see if it's running too rich or lean.

Gearing.....I drove a SC'ed 95 w/ the 2.59. Even in SC'ed form it didn't have that oomph. The owner opted for the 3.54 and it slammed you into the seat. As long as the gear is installed correctly, and I mean the tolerences are measured w/in a few thousands, a 3.54 should last. The trans will not unless you have it beefed to handle the hp/torque. In all likelyhood you'll have at or more than 620 ft./lbs. if you have the 8 psi unit.
 

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Discussion Starter #9
i don't know now, i think i might just go with the 3.07 and see how that goes. How much difference would 2.59 to 3.54 make in ET and mph? does anyone have a L98 procharged with 2.59s or steeper?


I appreciate all the advice.
 
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