I'm living on an island in the south pacific where the max (legal)speed limit is 30 MPH, no smog sniffers or inspection stations. I recently got a deal on a 88 350 Iroc (bad trans), Irebuilt the trans with max clutch pack mod's,Transgo H.D. shift kit, vette servo, 2500 stall converter plus some other mod's.

Next I want to get rid of the 9-bolt for a Currie 9-inch, I'm going to rebuild the engine last. My limiting factors are 1 driven daily, 2 fuel octane available on island (I'm still trying to get a answer from the island supplier) the pumps show no octane rating, I'm guessing 87 octane. Until I get a sure answer on this I don't want to go above stock compression 9.3.

My question is what is the best gearing that I can put in my car that will take advantage of the 30 MPH limit? I'm guessing 4.86's will keep the RPM's around1500 at 25 MPH in 3rd gear with mechanical lockup valving installed. I plan to use ported vortec's, intake, a cam that will work good with the compression limit; I'm guessing 15 to 5500 RPM. I'm planning on doing any bolt on's that will get it to hookup with out sacrificing handling. Any input will be helpful!
Thanks, Kelly

 

I'd keep the stock gearing and just use 3rd gear (assuming that it has 3.42's or 3.73's), You may want to burn a custom prom that locks up the converter at your "cruise" speed in 3rd.

WOW, 30 mph max.....I'd be in jail for life there.

 

My Idea behind the 4.86's is the RPM that it will spend most of its time at, stock gearing 2.77's at normal freeway speeds 60 MPH = 1503 RPM in O.D. In 3rd at 25 MPH with 3.70's= only 1200 RPM, with 4.86's=1570 RPM. There are straits that are a 1/2 mile long and I would like to get from one end to the other as quickly as possible, (before the other guy) I would like to make this car as quick as possible for what limits I have to deal with. Oh, and I just got a word back today, the octane here is 88 so I need to find info on max safe compression for 88. I figure with 4.86's I'll have a top end of 125-135 MPH.

 

The stock 9.5:1 will work with 88 octane just fine as long as you don't get carried away with timing tables (assuming you burn your own prom)