Hi all, I would love to get some suggestions on what gear to run, here is my combo:
· 396 Bored .040 over
· 9.7 : 1 Compression
· 702 Heads with 3 angle grind, bronze guides, & hardened seats
· Speed Pro Forged Pistons (part # L-224ONF)
· Eagle SIR I Beam Rods
· Comp Cams XE274H-10 - .552 .555 / 230 236
· Comp K-kit (matching valve springs ect.)
· Harland Sharp Roller Rockers (1.7 Ratio)
· Holley 700 Double Pumper
· Performer RPM Intake
· GM HEI Distributor
· MSD 6AL Ignition Box
· Hooker Super Comp. Headers (with jet coating)
· Muncie M-20 Tranny / 3.23 –12 bolt posi

This a mostly street driven car, but I am looking for good performance as well, but still want to be able to drive it on the freeway.. I was thinking either 3:55's of 3:73's what do you guys think???

TIA,
Scott

3.55's

I agree, 3.55's is where it's at if you still want to be able to cruise the highway in fashion.

3.73's would be my choice,,,thats what I have and I wish I had gone to 4.11's for a tad better performance(since I'm closer to the big city now) when I had the Eaton posi installed. I can cruise at 70 yet still run high 11's with the 3.73's.

I just went from a 3:73 to a 3:42 with a M20 and a 27" tire and like it a lot, good around town & about 2600 rpm at 60 mph. 3:73 was not so good on the highway, about 3000 rpm at 60 mph. Dave

Your tires are too short...28" tires work good with 3.73's. 70 is around 32-3300 rpm.

if it's just an occasional trip on the highway then i'd go with the 3.73's.

I don't drive on the highway alot, but have been thinking about a pilgramage to Chevellabration.. Other than that, 15 - 20 min trips @ 60 - 65MPH..

Also will be replacing the tires this winter, so that can also be changed..

Would there be enough differance between the 3:23's & the 3:55's to justify the change??

Thanks,
Scott

How was the race???? I'm an automatic guy so not sure about the gear selection. But.... 3.55's sound good to me.
Carpet came though SWEET!!! Thanks again graemlins/beers.gif Mike

Scott, I like the 331s for highway use. I personally wouldnt want more, especially for "freeway" speeds. Have you thought about the tranny gears?

Go to a 28 inch tire and go with the 3.73's. If you are using a 26 inch tire, then 3.55's. The great thing about the 3.73's ois that you can use a 26 inch slick (or drag radial0 at the track and still get the benfeit of a lower gear. Then swap out to your 28 inch tall street tires, and you'll get the benefit of lower RPM's at speed.

Scott (or anyone):

If you have Microsoft Office 2000 (Excel) software on your computer, I am happy to share a little spreadsheet I made that lets you pick your transmission, rear end gear and tire size. It wil then list RPM by MPH for each gear. If you email me (in case I forget to check back here) I will send it to you. This might help you see your cruising shift points or your MPH at redline points.

http://www.project33.com/tiresize.cfm This should give ya an idea. Mike

Scott, I think you'll be much happier with a wider ratio transmission and less gear. All the G.M. 400 inch motors i've owned all got considerable better gas mileage with low three series gears. A newer five or six speed transmission is the ultimate but if the money isn't available the 2.54 geared Muncie will seem like the car has more gear. How did you come up with a 3.23 rear end gear? This isn't a normal gear set for a twelve bolt. Most of the old Chevies had 3.31s. If you find a later model G.M. car like a Trans Am it might have a Super T-10 in it with better gearing.

Harold, I am guessing at the 3.31, that is to say, that I did the old spin the tire & count the rotations, the drive shaft spun about 3 and 1/4 times.. Could very well be 3.31..

Changing the tranny is really not an option (at least for now) I just got the muncie, it replaced the saginaw that came with the car.. I prob would have gone with an M-21, but a friend gave me the M-20... Although I did put a couple of hundred dollars into it (total rebuild)..

So at this point, the best thing for me, is to put some gears in it to wake it up a little..

PS Ron, I would love to have that spreadsheet, email it to me when you get a chance..


Thanks for all the help, keep the thoughts comming..

Scott