3.55 or 3.80 Gears

Trying to select which ratio.
for a stock rods and pistons, ARP bolts, Stock stroke and bore.

Street car but needs to be quick. That was the whole idea of the build up.

My max cruising speed is normally 62 in the 55 mph zone. We dont have any 65 mph zones around.

3.55 @ 65 mph = 3122 rpm
3.80 @ 65 mph = 3342 rpm

Is cruising at 3300+ rpm ok for these motors for extended distances (1 hour say). Im guessing it is cause i cruise my big block olds at 3,000.

Any input is appreciated.

Thanks
tim

 

I would think 3.55 is the max you would want for a street car. I put a 3.25 in mine ...

 

i would think you would be okay with either one. not really that much difference in the rpm.

 

I like my 3.55s and would not go any higher, and 3.40 is the lowest (numerically) that I would want.

My engine turns 2900 @ 60mph with 25-inch tires...

 

You know what they say about opinions..........here is mine. Go with the 3.55. They will also work great if you choose an AOD or 5 speed with the mild motor.

I had 3.89 in my truck and 3.73 in a chevrolet I owned. I didn't like either one. It was too steep for the street and not steep enough for the track. BTW, I switched to a 3.50 for a while in the truck and finally found that I preferred a 3.25. Corvette was sold. Both of these had small 26" tires. 3.80 might be OK for cruising if you had some BIG tires. I had 3.50 in a Cougar for a while with 245/60/15 tires and it drove it to work daily for a while. Worked OK at 60 MPH cruise.

Cleaver

 

I guess you figured rpm with your tire height?
Those gears you are looking at are very close, so it doesn't matter much, however I think that more detail is needed if you want to get down to the absolute best for your car.

If you are more worried about the engine life and you drive often at cruise speed for an hour, the 3.55 would be the best compromise. Also best for fuel economy.

If economy and cruise rpm are no issue for you in general, the 3.80 could possibly be the better gear for your combo.

If you are still interested in the 3.80 gear after taking these into consideration, we should know the cam duration @.050", what intake, what carb, headers, and tranny specs...

Dave

Edit:
Brain fart!
I should have read your sig...
Going by your sig, the 3.55 would be good, but the 3.80 would be better if you can stand the extra little bit of gear.

 

Tire size would be very helpful
I runb 3.40s with 26 inch tall Mt drag radials. 65 equal 3300ish give or take 100 rpm. I would love a set of 3.80s asI think it would be more suited to my new cam:evilsmile and my current converter

 

You shouldn't have 3300RPM at 65 with 3.40s and 26-inch tires. Your tach or speedo must be off (probably speedo)....

 

I run right at 60 mph and 3000 rpm with 3:89s.

 

RPMS were calculated from this gear calculator.

http://www.davisracing.com/CALCULATORS.htm

My tire size is 195/75 R14. Im using a 25.5" tire diameter.

Im gonna use the C4 to start at least. It would be nice to choose a gear that would work with an AOD also, but thats not my primary concern right now, but something to keep in the back of my mind.

Im somewhat concerned about the engine longevity of cruising at 3300 rpm. IM not concerned about economy. Im still considering a stroker right now and have to decide soon, cause keeping the 302 will cost me about 50 hp im guessing.

My first "dream" for this car is a SLEEPER that would run with a newer vette. After doing some research, i realize thats probably not going to happen so ive lowered my goals. If i could come up with a combo that could run high 12's i would be very happy. That should take care of most newer "sports cars", all "rice" and most "muscle cars" around here, anyways.
To put things into perspective, i wouldnt expect to put more than 3000 miles on this car a year. Probably more like 1000. Cant see owning this car for too awful long, as i like to try different toys.

The specs in the sig are what ive purchased already. The motor is still apart waiting for me to decide whether to stroke it or not.

 

From what the engine is going to have in it and you going to a 3.50 or 3.80 gear you are going to have to look at the tires you are running. With the tires you have and the engine combo you have all you are going to do is put burnt rubber in the air. The car probably will not even move under full throttle at a dead start, just sit there and spin. If you want it to do great things when you are done you need to think the whole thing through. As all of us drag racers know, when you spin a tire it is just like putting your foot on the brake. Your ET will be slower but your MPH goes up. The best all around street/strip gear in my opinion is a 3.70.

And everyone else, just my

 

Tires, drag shocks and suspension bushings are on the list after the engine and drivetrain get done.

Thanks

 

I ran through the same delimma a couple years back, and finally decided to live with a few extra rpms on the highway and gain a little power at take off...I went 3.80 with a spool.

I figure that I do more taking off than I do long highway drives, so may as well make it perform better down there.

I run 255/60r15 (that is somewhere around 26" tall) and really, I just cruise at 3000 rpm, right around 55 or 60, not sure which because the gears messed up my speedo (still works, just not the correct speed, even with a new speedo gear, close, within 5-7 mph). I have done 75ish mph on the highway for long periods at just under 3500 rpms, and it never made much of a difference...just purred along with just under 20 mpg.

I figure that when I rebuild my engine, it will be able to handle 6000-7000 rpms safely, so cruising at 3300rpms won't even phase it...

Honestly, just personal preference. I had a guy willing to sell me his 3.55 because he thought it was too high for regular highway driving.

Fordmaster is right about taking off. THat is why I went with a spool. Even with 2.79 gears, if the road was even a little wet, I could not take off without spinning all over the place. I wanted both wheels moving when I accellerated.

Oh, yeah, for everyone about to argue for/against the spool, let's not jack this thread...just post the links to those threads so we can stay on the 3.55 vs. 3.80 track here, OK? :Handshake We can then jump to those threads to read about those arguments...

 

i know this is off the subject but i think if your looking for 12's in a street car you'll need more than the stock bore, stroke , pistons, etc. jmo