Anyone running the same gear as this or real close to it? I would like to know the engine combo and rpm going through the traps. I have a set of 5.13's but don't know what rpm it will go through the 1/4. I really don't want to have a short living motor. Two years ago with these same 5.13 gears with alittle less power ran 7.50's but the tachometer quit working and the very first pass which was a 7.56 right before the tach quit working I remeber seeing like 7800 rpm. We didn't shift into high gear untill like 100 ft away from finish line. Tire size is 29.5x10.5 hoosier measures 30.6 tall and 11.1 wide with a roll out of 96". The converter is a TCI 4,000 stall 10" but is starting to losen up over time because it would only go to 3200-3500 at best now it goes 4000-4200. I think the tach was probaly pretty close to right because the motor sounded like it was turning some rpm. It was an old moroso mechanical tach.

I run mine in the 1/8 and shift at 6800 and cross the finish line at 6700-6800. It has 5.14 and a M/T 315 60 Drag Radial, about 30 in tall.

Does anyone think 4.88's would be the better and safer choice for a 11 or 10 sec car?

That's easy.. You can roughly figure out how much hp you will make then gear accordingly to the the max rpm the engine is good for.

Or you can run the engine with too much gear, blow it up and drop down one gear size at a time til you stop blowing up the engine..........

I have a question for you?? Are you for real or just pulling our chains???

Nobody can answer your question without knowing a lot more about your motor. Are you taking Dana or 8 3/4"? At what rpm's are your peak horsepower and torque? Do you really want to go 7600 rpm's and only run mid 7's in the 1/8th? What kind of mph and 60' times? How heavy is your car? You need to consider all of these factors. If you have an 8 3/4, I would go in the other direction with the rear ratio and see how it affects your ET. It sounds like you may be reving that motor past where it's pulling and it's not helping your ET?

Well right off the bat if you have gained 1000 rpm of stall with the same engine combo, your converter is pooched. You need a new tach too.

Without engine/car combo details nothing else much useful can be done here. Just because it will turn 7000 plus doesn't mean it is doing anything there but making noise.

Kevin

The engine combo is slightly different but not sure if it's just a hp thing pushing the stall up or the converter is balloning?

No 10.90 racer I am not trying to screw with anyone. I am also not trying to do that approach by blowing engines. I'll be the first to admit I can't afford it and heck I can't even afford the motor I got now!!

It's an 8 3/4 rear with high quality parts. Mooser full spool and Mooser 35 spline axles. We tried a 4.30 gear but had the be the worst move we have ever made on the car. The car's combo is just a stock 340 with some w2 econo heads worked over alittle bit with some trw 13:1 slugs. It has steel rods and a very heavy 8 bolt crank. Just a mechanical flat tappet cam that I really know nothing about and ductile iron rockers. We are currently running 1 5/8 headers which we will be changing. It had a mechanical fan, water pump, fuel pump and alternator and a edelbrock 750 carburetor on it 2 years ago. Also a real messed up fuel system with 5.13 gears and ran a best of 7.56 with a 1.65 60 ft with alittle bit of traction issues. Over that winter I changed the following: Electric water pump, Electric Fan, Took off alternator, changed carburetor to a proform 750 street series it's black and silver and we did some work to it. Probaly only made it worse but we ran it anyway. Also added a intake spacer 2" aluminum open, Adjusted valves, and made some suspension tweaks and fixed the front end alignment and last but least we changed the rear end gear to a 4.30. We only got 1 pass which was bad so I have no real good data but the car went 8.00 at 87 was in 1/8 and 60 ft was 1.75 and 12.65 at 104 in 1/4. Car spun and we had the shifts messed up and a couple other small things but even if it didn't break the very next pass on the line like it did it would only run like maybe a 12.20 at best. Plain and simple it wasn't getting out of the 12's with that gear!!! I can't say it for a fact but I highly doubt that the 4.30 gear would work behind our combo. I hope this made everything alittle more clear?

I don't know peak hp and tq. Motor has never been on a dyno. The cam is post to be 606 lift. We are going to put a dial indiactor on and find out what it really is.. We are also going to hopefully run a leak down test and do some other stuff like check valve springs and probaly look at bearings and stuff.

We have a new tach now so that is taken care of also has a shift light but probaly need to change the light because blue is not to bright and won't blind you at night but you can't see it in the day time worth a crap!!

When you put the dial indicator on the retainers to see how much lift you have take the time to record the duration at .050 from oepning to closing, in other words watch the dial incator , when it reaches .050 on the opening write down the numbers it has before or after top dead center and the same on the closing, write down how much after bottom dead center it reaches .050 before closing. Do both valves, intake and exhaust and post the results on here We will be able to to tell you exactly what the duration is at.050 and how much, if any, the cam is advanced or retarded BTW, you will need a piston stop and a degree wheel, you will probally need to take the crankshaft pulleys off to mount and set up the degree wheel As far as your results with all those changes, it doesn't suprise me that it spun the tires and didn't run as good as it did the firts time I would put it back, the motor parts, not the gear changes, and see if it runs as good as it did the first time If it does don't make any other changes until you max the tuneup and set up you have that runs good Once your thier then do ONE change at a time, not a bunch of changes I've seen .25 canges in E.T. by swapping accelerator pump squirters Lots of things to try on race cars, more better change them one at a time

Thank you for the advice we will check the cam like that. Only thing I can't do is put the 4.30's back in unless I buy another set. They got destroyed when a bolt decided to let loose that holds one of the caps in place that's part of the spool assmebly..

FWIW, I've run 4.56, 4.88, 5.13, and 5.57 gears under my car. In the 1/8th mile the difference was so small it wasn't worth the effort. It's been years since I've run any steep gears in the 1/4 so it's hard to say. I currently run either 4.56 or 4.88 and it likes it just fine in either the 1/8 or 1/4.

I like the 5.13 because its a good all around gear. RPMs don't change much because of tire growing. More gear helps a tight converter. Depends on how much money you got to start trying all the different conv. and gear combos.

I think in another post you said the car weighed less than 3000 lbs. If so, and you run 104 MPH in the 1/4, you are only making about 300 hp or so. I would forget about the rear gear for now and figure out why it is so down on power.

The car is 2600 lbs w/o driver and about 2800 w/d. The car is down on hp with out a doubt!! It needs a better carburetor like a holly 950 hp instead of the junk 750 proform street series we have on the motor now! It also needs a way better set of headers. The ones that are on there now are only 1 5/8. They are very restrictive!! The timing needs tuned in. It may be way off because we never got a timing light on it. Not sure if the 2 inch open aluminum spacer is hurting performance or not? Will have to try it some more and try another spacer that's only 1 inch but it's a wood open spacer. Then try it with no spacer. The 4.30 gear really hurt performance alot by bringing the engine rpm way down. It needs a 4.56 gear or more and even with a 4.56 it still won't be that great! I have a set of 5.13's sitting in the box from when we were 1/8 mile racing and it won't cost me anything to put them in but I am giving it some series thought on going to a 4.86 gear..