Which gear to run in 1/8th mile 5.13 or 5.29

429 cid with cast iron mild ported heads solid flat tappet cam 643 intake 666 exhaust. duration@ .050 258 intake 264 exhaust 108 lobe seperation installed on a 104, c-4 trans 4800 stall speed converter 11.5:1 compression victor intake 1050 dominator 3400lb car 31" tal tire on 14" wide rim. has 4.86 rear gear in car now. Turns engine 6500rpm and shifts in to high gear about 100 ft before the lights. 1/8th mile car.

What kind of mph is it running now

92mph is average 93mph is best

I think this guy has given you some miss information. Or that torque converter is locking 1 to 1 down track.

6500 @ 7.09 Final drive 100 ft off the line. if you figure in 10% slippage on that heavy car that puts it at 76 mph.

It would be hard to pick up 17 mph in 100 ft. even locked 1 to 1 it would have to pick up 9 mph in 100 ft.

If your wanting it to trap at 6500 in high gear through the 1/8 your going to have to put a way steeper in than a 5.29. More like a 5.86 from the info you have from him. that would put it close to 93 mph.

JMHO.

IDT-572 wrote:I think this guy has given you some miss information. Or that torque converter is locking 1 to 1 down track.

6500 @ 7.09 Final drive 100 ft off the line. if you figure in 10% slippage on that heavy car that puts it at 76 mph.

It would be hard to pick up 17 mph in 100 ft. even locked 1 to 1 it would have to pick up 9 mph in 100 ft.

If your wanting it to trap at 6500 in high gear through the 1/8 your going to have to put a way steeper in than a 5.29. More like a 5.86 from the info you have from him. that would put it close to 93 mph.

JMHO.

Ok got some more info ! I have found out that at those times and mph and a 1.70 60ft time he was not getting full throttle. That issue is now resloved. Hughes 10" converter. ( I advised him to get a 8" 5000 to 5500 and leave the gear alone).

Mike,

Try this formula and see if it helps,..........



How To Select The Right Rear End Gears

#1

Shift Point x Tire Height
336 x Trap Speed


*Multiply your shift point by your tire height
*Multiply your trap speed by 336
*Divide top number by bottom number
---------------------------------

#2

5500 x 30 = 165,000
336 x 130 = 43,680

*In this example, your shift point is 5500
*Your tires are 30 inches
*Your trap speed is 130 mph
-----------------------------------

#3

165,000
43,680

Result is 3.78

*Multipling 5500 RPM by 30 inches gives you 165,000
*Multipling 130 MPH by 336 gives you 43,680
*Dividing 165,000 by 43,680 gives you 3.78
-------------------------------------

#4

Gears available for 9.75"/8.8" rear:
3.08
3.27
3.55
3.73
4.10
4.30
4.56

*From here, you simply select the closest gear available to 3.78 = 3.73

Thanks Keith

4.86 is more than enough gear IMO.the converter may be the issue but 8" in that weight car aint the answer.i run 4.56 with 33"tires,glide,and a 9" 5000 converter.

cool40 wrote:4.86 is more than enough gear IMO.the converter may be the issue but 8" in that weight car aint the answer.i run 4.56 with 33"tires,glide,and a 9" 5000 converter.

What size engine were you running with that set up ?
I didn't think about the weight of the car when I suggested the 8" converter !

whitefield wrote:

cool40 wrote:4.86 is more than enough gear IMO.the converter may be the issue but 8" in that weight car aint the answer.i run 4.56 with 33"tires,glide,and a 9" 5000 converter.

What size engine were you running with that set up ?
I didn't think about the weight of the car when I suggested the 8" converter !

526 cid. i'm looking at the rpm your turning and it should be in high gear way before it is,IMO.all i ever ran was 4.86 gear till last year.i had a 400m,c4 before and footbraked 6.80@102mph all day.is your 429 slow to rpm?

It's not mine it's a customer so I really can't tell if it's slow to rpm. We are going to take it to the track next weekend and do some TNT weather permits . I really think it needs more stall speed on the converter !

whitefield wrote:It's not mine it's a customer so I really can't tell if it's slow to rpm. We are going to take it to the track next weekend and do some TNT weather permits . I really think it needs more stall speed on the converter !

does it realy go to 4800? transbrake? i'm sure you'll have a good idea when you see it run.

Went to the track for some TNT ! With the throttle issue fixed car went 1.64 60ft and is a true 4800 converter launched at 4500 shifted at 6500 .went consistant 7.67 at 94mph. Ran in the 7.60's all night and 0ne 7.70. So I think the gear is fine ! What do you guy's think ?

Honestly..... It sounds like a pig.....

3400# and the et Is about 425-450 hp.

dfree383 wrote:Honestly..... It sounds like a pig.....

3400# and the et Is about 425-450 hp.

Yeah it is ! The Rpm doesn't come up quick at all going down the track but revs very quick in park! I think the converter is suspect !

To much cam...........

IDT-572 wrote:To much cam...........

Blake's on to something......

if your on the brake and leave @4500 the converter aint the problem.

cool40 wrote:if your on the brake and leave @4500 the converter aint the problem.

So a cam change and keep the same converter ?
I guess I was looking at it the wrong way . I thought the converter might not be letting it get or take off at its torque peak . I also thought that even though it was stalling at 4800 and launching at 4500 that it was not multiplying torque. I also was thinking that the weight of the car and size of tire would make it appear to be a higher stall the same way a truck does when you put a load be hind it.

I figured a 8" 5000 to 5500 would be a better converter for that small of cubic in engine or even say a 9.5 5000 to 5500.

The weight of car is 3400 lbs with a 230lb driver.
So which way do we go with this thing ?

whitefield wrote:

cool40 wrote:if your on the brake and leave @4500 the converter aint the problem.

So a cam change and keep the same converter ?
I guess I was looking at it the wrong way . I thought the converter might not be letting it get or take off at its torque peak . I also thought that even though it was stalling at 4800 and launching at 4500 that it was not multiplying torque. I also was thinking that the weight of the car and size of tire would make it appear to be a higher stall the same way a truck does when you put a load be hind it.

I figured a 8" 5000 to 5500 would be a better converter for that small of cubic in engine or even say a 9.5 5000 to 5500.

The weight of car is 3400 lbs with a 230lb driver.
So which way do we go with this thing ?

if it aint peaked by 4800 with that cam it never will. i'd degree the cam to see where its at before i changed it.it could be a lota things.lol,but slow rpm sounds like a retarded cam.JMO

I'd get a cam and lifters for it.

Its not enough compression for that big of cam and it to big for the operating range your looking at.

dfree383 wrote:I'd get a cam and lifters for it.

Its not enough compression for that big of cam and it to big for the operating range your looking at.

Its about 15 degrees at .050 to big and needs to be on 105 or 106 seperation if you want it to really run good. You have no cylinder pressure , cam it like a 4v clevland. Small engine big head . People that say a 4v cleveland wont run dont now how to cam them.........ii

I think a gear change , and some seat time and he will be set. don't touch the cam just yet. that is where alot of guys mess up is changing to much stuff . fine tune what you got. may need a converter also.

Where most guys mess up is throwing a bunch of mismatched crap together and expecting it to fly instead of carefully thinking out the build and exactly what they want. A gear change ain't gonna help much if the engine ain't working right. I think the gear is fine, sounds like a cam problem to me.

wild pony wrote:I think a gear change , and some seat time and he will be set. don't touch the cam just yet. that is where alot of guys mess up is changing to much stuff . fine tune what you got. may need a converter also.

I agree you just want to change one thing at a time, and it obvious the cam is the item to change here. Leave the gear and converter alone take some cam out of it the stall will come up higher with the extra torque and the car will 60 better and also et better.

It,s got a cam in it suited more for a 13.1 472 than an 11.1 429 with a 3.59 stroke.

Just trying to help, but I guess, what I say is falling on deaf ears. I will refrain from commenting farther in fear of messing up.