1st gear ratio ?
 

Question !!! I just bought an IHRA crate 85 z28 and i cannot get it to 60 ft the same as the last owner.The only change is the trans,same convertor i suspect the prob is i am running a 1.96 gear set and i am thinking previous trans might of had a different gear.Its a glide with a brake and 4.88 gears 60 ft is 1.48 and some old slips with car show 1.40 so just wondering what first gear ratio i should be running 2.08 or higher ? It is 350 330 hp car Thanks

Re: 1st gear ratio ?
 

thoughts to consider;

* more rear gear, at least 5.14 or even 5.38

* depending on number of runs on converter, might need to be checked, something could have changed

*tire condition?

* changing to a 2.08 low gear is a reasonable option, the thing is, doing so increases the RPM drop at the shift and lays the engine back on the converter until the driveshaft catches up with engine RPM. Thus, making the converter an even more important part of the package.



* also consider, you do not know the conditions the 1.40 time slip happened under. It could have been better air and track.

* And consider leave RPM in the equation.

Re: 1st gear ratio ?
 

Can't you ask the previous owner?

Re: 1st gear ratio ?
 

Old owner thinks his old trans was 1.96 i think he might be mistaking ! Def new convertor and i will try a 2.08 have to run 1/4 mile a few times a year so would like to keep 4.88 Thanks for the advise !!

Re: 1st gear ratio ?
 

Are the 60ft times you are turning done at the same track as the previous owner? Track times can be different in the way they set up the beams. Sometimes 60ft is not 60ft.

Re: 1st gear ratio ?
 

Sixty foot is not the number you should be comparing,smart racer's use 330 ft. Sixty varies too much day to day and track to track.

Re: 1st gear ratio ?
 

Same track and a good 330 for me is 4.73 and a good one last year for him was 4.58 it is now running 7.04 fastest pass and last year a fast pass would be 6.85 car is running the same mile an hour 94 to 96 same as last year !! Seams to be 60 ft only other change to car is a super victor from a victor jr !! Thanks Guys

Re: 1st gear ratio ?
 

Manifold may have hurt torque.

Re: 1st gear ratio ?
 

Almost certainly moved the power band up a few hundred RPM. At the very least.

Might be something the PowerGlide and current converter do not like. And will almost certainly not like a big RPM drop, a lower low gear set, say 2.08, may make it even worse. You shift sooner, at a lower tire speed and vehicle speed, and then try to accelerate with only the converter and the rear gear.

Re: 1st gear ratio ?
 

Do an A-B-A test of the manifold change at the track to check that out.
The 1.96 you are talking about probably uses the heavier V8 planetary.
Could the original owner be mistaken and had a 1.98 that is the lite weight 6 cylinder planetary?
There is a substantial weight difference, I'm talking major lbs...
It takes some time and HP to get that heavy planetary moving.
The 1.98 also has one of the best % drop in shift RPM of all the aftermarket ratios. Anything lower than a 1.98 has more than a 50% drop in RPM and becomes power and weight as well as converter sensitive. Just the difference in (both trans were tricked out with lt weight parts) the 1.76 & a1.98 in my 3175 lb 660 HP Camaro was almost .25 sec.

Re: 1st gear ratio ?
 

I knew someone sharper than me would have some answers.

Re: 1st gear ratio ?
 

I don't know where you are but the weather for us has been slow this year. Comparing log books from last year same dates to this year et's are slower as the weather has been hot and humid.

Re: 1st gear ratio ?
 

I'm in Ontario Canada and hot hear also which is prob playing a part ! Thanks everyone for the help!

Re: 1st gear ratio ?
 

What Motor do you have?
330 hp Vortec head in my car. Powerglide 2.10 low gear, 5.38 rear and a 94 inch circumference rear tire and you should make the 1/4 mile finish line.

Re: 1st gear ratio ?
 

Yes 330 hp car, i will check tire size i cant remember off hand,i'm not looking to brake records but think car should run 6.85 on a good day ? How fast are these cars going with 385 hp motors ? I am new to this crate motor stuff thanks

Re: 1st gear ratio ?
 

Yes, .85 is respectable in the 1/8. But , its all relative, depending on class. 3rd Gens with a 330hp generally run F G or H. In H 6.85 is fast, in F, not as much. How much does the car weigh?

Re: 1st gear ratio ?
 

Sorry for the delay i felt i should scale car before replying,so 30 inch tall tire and car is 3288 lbs with me in it !!

Re: 1st gear ratio ?
 

Why are you trying to run a power glide with a trans brake? Are you running it in stock?

Car would be much better with a metric 200.

Re: 1st gear ratio ?
 

Im curious as well as to why youre running a transbrake, and if so, why you would inform us. Only if you are just running brackets with it then that's fine. I run the exact same combo and ran previously a glide, but now I have a th350 and the 60' times are much better, putting my metric in this week though with a 2.74 low. Your car is very heavy for what it can be, im at 3077 with me in it running F and I don't have any weight anywhere except for the majority in the drivers seat!! My converter stalls at exactly 5k which took me about 4 different converters to finally get the right one in the car. With a 2.75 low gear, shifting at 6500, and 5.38's my shift light comes on about 100-150 feet before the 1/4 mile finish line.


If you are running it in stock, what class do you plan on running? The 385hp guys are low 6's on average from what I've seen.

Re: 1st gear ratio ?
 

The car was being bracket raced when i bought it and that is what i am doing with it also,the car was going 6.85's in good weather but the guy kept trans and convertor which was a glide ,so i now have a reid case and a 5800 stall with 196 first gear,i will check the actual stall this weekend,car has h/cm on window,there is a national open near me that i thought i could run the car in but maybe i can't with the glide ? I would like to go a bit faster that's why i was thinking 385 hp combo and that would still keep the car close to legal for ihra if i decided to sell it some day thanks Guys ! Once again i am new to stock,crate motor stuff i just bracket raced !!

Re: 1st gear ratio ?
 

at 3288 you would be in G/CM, I tried a fast burn once and it was only a tenth faster than I have been with the vortec head motor . I will admit there was more there with the fastburn but I didn't pursue it farther.