_Remi

Hi friends,

Quick description of my problem that some of you already know: I switched from stock to performer aluminium heads on my 289 (other small mods in my signature) and although I have some good top-end power, I don't have any torque and it hesitates at low rpm. I am still using my stock cam, which everyone agrees to say that it is wrong and I am planning a change.

However, I was wondering a little more about gear swap which, for some reasons, I tried to avoid. Let me tell you why

I had my engine rebuilt and I put a T5 in it at the very same time. I loved the feeling so much (especially on the 3rd / 4rd gears) when, at that time with stock heads, I had a nice torque and was able to do long and nice accelerations. I though that changing gears (I have I guess 2.79) would make my first and second gears way too short.

I know about the basics of gear swap (highway vs street) but I am wondering how it affects the way you drive a stick shift.

Am I clear enough?

It may completely solve my problem to go to 3.55 (better throttle response?)

Thanks,

EZFEED

3.55 for the win bud! Sounds like you should do some gear work.

1971mach1

I think you'll notice gears more than the cam. But you'll get worse gas mileage (If you care). But you also may be lugging too much in 5th anyway.
2.79 is tall for your 1st gear, 3.55 would have much more torque. Most t-5s have a
first gear of 2.98.
www.ringpinion.com has gear/transmission/tire size = rpm calculators.

Starfury

You should definitely swap out gears. 3.55's at the least, if not 3.73's. That T5 will let you cruise on the freeway all day with shorter rear gears.

Shorter rear gears will improve throttle response, but won't get rid of your hesitation. You need to figure that out separately.

kalli

re-read that 2nd line! your problem is not the gearing. hell ya it will be more fun (i drive 3.5:1 gearing with my T5 and it's good on street and highway), but it will not cure your original problem.
I don't think it is the gearing or cam. I believe it to be carb or ignition.
who adjusts your ignition? do you have or know someone with a timing gun?

kalli

_Remi

Thanks for your feedback.

I got some news about the car this morning. I had my new mechanic (performance engine builder with excellent reviews) checking the bottom-end and he told me that everything is fine (compression are around 160 PSI). I also have a new MSD distributor and new spark plugs. I believe that they set the timing correctly, however, they have not driven it yet (only I did) so maybe they will feel something wrong with it and adjust accordingly.

By hesitations I mean that I floor it and it does not sputter/misfire but, it does not come immediately and smoothly. Once again, I am waiting for my mechanic to drive it so that I can have a second opinion.

I was not feeling that before I had my heads changed, was it because I had more torque? That is the question!

Now I am seriously considering a swap from 2.79 to 3.55 but I am still wondering how it will affect my 1st, 2nd and 3rd gear (i.e. making them too short -> not usable).

Starfury

They'll be perfectly usable, although WOT in 1st gear is likely going to be nothing but a tire melter. Most people opt for lower gears than 3.55 with a 5sp.

kalli

are you sure you are running 2.79:1 gear in back? if yes, tell me what tyresize (ex: 225/60R15) you have and I'll give you statuistics (before/after).
Good idea to go somewhere else to get a 2nd opinion and congrats that your bottom end is fine. from there it'll be easier to fix your problem.

what could have happened is that the new heads have way less chamber resulting in lower compression. but 160psi is what i had with 9.5 compression as well. you can't calculate that way but gives an idea.



Kalli

_Remi

Do you mean that they go with 3.25 or 3.73? Low vs high is still confusing me

I have 225/60/15 front and back.

Thanks

Starfury

Lower gearing means lower ratio, which means a numerically higher gear. 3.00:1 is lower than 3.55:1, etc.

Lots of fox body guys love to run anywhere from a 3.55 to a 4.11 to improve performance while still being able to drive on the freeway. 4.11's are a little excessive, but I'll probably be looking at 3.93's for my car with a TKO conversion in the future.