I know this is a rather vauge question but lets assume, a 700r4 Camaro runs the quarter in 14.00 flat shifting at 5000 rpm, is there any way of knowing what kind of gains could be had by changing over to a TH350? I've drove cars with the TH350 swap and the lower first gear is hardly noticeable because the cars seem to feel lighter (less rotating mass?) even though they lose ration in 1st gear. I'm thinking this swap will give me some good gains because the car drops to about 3300rpm after the first to second shift with no slip and a decent firm shift.

 

I am not sure that there is an easy answer to that question. I have friends that converted from one to another with different result. I guess it would depend on the combination. The last conversion I saw was on a friends 90 camaro. He went from a 700 to a 350. Nearly no difference in et in the 1/4 mile. He was a bit disappointed.

 

That's too open of a question.

When I was still using a 383, I had a 700R4 with something like a 2000 stall converter. The engine had some really poor smog heads on it but had a good solid cam. The car ran 14.0

Over the winter, I swapped out the tranny for a TH350 with a 3800 stall converter. I also put on some old camel back heads that had a lot of port work and big valves all set up for the cam that was still in the car. Nothing else was changed in the car. First pass in the spring got me a 12.0 and I needed to install a rollbar before the next race.

How did I gain 2 full seconds? The heads were probably a huge increase but the tranny also helped.

 

That's really what I'm wondering, what gains people have seen after the swap. My setup is an iron head 350 TPI with the 87 roller cam, stock heads, stock injectors, ported intake, AC and smog delete, Walbro 255lph fuel pump running 49 psi, 1 5/8in headers to a Y pipe and a short 2 1/2in exhaust (dumping before the rear axle), standard steel DS with a 3.27 geared 9 bolt, stock 91 style 16in rims and tires. The car weighs in at 3400 pounds with me in it. I have a TH350 conversion kit, short shaft TH350, and 3000rpm stall with anti baloon plates. The trans in the car is a stock stalled 700R4 with upgraded clutches, band, servo, etc. etc. I think the TH350 swap is going to help alot because my car really doesn't like that 1 to 2 shift, I would almost prefer it spin the tires a little rather than drop as many RPM as it does and lug itself back up; that 1 to 2 drop is also pretty interesting on the nitro because it just fries the tires. My intention of this post was basically to gether info on what gains people have seen when they did this swap on there setup.

 

I have not seen any big changes no matter which way you go. I have a couple of my 4L60E's in the very low tens (10.20 - 10.15) at 132 - 135mph both in 1996 Firebirds weighing in at 3,350 w/o driver, doing extremely well. Rick Abare's should be in the high to mid 9's this season, & Ed Wright's soon to follow. So would a switch to a TH350 help?, I doubt it.

 

Th700r4 with corvette 2200stall 13.43@104.5. Changed to th350 with 3600stall B&M holeshot 13.01@103.3
Couldn't get a 12.99 out of it even with a tail wind.
This was a direct swap, same car same motor same tires, gear, shift points same track. 4 tenths consistant improvement.

 

Not exactly a "direct" comparison. You forgot to mention the difference in stall of the torque converter, and weight, and diameter of the torque converter (big difference). I've seen these differences alone just from a torque converter change, higher stall & a lighter weight torque converter. I still stand by what I said earlier. Did you notice that you lost speed with the new torque converter?, sounds like the TC was not "matched" to your particular setup.

 

apples to apples, isnt the th350 more efficient than the 700r4. therefor gets more power to the ground.

But then you gotta think about how much of that fist gear you loose, thats gotta be bad for the 60' times.

 

on paper it seems that it would help just abit.

3.06 first gear and 1.63 second, 1.00 third in the 700r4

Th350 is like 2.52 1.52 1.00. the tighter ratios in the th350 with the right gearing will keep the motor more in its power band.

5000rpm shift point in 700r4 is like 37mph for 3.42 gears
shift to second and rpms are just below 3000rpm.

for th350... shift at 5000rpm same gears tire.... at 45mph in first gear. shift second and rpms drop to just over 3000rpms.

with the right converter, it can be helped abit in favor of the th350 abit more.


the differences are kinda minor between shifts... but you ride first gear out longer.. so you can jump to a bit deeper gear if you want with th350's taller first gear