cagotzmann

1978 corvette. I am in the position I need to pull my TH350 due to some leaks. I will be using this car for Road Track days and unsure if I should fix and rebuild the auto or install a Keisler RS600 (5 Speed). I am happy with driving a auto with manual shifting, but is there someone that has made a switch in the C3 from auto to manual and notice better lap times with a manual. Now this will vary track to track. Other than driving fun with a manual is there other things to consider such as reliability, acceleration lag etc.
Anyone running th350 for road track days. Engine is a stock 1978 350 with an upgrade to a LS3 or ZZ383 coming up.

Current VB&P salmon kit, with HAWK racing PADS (Stock brakes)
new tires will be 18" michelin super sports.

Thanks looking for suggestions.

Not interested in winning races vs C6's, but looking at making my C3 as much fun and getting the most without just spending money with no gain.

bosco022

The improved gearing of a 4 or 5 speed will easily make for solid improvement in lap time. The cheapest, new, suitable 4 speed would be a Richmond Super T10 at about 1800.

Another issue you have is that you likely have something like a 3:08 gear. Which is not optimal for most road courses except Daytona.

This is likely gonna be a fairly expensive move to go to a manual as you will need the bellhousing, high perf clutch, pedals, plus the tranny and something like the Hurst billet speedway shifter.

If you are pretty sure you are going to continue tracking you might want to consider selling this C3 and find a more suitable track car. There have been some prepped C4's on here at more than reasonable prices.

Scooter70

Been there, done that, bought a Z06.

If you want to continue tracking that car, I would ditch the automatic and go to a manual. The Keisler kit seems to be a decent way to go but it's not cheap. As Bosco said, there's a lot of little things that will add up (pedal assembly, clutch, Z-bar, driveshaft/u-joint may have to change, shifter). You'll be into the swap for at least $2500 and probably won't be any faster or more reliable other than avoiding overheating the automatic. I'm sure it will be more fun as well.

However, here's my story:
I had a '70 coupe that I tracked for years. It was just a base 350 with a M20 4-speed, lots of VBP parts, and some R-compounds. It spun a bearing at Watkins Glen in 2003 so I swapped in an LS1 and T56. Tracked it a few more times and quickly came to the realization that I was still working on it 4 hours for every hour of track time and I was slower than friends in Mustangs at the events. The car was good and it was fun to drive but it wasn't great. I wanted to get to the track, drive, and not have to spend the day working just to turn slow laps. After a few years in a 2005 GTO I finally stepped up to a C5 Z06 and haven't looked back. I kept the '70 as a garage ornament for a few years and just sold it a couple of months ago.

You have to ask yourself whether you like driving (and working on) the '78 or whether you want to go fast and work less.

-Matt

J.R.

Look at Tremec TKO 600

You can run a 0.64 or a 0.82 5th gear.
It has also has 2.87 1st, which will help with higher ratio rear gear.

I believe American Powertrain/Keisler/D&D all make conversion kits for the
C3 application.

cagotzmann

At this point I feel I can work on my 78. I think I have almost touched every part of the car during my 32 year ownership. I am not sure I can / or will be able to work on the newer corvette's. But last year I almost sold the 1978 for a 2007 Z06. Its hard a sell a 78 up here in Canada. I dont have room for 3 corvette's. I am now thinking about starting with a GrandSport of some sort. Waiting for something in the 35k ranage. Up here in Canada they still think 2010 GS are worth 59k.

I have been quoted 5k which is about 6k(cdn) with shipping and duty etc, for the complete conversion kit. I just wanted to know if someone has gone from auto to maunal for track use, and seen a real difference. I also road track /daily driver my 2010 GS so there is no rush making a change. But since I needed to pull the auto to fix a leak I was not sure I want to do it twice.

Thanks...

cagotzmann

Yes they all have kits, just asking if someone has made the change and noticed an improment before I do the same. If it doesn't provide improvment I am not likely going to make the change. I only improvment I do know is simply the enjoyment people like with manual transmissions. I myself like auto's with paddle shifting. Know one makes a C3 transmission with paddle shifting that looks good. and is more than 3 gears. Any of the 4 speed auto have the same gears as a 3 speed with overdrive. Any of the tracks I have access to I will never use and overdrive. Max a 1-1 ratio. Top speed of faster cars on my track is about 110-120 MPH on the straights. Laptimes are around 1:35 for fast cars. I run 1:50 with my stock 78 on bad T/A 255 tires.

Jason Staley

I don't have any times comparisons between transmissions because I swapped in a Richmond 5 speed before going to any road course tracks, but I wouldn't try to seriously track any car with a TH350 IMHO. I don't hate TH350's at all, and I have a highly modified one in my drag racing car. It's just that trying to drive one on a road course to me doesn't seam like much fun, and I would be concerned about the reliability of the transmission in two main areas (1) over heating, which can be helped by adding an transmission oil cooler (coolers), and (2) wearing out the Intermediate Band, which can be avoided by not downshifting to slow the car down.

If you go the manual route, here are a few things to consider:
(1) Your going to have to cut the transmission tunnel for the shifter. Not a huge job, but still is worth mentioning.

(2) If you go with a mechanical clutch linkage (i.e. factory), Mr Gasket sells a heavy duty push rod for the clutch to reduce flexing. Also get some polyurethane motor mounts too. A mechanical clutch applies an axial load to the engine mounts and the stiffer poly material helps with clutch disengagement.

(3) Get a steel bell housing for protection. You don't want the clutch/flywheel if it explodes to take your feet out. Quicktime sells a good one that is SFI approved and doesn't hurt ground clearance (Quicktime). Note that this bell housing requires the smaller 153 tooth flywheel and 10.5"clutch combination.

(4) If you get an older style transmission with external shifter, get a Long's shifter instead of a Hurst or similar type of stamped steel construction. The Long's shifter greatly improves the ease and precision of shifting the older type of transmissions (ie. Richmond, Saginaw, ...). They are expensive, but well worth the extra money.

Also, the Richmond 5 speed gear ratios work really nicely with a 3.08 rear end gear. I mainly use gears 2-4 while I'm on the track giving me a top speed just over 120mph. If I go back to Road America or another track with long straights I may see how the car does in 5th, but my local track just isn't long enough for me to use top gear.

Hope this helps,
Jason

cagotzmann

This is good info. I always was concerned about heating of a auto, since I do down shift before corners like you would in a manual. Adding a transcooler can help. I am looking at Keisler RS500/600 or SS700 which eliminates the need to cut the tunnel. But I will need to ask about their bell housing they include. I will compare the gears of the richmound to keisler see if they are close.

Thanks....