i have seen a few different kits to convert my 78 with th350 to a 5 speed but theyre all pretty high dollar, well over 3500 with 2 over 4000. is there a more economical way to do the changeover? the motor going in makes right at 450 lb ft at the wheels running through a th700r4 in the truck it's coming out of. i dont plan on drag racing, no fat sticky rear tires...........running a 225/70 on it in fact.

have you considered getting that 700r4 with it, put the whole thing in your car..there are a few of us that have converted th350 s and th400 s to the 700r4 in our cars.. we are all pretty happy with them.

A TH700R4 is very easy to upgrade so it will handle a LOT of torque. I just overhauled one and put it in my big-block '71. All it takes is an aftermarket 3-4 clutch pack (either a 8 or 9 disc), an increase in line pressure ($10 worth of springs) and Fairbanks servos.

the 200r4 is the one that came in the grand national/gnx/t type regal and the monte carlo ss and is the same length as the th350 so i woldnt have to get rid of the carbon fiber driveshaft thats in the car. i got to drive a G-Force T-5 equipped 81 yesterday that got me thinking about a 5 speed. i actually have a 200r4 thats built to handle 550 lb-ft ready to install already but i liked the 5 speed.

i have seen a few different kits to convert my 78 with th350 to a 5 speed but theyre all pretty high dollar, well over 3500 with 2 over 4000. is there a more economical way to do the changeover? the motor going in makes right at 450 lb ft at the wheels running through a th700r4 in the truck it's coming out of. i dont plan on drag racing, no fat sticky rear tires...........running a 225/70 on it in fact.

i have decided to go to injection on my 78 and i've looked at several options one of which is the GM Tuned Port Injection. i have had enough of tuning and tweaking of the carb and though i can spend it, if i dont have to drop 1500+ into the Professional Products ez-tune if i dont have to i wont. the motor is an l48 that is getting 64cc chambered heads and a mild hydraulic roller cam and either a 200r4 or a 700r4 is i can get one cheap enough to be able to buy a new driveshaft to replace the carbon fiber one in the car now. i am not looking to make much over 300-325hp with mileage and driveability being more important than all out power (other than when hauling a motorcycle trailer or bags of feed this will be my daily driver) reliability being #1 and mileage #2 priority.

Looking at the two posts it looks like you are on the road to deciding which way to take your Vette. Here are some of my ramblings on the transmission and injection/engine;

I have a 74 L48 with a close ratio 4 speed. It is great jamming through the gears around town but when I go out on the highway I am looking for another gear at 65 mph. I have contemplated the T5 or T56 swap out and will probably do it when I rebuild the engine in the next year or two. Besides obtaining the transmission with bell housing I am looking at clutch/pressure plate/throwout bearing ($350-500), cut down driveshaft, speedo conversion or mod, and trans crossmember (I hae to cut mine out). With an Auto trans setup you can unbolt it from the frame. With the Auto you also have to look at pedals, clutch controls and modifying the center console to get a manual tranny to work if you are going to make the auto to manual conversion.

IMO if I had a car that currently had an auto tranny I would look at the 200r4 or 700r4 and I would put a ratchet shifter in. Converting auto to manual has additional headaches that are not worth the hassle. If it were manual to auto that would be a little different but it would still be a hassle. As far as the manual transmission you need to look at one designed for the HP/TQ that your motor puts out - I almost pulled the trigger on a T5 that came out of a V6 S-10 but I was talked out of it buy a mechanic buddy of mine. The S-10 tranny will work but there are a number of parts that need to be changed out internally if you have anything stronger than a stock L48.

Injection is another matter. I like the modern computer controlled injection but I hate the sensors (that fail). The initial cost and set-up of an aftermarket injection system is a bit prohibitive to me. I would take the $$ that I was going to put into the injectors and do a rebuild on the L48 to get the bottom end bullet proof and then either do headwork to the iron heads if I wanted to keep the original heads. If keeping the engine original is not a concern than I would put a set of aluminum heads on it. A good cam that does not go over .500 lift on intake would still produce enough vacuum that you would not run into any issues. Then I would put an Edelbrock or Demon carb and tune it on a dyno. Once tuned it should not need to be tweeked or messed with unless something else is changed on the engine. The cam and headwork can allow you to dial in your desired HP. As HP goes up the street drivability and economy goes down.

On the other hand I have a buddy of mine with a 82 that he has pulled the oil burning, wore out 350 and put a 305 in. It has had the headwork but he has retained the cam and tweaked the crossfire injection. It has more power than stock and gets 20+ mpg.

I have a buddy with an '82 that he pulled the oil burning worn-out 350" and put a 305" in.




Are you kidding me? I have never heard of anyone putting in a SMALLER engine. Bigger yes but never smaller. That's almost un-American.

I m with Toobroke, he put a SMALLER engine in? Blasphemy! should have bought the honda civic...as to having to constantly be tweeking and tuning carb,if you get it right to start with, it should stay in tune... I ve not had to touch my Quickfuel in 2 years, after initial dial -in.

Toobroke & Fishslayer, I agree about going smaller but he had the 305 and it was supposed to be a short term fix until he rebuilt the 350. With the gas milage he got he didn't want to go back. The 350 has been sitting on a pallet out behind his barn for at least 10 years now.

hey, we re just screwing with you...if it worked out good for him, great. We just always want "MORE POWER!" but in reality, I do get almost 20mpg with mine!

hey, we re just screwing with you...if it worked out good for him, great. We just always want "MORE POWER!" but in reality, I do get almost 20mpg with mine!
I am happy when I can break 10mpg...

Just rec'd e-mail from Keisler. Look at the RS conversion. $150 discount if ordered before the 30th. I would do the engine as suggested and raise compression. Keep in mind the torque curve for the lower engine operating rpm with 0.67 OD in 5th. Corvettes should be required to have manual transmissions!

I am happy when I can break 10mpg...
really, wow! thats not good..my stock set up got about 22mpg hiway..now I ve got over 500HP and in OD on hiway, I do right at 19-20mpg...now if I open it up, its more like gallons per mile! BUT ITS SOOO WORTH IT!

really, wow! thats not good..my stock set up got about 22mpg hiway..now I ve got over 500HP and in OD on hiway, I do right at 19-20mpg...now if I open it up, its more like gallons per mile! BUT ITS SOOO WORTH IT!


I recently overhauled my '71's 454" and then I threw in a rebuilt TH700R4 behind it. My first 150 miles of stop-and-go driving with speeds seldom going over 55 mph gave me 12.9 mpg. So I'm sure the mileage will go up to 18 mpg or better when I can run it at a sustained 65 mph on a freeway.

really, wow! thats not good..my stock set up got about 22mpg hiway..now I ve got over 500HP and in OD on hiway, I do right at 19-20mpg...now if I open it up, its more like gallons per mile! BUT ITS SOOO WORTH IT!

Totally stock L48 with 47K miles on it - 14 years in storage. Cylinders 1 &4 are lower on compression than the rest and the spark plugs for 1&4 are fouling with oil - I clean or change them every other month but I only put about 300 miles a month on it now. I am burning a quart of oil about every 900 miles - I finally got all of the leaks stopped but I have a few other issues due to the storage. I also drive with a heavy foot.

On the bright side I am planning a overhaul for this engine in the next 6 to 9 months (I travel a lot w/ work). I am also planning a T5 or T56 tranny upgrade when I overhaul the engine (radiator, fuel lines, and gas tank vapor canister - it has a recent fuel tank). With a fresh engine in the 300-350 hp range and overdrive I am hoping to get much better MPG with the additional performance.

Totally stock L48 with 47K miles on it - 14 years in storage. Cylinders 1 &4 are lower on compression than the rest and the spark plugs for 1&4 are fouling with oil - I clean or change them every other month but I only put about 300 miles a month on it now. I am burning a quart of oil about every 900 miles - I finally got all of the leaks stopped but I have a few other issues due to the storage. I also drive with a heavy foot.

On the bright side I am planning a overhaul for this engine in the next 6 to 9 months (I travel a lot w/ work). I am also planning a T5 or T56 tranny upgrade when I overhaul the engine (radiator, fuel lines, and gas tank vapor canister - it has a recent fuel tank). With a fresh engine in the 300-350 hp range and overdrive I am hoping to get much better MPG with the additional performance.



try pulling the plugs and pouring a mixture of ATF and MEK into the plug holes, if the problem is sticking rings that ought to cure the problem. i have worked on motorcycles that have sat for 30-60 years and cured the same exact problem many many times.

my l48 when i got it did around 12 mpg on the highway, then i went through the carb and properly jetted it, completely tore down the advance mechanism and cleaned/lubed it and when i put it all back together i got 17 mpg with the th350. cant wait to see what it does when all the changes and modifications are done next year. next big mod is the stainless chambered exhaust with one of my very own home fabbed x-pipes.

Totally stock L48 with 47K miles on it - 14 years in storage. Cylinders 1 &4 are lower on compression than the rest and the spark plugs for 1&4 are fouling with oil - I clean or change them every other month but I only put about 300 miles a month on it now. I am burning a quart of oil about every 900 miles - I finally got all of the leaks stopped but I have a few other issues due to the storage. I also drive with a heavy foot.

On the bright side I am planning a overhaul for this engine in the next 6 to 9 months (I travel a lot w/ work). I am also planning a T5 or T56 tranny upgrade when I overhaul the engine (radiator, fuel lines, and gas tank vapor canister - it has a recent fuel tank). With a fresh engine in the 300-350 hp range and overdrive I am hoping to get much better MPG with the additional performance.


Are you absolutely sure it only has 47,000 miles on it and not 147,000 miles? Or even 247,000 miles? From the sound of it with two cylinders having less compression and two cylinders passing oil it sounds like it really has 147,000 miles (or more). Try squirting about 1 ounce of 30wt oil in each of the cylinders then take another compression test. If your compression suddenly comes up to normal your compression rings are certainly shot and your valves are most likely leaking.

Totally stock L48 with 47K miles on it - 14 years in storage. Cylinders 1 &4 are lower on compression than the rest and the spark plugs for 1&4 are fouling with oil - I clean or change them every other month but I only put about 300 miles a month on it now. I am burning a quart of oil about every 900 miles - I finally got all of the leaks stopped but I have a few other issues due to the storage. I also drive with a heavy foot.

On the bright side I am planning a overhaul for this engine in the next 6 to 9 months (I travel a lot w/ work). I am also planning a T5 or T56 tranny upgrade when I overhaul the engine (radiator, fuel lines, and gas tank vapor canister - it has a recent fuel tank). With a fresh engine in the 300-350 hp range and overdrive I am hoping to get much better MPG with the additional performance.
It will improve with the engine mods, but the trans swap is what really makes the difference..it does sound pretty worn out for only 47,000 miles. good luck on the upgrades

Are you absolutely sure it only has 47,000 miles on it and not 147,000 miles? Or even 247,000 miles? From the sound of it with two cylinders having less compression and two cylinders passing oil it sounds like it really has 147,000 miles (or more). Try squirting about 1 ounce of 30wt oil in each of the cylinders then take another compression test. If your compression suddenly comes up to normal your compression rings are certainly shot and your valves are most likely leaking.

It is all original with 47K on it - I have all the documentation including the storage unit receipts for 9 years and a year latter for 5 more years. I purchased this car from the widow of the PO. She refereed me to her 40 year old son for the details on the car.

I have tried the oil trick checking the compression and it is still low. I had to replace the valve cover gaskets and intake gasket to stop the oil leaks. When we did this I could see where oil was leaking through the valves guides - just on the front cylinders. I also confirmed head issues with a bore camera going through the spark plug.

I have it running but not well. The PO's son had the car running when I bought it. He also was kind enough to service it with synthetic oil prior to me buying it - hence all of the oil leaks. I have replaced gaskets for the intake, valve covers, oil pan, and 2-piece rear seal). I switched it back over to regular oil when I did the oil pan/rear seal. Replacing the clutch was easier than the heater core.

The bottom end looks clean with no sludge or varnish. I am hoping I can get by with just a top end overhaul but I am preparing for the worst. The problem is finding time to tear into it as I would rather drive it when I am home instead of work on it.

thats the problems you encounter when a car sits for 15 years..gaskets dry out or rot, corrosion starts to work on everything.. but I assume you got a good deal on it, so hopefully it won t break the bank to get it back in shape..you know, its really not a lot more $$ to just freshen up the bottom end while its apart.and then you will have another 100,000 miles or more from it.

thats the problems you encounter when a car sits for 15 years..gaskets dry out or rot, corrosion starts to work on everything.. but I assume you got a good deal on it, so hopefully it won t break the bank to get it back in shape..you know, its really not a lot more $$ to just freshen up the bottom end while its apart.and then you will have another 100,000 miles or more from it.

My problem with taking the bottom end apart is I would put a 400 crank in it. That would be fun but that is not where I really want to take this car.

thats how i got my 78' it had been sitting for many years. i paid less for the car then i will on the interior re-furb.

I'm installing a TKO 600 behind a LSX in my 71.I've been wanting a stick back in the car since I got it.
It was a 4spd that got an auto thrown in it sometime in it's past.If this TKO is anything like the others I've tried, it will be SWEET!
A 700r4 is not a bad choice for the money though! :thumbsup3:

the TKO is a great trans. i ran one in my 85 mustang notch after destroying a G-Force T-5

the TKO is a great trans. i ran one in my 85 mustang notch after destroying a G-Force T-5
How much hp were you feeding the tranny? I think this TKO will hold it's own.(I hope!)
http://i53.photobucket.com/albums/g65/showme71vette/DSCN1123.jpg

How much hp were you feeding the tranny? I think this TKO will hold it's own.(I hope!)
625 at the wheels.

625 at the wheels.SWEET! I think my next weak link will be the rearend!(But thats another topic.)