Cheap power for '77 Vette

[p. rex]

I have a Silver 1977 Corvette L-82, with the Turbo-Hydramatic 3-speed, and, in all honesty, it's pretty anemic. I'd like to get respectable performance out of it, but I'm on a fairly tight budget.

I'd like to get high 14's or low 15's in the quarter mile, which is fast enough to humiliate most modern Japanese cars. As far as I can tell, I have three main options:

1) Rebuild the current engine. I believe the engine is original, and if so, it has about 130,000 miles on it. Somehow, a performance rebuild seems like a poor idea with such an old, tired, and incompetent engine, but this is most likely the cheapest option.

2) Replace the engine with a quality small-block. I could drop in a new 350 crate engine putting out somewhere around 300-350 horsepower. This would definitely produce satisfactory performance, and probably at a fairly reasonable price. My one concern is the transmission: how much torque can a TH-350 handle, especially at this age? As far as I can tell, the transmission is in good, working condition, but I would hazard to guess that a new engine could cause problems. Also, will the automatic transmission significantly hinder performance?

3) Go the whole nine yards: drop in a modern overdrive transmission and some ungodly big-block. Obviously, this will yield the best results, but will involve significant financial hardship for me.

I love the old car, but I just can't get over the fact that my 1995 Acura Integra (I love it, but it's a glorified Honda Civic) is faster than it.

Lastly, make sure you include labor costs in your price estimates. I know quite a bit about cars, but I'm not all that great mechanically, and I would NOT trust myself to do an engine swap.

 

[bossvette]

Welcome to CAC!!
Go with a 383 you will be glad you did, The best small block for the street. I prefer to build my own but a "Crate" motor is much easier and may even be cheaper in the long run.

 

[Koop]

Welcome to CAC!!
Go with a 383 you will be glad you did, The best small block for the street. I prefer to build my own but a "Crate" motor is much easier and may even be cheaper in the long run.

I went with the ZZ383 crate because it was cheaper than a custom 383 and it has loads of good stuff. It works great with the lightly modified TH400 trans and a 3:08 rear end. The GM warranty makes me feel good to.

Check them out at the GM crate web site.

 

[p. rex]

If I go with the ZZ383, can I leave the stock TH350 in place? Do I need to strengthen it?

 

[Koop]

There is some great info available from the members here.

All I can say about the TH350 is I ran one behind an LT1 with no trouble.

 

[Crimson Thunder]

A stock 77 L82 should run mid 14's with nothing more than a set of headers,true dual exaust,and a good tune up.Way back in the high school days, a good friend had a stock 79 L48/turbo350/3.55 car with headers and duals and ran 14.30's.Didnt the L82 come with the turbo 400 and the L48 come with the Turbo 350?

 

[p. rex]

Okay...

How much should headers and true dual exhaust cost me? If I can get mid 14's just from that, then that's what I'll do. I've noted that much more powerful small-blocks were made from 1968-1972 with the same compression and similar looking specifications. Was the loss in power caused only by restrictive intake and exhaust?

Also, I can't shake the impression that the 3-speed REALLY hurts performance. Is this true?

 

[zachh]

The late 79 l82s came with the turbo 400, and possibly a few L48s. I dont know what decided the different types in different cars. I have Hooker hedders and sidepipes. They cost about 1400$. If you want a good site, www.mamotorworks.com I also have a question, mine is the 400, Is it 3, or 4 speed?
zachh

 

[bossvette]

TH350 and aTH400 were both 3 speed trans with the TH400 being the stronger version

the 700R4 and 200R4 are 4 speed OD trans
the newer OD trans are named differently something like 4L60E and 4L80E and are computer controlled

 

[AKRAY4PLAY]

Okay...

How much should headers and true dual exhaust cost me? If I can get mid 14's just from that, then that's what I'll do. I've noted that much more powerful small-blocks were made from 1968-1972 with the same compression and similar looking specifications. Was the loss in power caused only by restrictive intake and exhaust?

Also, I can't shake the impression that the 3-speed REALLY hurts performance. Is this true?

the "loss of power" was from from the swap from gross to net ratings for horsepower. the differences in the two systems are so much that there is no way to compete the two except to dyno each engine again with the same parameters. needless to say, the '70's cars got a very bad reputation because people would look at the rated hp and play judge, jury and executioner. you can do a lot with the stock stuff, but a motor swap is a damn good idea. can you operate a wrench?? then you can do motor swap, it's really easy. don't let the size of the project scare you, it's really no more difficult than changing oil. also look at the GM 350 ho crate motor. it is a great buy at $2400 and makes 330 hp. they are available from any GM dealer parts department as are the entire Jim Pace performance line. also side pipes are not a necessity, a good set of headers and duals will run about $700 complete. also your stock tranny is good for about 450 hp if it is still on good shape.

 

[GerryLP]

Option # 2, Definetely. Like Craig Sr. said...in the long run it will be much cheaper.

GerryLP:cool

 

[p. rex]

Okay, so the factory 3-speed tranny is strong enough, but will it hurt my 1/4 mile times? I don't particularly care if it pulls 4,000 rpm when I'm doing 80mph on the freeway, and I don't need a 150mph top-speed, I just need to know if a well-built, modern transmission will significantly improve acceleration.

I've checked road tests from Road & Track and Motor Trend (I think) from 1977; a Muncie-equipped L-82 runs about mid-15's, and an automatic L-82 takes over 17 seconds. Is this the result of different testing conditions, or is the auto that much slower?

Lastly, my 'vette doesn't feel like it's pulling 15's. I'm starting to wonder whether it really has an L-82 engine in it. I'll have to check the VIN.

Thanks for the advice,
p. rex

 

[GerryLP]

[1] , so the factory 3-speed tranny is strong enough, but will it hurt my 1/4 mile times? ... need to know if a well-built, modern transmission will significantly improve acceleration.

[2]... or is the auto that much slower?

[3] my 'vette doesn't feel like it's pulling 15's. I'm starting to wonder whether it really has an L-82 engine in it. I'll have to check the VIN.

p. rex

p.rex,

1) A fresh factory configuration works fine in the 1/4 mile, and minor tweaking Will do wonders. A 23 year plus tranny could fail on X number of passes.

2) The automatic robs horse power from the engine to drive its internal components, but with a little money and a good tranny mechanic you can end up with a truly reliable and efficient tranny set-up.

3) If it was running 15's, then that means you have a manual transmission, right? From the sound of it, you have an automatic.

Let me tell you about my experience, I had 355 engine (with flat top pistons w/ 4 valve reliefs) with a XE274H cam, Edelbrock performer heads, a Holley 650 DP, a Weiand single plane manifold, hedders, and my current tranny (1981 Corvette TH350C) running a 2400 stall locking converter. My best time was 0:14:36 (at 5280 feet altitude). The tranny worked fine.

I recommend that you take a look at your engine's timing after a pass, and adjust the distributor weight springs or even the total timing. In the 1/4 mile, you can experiment safely with 30 -36 degrees of advance timing. Then make another pass. Was your time better or worse? Then try another tweak. And so on and so forth.

The key is to MAKE ONE CHANGE AT THE TIME. It will be tempting to make two changes (i.e. fuel jets sizes and timing), but don't do it. You won't be able to trust your engine performance. Also, write down all the changes made, so that you can back track your way to a certain point.

Good luck!

GerryLP:cool

 

[AKRAY4PLAY]

auto trannies are the way to go for going fast. R&T has been pulling the wool over peoples' eyes for some time. they do not brake stall autos for good launches in time trials. pretty much they idle cars until the light turns and then hit the gas and let the tranny shift, no power shifting to increase performance. remember the shift patterns were designed for as economy not performance. even todays modern autos will cut better times if you manaually shift the tranny. and there must be areason for 95% of new cars to have autos. yes the auto sucks up torque to turn the internals, but there is a double edged sword you're playing with. at high rpm, the auto looses effecientcy. but conversely at low rpm it is a torque multiplier. basically you gain low and loose high compaired to a manual tranny. a good stall converter will cure the high speed losses. go to the races and check out how many fast cars are running autos, bet you'll be surprised!

 

[Crimson Thunder]

Im still thinking headers and dual exaust.You will have to put these on even if you later choose to do an engine swap.A decent set of ceramic` coated headers will run around 250.00 and any local muffler shop will do duals for about 200.00 using your stock mufflers.I wouldn't worry about the tranny,there are millions of fast cars running around with Turbo 350/400.

 

[lightingrod]

Well, a 77 L-82 was no rocketship and that's for sure! All the smog crapp and no compression! As others have said a TH-350 or Th-400 with a little work will be great for what you want! For the most part in the 1/4 mile there's no big advantage to a 4/5/6 auto. What you may gain with better gear ratios will be lost in shifts/weight/and power robbed! With a 350cid and even more so with a 383cid you will have a wide enough power band (torque curve) for 3 speeds to get you down there just fine! Didn't see your rear gears but anything over 3.08's (3.55-3.70's) will be a help!

Buy or build would be up to you and your friends, it's a lot easier with a few friends. Of course your and there skill level is very important! As most here have already said, there's alot options out there! 350-HO, ZZ-4 and right on up to my choice the ZZ-572! How fast you want to go? Good luck, think about it, read a bit, check your budget, and then form your plan. I'm sure alot of guys here will give you advice!

Al

 

[p. rex]

It currently has 3.55 gearing. I'm thinking that the best option now would be to build the current engine; all things considered, a crate engine would cost at least $4000 after labor (I don't have the expertise or equipment to do it myself). Is 300HP to the wheels a reasonable expectation if I get headers, side pipe exhaust, and hotter camshafts? Will I gain any torque from the aforementioned mods?

I don't need to break any records, I just want the car to be as fast as it looks. I'd like to be able to stomp on the gas and go in a hurry, or kick up lots of smoke.

Lastly, can I install headers, exhaust, and camshafts myself? I know little mechanically, but I can read, I'm pretty quick mentally, and I'm persistent.

 

[Koop]

It currently has 3.55 gearing. I'm thinking that the best option now would be to build the current engine; all things considered, a crate engine would cost at least $4000 after labor (I don't have the expertise or equipment to do it myself). Is 300HP to the wheels a reasonable expectation if I get headers, side pipe exhaust, and hotter camshafts? Will I gain any torque from the aforementioned mods?

I don't need to break any records, I just want the car to be as fast as it looks. I'd like to be able to stomp on the gas and go in a hurry, or kick up lots of smoke.

Lastly, can I install headers, exhaust, and camshafts myself? I know little mechanically, but I can read, I'm pretty quick mentally, and I'm persistent.

300 HP to the wheels is a bit optimisticwith those upgrades. I'd bet you'd be happy with the exhaust, cam and you'll need to rejet the carb at a minimum and later you'll need a stall converter. Those improvements will make the car a bunch faster, but most important...It'll sound very cool! I had a '78 with the stock low compression L82, I put a big cam in it and it sounded mean as hell! It went pretty fast to.

 

[GerryLP]

It currently has 3.55 gearing. I'm thinking that the best option now would be to build the current engine..., a crate engine would cost at least $4000...(I don't have the expertise or equipment to do it myself).

:confused The statement above begs for a crate motor...if you have tools and shop equipment available and the best Chevy book available for an overhaul, then that's a good start, BUT there still the machine work needed (i.e. $$$), replacement parts, and time involved. I definitely believe in the learning of these tasks and a little coaching, but personally I would not experiment on my first build on the number's matching engine. You can find good and seasoned blocks locally, and Ebay always has a good set of heads for awesome price.

Is 300HP to the wheels a reasonable expectation if I get headers, side pipe exhaust, and hotter camshafts?...

IMHO, those are components that depend on a good bottom line displacement and resultant compression ratio (CR). If you have a good CR working for you, then those components will help.

...I don't need to break any records, I just want the car to be as fast as it looks. I'd like to be able to stomp on the gas and go in a hurry, or kick up lots of smoke.

:L That's how I started a couple of years ago. Verbatim! Here is a good perspective. I spent about $5,800 dollars to get my 14:36 1/4 mile time. Some people would say I got off cheap. But is never enough. I was ready to dump another $5k dollars to drop to the teens. Then I came to my senses. :ugh

Lastly, can I install headers, exhaust, and camshafts myself? I know little mechanically, but I can read, I'm pretty quick mentally, and I'm persistent.

That as good project to start if never wrenched on the car before. Some cams require a change in the torque converter.

GerryLP:cool

 

[craig32]

Lastly, can I install headers, exhaust, and camshafts myself? I know little mechanically, but I can read, I'm pretty quick mentally, and I'm persistent.

Yes, yes, and probably no. There is only one camshaft in an SBC 350. You may be thinking of the Acura with the overhead cams, not the same. Read the other posts on here about adjusting rockers, if you change the cam, that's in your future. Not like an old Ford where 4 bolts holds the whole set of rockers on with no adjustment either. I'm not by any means trying to talk you out of learning to rebuild an engine, but don't think changing a cam is a weekend project. GerryLP is right on with the advice to learn all you can. Hope this helps.

Craig