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81 Engine rebuild and transmission upgrade

Feltman

Well-known member
Joined
Jul 18, 2003
Messages
97
Location
Indianapolis
Corvette
1981 Dark Blue Coup
I have read many post on this subject and honestly not sure which direction to go, since most post discribe their own unique project...so here goes mine. I am at the point in my restoration project that the engine and transmission is next. Just completed rebuilding both doors (hardware, new window regulators, motors, lock actuators, new rubber..etc..etc).....now what I would like to do is this:

Keep my original engine and upgrade to produce more horsepower....not 18 anymore, so looking for a good mix of daily driving with an occasional "show off" of what my smog vette will do ( have true dual exhaust now). Want to keep the stock q-jet and distrubutor. I know most HP gains can be made in the heads. I will be removing the engine and transmission myself and then to the machine shop for the engine. I am looking at buying a 700R4 (I want the overdrive) and know that some modifications will need to be made to the shift panel and lock-up conversions.

I am stuck on the gear ratio...mine is stock........as always I look forward to the feedback that I get from this outstanding forum:

Recap:

1. Engine rebuilt: suggestions

2. Transmission/rear end ratio combination.....(torque converter recommendation also)

Happy Holidays to all!!
 

Peer81

Well-known member
Joined
May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
Hello Feltman,

I'm in the middle of a complete body-off project so I had to deal with these issues two years ago.
Starting with the transmission. When you want to buy a 700R4, be sure to get a 4L60 (late 700R4, and not the 4L60E type) The first generation 700R4's have there weaknesses and they are corrected in the 4L60. I think after 88 or 89 they where put in Corvette's. Second thing, they said to me to only take a Corvette 4L60 (700R4). These have some stronger parts inside and something that has to do with the 4th gear.
Things you have to change.
Put a 82 center console gear selector indicator thing in to replace your 81. The plastic thing with the gears on them.
Easiest thing to do is replace your 81 transmission crossmember for a 82 model. You have to shorten your driveshaft to fit between the transmission and diff or take a 82 model.
I'm still not sure if the 81 ECM will control the luckup on the 700R4. Some say it will some say it will not. I also got the lockup kit from bowtie overdrives to let the lockup work without the ECM.
As far as I know the diff is a good combination for the new transmission.

Engine.
I wanted the outside to look stock so all the changes occurred inside. Without changing the heads my engine guy advised me, to not go with a 383 but some guys here made a 383 and are very happy with it. I changed the camshaft for a comp cams (don't recall the number). Changed the pistons for the hyperthings, heavy oil pump and it already had a double chain, timing chain on it. The engine only has ran for maybe an hour till now so I don't know the results. True dual with Dynomax Ultra Flow will be installed somewhere in may next year (if Santa Gerry is willing to send them to me ;) )

Groeten Peter.
 

Sensei

Well-known member
Joined
Apr 5, 2004
Messages
393
Location
Jacksonville, Fl
Corvette
'81 dark blue
I used Dart Iron Eagle 180cc runner, 72 cc chamber heads. Got them from a guy on e-bay (race parts direct) new assembled ready to bolt on for under $800 to my door. I've got around 10k miles on it so far and they have been great. I used Speed-Pro flat top hypertuetic pistons and a Comp XE 262 cam. Seems to be a great combination; very efficient and works well with the stock computer and distributor.
As far as the 700r4, I have also been looking at putting one in for the overdrive (if my th350c ever goes). The only concern I have is that I have heard you need to have at least 70 MPH at 2000 RPMs. With the '81's stock rear gears, I think you would be just under that (about 68 or 69 MPH). Has anyone with a stock '81 rear end put in a 700r4 and put enough miles on it to let us know if it is okay? God bless, Sensei
 

gedmeyer

Well-known member
Joined
May 17, 2003
Messages
316
Location
upstate New York
Corvette
former L81 owner!
Groeten,
Check out my website http://gedmeyer.l81vetteregistry.com. I did an engine buildup 3 winters ago. The engine still looks completely stock, but I did get some more horsepower out of it. I sent out the carb for a full rebuild (looks brand new) and kept the stock distributor/computer setup. I did remove the smog equipment, but you could leave it on just as easily.

-tim
 

Feltman

Well-known member
Joined
Jul 18, 2003
Messages
97
Location
Indianapolis
Corvette
1981 Dark Blue Coup
Great thanks for the engine information..just what I was looking for.....now I hope to here more about the right rear gear to run with a 700R4.....
 

WONKABOY

Well-known member
Joined
Oct 31, 2004
Messages
237
Location
BRIDGEPORT , CT
4L60E IS BETTER

Hello Feltman,

I'm in the middle of a complete body-off project so I had to deal with these issues two years ago.
Starting with the transmission. When you want to buy a 700R4, be sure to get a 4L60 (late 700R4, and not the 4L60E type) The first generation 700R4's have there weaknesses and they are corrected in the 4L60. I think after 88 or 89 they where put in Corvette's. Second thing, they said to me to only take a Corvette 4L60 (700R4). These have some stronger parts inside and something that has to do with the 4th gear.
Things you have to change.
Put a 82 center console gear selector indicator thing in to replace your 81. The plastic thing with the gears on them.
Easiest thing to do is replace your 81 transmission crossmember for a 82 model. You have to shorten your driveshaft to fit between the transmission and diff or take a 82 model.
I'm still not sure if the 81 ECM will control the luckup on the 700R4. Some say it will some say it will not. I also got the lockup kit from bowtie overdrives to let the lockup work without the ECM.
As far as I know the diff is a good combination for the new transmission.

Engine.
I wanted the outside to look stock so all the changes occurred inside. Without changing the heads my engine guy advised me, to not go with a 383 but some guys here made a 383 and are very happy with it. I changed the camshaft for a comp cams (don't recall the number). Changed the pistons for the hyperthings, heavy oil pump and it already had a double chain, timing chain on it. The engine only has ran for maybe an hour till now so I don't know the results. True dual with Dynomax Ultra Flow will be installed somewhere in may next year (if Santa Gerry is willing to send them to me ;) )

Groeten Peter.


Hey pete my 1994 came stock with L460E the E is for electronic my buddy had a 92 and it came stock with a L460 nothing but trouble !!
 

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