1981 repower
Burning Brakes
Joined: Sep 2012
Posts: 818
Likes: 0
From: coon rapids mn
do a compression check first..consider a elderbrock performer intake and a comp ex262h ,or ex268h cam .consider long slot rockers.some dart iron heads would really wake up the motor if your stock heads need rebuilding.check out competition product for 350 or 383 short and long blocks.
Racer
Joined: Nov 2011
Posts: 261
Likes: 1
From: Montgomery TX
My 4spd 81 was a California emmisions car. The engine had been rebuilt by a PO and had a performance cam installed although I do not know what type. I pulled the carb. , manifold, distributor and emmisions equipment. Went back with an Edelbrock EPS manifold. Edelbrock 600 carb and HEI distributor, factory style side pipes bolted to the factory tubular headers.
The difference was dramatic, the engine has a nice lopey idle and after some tuning smokes the tires easily in first and second. It pulls hard when floored at cruising speed and I have not found top end yet. We had a C6 for four years and its no match for that but sure feels good. It was pretty tame when I got it.
The whole investment not including the pipes was less than $1K. I need to get it dynoed to see what the RWHP is.
I considered a crate engine or LS1 but am now satisfied with the way it runs now.
The difference was dramatic, the engine has a nice lopey idle and after some tuning smokes the tires easily in first and second. It pulls hard when floored at cruising speed and I have not found top end yet. We had a C6 for four years and its no match for that but sure feels good. It was pretty tame when I got it.
The whole investment not including the pipes was less than $1K. I need to get it dynoed to see what the RWHP is.
I considered a crate engine or LS1 but am now satisfied with the way it runs now.
Last edited by texasbaehr; Jan 11, 2013 at 11:17 PM. Reason: add pics
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
In response to the original heads being cracked...
The original heads are thin casting smog heads..built to meet '81 emissions, no they will not leak coolant. They crack in the thin areas. It has been a very long time since I got rid of those heads and I do not remember the details. Suggest doing a search using the last three numbers on the heads...I think this is 481...but just not sure.
I had three rocker arm studs walk-out and this was on a completly stock engine...pressing them back-in only lasted a short time. That is when I took the heads to the machine shop...which told me the problem with these heads...further searching verified the information.
These heads are junk....replace them.
The original heads are thin casting smog heads..built to meet '81 emissions, no they will not leak coolant. They crack in the thin areas. It has been a very long time since I got rid of those heads and I do not remember the details. Suggest doing a search using the last three numbers on the heads...I think this is 481...but just not sure.
I had three rocker arm studs walk-out and this was on a completly stock engine...pressing them back-in only lasted a short time. That is when I took the heads to the machine shop...which told me the problem with these heads...further searching verified the information.
These heads are junk....replace them.
6th Gear
Joined: Nov 2012
Posts: 6
Likes: 0
From: Lake Ariel PA
I did same upgrade...cam,edelbrock intake /carb/MSD Dist vacuum advanced. The issue I'm having is an electric draw on bat when not in use.Choke heater is in acc/ign fuse spot. Only hot with key on.I have suspision on stereo or power antenea.Im curious if I should change engine wire harness. I see Ecklers has one for $209.00. My concearns are the wiring at fire wall that is not being used anymore (disconnected) is making the circuit incomplete as for the wiring diagram is 1981 and car is now set up to run like 1974
Racer
Joined: Oct 2003
Posts: 424
Likes: 9
From: Killeen Texas
It's true, as stated about the heads being not worth working. they should be replaced. Heads are a very important component when it comes to the engine breathing properly. Going w/ the original block, if it's iin good shape, will save you afew dollars. Good Luck.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
There is no performance loss to your engine/ignition system by leaving the existing hardware on it....either 'as is' or if you rebuild the engine...IF it is still functioning properly. You can put any carb/distributor you want on it, but it won't be any "better" than a good working Q-Jet (with electronically controlled fuel mixture) and the computer controlled HEI timing that came with the car.
Your transmission was a THM-350 with lockup (no overdrive); but an overdrive transmission really won't do you much good, as you have a 2.87 gear ratio in the back. The O/D auto trannies are meant for 3.23-3.73 rear gears; otherwise, you get a lot of low speed 'bucking' because of the low rpms at 35-45 mph. Or you can just run the car in 3rd gear until you get on the highway. At 70 mph with a 2.87 rear gear, an O/D tranny will be running at about 1700 rpm (or less)..and just loping around.
If you are bound and determined to remove the '81 dizzy, carb, ECU and wiring harness, just send it to me and I'll pay the freight!
P.S. I put a 700R4 in my '71 a couple of years ago and love it; but it has a 3.36 rear gear. The best tranny choice for me would have been a 200-4R, but that's because mine came with a THM-400 and I wouldn't have had to change the crossmember and driveshaft with it. But, the 700 was available at the right price, so that's what I did.
Not sure which unit is easiest to swap for a THM-350C if you decide that's what you want to do.
Your transmission was a THM-350 with lockup (no overdrive); but an overdrive transmission really won't do you much good, as you have a 2.87 gear ratio in the back. The O/D auto trannies are meant for 3.23-3.73 rear gears; otherwise, you get a lot of low speed 'bucking' because of the low rpms at 35-45 mph. Or you can just run the car in 3rd gear until you get on the highway. At 70 mph with a 2.87 rear gear, an O/D tranny will be running at about 1700 rpm (or less)..and just loping around.
If you are bound and determined to remove the '81 dizzy, carb, ECU and wiring harness, just send it to me and I'll pay the freight!
P.S. I put a 700R4 in my '71 a couple of years ago and love it; but it has a 3.36 rear gear. The best tranny choice for me would have been a 200-4R, but that's because mine came with a THM-400 and I wouldn't have had to change the crossmember and driveshaft with it. But, the 700 was available at the right price, so that's what I did.
Not sure which unit is easiest to swap for a THM-350C if you decide that's what you want to do.
Last edited by 7T1vette; Jan 12, 2013 at 05:08 PM.
Intermediate
Joined: Feb 2016
Posts: 28
Likes: 0
My heads are original and are not cracked...
Here's what I did with my '81, It was bone stock when I bought it:
Adjusted the timing to 14* base timing
Summit brand long tube headers and a true dual 2.5" exhaust with magnaflow mufflers.
swapped the automatic out for a Richmond 5 speed transmission.
I can spin the tires up pretty good from a stop now and the car is much more fun to drive. My stock carb and computer work perfectly though, so I had no drive-ability issues to begin with.
My next item on the list is to remove the mechanical fan and install an electric one.
Whens it time to think about the engine, New heads are a MUST. The stock heads don;t flow very well at all, and like said already, are prone to crack.
If I were you, and wanted to mess with the engine I would install a roller cam, and some 170cc-185cc heads, and anything else that goes along with it (new timing chain etc.) don't go too crazy on the cam, otherwise your stock carb and Distributor will need to be replaced, as the stock ECM doesn't like low vacuum situations. The stock aluminum intake will work well and fit under you hood (obviously)
A 700R4 transmission has a lower first gear so that will help with your crappy 2.87 rear gears. You can get all the parts from an '82 to do an easy install. Or you could go with a TKO500 manual transmission or a Richmond 5 speed like I did.
When the time comes, I'm going to just replace my engine, Since it has 100K on it. Roller cam Crate motors are cheap enough now that I don't see a point and spending the time to rebuild the original block.
Here's what I did with my '81, It was bone stock when I bought it:
Adjusted the timing to 14* base timing
Summit brand long tube headers and a true dual 2.5" exhaust with magnaflow mufflers.
swapped the automatic out for a Richmond 5 speed transmission.
I can spin the tires up pretty good from a stop now and the car is much more fun to drive. My stock carb and computer work perfectly though, so I had no drive-ability issues to begin with.
My next item on the list is to remove the mechanical fan and install an electric one.
Whens it time to think about the engine, New heads are a MUST. The stock heads don;t flow very well at all, and like said already, are prone to crack.
If I were you, and wanted to mess with the engine I would install a roller cam, and some 170cc-185cc heads, and anything else that goes along with it (new timing chain etc.) don't go too crazy on the cam, otherwise your stock carb and Distributor will need to be replaced, as the stock ECM doesn't like low vacuum situations. The stock aluminum intake will work well and fit under you hood (obviously)
A 700R4 transmission has a lower first gear so that will help with your crappy 2.87 rear gears. You can get all the parts from an '82 to do an easy install. Or you could go with a TKO500 manual transmission or a Richmond 5 speed like I did.
When the time comes, I'm going to just replace my engine, Since it has 100K on it. Roller cam Crate motors are cheap enough now that I don't see a point and spending the time to rebuild the original block.
