bkarsten26

I am new to this site, but I have had a 1981 for about four years now. The motor is all stock as far as I can tell. So I was wondering if anyone has any ideas on how to bump up the horsepower short of replacing the motor. For example any cams, intakes, heads, headers,etc. Thanks to any replies.

Solid LT1

I think all 81's were 350s so your OK there but, the carburator is a CCC controlled emissions design with electronics interfaced in the fuel mixture and ignition timing (as I recall from my school years way back in the 80's.) You will need to lose your ECM control of your fuel and spark advance curves to sucessfully modify the engine. The heads can be swapped for small combustion chamber/small intake runner heads like the Dart SR Torquer heads with the 64cc combustion chambers to boost the compression, the intake and carb swapped for something more performance freindly (Edelbrock Performer Qjet intake and a Edelbrock or earlier Qjet carb.) You could go with a mild Comp Cams hydraulic grind but, don't go too wild if you are running an automatic transmission (XE262 cam or smaller.) The exhaust should have the catalytic converter changed to a high flow unit as the early cats are lousy! You will need to get a new HEI distributor and eliminat the electronic spark control. You should be able to go from the 190HP to around 260-300 with a set of good bolt-on performance parts but, first have the engine's condition checked witha leakdown test being performed on it. The engine should have less than 10-12% leakdown rates or you need to consider a rebuild at which time, I would go to a 383 size motor.

standup

:iagree: ........no holes in that logic :yesnod:

pillowmeto

I like what LT1 said, he hit everything right on the head
Id like to recommend Vortec heads as a possibility. They can be found on truck engines in the junkyard for near to nothing and might out perform the torquer, which is a very very good head for the price too.
You might want to also consider a good set of headers, shorty headers will do fine, and if your lucky they might mount right up to the existing exhaust
I cant think of anything else right now

MAtt

Pauld

:iagree: thats the exact route I am considering, I have a true dual exhaust system that I put on at the moment, which has improved things a bit


[Modified by Pauld, 9:45 AM 4/14/2004]

markdtn

How about putting a Tuned-Port on your stock bottom end. You'd feel like you had a new car. There is lots of info in the previous on TPI conversion.

stingraymaniac

:iagree: to the talkers above and welcome to the forum!!!!!!!

Beer

Here is what I did to my 81 before I pulled the motor to start a full rebuild. I had already planned to change the hood so height wasn't an issue for me. I also have ohio collector plates so I pulled the exhaust cats, air pump, etc. So there really isn't polution control to speak of. Without going too crazy just going with a new set of heads and cam will make the difference. Get the carb reworked, you might want to have lars work on it. If you plan on replacing the computer chip, I might still have one from when I updated mine, got it from Mid-america or ecklers. Don't remember which. I'll have to check because I disconnected the computer as well. You can email me at beer@lanplay.net if your interested in the chip.

Intake: edelbrock performer rpm
Carb: edelbrock 1407 performer 750
heads: trickflow 23 degree TFS-30400002
cam: trickflow TFS-K31401001 duration 228/234 lift 480/494
ignition: accel


:cheers:

bkarsten26

I also forgot to mention that I do not need to worry about emissions. I plan to take off the air pump if I can figure it out. I also hollowed out my cat already. The only question I have now is how do you get rif off electronic spark control. Also electronic fuel control. Is it true that only a performer can fit under a stock hood? Thank you for all the posts so far but now it seems like I have more questions than ever. It is a manual stock tranny.

pillowmeto

almost any carb will fit under your hood. The performer is good for the price, i bought a used 600 for 100 bucks with about 3 hours of run time on it. Holley makes very god ones, but they are twice as much, i woudl suggest a deamon, they are a good mix of the two.
To get rid of the eletronic stuff just rip it all out, but a new distributor and carburator. Just put those on :yesnod: .
Id reccomend a HEI distributor, though you might beable to modify the existing one to work, which should also be HEI.
If you want to spend alot, you can buy a used TPI unit off of a 85-90 corvette and use that, it will do wonders for the car, but dont expect to pay anyless than $1,500 for ir, that will do the job of both the carb and distributor, and the intake manifold.
You may need to get a drop base air cleaner with an aftermarket carb and intake manifold. They just sit lower with the same size air filter to give you more hood clearance.

If i were you id start by adding a edlebrock or deamon carb (600-650) and intake manifold (id reccomend a torker II) a HEI distributor (unless you can modify the existign one to work) and a set of shorty headers. You will also want to recurve the distributor, unless oyu buy an aftermarket performance one, this will pick up a few HP.

MAtt

standup

......single plane intakes like the Torker II are for high reving setups and are not an ideal setup for the street.....it's better to stay with a dual plane like the Performer EPS........

Also, Vortec heads require a special intake manifold and center bolt valve covers and need a lot of work to make good power.......better to use the small chambered Dart heads like Solid LT1 suggested......

Beer

:iagree:

stick with a dual plane

Willis

Changing an intake manifold is hardly a lot of work, considering that it is already off of the car to get the heads off. Stock vortec heads make more power than the old double hump 2.02/1.60 heads, and a set of vortecs is MUCH less expensive than a new set of aftermarket heads. Even after you buy the intake manifold and the valve covers, (which look cool anyway) you will still be ahead.

cmashark

WHOA!!!! hold up everyone....i went by the local speed shop today and talked with their machinists and the owner. now i used my 77 L82 as the example. it has the correct cam in it and 9to1 compression. i asked them about putting the 64cc heads on mine to bump the compression and they said it would put me somewhere between 10to1 and 10.5to1 compression. say goodbye to the cheap gas. some of you engine builders need to chime in to see if this jives.

chris :lurk:

standup

........stock compression on an '81 is 8.2:1........

standup

........the work I was referring to was in overcoming the limitations of the Vortec heads, including increasing valve lift and using performance springs and roller rockers......

.......also, it is not clear whether the recommended intake manifolds, eg. the Vortec Performer RPM and Vortec RPM Air Gap will fit under a stock Corvette hood.....

........the original comment was that buying a set of used Vortec heads off a truck is a cheap way to go, which may be true if you find the correct version of the L31 head, as there are variations that are useless to modify......

....all in all there's a lot of homework and hunting around around to do with Vortec heads, and since time is money, I don't think they are the bargain of the century........

:cheers:

7T9Shark

I pretty much agree with Solid LTI. Unless your current rotating assembly has relatively low miles and is solid, You need to do a rebuild before you ask it to bear the punishment of additional ponies. I would seriously consider the 330HP GMPP crate motor. I spent almost that much bringing mine up to those specs, and tied it up for two months last summer. Sure made a difference though.

My $.02