hey, im thinking about purchasing an 81 vette, and i was wondering what the capable hp is on the stock 350 with a reasonable amount of work, or if id be better off with a different motor, please let me know what you think.
thanks

 

Your engine, if done properly, has a lot of potential. It really all comes down to how much you want to spend for that HP. Do you have a specific budget in mind or even any performance goals?

 

I agree, if you put dual exhaust and headers there will be a noticable improvement. Of course it all depends on the state you live in.

 

If you bought a crate motor for it, you would probably need to get at least a 330 horsepower engine to see any real improvement, if you keep everything else stock.

 

Take a few moments to fill out your profile for us. See, if we could tell where you were from we could make suggestions that have to do with your region. Like if you were from CA, we would tell you not to touch any part of the car that affects emissions.

 

It all depends how far you want to go. Like Durango Boy said, if you live in an area where emissions aren't a problem, a nice set of headers and a dual exhaust will wake things up quite a bit.

I believe the L81 in the 1981 came with 190hp, but it had a good torque number, I believe beyond 250, and that's what you feel, anyway.

Like I said, it depends how wild you want to get.
Mild improvement-exhaust.
Little bit more-change your rear end gears, port and polish your heads.
Getting crazy-New heads, roller rockers, big cam
Nuts-crate motor, or look into machining your block to get some more displacement (383)

How far do you want to go?

 

i live in California. I want a good increase in power, im thinking a budget around 3 thousand right now for the motor. Ive only dealt with imports before, so this is a whole new project for me. thanks for the help

 

This engine is the venerable small-block Chevy. The SBC is arguably the most popular engine in the world for engine swaps into all kinds of vehicles, whether for hot-rodding or not!

There is nothing better to give you inexpensive performance options than the motor that is already in your Corvette.

 

Living in California is likely to be your most limiting factor.
You may have to maintain the Cat, but you can swap in a Hi Flow cat, True Duals, better Mufflers and there are headers that maintain the AIR Injection tubes.
The stock carb and distributor will handle a pretty wide variety of engine mods. A bumpier cam and Prt/Polish heads or even replace them. You can stick on a Vortec setup for around $1k.

Any performance mods should start with exhaust so see what you can get away with out there.
Then its a matter of maintaining smog numbers against $$

 

Ugh that's not what I wanted to hear...

 

I can honestly tell you from owning an '81, that doing just the exhaust won't get you much... at least mine didn't. I'm still running the stock manifolds, but swaped the exhaust out for side pipes, and aside from sounding real good I didn't notice any change in performance... it still can't break the tires loose from just flooring it at a stand still

From what I've read, one of the best upgrades for the L81 engine is a set of vortec heads. I'm either going to swap a set of vortec heads and a new cam in or a whole new crate engine... I haven't decided if I want to spend a few hundred or a few thousand on the engine yet. If you're looking to get a vette to work on and modify, an '81 is a great choice, but if you want real performance without having to do any mods, don't get an '81.

 

Six is right. Being in CA will be your biggest limitation, not the 81 engine.

With a few exceptions, you can't do very much to the stock L81 and remain legal here. Mostly, you're limited to hidden things (like changing to a stroker) and finding an incompetent smog station.

If you're looking to do mods and finding real power, I would suggest going to a 1975 or earlier C3. Then at least you don't have to contend with smog inspections. Currently anyways.

 

so does anyone think its possible to gain a sufficient amount of hp with about a 3k budget on this motor, or am i just going to be wasting my time?
thanks for all the help also

 

$3k is plenty to realize significant power increase.
It has to breathe so exhaust is needed, you can hand build it for $500 or so
Vortech kit $1000
Cam, lifters, top end kit $500
Keeping the smog system intact should still get you to pass
guestimate on hp ~250
Swapout Tranny for 2004R with a 2200 stall converter annother $1k
That will get you the seat of the pants kick your looking for, better milage.
Unless the smog check guy is pretty sharp, he won't see the difference in the heads and intake, you can plumb it allin exactly as it came from GM.
I think you can do it, but I don't live there

 

If you want HP in CA, you're money ahead to install an "CA emissions legal" injected crate engine w/computer. You will get the horsepower you want, be able to pass emissions testing, and get much better mileage than us Q-jet boys. Trying to get all that done with a stock block set-up would cost you more $$$ {if you could do it at all}.

 

That's just what I was thinking. A fuel injected motor of some kind. Maybe even an engine out of a GM like a newer 5.7L or 6.0L takeout engine with harness and computer, and swap out your old motor for a new one. You can find LS1 engines complete for under $2000, and then another $1000 or so for brackets, exhaust, and random goodies.

 

See my sig. That'll get you more power.
But, not for your budget. I don't know what you can do in CA as far as mods go, but you could swap out your cam for a comp 260H, go with 2 1/2" true duals running stock manifolds and high flow cats/mufflers, along with a little bit of head/intake polishing and have a noticeable increse in performance 2 ways = it will sound better and a nice sounding small block feels faster, it will also breath better making a little more power. These mods won't cost a lot and the stock carb/distributor and emissions equipment will work fine with it. A 200 4R from Bowtie Overdrives would be a more worthwhile investment than any of these IMO though.


-Justin

 

Since you're thinking about buying an '81 Vette with the intention of modifying it, you probably should become familiar with the requirements in CA. The Bureau of Automotive Repair web site http://www.smogcheck.ca.gov/stdpage....ck/default.htm is a good starting place. You'll find that it depends on where you live in the state effects the severity of the test your car must pass. If you spend a lot of $$ on mods and find out the car can't pass, you'll be very sorry. The smog crap is serious stuff here and not easy to circumvent. Finding a sympathetic test station might not be possible, as they can easily loose their license if caught.

On the bright side, '75 and older vehicles are currently exempt from smog test/inspections, so you can do anything you want to an older Vette.

Cheers and good luck,
Pete

 

I have an 80 and live in CA. There ARE some things you can do to signifcantly increase power like me and a lot of guys have done- and stay emissions legal. From the top: keep the stock dual snorkel air cleaner and your unique Q Jet. Get an Edelbrock EGR Performer intake manifold, or keep your stock aluminum one. Keep your AIR pump. Rebuild the HEI distributor. Get Edelbrock Performer 64 or 70 cc aluminum heads- they have an EO number and are smog legal. Get a mild torquey short duration cam, with a little more duration on the exhaust side, for the street- from Comp, Crane or Lunati- mine is a mild Lunati Voo Doo. Definitely better than your wimpy 195/205 @ .050. Get new smaller dish pistons- mine are KB hypers with a 12 cc D-dish. Your CR should be about 9.0- 9.6: 1 and no problem for our 91 high test. You can bore 30 over and rebuild the rest of the bottom if you want. You'll need to keep the stock exhaust manifolds; get a new 2 1/2 " Y-pipe and merge to a single 3" Magnaflow cat, then dual 2 1/2" pipes to your choice mufflers- mine are Flowmaster Delta 40's. These modifications should get you about 300 hp and lots of torque, and pass the visual and sniffer tests for a smog legal vette. Then eliminate weight- you already have a rear fiberglass spring, get better rearend gears, swap out the trans if you want, and improve the wheels and suspension.... it doesn't end. This recipe is NOT for NCRS guys- but your 81 WILL get up n go! Have fun with your engine build- it will be the best thing you ever do to enjoy your vette. JIM

 

I agree, you can still do a lot for little money, but I would put headers on it, true duals with high flow cats, change the cam and use a head gasket that crushes down real thin to up the compression ratio. OR, go to aa salvage yard and get a complete late model engine and harness but I think the exhaust
modification alone will give you a good boost.