I have and 81 vette. Stock engine(matching numbers). I am looking to get the motor closer to the 300 HP I know that engine can put out. I am looking for opions and how to go about it with out tearing the entire engine apart. Have thought about the intake and a new carb, but not sure which type/size to use. Anybody?

 

These will get you close to your goal.

Cam and lifter combo.
Intake and carb combo.
Exhaust.

The cam and lifter choice can get confusing, so discuss it with professionals. Maybe call Comp or Crane and get advise about what would work best in your car.

Intake and carb speak for themselves.

Exhaust is anything that flows better than the stock exhaust. Maybe long headers, dual 2.5" pipes, and a pair of Magnas or Flowmasters. Side pipes too but they are very expensive.

 

Do a search (advanced search is best) and you will find all sorts of information. Read as much as possible, get confused, ask more questions, make a decision and go for it.

Good luck!!!

 

dont over look a tall set of gears!!!!! if you're rolling on 3.08's say and you jump to 3.90's its a very nice difference!!! anything over 4.00's though and you'll have the highway. specially on a 4 speed

as far as engine defenetly carb, intake, cam/lifters, exhaust. also a good full tune with the new stuff including the timing curve on the distributor

 

See what many refer to as my Exhaust topic.
http://www.corvettefaq.com/c3/ganeyexhaust.htm

For cam, at least trans. should be stated. Comp Cams 260H, XE-256 or more will get you close & over w/ better heads.
Q-J or 600 CFM will do it.

 

Just a note. Changing the rear gears is an expensive endevour. I would chock that one up only if the budget allowed it.

 

It'd be helpful to know what are your 'real-goals', and 'givens-and-druthers', for this car, before making suggestions:
do you just want to have 300 HP, without 'using-it' ?..... is miles-per-gallon an issue?..... will you road-race or auto-cross the car?..... is the car a daily-driver, where zero-maintenance is a concern?..... will you have to meet local EPA/emission laws?..... are you competing in the 'Stop-Light Nationals' ?.....

 

 

First off, if you have a stock '81 engine, you can't just throw an aftermarket carb on it. You would have to ditch the entire CCC computer system which would include the distributor. Major money, and in the end, it would probably downgrade your performance!

Bubba: "These cars are dogs! I've done everything I know to hot rod it and it's slower now than when I got it!"

I've got between 350-400 HP on my '81 with the stock distributor, carb and computer.

Your #1, best bang for the buck mod would be a set of headers and free flowing mufflers with 2.5" true duals. After that it gets involved. Heads, cam, pistons etc.

My best advice is this: Do the exhaust now. Wait till the engine needs a rebuild and get a good set of heads, flat top pistons and a cam. Unless you plan on doing all out (non-street) racing, keep the E4ME carb. God bless, Sensei

P.S. The stock aluminum intake is not bad either. Don't bother replacing it, you won't see a performance difference.

 

Last year I put on a 2.5" system with magnaflows and was amazed at the difference it made. Plus the sound...............oh baby!!

 

Is there a simple plug in chip that'll liven up an '81?

 

We just did my father in laws 1980 with a Comp Cams XE 268 cam(as far as you can go with stock TQ conv), Road Demon 725 cfm carb vacuum sec, and an edelbrock eps intake, hooker super comp sidepipes, by comp cams desktop dyno advanced he can hit 304hp at 4500 RPM with this set up.

 

Yes, there's a couple from Hypertech, though my experience of one, & what I've seen on here, seems to show that just changing the chip doesn't do a whole lot, apart from lightening your wallet. Fitting one with other mods (cam, CR, exhausts, etc) does liven it up a bit, though it's nothing spectacular.
As ever, a1sensei gives good advice regarding an '81.
If you have got the stock CCC system still in place (& it works) then a very cheap improvement can be got by advancing the base timing from the stock 6BTDC to anything up to around 13BTDC (I set mine to 11). This will advance the whole advance curve & you'll notice better throttle response at low revs. I swapped the cam out in mine & it lost some off idle power (probably as I'm still running a low CR with the stock heads & pistons??) & fitting a Hypertech chip & then advancing the base timing both brought a lot of it back.
Ganey's exhaust topic makes a good read and fitting true duals to mine was the best power mod I've done so far (hope I can say otherwise when I can afford a set of decent heads!).
If you've still got the CCC hooked up then I wouldn't advise fitting a 160 stat as the computer don't like it. A 180 is a much better choice (no matter what the books say - several '81 owners have run into problems with a 160stat fitted).

 

So timing, exhaust, and heads are #1. Intake is fine as is, and if #1 is met a cam and lifter combo will improve things as well with a computer mod or chip in place. Sounds right?

 

I agree but he said he didnt want to tear the engine apart and I would say putting on new heads is that. Really so is a cam. It would have been a lot easier if GM made these the way they should have. really, a sports car with 185hp? My Jeep inline 6 banger has 215hp. Someone should find the guy responsible for all gm v8's from 1972 to 1982 and make him pay to fix all our engines!

 

Hmm...see I thought tearing the engine apart would have been rotating assembly. No bearings or rings to replace when you change heads or cam...unless the cam bearings are bad.

 

Yes. The exhaust is probably the 1st thing to do & will get the best improvement. Changing the manifold out is something I'm not sure about as I'm not sure if it made that much of a difference (didn't get the weight saving normally got as the stock one is alloy). It looks a lot nicer with a new manifold though, & there's a better sound from under the hood, but as for a performance increase? It'd be something a dyno would show, my standard seat of the pants type testing was inconclusive!
What defines tearing the engine down? Pulling heads & cam aren't tearing it down in my book, ending up with the crank on the kitchen table is what I'd call a teardown. If you don't want to touch the engine at all then power increases after changing the exhausts aren't going to be that easy to find. Not sure what the climate is like where it is, but I got a nice improvement by junking a whole load of weight, eg. the aircon system, which is just coming at increasing the power to weight ratio from another direction.

185hp? The L81 had 190hp stock and that, along with the diet GM put it on, makes it a stonking powerhouse amoung the late model C3's Thinking about it, I've seen tables of power outputs for different year C3's, but has anybody got a table of power to weight ratios for '68 through '82?

 

This car has been a dream since I was a teenager and finally found one almost 20 years later. It is not a daily driver. I live in the NW and really only get about 3 month of driving a year. So when I get to drive it I want to enjoy it.( plus I am getting sick of getting blown away by my father and his 87 calaway). 192Hp has a good pull to it, but know there is alot more that is avalilble from the engine. I don't mind changing some part of the engine out, but want to keep it looking as close to stock as possible. I don't think I am ready to tear the rear end out yet, but the intake, carb and heads are well within reach to do. I am looking for suggestions as to what type and size fo carb and intake. The engine is stock now and I will be add alot of chrome to the accessories and while having things off I think I will start the preformance upgrades. I really don't want to change the look of the body at all( I like the look). So what ever I install need to fit under a stock hood.

Thanks for the info.

 

It took me a 20 year wait to get mine as well, but now I have, it was worth the wait
The first major thing I did was to change the exhaust system to true duals (Mid America ones). That gave a nice boost in performance. You'd better check if you legally have to have cats fitted, or if you can touch the system at all. If you do fit duals you'll find that bottom & mid range power is better, but as it gets to the upper revs it'll feel like power is being strangled slightly. this is due to the restrictive heads & manifolds. Changing the manifolds to full length headers really helped mine &, even with the stock heads, it's still much better than stock. Full length headers won't look stock(!), but if you do any exhaust changes have a think about whether you may fit headers in the future as fitting headers later will involve some fabrication & modification of the dual pipes. It would be easier (& cheaper!) to do the entire system in one go eg. get somebody to make an exhaust system to fit to the headers, or do it yourself like I did. You can route the system down the passenger side, or you can cut out a scallop in the trans x-member on the d.side (to match the p side one) & run one pipe down each side. I was lucky in that I've fitted a 200-4r trans & the custom x-member allowed a pipe down each side, but the principle is the same. Doing it like this means that you'll only need 2 bends in each pipe. I used Dynomax ceramic coated headers (1 5/8" primaries, 3" collectors) & got a couple of reducers from Summit that have an O2 sensor bung in them. With headers you'll need to richen up the secondaries &, assuming you have the stock carb & don't live at high altitude, swapping the stock CH needles for DA gets it about right.
If you don't want headers (as they don't look stock), I've read that the tubular manifolds used on the '82 aren't as restrictive (2 1/2" as opposed to 2"). I don't know if this is correct, but if it is then it will improve flow & still look stock. Or, just fit true duals to the stock manifolds as you'll still feel a big improvement.
If you do a search, you should find a few pics of various custom dual systems.

 

So Baron - What are you thinking you want to do, and where to start?