MsVetteMan

How would you spend $1500 to upgrade perfomance on my stock 1981 vette? Motor was overhauled about 5 years ago and it's a bit on the sluggish side. Everything is original except computer has been disconnected, but is still there.

Help me spend my $1500, and keep in mind, I don't do engine work, so I would have to have someone do the work. I would like to keep everything original looking and change things folks don't usually see. Not opposed to changing carb out and things like that, but no side pipes!

Spend on!!

vettedave

Well I couldn't remember if an 81 had crossfire or a carb so I did a search and came across this guys web site. Seems like he was in the same boat and has a lot of good ideas...

http://www.diabolicalperformance.com/performance.html

First I would get the carb done (hook the computer back up) , change the cam (lifters) put in 1.6 rockers, get the chip burned to compliment the cam etc., headers and freeflow cats and exhaust system. K&N air filter. Make sure distributor is working perfectly and add MSD- w/quality plug wires and platinum plugs. Should net you about 100 hp +-

MsVetteMan

Why should I hook the ECM back up?

skid

Buy a nitrous kit and have it installed for say 800 bucks. Add a true duals exhaust and headers. With the money left over take the wife out for supper. You are now running two seconds quicker in the 1/4 with a 150 shot.

Subfixer

The ECM keeps the mixture correct by taking readings at the o2 sensor, MAP sensor, etc.... Without the ECM on a car originally equiped with one, the engine is running in an "open loop" mode, which doesn't vary the timing or fuel flow with respect to the demand placed on the engine (i.e. wide open throttle, idling, etc...)

If it came with a computer, it will always run better if it's hooked up and working properly.

vettedave

You don't have to use the computer for performance.
You could put a holley 650 dbl pumper on it but gas mileage and drivability would suffer. Perhaps an Edlebrock 4bbl. would be a good comprimise.
Oh and if you change cams make sure the springs have good pressure and don't bind.

69stingray

I would start with the exhaust. Headers and a cat-back system. Maybe even a hi-flow cat.

MsVetteMan

How about NO cat.....dropped it today!! True dual exhaust!! Next.....

SpyderD

Hook the computer up? wtf? Rip the computer out!!!

Anyways you are on the right track, take out the cats and put on dual exhaust, you just increased your HP by a healthy 40HP or so.

For $1,500 you can buy a performance cam, goods heads (good heads will be the budget buster - you can get excellent performing Vortec heads at a bargain price), headers, an intake, and a carb and be close to 400hp with the stock bottom end.

btw - you will get great suggestions on the C3 forum, we don't need no "O2 sensors and ECM"'s there (and I know MS doesn't have smog testing).

The Money Pit

If you want it to look stock,but kick some butt for $1500,I'd get the rear end gears changed from the stock 3.08's to a 4.11,add true duals and get a tune up. You'd be amazed what snap you'll have out of a "stock" 350.

UKPaul

True duals & no cats will give a big boost in power. Once you've done that you'll find that the engine feels strangled at higher rpms. This is due to the stock manifolds (tubular type). Either fit headers (1 5/8" primaries & 3" collectors work well), which will mean hacking your new duals around, or try to get some manifolds from an '82 (which have a 2 1/2" restriction as opposed to the 2" restriction of the 80/81).
As the computer isn't hooked up get a strobe on it and verify that the timing is being advanced as the revs increase. If it isn't then it will feel very sluggish. If it is advancing OK then modify the advance curve (plenty about this in the C3 archives - Lars is tha man for this), Just by advancing the base timing on my '81 (with computer still hooked up) made an amazing diffrence in throttle responce & off idle power. Not bad for free.
I wouldn't worry to much about the manifold to start off with. The stock one on an '81 is ally so you won't gain any weight savings by changing it. I changed mine & quite honestly don't think that the cash was worth the difference (if there was a difference, I couldn't tell!). After fitting a new one I read on this forum that the stock one doesn't flow bad at all. Spend the money instead on something like a decent cam. That'll help to wake it up. What's really needed is a set of decent heads. Junk those smog ones & fit something better. Whether you go for iron or ally is up to you (ally saves weight at the front but can cause the ride height to increase. It also allows higher CR to be run & 64cc chambers are popular with stock pistons). I wanted ally so was looking at several heads & narrowed it down to a choice between AFR180's & TFS 23 deg. I went for the AFRs (the exchange rate is so good for me that they're almost affordable). I chose a 180 intake volume instead of the popular 195 as they flow very well at the sort of valve lifts I'm using (nearly as good as the 195s) but the higher gas velocity will give more low end torque, which is what I want.
Fitting some decent flowing heads, that also raise the CR, in combination with a better cam will really wake it up. The weak point of the '81 isn't the computer, as is often claimed, it's the smog heads & a cam that gives max power somewhere around 2000rpm, combined with an exhaust system designed as a huge restriction at higher rpms.
Once you've got a cam & heads sorted then is the time to think of a new intake manifold as any advantages of one now will be wiped out by the heads & cam. The cam I fitted in mine made little difference apart from losing a lot of torque that it used to have at 2000rpms. It's a bit better in the midrange but nothing spectacular. People with the same cam, combined with decent heads, report far better results for the simple reason that the cam was designed for a higher CR than the puny 8.2:1 stock reading & needs heads that flow well.
After changing the exhaust it's pointless skirting around the issue by fitting bolt on goodies for added power. The thing to do is to grab the bull by the horns & sort out the poor flowing heads, the smoggy cam & bump up the CR. Once you've done that you should be on a par with earlier C3's that have had the same sort of mods done, or maybe better as the L81 lost a lot of weight in a factory weight saving program. A really cheap way to increase performance (& improve handling) is to lose some weight from it. I junked the aircon from mine & that pile of bits weighs a surprising amount. Acceleration may have improved now it's gone but the steering definitely feels more reponsive due to it.
If it's an auto then increasing the stall rating can give better off the line acceleration. If you do any significant amout of highway driving then don't change the rear end to a very low ratio as it'll be screaming along when cruising at highway speeds.

An easier thing to do is take a different approach. Ignore all the BS about '81s as without the ECU controlling it you've effectively got an '80 or earlier. Just check out a few peoples sigs & compare mods & times, then copy the one(s) that appeal to you

For $1500 you should be able to change the heads & cam (& have change, depending on what heads you go for),

DaveL82

I have a 1980 vette and I tried many upgrades over the years with various levels of success. I now have a ZZ4 motor which is way over your bubget but I think with the right choices you can come close.

I run my ZZ4 with the stock rams horn exhaust manifolds and let me tell you they flow great and are rated as on of the best stock exhaust manifolds. If you check out Brezenski racing they build exhaust systems for stock car racing and make great power with the manifolds. I recommend putting your money else where instead of headers since you also raise the heat level in the engine compartment and also have to deal with leaks periodically. Try removing or updating the stock converter to a high flow unit. Mufflers can be really restrictive so put high flow units on. With these changes you still have a lot of budget.

Pull the ECM (no cost), replace the distributor with a rebuilt unit from a 1980 sicne it does not require an ECM. Buy a used intake such as an Edelbrock performer.

Buy a rebuilt Holley with electric choke or look for a deal at jegs or Summit on a new one.

To make the power I would go with a roller cam conversion, this will cost about $600 to $700 dollars but would give you the real boost in power and saving on the other mods may allow this to just fit in your budget.

Used or rebuilt higher flow heads are also an option. The L98 aluminum heads can be found cheap and would give a good compression increase.

supervett77

Alright dude buy a holley 750 double pumper. and slap some air flow research heads on that beotch. Theres your 1500 right there. But as soon as you get extra money. Buy a edelbrock performer air gap 200 bucks, and get a matching cam ( go hydraulic or roller cam). Youll make power right quick.... Or just juice her with some nitrous. She should handle a 100hp shot just fine

UKPaul

I've read about those reworked rams horns. What I read said that they were done for racing where stock componants need to be used (cheating!) & that they can be made to flow very well, nearly as good as Headers & are a great alternative to Headers. BUT, the Dynomax ceramic coated Headers I fitted are affordable, still look good after 2 years & have caused NO heat problems at all in either the cabin or engine bay. They sales hype about ceramic coating keeping the heat in appears to be true as not only have they not cooked me & the engine bay, they also keep my O2 sensor at a high operating temp, even though it's located in the reducer which is much further downstream than it used to be. The engine bay actually seems cooler with the Headers than it did with the stock type system but I never measured the temp b4 or after & am only judging by the lack of hot air blasting me in the face when I open the hood now (it doesn't feel as hot as it used to which is the complete opposite of what I expected to happen).
Another option would be to fit the stock tubular manifolds from an '82 model (less restrictive) but finding a good set may not be easy.
Why? (It's not connected anyway!!!). If it were connected then what will pulling it do for him? He'll have to spend a chunk of his limited budget on replacing the carb & distributor (and will have to fit a method of locking the TCC if it's an auto) & where will he be at then? He'll be in the same position as an '80, or a '79, '78.... which are just as much a slug as an '81. Where are the figures that show the '81 as a lot slower than the preceeding models? If you look at the figures (stock) you'll see that the '81 has actually increased hp over some earlier years (by about 5hp I think. Lookout! ). The ECU is NOT the limiting factor on power, it's the same smog crap that earlier models have that's the problem. What I'm saying is to modify the car in the same way as you would an '80 ('79, '78...) & keep the ECU in place if it's working OK. There's nothing to be gained by junking it if it's working. If you're going for a lot more power which involves cams that give a low manifold vacuum at idle then the ECU won't handle it, so junk it in those situations, but if the cam has a good idle vaccum then save your money for things that will make an improvement.
I did and didn't really notice much of a difference (at least, not £120 of difference - it felt more of an improvement when I advanced the base timing by 5 degrees I feel cheated ).
So the E4ME will be in the trash, but what will he have gained? An easier to understand carb isn't worth the money, I reckon. I'd rather spend some time over a few beers reading the workshop manual & Doug Roe's book on Q-jets & work out how the E4ME does its thing. The secondaries are just as easy to tune as any other Q-jet & the primaries (once set up according to the instructions) adjust themselves dynamically. What could be better than a self adjusting carb that copes with different air temp/pressure, etc (yeah, I know, fuel injection!)? I expect the people who are producing in excess of 400hp will jump on me now, but if you're looking for around 300hp the E4ME should work OK at no extra cost other than a couple of secondary rods (esp. if he's got an upgraded chip in the ECU - even if it isn't connected! ).
True, but does that include the cost of fitting? Without knowing what power he's after, he may be better off getting a hydraulic lifter type cam fitted as it'd be cheaper? To get the true potential of a roller (or any other performance) cam then decent heads/exhaust/intake would be needed. Having somebody do the work would quickly run over the budget.
Good idea.
Plus the cost of fitting them 750 double pumper see above (if the ECU is disconnected, then what's it running at the moment? If it's the E4ME then improving performance will be easy as it'll be running the primaries full rich & the dist won't be giving any advance: "Everything is original except computer has been disconnected, but is still there").
AFR heads will be a real beotch alright. They'll be a beotch in heat with it's *** in a hornets nest as AFR have had a machine down for 3 weeks & now have a large backlog. That's what I've been told as I've just heard that my heads will be a few weeks yet before delivery (& I had hair when I ordered them ). If I had the heads then I'd be able to say what changing heads does for an L81 from personal experience (the experience of others is that it really wakes it up). At the moment, with the mods I've done, by far the best was dual pipes. That mod was head & shoulders above the others & I'd recommend doing it before anything else (or even instead of anything else with a limited budget). Headers made a difference higher up the rev range, but if you're getting dual pipes fitted then it'd make sense to get the Headers on at the same time (get it all done & once & keep labor costs to a minimum & end up with a system that fits OK). I used copper manifold gaskets (they'll eat a small part of the $1500!) & bought some "normal" stainless steel allen head set screws & spring washers. I fitted the Headers with these set screws (being allen head you can get a key in there to tighten them easily), ran the engine up a couple of times until hot (& left to cool down) & nipped up the set screws (a set screw is just a bolt with the thread all the way up the shank). I've not had to touch them since, no leaks, no loosening off, just fit & forget.

TIMSPEED

1.) Headers & dual 2.25" Exhaust with straight-through mufflers
2.) Higher Stall Torque Converter (2000rpm should be perfect)
3.) Tune that Quadrajet
4.) Regear the car (depending on what gears it has, if they're close to 3.73's, leave em', if not, get 3.73's)
That right there should make that 81 run pretty good.

vetred

Wellllllllll,.........sence you are going to spend at least that much for labor just to change the plugs these days,...............I think I might look at the "Jim Beam" up grade,......thats I think the Booker Noe limited production model