I just purchased an 81 vette, tuned it up, removed the stock air intake, and put in synthetic oil. I also removed the air pump and disconnected all the related tubes. I will eventually upgrade the exhaust. It has a 350 and I know that the compression is weak.

I am looking for the best carb to upgrade to without changing the manifold. Also any additional advise to get some more horse without changing the motor. Also wondering if upgrading the valve covers would benefit at all...

Thanks,

newc3guy

I just purchased an 81 vette, tuned it up, removed the stock air intake, and put in synthetic oil. I also removed the air pump and disconnected all the related tubes. I will eventually upgrade the exhaust. It has a 350 and I know that the compression is weak.

I am looking for the best carb to upgrade to without changing the manifold. Also any additional advise to get some more horse without changing the motor. Also wondering if upgrading the valve covers would benefit at all...

Thanks,

newc3guy
a carb change wont help that motor, compression too low, cam is weak poor heads ignition is not designed for performance, its a smog motor and to make it worse ,its got either 2.72 or 2.87 gears

I just purchased an 81 vette, tuned it up, removed the stock air intake, and put in synthetic oil. I also removed the air pump and disconnected all the related tubes. I will eventually upgrade the exhaust. It has a 350 and I know that the compression is weak.

I am looking for the best carb to upgrade to without changing the manifold. Also any additional advise to get some more horse without changing the motor. Also wondering if upgrading the valve covers would benefit at all...

Thanks,

newc3guy

Hi New C 3 guy from Ill,

I need a little more information…
If your Engine is original, your factory compression should be around 8.2 to 1...
Also depending on engine ware and mileage...
And if you have the original carburetor and fuel system, be careful because the 81 corvettes have a "computer command control" The Computer regulates the amount of Air, Fuel mixture to the carburetor...
I see that you removed the stock air breather...
The design is to bring in cold air from the front of your vette, if you changed the breather, to one of the type from on top of your engine it will breathe only HOT air from your engine and engine compartment...

As for more horse power...I will need to know your engine ID numbers, to answer your Questions...your ID numbers are located on the passenger side of the engine just under the front of the head... you should see two sets of numbers , large set and a small set...
I believe we can make your vette run out real nice...:goodpost:


Kev...

a carb change wont help that motor, compression too low, cam is weak poor heads ignition is not designed for performance, its a smog motor and to make it worse ,its got either 2.72 or 2.87 gears

What^he^said. Crate motor time. Or build a 383.

What^he^said. Crate motor time. Or build a 383.
yeah, if you consider just swapping out motor for upgrade, contact Patriot Performance.com. 350Hp on up i have their 383cu. in./ 500Hp

I have done a little research, and have found a few thing you could add to enhance your HP...:thumbsup:

i also have a 81 replaced carby new hei no cats i didnt notice any real difrence put new exaust from factory headers (extractors) 2 " into 2.5" back to duel 2" sounds great but went backwards lost some torgue

Do you know what i'd do? Wait & try to find the best used engine your willing to pay for. I would try to find a decent mileage 350 vortec, they have great heads, roller cams, good comp. ratios & they seem to run along time. Get the used engine, swap a Vortec manifold (4bbl.) Get rid of the plastic timing cover, try to find a 86 up vette oil pan & pick up tube. You'd have to run an external by-pass for the coolant (easy to do). Switch over the exh. manifolds, water pump, & other accesories. I bet if you did all the work yourself, it could be done under $2,000, depending on the cost of the motor & intake.
Just make sure you clean & paint everything, that good for 20 H.P.:burnout: :burnout: :burnout:

I just purchased an 81 vette, tuned it up, removed the stock air intake, and put in synthetic oil. I also removed the air pump and disconnected all the related tubes. I will eventually upgrade the exhaust. It has a 350 and I know that the compression is weak.

I am looking for the best carb to upgrade to without changing the manifold. Also any additional advise to get some more horse without changing the motor. Also wondering if upgrading the valve covers would benefit at all...

Thanks,

newc3guy


To get some performance out of your 350" engine, you'll have to increase it's compression ratio to at least 9:1 and install a performance camshaft in it. And if you have the money, a new set of performance cylinder heads. And a performance intake manifold. The original carburator will flow 750 cfm already, so a simple jet/metering rod change will boost it's performance. If you don't have to have it smogged, the possibilities are endless and the sky is the only limit.

So far on my 350 79 vette I have only added a new carburetor which was from a 600 cfm to a 850 cfm... I want to make the 12.50's on the 1/4 mile at the track but right now with what i've done it's running 14.80

I was going to buy some Vortec Heads & Intake for a total of $350...? As well as maybe adding a performance cam...? Does anybody know any good setups with Vortec?

Any advice, setups or tips...? Any information would be great! Thanks! :)

your carb is much too big for your motor

So what do you suggest or think i should do?

Should i go back to a 600 cfm carb and go with the vortec heads and intake or whats the best route...

btw how is it too much for the motor? Just out of curiousity...

So what do you suggest or think i should do?

Should i go back to a 600 cfm carb and go with the vortec heads and intake or whats the best route...

btw how is it too much for the motor? Just out of curiousity...
an 850 cfm is more suited to a big block engine or a radical smallblock your motor cannot flow that much air so you loose velocity because the bores are too large makes for poor low and medium performance, for example , my 383 stroker motor produces 501 HP @6200rpm with a 750 cfm Quickfuel carb and still maintains loads of low to medium power bigger is not better. matching head flow ,cam lift and duration with carb cfm thats the path to HP edelbrock has some excellent head,cam manifold pkgs all matched and if you can afford it , full roller cam worth every dollar over flat tappet

A good way to figure out if your 600 cfm is to small, hook a vacuum gauge to manifold vacuum source, if the gauge does't fall to zero under hard accelaration you could benefit from a larger carb. This only works when the engine is under a load, so revving it while its in park won't be accurate.
I'm sure Edelbrock would have a good recomndation for a cam/heads/intake combo.

just had my rear gers swaped to 373 motive was the brand name and now waiting for the 2700 stall converter for 4l60 trany to do the whole job in one go does any one khow what the stock headers on a 81 are like

just had my rear gers swaped to 373 motive was the brand name and now waiting for the 2700 stall converter for 4l60 trany to do the whole job in one go does any one khow what the stock headers on a 81 are like
are you talking about the factory short tube exhaust with the A.I.R. tubes into each? are you still using the pump? its draining HP

no the pump has gone and most all bits taken off i would like to know if welding up the air holes is worth it or are they crap and need to be junked but in oz we are rh drive and of the shelf headers may not fit now the steering box is on rh side of car

no the pump has gone and most all bits taken off i would like to know if welding up the air holes is worth it or are they crap and need to be junked but in oz we are rh drive and of the shelf headers may not fit now the steering box is on rh side of car
a good set of headers would be an improvement over stock but i really don t know about right hand drive check with Summit racing.com or Headers.com they can tell you

did some reading on 700r4 {4l60 } trany swap to go with my 373 diff gears and read an article in corvette fever forum step by step photo by photo how to do the job exept small mistake it stated that the drive shaft be shortend by 1 1/2 inch so i did to have all parts ready to go only to find that th350 to 700r4 the length diference is 3 inches so not only am i $100 bucks out of pocket but will need to wait another week for my shaft to cut again question is am i the first to follow their instructions how old is the artickle why hasnt it been updated with corect info this is just @#$%$#@#$%$#@ i need another beer now

Welcome to SV newc3guy.
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Can't help on the horsepower but am happy you decided to join the best Corvette Forum on the net. Remember to save the wave.....

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did some reading on 700r4 {4l60 } trany swap to go with my 373 diff gears and read an article in corvette fever forum step by step photo by photo how to do the job exept small mistake it stated that the drive shaft be shortend by 1 1/2 inch so i did to have all parts ready to go only to find that th350 to 700r4 the length diference is 3 inches so not only am i $100 bucks out of pocket but will need to wait another week for my shaft to cut again question is am i the first to follow their instructions how old is the artickle why hasnt it been updated with corect info this is just @#$%$#@#$%$#@ i need another beer now
wow, i could have helped on driveshaft, i did the conversion th350 to 700r4 this year its 3inches exactly you will be pleased with the result, trust me major improvement in holeshot and hiway driveablity

I just purchased an 81 vette, tuned it up, removed the stock air intake, and put in synthetic oil. I also removed the air pump and disconnected all the related tubes. I will eventually upgrade the exhaust. It has a 350 and I know that the compression is weak.

I am looking for the best carb to upgrade to without changing the manifold. Also any additional advise to get some more horse without changing the motor. Also wondering if upgrading the valve covers would benefit at all...

Thanks,

newc3guy


What are your ultimate goals? And changing the valve covers won't accomplish anything other than making your engine look different than it does now.

An 850cfm carb sounds very big for a small block.
650 cfm should be plenty if you tune it properly.
Alot of big blocks only run 750cfm.
I would say pull the engine and send it to a good tuning shop that you trust. Balance the crank, new bearings, pistons, heads and cam and you'll have a little rocket. 350 horse is a lot of power and should be plenty above 400 and you start to break things. It's no good having loads of power if you can't get it on the tarmac. gearboxs, drive shafts diffs aren't cheap. Worth considering what you want from you vette.
Just my 2 pence worth, good luck:thumbsup3: