amf133

What is the best cam for a 1981 corvette to gain power and still have good vacuum pressure? Some one told me to go with the .421/.451 comp cam, but wanted to see other peoples thoughts. I want to gain some power and have a deeper rumble to the car but don't want to effect the vacuum so the headlights windshield wipers excetra still work properly.
Thank you for your help.
Amf133

SIXFOOTER

On an 81 the vacume has nothing to do with the wipers. If your vacume system is up to scratch and not leaking much you can run a pretty bumpy cam and still have plenty of vacume for the headlights.
Cam selection would depend on a bunch of things, First off, what has been done to the motor? Exhaust, ignition? Is it stock, CCC system still functioning?
If your a bone stock 81, you will need more than a cam upgrade to get very far.
The 81 had a very restrictive head and exhaust and the cam matched that. The intake and carb and ignition will support a lot more motor than stock, 300 hp or better.
Any serious HP quest should start with better exhaust.
So, what ya got and what ya want to do with it?

amf133

i put a different exhaust on it other tan that the car is completely stock. i was going to rebuild the motor but keep it mostly stock. keep the intake manifold, CCC, heads, carb and distributor. was going to rebuild it due to it burning oil and having a bad baring in the bottom end. right now it has long tube headers, 2.5" with a balance tube (H pipe), no cats, going to delta 40 series mufflers. dont need crazy **** power just a little kick and want it to have that deep muscle car rumble when idling.

Tim81

I'm in the process of rebuilding my 81 as we speak. My goals for the motor are pretty much like yours, My advice is to get rid of those stock heads, the guides are probably bad and the machine work to bring them back to snuff will end up costing more then those stock smog heads are worth. A lot of people will tell you to switch to Vortec style heads and for the money they are right. There are some good earlier model heads out there that you can find for a good price. Just freshing up the motor will wake it up a lot. Those stock heads are some of the worse heads that GM ever made, most of the time they have cracks can not be repaired.. Good Luck Tim

SIXFOOTER

Good advice from Tim. Vortec is a pretty good way to go, but it requires heads and intake. You would still be able to keep the CCC system and all of that.
Check out the comp 168H series of cams, I think they are under $200 for cam and lifters

Jack Wood

Instead of saying what cam you ought to get, I can give you some tips to make a good choice. The 350 is happy with 273 to 283 degrees of duration. Higher duration means the same power but at a higher rpm. Long duration cams also need higher compression. Valve overlap shd be 50-75 degrees; lean toward the short side especially w/heavier cars and restrictive exhaust. For a good sound get a stick with 108 degrees of lobe separation angles, no less for a 350 engine. Stay below .500" of lift and 270 lbs. of spring pressure on the cam nose to avoid wearing out iron valve guides. Any camshaft Techline can use these specs to help you pick a winner and the springs to go with it. And use 1.6 rockers for a little extra power.

Vette5.5

I agree with most of the above, and just end up pulling the motor, to do it right. Head work's pretty much a given and maybe higher compression piston's too. As for the cam you're asking about, a few trick's availible for good street usage. Crane make's a Hi Intensity hydraulic lifter line that bleed's down lift/duration a bit at lower rpm's. Also, just because an advertised cam show's say a 110 degree LSA, doesn't mean you can't contact the manufacurer directly and get the same profile ground with a 114 LSA for a smoother idle and better vacuum. The torque will peak at a higher rpm, but daily street drivability will probably be better.