Leo001

I'm considering upgrading my stock L48 heads for a set of Vortec units (the L48 need a rebuild) I know this will necessate an intake swap also, and "while I'm at it" maybe a cam upgrade (Comp cams 262) I wonder how much of a performance this will yeild, I just don'f feel like pulling the whole engine and doing a complete rebuild.
Any Thoughts??

Leo

Solid LT1

With a cam you should see a 60-80HP gain it will make a great difference. Try Weiand for a cheap USA made Vortec intake that will fit under your hood.

Durango_Boy

You can also get an Edelbrock Vortec manifold pretty cheap on Ebay.

http://cgi.ebay.com/ebaymotors/ws/eB...MEWA:IT&ih=013

BKbroiler

I made the same changes PLUS converting to 383, higher compression, headers and full duals. The difference is like night and day. Assuming your bottom end is in good shape, your improvement should be substantial.

Glensgages

80crabvette recently did a similar swap (vortec heads, RPM Air Gap intake, Street Avenger carb, and 270H cam {original EX268H wasn't broken-in properly, and wiped-out lobes} ), and has his back on the road:
they are working the bugs out of the tune-up, but I think he is very-happy with the car's performance.

The upgraded-heads, head-gaskets, intake, gaskets & bolts came from Scoggin-Dickey Performance in kit-form.

http://www.sdparts.com/product/SD806...RPMAirGap.aspx

swoodard23

http://www.chevyhiperformance.com/te..._iv/index.html
Good article on the upgrade. Google I, II, III, IV, V for more on the build up.
Scott

Leo001

Will that intake (RPM Air Gap) fit under the stock hood on a 74?

Glensgages

..... the RPM Air-Gap/Street-Avenger, with a drop-base/open-element air-cleaner, fit under the stock hood of an '80, which appears to be even-lower than the mid-'70s C3s:
I'll forward 80crabvette this link, and maybe he'll chime-in.....

Durango_Boy

Yes, with a drop base air cleaner.

billla

The Vortecs alone are worth nada with the anemic GM 3896929 '390' cam. The XE262 is a good choice and right at the edge of what the stock (upgraded ones are available that will go to .525 and beyond) Vortecs will allow for lift - but you'll still want check the valvetrain geometry. The Performer is a good choice; I'd pass on the RPM as the cam runs out of smash at around 5800 RPM and the RPM intake won't show significant benefits until just about that point...and you're sacrificing some low-speed driveability.

I'd expect to see more like 45HP at the flywheel increase, but the "seat of the pants" feel will seem like significantly more due to a 60+ TQ increase. If orginality isn't a problem, headers will add another 20 HP and 30-50TQ for a long-tube.

All IMHO It's a nice upgrade; I've done a few Vortec top-end swaps and everyone's been really happy so far.

Note that you need self-aligning rockers - roller tip are nice - and either new valve covers or adapters (<-expen$ive)

Crab

I can tell you that the Air Gap will fit under a 1980 hood with a 3 inch drop base filter.
As far as what you are planning , I say do it, you won't be disappointed .
I got everything from Scoggin- Dickey out of Lubbock,Tx.
We went with the upgraded head kit that allows for more lift(.525) with heavier valve springs and screw in studs versus the stock vortec heads with pressed in studs and lighter springs(.450) max lift.

A cam choice was where my biggest problem started, CompCam XE268h was the 1st cam we tried and it wiped out during break-in, prolly from a combination of improper break-in and a poor cam design. I don't like the XE line of cams , it was very ,very noisy during break-in and the 100 miles or so that I drove the car before we realized the cam was gone.
Something real important is, buy the cam break-in additive that CompCams sells for their cams. It is a little pricey, but not as much as replacing the cam
CompCams did replace the cam and we then went with a Magnum 270H cam that is old design that has been around for many years.

I'm fairly happy so far but there is still some carb issues and some final tuning. I'm trying to keep the RPM's under 3000 for about 500 miles so I really have'nt got to open it up much, but above 2500 RPM is where you can notice the differance. I also added DynoMax ceramic headers.
Billa, who has a lot of good data was good enough to do a Desk-top Dyno for me, you can check out the resultsin the thread below:
http://forums.corvetteforum.com/show....php?t=1793426

DiamondDave80

Were you at Carlisle this year? Your car is imacculate

Crab

My wife and I were there for the day on Friday this year without the car.
Last year we entered it in the NCCC car show at Carlisle and it took so much of our time to do the show that we missed alot.
Thank you,

ptroxx

SO you guys are all doing this without a bottom end rebuild????
My car has 50k on it and runs real good.But it does smoke when i start it in the morning(valves?? ) But i want a little more.
So i can do this heads and cam and intake and not have a problem??
cause for about 1100 you sure can get some HP..

Durango_Boy

George - Depending mostly on how much you can get a set of good Vortec heads for this Vortec project can cost a lot less than $1100. The heads would be best with some milling so they can accept a cam and springs with close to .500 lift. That and the new springs would be a bit on top of the heads. Then you need the cam and lifter combo, like suggested from Summit, a Vortec intake, and some gaskets.

Heads - $400 (After machine work.)
Intake - $150
Gaskets - $80

Again it depends lot on finding the heads in a salvage yard cheap but it can be done.

BKbroiler

Don't forget the self aligning rocker arms, valve covers and new plug wire supports.

ptroxx

Matt, I noticed in Summit

summit has a set of gm vortex heads for 600.00
intake on ebay 110.00
cam ?? 150.00
But what about the bottom end?? with 50k miles and 30 years on it will it handle the power??

Bric

billla

The best deal if you're looking for over .475 lift is to buy the head already modified from someone like Summit, SDPC or others. In my experience the cost of overhauling a used set of Vortecs including machining for higher lift will exceed the cost of NEW upgraded heads.

It's important to note that the flow levels out at about .450 or so for the stock Vortecs, so I'm not convinced of the value of upgrading to handle lift beyond that. If you're looking for more than .475 lift, then IMHO you should be looking at other heads. The stock Vortecs are the budget-builder's friend - but only up to about 1.2 HP/CID max. GMPP makes better Vortecs in their "small port" and "large port" versions which are outstanding, and of course there are plenty of aftermarket choices.

billla

"handling the power" of a 40HP/50TQ upgrade isn't a problem Frankly, it's not so much the increase in power as the heavier right foot it encourages that causes problems If you've been cruising around at 4500 RPM for 30 years and now decide to see if the redline is really 6K, that's when things will get interesting.

This is also kind of one of those "while we're in there" discusions. A stock bottom end with 50K on it is fine, but a 383 is nice, and maybe forged pistons so I can spray it and...

All of the sudden you have a floor full of engine parts and a $3100 Summit Racing charge on your VISA that you have to explain to the SO