I really have no idea which one would be a better buy. Considering the L98 heads are a direct bolt on (no TBI intake manifold required and can handle higher valve lift) they come out to about the same price as upgraded Vortec heads. Which one would you guys vote for?

 

I would go for the Vortec heads. They are around $320 with the spring upgrade and will out flow stock L98 heads. L98 heads from Scoggin Dickey parts center that have had a bowl job are $1300, and probably flow close to Vortec heads.

 

I saw flow numbers in a mag for ported aluminum L98 heads and they weren't anything to get excited about. Apparantly there is not much material, so modifications are limited.

 

The Vortecs, hands down. Chevy High Performance tested the L98 alum. heads against the Vortecs quite some time back, and the Vortecs made quite a bit more power over the entire RPM range.

 

I strongly regret my decision to go with 'ported' aluminum L98s, a 105mph trap with a hotcam is pathetic.

 

The Vortecs and a decent cam, along with a Performer RPM Vortec intake will wake that 305 up pretty nicely. If you got any specific questions pm me

 

Some more questions regarding the Vortec heads:

1. Is it imperative that I mill the chamber from 64cc to 58cc or can I get away with it?

2. I noticed that the 'basic' Vortec head valve spring can hold up to 0.450 Lift. The LT1 cam has an intake lift of 0.447 and exhaust lift of 0.459. Does that extra 0.009 Lift mandate that I buy the 'upgraded' heads with Z28 Valve springs and LT4 retainers or will it be alright?

3. Do 'lightweight retainers' do any good performance wise?

4. What is that adapter people talk about to get the performer intake onto the TBI unit?

Thanks.

 

Answers:


1. Yes, you need to mill the heads.

Car Craft did a test a few years back on an 80,000 mile LG4 305 given to them for free. They ran Vortecs milled down for the 305 chamber size, and an XE 268 cam. They got 325HP out of this engine with an RPM intake and 750 Holley carb. That's pretty impressive for a used 305 engine with dished pistons.

2. Vortecs are good to .460" lift stock. You'll be okay for your LT1 cam.

3. Vortecs already come with a thin retainer.

Any time you lessen the weight in the valvetrain, useable RPM's will rise somewhat. Is it worth the expense to go out and buy light weight retainers for an LT1 cam? I wouldn't bother. You can grind 3/16" off the bottom of the Vortec retainers and lose a gram or two of weight there if you want, not to mention gain lift for a hotter cam if you want more lift. Thats all I did for the .488/.510 Crane flat-tappet hydraulic with ported Vortecs in my '77 Z/28, and no problems to report so far. (I should add, I upgraded the springs to stock-diamteter Crane's at the same time.)

4. Its common knowledge that the Performer TBI intake is less than stellar in the HP dept. over the stock intake. So what guys use is a TBI to carb intake adapter to be able to run the Performer carb intake with the TBI unit on top.

 

So you're saying the performer intake for TBI is actually worse than the stock intake, but the performer CARB intake is better than the stock one in my car? What's the part number for the CARB intake?

 

Something to keep in mind is that you will HAVE TO change intake manifolds to use the Vortec heads. If you are willing to pay this extra cost, then go for it.

But if you are tight in the $$$ dept., you can port and polish those aluminum heads and get terrific performance out of them. They can be made to flow even better than Vortecs, AS LONG AS YOU DON'T MIND DOING THE WORK YOURSELF!!!

Follow the link at the end of my sig for comprehensive instructions on doing all of the porting and polishing yourself.

You CAN do this work--it is NOT hard. It only requires that you invest about 25 to 30 hours of careful workmanship in the heads.

 

No, the TBI intake is not worse, but it is no better. Certainly not worth the $ for all the hassles to change an intake.

SittingBull is correct; the Vortec head takes a specific bolt pattern. Edelbrock offers a Performer, Performer RPM, and Super Victor intake for Vortecs. Go with the Performer. Don't know the PN# right off the top of my head.

 

I just remembered: Scoggin-Dickey makes a TBI intake for Vortec heads. That might be your best bet if you want to go Vortec. I think its also in the GM Performance Parts catalogue as well.

 

Vortec all the way

 

I guess you really dont have to mill them down .040 like hot rod did, but it helps. Mine are down .020 with the fpp-1094 head gasket thats only .017" thick compressed, so my compression is about the same as stock. I use the Performer RPM Vortec and like it a lot with the LT1 cam. I didnt get nearly the gains I wanted out of it, but (I think) its fuel related as the stock pump is only putting out 13.5 psi on stock injectors. Im putting in a walbro 255 whenever I can get home and I'd like to run about ~19 psi with 80 pph injectors, we'll see how that works

 

What numbers are you putting down Chuck? Anyone else care to share dyno#'s?

The problem with Vortec all the way is that it costs about $200 more than Vortec + Performer Intake.

So to maintain my Compression I have to have 58cc chambers?

Thanks for all the replies.