So I scored a set of Vortec heads for 50 bucks, I am taking them to my machine shop to have them checked out and am thinking of running them on my 89 L98 Iroc Z.

Assuming they check out and I decide to use them, I just wanted to get everyone's opinion. So I am trying to find a 350 TPI dyno where the only thing swapped were the heads and a sdpc intake.

My thinking is that the dynos I do find all are Vortec heads with an aftermarket cam as well such as the lt4, and a lot of them still peak around 4800 to 5000 rpm. I am basically wondering, even with the limitations of the sdpc vortec TPI intake and stock cam, how much horsepower Vortec heads could add to an otherwise stock L98.

Thoughts? I have ruled out the stealth ram due to hood clearance.

 

I would say you could probably gain 30-40 dependant on the cam and tune. It will gain more torque that horsepower. Which if the car is mostly street driven thats kind of what you want.

 

Yeah, keep in mind the Vortec heads are a LOT more efficient, but still aren't really a big head, and don't flow a ton. That makes more power under the curve, which is good. They still reach their potential (relatively) low in the power band. Again, with a TPI, can be a real good match. Even with a stock cam, I think you'd be real happy!!!!! .....but why NOT go a little bigger with the cam?

 

Well I don't mind going with a bigger cam, that is what I am trying to figure out I guess. I have found side by side flow #'s in Car Craft that say the Vortec heads flow almost 40 cfm more than the L98 heads on the intake, and only like 10 more cfm on the exhaust.

What I am wondering is this: even those who have gone to an LT4 cam or another bigger hyd. roller cam seem to still be making peak power about 4800 rpm, well below where their camshaft is supposed to peak. So I am wondering, basically what a dyno would look like with just the heads swapped.

 

The Vortecs seem to lose their luster over .500 lift, so obviously a cam that goes beyond that is overkill. The key would be choosing the right cam.

 

i would go lt4 hotcam with 1.5 rockers.... would be .492 .492 lift......

 

http://hobracing.com/featurecars/1989GTA/1989gta_1.asp

no dyno, but tons on track times, very helpful to show what modifications can give you, this is close to what you are looking for

im doing this swap right now with the lt4 hot cam, i suggest you drill the push rod holes out to 1/2 inch so you can have enough clearance to run 1.6 roller rockers before you install it

 

I've heard others say that there isn't room for 1.6 rockers, but on my motor I seemed to have plenty of pushrod clearance.

 

This is such great info thanks this is exactly what I was looking for. Was he running a stock camshaft then?

 

everything I have read about the SDP vortec base says that it flows barely better than stock, Which is why I opted for a FIRST TPI vortec setup for the vortec 350 I put in my jeep. Flows way more than you ever will with the SPD or edelbrock tpi base and runners.

 

yes from what i read that was the l98 camshaft, i just drilled out my pushrod holes the other day by the way, just flipped the engine upside down on the engine stand and drilled them out, pretty simple, just make sure you spray down the heads really good with carb cleaner before you flip it back over, i used 2 cans and it was clean after that, but its a different story if the engines already in the car


and ive done hours of research on truck forums, everyone ended up drilling out the pushrod holes to safely run 1.6 roller rockers, im going to run the comp cams magnum (1418-16) 1.6 rr, but from what one guy said it only shaved off one tenth in the quarter mile and gave him a few mph by doing that upgrade

 

If I get a chance, I'll snap a couple pics tonight. I recall having at least 1/16" of pushrod clearance. I hope like hell I'm right, or I'm going to have a lot of carnage.