I'll going to change my heads and wanted to make if the aluminum L98 heads from a vette are the exact same heads as the ones that come with the zz4 crate engine.

 

The aluminum L98 heads flow absolutely terrible for a "performance" head.

 

if you can swing it go with the fastburn....

if you can't i'd have the stock L98 ported and polished.

alot of it depends on the intake your using as well as the money you have to burn. aluminum just costs alot more obviously.

 

Yes they are the same heads.

They work very well when *Fully Ported* and bigger 2.00 x 1.55 valves are installed.

TPIS and CNC cylinder heads sell these in CNC ported form.

 

Per Scoggin Dickey Book it appears to be the same head.

Why not buy the vortec. 1/2 the price and flows more than the fast burn or the L98 at any valve lift. (comparing as cast head)

 

Will they out flow a stock lg4 head?

 

yeah they will, they dont flow that bad. Its just over 200cfm at .5 lift if i am not mistaking.

 

Look up Alexparts or Vortec heads on E-bay. This guy is selling Pro-Topline's version of the vortec head. for less that 700 dollars I got these heads. They come with the quality casting pro topline is known for and on top of that Alex machines them for dual springs matched to your cam specs. His kit also contains swirl polished under cut valves, screw in rocker studs(the heads are already machined for), chromoly retainers, viton positive seals, and all the other stuff needed to make a nice head. The pro topline vortec is already set up for guid plates if you want to run them also. I could not find a better deal.

 

Bubafett, are you sure out of the box vortecs outflow out of the box fastburns at any lift. I don't think that is the case.

 

I must say that I am very happy with my "ZZ4/ vette" heads. I paid next to nothing for them and had them completely ported. I have just over $900.00 in them.

 

"performance" or "hi-performance". Weren't they designed especially for the Vette..And I thought the Vette was reborn with some ***** around that time

 

have any flow numbers on those 900 zz4/vette heads?

are the L98 vette heads or zz4?

 

229cfm on the intake side at .550 lift with the lower intake and runner on. The exaust was 197cfm @.550 . The heads were flowed on SF600 . I'm look for my flow sheet. I will post the low lift numbers as soon as I find them. They were not to bad. The intake side did take a poo at .550 . If I remember correctly the .500 lift numbers were like 227cfm with all the intake stuff on. they are off of the zz4. Does that make a diff? I thought they were the same heads. Please let me know.

 

lift INTAKE EXHAUST
.100 62cfm 58cfm
.200 112 108
.300 146 142
.400 189 178
.500 227 190
.550 229 197
.600 --- 208

 

for argument's sake, here's the flow bench numbers from my bare heads. they are 062 vortecs, with a 3 angle vavle job and mainly exhaust bowl work, and a lil bit of intake side bowl work. and stock valves.


This is at 28" of water

lift_ int._ exh. _ Ratio.

.2 142.5 103 72.3%

.3 193.1 138.8 71.8%

.4 220.9 153 69.3%

.5 222 176 79.3%


They also did a quick shot at .5lift with the intake on it at the intake numbers were over 230. didn't have the headers yet to see how much higher they'd be.


I'd rather have these heads than the L98 heads, the combustion chamber is much better, at 10.7 compression no detonation problems either. It's just a better design. The flow numbers also work very well with my XE274 camshaft that stops just short of .500 lift.

Total price on the heads, including heads, springs, the machinework, including decking, flowbenching, installing hte springs, and intake gaskets, and bolts, was 930.

 

All of my flow numbers were with the lower intake and runner on the heads. I'm really did not care what the heads would flow with out the intake stuff on. They have to flow through the intake system when there on the motor anyway so those are the only numbers that really matter (IMHO). I still agree with you about the chamber design of your heads. BTW my compression ratio is 10.9:1 and I have no detonation problem. Thank you for your input Pony Killer. One thing though, your .500 numbers went up with your intake on? Is this normal? My flow was much lower with the intake on than with the intake off. Thank you again

 

hooking the intake up was proving to be a pain in the *** becaus of the vortec head design... the way it bolts up specifically, we got one good test on it and decided to call it a day.

The machinist told me later he tested a set of vortec heads with the performer rpm intake and the results were the same about a 7-8 cfm increase at peak with those heads and that manifold, the encouraging part was it never "robbed" cfm from the heads.

The fella does a lot of work on the heads and has done an aweful lot justlike mine, so i take his word on it. Part of the reason he likes that intake is because it never makes *his* heads look bad. wheras he has a real aversion to the wieand intakes, and some others.

 

I wonder if it has anything to do with me being injected why I lost so much flow from my heads.

 

The heads alone were probabily tested without a radius plate
on the inlet face. worth about 20cfm.

Putty radius will do in a pinch.