What heads are we talkng about. What you are asking can almost exceed the cost of new heads from GM Performance parts that already have these features?

Vince

 

Wow, "302"! I've always liked that engine, but I've never been around one. One day I might make one of those though. That short stroke with a 4" bore has great power potential.

You asked what heads, but I actually included that in my post. GM only put one kind of head on their 1998 chevy pickups. Anyway, thanks for looking out for me, as far as directing me to go to GMPP for heads. I already have one set of their heads on my truck as they came with my crate engine. I just want to know how much of a tab I'm looking at. Yes, it may very well exceed the cost of a new set of *STOCK* vortec heads, but that's okay...

As far as the GMPP heads,

they don't come with screw-in studs
they don't come with big valves
they come with a combustion chamber size (~62cc), that I don't want

But, yes they can handle more lift, but they would have the wrong springs for my application. So, it's no real savings. These vortecs aren't that great of a bargain once you figure all of this in, but they're what my old truck has on it, and I'm willing to work with them. And "work" is what I have in store for these heads.

Again, this is VORTEC heads.

Please reply if you know what the going machine shop rates are for these services.

Ben T.

 

You have the Vortec heads.

From what I hear, you're not going to see a lot of gains from going to 2.02 valves.

Edelbrock offers the E-Tec aluminum version of the Vortec heads with 170 cc intake runners (1.94 valves) and also the 200 cc version that has 2.02 valves. This combination will be more matched than the 170cc with 2.02, but very $$$

Why not try bowl blending your current heads for a little more flow? You would probably pick up about 10 to 15 HP if you don't overdo it, and bowl blending is very easy to do

 

I actually just got in from bowl blending some heads right now. I think I still have some metal dust on me. Yes, it is pretty easy to do.

I have some flow numbers that would go against what you said. I had been hearing the same things that you did, but I have been learning the L31's can flow a lot more than how they come factory. I infact have some pictures of vortecs that flowed 280cfm/220cfm. They're pretty sweet looking too. Those heads had big valves. I also have some numbers from David Vizzard of some 2.055 and 1.60" vortecs he did. He managed to get great improvements with his work.

I do not want to go with ETEC's. I want to go with the vortec heads. I want to try the small intake runners for velocity and combine that with big valves for good flow. We'll see what happens.

Thanks anyway though. I think I'll call a machine shop tomorrow.... :-(

Ben T.

 

Reddwarf,

Can't believe I forgot. You're right on one thing for sure. If you don't unshroud the bigger valves, you'll gain nothing. That's why just the larger valves and not porting work gives you no better flow.

Ben T.

 

Vizzard certainly knows his stuff.

Did he enlarge the runners at all?

And what valve lift were those flow numbers at?

Don't forget to look at the .100 to .400 lift figures since that's all you're going to get out of a street-friendly cam. What cam are you planning on running?

Your project is starting to intrigue me....

 

I'm wondering what would be a fair price for the following services to be done. This is a V8 chevy engine, of course.


1*Heads milled, and the manifold side resurfaced for use with a conventional unmachined intake.

2*Cutting the heads for 2.02 and 1.60 valves as opposed to the 1.94 and 1.50" valves they have now.

3*Enlarging the spring pocket to use a 1.437" spring, as opposed to the stock 1.25" pocket.

4*Removing, and then, drilling and tapping the heads for screw-in rocker arm studs.

Okay, if they are any machine shop owners/patrons out there that can give me some insight into these costs please advise me. I don't want to go and get ripped off somewhere. These are heads off of a 1998 chevy pickup truck.

Thanks if you can help me out.
Ben T.

Hey Ben

http://64.246.6.99/~admin6/forum/showthread.php?s=&threadid=39997&perpage=15&pagenumber=1

Ken

 

Mr. Dwarf,

let's see if I can get your numbers...
The intake runners were enlarged 7cc for a total of 177cc's.
Below is Mr. Vizzard's intake cfm's
.100 70
.200 141
.300 202
.400 240
.500 250+ (peaked amount from .5-.6")
Exhaust cfm's
.100 70
.200 127
.300 165
.400 182
.500 195
.600" 208

Cam choice is a comp cam hydrulic roller. It's got 276/284 advertised duration from 224/230degree of valve lift at .050". This cam is on a 112degree LCA, so it'll still make great midrange. Lift is .503/.510" with 1.5:1 rocker arms. This is the cam I think I'd like to go with, but after the heads are finished I'll then make my final decisions. Once I get some numbers, I'll decide on how much lift I want to run.

Compression will be around 10:1 (after the heads are milled). It'll flow through a mildly cleaned up GM dual plane. It came on my 330 deluxe crate motor. It is also is the same dual plane manifold used on the zz430. My modified heads, hopefully, will make power as well as the fast burns, but possibly more torque/midrange. So, I want to do just a little head/cam swap and pick up another 100 horsepower.

This is the project. The "old" truck is a 1988 swb sc c1500. A th400 would takes the abuse at it sets tonight.

So, the questions about the heads are because I'm learning to port cylinder heads. Once, I get it down I'll apply my new found skill/knowlege to a pair of L31's for my truck.

Ben T.