Thread: CNC Heads--Opinions?

03 GTP 132k, dd

I've got my car running strong as near stock. Plan is to enjoy it thru the winter, then in the spring start w/ the go-faster fun stuff, beginning w/ headers. I've ruled out a cam, but eventually plan to do MPS & roller rockers. I'm toying with the idea of getting CNC heads, and have a few noob ?s

1st, for our cars, can the heads be swapped w/ engine in car?

2nd, what kind of gains might be expected by bolting on CNC heads w/ a modest build (stock bottom end, rods, pistons, etc)?

3rd, opinions on comparings CNC heads vs. I/C, for the $?

Thanks!

1) yes, very easily.

2) heads without installing a cam isnt going to be utilizing the extra headroom you just gained. get a cam.

3) if youre not going to cam the car, the intercooler would do you better.

Swapping heads with the engine in the car sucks. It can be done, but it's not much fun. Cleaning the old gaskets off the block is what sucks.

You're probably looking at about a 10whp gain on a stock car over one with CNC heads. Get and IC instead.

Thanks for the input guys. cnc heads are not cheap....

Please confirm stock L67

cam lobe = .25
head clearance = .5

You're going to have to be more specific. I don't know what you're asking.

I'm trying to get a better general understanding before digging around in there.

What is stock cam lobe lift? .258"

With a rocker lift ratio of 1.6.

When shopping for heads, I see ads w/, machined to .600" clearance. For stock L67, what is clearance?


Also, shopping for yt 1.9 alum rr, the only place I found is intense, and they recommend 90# springs. I've read in many other places 105# are better. Anyone want to chime in?

the .6" clearance will allow you to run more lift (rockers or cam, depends). the part you're really looking for is the heads to be ported. the head room is cheap and extremely easy. the porting (the right way) is the expensive part.

Originally Posted by Mr D

I'm trying to get a better general understanding before digging around in there.

What is stock cam lobe lift? .258"

With a rocker lift ratio of 1.6.

When shopping for heads, I see ads w/, machined to .600" clearance. For stock L67, what is clearance?


Also, shopping for yt 1.9 alum rr, the only place I found is intense, and they recommend 90# springs. I've read in many other places 105# are better. Anyone want to chime in?

There is a cam spec'sthread on here, I think stickied in this section. That will give you all the answers you need.

Anytime you are exceeding .515" lift, you either need machined retainers, viton valve seals, or clearanced valve guides. Just depends on how much lift you have.

I would go with 105# springs, as long as it's not a Comp Cam Spring.

Thanks again guys,

I was looking for the .515" lift, read sticky but didn't see it in there.

if your not camming the car dont even waste your money on heads. just get yours ported instead.

put bigger valves in your heads and blend the throat into the port, wont cost much more the a typical valve job