How to identify GT40x heads??

webshot · Mar 16, 2012

Hey folks I have a 94 cobra, and it has been told to me that I have gt40x (SVO) heads. How would I go about verifying this? Is there a casting number or something on them? Also would I have to remove the heads to find the identification marks/number?

revhead347 · Mar 16, 2012

Are they aluminum?

Kurt

VibrantRedGT · Mar 16, 2012

Right on the front of the head it says SVO in big letters. Like Kurt said the X series are aluminum so the color of the heads will be lighter than cast iron. Look where the accessory brackets bolt to the heads, if they are X you'll see the SVO stamp. All the other stamps will not be visible without taking the valve covers off.

revhead347 · Mar 16, 2012

If you are not good at distinguishing colors, or the heads are painted or dirty, just do the magnet test to see if they are aluminum.

Kurt

webshot · Mar 17, 2012

Thanks guys, revhead347 the magnet test you mention. Are you saying to place magnet on an exposed area of the head and the magnet should stick? The heads are a really light in color, but I tried to stick a magnet on a small exposed area and the magnet did not stick. The heads are on the car with everything bolted up so I could not see the markings you spoke of VibrantRed.

revhead347 · Mar 17, 2012

webshot said:
Thanks guys, revhead347 the magnet test you mention. Are you saying to place magnet on an exposed area of the head and the magnet should stick? The heads are a really light in color, but I tried to stick a magnet on a small exposed area and the magnet did not stick. The heads are on the car with everything bolted up so I could not see the markings you spoke of VibrantRed.

That's a good start, that means they are aluminum. Now you can start looking for markings. See if you can get a mirror in behind the head. Like someone else said, they should say SVO in big letters on the back.

Kurt

VibrantRedGT · Mar 17, 2012

webshot
Should say SVO on both the front and back of the heads. This was the best picture I could find. I never did take any close up pics of these heads. I circled where it will say SVO. It does sound like they are GT40X heads though.

webshot · Mar 18, 2012

Thanks gents.... I am gonna try again in the AM to positively identify these. I have a battery of other questions to ask after this, but I want to positively identify my key parts before hitting you guys up (so I can give precise details).

Thanks folks. Will report back.

revhead347 · Mar 18, 2012

If they are aluminum, you can pretty safely assume that it has the GT-40x heads like you were told. That's something most people wouldn't lie about. All those entry level aluminum heads cost about the same, and the GT-40x is arguably the lowest performer of those heads. Not by much, but enough that there is no incentive to lie about it.

Kurt

webshot · Mar 18, 2012

thanks Kurt. I am having some engine troubles and it is being attributed to my heads/cam combo so I am just doing a little research.

revhead347 · Mar 18, 2012

Sounds good. Unfortunately it's hard to tell what kind of cam there is without taking it out.

Kurt

webshot · Mar 18, 2012

Oh I know the cam, it is a TFS stage 1.

advent · Mar 19, 2012

The newers GT40X have a "Ford Racing" logo stamped instead "SVO" ...

There are the GT40Y too . I don't know if there are visually differences between X and Y heads .
Just know that Y are 160cc int./53cc exh. and X are 178cc int/62cc exh.

revhead347 · Mar 20, 2012

I forgot all about the damn Y heads. Those go way back.

Kurt

VibrantRedGT · Mar 21, 2012

revhead347 said:
I forgot all about the damn Y heads. Those go way back.

Kurt

Yeah me too, just brought me back. I believe they were Y02 heads.

FastDriver · Mar 21, 2012

There should be casting numbers where the rockers go. Tell us what the numbers are. I think "X303" and "X305" heads differentiate between stud and pedestal mount heads and/or combustion chamber size.

advent · Mar 21, 2012

FastDriver said:
There should be casting numbers where the rockers go. Tell us what the numbers are. I think "X303" and "X305" heads differentiate between stud and pedestal mount heads and/or combustion chamber size.

Yes , X-303 are 64cc chamber and X-305 are 58cc chamber . Both are pedestal mouting rockers and have 1.94" int./1.54" exh. valves . Here are Ford Racing flows numbers:

VibrantRedGT · Mar 21, 2012

I bought my GT40X heads bare and upgraded the springs to Steeda Hi-Rev's and valves to Ferrea's. I should have had all the ports cleaned up. Lots of cast flash. When I upgraded to the 347 I went with AFR 185's so they were sold. They sat in Rogers (Green94 5.0) garage for like 7 years. They got dusted off a few months ago. They are now on his 1992 GT with Vortech V3i and my old Edelbrock RPM Polished Intake / 70MM throttle body. So 12 years later they are still going strong.

Here they are.

FastDriver · Mar 21, 2012

Good stuff, Advent. Thanks! I think that should pretty much hit the nail on the head as far as what the OP was looking for.

webshot · Mar 21, 2012

Good stuff gentlemen!! I am soaking up all the knowledge being dropped!!

How to identify GT40x heads??

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