Need some advice on upgrading GT-40-X303 heads

93gtmustang · Sep 1, 2024

I've been racing this motor since 2007. I was thinking maybe the valve springs should be checked or upgraded to stronger ones. Also thinking of putting in roller rockers too. What ratio?
I read somewhere you could pick up 10-15 rwhp? The heads are GT-40 M-6049-X303 heads on top of stock bottom end 302 9.0:1 compression B-303 cam. Ford Racing Crate engine. M-6007-XE3M
I'd like to try and do this myself. Any advice, links to parts, and how to instructions would be greatly appreciated.
Happy Labor Day!
Thanks!

qikgts · Sep 1, 2024

Installing roller rockers is an expensive proposition these days when buying new. For a decent set you'll be looking at like $400+ bucks. If you can find a set of drop in springs then you could do it yourself on the car w/o even pulling the heads. However, since the heads have been in service for more than 15 years, I'd pull the heads and have them gone through at a competent machine shop and also have them replace the springs. Good time to get a fresh valve job too. Bet that alone would make it feel faster and might cost less than new roller rockers alone.

93gtmustang · Sep 2, 2024

qikgts said:
Installing roller rockers is an expensive proposition these days when buying new. For a decent set you'll be looking at like $400+ bucks. If you can find a set of drop in springs then you could do it yourself on the car w/o even pulling the heads. However, since the heads have been in service for more than 15 years, I'd pull the heads and have them gone through at a competent machine shop and also have them replace the springs. Good time to get a fresh valve job too. Bet that alone would make it feel faster and might cost less than new roller rockers alone.

Thanks for the information. Yes, the heads have been in service for 15 years, but there is not many miles on them. It saw some street time. It's now an all out drag car on a trailer since 2020. Odometer doesn't work. There's probably only 30,000 miles on the engine.

Noobz347 · Sep 2, 2024

93gtmustang said:
I've been racing this motor since 2007. I was thinking maybe the valve springs should be checked or upgraded to stronger ones. Also thinking of putting in roller rockers too. What ratio?
I read somewhere you could pick up 10-15 rwhp? The heads are GT-40 M-6049-X303 heads on top of stock bottom end 302 9.0:1 compression B-303 cam. Ford Racing Crate engine. M-6007-XE3M
I'd like to try and do this myself. Any advice, links to parts, and how to instructions would be greatly appreciated.
Happy Labor Day!
Thanks!

Man... There is just nothing in this post that suggests stronger springs are required? Are you planning to boost it or change the cam or something? Do you experience valve float?

You only gain "10-15 rwhp" from springs if your current springs are not up to the rest of the combo. A B-Cam isn't really very extreme.

I whole heartedly recommend the Roller Rockers. Anything you can do to reduce the friction in the valve train or lighten the valve train, is a [good] thing.

If this is race only, consider moving over to solid lifters, You can even use your current cam. Find a set of lightweight roller rockers in maybe a 1.6 lift. It will amplify a little bit over your current cam. There are actually much better folks on this site to recommend a specific ratio better than me.

The spring upgrade for an otherwise N/A engine with a fairly mild cam... Hmmmm... I just don't think that is going to get you anywhere. If you're talking boost... different scenario.

AeroCoupe · Sep 2, 2024

So a drag motor will spend more time on the upper end of the rpms than a street motor and they are hard on valve springs. Take the heads off and take them to a reputable machine shop in your area and have them inspect them. They can check the springs for proper open and closed spring rates, correct install height, bind, valve guides, valve seals, can lap the valves to see how they are sealing, and then check the flatness of the heads.

You can also get a price to covert them over to stud mount roller rockers if you think that is the way you want to go or just get some pedestal mount ones but they have their limitations when it comes to lift. Someone else can speak on that as I do not run them just heard that there is a limit geometry wise.

I just call this good maintenance and at this point all you are paying for is for them to tell you what needs to be done and provide a price. If everything looks good then it may be as simple as putting a set of new springs on and bolting them back up.

93gtmustang · Sep 3, 2024

Noobz347 said:
Man... There is just nothing in this post that suggests stronger springs are required? Are you planning to boost it or change the cam or something? Do you experience valve float?

You only gain "10-15 rwhp" from springs if your current springs are not up to the rest of the combo. A B-Cam isn't really very extreme.

I whole heartedly recommend the Roller Rockers. Anything you can do to reduce the friction in the valve train or lighten the valve train, is a [good] thing.

If this is race only, consider moving over to solid lifters, You can even use your current cam. Find a set of lightweight roller rockers in maybe a 1.6 lift. It will amplify a little bit over your current cam. There are actually much better folks on this site to recommend a specific ratio better than me.

The spring upgrade for an otherwise N/A engine with a fairly mild cam... Hmmmm... I just don't think that is going to get you anywhere. If you're talking boost... different scenario.

Thanks !
So, no need for valve springs right? Now that I think of it, I contacted Alex Parts and I think they said the current valve springs are fine for the B cam. Heavier ones aren't required.
Not planning on boosting it. I would really like to get the Trick Flow 11R top end kit. But at this point I don't feel like dropping $3500.00.
No valve float. It peaks out at 6000rpms most every run. Shift light is set to 5700 rpms. It come on a little before the finish line. Not really super high rpms.
What would the solid lifters do?
It is a race only car.
I like the roller rockers idea. Just need to know which ones and how to do install them.
On a good note, I had a leak down test done a couple years ago. My mechanic said ""The engine is TIGHT. Input 100 psi during leak down test. All cylinders held 99-97.5 psi. 1 to 2.5% leak down. Super healthy.
Knowing that, I should just run it the way it is and be happy about it.
Thanks!

93gtmustang · Sep 3, 2024

AeroCoupe said:
So a drag motor will spend more time on the upper end of the rpms than a street motor and they are hard on valve springs. Take the heads off and take them to a reputable machine shop in your area and have them inspect them. They can check the springs for proper open and closed spring rates, correct install height, bind, valve guides, valve seals, can lap the valves to see how they are sealing, and then check the flatness of the heads.

You can also get a price to covert them over to stud mount roller rockers if you think that is the way you want to go or just get some pedestal mount ones but they have their limitations when it comes to lift. Someone else can speak on that as I do not run them just heard that there is a limit geometry wise.

I just call this good maintenance and at this point all you are paying for is for them to tell you what needs to be done and provide a price. If everything looks good then it may be as simple as putting a set of new springs on and bolting them back up.

Thanks for the great information!
If those heads had to come off, I would sell them.
Then I would be putting the Trick Flow 11r top end kit on without a doubt lol!
Thanks!

AeroCoupe · Sep 3, 2024

I am just used to putting new valve springs on every year with my buddy's car. He said if he runs the previous year's springs the car falls off within a few weeks in the new season. Granted he is running a high lift cam and shifting at 7800 rpm but you have had them in there for 15 years. My guess would be they are no longer providing the open and close pressures they used to.

Decent video on how to change them in the car:

2000xp8 · Sep 3, 2024

Head work is one of those things that it really just doesn't pay to mess with yourself.
Valve jobs aren't really expensive and they insure the heads are reliable and you get the most out of them.

Find a local machine shop, take them there for a valve job and they really should handle all of it all it.
Even if you were to look at TEA's website for a valve job, none of the prices are all that nuts.
And considering Gt40x heads are flawed in brand new condition (almost all heads are), it's well worth it.

93gtmustang · Sep 5, 2024

(Head work is one of those things that it really just doesn't pay to mess with yourself.)
That gives me my answer right there.
I'm not screwing with the heads.
I have no clue how to do any head work. I just talked to my mechanic, and he suggested a yearly leak down compression test.
If and when they start to fail, I'm looking to upgrade to trick flow. But, If I can't swing it financially, I'll look into sending them out to TEA.
Is that Total Engine Airflow? Looks like a great place and fair prices.
Thanks for all the help everyone!

Noobz347 · Sep 5, 2024

If you wanna get [really] crazy

The next time you pull the heads (for whatever reason), find a place to take your entire inlet tract and heads to get them extrude honed:

Extrude Honing Frequently Asked Questions — Automotive Edition - Extrude Hone AFM

Extrude Hone AFM has many clients in the automotive industry. If you’re considering sending one or more components to Extrude Hone AFM, here are the answers to our most frequently asked questions for the automotive industry.

www.extrudehoneafm.com

Noobz347 · Sep 5, 2024

93gtmustang said:
What would the solid lifters do?

They increase HP by making timing events [precise] whereas hydraulic lifters inherently have a lot of slop. It also reduces the amount of mass in the valve train [decreasing] the demand on valve spring pressure.

The tradeoff is that solid lifters require more frequent adjustment.

2000xp8 · Sep 5, 2024

I had extrude honed twisted wedge heads. Even getting the heads bare brand new and technically for free (i had to pay the extrude hone bill for someone that abandoned them at my buddies shop, at the time it was $750), they still were pretty expensive, by the time i bought all the hardware and paid for the valve job. Would i pay to have it done? Not totally sure. The theory at the time was that straightens and smooths out the path without opening it up too far and killing velocity.
Does it work? I'm not totally sure.
What they will do is work well on a 302 and a 347.

If i had a 302 and X heads, i'd have them valve jobbed and all the work that goes along with it (like springs, bowl work) and run them. They will be close to as good as box stock 170 Tw's.
To be clear, i also owned X and Y heads.
Now if you get into a 347, it could be an issue. There are good CNC programs for TW's, not many i've seen for X's.

I'm also all for port matching intakes to heads while they are at the machine shop.

BTW, back in the day they used to extrude hone cobra intakes before there were 50 better ones out there. It would hang with the best out there on smaller displacement engines, but i don't think it can hold a candle to an RPMII.

93gtmustang · Sep 5, 2024

Noobz347 said:
If you wanna get [really] crazy

The next time you pull the heads (for whatever reason), find a place to take your entire inlet tract and heads to get them extrude honed:

Extrude Honing Frequently Asked Questions — Automotive Edition - Extrude Hone AFM

Extrude Hone AFM has many clients in the automotive industry. If you’re considering sending one or more components to Extrude Hone AFM, here are the answers to our most frequently asked questions for the automotive industry.

www.extrudehoneafm.com

For me, that's way too much!
Very interesting though!

93gtmustang · Sep 5, 2024

Noobz347 said:
They increase HP by making timing events [precise] whereas hydraulic lifters inherently have a lot of slop. It also reduces the amount of mass in the valve train [decreasing] the demand on valve spring pressure.

The tradeoff is that solid lifters require more frequent adjustment.

Oh boy I don't need frequent adjustment.
I'm trying to stay as simple as possible!
Looks like something more used in a race motor that gets freshened every 60 runs.

93gtmustang · Sep 5, 2024

These are the heads I was looking at.
Well actually it's a complete kit.
I think it's fairly priced.
Good horsepower gains.
But I'm not doing it this year.

Noobz347 · Sep 5, 2024

93gtmustang said:
I've been racing this motor since 2007.

93gtmustang said:
Looks like something more used in a race motor

93gtmustang said:
that gets freshened every 60 runs.

No

Need some advice on upgrading GT-40-X303 heads

93gtmustang

qikgts

Active Member

93gtmustang

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

AeroCoupe

lube between the nut and the face. I know my lubes

93gtmustang

93gtmustang

AeroCoupe

lube between the nut and the face. I know my lubes

2000xp8

93gtmustang

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

Extrude Honing Frequently Asked Questions — Automotive Edition - Extrude Hone AFM

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

2000xp8

93gtmustang

Extrude Honing Frequently Asked Questions — Automotive Edition - Extrude Hone AFM

Extrude Honing Frequently Asked Questions — Automotive Edition - Extrude Hone AFM

93gtmustang

93gtmustang

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

Similar threads

Need some advice on upgrading GT-40-X303 heads

Active Member

Stangnet Facilities Maint Tech... Er... Janitor

lube between the nut and the face. I know my lubes

lube between the nut and the face. I know my lubes

Stangnet Facilities Maint Tech... Er... Janitor

Stangnet Facilities Maint Tech... Er... Janitor

Stangnet Facilities Maint Tech... Er... Janitor

Similar threads

Privacy & Transparency

Privacy & Transparency