HELP....GT40 P heads questions....HELP!!!

rideapony · Aug 25, 2006

Hi all, I'm trying to find answers about GT40 P heads before I buy them.

a) I would like to run 7/16" top and bottom ARP studs for RR's. I heard that the pedestals need to be milled down to a certain height and of course drill and tap for the 7/16" studs as the pedestals are threaded for 5/16".

Or can I just use the 5/16" bottom - 7/16" top studs?

Did anyone did this conversion and if so how hard it is to be done? Also if anyone has any links that can help with this project please post them. I haven't been able to find anything on the net.

b) I read and heard a lot about some of the inconveniences involved when using these heads besides the use of the "P" headers. The things that really concern me are the issues ragarding replacing the plugs and the damage to the ignition wires because they are too close to the headers. So what type of wires boot angle to use and how hard is to replace the plugs? Also if this combo (drilled GT40 P heads, GT40 P headers, and Trick Flow Stage 1 cam) will pass the smog check in California.

I really need answers to these question or maybe some other ideas before I buy those heads.

thanks guys, Nick

TheUser · Aug 25, 2006

Is there a reason you have to use studs for the rockers? I am not sure if studs are stronger, but if you are using the GT40 P heads, I really doubt you need a whole lot of increased strength. Again, I'm not even sure if stud mounted rockers are stronger.

Changing spark plugs w/ my FMS headers on looks like a pain - I don't remember changing them w/ the headers on, but it might be impossible w/ my headers. I'm not 100% positive if my headers are P headers, but they're made by FMS and came w/ the car - I assume they are P headers.

I've read you can use one brand of long tubes w/ the P's, which might give some more room, but will probably cause clearance issues below the car (dragging on speed bumps, etc) and will require a shorty mid-pipe to accomodate the long tube headers.

As long as you have the CARB numbers for all of the parts and pass the visual and sniffer tests, you should pass the CA emissions tests, I assume, although I have no personal experience w/ that. They most likely won't remove your valve covers to see your rockers, so that shouldn't matter.

Tonys96Cobra · Aug 25, 2006

I can vouch for the FMS headers working well, no real issues with plug changes. As far as emmisions, they are not drilled for the AIR tube in the back of the head, so if you want to keep that, you wil have to pay to have them drilled and tapped.

rideapony · Aug 26, 2006

I heard that the studs are better all the war around for once you can adjust your rockers easier than pedestal because you don't have to use shims which is a pain. I'm sure those 7/16" top and bottom ARP studs are really strong.

By the way do I have to use hardened pushrods and guides when using stud mount rockers?

I know the heads are not drilled originally but you can get them drilled (from some companies) and ready to bolt onto a mustang. As far as changing the plugs it might be a bit tricky but there has to be a way to do it right?

I think I'm going to take my chances and piece this set up together but I really need advices from people here in California that have or had this set up if will pass smog check or not.

Did anyone experienced burned ignition wires/boots by using those headers?

Thank you guys, Nick

rideapony · Aug 30, 2006

I was wondering if the RR I have will work on the GT40 P heads. The thing is that the RR I have (New I ran them only a couple of weeks) are 1.7 pedestal. I thought I could use them with studs too. I read on crane cams webpage and I cut+paste this:

Part No. 44746-16 (a)
(Ford Cobra 5.0 H.O.) 1.70, 5/16? dia., bolt

Ford V-8 1962-2000, 221-255-260-289-302-5.0L H.O. and 351W
Stud-mount, requires machining heads and installing screw-in studs and pushrod guideplates.

This is directly from the Crane Cams online catalog. Did anyone run those RR on studs instead of pedestal?

Thank you all, Nick

TheUser · Aug 30, 2006

I forgot about the Air tubes that go to the back of the heads...the heads probably wouldn't be worth it if you have to purchase them and have them machined for those holes, plus cleaned up and all that.

I use the wires w/ the 90 degree boots and have no problems.

I might have different headers than Tony above, but my spark plugs look like they'd be nearly impossible to get out on some of the cyclinders - at least without totally scratching the hell out of the headers, and I really don't think it's possible anyway. I recently painted mine and they fried, so I might be buying new ones, who knows.

Good Luck

rideapony · Aug 31, 2006

thanks for the info. Well I'm not too worry about drilling the heads here is a site where they have those heads with bigger valves and springs better than stock so they should be good. www.tristatecylinderhead.com/catalog/products. I'm sure they can drill them for some 40 bucks.

Thank you for the tip on which wire boots angle to use so they don't get burned. The biggest worry now is that I have to remove the headers to change the plugs that really sucks!!!!.

That makes me wonder if I really want to use those heads.

Please keep sending your experiences with those heads or new suggestions.

Thank you all, Nick

TheUser · Aug 31, 2006

Nick,

I forgot to mention that I also use wire dividers to sort of hold the wires up and away from the headers; 90-degree boot or not, if the boot gets turned, the wire could possibly fall into the headers. I would get some wire dividers if I were you.

Again, you may check out the different types of headers for the P heads. I guess the issue I had w/ mine is that you can't turn the rachet very far because of how close the pipes are, but I guess you really don't need to; really, I suppose you just need enough room to "break" the plugs loose allowing you to possibly turn them out by hand, so they may not be a problem after all. If for some reason they do require a socket and ratchet the whole way out, you'll have problems.

Sorry, I've only changed plugs w/ everything bolted to 5.0 once; other than that, I've had the headers off for some reason and just went ahead and changed them at that time.

rd · Aug 31, 2006

I have used the Comp Cams conversion studs for pedestal mount heads, 5/16 on the bottom and 3/8 on top and they work fine.

You may or may not have to mill the pedestal or stud boss down. Mock it up with your rockers. If the rockers have enough travel and are hitting the valve tips on the center youre good. I have done both, and made it work. The original advise on milling the stud bosses came from 70's heads, when there were some heads with shorter valves, springs, etc. I think most 79 and up 5.0 heads with current stock valve and spring lengths are ok w/o that mod.

SMOKEDYA · Aug 31, 2006

I have these heads with mac L/T's and have no issue's with plug replacement or wire issues. I dont go threw emisions so i dont know about that? I've also noticed with the crane (cobra) 1.7's or maybe with these heads alone i hear rocker tapping, i've set and rechecked the tourque and there right on! Here is a pic of mine on the stand i used the ford blue 9MM wires from summit! The L/T's do hang low but i mostly hit the mid pipe on speed bumps and other stuff but not bad as long as you remember your notdriving a 4x4! My car is even lowered!

Heres a pic from under the car :

peace

john

rideapony · Aug 31, 2006

I have a lot of wire separators from MSD and maybe I can put some boot shields just in case.

Hey "SMOKEDYA" those are nice pics, those give me a better idea about the access to the plugs with the headers on. It looks really tight but shouldn't be that hard. Unfortunatelly mine is a daily driver car and those headers won't pass smog check (I think) but the clearance should given with the shorty headers shoul be close to the long ones (I'm assuming)

"rd" are we talking about the same rocker arms Energize 1.7 p/n 44746-16? I know they are mount using a 5/16 retainning bolt but you say you mounted them on 3/8" studs, I have to double check to see if a 3/8" bolt thru the rocker arm hole.

Thank you all guys, Nick

HELP....GT40 P heads questions....HELP!!!

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