GT40 head's and installing heavier spring's.

289 - 351 cid Small Block Performance

GT40 head's and installing heavier spring's.

Postby Lip Ripper » Mon Jan 16, 2017 9:49 am

Well, I've been all around this 93 5.0 with the 93 Cobra head's. A couple thing's I'd like to share are #1, The F303 cam installed in this setup causes the intake valve's to tag the piston's. There are no eyebrow's in the factory piston's. #2; The valve retainer's and valve spring's have a staggered height. The exhaust valves have a rotator and shorter spring's. Comp Cam's and others' sell double spring's and retainer's as a direct fit but they do not. Valve lock height on the exhaust valve is lower than the intake. I have finally figured out with some guidance and a lot of researching that in order to use the aftermarket spring's and retainer's you must replace the exhaust valves. I found that the early 351 Windsor 1.54 exhaust valve's have the same lock height as the intake valve on the GT40 head's. Part number V1893, V1237, E-1762 are a few of the aftermarket number's for the 351 valve that is needed.

For the valve clearance issue I've ordered a chebby 1.94 intake valve. I will glue 80 grit sandpaper to that valve and carefully cut the eyebrow's using the cylinder head as a jig. This technique came from a trusted engine builder that I've known for a long time. According to John, the intake need's about .100 relief on a manual tranny car to assure the valve's don't play tag with the piston's. I'll probably do a video on this or at least take photo's to share.
66 Cyclone GT; 245/60R15's on 15x8's and 215/70R15's on 15x7 Magnum's.
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Re: GT40 head's and installing heavier spring's.

Postby Rocket989 » Mon Jan 16, 2017 10:56 am

Stacey - if the pistons don't have valve reliefs, they were replaced (odd though - not many totally smooth, flat-top replacement pistons!) or the shortblock might be from an '86 'Stang (or even something else like a Crown Vic). What's the casting number on the block? Also, is there a partial VIN behind the rear China wall?

For springs, Trick Flow and Alex's Parts make drop-in replacement kits (springs, retainers, locks, and seals) for about $150 bucks. As you said, if you go aftermarket valves, stock diameter or larger options open up. The key with the stock stuff are the special retainers for different stem heights.
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Re: GT40 head's and installing heavier spring's.

Postby Lip Ripper » Mon Jan 16, 2017 11:37 am

According to my engine building friend, Ford did use these piston's from the factory. I sent him photo's. They have no valve relief an only a very slight dish in the middle. He called them the second worst factory piston as far as valve clearance. I don't know but I have no reason to doubt him. He's been building Ford block's since the 70's.

I'll look at casting number's to share. I know the crank had F3 and so do the head's so they're the 93 casting's.
66 Cyclone GT; 245/60R15's on 15x8's and 215/70R15's on 15x7 Magnum's.
There's nothing like the sound of a pushrod V8 singing at the top of her lung's.
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Re: GT40 head's and installing heavier spring's.

Postby Rocket989 » Mon Jan 16, 2017 3:42 pm

Huh - all the 5.0 'Stang motors except '86 had valve reliefs. About the only good news if it is an '86 shortblock...the pistons are forged! :D I'm not familiar enough with some of the other non-HO 5.0's but some of them coulda had true flat tops. Flycutting them yourself will work just fine! Or cough-up $$ for any of the TFS Twisted Wedge heads - with the shallower (varies) valve angle, they typically have plenty of clearance up to some pretty decent size cams.
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Re: GT40 head's and installing heavier spring's.

Postby Rocket989 » Mon Jan 16, 2017 9:31 pm

They've got others for different lift ranges, but here's .550 lift kit:

https://www.alexsparts.com/sb-ford-gt40 ... sk7h48-13/
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Re: GT40 head's and installing heavier spring's.

Postby Lip Ripper » Tue Jan 17, 2017 5:06 am

Dang, that would've been perfect and a lot less work. I think I'll see about returning the valves then selling my other spring's and retainer's at a loss and use the above instead; thanks for the insight.

SW
66 Cyclone GT; 245/60R15's on 15x8's and 215/70R15's on 15x7 Magnum's.
There's nothing like the sound of a pushrod V8 singing at the top of her lung's.
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Re: GT40 head's and installing heavier spring's.

Postby Rocket989 » Tue Jan 17, 2017 9:50 am

Sure man!! Hopefully you can recoup most of the $$!! :D
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Re: GT40 head's and installing heavier spring's.

Postby Lip Ripper » Tue Jan 17, 2017 11:07 am

Next problem is the valve stem seal. These have to have the steel jacket that slide's over the guide. My guide measures .564. The seal's I got won't go over the guide. I called Felpro tech and they agreed that they're too small for my head. Some seals require machining down the guide. Are you kidding me?
Last edited by Lip Ripper on Tue Jan 17, 2017 4:31 pm, edited 1 time in total.
66 Cyclone GT; 245/60R15's on 15x8's and 215/70R15's on 15x7 Magnum's.
There's nothing like the sound of a pushrod V8 singing at the top of her lung's.
Lip Ripper
 
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Joined: Wed Jun 06, 2012 4:47 am
Location: Lake Placid, Florida

Re: GT40 head's and installing heavier spring's.

Postby Comechero65 » Tue Jan 17, 2017 2:22 pm

Someone sells a tool for cutting the guides so the better seals will fit correctly. Have no idea who.
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Re: GT40 head's and installing heavier spring's.

Postby Rocket989 » Tue Jan 17, 2017 4:26 pm

Alex's Parts also sells a Viton seal that'll stick right over the boss (should be an add-on to the spring kit). I bought the same ones.

Oh yeah...definitely get the shim pack (maybe call & see if they'll discount the bigger pack that includes the .060 shims). I wouldn't go more than that, but it's better than stacking 'em. IIRC I used .045 on the exhaust and .060 on the intake valves to get the correct installed height.

BTW - You get a chance to look @ the block casting #'s??
Last edited by Rocket989 on Tue Jan 17, 2017 4:32 pm, edited 2 times in total.
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Re: GT40 head's and installing heavier spring's.

Postby Lip Ripper » Tue Jan 17, 2017 4:29 pm

I'm not going to buy a cutting tool to work on a pair of head's that I will likely never own again. I have contacted Alex's part's and hopefully they'll have the right seal's. This coupled with the eyebrow-less piston's are making thing's difficult. Thank goodness I pulled this thing apart and didn't trust the previous owner's effort's.

Thanks for all the input guy's.

SW
66 Cyclone GT; 245/60R15's on 15x8's and 215/70R15's on 15x7 Magnum's.
There's nothing like the sound of a pushrod V8 singing at the top of her lung's.
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Location: Lake Placid, Florida

Re: GT40 head's and installing heavier spring's.

Postby popscomet » Tue Jan 17, 2017 5:47 pm

I bought a new 1977 302 ford bronco,after 20,000 miles ,I changed out the heads ,intake,carb and timing chain and gears,and added dual exh........it had true blue flat top pistons !!.....I went with everything from a 1965 289..pop
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Re: GT40 head's and installing heavier spring's.

Postby popscomet » Tue Jan 17, 2017 5:49 pm

popscomet wrote:I bought a new 1977 302 ford bronco,after 20,000 miles ,I changed out the heads ,intake,carb and timing chain and gears,and added dual exh........it had true blue flat top pistons !!.....I went with everything from a 1965 289..pop

forgot to mention,,,used a bone stock 289 camshaft also........pop
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Re: GT40 head's and installing heavier spring's.

Postby Lip Ripper » Wed Jan 18, 2017 7:20 am

This thing has me aggravated. The Cobra cam that came factory was F3ZE-6250-CA and had an advertised 479 lift, 270 duration and .209 @.050. That is what I want but cannot find that grind. The F303 has .226 @ .050. and the Bcam is .224 @ .050. Most all of the aftermarket cam's have more going on early like the F303. The closest I've found is Comp Cams 35-420-8 with an advertised 533/270 and .215 @ .050. I'll ask my builder friend if that is too far. I really want the OE Cobra cam.

SW
66 Cyclone GT; 245/60R15's on 15x8's and 215/70R15's on 15x7 Magnum's.
There's nothing like the sound of a pushrod V8 singing at the top of her lung's.
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Joined: Wed Jun 06, 2012 4:47 am
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Re: GT40 head's and installing heavier spring's.

Postby Rocket989 » Wed Jan 18, 2017 7:46 am

Stacey - that lift on the Cobra cam was with 1.7 rockers. I believe I have one in the parts stash. It's basically an HO cam with a bit less duration and a slightly wider LSA, combined with the higher lift provided via the rockers. Only used in the '93 Cobras and '93 5.0 T-birds. Goal was to help build torque...to help keep low-end in the Cobra that used larger heads/ intake and to help the chubby 'Bird get moving (the 'Birds stuck with stamped 1.6 rockers though)!!

Far as I know, they were never sold OTC or available aftermarket. If I can find mine, you can have it for $20 & shipping (typically 15-17 bones).

I'd use that Comp Cam you listed though!!
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