GT40 valvetrain question

[Decurion]

After a long time debating what heads I was going to use, I got a set of decent used gt40 (f3ze) heads for $75 complete. Ill do a little port cleanup on 'em, mill 'em, valve job, and have a decent set of heads for notta lotta dough. Ill be using a stock HO roller cam with 1.7 rockers and will be keeping it under 6,000 rpm, so its not like I need some race setup. Ive heard people claim that the stock springs are good for something like ~.515 lift. I plan on a set of retainers to eliminate the multi piece stockers. My question is regarding the springs. What size does it use, what size can I get away with and not have to do any extra machining, and can I just use the old springs?

Also, how much is it safe to mill these heads? The general rule Ive heard is that after about .030 you may need to face the intake side so the intake will actually bolt up with out a fight.

 

[dbfarr]

I used the trick flow spring kit and am running the tfs 1, have had no problems.

Using comp cams red, no longer made, pedestal roller rockers.

The spring kit sits at 1.8 height and is adjusted with shims. Very few of mine required shims.

Anyway, the 5.0 forums have a wealth of information on these heads. Seems a lotta guys are getting into the 13's with just a gt40 iron head swap and the tfs1 at 1.6.

Oh, and the stock springs are considered only good to about 450 ish. In other words, they are crap.

As for me, these heads have made my day

 

[phutch11]

I used the ffpp springs - "b"; I think. Call them and they can tell you what to use. I also run an E cam, so they should handle your combo.

I milled my heads .030; but you really need to cc the heads to make sure they haven't already been milled. Had no problems with the intake, but had to go with custom pushrods and adjustable roller rockers to get the geometry correct.

Good luck with your heads...

Posted via Mobile Device

 

[Decurion]

I did some looking on the Fordracingparts website, and came up with the springs and retainers. M-6513-a50 for the springs and m-6514-a50 for the retainers. Theyre $76 and $50 from Jegs. Only thing is I dont see anywhere what the max. lift is, and it gives the spring pressure at only .420 lift, which is odd since even the stock cam gives .445 lift.

 

[dbfarr]

What block are you running, early or late?

 

[woodsnake]

When you purchase your new cam, find out what springs the cam manufacturor reccomends. Check for the correct installed height of the springs, and verify your valve train geometry.

Or not, it's your money.

 

[Decurion]

Pre-roller block (mid 70s I think), KB hypereutectic pistons with valve reliefs like the H.O. pistons. I plan to use the stock H.O. cam with link-bar lifters and 1.7 roller rockers. I had a bigger flat tappet cam in it, but wiped it out, so piston to valve clearance is not an issue if thats what you were getting at.

 

[Decurion]

dbfarr, did you have to machine the guides to use the TFS kit? I have looked at every valve spring set I can find, and none have the correct inside diameter to use without machining. The TFS kit looks pretty nice, so I may have to just bite the bullet and have the heads machined to use that kit. I ordered the FRPP springs, but theyre on backorder and the rep at Jegs said he has seen a few sets on backorder for a long time now, and I need to get these heads back together in the next week or so.

 

[v8only]

if they're explorer heads, then you'll want to change the springs.

if they're stock cobra heads, then they came with crane springs and they'll be more than fine with an HO cam

 

[Decurion]

I already dropped the heads off to have them machined for the TFS kit. They said the Ford Racing springs are on galaxy wide backorder because the springs were made by Crane, which is dead and gone and never to return. Nobody makes a direct fit spring for that head that they or I could find.

 

[DJCarbine]

I already dropped the heads off to have them machined for the TFS kit. They said the Ford Racing springs are on galaxy wide backorder because the springs were made by Crane, which is dead and gone and never to return. Nobody makes a direct fit spring for that head that they or I could find.

I've been out of the loop too long, I didn't even know crane cams went kaput

 

[woodsnake]

Trick flow springs??

Trick Flow Specialties TFS-31400414 - Trick Flow® Valve Springs - Overview - SummitRacing.com


Trick Flow Specialties TFS-51400413 - Trick Flow® Valve Springs - Overview - SummitRacing.com

Summit has a real neat link that lets you look for "related necessary parts"..

 

[Decurion]

I went with this one: Trick Flow Specialties TFS-2500100 - Trick Flow® Valve Spring Upgrade Kits - Overview - SummitRacing.com Its so cheap, Id be dumb to go any other way.

 

[woodsnake]

Good call!