Ford 302 question

jdubb

jdubb

Well-Known Member
Joined
Apr 12, 2005
Location
Gastonia
buddy has '76 Bronco 302 and he slapped GT40 heads on it. The cam he used says .472 lift on exhaust but the springs wont do it and he broke a rocker shoulder bolt. Does it need custom push rods or head work for more spring clearance? Isn't this a common swap?
 
The valve springs will have to be changed. The existing springs can not handle that much lift. Will likely need double springs that can compress beyond the lift and rocker arm ratio with room to spare.
 
He will need new springs that can handle more lift but still have the same seat and open pressure at the same installed height as the old springs. If he broke a rocker stud he will probably need new pushrods just because the old ones may be bent. Also make sure you have the right length pushrods.

Luke
 
302

Yes you will need new springs Those heads with stock springs are only for .500" max lift. The newer GT 40 heads are for .550" lift New push rods yes Do you know if the heads have been worked on? It kinda sounds like the spring pressure was a little high
 
I don't know anything about the heads but the guy that built the engine for him said the cam is supposed to be. 472 exhaust lift.
 
ive got a new set of double motorsport springs for stock style 5.0 heads . they will work on your gt40 heads with that little cam. $100.00 free shipping.
 
I put a Melling MTF-1 in my old 302. It is probably the same grind; 204 int./214 exh. 0.448 int./0.472 exh. lift 112CL.

I had to swap springs on my heads. It would float the valves if I ran it too tight in 1st gear. Otherwise the rockers and push rods where stock.

Are you sure he didn't just over torque the bolt? They are rather small 5/16 bolts. The bolts only torque 18-20 ft/lbs.
 
the pushrod length needs to be checked for sure. if it is breaking rocker studs/bolts be certain that the spring retainers are not coming into contact with the valve seals and guides. i know that stated lift is only .472 but depending on the spring retainers and the type of seal being used clearance could be an issue. also might want to check the preload on the lifters. if it has bolts they are non adjustable rockers and have to be shimmed for proper preload.
 
i would pull a head off and look. My best guess is the valve is slapping the top of the pistons. The truck pistons dont have the fly cut valve reliefs in them like the mustang 5.0s and your probably running into interference problems. the springs should handle it.
 
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