302 question
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Senior User
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302 question
I have a motor out of a 1990 mustang gt my question is can i install a regular cam instead of a roller cam. And has anyone ever installed a x303 cam in there 302. Can you put on new valve springs without removing the heads.
Elder User
Joined: Mar 2004
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Yes, you can install a flat tappet cam in a roller block, but you need to change the gear on the distributor and use different pushrods.
The X303 is a race cam. It's a B303 with a lot more lift (.542/.542). You must check your piston to valve clearances on a stock 302. I recall dealing with it on a friend's GT40X head crate motor, and it is for high rpm power (6500rpm HP peak). It really requires better than stock cast iron heads to do any good. In my experiance it had a very rough idle, but all those FMS cams, from E, B, F, and X, have roughly the same 62* of overlap, and idle pretty much the same with EFI. It didn't really idle below 1000rpm, but I think the builders of the Crate (not Ford Racing) hadn't adjusted the valves properly as well.
The X303 or the like will require better than stock valve springs. I've heard of changing valve springs without removing the heads, but I have never tryed it.
The B303, (or E303 or HO) would be a better choice with stock heads, and in most any type of truck application.
What do plan on using it in?
The X303 is a race cam. It's a B303 with a lot more lift (.542/.542). You must check your piston to valve clearances on a stock 302. I recall dealing with it on a friend's GT40X head crate motor, and it is for high rpm power (6500rpm HP peak). It really requires better than stock cast iron heads to do any good. In my experiance it had a very rough idle, but all those FMS cams, from E, B, F, and X, have roughly the same 62* of overlap, and idle pretty much the same with EFI. It didn't really idle below 1000rpm, but I think the builders of the Crate (not Ford Racing) hadn't adjusted the valves properly as well.
The X303 or the like will require better than stock valve springs. I've heard of changing valve springs without removing the heads, but I have never tryed it.
The B303, (or E303 or HO) would be a better choice with stock heads, and in most any type of truck application.
What do plan on using it in?
Last edited by P51D Mustang; Sep 27, 2006 at 03:41 PM.
Hotshot
Joined: Jul 2002
Posts: 14,285
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From: Bend,OR
i agree stick with roller if you can afford it. also you might try going with a 1.7 rocker and stay with your current cam. changing the springs while the heads are on the motor could be bad if the valve fell into the cylinder, then your tearing the heads off anyway. no real shortcuts on this one i am afraid.
I would call compcams and tell them what you are looking for out of your rig and have them help you out. they can also recommend the right springs/lifters and pushrods if necessary as well.
I would call compcams and tell them what you are looking for out of your rig and have them help you out. they can also recommend the right springs/lifters and pushrods if necessary as well.
Fleet Mechanic
Joined: Aug 2004
Posts: 1,276
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From: NE Tennessee
I changed vale springs on a 460 with the heads on. Used the ol' string in the spark plug hole trick. Worked well but was alot of work. Easier than taking the heads off though.
I agree with the changing rocker arm ratios. Easier and will work better unless you plan on working on the breathing of the engine (intake, heads, exhaust). Remember its a 302 in a truck ( I guess ) so you really want torque more than hp. Torque makes a fun street motor.
I agree with the changing rocker arm ratios. Easier and will work better unless you plan on working on the breathing of the engine (intake, heads, exhaust). Remember its a 302 in a truck ( I guess ) so you really want torque more than hp. Torque makes a fun street motor.
Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
The X303 isn't that radical. I've run the Z303 with 1.7 rockers in a 331 and it idled pretty smooth, not unlike a B303 in a 302. Both were carbed though. I was able to idle the 331 at 6-700 rpms with the Z. And total lift is only one part of the equation when it comes to piston to valve clearance, duration and the timing events have more to do with it than total lift. With an X cam, you'll have to change valve springs, the stockers will bind at around .520 lift. Changing them without pulling the heads isn't that hard if you use an air compresser and a spark plug adapter to plug the air hose to. You could change the springs in an hour or so.
Junior User
Joined: Dec 2005
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Yes,
You can change the valve springs without removing the heads.
Do you have or have access to an air compressor?
Get an air fitting that is the same size as your spark plug, fill the cylinder with a constant air pressure, if you have good rings and the valve do not leak the air pressure will hold the valves up in place.
Remove all the spark plugs first, the air pressure will force the piston to BDC each time you change cylinders.
Changed alot of valve stem seals this way.
Hope my 2 cents helps.
KenZ28
You can change the valve springs without removing the heads.
Do you have or have access to an air compressor?
Get an air fitting that is the same size as your spark plug, fill the cylinder with a constant air pressure, if you have good rings and the valve do not leak the air pressure will hold the valves up in place.
Remove all the spark plugs first, the air pressure will force the piston to BDC each time you change cylinders.
Changed alot of valve stem seals this way.
Hope my 2 cents helps.
KenZ28
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Elder User
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Originally Posted by baddad457
The X303 isn't that radical. I've run the Z303 with 1.7 rockers in a 331 and it idled pretty smooth, not unlike a B303 in a 302. Both were carbed though. I was able to idle the 331 at 6-700 rpms with the Z.
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Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
The X ought to be just as torquey as the B as they both share the same duration, just the X has a bit more lift. I've run the B in a 302 with 1.7 rockers and it was OK on the bottom with a dual plane intake, ported E7's and a 650 Holley. But with the same short block with Canfield heads and a Vic jr., it was sorely lacking on the bottom. The 331 has the same heads but with the Z cam and a repop factory 3x2 high rise dual plane with three Holley 250's and it's way more street friendly than the B cam was with the Vic.Jr.
Fleet Mechanic
Joined: Aug 2004
Posts: 1,276
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From: NE Tennessee
Yeah manifold selection will have alot to do with bottom and top end performance. A single plane usually isn't a good 'street' selection. Trucks usually do better with a performer or weiend duel plane set up with carb. You gonna go efi or carb?
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