X-303 camshaft issues

drummerboy5.0 · Jan 3, 2008

couple quick questions..

I'm running a 90 mustang 5.0 with a stock valvetrain, and I am wondering if there would be any piston-to-valve clearance issues with an X-303 camshaft?

do I need different valve springs and/or 1.7 rockers ?

and most importantly, how much vacuum would be lost?

I don't know alot about cams and i'm trying to decide between the ford racing b-303, F-303, and X-303 . I'm pretty sure i'm going to go with the X cam because it sounds the meanest, but any opinions would be greatly appreciated

PJC Racing · Jan 3, 2008

You are going to need to provide more info on your combo to get a good answer.

5spd GT · Jan 3, 2008

Your going to need to get new springs. Those old stock springs are not going to hold tension long.

To find out if the valve is going to hit the piston with a camshaft like the X cam, you need to check yourself to make sure.

You are likely to loose some vacuum, but I do not have the software to compute that for you.

It is my opinion, the X cam is not matched up to well for good performance. If you do decide to get it, I would atleast advance the camshaft 2 or 4 degrees.

Advancing or retarding the camshaft can gain you a bit...although it compromises your performance and power band.

Doing that changes your piston to valve clearance though.

Advancing the timing opens the intake sooner and closes the exhaust sooner. That will gain you some clearance on the exhaust valve, but you will lose clearance on the intake valve.

Retarding the cam causes the timing to open the intake valve later, and closes the exhaust later. You'll gain clearance on the intake, and lose clearance on the exhaust. So changing the cam timing won't result in increasing clearance on both valves.

So it really all depends on which valve you need the most clearance on.

Basic clearance needed is typically .080" for the intake valve and .100" (1/10th of an inch) for the exhaust valve.

Fast63 · Jan 3, 2008

if your engine is all stock, honestly I would just leave the stock cam in there. Aftermarket heads will definitely increase your gains from getting a bigger cam, so I would wait till then.

85_SS_302_Coupe · Jan 3, 2008

On an all stock engine you're not going to get anything except a nice exhaust lope sound and poor performance to back it up. An E303 or B303 would be a far better choice if you were to go with another Ford cam.

That said, you should be able to get an X303 in there without PTV clearance issues but it's never a good idea to take someone's word for it.

PUNISHER RACING · Jan 4, 2008

I run the X with a stock bottom end and p/p E7's carbed. Yes it will fit and I did have ample clearance. I however am running an Excellerator open plenum carb intake and have 4.30 gears. If my combo was more stock like yours I wold lean towards the E cam or the B with upped rear gearing. You will need to change the valve springs to a Crane 44308 kit its like $125.00 buck and will keep your bucket alive. Ditch the 1.7's!

drummerboy5.0 · Jan 4, 2008

PUNISHER RACING
I run the X with a stock bottom end and p/p E7's carbed. Yes it will fit and I did have ample clearance. I however am running an Excellerator open plenum carb intake and have 4.30 gears. If my combo was more stock like yours I wold lean towards the E cam or the B with upped rear gearing. You will need to change the valve springs to a Crane 44308 kit its like $125.00 buck and will keep your bucket alive. Ditch the 1.7's!

thanks bro that helped alot.

but what difference would upped rear end gearing make? just maximize the performance gains that the different powerband would offer?

and why not go to 1.7's?

85_SS_302_Coupe · Jan 4, 2008

drummerboy5.0 said:
thanks bro that helped alot.

but what difference would upped rear end gearing make? just maximize the performance gains that the different powerband would offer?

and why not go to 1.7's?

You don't want 1.7s because you're pushing it with an X303 anyways. At .542 lift (if i remember right) it's already got more lift than you can use with stock heads, so more lift won't do you any good except to rob you of piston to valve clearance.

As for the gear, again your problem is stock heads. You have a cam that wants to scream at 6500RPM and heads that run out of breath around 4500RPM, so throwing a big gear in won't do any good except up to the point where your heads are exhausted. I wouldn't go any higher than 3.73s.

fastford91 · Jan 4, 2008

if your just doing the cam and nothing else B303 is more than enough! its waste to do the X! to much!!! over kill for stock motor!

5spd GT · Jan 4, 2008

I imagine with 1.7:1 ratio rockers, and the new .576" lift, it would not surprise me if the valve spring ran into some coil bind.

If you would like to know the new lift by adding or subtracting an rocker arm ratio, it is quite simple.

Take the given lift with the given rocker ratio.

The X-cam has .542" lift with a 1.6 rocker.

.542"/1.6 = .339" Lobe Lift

.339" x 1.7 = .576"

PUNISHER RACING · Jan 5, 2008

I agree on the B or E cam as well , they sound good to if thats all your after!

Fast63 · Jan 5, 2008

5spd GT said:
I imagine with 1.7:1 ratio rockers, and the new .576" lift, it would not surprise me if the valve spring ran into some coil bind.

For stock springs? Yeah, it would not surprise me if bind happened at even around .525 lift or less.

No matter what cam you decide to get, get new valvesprings to go with it, ones that are matched to the cam. I used the E-303 (.498 lift) with stock valvesprings and it severely weakened them after about 25k miles. I know others have not had issues, but some have so why take any chances you don't want any broken valvesprings or any bind, that's for sure

85_SS_302_Coupe · Jan 5, 2008

Fast63 said:
For stock springs? Yeah, it would not surprise me if bind happened at even around .525 lift or less.

No matter what cam you decide to get, get new valvesprings to go with it, ones that are matched to the cam. I used the E-303 (.498 lift) with stock valvesprings and it severely weakened them after about 25k miles. I know others have not had issues, but some have so why take any chances you don't want any broken valvesprings or any bind, that's for sure

Yeah and even if you didn't get bind, you'll surely get valve float out the ass with stock springs and a X cam.

PUNISHER RACING · Jan 6, 2008

switch out the springs regardless of what cam you use, the added lift and duration will bust them weak stockers up. crane makes a kit for 125.00 bucks and it gives you springs,retainers,and locks, good to .550 lift. part # 44308

X-303 camshaft issues

drummerboy5.0

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PJC Racing

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5spd GT

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Fast63

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85_SS_302_Coupe

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85_SS_302_Coupe

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