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sec 01-18-2008 11:15 AM

cam
 
just wondering what is the maximun lift on a cam I can use with 1.7 rockers?

mjr46 01-18-2008 11:40 AM

RE: cam
 
lift is not a determining factor of ptv it is cam timing that'll affect ptv more than anything..but what size cam are you thinking of and are you planning on putting 1.7's on top of that??

5spd GT 01-18-2008 11:44 AM

RE: cam
 
Yep, gross valve lift is not the reason for piston to valve clearance problems.

It is during the period of overlap when the exhaust valve is closing (as the piston is coming up) and the intake valve is opening. They are both open at the same time for a short time while the piston is at top dead center.

The 1.7:1 ratio is a bit harsher on valve springs, so keep that in mind.

Get a good valvetrain...

sec 01-18-2008 01:11 PM

RE: cam
 
I'll look tonight to see specs on cam, at work now and can't remember. Sold my 89 GT and just bought this 90 coupe(been looking for a coupe for a long time)and the guy had the stock heads ported, with heavier springs and 1.7's put on them. I bought a cam for my old 89 but didn't get it in before I sold it. It's a crane but I believe it matched pretty close to the e-cam ford offers. Thanks in advance.

sec 01-19-2008 01:14 PM

RE: cam
 
OK, I just looked at the cam card. Its a Crane Cam and has .311 cam lift and .498 at the valve. 282 avertised duration. So correct me if i'm wrong, but that should be roughly .529 with the 1.7s. Can anyone tell me if this is going to be too much lift. I know I should do a piston to valve check to be sure but just thought someone would know off the top of their head. Engine has stock pistons and unmilled heads that have mildly ported and polished and stiffer springs installed(not sure which ones). Thank you.

mjr46 01-19-2008 03:31 PM

RE: cam
 

ORIGINAL: sec

OK, I just looked at the cam card. Its a Crane Cam and has .311 cam lift and .498 at the valve. 282 avertised duration. So correct me if i'm wrong, but that should be roughly .529 with the 1.7s. Can anyone tell me if this is going to be too much lift. I know I should do a piston to valve check to be sure but just thought someone would know off the top of their head. Engine has stock pistons and unmilled heads that have mildly ported and polished and stiffer springs installed(not sure which ones). Thank you.
I know it's more work but the proper way is to clay the pistons with any cam swap and check for ptv using the proper tools;)

Joel5.0 01-19-2008 05:08 PM

RE: cam
 

ORIGINAL: sec

OK, I just looked at the cam card. Its a Crane Cam and has .311 cam lift and .498 at the valve. 282 avertised duration. So correct me if i'm wrong, but that should be roughly .529 with the 1.7s. Can anyone tell me if this is going to be too much lift. I know I should do a piston to valve check to be sure but just thought someone would know off the top of their head. Engine has stock pistons and unmilled heads that have mildly ported and polished and stiffer springs installed(not sure which ones). Thank you.
Looks like you have an E-303 cam (aka Powermax 2040). Based on its events, I still have to see one cause PtV issues.... but it's less expensive to be 200% sure with a clay test. Do suggest to make sure you have the correct valve springs/retainers setup though.

5spd GT 01-19-2008 05:58 PM

RE: cam
 
Your math is right. Remember, the lift is not going to cause the issue with piston to valve clearance.

Read over this link for the clay method.


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