Why you need to degree your XE-270's
10-28-2006, 04:26 AM
#1
2nd Gear Member
Thread Starter
Join Date: Oct 2006
Location: CA
Posts: 298
Why you need to degree your XE-270's
Here's a follow up of a post I did about a week ago when I installed Comp XE-270AH on my 97 block with PI heads. I found out the hard way that you need to degree the cams so you don't get PTV contact. Question: Are my valves going to be OK? Is there any way to tell by visual or is this something I am going to need a shop to determine? They look fine. I already got cobra (03/04) pistons and tri-metal bearings plus new rings on the way. Any other concerns before I slap this motor back together?
10-28-2006, 03:17 PM
#4
5th Gear Member
Join Date: Apr 2005
Location: South Jersey
Posts: 2,489
RE: Why you need to degree your XE-270's
ORIGINAL: 2000GT4.6
Big cam + PI swap = trouble.
Doesn't look like the valves are damaged though. Is there no damage on the valve stems?
Big cam + PI swap = trouble.
Doesn't look like the valves are damaged though. Is there no damage on the valve stems?
10-28-2006, 03:53 PM
#5
6th Gear Member
Join Date: Jan 2004
Location: United States
Posts: 12,575
RE: Why you need to degree your XE-270's
ORIGINAL: droptoppony
it has nothing to do with the pi swap...look at the pistons and where the contact is made...its on the outter shelf not in the dish so he would have had ptv with a 30cc dished piston. all 2V pistons have the 10mm flat edge around the outside and thats where ptv occurs.
ORIGINAL: 2000GT4.6
Big cam + PI swap = trouble.
Doesn't look like the valves are damaged though. Is there no damage on the valve stems?
Big cam + PI swap = trouble.
Doesn't look like the valves are damaged though. Is there no damage on the valve stems?
Gotta be a reason for it.
10-28-2006, 04:56 PM
#6
5th Gear Member
Join Date: Apr 2005
Location: South Jersey
Posts: 2,489
RE: Why you need to degree your XE-270's
ORIGINAL: 2000GT4.6
They say not to run a aftermarket PI cam in a NPI swap.. and they say not to run a cam bigger than a .500 lift in a NPI engine...
Gotta be a reason for it.
ORIGINAL: droptoppony
it has nothing to do with the pi swap...look at the pistons and where the contact is made...its on the outter shelf not in the dish so he would have had ptv with a 30cc dished piston. all 2V pistons have the 10mm flat edge around the outside and thats where ptv occurs.
ORIGINAL: 2000GT4.6
Big cam + PI swap = trouble.
Doesn't look like the valves are damaged though. Is there no damage on the valve stems?
Big cam + PI swap = trouble.
Doesn't look like the valves are damaged though. Is there no damage on the valve stems?
Gotta be a reason for it.
When i give advice it because i've done it or have 1st hand knowledge of something...I don't take much stock in what "they" say. Because "they" said it is the reason so many of you spread bad info all over these forums because if you read it on the internet it must be true.
The guy posted pics of where the ptv is on his pistons...is it in the dish? No....so "they" are wrong about using high lift cams on a npi shortblock. All cams must be degreed and adjusted properly regarless of what piston is used.
10-28-2006, 10:10 PM
#7
6th Gear Member
Join Date: May 2006
Location: Ohio
Posts: 6,448
RE: Why you need to degree your XE-270's
The reason you have PTV contact is because you used comp cams. Comp cams buts a 5* advanced timing in their cams. If you would have used VT or crower cams you wouldnt have had this problem. I has nothing to do with the PI swap. Non PI engines have flat top pistons so you must degree the comp cams with adjustable cam gears to avoid contact.
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