Comp Cam Guide Plates
Thread Starter
Safety Car
Joined: Dec 2012
Posts: 3,815
Likes: 1,726
From: Summerville SC
Comp Cam Guide Plates
I have a 1986 L98 with aluminum heads and putting roller rockers on them. Got new Comp 4808 guide plates and when I go to put them on, the holes for the studs are a hair too close together. I can feel the studs binding and I can just barely get them both started. When I put the new plates up agains the old plates, there is a noticeable difference in the spacing of the holes. I was trying to be PROACTIVE here but replacing the guideplates that came on the aluminum heads even though they are marked "05" which I understand to be the GM hardened plates. I didn't want to take any chances since there is some arguement as to wether they are hardened or not so I bought the new ones. So how do I make the holes a tiny bit larger for the studs to align with the bosses in the heads?Any help would be appreciated. Thanks.
Melting Slicks
Joined: Nov 2010
Posts: 2,216
Likes: 113
From: Michigan
Just make the holes larger how ever you can, before adjustable guide plates people would say to try and move the guide plates to get the best line up of the rockers. That would imply that that some slop or play was the norm and from my experience on other heads it is. I used adjustable on mine, takes forever to get them lined up and snugged down "just right" before you torque them LOL. Some will say to weld adjustable plates but I haven't on any of my cars and no issues.
Last edited by BOOT77; Oct 25, 2015 at 05:00 PM.
Thread Starter
Safety Car
Joined: Dec 2012
Posts: 3,815
Likes: 1,726
From: Summerville SC
I figured there should be some SLOP in them. I am waiting on some ARP bolts that should arrive tomorrow, so once they are here I will fgure how to enlarge the holes ase needed. Thanks.
Pro
Joined: Jan 2003
Posts: 706
Likes: 47
From: Denver Colorado
For the minor bind on the guide plates, try breaking just the edges of the holes with a conical grinding stone in a Dremel tool or a die grinder. It may be that the manufacturer was at the end of his tool life when yours were produced so the holes are at minimum spec.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Before hogging out the holes, try contacting Comp Cam ask them what's going on. Take some pics of their plates and yours as you have mentioned and email them to Comp Cams.
Once you start grinding on them, they will not be returnable even if their plates were not made properly.
Once you start grinding on them, they will not be returnable even if their plates were not made properly.
Thread Starter
Safety Car
Joined: Dec 2012
Posts: 3,815
Likes: 1,726
From: Summerville SC
Excellent idea. Maybe even putting a digital caliper to them. It's only a small difference but after I managed to get the old studs in, as I took them out the threads were getting hung up on the plates. I certainly don't want to screw up the threads in the heads. Thanks.
Melting Slicks
Joined: Sep 2010
Posts: 2,422
Likes: 202
I have Isky Adjustables. They do a great job keeping your push rods centered. I ground the male & female guide connector slightly. To dial in center. Traditional plates were slightly off.
Last edited by THE 383 admiral; Oct 27, 2015 at 09:45 AM.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Never seen or heard of guide plates that fit correctly out of the box. But usually its the p-rods that are dragging or dont fit in the slot - not the stud holes. That some sloppy manfr QC or else those are the wrong application. Do u have larger 7/16" studs?
Regardless guide plates aint rocket science. U just want the p-rod to slide in the slot w/o heavy drag - touch is ok just not draggy at all or u will create wear. Dont be afraid to touch the slots or the stud holes to fit them up. So before u ask about p-rod slots just get the p-rod to move freely - no large clearance needed. BTW are your p-rods hardened? They have to be or the G/P will eat them up. Just try a light swipe with a file and if the file bites the p-rod it aint hardened.
Hope this helps.
Regardless guide plates aint rocket science. U just want the p-rod to slide in the slot w/o heavy drag - touch is ok just not draggy at all or u will create wear. Dont be afraid to touch the slots or the stud holes to fit them up. So before u ask about p-rod slots just get the p-rod to move freely - no large clearance needed. BTW are your p-rods hardened? They have to be or the G/P will eat them up. Just try a light swipe with a file and if the file bites the p-rod it aint hardened.
Hope this helps.
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Thread Starter
Safety Car
Joined: Dec 2012
Posts: 3,815
Likes: 1,726
From: Summerville SC
So I contacted Comp Cams and after pics and measurements, they told me there wasn't much they could do so I should return them and buy a set of adjustable guides. The hardened rods fit in them fine, just can't get the studs started. In the meantime I spoke with a few engine shops here in CHarleston and I was told that the OEM guides I have will work fine. Remember, these are not the ASSEMBLY plates, but the ones sold by GMPP that are on the car. It's an oddball with stock aluminum heads and flat tappet cam. They are hardened. The only issue will be if I go to a higher lift cam, then the geometry will push the rods further up which will require a LONGER slot in the plates. Not going any higher so I think I will go with what I got. Thanks for all the thoughts.