Valvetrain noise

[hotrod68]

Hey guys:  I'm hoping there is an aftermarket tech guy in the forum who might help me. I replaced the roller cam in my '68 with a small base-circle roller and now from idle (1200) to around 2500 rpm the rocker arms are raising all kinds of cain. The cam is a Comp Cams solid roller with the new X-Treme lifters that oil the rollers on the lifters. I double-checked the valvetrain geometry on assembly and it looks good. The valves are lashed to Comp specs. The heads are AFR 210s with 7/16" studs and the rockers are Comp stainless rollers. This makes absolutely no sense, and I'm wondering if anyone has ever encountered this before. Any help would be greatly appreciated. Thanks.

[BlackoutSteve]

Assuming a solid when you say you lashed it to spec.. ..or is it a hydraulic?
Are you using longer pushrods to make up for the smaller base circle?
Are the rocker arms hitting the retainers or interferring with the guide plates?
Have you lashed the valves using the eo/ic method or TDC method?

[hotrod68]

Steve...it's a solid roller with fairly radical specs... .577/.583, 248/254 @ .050" with a 106 degree intake centerline, 110-degree LSA. When I installed it I double-checked the rocker roller pattern on the valve tip and it was running on the center 1/3 of the valve tip with .100" longer than stock pushrods. There are no clearance probs with the retainers or guideplates that I could tell--there is good clearance between the rocker body and retainers, and the pushrods spin freely in the guideplates at TDC. I lashed the valves using the TDC method with the spark plugs removed and the pistons at TDC on each cylinder. I'm plumb puzzled--I've never had this happen before. I had a Lunati solid roller in it before this cam, and it was as quiet as you could expect solid lifters to be. I've emailed Comp Cams but have gotten no reply. Thanks.

[JohnZ]

I lashed the valves using the TDC method with the spark plugs removed and the pistons at TDC on each cylinder.

Can you expand a bit on the "TDC method" you used to lash the valves? With that much duration and overlap, the EOIC method usually gives better results.

[hotrod68]

John--I remove all the plugs and get each individual cylinder to TDC by turning the crank with a pull bar. I get a cylinder on the compression stroke, then use a small screwdriver to feel for the piston to get to TDC, then lash both valves with the piston at TDC. This has always worked before, so as I said--I'm puzzled. Thanks.

[JohnZ]

John--I remove all the plugs and get each individual cylinder to TDC by turning the crank with a pull bar. I get a cylinder on the compression stroke, then use a small screwdriver to feel for the piston to get to TDC, then lash both valves with the piston at TDC. This has always worked before, so as I said--I'm puzzled. Thanks.

I asked the question (TDC vs. EOIC) because the TDC method isn't effective with a factory "30-30" cam, as the lifters are still on the ramps at TDC due to the extreme duration; see this article:

http://www.camaros.org/302valves.shtml

Your cam is fairly radical, and may exhibit similar characteristics; Comp Cams technical guys should be able to confirm one way or the other.

[BlackoutSteve]

To elaborate on the EO/IC method in case you are unfamiliar with it..
On each cylinder, when the Exhaust is begining to open, lash the Intake..
Then, when the Intake is about to close, lash the Exhaust..
This will ensure that the valve being lashed is positively on the heal of it's lobe.

With #1 at TDC and firing stroke, you with be able to then lash #7's Intake and #4's Exhaust and then 8436572 respectively for each firing stroke and valve. (ie: next, rotate to #8 TDC and lash #2 Int & #3 Exh and so on.)

One thing you will most likely see is the lash got tighter when you rotate it to TDC and check again, -indicating that the lifter is now on a slight ramp. It might only be a few thou, but some radical cams will show a lot.
Basically, the TDC method will result in too much lash. Hope this helps.

This may not eliminate your noise, but will at least eliminate one probable.  

PS: Check guide plate-pushrod clearance through out valve lift.. As the rocker opens the valve, the clearance generally gets tighter.
Doing a cam dial-in, I once had a set of inaccurately stamped guide plates and it did my head in until I found them out. They would have killed my pushrods in minutes if the engine had have run with them.

[hotrod68]

Thanks a lot guys--I'll probably try and redo the valves this weekend and I'll post how it went if I do. Fellows like you are the heart of what helps keep our old hotrods alive. Long live the 1st-Generation!