daanbc

I called comp cam and asked about springs. The said they recommend new springs, But for my cam and the mileage of the car, I could probably get away with it. I have not even put 17 miles on it. Everything was fine last week. This all started yesterday. There is No noise from the valve covers. Just the popping from the exhaust. Took the valve covers off today, checked all push rods - all are straight and clog free. The lifters are new Crane anti-pump up ones. I don't believe I wiped a lobe yet. Keeping my fingers crossed. So now I'll get new springs and seals and install and see how this works out. Thanks...

cardo0

From over 2,000 miles away here in cal it sounds more like a dist/timing problem. Can u see the timing advance when you increase rpm (with timing light)? Sometimes the centrifugal weights bind up and quit.

Trying to measure vlv spring spacing is something new to me and i would expect it would have been a problem from the very start not a degrading issue. Weak vlv springs lose at top end rpm but operate normal at idle. How is your rocker pattern on the vlv tip? Side loading the vlv stem will wear it out in no time. Did you measure for p-rod length?

Now vacuum leaks can get crazy on u too and they do cause poping also. Did u measure idle vacuum yet?? At least 12"Hg? Heck could be a mixure problem too. When u say u adjusted the idle screws and nothing happened means it not responding to the idle circuit. Are u getting black smoke out the exhuast (too rich)?? Are u getting blogs when u open the secoundaries (lean)??

I would focus on distributor timing and carb,
cardo0

scottyp99

Hmmmm.........the xe268h cam doesn't have that much lift, .480" on the exhaust valve, right? The L82 cam had .460" on the exhaust valve, and used the same stock valve springs as the L48, I think. Are you running higher than stock rocker arm ratio? I don't seem to remember you mentioning anything about it. You didn't shim the valve springs or anything, did you? Have you tried re-adjusting the valves? I have never experienced it myself, but I seem to remember reading about tight valves not being able to close all the way, and giving a popping sound from the exhaust, but I could be all turned around on that. But why would the valve be tight all of a sudden? They sure aren't going to tighten themselves, if anything they would loosen. Man, I'm in over my head here. If I weren't such a logical, rational person I would say you have a ghost in your engine! Good luck, and definitely let us know what the problem turns out to be. I'm rooting for ya!


Keep the shiny side up!
Scott

daanbc

Yeah I re-adjusted the valves again. They still bind. Funny because I checked them when I first installed the cam two weeks ago. I made sure there was .060 between the coils. I am assuming that the few times I took it down the street and back, and the one night I took it to Barrett Jackson (1-1/2 miles from my house) They probably wore/loosened up. I am ordering new springs from summit with clips/retainers/and guides. It's deff. not timing or electrical. I know it's the springs now. I just took the exhaust one off on the number 1 cylinder. I also found some broken bits of plastic, looks like part of the seal.

hugie82

You must have a pretty high lift cam to be binding the valve springs...

daanbc

Not really. XE268H = Valve Lift Intake and Exhaust: .477/.480 gross
---Duration at .050: @.050 = 224 intake/231 exhaust
---Advertised Duration: .006 tappet lift 268/280
I think my springs are just tired and old.(35 yrs)

scottyp99

Something here just doesn't add up. If they weren't binding before, why are they binding now? Just being old and tired won't make them bind. Well, anyway, if Comp Cams said that the stock springs would work if they were not too worn, then a new set of stock springs should work, right? You might even think about getting a cheap set of Z28 springs for a little extra insurance. I believe the springs that Comp Cams recommends for the XE cams are the 981-16 springs, if that's what you decide to do.

http://www.kmjent.com/cart/product.php?productid=735


Keep the shiny side up!
Scott

daanbc

I'm getting the Summit # 174000 kit.

mds3013

What you show in the pics. is indeed the valve stem seal. On a SBC they are just a square sided O-ring that fits into the bottom groove of the valve stem. Mine came out in pieces also. Good luck, watching to see what you find. mike...

dannyman

Did you replace the lifters when you changed the cam?

Something you changed had to have change the geometry if the cam lift is similar to the original.

Is there a possibility that the lifters are taller than stock?

Or, overtightened?







Dan

scottyp99

springs, retainers, locks, and seals for 70 bucks, sounds like a pretty good deal!


Keep the shiny side up!
Scott

daanbc

Yes the lifters are Crane anti pump up lifters. As for the cam, it is deff. Different then the original. I will keep you all informed as I progress from here. Thanks mds 3013.

OzzyTom

Were the Crane anti pump lifters new (unused) when installed with the current cam?
Maybe one of them has seized causing slight excess pushrod travel resulting in coil bind ???? Just a thought.

daanbc

New, it's not just one spring. In fact when I did initially check the Clarence of the springs I checked # 1 and # 8 cylinders. And they are now binding, along with the others.

70BBvert

How are you adjusting the valves? With the engine off or running? It's very easy to over adjust them cold.

Jim

daanbc

Did it both ways. Tried to leave them as loose as possible with out hearing the noise, thinking it would stop the binding. Dummy me. LOL.

70BBvert

Trust me, I've had my share of stupid mistakes, including over tightening the valves