barrman : 396 Woes

396 Woes
Post by barrman on Jul 5, 2006, 1:37pm

I spread out the machine work on the 396 over 2 years for money reasons. I assembled it and installed it in April 2005. The thing ran great and never has leaked or used any oil. But, about 200 miles into the new engine I started hearing a ticking while driving at 2000 rpm or more.

I did every kind of valve lash adjustment I could find and made up a few more. None helped. I could put my hand on the rocker at idle and the noise would stop. 16 new rockers later. Same noise. 16 new push rods later and still the same. I decided it must be the special groove the machine shop had to machine into the back of the cam for the 1966 396 oiling that wasn't letting enough oil get to the lifter. Out comes the cam. Looks great. Lots of oil getting to the lifters. Machine shop says the cam is good. They also tell me "big blocks make a lot of valve noise." I write a big thing about it last May on the Zone and many others agree. "Big blocks make a lot of valve noise."

I drive it daily and at the Texas FE, Al tells me about the trouble Chevy had in the past with over sized lifter bores and the noise it makes. I am convinced that is what it is and ignore the noise.

The only problem is that I can't ignore it. It is only the number 3 exhaust valve doing it. I convince Edelbrock to send me another set of lifters. I swap them out and no change.

Then out of nowhere last week it clicks. What about the valve spring? The outside one looks ok, but the inner could be broken and I would never know without taking it apart. I pull the rockers off yesterday and put the air hose in the plug hole to hold up the valve. I can feel air around the valve spring. I put the spring compressor on the spring and can wiggle the valve. The noise almost goes away depending on which way I hold the valve. I go ahead and pull the spring off. Looks good. But, I have a valve seat that isn't sealing and a valve guide that allows wiggle.

I call the machine shop and describe what I did. I remind him that he charged me for 16 new valves, valve seats and valve guides. Along with valve springs and keepers. He gets one of those "oh sheeet" voices and tells me to bring him the head. I tell him to have a complete gasket set, 2 gallons Dexcool and 2 gallons distilled water ready for me to pick up. I will bring the head to him after I get that. He said to come on by. We will see.

Can anyone think of another cause for the valve to be this loose with less than 5,000 miles besides a bad or wrongly installed valve guide?

Thanks.

Re: 396 Woes
Post by elwenil on Jul 5, 2006, 2:02pm

I have seen the guides themselves move around in the head from either a botched job or poor quality guide. I'm not even going to go into my Mopar 383 in my W100 with it's diesel engine sound. Mopars don't have adjustable drivetrain and the valve heights have to be taken into account when doing a valve job. Your average Chevy machinist apparently has no clue about this. Grrr...

Re: 396 Woes
Post by brute4c on Jul 5, 2006, 2:03pm

When all the others are fine....abuse...I know you well enough to rule that out...and sobotage....but how could anyone...

Re: 396 Woes
Post by jeepistdougiowa on Jul 5, 2006, 2:20pm

A exhaust valve set too tight can act as a torch blowing thur the exhaust runner. Heat kills everything.

MIght see some evidence of this on the valve seat and valve...they could also appear fine it it was corrected early on during readjustment of the valves and now worn in.

Re: 396 Woes
Post by tacomainoh on Jul 5, 2006, 6:54pm

I think you're right on the money... There are only a couple factors in proper valve seating, and you've got problems with both, it seems.