Big Block Blues
Post by barrman on Jul 21, 2006, 12:47pm
I had a local machine shop do the heads on my 1966 396 Chevy Big Block 2-1/2 years ago. I assembled the engine in March 2005 and installed it in the M715 2 APR 06. Less than 200 miles later, I started hearing a ticking noise. I thought it was valve adjustment and got very good at valve cover removal/instalation.
I still had a tick
The 1965-1966 Chevy Big Blocks had a different way of oiling the lifters and engine upper end than all 1967-present engines. A groove in the rear bearing of the cam had to be cut in my cam and 1966 only bearings had to be used. The same shop did the groove to my Edelbrock Performer cam.
I was getting oil to the top of the engine. Some push rods where spraying oil and some just pulsing a little. I suspected the groove. Out comes the cam. The shop looks at it and compared to the original, everything looks good. With the cam in the engine and the lifters pulled I could use a drill to turn the oil pump and still get oil blasting out the front of each lifter gallery. Oil was getting to the lifters. Engine goes back together. The machine shop and I start looking at the push rods and rocker arms. They are kind of worn, so I buy 16 of each.
I still hear the tick.
The shop tells me "Big blocks do that sometimes, just drive it."
I narrow it down to the #3 exhaust valve. I can put my hand on it while the engine is running and the noise stops. If I tighten it down more, I loose compression. So, I think the lifter is bad.
Edelbrock sends me a new one. I install it.
I still hear the tick.
Al Nelson at the Texas FE convinces me that it could be the lifter bore is oversized and we both agree nothing can be done without a complete tear down. I drive it.
I think up something else last month. Inner vavle spring. I put air to the cylinder to hold the valve up while I pull the spring. I can hear air flowing around the springs. I jiggle the valve and the air flow changes. Not good.
I call the machine shop up and tell them my guide is shot. He agrees to look at it and take care of it.
I pull the head on Wednesday night and take it to him on Thursday. He tells me all 4 exhaust valve guides are shot along with the valves. He said it is because I ran the engine too rich and that he won't charge me labor, but I have to buy the valves and guides.
I tell him that my air/fuel mixture was 14.8:1 last week acording to my fancy Snap-On flexible gas analyzer and it has never been richer than 14.2:1 or leaner than 15.1:1 over the last year. Which is basically all of the engines 3124 mile life. He says that it couldn't be the guides because the all went and that it had to be driver induced. He also said to bring in the other head.
I pulled it off last night and took it to him this morning. They are bad too.
I called a few other machine shops up and talked to them about this. They can't think of any reason why my driving slow or a rich start up condition would cause the guides to go. They tell me that the guides where probably installed wrong or the seats weren't properly matted to the valves and that my shop is just not wanting to accept blame. I agree.
but, the other shops all want at least $250 to fix it now. My shop is going to charge me $70 and have them both ready next week. The guy who did the head work doesn't work there anymore. The guy who did my block and cam work is a big block fanatic and is a good guy.
I don't like it, but I will pay the $70 to get them back and the truck running next week. I know if I throw a big fit, they might "accidentally" slow down my work or break something else. But, I send a lot of business their way and influence about 400 people on where to get work done.
Can anybody think of a reason all 8 exhaust guides would go in the first 3000 miles that wasn't workmanship related?
Anybody think it is because I use 5th gear a lot and lug the engine around at 1000-2000 rpm a lot?
How would a rich mixture cause the valve stems to tear up the seats? I still haven't figured that one out.
Should I throw a fit and threaten his future business or just let it be and not refer people to him anymore?
Thanks.