I felt power loss, but that is about it. The spark plug broke so no popping. I don’t remember any tapping…..
I think I need a new engine?
Thread Starter
Instructor
Joined: Dec 2004
Posts: 230
Likes: 6
From: Washington DC
I think I need a new engine?
Well I was on the highway doing about 75 mph. It was starting to get hot so I turned on the AC. About 2 minutes later, I felt something coming from the engine and the car started to loose power. I turn off the AC and some of the power came back. About 10 minutes later, I slowed to pay a toll and the engine stopped. After getting the car home this is what I found.
I have about 1200 miles on these heads.
Any Ideas what could cause this type of failure?
I have about 1200 miles on these heads.
Any Ideas what could cause this type of failure?
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Possible causes;
Coil bind
Insufficient guide to retainer clearance
Over-revving (valve float)
Insufficient valve to piston clearance
Retainer, valve stem or keeper failure
Cam has too much lift for spring set-up
Have a competent machine shop do forensics on the heads.
BTW, a major engine rebuilder supplied a customer with a long block. Lasted 300 miles. Coil bind. You have to check everything these days.
Coil bind
Insufficient guide to retainer clearance
Over-revving (valve float)
Insufficient valve to piston clearance
Retainer, valve stem or keeper failure
Cam has too much lift for spring set-up
Have a competent machine shop do forensics on the heads.
BTW, a major engine rebuilder supplied a customer with a long block. Lasted 300 miles. Coil bind. You have to check everything these days.
Last edited by big_G; Jul 19, 2007 at 01:02 PM. Reason: added info
Thread Starter
Instructor
Joined: Dec 2004
Posts: 230
Likes: 6
From: Washington DC
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Drifting
Joined: Apr 2007
Posts: 1,892
Likes: 3
From: Springfield Illinois
Possible causes;
Coil bind
Insufficient guide to retainer clearance
Over-revving (valve float)
Insufficient valve to piston clearance
Retainer, valve stem or keeper failure
Cam has too much lift for spring set-up
Have a competent machine shop do forensics on the heads.
BTW, a major engine rebuilder supplied a customer with a long block. Lasted 300 miles. Coil bind. You have to check everything these days.
Coil bind
Insufficient guide to retainer clearance
Over-revving (valve float)
Insufficient valve to piston clearance
Retainer, valve stem or keeper failure
Cam has too much lift for spring set-up
Have a competent machine shop do forensics on the heads.
BTW, a major engine rebuilder supplied a customer with a long block. Lasted 300 miles. Coil bind. You have to check everything these days.
You say 1200 miles? i am surprised it even lasted that!!
Le Mans Master
Joined: Mar 2004
Posts: 7,501
Likes: 1,508
From: Little Rock AR
I might suspect the valve stem stuck in the guide and hung open. The piston hit it and bent it enough to break it off. Either that or it was simply a dropped valve. No way that should have happened under those conditions.
If it makes you feel any better I had a cam chain failure on my '98Jaguar twin overhead cam engine a few months ago and it resulted in the same broken valve stem and a ventilated piston. The only difference is if it had been a Chevy I would have fixed it myself. The Jag had to be junked as the cost to fix was higer than the value of the whole stinking car.
P.S. - if any of you happen to own a late 90's early 2000's Jag and have not done the cam chain tensioner upgrades yet, send me a PM RIGHT AWAY.
-Mark.
If it makes you feel any better I had a cam chain failure on my '98Jaguar twin overhead cam engine a few months ago and it resulted in the same broken valve stem and a ventilated piston. The only difference is if it had been a Chevy I would have fixed it myself. The Jag had to be junked as the cost to fix was higer than the value of the whole stinking car.
P.S. - if any of you happen to own a late 90's early 2000's Jag and have not done the cam chain tensioner upgrades yet, send me a PM RIGHT AWAY.
-Mark.
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Coil bind: when for whatever reason the individual wires that makeup the spring coils touch, basically becoming solid.
Find out what cam was used (lift), installed height of the springs, valve to piston clearance, rocker ratio etc. The answer is there.
Find out what cam was used (lift), installed height of the springs, valve to piston clearance, rocker ratio etc. The answer is there.
Last edited by big_G; Jul 19, 2007 at 09:53 PM.
Thread Starter
Instructor
Joined: Dec 2004
Posts: 230
Likes: 6
From: Washington DC
Thread Starter
Instructor
Joined: Dec 2004
Posts: 230
Likes: 6
From: Washington DC
Yes No?
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
It would be easier. You have to look at all options.