I pulled out of a gas station and into a construction zone, creeping along in first gear when there was about 1 second of horible noise and the engine stopped. I was able to coast partially into a blocked off lane and pushed it the rest of the way. This HAD been such a sweet engine that I never even considered that the problem might be internal and I tried to crank it (after lots of cranking I even had it running for another second, again with lots of terminal noise). I pulled the plugs to be able to turn the engine over by hand and the #3 plug would not come out - anti-seize does not do much good when the end of the plug has been mushroomed by valve parts. Even after the final plug was pulled, I had a hard time turning the engine over with a 15 inch long breaker bar. I pulled the cam cover off and found a loose and broken valve spring and the valve guide also loose and broken in half.

I could not figure out how this could happen until I showed the broken parts to my wife and suddenly it all came to me - the valve spring must have broken. With a broken spring the valve keepers loose their tension and the valve drops down. I have to presume that on the first drop the valve was not completely free of the head when the piston pushed it back up and the valve became the drift that pushed the guide up into the top of the head.

I did not have time to pull the head last night but looking into the bore I see gouges scraped in the bore. I suspect the block is toast w/o boring oversize. I have not begun to look around for replacement engines. This engine had about 120K miles on it and was not even burning a qt of oil in 3K miles.

This was a 2.3L. Anyone else ever have a valve spring break? I know that race engines frequently "swallow valves" but this is a low reving motor - I rarely go past 4K rpm. So one question is should I just get a 2.6 long block (instead of replacing the 2.3) or consider getting a used 2.8/3.4 V6 driveline & engine mgmt out of a similar age Trooper? Any ideas as to the cost of a 2.6 long block?

I just had a thought as I was previewing my post - I did swap in a Delta cam about 60K miles ago - wonder if the slightly greater valve lift did my valve spring in?

Off to start searching for engines, parts car, ....

Follow-up after I pulled the head. After about 120K miles the bores STILL had the cross hatch marks from the machining of the block - this could have been a 200 to 250K mile motor!

Engine bore is much better than expected - a few shallow gouges about .005 deep.

Piston is toast: cracked, perforated by the valve on edge and generally abused.

Head is toast: valve head (stem broken off and who knows where) is imbedded in the head.

I took some quick pictures but am uncertain how to upload them without first posting them to a picture hosting site and linking them here.

Now I have to decide on if I want to do a quick and dirty repair - trying to get another 50K out of the existing motor or upgrade to a 2.6L. Is there a signigant performance difference between the 2.3 & the 2.6?

Picture of the head with the repositioned intake valve: http://i290.photobucket.com/albums/ll272/aribert/Isuzu/PB280018.jpg

Picture of the ventilated piston: http://i290.photobucket.com/albums/ll272/aribert/Isuzu/PB280023.jpg

ANyone outthere with 50K or more miles on a Delta cam (and valve springs)?

Anyone familiar w/ Clearwater heads, (their head is about $125 less than an AMC head)?

Man that sucks!! What a horrible thing to have happen! I hope you get everything fixed up. Sorry I don't know much about the 4 cylinder engines so I can't help you out much but give you my sympathy!

I dont know anything about isuzu 4cyl engines, but do they only have 1 spring per valve? My '72 yota started breaking valve springs around 230k miles but they have a smaller inner spring. Still made lots of noise but kept the spring keepers in place so it never dropped a valve. If the stock heads only have one spring you might check to see if any of the head remans add a 2nd spring.