An engine repair question to the mechanics out there

[dbenamati]

I posted last week about a screw from my carb. falling in to my intake manafold and doing some damage. The screw was removed after taking my manafold off and I thought It didn't do too much damage. I was wrong. A friend stopped by to tighten and adjust valve/springs and push rods. It's not making a sloppy noise anymore but he showed me with out the vacuum gauge that my #6 has no compression (it's a 250 strait 6 cyl.) by taking off the plug wires from distributior while running. I am no mechanic and my friend does more than me but general repairs and not rebuilds. From the looks of things it is probably a bad valve or crack in the piston head to have low compression. I know the head will need pulled to find out but by doing that, what am I looking at cost wise to have that repaired? What kind of project would that turn into, have a major rebuild or just repair what's broken? My friend said he had no idea but thinks I may as well just scrap the motor. I don't know about that because first I don't have that kind of money and I kind of like my little 250-I6 and it is Original motor with 80k on it. Anyone understand where I'm comming from?

Thanks, Dave

[bigjimzlll]

with the valve cover off(its going to be messy) start the engine...watch the valves on #6...how big was the screw you dropped in there? Did you recover it from above the cylinder? if so..its not a piston. You might of bent a valve..which might have bent a pushrod..which could damage the cam. You might have pulled a rocker stud..If the cam is still good, you are probably just looking at pulling the head, and repairing the damaged valve(s) and maybe the seat.....anyways..check to see that the offending valve(s) are going up and down the same as the others. Have you pulled the spark plug from #6? Can you do a comression test? The damage is usually not as bad as our imagination.(most of the time..lol)

[dbenamati]

The screw was very small, one of the screws that holds my choke conversion kit to the carb. When I pulled the manafold, It was at the edge of the #6 intake so it got sucked in and kicked back out quick only a second or two until I shut it down. Originally I thought not too much damage but everyone else is gloom and doom saying that is all it takes (Piston/valve moves hundreds of times in that period). Anyway, had the cover off and checked the push rods, they all seem tobe strait so thats why I think it is a valve or piston. It is when I put things back together and took the truck down the road that I notice things are not right. It puts when the oil pressure goes up. Even with it being a valve, that guy told me the head will have to be pulled and machined which will be big bucks. Two things I will do this weekend is find a compression check gauge and even try a new plug/wire. You never know right? Either way, If I were to take it to a garage to have this done at $70/hr., it will cost something. I am just looking for a fix under a few hundred dollars.

[bigjimzlll]

I just broke a piston and ring on my 350.. http://67-72chevytrucks.com/vboard/s...threadid=56354
there were no pieces left in the cylinder and NO damage to the valves or cylinder) I knew I broke a piston(because of a ton of blow by) I doubt that you hurt the piston..you would have to by very very unlucky to have. You probably chipped the valve, at worst. I would look at the rocker stud, rocker arm,lifter. First check the plug...I am sure it is fouled. Your friend who adjusted the valves might have tightend it too much, this would give you the bad compression readings...if he only used a vacuum gauge, a bad plug would give the same reading....good luck and keep us posted

[4t5acp]

If it was a damaged piston/cyl wall then you would probably be able to hear the previously mentioned blow-by (compression) through the oil filler hole. If its only a bent valve and you have basic skills and a good manual the repair shouldn't cost too much. You'd be looking at 1 or 2 valves, head gasket set, maybe a rocker stud and re grinding the 2 seats, oil change and some antifreeze should get you back on the road for a couple hundred.

[Eddie H.]

It is also possible that your friend may have over-tightened one of the valves on the #6 cylinder. This would not allow the valve to close completely and cause a loss of compression. I don't think the piston would have been damaged seriously by a small screw.
My guess would be at worst, just a valve.

The inline 6 engines are probably the easiest engine to work on that has ever been built. Get a shop manual, remove the head and take it to the local machine shop to grind the valves, and re-install it yourself. You'll get out cheap and learn something in the process.

[lukecp]

If it turns out the damage is excessive, instead of spending gobs of money getting parts of your 250 machined back to new, i would just go the the salvage yard and pick up another 250, or even a V8 if you wanted to swap one in. 250's are usually swapped out for a SB V8, so finding a good running motor should be pretty easy, and will be inexpensive. Swapping motors isn't very hard either. As long as you have some hand tools and a engine crane (which can be rented), you will be just fine, and can proably do the whole swap in one day.

Good luck!