87 350 hole in piston #4

[gw11]

I had a remanufactured 350 engine installed, have less than 50 hrs on motor, #4 piston has hole melted into it, the size of quarter and is shining. all the rest look good except for carbon billed up. Do not wish to take back to Marine Mechanic, this was the trird time he installed the engine, fist time oil filter came off, rebuilt it. next time glogged ports from Silicone, no oil to rockers, rebulit it and know hole in piston, after less than fifty hours. Know I.am going to have engine manufactrue send me a new piston and new set of rings. I will install new cap, points, and wires, and rebuild carb, Is it posiable that the wrong cap was used, or is 350 pretty standered, how can I find out what caused this so it wont happen again. The motor did seam to run good until the hole in piston, I did not notice any pinging or miss firing, it seamed to be running great.

 

[Howard Sterndrive]

Re: 87 350 hole in piston #4

Is it posiable that the wrong cap was used,

judging by the workmanship of your mechanic, I'd say anything is possible.

But a mismatched distributor cap isn't a common cause of holes in 1 piston... can't imagine it would run well enough, long enough... is there a specific reason why you are focusing on the cap?
If you are going to rebuild it again, use a fine tooth comb - leave no stone unturned. Take it apart carefully - I'd check valve (rocker) adjustments and cam timing, valve seats... everything around that cylinder especially.
Timing advance should be verified. Firing order even, getting back to the cap.

Personally, I'd be thinking about just putting in a new crate or rebuilt long block. I tend to like the 350/290HP GM crate option even though marine use deletes the GM warranty... and you still need to verify that you aren't carrying any carb/intake related issues forward and that your distributor is healthy and advancing.... but a new Delco Voyager system would go nicely with the new long block.

 

[bruceb58]

Re: 87 350 hole in piston #4

How did you set the timing? Verify proper total advance? Stock marine distributor?

What condition was the carb, filters and fuel pump?

 

[proshadetree]

Re: 87 350 hole in piston #4

If it is on one cylinder I would suspect a vacuum leak.

 

[bruceb58]

Re: 87 350 hole in piston #4

If it is on one cylinder I would suspect a vacuum leak.

Yes...actually a very good possibility.

You have pictures of all the spark plugs handy?

 

[gw11]

Re: 87 350 hole in piston #4

How did you set the timing? Verify proper total advance? Stock marine distributor?

What condition was the carb, filters and fuel pump?

I had the engine installed by a Marine Mechanic he did the timing , figured he knew what he was doing, the carb is in fair condition , but having ig rebuilt, distributor is stock in the Mechanic used my distrbutor when he but it back in , hard to say what he did at this point no longer dealing with him. going to distributor checked out on a distributor machine. is there away to find out if I have the right distributor

 

[gw11]

Re: 87 350 hole in piston #4

Dont have all the plugs at this time, put they all looked good except for carbon build up, #4 looked clean and as if somthining hit it