Engine rebuild lasted 400 miles :(

[grant12]

Hello guys, i posted up before about a problem with the oil pump packing up, starving the crank and smashing the bearings, the crank was sent to a machine shop with a reputation for beeing good, and told me they can regrind the crank with maching race bearings. this was done, new oil pump, new gaskets, everthing in the engine was taken out and cleaned before getting put back together. I must also point out all parts were tourqued to Honda's specification. engine went back in with the new crank and bearings started up fine, ran brillient until the other day driving to work (carefully as i have since the rebuild) and it started knocking quietly, i was about half a mile from my work so carried on, by the time i got to work the knocking was LOUD and knocking with the engine revs, until i parked and the car cut out. now there is nothing, it wont even try to turn over, try bump it off it locks both wheels. I think personally its the crank again but my friend is claiming a goujion pin? any constructive advice is welcome!

Thanks

Grant,

 

[Hazz]

Gudgeon pin is the pin which attaches the piston to the con-rod. Highly unlikely if they didn't come appart during re-furb (they generally don't).

It will be shells, probably big ends if it's knocking with the revs although it could well be mains. A high proportion of engine running in issues are down to poor clenliness when assembling the engine.

In my opinion, the only way to ensure an engine is right is to measure every part yourself and inspect it at every assembly stage. There is basically no way of tracing the problem back to the cause now... unless it's a obvious great lump of something embedded into a shell bearing. You'll have a very hard time pinning the blame on anyone now mate, sorry to tell you.

 

[grant12]

Much apritated, like i say the cranks just been ground though, and all new bearings. could it be down to bad machine work?

 

[Griffin]

I'm in with the gudgeon pin theory. For the knocking to suddenly start quietly and start to louden over such a short period is where the pin has rattled from the piston causing a light knock then perhaps come free from one side of the piston causing a heavy knock to occur on every stroke or... the looseness of the rattling gudgeon pin has caused itself to become dis formed due to combustion cycle. The engine then seizes as the pin eats its way into the cylinder wall or bends a Conrod pitching the piston in the cylinder. I would expect the big ends, if deteriorating that fast to explode father than seize

 

[Hazz]

That does make sense Griff. I just don't understand why a rod would be separated from a piston during a re-furb.... unless you'd melted your pistons or crashed them into valves I suppose. You said yours was an oil pump fail... so I guess from a re-furb point of view, that'd be new cylinder liners, piston rings, crank re-grind & new shells and you're good to go. Pistons should not have left rods IMO.

Yes, it could be from bad machine work. You will not be able to tell now though, you have to inspect these things before they are fitted. I was convinced minisport didn't grind my crank propperly the first time round but I couldn't prove it. 2nd time round I went to MED engineering and measured it with a ballend micrometer on each journal in 4 positions. Still didn't work, turned out it was my shoddy engine building skills in the end :lol: but I still think my crank wasn't right the 1st time round.

 

[Griffin]

Perhaps a bad machining on the crank has affected the top ends, being offset by a few thou would have an affect on both ends. But then again if the crank was offset, all pistons would be affected.

 

[Hazz]

The float on the pin should take up that though, it'd have to be some serious offset. I guess you'd see some
bad damage on one side of the little end and inside the piston?

It could be worth getting some kind of certified engine builder to take it apart and photograph/document it at each stage. That way if there is any blame to be placed you might have a chance in court. You never know, they might know they've done a botch and just give you your money back.

 

[m1ke]

I reckon it's still the crank, does sound like the engine is seized now though which is odd.

I wouldn't have thought whomever re built the engine would have touched the piston/conrod.

 

[rf55]

Seized on crank, did you check the valve in the oil pump when rebuilding? they can stick open, which gives it low oil pressure? then big end starts to knock.

 

[Griffin]

The float on the pin should take up that though, it'd have to be some serious offset. I guess you'd see some
bad damage on one side of the little end and inside the piston?

Aye, if the offset was that bad you would have felt it as it was assembled.

As you say in a prior post the lack of oil from the previous problem may have affected the small or big ends causing them to fail.