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We regularly get emails coming in from people saying the’ve overhauled their engine but it still doesn’t start or run very well.
When we dig a little deeper we begin to find out why.
It always amazes us how many people go to all the time and effort of of dismantling an engine and then only do half a job of refurbishing it.
Just Buying An Engine Kit Won’t Cut The Mustard
All too often people buy an engine kit and fit it, but fail to do a decent job of the valves or the head. Or worse still they replace the piston rings, think that the pistons themselves are OK, maybe just use a honing tool on the cylinder liners because, well, they don’t look all so bad do they?
Worn liner
I know we don’t like to spend our hard earned cash unneccesarily and replace parts that are serviceable. However, if the rings are worn, so usually are the pistons they run on and the liners they run in.
Skimmed block with new liners fitted. Note the cross hatch hone marks clearly visible.
Every so often engines develop a broken piston ring for no apparent reason, when everything else is in good condition, so that may be an exception. But wait, are you really sure that broken ring was a one off or did something else cause it. Occasionally things do break for no apparent reason, but more often there is a cause.
We Didn’t Bother To Re-Gring The Crankshaft
“It didn’t seem all that bad. There were a few rough spots on it but I didn’t have a micrometer to measure it, thought it would be OK.”
Vintage Tractor Engineer’s blood is now reaching boiling point.
Grinding of the crankshaft is a specialist job
Valve Seats. I Used Some Paste And Sand Paper
Is rubbing the valve seats with a bit of paper really going to create a sufficiently good sealing surface? OK, so yes, it will improve them. Re-cutting will be a much better job with new valves and guides. Sometimes a new valve seat needs to be pressed in and then cut if the old seat is too worn.
Worn valve seats
The Head Gasket Failed And The Engine Boiled
“I replaced the head gasket. It went OK for a while, then it started to leak again. I’ve got to replace the gasket again now.”
Maybe you should have realised the head may have warped or cracked. As a minimum it needs pressure testing, probably skimming.
“It was cheaper to buy a new cylinder head than have the old one serviced”.
That should tell you something about the quality of this new head. If it’s cheap then it’s probably rubbish. VTE would recommend having your old one skimmed in preference to one of these cheap heads. If your existing head is beyond repair consider getting a second hand head and having it serviced.
What Else?
- Was the camshaft OK?
- Timing gears or chain condition
- Injectors
- Injector pump
- Cleanliness is king
There’s obviously a lot more to it than this, but the point of this article is that you need attention to detail. Stripping and rebuilding an engine can take 2-3 days, so a few extra pounds spent on the job will often be well worth it.
