ianj99
Well-Known Member
I'm told the head on the 4108 is prone to cracking. Has anyone had this happen or is it another myth?
Perkins 4108 cylinder head cracking
- Thread starter ianj99
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Seanick
Well-Known Member
It is prone to cracking between the valve seats if worked really hard. Apparently this used to happen when the engine was in vehicles, but most marine engines get an easy life. If yours is in a planing hull and rated at 55HP, and you thrash it, you may be at risk.
I used to run two 4107's, and still have two spare heads! Be nice to it untill its warm, and you should be ok.
I used to run two 4107's, and still have two spare heads! Be nice to it untill its warm, and you should be ok.
ianj99
Well-Known Member
Thanks for that. The engine is in my recently acquired 36' ketch and hasn't apparently been worked hard.
It suffered a hyraulic lock as soon as I cranked it over a couple of weeks ago after refitting overhauled injectors and pump.
Cylinder 4 was full of mayonaise which as ejected when I slackened injector 4 off (the combustion chamber was dry when I first fitted the injector so I assume the piston stopped well down the bore)
With the head off I found a bit in cyl 3 as well.
I suspect it was a leak from the 33year old Perkins exhaust water cooled manifold. The head looks okay, valve guides aren't worn and the bores show negligible wear. I hope to have it pressure tested and have a Bowman combined heat exchanger/ manifold/header tank to fit.
PCUK
Well-Known Member
If you don't need full power you would probably not notice the difference with a cracked head. I had two 4107s and both cracked the heads within a week of each other. Each engine lost about 250 RPM but other than that they carried on regardless. When a crankshaft broke a few months later it had to be replaced as it refused to run with it in bits! The new crank broke a week later and I was then told that it is ESSENTIAL to have a case hardened crank. After that, no further crank problems.
The perforated cylinder liners were another problem (although you won't get that on a 4108 as you have dry liners).
Treat it kindly and it will be OK for years, there are thousands of them about and my problems were slightly unusual.
The perforated cylinder liners were another problem (although you won't get that on a 4108 as you have dry liners).
Treat it kindly and it will be OK for years, there are thousands of them about and my problems were slightly unusual.
