Perkins 4108 cylinder bore tolerance

pcatterall said:
The bores on my 4108 look good and measure just about 3 to 5thou above spec (3.125) Is there a rule of thumb about what to expect and when it is time to replace anything?
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This is a copy of the workshop manual for the perkins 499 4107 and 4108.

http://www.fujiyachts.net/manuals/Perkins 4108 Workshop Manual.pdf

or this one

http://www.atlantisbolivia.org/p1983uk.pdf This one looks like the oficial Perkins manual

service wear limits are on page 11 in the first manual
 
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Roger many thanks! 6 thou !! I will check all mine again more rigorously Clearly at 5thou I would be advised to get them done now that the engine is on my bench and not on the boat!!

I need to check my manual as I could not find that service wear section ………..back to specsavers I guess.

Thanks again
 
Any time

I have an old stripped Perkins 4/108 in my Garage that I part exchanged for one I got put of a road washer sweeper but never got round to rebuild.
 
pcatterall said:
The bores on my 4108 look good and measure just about 3 to 5thou above spec (3.125) Is there a rule of thumb about what to expect and when it is time to replace anything?
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When you find out the price of a set of o/s pistons and a rebore you may re-think that decision. Question is, how long has it taken to wear 3-5 thou? Ok it is bordering on the tolerance but could outlive your ownership with a set of rings and a glaze bust. If it aint bust, don't fix it.
 
Rebuild kits including liners, pistons, bearings and gaskets will set you back £375.

But you do need a engineering workshop to size the liners and then top the pistons which is a lot of faff. If there isn't a really discernible ridge around the top of the bore, no obvious corrosion issue along the top of the liners, I would leave them alone.

But do remember to crack test between the pairs of valves on the cyclinder head.
 
third engines said:
When you find out the price of a set of o/s pistons and a rebore you may re-think that decision. Question is, how long has it taken to wear 3-5 thou? Ok it is bordering on the tolerance but could outlive your ownership with a set of rings and a glaze bust. If it aint bust, don't fix it.
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On this thread http://www.ybw.com/forums/showthrea...-what-does-that-achieve&p=6479239#post6479239

You said
This thread just about sums up the engineering knowledge on here. Nixt, zilch, none, aucun. And the shameful part is that you all purport to advise on subjects to novices.
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Hmmmmmmm

In response to your post here, i would say "This post just about sums up the engine knowledge here. Nixt, zilch, none, aucun. And the shameful part is that you purport to advise on subjects to novices."

:):):)
 
Thanks, yes, current estimate was £50 to fit, bore and hone the liners but no price for piston topping yet.

Just what is the crack test on the head? I understand that there are sometimes problems with cracks between the middle valves.
There are no visible cracks and the head is in tolerance regarding bow.
 
pcatterall said:
. . . Just what is the crack test on the head? I understand that there are sometimes problems with cracks between the middle valves.
There are no visible cracks and the head is in tolerance regarding bow.
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That's right, cracking between the middle valves is fairly common. If the crack is well established it will be obvious as water will have leaked, but very early onset can be detected by a generic dye / penetration test before it's visible to my (rapidly ageing) eyes. A simple thing to do when you've got it in bits.

There is conflicting views on skimming the cylinder head face. Perkins says don't, some engine overhaulers do it. I would check for flatness and if at all possible, leave alone.
 
skipper_stu said:
Indeed! https://www.parts4engines.com/perkins-4-108-overhaul-kit/
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I somehow expected better from you.

Le us look at the deal. They supply in the kit amongst other things,

Liners 4 off
Pistons 4 off
BE bearings 1 set
M bearings 1 set
Head gasket set 1
Conversion set 1
Gudgeon pins 4 off
Set of rings 1
Small end bearings 1 set

Just a sample of the whole kit contains 18 items. All for the price of £375. That equates to an average price of £21 per.

Caveat emptor
 
One reason for retaining the Perkins was the availability of cheap spare parts. The £375 kit and the head kit (c £80) are pretty comprehensive.
My mechanic chum who was brought up on similar engines showed me the dye test for cracks. He also showed me that as well as measuring the
bores for wear that a finger nail check for a ridge on the 'wearing' side of the bore was also a fair first check.
He pronounced the head and the bores fit to continue after some cleaning and valve lapping.
Thanks for all the advice.
 
pcatterall said:
One reason for retaining the Perkins was the availability of cheap spare parts. The £375 kit and the head kit (c £80) are pretty comprehensive.
My mechanic chum who was brought up on similar engines showed me the dye test for cracks. He also showed me that as well as measuring the
bores for wear that a finger nail check for a ridge on the 'wearing' side of the bore was also a fair first check.
He pronounced the head and the bores fit to continue after some cleaning and valve lapping.
Thanks for all the advice.
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Now, that chap knows what he is about. Valuable chap.
 
third engines said:
I somehow expected better from you.

Le us look at the deal. They supply in the kit amongst other things,

Liners 4 off
Pistons 4 off
BE bearings 1 set
M bearings 1 set
Head gasket set 1
Conversion set 1
Gudgeon pins 4 off
Set of rings 1
Small end bearings 1 set

Just a sample of the whole kit contains 18 items. All for the price of £375. That equates to an average price of £21 per.

Caveat emptor
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I dunno what planet you live on but that kit is a deal!
Having rebuilt a few different engines in my time I have a good idea of what parts cost! My previous MD2030, before parts4 came along, a VP headgasket cost me nearly £90. Rebuilding a Cat 3306, the engine gasket kit runs in to the thousands, so do I think that genuine Perkins kit for £375 is expensive? No! As for Petes engine, the thumbnail test is a good indicator BUT if he hones it, another thou or so off the bore? He will probably get away with a set of rings the same as I did. But the option is there to do a reasonable priced overhaul if he so wishes.
 
skipper_stu said:
I dunno what planet you live on but that kit is a deal!
Having rebuilt a few different engines in my time I have a good idea of what parts cost! My previous MD2030, before parts4 came along, a VP headgasket cost me nearly £90. Rebuilding a Cat 3306, the engine gasket kit runs in to the thousands, so do I think that genuine Perkins kit for £375 is expensive? No! As for Petes engine, the thumbnail test is a good indicator BUT if he hones it, another thou or so off the bore? He will probably get away with a set of rings the same as I did. But the option is there to do a reasonable priced overhaul if he so wishes.
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£375 for that lot for genuine parts for a marine engine? I suspect that they have accidentally left the 1 off the start of the price. :ambivalence:

Richard
 
RichardS said:
£375 for that lot for genuine parts for a marine engine? I suspect that they have accidentally left the 1 off the start of the price. :ambivalence:

Richard
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They are ubiquitous in the world of the utility engine, common as muck and everywhere, hence lots of spare parts at low cost.
 
third engines said:
I somehow expected better from you.

Le us look at the deal. They supply in the kit amongst other things,

Liners 4 off
Pistons 4 off
BE bearings 1 set
M bearings 1 set
Head gasket set 1
Conversion set 1
Gudgeon pins 4 off
Set of rings 1
Small end bearings 1 set

Just a sample of the whole kit contains 18 items. All for the price of £375. That equates to an average price of £21 per.

Caveat emptor
Click to expand...

A couple of posts ago you were discussing a re-bore and over sized pistons. Who ever heard of re-boring a 4108 :ambivalence::confused:
 
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