Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 29-02-2020, 09:52   #16
Registered User

Join Date: Sep 2008
Location: Washington State, North Cascades
Boat: Valiant 40
Posts: 103
Re: Perkins 4-108 Rebuild Question

Thanks to all of you for your info on the rear crankshaft seal. It sounds like a job that I can handle. It will be nice to have dry diapers in the bilges!
__________________

bongo is offline   Reply With Quote
Old 29-02-2020, 10:23   #17
rbk
Registered User
 
rbk's Avatar

Join Date: Feb 2016
Location: Canada
Boat: T37
Posts: 1,862
Re: Perkins 4-108 Rebuild Question

Quote:
Originally Posted by bongo View Post
Thanks to all of you for your info on the rear crankshaft seal. It sounds like a job that I can handle. It will be nice to have dry diapers in the bilges!
Mark the orientation of your fly wheel when you pull it. It only goes back on one way and depending on the location in your boat it can be a pain re-aligning while being in a pretzel.
__________________

rbk is offline   Reply With Quote
Old 29-02-2020, 10:46   #18
Registered User

Join Date: Mar 2007
Location: Santa Cruz
Boat: Boatless Again
Posts: 4,869
Re: Perkins 4-108 Rebuild Question

For the OP, did you have any low oil pressure problems besides the oil leak? If not, the bearings are probably OK.

In my experience, the rear seal is not the only oil leak at the back of the engine. You will need to change out the old cork oil pan gasket as well.
donradcliffe is offline   Reply With Quote
Old 01-03-2020, 09:50   #19
Registered User

Join Date: Sep 2008
Location: Washington State, North Cascades
Boat: Valiant 40
Posts: 103
Re: Perkins 4-108 Rebuild Question

Thanks again for the input. Jpendoley, I sent you a pm asking for the copy of the relevant pages of the service manual, for the rear main seal. Thanks in advance!
bongo is offline   Reply With Quote
Old 05-03-2020, 11:15   #20
Registered User

Join Date: Mar 2007
Location: MA USA
Boat: Pearson 365
Posts: 150
Re: Perkins 4-108 Rebuild Question

Quote:
Originally Posted by Lepke View Post
I doubt the crank needs turning. I've mic'ed hundreds of diesel cranks and if no oil failure occurred they are usually close enough to original that standard bearings do the trick. If the crank is worn, then I have it hard chromed to spec. Then it never wears. Most diesel cranks have hardened journals. If turned, that's removed. Not all small crank turners know how to hard surface.

You should be able to mic ok.
Rear main usually leaks on a 4108 with the original rear seal. Old rope seal needed to be soaked in oil and lubed with grease before install. New ones no, but I grease them to prevent the crank from pulling the seal out of position on the first start. You can buy the new seal at parts4engines at about 1/3 of what Foley charges including shipping.
On ether, I've been using it for 60 years w/o problems. Don't use more than needed, don't run an engine on ether. You can use it every day w/o damage on a hard to start engine if you don't use too much.

You can change the sleeves yourself. I'd send the head out for a rebuild and either send out the injectors or buy new nozzles.
I have a 1972 - 4108 turning a 10kw at 1800. Only rebuilt once, by me. Now it's like new and still has a standard crank. My 1947 Detroits have original standard cranks.
Lepke-your post gave me courage, I learned how to pull liners- thank you. Maybe grew a few more gray hairs in the process...wound up running a very light weld bead up the liners to shrink them and they came out easily. No damage to the bore which measured close to the original spec-like within .0005 properly measured by a bore gauge.
Next question is about sleeves. Online I see lay people installing dry liners -and my originals are straight steel with no flange-but TAD told me the liners have to be bored after install. That seems odd as the originals were .0125 or so when installed new and they lasted 40 years. Thoughts from anyone who has lined a 4-108? Did you do it yourself or did you send it out? My machine shop is quoting 45 day turnaround and I will need to launched by then....
I'm trying to keep machine costs down and this might be a setback
jpendoley is offline   Reply With Quote
Old 05-03-2020, 11:32   #21
Senior Cruiser

Cruisers Forum Supporter

Join Date: May 2013
Location: Oregon to Alaska
Boat: Wheeler Shipyard 83' ex USCG
Posts: 2,821
Re: Perkins 4-108 Rebuild Question

For engines that don't come sleeved, rebuilding required boring the block and fitting a sleeve that usually has to be bored to a final size. The 4108s I've seen come with sleeves the proper size and honed with cross hatching and ready to install. The 4108 engine kit should come with sleeves with a proper bore. Mic them. I have a 1972 - 4108 on a 14kw generator I rebuilt a few years ago. Sleeves were standard and pre honed. The only fitting I had to do was minimal trimming the piston tops. The head I sent out. Depending on the kit you buy, they come with new valves, guides and seals that are sent with the head. Any auto machine should be able to do the head.
I had an old engine and an old kit. Newer engines kits may come with the piston tops the correct height. British machining got more precise over time.
Lepke is offline   Reply With Quote
Old 06-03-2020, 18:28   #22
Registered User

Join Date: Mar 2007
Location: MA USA
Boat: Pearson 365
Posts: 150
Re: Perkins 4-108 Rebuild Question

Thanks for that response Lepke. It has been interesting talking to parts suppliers and getting responses all over the map. Yesterday I spoke with a large very reputable Westerbeke/Perkins dealer who told me the notes have to be rebored and the liners bored. Parts4Engines which sells lots of 4-108 kits agreed. My local Napa disagrees and says they can source the correct sleeves that should need no boring. And this is boring not simply honing. Pretty big difference of opinion. For my money ( of which I have precious little), Im going with the Napa folks. These engines powered everything from industrial reefers to field tractors. Were not building a race car. I like the 4-108 for its virtues: simplicity, rebuild ability and ubiquity. I will let the forum know how it all turns out.
Thanks again for the insight to j hi ou and everyone else who contributed suggestions.
Jim
__________________

jpendoley is offline   Reply With Quote
Reply

Tags
perkins, rebuild

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Perkins 4.108 - Rebuild or Replace? gandalf Engines and Propulsion Systems 36 10-11-2015 15:43
Perkins 4.108 Rebuild? sapadeni Engines and Propulsion Systems 67 14-12-2012 13:16
Perkins 4.108 Rebuild Now No Instruments ? Sailingdiver Engines and Propulsion Systems 7 21-11-2012 05:16
Injector Pump Rebuild or Service Perkins 4-108 S/V_Surya Engines and Propulsion Systems 2 29-08-2011 13:02
Perkins 4-108 Rebuild Questions bobfnbw Engines and Propulsion Systems 20 06-08-2009 10:16

Advertise Here


All times are GMT -7. The time now is 08:33.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.