Perkins 4.108 - Rebuild or ???

[sailr69]

If the inside is anything like the outside, what are you doing?? send the engine to Atlantic diesel for a complete rebuild by the pros.

[sailr69]

Originally Posted by 1affiah

I would look long and hard at all Perkins parts sources before buying anything from Foley. Google them for some interesting reading.

Yes, Foley does not have a good recommendation , go to Atlantic marine , a true Perkins rebuild service. the word from Perkins rep. I can witness.

[btompkins]

Thanks, everyone for all the help here! This forum is awesome.

I've got the head off and here's what the cylinders look like. To me this looks more like carbon buildup, does it make sense to completely rebuild here, or is there an option of just cleaning up and re-sealing and focus on the accessories, atomizers, etc.

Thanks again for all the help here. Still concerned a bit about the unknowns this being a generator engine. Going to look into the valve springs and injection pump questions.

[Tillikum]

If you don't have the repair manuals, buy them before going further.

You'll need a suitable inside micrometer to measure the cylinder bores, not to mention outside mics to measure the pistons etc. etc.

You'll also need a piston ring compressor to get the pistons back in the bores.

Be sure to record the alignment and layout of all the parts and lay everything out carefully on a flat surface.

Label all the fastenings or put them back in their original holes etc.

You can either bring a pro and the tools to your block, or take your block to him, or buy/rent the tools and do it yourself with the aid of the manuals.

Sort of like folding and packing your own parachute: screw up and the trip may be shorter than expected.

[jpendoley]

Listen carefully to what Tillikum said. Get the manual, mike the bores, mike the crank (they usually are hardened and show no wear). The manual will tell you how much wear is acceptable before replacement. The head should not be planed if at all possible. If the cylinders or oval rather than round (check the manual for whats acceptable) have a machine shop press the sleeves out and put in new ones. Parts4engines is dirt cheap and ships lightening fast, TAD is a bit more expensive but great service.
I'm an english major-never rebuillt a diesel before my 4-108 and am completely satisfied with the result. My engine leaks no oil and my exhaust is clear-lots more power too. Total rebiuld cost under 4 K with an upgraded serpentine kit. 15K less than a BETA 50-thats not chump change-use the savings for a new fuel tank if yours is old.. And I can fix the engine if and when anything goes sideways.

[malbert73]

Originally Posted by jpendoley

Listen carefully to what Tillikum said. Get the manual, mike the bores, mike the crank (they usually are hardened and show no wear). The manual will tell you how much wear is acceptable before replacement. The head should not be planed if at all possible. If the cylinders or oval rather than round (check the manual for whats acceptable) have a machine shop press the sleeves out and put in new ones. Parts4engines is dirt cheap and ships lightening fast, TAD is a bit more expensive but great service.
I'm an english major-never rebuillt a diesel before my 4-108 and am completely satisfied with the result. My engine leaks no oil and my exhaust is clear-lots more power too. Total rebiuld cost under 4 K with an upgraded serpentine kit. 15K less than a BETA 50-thats not chump change-use the savings for a new fuel tank if yours is old.. And I can fix the engine if and when anything goes sideways.

Sounds awesome! Nice work.
Just correcting numbers- a Beta 50 is total around 15K and a 43 which still likely has more power than the 4-108 at lower RPMs where you actually run it is maybe 1K cheaper. Just correcting marginal numbers. If you were to hire someone to remove, rebuild, and replace the difference would be less. Still not a small amount and a 4-108 as many have said is often worth rebuilding

[alaskanviking]

With regards to rebuilding marine engines... There is some truth to repowering a short time after a rebuild, and that there is often issues as 30-40 year reused old parts continue to break down. It is also true that land based engines are regularly and reliably rebuilt.

The difference is how they are rebuilt. This applies to all engine makes, but specifically Perkins and older engines that don't nessesarily have easy access to new parts. The difference is simply that land based engines typically replace more parts, and those that remain are refurbished better.

As an example, connecting rod bolts are typically replaced, as they stretch. It's normal to sent them off to a machine shop or specialty shop to press new upper bearing into the connecting rod and machine everything back to spec, or an oversized with appropriate bearing. New rod bolts are installed, they use Shotpeen, hardening and other processes for strength.

I don't see this done typically with Perkins 4-108, and many other marine engines. Normally a put in new bearings and check measurements kind of a deal. Reuse everything that isn't in danger of rusting away. Combine that with the normal neglect that comes with boat engine installs, specifically sail boat engines, and of course some age issues. Shouldn't be a surprise when things fail. When I look at the Perkins engine facebook group I've noticed it seems there is a trend with rods going bad or losing compression after a rebuild. My theory it's due to reusing old connecting rod bolts, and heat bolts ect. Reused bearings like in the injection pump cam shaft ect, as these aren't as easy to replace. Most Perkins 4-108 rebuilds only replace the parts that come with a rebuild kit.

Land based engines they have more time to do a rebuild, they put more hours on the engines while operating on a regular basis, requiring more frequent rebuilds. They sometimes use special oil filters or run at lower rpm to extend life. there tends to be a larger market for new parts,so they are cheaper and easier to get. Some engine types swap in new performance or aftermarket parts. This all means they go through and replace more parts or more completely refurbish parts than is done with marine engines. Perkins 4-108 is a common generator, refrigerant, or equipment engine. It's in forklifts, bobcats, and tractors. You can get parts if you learn where to look.

So moral of this story is you can rebuild ( I swear it's not too difficult). But if you do or have it done make sure it's done right. Don't do the minimum and just throw in a rebuild kit. Also replace bolts and studs with ARP high strength types.

[alaskanviking]

Also much to be said with swapping in a beta engine. There is another brand that uses the same kubuta blocks but adds a turbocharger. Beta went out of their way to make things easy to do maintenance.

With Perkins, kubuta and other tractor engines you can "turn up" the injection pump for a little boost also.

[Tillikum]

Listen carefully to what Alaskan Viking said.

Now I've got a question for you A.V.: is there a relationship between the often "stop & go" useage of marine engines and this connecting rod distortion, and does the often greater and varied loading of marine engines play a part in that, compared to land-use engines?

Are these rods in fact not sufficiently strong for the marine application or is maintenance and/or usege causing the problems? Or perhaps QC failures?

While you're here, if you feel like offering some tips on small marine diesel "preservation" that would probably be of benefit to many?

Based on the failures you see and the causes found on tear-down.

[alaskanviking]

There is no real relationship with a stop and go operations. Depends on the boat really.

Powerboat engines are more akin to generator engines. Get to operating speed and stay at a relatively constant rpm. More performance oriented but similar

Sailboat engines have more issue with a slow rpms. Cruising at 2000ish, maybe 2500. We use them with low loads to power the alternator to charge batteries ect. These situations lead to carbon buildup. Turbo engines get coked up. Low usage means the heat exchangers and coolers get scummed up like cholesterol in an artery. Slowly lose cooling ability. Even more difficult on some boats with tight spaces.

To make engines last, Better to get a generator even a little honda 2000 to charge batteries. Put more load on the engine when you do run it. Increase turbo, exchanger, cooler maintenance/cleaning. Get religious in engine zinks if you have them. when not using the boat for a while Flush the salt water out with fresh. Better yet install a recirc loop in your salt water system, flush it with salt away or acid and water maybe once a year. Fuel cleanliness is a good thing, polish tanks, clean your lines. Old boats and engines used copper fuel lines, copper oxidises/reacts with diesel over time, makes a black scum that can clog stuff. Fuel nowadays isn't the same as when the boat was new it's more acidic, can contain biodiesel (a solvent), doesn't have the same lubricating properties it once did. Means your injector pump is going to need servicing at some point. You can get a fleetguard lubricity filter at the engine to help with this. Also take a page from the diesel truck world and look into airdog or similar system that takes air out of the fuel. The oxygen and copper fuel lines also react together with the fuel, but I've seen an engine run smoother. Get your service manual and compare to a newer engine manual like cummins see what's different in the maintenance and schedule. There is a lot they have learned since they designed some of our engines

We use cummins bta and qsb engines with her drives at work. Hot weather with constant operations really impacts the cooling ability over time. Lots of idling 1500-2500 and the engines get a lot of carbon buildup, turbos have to be replaced regularly as they coke up. Poor maintenance schedules and engines really start having issues around 3000-5000 hours or so.

[alaskanviking]

The rods are strong enough as originally installed. Problem is the older designs and metalergy. Perkins are tractor engines so they're built of cast iron, heavier duty in some ways. 1950's design. Cast iron block and head are pretty solid.

Rods bolts specifically are old metalergy and stretch over time. When you reuse them you stretch them further when you torque them, and weaken the metal. Add to that a fresh rebuilt engine with restored performance so more pressure on the combustion chamber and more vigor in the strokes adding stress. This is when rods fail. Arp studs are 260000psi tensile strength, far beyond stock Perkins. With large marine engines, industrial engines and generators they refurbish with new studs, and press in new upper bearings at a minimum. Truck diesels the measure length and replace if out of tolerance. Built performance engines just replace these parts to eliminate weak points.

Overheating is also pretty painful on these old metal bolts and studs.

Modern engines use torque to yield bolts and studs. You have to replace them. Arp studs have such a high tensile strength they don't really stretch.

I'm not 100% on Perkins failures due to rods. Just a running theory seeing the number of bad rod stories you see in forums and other places. They didn't keep that kind of data back then, and best info and collaboration now is forums and the Google group. I have noticed similar corelations with other older marine engines however.

Simple fix is just replace with new. Arp isn't much more expensive, but you do have to figure out the measurements and thread of the old bolts and call them to order. Also look at the diesel truck builds and compare what they replace or refurbish. People don't generally like blowing the engine on a 70k duramax or ram, thier operation is different but what they choose to strengthen is good insight.

[Tillikum]

Excellent, thank you. Worthy of close study. How much of an issue is glazing of cylinder bores due to running with inadequate load?

[alaskanviking]

We work on cummins, older boats have bta 6cyl 350hp. Newer engines have QSB 5.9 400+. The boats have been getting refurbished and switching out the old engines. Recent revisions are putting in the 6.7 Liters. These are connected to jet drives so they need high horse power.

However, these are are at full load maybe 10-20% if the time, during longer passages. Majority of the time they're idling on location with no or low load. I seen engine hours of 2000-5000 before replacement

Problems are more with turbo coking from low load on the engine, or overheating due to hot raw water and marine growth reducing cooling capacity. Lot of fuel cooler, fuel lift pump raw water impeller, and water pump issues. Cummins upgraded its Fuel cooler design and it's not supposed to fail much.

I don't think I've ever seen cylinder glazing or such. Older BTA engines were mechanical, more similar to the Perkins. In addition to the above, I saw a lot of cooling hose issues, belts, and people standing on the coolant expansion tank breaking stuff. More overheating issues. I don't think they lasted as long hours wise because thier power band was maxed out for what you used them for.

[alaskanviking]

Sail boat engines and the military patrol boat cummins have a very similar usage. Lots of low load and idling with shorter periods of peak use.

Overheating was probably the most regular issue I see. Even the cummins bta 5.9 is a more modern design with modern metals and materials. It takes several overheat incidents before the engine degrades and we start to see consequential issues with other parts.

Perkins have decent blocks but was but the older design work didn't have access to modern metalergy. More cast parts. Overheating this stuff has much more immediate consequences.

While we aren't generally running around in water above 100°, we still should be much more religious on checking and servicing the cooling system on a Perkins if you want to keep it alive longer.

Also backs up my theories of the rods going more. The cast rods and lesser quality rod studs/bolts would be degraded from overheating. See a lot of posts asking about cooling system zincs on older engines without the bowman, and heat exchanger issues.

it's a pain to clean the exchanger and go through the cooling system. Full disclosure I haven't gone throu mine fully. I need to pull the exchanger and boil it at a radiator shop or leave in a bucket of acid for a bit. Raw water pump is leaking and needs to be replaced. My attention has been elsewhere the last couple boat yards.

[lexowgrant]

I wonder if the Bowman is a superior cooling system because the heat exchange tubes seem longer?