Perkins 4.236 Serpentine belt conversion

I have been looking at power generation upgrades and have started the serpentine belt conversion. The conversion was documented on CF but I'll post most if that here as well.

I ended up ordering the pulleys from SW Diesel and will need to make a few things. I'm thinking to report on progress in this thread instead of making a new one....
The pulleys are ordered individually from SW Diesel and came in about a week. TAD and others have full kits. I've not called Balmar but they do not list a 4.236 in their product list.
It is interesting to note that the water pump pulley has a vee bely groove in it so that should need to you can revert to using the vee for your alt or another use.
The crankshaft pulley mounts on the front of the crank pulley and thus has the original vee groove available.
The serpentine belt will be forward about 3/4" so the alternator will need to be mounted that much further forward. The spacer to do this is included in the TAD kit. I'll just have to make my own.
Also, rather than reuse my existing coolant pump I've ordered a replacement. The old can be a spare.

Crankshaft pulley
Water pump pulley
Alternator pulley
On edge

The first step is to mount the new pulley on the front of the existing crankshaft pulley. First I needed to clean out the 4 holes in the existing pulley. They had 30 years of gunk built up in them.
I started with some deoxit-5 on a 1/2" round wire brush. This cleaned out a lot of the junk from the holes.
Then I used a tap to clean the threads. After wire brushing the tap went in nicely.
Lastly I will de-grease the threads so that the thread locker will be able to do its job.
The front surface of the existing pulley has been sanded to remove surface rust and present a flat mounting surface to the new pulley. The insides of the new pulley will be coated with tef-gel and then bolted in place.

This photo shows the serpentine pulley mounted to the existing pulley. This is a test fit before using thread locker to be sure that there are no problems (like the pulley wobbles).

The bolts are grade 8 - 7/16" x 1.25" 20 tpi and I'm sure that they are overkill for the application.

Crank pulley mounted on engine

THe new water pump arrived. I did some dry mounting of the pulley. It is a tight fit so I did not push it on very far. It will get a coat of tef-gel on the shaft and then the nut will pull the pulley onto the shaft. Lastly, I'll torque the nut.

Water pump front
Water pump top

Well, I got a little more time to work on the serpentine conversion for my boat.

I bought the pulleys from SW Diesel for a good price. The kit from TAD has the same pulleys but costs more by a bit. However, the TAD kit comes with the alternator spacer that is required to move the alternator 3/4" forward.

Being a DIY kind of guy (as are so many sailors) I decided to make one myself. TAD would want $90 for the spacer if they had any to sell.

The Alternator needs to move 3/4" forward because that is the thickness of the vee-belt pulley that the serpentine pulley mounts on.

The first step was to remove the alternator and alternator bracket. That done I sent the alternator off to PMX here in Portland for an inspection and rebuild. I also have a 150 amp Helr alt that is really dirty so I sent that off to PMX as well. Bill is a great guy and knows his stuff and gives super service.

In addition to new brushes, bearings, checking diodes etc I had PMX install the 6 groove serpentine pulleys. PMX charges $100 plus parts and considers the alt to be remanufactured.

It was time to get busy making the spacer. Based on info from the web including the photo of TAD's kit from their website I decided that the space could be made from a 3" long piece of 2" wide, 3/4" thick mild steel (a36) bar stock.

I went over to our local Metals Supermarket and for $5 they cut me a 3" piece of 2" x 3/4" bar.

A36 machines well and is easy to work with. The forces are low and mostly compressive so it is a great choice. But any mild steel would work.

Here is a rough drawing of what needs to be made....

I have indicated that the mounting bolt is hex head but this is allen head. The white section is the spacer I needed to build.

The shaded section is the existing alternator mount, and the offset between the bolt that mounts the alternator bracket and allen bolt that mounts the spacer plate is 3/4".

I used a Q drill for the pilot holes then a 3/8"-24 tap for the bracket mount.

The allen head bolts need to align with the existing mounting holes on the engine block. So rather than use a 3/8" drill for those holes I used a larger drill ( 13/32" ) to give some tolerance for alignment.

But before starting that hole I drilled the recess for the allen head cap bolt using a 1/2" pilot point drill to make the pocket for the allen head bolt.

The pilot point drill starts with a small set of cutting faces and outside of those are flat cutting faces to the full width of the drill. Sadly the allen head diameter is more then 1/2" so I ended up in enlarging the pocket with a 5/8" tungsten carbide concrete drill I had laying around.

It would have been better to use a larger pilot point drill but I had the 1/2" already and the cost of the concrete drill (about $8) was less than the cost of a 5/8" pilot point ($25).

Sketch of spacer

I don't have a milling machine in the garage anymore so this was all done on a drill press. It could have been done with an electric hand drill motor and a vise.
Here is the final results assembled. Of course it needs to be painted....

I did take the time to trim the spacer on the alt bolt so that I could get a few more washers in. With the washers the alt could move forward and back a bit and I would rather have it mot moving around or need to tighten the bolt so much that the mounting bracket is bent a lot.

Alt and spacer
Alt and spacer

Here are some closer looks at the spacer plate....


Lastly, the allen head bolts are "captured" inside the spacer plate.

The installation requires that the existing mounting studs be removed from the engine block and the spacer plate bolted (using the allen heads) in place.

The thing to look for here is that these mounting holes are through drilled and if the allen bolts are too long they will make contact with gears inside the engine. This would be very bad for your engine. (camshaft gear I think)

The studs only screw into the block about 1/3" and thus you should get allen head bolts that are only long enough to go 1/3" into the block.

When mounting them use loctite after cleaning the threads.

I will be measuring the depth when I get to the boat to install this bracket but will keep to the 1/3" depth unless I see that there is a lot more space.

Here is a side view of the allen bolt in place in the spacer.

Allen and spacer

One last update re the mounting bolt depth.
On my 4.236 I can screw the bolt into the block 18 turns till it touches something (gear teeth or???) That works out to 3/4" (18/24).
On the spacer plate I made the allen head bolt screws in 8 turns or about 1/3" (8/24). Leaving more than 3/8" clearance. Sounds like plenty.
Everything mounts up nicely and in alignment. The tension arm need to be straightened so as to make sure it did not hit the expansion tank.

Well now I got a bit more time on the boat this weekend. The short of it is that the serpentine kit is installed and working. No photos yet, it was messy and I did not want the camera anywhere close to it.

There was of course some drama....

I started out taking off the water pump to put the new one on. I had put the serpentine pulley on the new pump a while ago. I just wanted to install a new pump and use the old as a spare.

After draining the coolant to a lower level I pulled the header tank off. This exposed the thermostat. This engine takes a 63mm dia thermostat (about 2.5") which my local auto parts store had in stock. More on that later.

Going after the water pump 3 of the 4 mounting bolts came off with a normal amount of force. But the last one just would not budge. Ranter than use BFI (Brute Force and Ignorance) I took this as an opportunity to buy an electric impact wrench.

That bolt came off without any problems. I can use the impact wrench other places. I've been needing one for years. It set we back $133 at Lowe's. Money well spent vs a mangled mess.

The pump is actually 2 pieces - the actual pump and a pump housing that bolts to the block. The pump housing is reused and the pump bolts into it. (gotta be a better name than pump housing which is really is not).

With the new pump installed into the housing I bolted it back onto the engine. Now I had all 3 serpentine pulleys installed and was able to measure the size of the belt needed. Off to my local NAPA and I had a K06052 (52") Gates green stripe 6 groove belt in hand.

That took up the day and it was time to head home to make pasta.

Starting again today I installed the belt and spacers for the tension arm. The tension arm needed to be straightened a bit so that the alternator would move from one end to the other without hitting the header tank on one side or the alternator on the other. I just put it in a vice and flattened it out a bit.

The old pump had the port open for a heater, the other end of the circuit is on the head. But there was no heater core so the PO just ran 6' of heater hose. The new pump has a plug in the port so I decided to pull the host and close off the port on the head.

The port on the head had a Tee and that is also where the temp sender is. Just a bunch of brass fittings... Should be easy right?

Of course all but the fitting in the head came off easily. The one in the head was a 3/8" NPT nipple - or should have been. The nipple was threads from one end to the other and of course was frozen into the head.

I worked on it with vice grips and heat and PB Blaster and then a chisel. Nothing, not a budge. Expecting the worst I dug around and found a 3/8" npt tap and get a 9/16" drill. 37/64" is the normal hole size for a 3/8" npt tap but 9/16" (36/64") is listed as an alternate. I figured that 9/16" would be safer and less likely to damage the threads.

Using a cordless drill (and a shop vac) I drilled into the brass nipple. I had already cut the brass off flush with the head and at low speed drilled through the nipple

Now luck would look my way. As I poked a bit of brass off the edge I was able to grab it with some pliers and pull it out of the threads all the way to the bottom. Using the 9/16" paid off. Kinda like opening a can of sardines the brass just unwound out of the threads. No need to tap the head. the threads were undamaged.

I bought a brass coupler (3/6" male, 1/2" female) and screwed that into the head. The temp sender was then screwed in the the coupler. Great, now we do not have 6' of hose waiting to go bad and the them sender was installed.

The thermostat was installed, I cut a new gasket and installed the header tank. Tension the alternator, with up the harness and positive and negative cables to the house bank. Fill the header tank with coolant and we were ready for the moment of truth.

Turning the key the engine starts normally, No bad sounds - is good. Water pulses out the exhaust and everything looks normal.

The alternator is only a 100 amp unit and at 1000 rpm (need to recalibrate due to the 1:3 pulley ratio) the alter is putting out 40 amps or so. Then up at 1800 rpm the alt is running at 80 amps into a 90% SOC 700 LiFePO4 bank. Bulk is set at 13.9 volts (I'll change this to 14.0 later)

Up at 2000+ RPM I'm seeing 100 amps or so. Not bad.

The temp kept climbing. This is normal for this engine and for many 4.236. Their thermostats do not have a jiggle valve or air bleed hole and at least in my engine the temp goes up to around 210 then drops rapidly to 185 when the thermostat opens.

Nothing like that this time. It just went up and stayed up.

I'm guessing I have a pretty big air pocket in the coolant system.

Out of time so the engine is shut down before it gets too hot.

Next time I'm there I'll pull the header tank and drill a 1/16" air bleed hole in the thermostat and see if I can do a better job of filling with coolant.

It also appears that there is a slight leak around the temp sender. I could torque it down more to see if that stops the leak or I could put a different set of fittings that give more depth of threads for the sender.

Time will tell.

Oh Yes, one more thought.

I think I'll (once the temp issue it fixed) switch over the the HEHR 23-12M 150 amp alternator I had rebuilt at the same time as the 100 amp Balmar. The Balmar has better overall low speed output but the Hehr Powerline may provide more current at 1000 rpm idle (3000 rpm on alt) and 10 or 20 amps more at WOT (2200 engine RPM 6600 alt RPM).

In any case I plan on an AT-160 later. It will be interesting to see the differences in output between the 2 alternators.

OK, may be I'm tired.

I wrote 3/8 npt up above and should have written 5/8" UNF. Just change that in your minds.

PS Hey mods, can I change those posts? It has been over 30 minutes.

OK, got some time tonight.

First on order is the temp sender. Trying to use the old one was a bit of a kluge because it was too big for the port in the head and I cobbled together an adapter. I got some slight leaks that way.

Knowing what thread the port was cut to is also a problem. At least one source indicates that it is 5/8" UNF. However, most temp senders are NPT. And 3/8" NPT 5/8" UNF are close to each other (if you know UNF and NPT then you know the differences)

It turns out that west marine had 2 of the senders I was looking at in stock. This boat uses a dual station sender (2 gauges, on at the helm and the other below) and 3/8" NPT would fit so I picked one up on the way home from work. ( WM # 1654854 | Mfg # 18-5897 ) Plus I had some rewards coupons in my pocket.

Back on the boat I pulled the header tank and drilled a 1/16" hole in the thermostat ( Slant 13478 ) The idea here is that air can escape and that in a cold engine some hot water gets through. More on that later.

With the header tank still off and the temp sender not installed I put a funnel into the port on the head and poured 50/50 antifreeze into the head until it started to come out of the hole in the thermostat.

At that point I reinstalled the header tank topped off the port in the head. Then I installed the temp sender and filled up the header tank.

With the fill cap still off I (moment of truth) started the engine. Amps up to 40 at idle, a few bubbles working their way out of the expansion tank fill. Top off coolant as needed and when the coolant started to expand I put the cap back on.

Letting the engine warm up gradually I kept taking a look at temps with the IR temp meter. No leaks and perhaps a slight mositure around the temp sender. Perhaps it needs another 1/4 turn when the engine cools down again.

Up the rpm and the alternator is putting out 80 amps into at 95% full 700ah LiFePO4 bank (100 amp alt). The regulator is set to 13.9 v.

Temps keep rising and eventually settle at 180 degrees (via the gauge). The IR temp meter reads 185 on the head bolts - Ran it a full rpm with no load and the temp stayed rock steady. The return coolant temp went from about 90 F at idle to 110 or so at near WOT with the gauge reading rock steady.

Ok, back to the hole I drilled in the thermostat. When using the original thermostat the temp would rise and rise and go up to about 210 F then after a time fall back to 185 F. This was always something that worried me (was it sticking, faulty etc).

The reason this happens is that with a thermostat without a hole there is no warmed coolant on the temp sensing (wax) side of the thermostat. So the thermostat stays closed until the conduction from the hot side to the cold side is great enough to allow the thermostat to open (and it does in a rush). It looks like it is stuck then releases.

And in my case because i removed the heater circuit there is more or less no coolant flow until the thermostat opens up which can cause localized hot spots in the head.

By drilling a small (1/16") hole in the thermostat I now do ger some coolant flow from the hot side to the cool side when the thermostat is closed. This allows some circulation in the head while the engine is coming up to temp and of greater value to me it allows the wax pellet to cause the thermostat to open in response to the coolant temp. No more "sticking" - the temp just rises to 180 F and stops there.

Well, I think that we can call the serpentine belt conversion a success!

Pulleys bought, adapter made, belt installed, pump installed and full amps (more or less) without belt slipping.

It does look nice to see that wide belt moving at low rpm.

The ratio from crank to alt is about 1 to 3 so at 1800 RPM cruise we will be turning the alt at 5400 RPM.

And at 1000 RPM the alternator could still produce significant output.

I'll have to discharge the batteries to 50% SOC and set the "bulk" to 14.0 v and then see what current the alt will put out.

As a point of reference - when the alt was producing 80 amps the alt case was at 176 F after 10 minutes.

Need to get a few more photos and then call this thread done.

Looking good - as always with things boat, if you uncover one area another problem crops up. The starter has decided it it time to be rebuilt.

I get a a little weeping around the temp sender in the head. The sender is 3/8" NPT and perhaps the head is 5/8 UNF after all. I'll see if I can source an adapter to fit a smaller diameter sender.

Here is a last photo of the full system. Hopefully this thread will be of use to someone who wants to piece together a serpentine kit for their 4.236.

Alt and spacer