D25 Engine Rebuild thread

[bamfordsgarage]

Thanks Joe, I'm going to do the same. A question for you (and anyone else) — I couldn't budge the crank gear with my wimpy puller so I bought another, heavier, one tonight and will have a go at it in the AM. Is there some trick or is simple brute force the answer? My only experience with crank gears is on Model T crankshafts and a press is needed for both off and on.

[greg g]

I believe I used my impact wrench on mine. Starting out with pretty low working pressure, then increasing it until the puller began to have some effect. Then finished up by hand. I used a block of scrap wood to wedge the crank so it wouldn't spin.

[Dodgeb4ya]

I use a 3 jaw 10 ton "Posi-Lok" puller to remove the crank gears on the MoPar flatheads. Then press them back on with a special press tool I made This prevents damage to the rear thrust bearing by pounding on the crank gear to install it.

[Joe Flanagan]

Yes, a puller. I'd use generous amounts of PB blaster or something similar, especially around the key. I think I went to my local Auto Zone and borrowed a puller from them.

[bamfordsgarage]

And as usual, the right tool makes the job go easy. My new three-jaw puller slid the crank gear off with moderate force and no drama. I'll be happy if the replacement gear is as good a fit as the original.

Reamed the cylinder ridges today and started pulling out pistons. Cylinder #2 was the most interesting... this was where we discovered the broken top edge and ring bits back in April. The upper ring was completely gone — there had been about 1/2" embedded in the top of the piston when we pulled the head off, but either before or since that day the rest of the ring must have blown out past the exhaust valve.

Piston #1 was no great shakes either. The upper ring was a three-piecer and a bit of land was busted out between rings three and four. I haven't yet pulled the other four pistons but all the cylinder walls look fine. It will be interesting to see how the remainder are, but no big deal either way as I am replacing them with a set of 0.030 oversize from PatS.

Both #1 and #2 rod journals have considerable ridging and are not as good as they look in the photo. There's a crank grind and undersize bearings in my near future. I haven't looked at the mains yet.

There was surprisingly little wear and taper in the bores and if I didn't already have a set of 0.030s available I could do with much less. Eagle-eyed types (I'm talking to you, Don) may be looking at the last photo and wondering how the inside micrometer could possibly be measuring 3.367 across the nominal 3.375 bore — this mike reads 0.010 low from actual dimension.

[Don Coatney]

I am impressed by your tool knowledge and calibration! Way back in the late 1950's I learned to use a Ridge Reamer while working on a Ford flathead. In the early 1990's when living and working in California I hired a fork truck mechanic. His first job assignment was to rebuild a forklift. He could not remove the pistons. I suggested he use a ridge reamer. He did not have a clue what tool I was talking about.

Secondly I respect your knowledge on tool calibration. Always a good idea to take a known measurement and compare it to the field measurement for calibration. You will do well on this rebuild.

[Guest P15-D24]

Then press them back on with a special press tool I made This prevents damage to the rear thrust bearing by pounding on the crank gear to install it.

Just pull the square key out when reinstalling, mount the gear then re-insert the key with the help of a drift punch.

[bamfordsgarage]

Thanks for the suggestion P15, but perhaps the Canadian cranks are different — mine has a Woodruff key on the crank gear and a square key on the pulley. I anticipate pressing the crank gear on before installing the crank in the block.

Taking out the last four pistons revealed further damage. Only one didn't have a broken top ring, and the #4 and #5 pistons also had land damage. I was rather relieved to find all this as I had earlier harboured notions of just replacing the known-damaged #2 piston and putting things back together shadetree style. Hah. Have others encountered similar four-or-five-pistons-and-rings damaged during engine rebuilds? Man, these seem to be tough engines.

Main bearing clearance was 0.003 front and rear with 0.005-6 on the inner mains. Bringing this back to 0.001 should really help my oil pressure. There is a bit of scoring on three of the mains — I am wondering about only grinding them down to 0.010 under which will still leave some scoring. Or should I just take the 0.020 or so required to smooth them out completely?

I am impressed by how beefy the Mopar crankshaft seems — here is my D25 crank next to the '09-'25 Model T crank with which I am most familiar.

[RobertKB]

Chris, these are certainly tough engines. Wasn't that long ago that old tired-out thing got you nearly to the top of Pike's Peak and I am guessing most of the damage you are finding now was evident then.

Taking the mains and rod bearings to 0.001 is probably going to make things a bit too tight. I would double check the specs in your repair manual or get advice from others on the board. I would also recommend grinding your crank far enough to make it all smooth and remove all scoring. The crank in my '38 was ground 0.030 by a reputable firm in Calgary so 0.020 should be fine.

Go Fleiter, sometimes on here and often on the POC forum, I believe had to redo his rebuild as clearances were too tight. Maybe check with him or as mentioned, your repair manual or others. Don Coatney would be good to check with as his rebuild has lasted well. Good luck! I am loving this thread and all the good info and pictures!

[Don Coatney]

Chris;

I suggest you follow the advice and recommendations of your crankshaft grinding machine shop. These folks do this daily and the measurements they take and use are to be trusted more so than a Monday morning game critic.

When I bought my engine it was literaly in a basket. Completely disassembled and I was told all machine work (block boring and crankshaft grinding) was done. All of the new parts (oversized pistons, undersized bearings, timing chain and gears, etc.) were supplied with my engine. I (like you) checked the bearing clearance with plastigage prior to final assembly. I did not like my readings so I carried my crankshaft to a grinding shop. They also did not like what they found so I had them do a re-grind and had them supply replacement bearings. Fourty thousand miles later I am glad I did this.

I dont recall if you are replacing your cam bearings but you should do so. Sloppy cam bearings are one of the number one causes of low oil pressure in these flathead engines.

[wallytoo]

Have others encountered similar four-or-five-pistons-and-rings damaged during engine rebuilds? Man, these seem to be tough engines.

indeed, some of us have. here's mine:

http://www430.pair.com/p15d24/mopar_forum/showthread.php?t=19503&highlight=pistons

go to post #6 to see the pics of some of the pistons that came out of my truck. you were lucky. at least all of your pistons came out in one piece.

[bamfordsgarage]

Thanks for that link Wallytoo, very interesting reading. It's remarkable how well these engines can run even when they are so beat up inside. There was a comment in that thread about how overheating can brittle the rings — we overheated the engine real bad a year and 10K miles ago climbing to Mt Rushmore.

The last few days in the shop have been final disassembly of the block and preparation/cleaning for taking it in to the machine shop as soon as I get the new pistons from PatS. I had hoped to sort out what I needed ahead of time for bearings, but will, as Don suggested, let them have a look and go from there.

Because I am not hot-tanking the engine, I needed to do a thorough job of cleaning inside and out. The outside is ready to go, with only surface rust and what's left of the original paint, all the grime is gone. I found the best tool for this was a tile and grout brush from the neighbourhood supermarket — the bristles are stiffer and more aggressive than any parts-cleaning brush I've ever used.

The only items that gave me any grief during disassembly were the two pipe plugs at either end of the oil galley. I had high hopes for the removal tool I built from a 7/16" bolt but both plug heads fell apart like cheese. Dang. I managed to drill and break up the front plug enough to clear the threads but the rear plug was sunk below the surface and promised to be even harder to clear, so I drilled and tapped it for a smaller 1/8"NPT plug.

Then it was off to the carwash to give the water jacket and oil passages a good bath. Very satisfying and $14 well spent — got all kinds of crap and corruption out of the water jacket. I'll do it again after the machine work is complete.

[Joe Flanagan]

That's a cool picture of your block getting cleaned. Amazing to think that thing carried you across the country several times. Where did you have the cleaning done?

[Niel Hoback]

Thats a good way to clean a block if your car wash hasn't banned it. Ours won't let you wash greasey stuff down their drains.

[bamfordsgarage]

High everyone... (said the guy who spent too time at the parts washer).

My bell housing and bottom pan are all cleaned up, rehabilitated, and ready to install. It is a good feeling to have turned the corner on a few items.

Photos: They may indeed be clean creatures, but my workshop companion was not willing to help de-gunk the bell housing; Cleaning out the holes and threads; The fork boot had pulled out of the hole and the clamp tabs were poor — I drilled three small holes in the bell housing and wired it solidly in place; Inside view of clamp wires.

[bamfordsgarage]

The felt gasket on the bell housing pan was dirty and ragged — I replaced it with a surplus Model T Ford hogshead (bell housing) felt. The new felt was a little thinner than the original so I shimmed it out with a surplus 1/16" Model T valve cover gasket, and riveted the whole works together with Model T transmission band brass rivets... nothing like period-appropriate repairs!

The oil pump measured within specs and is almost ready to go back together. Problem is the manual calls for a gasket between the housing and end plate, but there was no gasket on my pump and none in my new gasket set (the lack of gasket could explain the slight wear pattern on the end plate). Can someone advise on what type and thickness of gasket is called for? My inclination is to use a very thin paper gasket so as to not substantially increase the rotor-to-end-plate clearance.

[Dodgeb4ya]

Looks like the black rubber O-ring is still in the oil pump body. That Square shaped rubber O-ring should come in your gasket set if it's a Felpro set. DO NOT use a thin paper gasket. You will lose all oil pressure!

Bob

[bamfordsgarage]

...the black rubber O-ring is still in the oil pump body. That Square shaped rubber O-ring should come in your gasket set...

Bob

Many thanks, Bob — just popped out to the garage and you are right on both counts. The imbedded ring was flush with the pump body and I mistook it for a discolouration on the surface. That, and I interpreted the referenced gasket as paper/cardstock. Oops. I'm hoping to blame all this on parts washer fumes.

[Young Ed]

Personally I would not even consider a used oil pump on an engine getting this sort of repair.

[bamfordsgarage]

I am surprised at that when this one appears within spec for wear and clearance. Could you elaborate?

[Young Ed]

Mostly just personal preference. When the rest of the oil pressure system will be fresh why not make it all fresh?

[Joe Flanagan]

Chris, mine had that kind of wear, also. I put it back together and it was fine. I can attest to what Dodgeb4ya posted. I was under the impression there should be a paper/cardboard gasket under the top of the pump, so I made one. The result was zero oil pressure. I also could not see the original gasket in its groove. If I recall correctly, I checked the clearance at the top of the pump with a feeler gauge as recommended in the manual and it measured correctly. I still had slight wear on the underside of the lid but it doesn't seem to have made a difference. I have good oil pressure.

Also, I bought new innards for the pump and replaced the old. I believe I got them from VPW.

[greg g]

I re used my 56 pump. The machine shop guy inspected it and delclared it up to the task. The clearence between the impeller is critical to the working presure of the pump.

You did not say whether your gasket set came with the proper O ring. As noted a paper gasket or RTV is a serious NO NO!

l would guess that as the rubber drys it shrinks and might lead to the scoring on the cover.

However, my manual does mention (but does not show) a gasket. It reads like it might be a gasket between the pump body and the block rather than between the cover and the body of the pump.

It gives clearences between the inner and outer rotor, and the outer rotor and the body, and the clearence of the rotor assembly to a straight edge across the body.

[wallytoo]

i also reused the oil pump in my 237. wear was within tolerance for each measurement, according to the instructions in the shop manual. i have 35 to 40 psi at idle.

i did replace the rubber 0-ring end gasket with the correct one supplied in my fel-pro set. seems to be fine.

wally

[Dodgeb4ya]

1930's pumps used gaskets. I've re-used oil pumps that were not scored excessively-no issues, good oil pressure..