Rebuild of a 1926 DB 4 Cylinder

[R.White]

I can't remember if it has been covered before but with the top removed from the gearbox you can check for wear.  Straight cut gears will of course always be noisy but the cause of excessive noise is usually found to be wear of the sliding gear surfaces and the main shaft.  You may well find that the gears actually "wobble"on the shaft.  The worst offender is likely to be the small gear nearest the front.  As this takes all the input thrust it can be severely worn.  If the teeth are badly pitted or even broken then it is a good candidate for replacement.  I don't think new ones are available except for early cars but I was fortunate enough to find a good used one. I tried to build up the bearing surface of the gear/ shaft but without success so I imagine  if you need to get these hard chromed it would be expensive. Even with new bearings (sealed) and a replacement gear my transmission is noisy in first and second - but top (which is direct) is quiet.

 

Ray.

Edited June 2, 2018 by R.White (see edit history)

[Wheelmang]

A small progress update - The throw out bearing is removed per Ray's instructions.

The clutch plates did not just slide off and it looked like solidified grease in the pilot bearing was the culprit.

The cam shaft plug was threaded, so a washer on the head of a bolt along with working my way around the plug with gentle pressure on a pry bar was successful. pressure from a pry bar removed it quite easily. 

And a question - The only marking I see is on the cam gear. I did not see anything on the cam itself. How is the correct position of the gear on the cam determined?

I almost removed the gear from the cam before realizing this.

The two "0s" on the cam gear line up with the single "0" on the crank gear OK. (not shown in picture)

Hope to get back to considerably more progress this week. 

[R.White]

That is right. I should have mentioned there is a risk of loosing the valve timing and with various different camshafts around these days you can't rely on the workshop manual settings.  The crankshaft gear has no markings on it so you would be well advised to make your own so they align with those on the cam gear.  Be very careful if it is a fibre gear.  

 

Ray. 

[Wheelmang]

Engine is at the speed shop for a dip tank cleaning then off to the welder. Does anyone know if the 3 main bearing crankshaft from a 12 V engine is the same as a 6 Volt? (Hope so or I may be looking for a crankshaft) Also looking for confirmation for original specs for the following (car #A716963)

- Crank - 1.750 on mains and 1.625 on rods. What is the minimum diameter for crankshaft rod journals?

- Pistons - 3.875 

Thanks all

 

[R.White]

The 3 bearing crank will not fit your engine.  I would suggest if you need a replacement crank it might be better to source a complete other engine.  The 5 bearing engine is a significant improvement over the 3 bearing unit.  Your call I guess.

 

Ray.

[Wheelmang]

Thanks Ray. I have a plan "B" 5 main that is re-buildable but am hoping to keep the 3 main that is original to the car. I may have been a little confusing on my question. Both the 6V and 12V engines are 3 main. If the cranks are interchangeable I would like to rebuild the original. Pretty sure I will need to come up with bearing caps for at least one main if going with the 5 main engine. Assuming (gulp) the rod bearings are the same size between the 3 and 5 main?

I really appreciate all of your insight on this project.

Paul

Edited June 12, 2018 by Wheelmang
Add text (see edit history)

[R.White]

MY mistake.  It shouldn't matter if you want to swap over 3 bearing cranks regardless of 6 volt or 12 volt type engines if they are both 3 main blocks.  I had forgotten that the "C" engine with 5 mains (like mine) didn't come into production until later in 1926. I have not actually done the swap that you intend so I can't say if there are any difficulties but I would have thought it would be possible, however, I don't know if the rod bearings are the same size or not.  

 

Regarding the bearings. If you need the crank reground I think you will have to get all bearings re white metalled and line bored.... Ouch!

 

O.K., I know I obtained good clearances by adjusting the shims and lapping the bearings to fit my crankshaft but the crank was hardly worn so didn't need a regrind.

 

Ray.

 

PS.  You mentioned a crack that needed welding.  It may not actually be visible but for every crack you can see there will probably be another corresponding crack in parallel.  I had a crack across a valve seat. I  had it "Cold" stitched then machined.  Another crack was frost damage in the water jacket and I repaired it myself using a professional epoxy by Belzona.  All OK so far!

 

Ray.

 

Edited June 12, 2018 by R.White (see edit history)

[herm111]

On ‎4‎/‎3‎/‎2018 at 11:30 AM, R.White said:

I would look into cold metal stitching as a preferable alternative to welding or brazing.  I have had very satisfactory results using this method.

 

I couldn't help noticing the crank grind tolerance of 0.010".  The crank needs to be much more accurately ground in my opinion.   0.001 " max.

 

Ray.

If you have a +, or - of .001, the crank is already wore out. The center line MUST be kept! You can't grind a crank like that, as you would a 350 Chevy! Your +, of - should be Zero!      Herm.

[herm111]

On ‎4‎/‎4‎/‎2018 at 11:47 AM, R.White said:

 

It all depends on what you want to spend!   Your engine (and almost all stock engines) came from the works without having been balanced.  If however you want your rebuild to be the best it can be then go for balancing. The most you can expect is a smoother running engine with a longer lifespan as the absence of vibration is a real benefit. Performance will still be limited.

 

Ray.

 

 

" AGREE "

[R.White]

4 hours ago, herm111 said:

If you have a +, or - of .001, the crank is already wore out. The center line MUST be kept! You can't grind a crank like that, as you would a 350 Chevy! Your +, of - should be Zero!      Herm.

 

I totally agree, Herm.  What I should have said is "run for the hills".   

 

Ray.

[Wheelmang]

Ray - Herm, I may have been a little confusing in some of my interpretations. The speed shop doing my crank etc is saying that the crank will be at less than .0005 tolerance. The original post of .01 was a typo on my part it should have been .001 That was the required measurement reading that I believe was given to me by someone who does babbitting so they could set rod and main bearings to crank spec. The actual main bearings will be line bored not honed. 

Is it OK to under size the crank? How much can be removed from the crank before it is not usable?

As to the crack repair, my welder now has the engine and I will be meeting with him the middle of next week to go over that process. He is military trained and now a retired welding teacher. At this point I am trusting his judgement for the best process but will definitely raise the various processes brought up here. 

Please let me know if I am missing anything here on the crank. 

Thanks all for you valued input. 

Paul 

[R.White]

Paul, seeing as Herm is with us I am going to leave it to him.  He is the engine builder here.

 

Ray.

[Wheelmang]

I will post a few pictures later, however, there were a few surprises found on the clutch assembly. (Not the engine proper rebuild but thought it best to keep this all on a single project post.)

One of my discs is bonded and the others are all riveted. It looks like Myers sell individual unlined disc but other than the bonded the disc looks to be in good shape. Still has the print on the face. Should I go ahead and remove the bonded and reline with riveted? If so what process removes the bonded lining? 

Thanks

 

[R.White]

I ordered 4 new clutch plates from Myers.  They came already riveted.  The only point that I would make is the way the lining material was riveted to the new plates.  The original clutch plates used open ended (hollow) rivets that are peened over at both ends.  The replacements used blind rivets and the heads are not very deeply recessed so in effect the clutch will not have a particularly long life.  That said, these cars seldom do high mileages these days so I am probably being over pessimistic.

 

Incidentally, how did you compress the clutch spring?

 

Ray.

[Wheelmang]

I had to make 1 clutch out of 2.The throw out bearing surface was severely worn on the one removed from the car and a couple plates were grooved.  Fortunately there was a spare transmission and clutch setting in my shop. Albeit a rusty one. 

Certainly the process used to remove the clutch spring is not found in any "best practices" instructions. Should anyone reading this try it - the spring does not appear to have much of a release stroke but be sure you do not stand directly in front of the vice nor put fingers in the open area to remove the c clips. Having clarified that, it actually worked quite well in the absence of a press. 

The OD of an old input shaft bearing was a perfect fit inside the spring housing. The outer bearing surface was cracked in the vise and the center ball bearings and inner race removed. It was then placed slightly off center on the spring housing in the vice and compressed.

 

The back side of the plate needed to be raised slightly, with the two raised sections on the vice jaws, in order to keep a slight down force to the front jaws. If this is not done the pressure will force the assembly upwards. 

Once compressed the first half of the c clip was removed with a magnet and then pressure was released, the bearing moved to the opposite offset and the second half of the c clip attempted to remove. There must have been a burr of some kind as it did not just fall out. I slowly released pressure and the clip held while the bearing case was removed and pressure reapplied to the spring retainer. The c clip then fell out. (As just the jaws of the vise on the spring housing released enough pressure to remove the clip it made me question if the bearing race I used was even necessary.) 

  

From there it was a simple matter of slowly winding out the vise to release all the pressure on the spring. 

Then on to drilling out the old rivets on the clutch plates. I found this worked best by drilling the rolled side of the rivet as opposed to the head side. Most of them fell out or just pushed through that way. 

Then on to bead blast and clean up. 

Time to spend money at Myer's.

A real press will be added to my shop before reassembly. This wasn't the safest procedure I have ever performed but worked on the moment. 

Anyone know if any of these clutch components originally had paint or metal preservative? 

[R.White]

This is how I did mine.

[Wheelmang]

That looks a whole lot easier and safer than what I did. A press is working it's way into the budget. 

Your throw out bearing surface looks like it also has some wear. There are major grooves in mine. Fortunately the spare had no wear. Way less movement in the throw out bearing now. 

[R.White]

I expect you know, but it is advised that the two anti rattle springs are reinstated when you put it back in.

 

 

Ray.

[Wheelmang]

Both springs were missing and I do not see them listed at Myers. There were some partial pieces in the crud at the bottom of the bell housing but not enough to figure out a way to make new ones. Would you or someone have a picture to go from or possibly a source to purchase. 

Paul

[R.White]

Romar supply them.

 

http://romardb.com/catmain.html

 

 

 

Clutch Springs. If your clutch is noisy, you probably need these springs. Replace both at once. #427S $20.00 EACH(TAKES 2)

 

Edited June 28, 2018 by R.White (see edit history)

[MikeC5]

Great photos and descriptions on how to for future reference.  Thank you guys!

[Wheelmang]

Thanks Ray - Myers had them, I just missed them. 

[Wheelmang]

My welder friend Dave has advised that the cracks are repairable so on with the block repair. 

There was a second crack found at the base of the carb intake when the block was dip tanked and cleaned. Interesting that this was not leaking but we decided to go ahead and weld it anyway. Both cracks were cleaned up and channeled. There are holes drilled at each end of the crack to stop further running. 

In order to weld on the cast iron it needed a temp of approximately. 400°. 

Cast composition was tested and determined that the best welding process was TIG with 95% nickle rod. 

Then a slow cool down with sand to absorb the heat.

 

I should be picking up the finished job tomorrow. Then back to my shop for grinding the welds smooth.

The speed shop has been advised to go ahead with the crank and as soon (likely a few weeks) as they provide me with the journal specs, the rods and mains are off to Herm for Babbitt.

Stay tuned!

 

[R.White]

Good to hear you are in Herm's capable hands.  

 

Ray.

 

 

[Wheelmang]

With everything forward of the driveshaft out and on benches, in bags and plastic bins there is no shortage of projects. Today was a quick one on the throw out bearing. It probably did not need to be totally torn apart but it was sitting there staring back at me all greasy and dirty and rusty. So here is what the inside of a 26 DB throw out bearing looks like all disassembled. It was actually pretty badly caked up with hard grease so it was a good thing to tackle. It came apart quite easily by grinding off the back side of the four rivets and punching through. 

There were also some small ridges that had raised up on the left side of a few of the ball bearings. They came off quite easily by letting the balls drop to the lower part of the retainer. This allowed the ball to drop just enough out of the way. It then took just a lite stroke or two with a fine tooth file to remove the burr. 

It is not completely reassembled yet as I need to find some rivets or more likely will get some machine screws with nuts, tighten up and a quick spot weld to hold all in place. It is working way smoother now.

 

 

Edited July 2, 2018 by Wheelmang
word edit (see edit history)

[Wheelmang]

I am going to replace the valve guides on this mostly because it seems like the right thing to do at this stage. Do they press out and back in or is it something more complicated that needs to be left to the engine rebuilder?

Thanks

Paul

[R.White]

I pulled my guides because the method of using a cold chisel and hammer (described in the manual) seemed too risky.

 

Also, measure the new ones.  Mine were about 0.003" too big and I had to turn them down to fit snugly..  

 

You will presumably be renewing the valves.  The retaining pins tend to leave a groove in the retainers which prevents desirable rotation so it would be good practise to machine out the groove.

 

Your engine shop will be able to cut new valve seats which in my opinion is likely to be more accurate  than doing it yourself.

 

Finally, check the valves don't stick at any point in the new guides.  I thought mine were o.k. but I suffered a sticking valve on the first outing.  

 

Ray.

[Wheelmang]

Got to cleaning and painting the U-Joint housing and have a question about the shims that go between the housing and the back of the transmission. There are five of them. Two are .032, two are .023 and one is .013. That leads me to think that there is some kind of shim spec for that union. If that is the case how is the correct spacing determined. It is a looong way before I get to reassemble but will be good to know at the time. 

Thanks for looking

Paul

[Wheelmang]

6 hours ago, R.White said:

I pulled my guides because the method of using a cold chisel and hammer (described in the manual) seemed too risky.

 

Also, measure the new ones.  Mine were about 0.003" too big and I had to turn them down to fit snugly..  

 

You will presumably be renewing the valves.  The retaining pins tend to leave a groove in the retainers which prevents desirable rotation so it would be good practise to machine out the groove.

 

Your engine shop will be able to cut new valve seats which in my opinion is likely to be more accurate  than doing it yourself.

 

Finally, check the valves don't stick at any point in the new guides.  I thought mine were o.k. but I suffered a sticking valve on the first outing.  

 

Ray.

Hi Ray:

Yeah the cold chisel sounded pretty radical to me as well. You say you pulled them. Could you please describe the process you used? 

All my retainers are refurbished and new pins made. I had just completed an interim valve job to get me to the point when I could do the whole engine up proper. Just didn't expect it to be so soon afterwards. Machine shop will be cutting new seats and all new valves and springs will be coming from Myers.

Thanks for the heads up on the oversize and sticking. 

Paul

[R.White]

Hi Paul.

All I diid was make up a puller from a long bolt with a little distance piece under the head to bear evenly on the end of the guide.  I think I used a length of tubing on the other end or it may have been an old box spanner; I can't remember now but it was all quite simple really.  I seem to remember if the camshaft is out the guides can be removed from either the top or bottom.  You will see the original guides have a ribbed surface which I suppose is to help keep them in place.  Sadly, the replacements don't have this and are perfectly smooth.  I didn't attempt to give them a key other than the fine machining marks left by my lathe but they are in quite tight so fingers crossed they will stay put.

 

BTW.  When you get the babbit done I understand that the end play of the crankshaft is determined by the white metal on the sides of the centre main bearing caps.  Probably teaching granny to suck eggs but better safe etc.

 

Ray.

[R.White]

1 hour ago, Wheelmang said:

Got to cleaning and painting the U-Joint housing and have a question about the shims that go between the housing and the back of the transmission. There are five of them. Two are .032, two are .023 and one is .013. That leads me to think that there is some kind of shim spec for that union. If that is the case how is the correct spacing determined. It is a looong way before I get to reassemble but will be good to know at the time. 

Thanks for looking

Paul

 

I haven't seen any information about these shims so I just put them back the same as before .  You may find the original seal needs replacing but if it is OK then leave it in place.  I didn't know what was the best grease to use so went with a multi purpose grease.  I used plenty of lube on the universal coupling.

 

Ray.

Edited July 6, 2018 by R.White (see edit history)

[DB26]

Thank you guys for the great pics and valuable info. Bookmarking for the future since I have practically the same automobile. 

[Wheelmang]

Thinking this thread should have been named engine and drivetrain rebuild. I am now into the transmission as long as it is out. It is looking like a few months before the "outside" my shop engine work will be done. Now looking to sometime in late October or November before the engine will be ready for re-assembly. So the first piece removed from the transmission was the idler gear? (Probably the wrong terminology.) The one removed (on the left) does not look to be in the best of shape. I had a spare and don't think that looks much better. Would you use either one? I am considering re-installing the original. it was working fine before removed. 

Anyone have a replacement that is in much better shape?

Thanks for looking 

Paul

 

[MikeC5]

If it's the reverse idler I wouldn't be overly concerned since it only comes into play when tranny is in reverse.  The one on the right looks a bit better shape to me.

[Spinneyhill]

One on the right looks less worn but it has been rusty. If you refit the original, would it work if you put it in the other way round?

[R.White]

My only concern with changing the idler gear is different wear patterns. My father used to go on about "matched gear sets" but I don't think we have that luxury.

 

 

Ray.

[Wheelmang]

On 7/19/2018 at 6:08 AM, Spinneyhill said:

One on the right looks less worn but it has been rusty. If you refit the original, would it work if you put it in the other way round?

I had the same thought but it is the reverse engagement gear so the worn side will still be in use on the larger gear. I decided to go with the one that had the most metal left even though it showed some pitting. Hope to reassemble the trans today and will post some pics when done. 

 

[Wheelmang]

I started to reassemble the transmission and decided it best to replace the transmission input and output caged ball bearings. Neither felt real bad but just enough question to go ahead, especially given the need to pull the engine should they go bad any time soon. 

I am not sure if it will hold true with all bearings on the DB but this is now the third time that bearings were readily available from my local parts house. Should you find you are in need of bearings you may be able to save some money by knowing a little more than the part guys. When I originally tried to get them to interchange the 3080 "it didn't interchange". A little research on the SKF site with size and dimension found that the original Fafnir 3080 is a fairly common and readily available 308. The same was true on a 2070 being a 207. I had one other instance for the pilot bearing. If you happen to need a sealed bearing, a suffix of "S" is sealed on one side and "SS" is sealed both sides.  

The counter shaft bearings were unlike any bearing that I have seen before. Kinda neat the way the spirals on the rollers force feed oil in all directions. 

Now on to the question for the day. 

Is there a secret in removing the transmission lock. The wedge easily punched out from the underside of the top cover. I tapped lightly on the underside of the cylinder but it does not appear to be moving at all. Better to ask before I get any more aggressive on the punching. 

Thanks for looking. 

Paul

[Spinneyhill]

Re gearbox bearings. I replaced the input pinion bearing in mine because it rattled when in neutral. The new one does too. Someone said something about the clearances or something to do with transmission bearings. I never chased it up so don't know what it was about.

 

Most of the time, we can easily source bearings by size. Timken have a number of documents available on line with bearings (and seals) by size. The SKF web site is a good one but harder to get a reference by size. Other manufacturers also provide documents on line but they can take a bit of finding.

 

Quite a few of our bearings are metric, probably because of the source in Europe. Some were local, such as Nice bearings.

[R.White]

I was advised that replacing the bearings would not make any difference to the noise - and they were right.!!

 

The countershaft assembly should have a distance piece at one end.  On my gearbox this was missing and the gears were able to move backwards and forwards alarmingly!

When I turned the box over,  a thick washer fell out - this would have been the distance piece but a po had presumably attempted to replace the bearings (bushings in my case) with the gearbox in situ and dropped the washer.  It must have lain in the bottom of the gearbox for many years.!

 

Ray.