Rebushing the cam bores in a worn out block..

[F Bill]

Sometimes when you go to rebuild the flathead 134 you will find your low oil pressure is due to a worn block where the camshaft rides in unbushed bores. While not a simple repair to do, involving a machine shop and some creative parts sourcing and machining, it is possible remachine the block, cam, and use modern Ford V8 bearing shells from a 289 for two of the bores. �

The first bore at the front already has an insert in it. They shoudl be available in undersizes if your cam is worn beyond tolerances.. The second and third bores can be bored out to accept bearing shells from the 289 kit. The last bore, if it is worn beyond tolerance, we have yet to find a manufactured cam bearing insert for. The second and third cam journal will need to be turned down and the installed bushings reamed to fit the turned down journals with the factory clearances maintained. The bushings need to be pulled in with a tool made for the process, not hammered in.

I will cut and paste some of the finer points as given by a couple of gentlemen on the g 503 board who had done this to their engines.

to be continued

[F Bill]

here is what John Gibbons, "Artificer" on the G 503 board had to say on the subject.

by artificer � Fri Dec 07, 2012 10:01 pm

Straight from an engine machinist/rebuilder [Bryan King] still practicing his trade in Brisbane Australia @ 75 years of age....

The L134 [assumed F134] block number 2&3 cam bores are machined to suit the bushes that are pulled into correct place, oil hole alignment & using loctite.

At one time it was possible to buy individual cam bearings & he had a box filled with all different types.

The front bush used is standard jeep
The second is Ford 302 or other Ford engines using the same bearing
The third is from a Ford Trader Diesel [it is 1.5" wide so each side has 3/8" parted off so the oil hole is still centalized]
added he used these because they were what he had & there would be others that would fit.
The front & 2nd were always worn most & he indicated he had seen them out 0.008" through wear or rust exposure needing repair.
When his work is done he has 0.001" clearance.
The 4th or rear is not touched....
My Comment: It would be common sense to look @ bushes for common vehicles & ascertain whether their cam bushes would suit if one was having to buy sets & discard what was not used.
I recollected him talking years ago about Perkins he was referring, in that conversation, to the rope type rear main seal he used & it is specified for Perkins diesel engines . He stated It is perfect for the L134 & much better than stuff in kits, that he throws out.
Folk like Bryan who sell their labour & expertise usually know the right/best ways to avoid comebacks or re-do's.

[F Bill]

And here is how it is done in Hungary by "SB5477"

"The part number of the bearing set I used was SEP 1204M. Both the cam and the block needed machining. Had to select from the five bearings those which needed the minimal material removal from the block and cam. The rear was also bad and a bushing was used made from aluminium similar to bearing material. The oil hole on the bushing had to be calculated/marked carefully to end up exactly in the right place. The machined areas for the new bearings must be exactly in line. After the machining and bearing installation (by pulling NOT hammering) is done measure the size of the compressed bearings inside diameters in the block, than the cam has to be machined to have the exact clearance required. This was done on a GPW block.
This is how I have done it. Hope it helps."

The set used SEP 1204M when googled reveals a 289 Ford application. It is a valid NAPA and Federal Mogul number.

[F Bill]

Joel Gopan aka Ben D. from Maine , an old time military surplus guy who has been around jeeps for a good long time, had a few tidbits to add...

"It is a custom job as there are no Jeep factory bearings for Front Intermediate, Rear Intermediate and Rear Camshaft Bores of the 4 Cyl Jeep engines. They seldom are out of specification as the Camshaft rotates at 1/2 the RPM as the Crankshaft and the wear is a bit slower.
Below are the dimensions.

Front Bushing Type Bearing 2.1870" Minimim, 2.1880" Max. This can be replaced.
Front Intermediate Bore 2.1250" Minimum, 2.1260" Max.
Rear Intermediate Bore 2.0625" Minimum, 2.0635" Max.
Rear Bore 1.6250" Minimum, 1.6260" Max.

"Some manufacturers have optional undersize cam bearings for worn camshaft journals, for example, GMC has 0.010", 0.020" and 0.030" sets available available for the CCKW engine, which has 4 bearings compared to one on Jeep. Jeep's one bearing at the front also comes in 0.010", 0.020" and 0.030" undersize, but only the front bearing journal on the cam is serviced.

The Federal Mogul 1091M fits the MB/GPW engine, all 134 Cu.In. CJ and M-38/M-38A1 engines. It can be easily installed with a hammer and block of hardwood and needs no staking."

IE if your cam bores are all good except the front one and you have a worn cam, you can turn down the cam and use an undersize stock bearing on that one journal. If you were replacing the cam with a good one you'd still use a stock size fromt bearing behind the timing gear/sprocket. I haven't double checked Joels specs for teh stock bores but I would bet he has them right.

Also at the end of the conversation Marty from SoCAl  added this helpful bearing locating info.

"by Marty, SoCal � Sat Dec 08, 2012 3:04 pm

A "Dura-Bond" part # F18 small block Ford set is $14 from Summit:
http://www.summitracing.com/parts/dur-f-18

They do make undersized ones for the Ford smallblock V8

The catalog is downloadable, they have the sizes listed for all the available bushings:
http://www.mellingdurabond.com/Portals/ ... ior_r3.pdf
Smallblock Ford listings are on page 14 and 15.
Set component size listings start on page 54.
Progressive size listing by housing bore diameter starts on page 90 (add in the wall thickness X 2 to get the ID)."

So, that about does it. If anyone has a listing they have found that would work in the last hole, let me know or go ahead and reply to this post.  So it CAN be done, and has been done, and if you have a jeep engine that has low oil pressure due to worn cam bores, you CAN fix it. Cost? ...One poster in the thread over at the G 503 board felt two or three hours of shop time shoule be all that is needed , but it might even be double that. These old blocks are getting scarcer every year, so if you need to save one by doing this, you are preserving just one more irreplaceable  block.

[Carls_jeep]

Bill, you sure did a lot more looking than I did, but then, I was in the middle of a rebuild and didn't have time to get to involved, I needed to get to Utah. I still have the old block that is cracked and needs a lot of work and will experiment on it later. Thanks for doing all this digging. I will cut and paste and save the posts in this thread. I may need the info.

Bill, I got the block bore dimensions from Sean and BobW and all your dimensions are correct except for #1 bore. The #1 bore dimension I have is 2.3165" to 3.3175". That is the bore dimension without the bushing.

The thing I didn't do was look for a bushing with an ID that was just small enough so you would have to grind the cam journal. I will go back to the engine shop and look through their books with a thought of grinding the cam journals.

I would much rather grind the cam journal than hone or bore the ID of the bushing. The bearing surface inside the bushing is best not tampered with so it's best to grind the cam to fit. In fact, I would bore the block, install the bushings, mic the bushing bores and then grind the cam journals for .001" to .0015" clearance. The oil clearance spec for the L134 cam is .001"-.0025". If someone decides to do a bore job they should document the ID the cam bores were machined to, the numbers of the cam bushing sets they had to use and which ones out of each set they used, the ID of the bushing when installed in the block and the cam journal OD's they ground the cam to. The more data you save the better off you will be later on.