The Stovebolt Site Forums The Shop Area Engine Shop 235 cam thrust bearing

I need a new cam thrust bearing so I can install a hydraulic cam in my 235 but I cant find one anywhere. All the vendors I checked are "out of stock" If you know of a source I'd appreciate it greatly.

Thanks
Craig

A stovebolt cam does not have a "thrust bearing"- - - - - -there's a steel thrust plate that bolts to the front of the block that controls fore/aft movement of the cam. If that's what you need, send me a PM. Unless yours is badly worn, recycle the one on your present cam.
Jerry

My Bad, the thrust plate that was with my old cam looks like its made of brass or bronze and is pretty scored from the cam. I imagine the clearance wasn't set right originally. I'll send the PM as requested. Thanks for the information and response to my posting.

Jerry, I recall that thrust plate I sent you being bronze as well, not steel.

Craig - Jim Carter shows his offered Camshaft Thrust Plate PN: ME990 as ready to ship. Includes the spacer ring. I also found it listed at Chev's of the 40's as Item 3702305 37+57, although I can't tell if theirs is in stock or not.

The Filling Station shows their Part# FS-625 as brass material.

The previous two sourced parts I listed don't appear to be brass.

I've got a thrust plate I removed from a worn out cam that appears to be cast steel, maybe? A thrust plate for a 230/250 engine will bolt on, but I believe it's a different thickness.
Jerry

You believe it's a different thickness, Jerry? What happened to measuring? I know you have one that's bronze that came off a 1958 235 because I sent it to you.

I checked the jim carter listing and its for a GMC. The chevys of the 40s looks right but mine didn't have a spacer. is that for early engines?

I don't have a 250 thrust plate to measure, and no plans to acquire one anytime soon. If it's thicker, which I believe it is, a magnetic lathe chuck and a tool post grinder could be used to adjust the thickness. Some timing gears have a step built into them to establish the correct end play instead of a spacer.
Jerry

Craig - Sorry about the initially thought incorrect advice on the Jim Carter part. The correct one listed for Chevrolets from Jim Carter should be ME727 and as you noted they are out of stock.

A peek in some Chevy Master Parts books shows the original part is listed as Parts Group 0.533, Bearing, camshaft thrust GM# 3702305 fitting ALL 1937-53 6 cylinders. That part number was later replaced by GM# 3707916 which began in 1954 and is further listed as fitting 1938-62 6 cylinders.

Interestingly enough, GM# 3707916 is also listed in a 1963 GMC Master Part Book as used for 248-270-302 6 cylinders from 1955-59. It sounds like perhaps the GMC listed part from Jim Carter might actually be one that would fit your application.

The spacer rings are listed for all applications.

Thanks so much. Very good information. I ordered the one from the filling station. I still don't know what the spacer rings are for or how they are used. Thanks for helping me with this.

First, yes, the 230, 250, 292 cam thrust plates are a different size then the 235/261 thrust plates. The 235/261 plate is .187 thick while the 230-292 cam thrust plates are .139 thick. Both are steel and both usually have four small depressions on the plates that are meant to sort of accumulate oil for lubrication.

With respect to a source for a 235 cam thrust plate, the pioneer number is PG213X for both the plate and the spacer. You might try Egge Machine for the 235/261 plate. They often have them available.

As for the use of the spacer ring, the spacer ring is beveled one one side. This bevel accommodates the machining filet at the snout and front journal. Allows the spacer ring to sit completely flat against the front cam journal.

The spacer ring is slightly thicker than the thrust plate. The hole in the thrust plate ID is just a tiny bit larger that the OD on the spacer ring and the clearance essentially allows the spacer to move with the cam without damaging the thrust plate. So the order of install is spacer with bevel facing the cam, thrust plate, then cam gear. When you install the gear, the gear will press right against the spacer and not the thrust plate. So you have the appropriate amount of clearance between the cam thrust plate and the cam gear.

The above is 100% for 56-62 235/261 motors and the last 63 235 motors with respect to the spacer ring. I am near 100% certain it’s correct for the 55.2 motors.

The 55.1 and earlier motors I am not at all certain the spacer ring was used. I have seen some literature over the years that suggest that a spacer ring was not used and that you set the distance with a feeler gauge while pressing the gear on. Whether that is accurate or not I do not know as I have never messed with a motor earlier than 55.2.

Does the thickness of the thrust plate really matter, as long as the proper end play is established by the spacer ring? A lot of these obsessive/compulsive concerns about using exactly the right part number item can be disregarded by anyone with enough brain cells to rub together to do some accurate measuring.
Jerry

Thank you for the detailed information. I am printing it out and adding it to my tech data for the 235. I ordered the thrust plate from the Filling Station. So I will see how it goes.

It does. The thinner late model thrust plate has a corresponding thinner spacer and thus the 235 cam gear would sit closer to the block and thus out of alignment with the crank gear. The 230-292 cam gear is also different than the 235/261 gear, presumably to accommodate the thinner plate and alignment as I am fairly certain the crank gears are the same.

Hey Jerry, what's your procedure for getting the correct clearance on the thrust plate. I need all the help I can get!

Measure the thickness of the spacer ring VS the thrust plate, and file, grind, or sand it to establish the proper end play- - - - -usually around .005". Just enough to keep the cam from walking fore and aft and changing ignition timing by altering the rotation of the distributor gear. I use a magnetic chuck on my lathe, and a tool post grinder.
Jerry

I have build a lot of these engines over the years, and never once did I ever have to adjust the spacer ring. The specification is .001 - .005 so a pretty good spread. But certainly no harm in measuring ahead of time as you only get one shot at installing the aluminum timing gear.

Just like every other clearance in an engine- - - - -"measure twice- - - -cut once!" I'm about to alter the fit between the cam and the timing gear to get a snug slip fit and use a bolt and a thick washer to hold them together. Then I can use an offset Woodruff key to tinker with cam timing during dyno runs. Advancing the cam helps low end torque- - - -retarding it helps high speed HP. That's what the computer controlled variable timing cams do on modern engines.
Jerry

There is new project for you Jerry, Stovebolt with VVT!

It would be possible- - - - -"There's no substitute for cubic dollars", though!
Jerry