The Stovebolt Site Forums The Shop Area Engine Shop 235 Fiber Cam Gear change?

To the point. Do I replace the Fiber cam gear on a rebuild? How long do they last?
Thank you for any insight.
Motor 58' 235. Unknown history.
**Update. NOS thust bearing, Aluminum Cam gear, steel crank gear ordered.
Just waiting on Aluminum Cam gear to be delivered.

No, use a timing set for a 261 Chevy Truck motor. Steel crank gear and aluminum cam gear. Way more durable.

Dragsix,
So get away from Fiber gear, period?

Fiber gears are quieter, but aluminum lasts a little longer. Unless you're racing or planning to run a heavily-loaded truck wide open all day, either one will outlive the average hobbyist. There's not enough difference to matter, as long as you start with a new gear on both the crankshaft and the cam. Don't trust the old fiber gear- - - -replace it with whichever style cranks your tractor.
Jerry

Jerry,
Not a hot rod not hauling Heavy loads. Just small Feed runs for the farm. Fiber quiet compared to aluminum? You can hear the difference when running?
Thanks!

Some people claim they can hear a difference, but I've never noticed it on the engines I've built. Of course, I grew up building flathead Fords, and there was no choice- - - -cam gears were all made of aluminum. There's a little bit of gear hum from both, so unless you've got very sensitive hearing just pick whatever suits you. My hearing got sacrificed to B-52's, race engines, and deer rifles years ago!
Jerry

Great, and confirm you replace cam & crank gears as a pair?
Thank you

Yes. Both gears are pressed on so with the engine in the vehicle they're a little hard to change. The steel crankshaft gear doesn't show as much wear as the cam gear, but replacing them as a set is considered to be the best practice. The fiber gear usually breaks as it's being removed, leaving the steel hub on the cam. Use a big chisel and a hammer to split the hub over the Woodruff key, and it will slip off easily. The crankshaft gear can usually be removed with a 2-jaw puller in one piece. Reinstall the crank gear with a big hammer and a pipe nipple, being sure the timing dot is facing forward. Heating the cam gear to about 250 degrees in a toaster oven will make it slip onto the cam a lot easier, but be sure to remove the fuel pump and have a helper hold the cam forward with a pry bar as you drive the heated gear on, also being sure the timing dot is aligned with the crank gear as it goes on. Work quickly before the gear cools off, and be sure to handle the gear with welding gloves to avoid burning your hands. If you don't hold the cam forward you could damage the valve lifters, the cam lobes, or knock the soft plug out of the rear of the block behind the cam, requiring the engine and the bellhousing to be removed to reinstall it. Have fun!
Jerry

I have used the truck timing set for close to 40 years now. I was looking at the copybook that I keep my notes on the 235/261 motor builds I have done over the years (yes old black marble, first entry for motor No. 1 is August 1979, there are 47 motors after that) and I used the truck set on all of them. About a third were restorations, the remainder were modified motors. Some have said they are noisier, I have not heard much difference between the two. The fiber gear was the predominate gear used in these motors from the factory but after a lot of use they could and did self destruct usually resulting in a few bent intake valves and other assorted carnage. The truck set is just a more durable part, 2516S is the common aftermarket part number that a number of manufactures use. They run in the $50-70 range new although I have paid less on ebay for RNOS sets in dirty boxes. As for installing the cam gear with the cam in place, as Jerry said, it can be done. Me, I am a big chicken, so I have always pulled the cam out of the motor to install the cam gear. A couple of the gears I have had over the years have been somewhat tight even after heating them up. I don't know that I could have gotten those gears on with the cam still in the motor so use your best judgment. The aluminum cam gear is not one you can remove and reinstall and maintain the necessary sort of interference fit.

I apologise for not putting in the top post. Engine is out and in pieces. Just got the block back from machine shop. So it should be easier to install both gears.
Again, Thank you.

Mike, in a shop environment where a timing gear set got installed before lunch for flat rate manual pay, we got innovative about getting the job done in a timely fashion. We didn't have the luxury of doing things like pulling the cam.
Jerry

I'd change over to the aluminum Cam Gear .

Below......ALL GM NOS parts


There's one on ebay NOW........go to ebay & in the search box.......type........3835473

It's for sale @ $44.50 OR Best Offer

ebay photo

https://s26.postimg.org/5ul6aygm1/3835483.jpg


There's also a Crankshaft Gear on ebay NOW

It's for sale @ $17.00 OR Best Offer

Go to ebay & in the search box....type....3836605

ebay photo

https://s26.postimg.org/xtfc28q2x/3836605.jpg


You'll also need a Thrust Bearing & the Spacer

PIC......from my files

Thrust Bearing & Spacer ( GM # 3707916 ) is a scarce part to find

https://s26.postimg.org/si0fhjr5l/Cam_Thrust_Bearing_GM_NOS_3707916.jpg

Go to ebay & in the search box......type......3707916

There's a GM NOS Thrust Bearing with the Spacer on ebay NOW @ $20.00 plus shipping


Here's a PIC of a timing gear set I purchased back in 2013 . It sits on my spare parts shelves .

https://s26.postimg.org/sr2ll766h/Cam_Gear_Crank_Gear_Unit_2.jpg


George
'54 3600

I hear ya, lol. I am still chicken, lol.

btw, the Pioneer thrust plate for the 235/261 is PG 213x. For whatever reason, they (along with neoprene rear seals) have gotten to be a bit of a pain to come by lately.

I grew up in a shop environment in the 1950's where stovebolts were not fragile wallflowers driven by snowflakes with lace on their drawers- - - - -they were rugged daily drivers built to take all sorts of abuse at the hands of semi-literate owners and shade tree mechanics, and still keep on truckin'- - - - -It's amazing how fragile these same vehicles have become after a few decades of sitting in barns and sheds around the country! Maybe it isn't the trucks that have changed- - - - -just possibly it's the drivers and mechanics?
LOL!
Jerry

54 3600,
Thank you.
I was just starting to look for NOS parts.
When would a Thrust Bearing be replaced? Every time Cam gear is changed?

Not trying to hi-jack the thread, but, I am replacing the cam on my rebuild. Old timing gear set is on the old cam, I need to put it on the new cam. Will that be a problem of fit or wear or anything? I figure I can just press if off the old and put it on the new.

Shaffer's 1950 ,

You say , When would a Thrust Bearing be replaced? Every time Cam gear is changed?


I kinda' think you are trying to self rationalize a reason for not finding or buying a new Thrust Bearing .

I have no dog in this fight......so ,as they say , ' have it your way ' .

It makes no difference to me whether you get a new one or ' nickel & dime ' yourself & use the old one .

The Thrust Bearing ( support ) prevents the camshaft from moving & rotating in all directions

except the for rotational motion of the camshaft .

In my opinion , it is critical in importance to have a new camshaft Thrust Bearing .

It's just my way of looking at the choice of new -vs- use the old one .

It could make the difference between a good running engine & a not so good running engine .

It's your choice.......just hope you make the right choice .

Other's will be along with their opinion's .


George
'54 3600

George,
I was asking when the Cam thrust bearing gets changed because I have no idea. I will order one. I am not short cutting the rebuild in any manner. This is just all new to me. Thank you.

A repro Thrust Bearing & Spacer is being sold by

The Filling Station

https://www.fillingstation.com/catalog/flippingbook/files/assets/basic-html/index.html#317

Filling Station , pg.317 . Part # FS - 625 $24.95

https://s26.postimg.org/75k7bcgyx/Filling_Station_page_317_FS-625_Thrust_Bearing_and_Spacer.jpg



Another photo of a GM NOS Camshaft Thrust Bearing & Spacer

https://s26.postimg.org/j7fl5mfyh/Camshaft_Thrust_Bearing_3707916.jpg


Take a drive over to: Antelope Valley Chevrolet in Lancaster , phone: 661 - 952 - 2300

Go the parts department.......& ask them to do a nationwide part search to see if they can

find you a GM NOS Thrust Bearing Kit - GM # 3707916


George
'54 3600

That is tremendous (I did not know the filling station sold them. I would however, call them first because it seems everyone else who had them listed for sale is now noting that they are out of stock) and the price for the new thrust plate is about right. I have reused them in the past but I prefer to install a new plate on each build.

As to the question of whether you can reuse the gears, no, you shouldn't. The crank gear would be the more likely candidate given the balancer will hold it in place but the cam gear I would want new because it relies on the interference press fit to stay on the cam snout. I am sure reusing those gears has been done in the past but its not a best practice in my view, emergency maybe. Order yourself a new set. They are not that expensive compared to the cost of repairs if the re is a failure. The last thing you want is for the cam gear to start walking forward on the cam snout.

The metal timing gear set is available from Rockauto for $44. Melling 2516S.

Matt

The 230/250/292 thrust plate looks similar to the 216/235 plate, but it's a different thickness. I believe it's a little thicker and won't allow the gear to be pressed on far enough without tightening up. I can see nothing wrong with reusing the thrust plate and spacer, if you can get the assembly apart without breaking the plate. In a few decades of working on these engines, I don't recall ever finding a measureable amount of wear on a thrust plate. I've seen a lot of them broken by people trying to remove the gear from the cam. It's possible to face a few thousandths off the 250 plate and make it work on a 235, but it requires a magnetic chuck and a tool post grinder on a lathe, or a similar setup with a surface grinder.
Jerry

'54 3600. George,
Again thank you. I have my eye on a NOS cam thrust bearing now. If it falls through I will hit my local Chevy Dealer or Filling Station.
I ordered a NOS crank gear and trying to grab a NOS aluminum Cam gear now.

Shaffer's 1950 ,

Sounds like a good plan . Keep everybody posted as to your progress .

You have a lot of people here ready & willing to help you .

If bidding on a part on ebay don't keep raising the bid . Wait till the last 20 seconds

of the auction and throw up the winning bid .

Good Luck


George
'54 3600

George, 54' 3600,
I just got (bought) the NOS Cam thrust bearing! Just need the Aluminum Cam gear..then progress.
Thanks.

You must have bought the one on ebay .

https://s26.postimg.org/r39vpe86h/bearing_and_spacer.jpg

Good purchase on a GM NOS hard to find part .

I like this version of the Thrust Bearing with the oil grooves .

It was an improvement over the original design that had no grooves .

Looks like it needs a little clean up . Do it gently !

No sandpaper or rough stuff .

The cam gear will be easy .

Keep up the excellent hunting .


George
'54 3600