Caution, cam washer bent!!

[Lee Thompson]

I was setting the cam end play on a billet roller (.005). I purchased the hardware for the front of cam from PT&E. ( torrington bearing, holder and cam button only). My measurement kept changing. The machined washer that goes against the distributor drive bent in to where it was touching the end of the cam.
I believe the torque for the bolt is 55 ft. lbs.. I was using blue loctite and going to 60 ft. lbs.. Maybe the extra 5 lbs. was just enough to bent it in, not likely. It appeares to be machined out of cold roll steel. Some what thick( didn/t measure the thickness but roughly .300-.350). I had an old original Buick washer that they used in earlier years (350 cu. in eng.) used the same front set up. I used it and it did not give. It is made like the big washer used on the front balancer. And appears to be harder than the PT&E. Maybe something to look out for. As most people who run a roller know the front of the cam has to be cut back shorter than the distributor drive. Anyone else run into this?

 

[Louie L.]

Lee,
Thanks for the heads up. What did you pay for bearing , button ect?

 

[Lee Thompson]

prices

TNDO450--Torrington Bearing Cam Button---$67.73
RTHR--------Roller Thrust Bearing Assembly---$49.95
They show the essentric and distributor gear but would not sell the gear to me. I located some used gears and essentrics off a 350. I have one extra. Also T A performance sells used ones.

 

[TurboTR]

Yeah in fact my engine guy made a custom, extra thick, tool steel washer for this. You would think that a soft washer there and loss of clamp torque could be a real problem. Maybe a factor in some of the reported key breakage?

TurboTR

 

[Lee Thompson]

cam washer

I didn/t have this tested, so I have no idea what hardness it is or what steel was used. All I know is mine bent at 60 ft. lbs.
Something to look out for!!!

 

[EightSecV6]

Sounds like the nose of the cam was shortened too much, there should only be a couple thousandths difference in depth between the nose of the cam and the outside edge of the distributor drive gear. If the other washer you put on does not give and there is an air gap between the washer and the nose of the cam, it will come loose loctite or not.
Bill Anderson

 

[Ron Tarabori]

Cam nose

I've had a few cams that the nose was a little short on. I just dig through the junk box and find a washer that will fit inside the gear and is not to thick but brings it close to flush and torque it up. I've had several ASA cams like I use in my engines that were short on the nose. Even with the gear with the recess cut in it. Ron

 

[Lee Thompson]

cam

The cam was cut .010 short. Looks like I need to cut out a .008 shim and use as a filler. What torque value is sufficient and is loctite OK? This is my first roller cam. Is there anything I should do? Thanks

 

[GNXClone]

I've seen two kinds of dist drive gears. One kind that is flush where the washer goes and another kind that has a recess cut for the washer to sit in.

I know someone with a few NOS dist. drive gears if anyone is looking for one.

-Mike

 

[Ron Tarabori]

cam nose

45 to 50 lbs with blue loctite should do it.

 

[The Radius Kid]

This topic should be posted in the general tech section as well.I've had several discussions about this very thing with a couple of very respected board members.Glad to see it was brought up here by someone who has one of these time bombs.The fix the member used was to make a new washer out of good material and get a grade 8 bolt.I believe that the washer was heat treated and hardened as well.IMO,from what I've read about these things,the bolt is *supposed* to maintain a *preload* or stretch on the front stack of gears.If the bolt is too weak of a material,or the preload washer is too soft,one of the two will "give" losing preload and putting all the drive stress on the soft key[if you're still using it].Of course over repeated cycling,the key gives and eventually shears or breaks off,leaving the valves to meet the pistons in a rather nasty manner.Ask Mark McCoy.
Considering the jobs of the respective gears in this type of app.,a tougher key and a better bolt and washer are in order.Not a filler washer to close the gap.That might help the washer dilema,but not the issue of the bolt.

 

[EightSecV6]

A little bit of preload is good (.002-.003) .010 is too much, we run spring pressures at about 730# open and spin the engine to 8000 rpms plus and have never twisted or broken a cam key. It is very important to be familiar with these engines before you jump into assembling one as it seems almost every one is a little different. You can learn alot by simply inspecting all of the parts when tearing a stage 2 Bush engines down, that is where alot of todays technology is derived from. A GOOD Busch engine usually ran 35,000.00 plus for the successful race teams.
Bill Anderson

 

[Ron Tarabori]

cam nose

Dont know what you guys are running for bearings on the nose buy all the pieces I use the bolt is part of the assembly. You don't have a choice. Some of the cams I've seen have been as much a a quarter inch short on the end. I prefer to fill the hole to within a few thou. I've never had one come loose. Like Bill said every engine and engine builder had its own little differences. If it doesn't look right to you dont put it together till you're sure. When one of these comes apart at 8 grand you dont get to save much.

 

[The Radius Kid]

Originally posted by EightSecV6
A little bit of preload is good (.002-.003) .010 is too much, we run spring pressures at about 730# open and spin the engine to 8000 rpms plus and have never twisted or broken a cam key.
Bill Anderson

So,who's cam package are you using?

 

[10SV6]

Ron,
Have you used a cam that needed to have that much (1/4 ")space taken up at the snout end ? I'm going to be taking the front cover off tonight and I'm expecting to have around that much to center the cam gear.

Thanks
Paul Thompson

 

[Lee Thompson]

cam washer

Thanks to all who replyed. I am confident I have it correct now. I measured the thickness of the washer today. (PT&E and the old Buick one both were ---.150). My cam was .011 short of the end of the distribitor drive gear. I cut a .008 washer out of shim stock, leaving .003 difference. Used blue loctite and torqued to 55 ft. lbs. Altho I have a .500 lift cam and drive my car some, probably stay 6000 RPM and under, If this will stay on an 8000 Rpm--1000 HP eng., I should be SAFE. I can see where all the air space needs to be taken up to eliminate any chance of the bolt reducing its torque value.. Thanks Again---Lee

 

[The Radius Kid]

Would it fair to assume you replaced the bolt as well as the washer?I heard they're pretty weak too.

 

[Lee Thompson]

bolt

No, I do not see any reason to replace the bolt.

 

[The Radius Kid]

Any idea what grade the bolt is?I was told by a "source" that it looks like something out if Home Depot.If that's the case and it's of an inferior grade,it could eventually loose it's preload due to stretch and cause the same problem as a cupped washer.

 

[Lee Thompson]

bolt

Don/t know what grade. This is not an ordinary bolt as it has threads on one side of the hex to go into the cam ( 1- 1.250 in. ) amount of thread. The outer end is a shaft that holds the torringtion bearing and roller that butts against the front cover. It has a grove cut in it for a snap ring to hold all the pieces on. The bolt is much heavier than the washer. Definnately not from any home improvement store.