Big Block Camshaft Sprocket Question

[78BBSTEPSIDE]

Decided to pull the 454 apart for a good cleanup and detail. Upon removal of the cam sprocket, the boss/flange has been machined and a retaining plate has been added. This work was done @ 23 years ago when the motor was rebuilt, only 35K since the rebuild and still runs extremely well. Has anyone ever seen such a repair on a Big Block? Can anyone verify if the new sprocket is the correct one for the motor or is the box mis-packaged? The new Cloye's is a true roller part number 9-1110. Thanks

[VileZambonie]

The retainer was available from GM. Not sure if still is. You can eliminate the retainer and go with a cam button. Summit sells a timing chain set with a torrington bearing. all you need is the lock plate and the cam button. It's dirt cheap I'd go that route. This is what I just did with my 454. I believe I posted pix but I can't remember. The set up you have there looks to me like it's not going to work unless you machine down the cam gear. Then you will have to make sure the chain alignment is correct.

[HAULIN IT]

I agree with Vile, what you have isn't all going to work together. I never knew GM offered these over 20 years ago (not saying they didn't, just never knew of one) When you say "repair" why do you think this, is there something that you know happened years ago? To me, it looks like someone thought it was a good idea & added it. It's hard to tell in the photo, but the cam looks to be closer to the face of the plate than what the thickness of the plate would be (based on the countersunk screws). Have you had the plate off? Is the cam flush with the block & the backside of the plate flat? If so, one option if it's not a roller cam, would be to just remove the plate & install the gear set you have (assuming the thrust surface on the block has not been machined or not gouged up). However, it it's a flat tappet cam, I would be concerned about changing the placement (backwards amount) the cam could move since break-in. Is the cam gear worn? Maybe just put a new chain on? I'm looking at it this way...If you have to change a timing chain every 23 years, is that so bad? It's hard to say about the quality of the chain that was in there (unless you where the one that picked it) there are allot of low quality timing components out there, even 20 years ago. Keep us posted! Lorne

[VileZambonie]

In these pix you can see the early version of the retainer and the later version which I think they changed around 1997 1998 ish.

[78BBSTEPSIDE]

If memory serves me correct the cam had walked around and damaged the surface of the block and therefore the need for the plate. I talked to Cloye's today and they suggested either machining the sprocket or changing the style of the bearing as Vile suggested. I really do not want to take the plate off as it is screwed in and then epoxied, of course the machinist that did the work is retired and unavailable to ask. There has never been a problem with cam and/or bearings, I was just going to install a new timing set while it was apart. I will talk to the machine shop and see what there thoughts are as far as machining the hub of sprocket.  Then other thought would be too find a new chain for the existing gears, however I'm not sure what brand it is, there is a MG stamped on the face of it as well as what appears to be the part number of 8394. Seems to me the shop used Federal Mogul or Sealed Power engine modules at the time, any ideas? Thanks

[VileZambonie]

http://store.summitracing.com/partdetail.asp?part=SME%2D7010&autoview=sku

[78BBSTEPSIDE]

One thing I might add is the plate is a filler versus a retainer, the cam comes out with it in place. If I were to remove it and install the Summit kit with the torrington bearing and button, will this work regardless of the amount of material that has been machined from the block? 

As far as a replacement chain for the existing sprockets, would most any stock same style work with the same tooth count? Thanks

[HAULIN IT]

That was kinda what I was getting at, I couldn't figure how the cam became level with the front of the plate once the sprocket was installed, but could see the wear mark on the back of the sprocket where it was rubbing the new plate looked near flat. So you think the block was chewed up & this was a fix for it? This really seems like a can of worms. Really the only problem is timing chain alignment....the cam was pulled out flush with the new plate in 1985 & has rode there ever since, changing/machining the cam sprocket won't change that fact. One thing that should work is.... put the new crank sprocket on, measure with a true straight edge & machinist rule from the face of the new crank sprocket teeth back to the machined surface (timing cover), then from the new cam sprocket teeth to the timing cover, this would tell you how much needs to be removed from the backside of the cam sprocket. If you choose to use a bearing behind the cam sprocket, the total removed would be less by that thickness. Quite frankly, I don't see any way of buying parts & bolting them on without a trip to the machine shop. Some undetermined amount must have been removed from the block in 1985. Look at it this way...."Joe" removes say .040 from the block the achieve a true surface, finds this mystry plate that is say .250 then puts the cam gear upside down on the surface grinder & removes .290 from the topside. Unfortunately this is ugly. How loose is that old chain that wasn't a problem until you went looking at it? Just a thought, Lorne   

[static22]

You said the work was done 23 years ago so does that also mean the engine has 23 years worth of miles on it? If the idea behind the repair was to use the retainer to get it back to factory specs then you should be fine either way. If the retainer has been in there for 23 years it may allow the cam to come out due to wear that has taken down the retainer to the point where it cannot work as a retainer any longer. Just a few thoughts. I don't know a lot about big blocks.

[VileZambonie]

Walk the cam forward enough to bolt the cam gear on. then look through the lifter bore and see if the lifter will make full contact with the cam lobes.

[78BBSTEPSIDE]

I was able to locate a Double Roller Sealed Power Chain today that fits the existing sprockets perfect. Thanks for all of the input.