Just going over the final assembly of my BB. I have been thru the theads and I am still confused. The cam is a hydraulic flat tappet. The lifters are sitting on the lobes offset to the front of the engine. From what I gather, this is normal as the cam moves back when running. Also, when you push the cam rearward the cam timimg gear is not flush or parallel to the crank timing gear. When measured the cam timing gear is .025 to far to the rear of the engine. Is this normal? I would tend to think that the 2 gears should be somewhat parallel to each other when the cam is moved rearward. I also have a thrust washer behind the cam timing gear. Do they make different thickness washers? This is my first engine, would like to do it right the first time.

Opps, forgot to mention, the distributor is not in. Could this be why the gears are not flush?

no, the distributor doesn't affect the location of the cam.

How about a little background? Is this a big block? do you know if the cam thrust area has been machined to repair an earlier problem? this is not uncommon on big blocks. Are you using a timing gear with the back machined for a thrust washer?

.025 is a little much, needs to be fixed. Can you pull the timing gear, lay a straightedge across and measure the distance from the straightedge to the cam thrust surface on the block? Actually should be flush.

The Camshaft end play is not all that critical because all hyd and solid flat tappet cam lobes are ground on small taper so the when lifter made contact with that cam will keep the cam thrust back toward the block. Now Roller cam do require a thrust bumper between the timming cover and cam to keep the end play at least .006.

Yes 1981 454 Big Block, 427 crank, CompCam #11-246-3. This was a fresh rebuild that I didn't do. The fella said it was ran for break in. Not to leave a stone unturned, I have disassembled the motor.

OK, Crank timing gear face to Cam timing gear face rotated 120 degrees and pushed to the rear I get readings of .042, .036, .037.

Timing cover surface to front block cam boss is about .296, it has a co-bore in it that is .042 deep that the .031 shim-spacer fits in. Can't tell if timing gear has been machined or not. I have pictures of the whole deal but have no way to post them. Send me an email smentecki@wi.rr.com I can send the pics if need be.......thanks

one way or another there needs to be enough shim or spacer to bring the cam thrust surface flush to the front of the block.is the back of the gear machined for a bearing or spacer?

What about the front cam bearing? is it sticking out of the thrust surface? You'll need to check that the cam bearing is not installed flush, if it is the oil hole will not be aligned with the groove in the block, bad things will happen.

post your pics up on any pic site and link to them. picasa, photobucket, cardomain, youtube, etc.

OK pic links below. The cam bearing is recessed in .031. I can slip a wire through the hole, is this good. Also I messed up on the timing cover surface to cam boss, its .183 + .042 to the co-bore surface. Tom, I'm still confused as how this should be fixed.

http://i270.photobucket.com/albums/jj115/malmech12/IMG_4139.jpg

http://i270.photobucket.com/albums/jj115/malmech12/IMG_4138.jpg

http://i270.photobucket.com/albums/jj115/malmech12/IMG_4137.jpg

Any chance the cam gear, crank gear being of differant manufacture? Is the crank gear on all the way?
Those are deep wear patterns on block. Probably would not hurt to have a small oiling hole in one of those galley plugs.

Big possibility on different gears. However, looks as if the cam area has been machined? Is there a vendor to purchace different size cam spacers?

good pics.

that's not a "co-bore", that's extreme wear on the block. Does this engine have a Hi-Vol oil pump on it?

the existing shim, is it smooth on both sides or does it have a lip on it?

The old hole in the lifter galley plug deal won't help, the oil squirts out onto the back of the timing gear and gets thrown off to the outside. A hole can drilled into the block from the thrust surface into the oil galley that feeds the front cam bearing, but this is not a job for a hand-held drill.

Looks to me like the front of the cam bearing has been eaten off by the timing gear as it worked it's way back.

This really is kind if nasty. The engine needs to be torn down to the bare block and fixed. This means machining the worn area down to clean, in a larger diameter than the wear surface back of the cam gear. then a spacer can be milled from a suitable material in a thickness to compensate back to flush with the front of the block. The new cam bearing will need to be installed carefully so the oil hole will line up. Don't run a Hi-Vol oil pump on the repaired setup.

I've seen one setup like this where they milled it down, doweled a spacer on bolted to existing bolt holes with countersunk head Allen bolts. Then they align-bored the cam tunnel to the next oversize and installed the oversized bearings. I guess the thought was to provide support to the front of the cam bearing as if the whole thing never happened. I'm not real sure I'd go to that length, might be cheaper to find another block.

no, the spacer is smooth, and it is a counter bore

Sorry, doesn't look like a counterbore to me, looks just like every BBC block with nasty thrust wear I've seen. Wouldn't be the first time I've ever been wrong though.

Why would anybody make a counterbore there anyway? Does the existing shim fit correctly in the counterbored area, not touching on the outside edge? outside edges of the shim square and sharp? Maybe you find a thicker shim?

Is the oil still centered in the cam bearing? Is the cam bearing hanging out the back of the bore? The front edge of that bearing looks to me like it was hammered.

The edges of the spacer are sharp, no burr. The spacer fits correctly. The cam bearing hole lines up to the block hole, I was able to fish a wire into it. The bearing doesn't hang out the back either. Front of the bearing has a chamfer. Al looks ok. There are slight ridges in the surfaces, nothing as in "smoked". Think I can get away with a thicker spacer? Who sell spacers of this variety? Thanks Tom

I dunno. I blew up the pic and the outside edge of the counterbored/worn area is pretty clean. I can't think of any reason a machinist would counterbore that surface to a depth that he didn't have a shim for??? Doesn't make any sense to me.

That is not a counterbore, it is wear.
It is how the front of the block wears
It needs to be machined flat & used with a shim that will bring the surface back to the unmachined spec which is the surface where the two holes are.
If it is .042 & flat I suppose you could install a .042 shim if you can find one but the correct procedure is to machine the front of the block the depth of a known shim not just machine the block & hope you can find a shim of the correct thickness,,,,
The gears need to line up. within about .005"

Thanks for stopping by Mike. Oddball deal to find on a newly built engine.

malmech, don't forget about that Hi-Vol oil pump deal. you really don't need a repeat on this.

Good clear pictures.

You need to get a couple different shims and take it to a machine shop, i would groove the front cam bearing or mike's way of drilling a small hole to the oil galley after machining.

Question for mike and tom,

We do mostly small blocks and they dont have as bad of a wear problem here, How would a coating on the block, a lubricating coating from polydyn, techline etc help this wear problem? I have never done this but just a thought on these rat motors??

I don't know or understand why BBs have this problem and SBs don't. I really don't see any significant difference between the two in this area. I can understand with a BB when there's a HV/HP oil pump, those things are big. But, they have this issue as stock production.

Possibly the guy before me machined it for the .031 shim that is there? Can you run more than one shim? I have 2 hardened .041 shims here that are the same size. I could surface grind one to fit to specs. I need somewhere in the area of .071 to achieve where I wanna be with the timing gears. Or is this not recommended?

Couldn' I just skim cut the crank timing gear .041? Drill the oil hole, and run what I got?

I am with Tom and Mike on this one.

I had a timing chain break at 6800 in high gear.

Upon disassembly my cam gear, block and shim parts looked much like yours. The back of the cam was trying to weld itself to the rear cam plug too!

You got the opportunity now to get it done right.

>> "Couldn' I just skim cut the crank timing gear .041? Drill the oil hole, and run what I got?"

No, you need to fix it so that the cam is properly located in the block. moving the crank gear back to match doesn't help. See Sandy's note about the rear cam plug and the broken chain. Also, if the cam gets too far back the lifters will contact the adjacent lobes and start grinding a new pattern.

You'll notice Mike has corrected me on the depth measurement deal, measure the depth of the wear from the undamaged section of the thrust pad, out near the bolt holes. one way or another you need to get a shim or spacer that will take up the space and mill the damaged section flat.

So skim cut the co-bore face for cleanup? Then shim, so the cam timing gear is even with the crank timing gear? Where can you buy these shims? Thanks for all the input here.

cut the bottom of the worn area so it cleans up or nearly. measure the depth from the undamaged areas near the bolt holes. find a shim that thick or slightly thicker. You've got to make so the fron of the shim is flush with the undamaged areas.

Do you have access to quality machine shop tools like a mill and lathe? If so, you can DIY the deal. load the block up into the mill standing on the bell housing flange and mill the co-bore. while it's up there use a tool to drill a small hole from the face of the co-bore into the oil passage between the main and the cam. find something to use for shim and cut it to fit on the depth, ID and OD. Strip the block to bare iron, bake and blast or vat or whatever, put it back together.

Sorry, I don't know where to buy the shims. It's been over 20 years since I had to fix one of these and that was in another state. Contact Wolfplace or Bill K, both are excellent machinists and running their own shops.

Gotch ya! But I still will have to have a thicker shim than flush. I will need around .071 or so to bring the timing gear flush with the crank gear within the .005 tol. As mentioned earlier. This may be a miss matched set. Best thing maybe would be to buy a new timing set. Upon inspection, the oil pump is a HV type Melling. I have read the threads on this and will also install a stock style pump as recommended.

Thanks again for all the input here. It has been of great help.
Happy New Year to all........sm

I used to use Cloyes wear plates for this, here in the catalog, page 12, there are several listed in the 9-201 , 203, 220 bearing or 220B .150 wear plate. Hope this helps. I still have a few of the 201's in my tool box.
http://www.cloyes.com/pdf/Cloyes_2007_HP_Catalog.pdf

I think I may have it handled. I spoke with a local race guy in the neighborhood. He's got a small boring bar and surface grinder. I showed him the pics., and his solution is to dust the worn surface and space out the cam to the correct tolerance to the crank sprocket using the Cloye's bronze .150 spacer. Grind it to the correct size. He also added that if the timing set is not matched, which I have a feeling there not. Add a Cloye's true roller set to make sure this will be a done deal, and not some hodge podge fix. He also will drill a 1/32" hole in the block spacer surface.

Would it also be a good idea to drill a 1/32" hole in the gallery plug? Or would this be too much oil flying around?

If you have a local shop that cam machine the cam thrust surface all you need is a Comp Cams part number 3110TB. Measures .140" thick and brings everything back to original specs. This leaves you use the cam bearing without modifying it also.

Also gives you a roller bearing surface for the timing set in place of jsut a thick shim.

Harry P.Hunter

From the timing cover surface on the block to the cam wear plate surface boss on the block, is this flush, or is it set back? Anyone know the dimention from these surfaces? I have a feeling the trust surface was machined.

From the timing cover surface on the block to the cam wear plate surface boss on the block, is this flush, or is it set back? Anyone know the dimention from these surfaces? I have a feeling the trust surface was machined.

The original surface where the 2 screw holes are located is about 3/16" down from the timing cover flat.

Only the small blocks are machine straight across.

Harry P.Hunter

Great! I'm good to go. Mine is .183.

one last question. When I measure for the spacer should the crank be pushed back, or forward? Sorry to pester.....sm

one last question. When I measure for the spacer should the crank be pushed back, or forward? Sorry to pester.....sm
=
How much is the crank moving?
It should only be about .003-.007
Honestly should not make any difference which way you measure it.
But to be picky,,, :D
I would just split the difference
If you measure it all the way back leave the cam gear a couple of thou proud
Forward, leave the cam gear a couple to the rear.

Crank endplay is .008 which is max in the book.