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I have two questions-
1) I have my 427 back from the machine shop, now bored to .060 over. My machinist said I should put in a Torrington cam bearing or else my block will be trashed. It's a fairly stock L-36 with flat tappet hydraulic lifters and I have had a flat steel washer in the slightly machined block bearing surface so the thrust washer sits flush with the block. I know the cam is always pushed backwards into the block due to the nature of the grind but my surface doesn't look like it's all chewed up. I notice there is no tang or groove to keep the washer from spinning, but does this represent the dire picture painted by the machinist? I've attached some pics to see the current surface condition- there is a slight groove on the right side that can be felt.
2) Some of the new cam bearings have marks on them- it nothing can be felt where those marks are, will they be fine or should they be spotless with no visible marks?
the front of the block thrust face has been machined. they are usually flat with the face of the block. i believe that is what he means. he now must have something there. the standard setup.
do you know the depth it is machined to? if not, find out. this thrust washer may be an option. https://www.summitracing.com/parts/c...saAiiwEALw_wcB the more i look at this the less i like it. the oil hole in the front cam bearing. the front bearing is now offset back the amount the block is machined. i would think there would be a step there and oil to the front bearing may be cut in half. thrust bearings are usually a roller cam thing. the cam pushes forward in a roller setup. the lobes are cut at a tiny angle so the lifters push a flat tappet cam to the rear. the OE roller setup in later chevys uses the 2 bolt holes in your block face. and there is a step in the cam to go through the retainer plate. like this. you need to find out what timing gear and thrust bearing or bushing goes in that recess, and you need to inspect the front oil hole to see if the bearing has to be pulled and the hole elongated to line up with the passage in the block. or better yet replaced and drilled correctly for your block as those bearings are not meant to be pulled and reinstalled.
Last edited by derekderek; Aug 14, 2022 at 06:43 PM.
DerekDerek-
you are correct in noting that the block has been machined (I mentioned this in my post but I think this was done 30 plus years ago). I had a .030 thrust washer riding on that surface (and is flush with the block) but my machinist is saying that I need a Torrington bearing to save the block. He seems to be usually spot on with his analysis but I thought I would question this recommendation with the experts on the forum. The oiling hole lines up directly with the passage and I can clearly see all the way through to the main bearing. I also wanted to know about visible marks in the new cam bearings- are they an issue if they can't be felt with a fingernail or are they fine as long as there is not a raised portion anywhere?
Thanks so much for your input!
Kirk
That block was already trashed at some point..hence the machine work and shim. There's nothing wrong with that as long as it ends up with the cam gear aligned properly with the crank gear.
Interestingly, I just performed this mod on a Dart 540" I was building today. I've done it on every big block I've built for years. It eliminates the issue by keeping a feed of oil directly to the cam gear face. In your case, the shim could keep spinning against the block and continue to chew into it I suppose. I wonder why you couldn't install a couple of flush pins into the block to keep the shim from spinning?
Or, you can get timing chain sets with the bearing where the gear is made thinner to let it fit. I'm not real wild about all those needles in there...but they do seem to work.
If you could keep the shim from spinning you could drill through it like this and make it bulletproof. This pic was of my 540 after 20 years of running with solid rollers (near .800" lift and springs to match) and lots of oil pressure.
As far as any marks on the cam bearings...they are forgiving of minor scratches etc. Look for real wear on the lower sides and replace if excessive.
also, with a roller bearing in there, is that block face supposed to be the rear bearing race? and the cam gear the front race? because that block surface is not very well finished. i would much rather see a bushing spinning or fixed in place against that face than roller bearings. what about welding it and machining it back to where the face used to be and really should be? and i am glad Jim weighed in. i am no authority on this subject.
427 Engine assembly advice needed
