I was rebuilding my 400 small block and found that my timing chain was rubbing on the block. Do I need a thrust washer or spacer behind the cam gear to keep it away from the block?
Unless there's a bunch wore off the block or the back of the timing gear,that should never happen.....Try another timing set and see if the chain is running straight...........
Dunno, I believe I had to grind some clearance in that area years ago on a 400 sbc. If I recall the instructions mentioned checking it. A straightedge will tell you if the sprockets are aligned correctly.
There are no signs of wear on the block or the back of the timing gear. Would a sloppy timing chain allow the cam to walk back? The cam lobes and lifters have normal wear.
I don't know if this is your issue of not but worth a look at this info When using an early-style cam nose and timing chain in a late-style block, grind the thrust-plate boss (arrow) down about 0.100-0.150-inch for upper sprocket clearance. Double-roller chains machined to clear the boss are available from the aftermarket, but they only mate with the late-style snout and still require an early-style front cover.
I run 400's and never ran across this however Moose's post makes sence. Here's a tip! Drill a 1/16" hole in the block at 12 o'clock in the center of the thrust area. This will allow a trickle of oil to lubricate the thrust area of the cam gear preventing the wear that is common on SBC.
Every SBC in the world needs clearanced there when using a double roller set....some set brands more than others/some blocks more than others.....but none the less we do every one when preping a block for a build. This is nothing abnormal......also just straight edge your gears and that will tell you you dont need a shim exept for a thrust washer IF the gear is designed to be used with one. And no a link set is not better than a tru-roller timing set. Tony
I run across this all of the time. Certain blocks need ground for clearance. When I have the blocks on the boring bench, checking this is a process I do. As far as the gear alignment goes, always put a straight edge on the upper and lower gears when installing them to check for the correct fit >>>>.
well some years ago ...(68-73)<--- thats like 100 years ago lol we used chevrolet morse pre-67 silent chains and cam sprockets with aluminum casting w/ nylon teeth, and all that HELPED with vibration harmonics,we checked and change them often. Core shift on some Small Block Chevy engine blocks is a possibility. We changed cam sprockets , clutch disc's and rear gears regularly..
That was called having repeat business every 60,000 miles. I've known mechanics in the past that put plastic gears back in for exactly that reason. So the car would come in in another 60K for another timing chain job. Back to the original subject of the thread. I've run double roller chains in several of my small blocks and have never had to make clearance for the chain (yet) the 350 in my 71 daily runs one right now but it is a 78 engine with stock cam. As one of the guys on the first page who I believes builds a lot of engines said, it is on a block to block basis and each needs to be checked. Like everything else on an engine, you check as you go and don't just slap things together as fast as you can bolt pieces on.
sorry didnt make my self CLEAR that was on / in a GAS class drag car R P M 'ing up to and including 9thousand rpms... o0Ps not entering in to a narcissistic pissing match today ah ha ha ha
On my 400 I used a Dart SHP block and Comp Cams hydraulic roller that uses a cam plate to keep it from walking. Their double row chain and gears are made to work with that setup. No clearence issues. As far as drilling a hole for lubrication goes I think most stock and replacement cam gears have three slots across the wear surface to let oil flow.
I have removed a lot of the link style chains without removing the gears they are so loose - sometimes on a small chevy they wear throught the timing cover they are so loose, all at about 60-70,000 miles. Great stuff. I bow to your superior grammatical and writing skills. You are a poet wasting your time on this site.
no explanation for the blocks that DO NOT need the hair cut? yes ... some do... but NOT ALL ? the ones that do not need are the off core ones ? ah never mind this thread has run its coarse and needs to closed. we have the answer SOME DO and SOME DON'T.
^^^^^ upon a closer look of the image, it would appear that is from interference and not clearancing. None the less, nothing of concern at this point. Just check clearance when doing your new assembling. Oh, don't forget to install oil galley plug that is missing in the photo.
^^Correction.....Most ALL need clearanced when running a true roller... Henry you just stick with those nylon tooth gears, then you wont have to worry about it..........Oh and dont forget to clean the nylon teeth out of the oil pump pickup....thats usally where I find them.
GOATROPER02 havent used dem nylon gears for 40 years... kinda back at the same time as DaGrump did. and thanks for being here and helping others, as i try to do the same thing.
Grumpy Jenkins ran those silent drive chains with nylon/aluminum gears in his small block 331's and zinged them regularly to 9500 rpm. Double roller timing sets add weight and weight becomes evil when zinging motors. The aluminum/Nylon gear better dampens crankshaft vibration that would otherwise be transferred to the cam. Of course, he was drag racing and inspected the chains regularly, and mentions that the chain was replaced every time the cover came off. They ran double roller heavy duty truck chains in the Grand National engines when durability was the objective. All his little tricks are in The Chevrolet Racing Engine.
The Jalopy Journal
