My local speep shop and I are stumped on a timing chain issue that I have. Basicly the chain looks steched but it only has about 10k miles on it. The chain fits to loose and dosen't make contact with 2 teeth of the crank gear when the chain is pulled to one side.

Background info: I bought a stock used motor about 10k miles ago and the chain was replaced at that time by another shop (which ened up screwing up alot of stuff) they never menchened anything to me about the chain fitting loose so I'm not sure if it was the motor or if the chain streched. We were thinking that the motor could have been rebuild before I bought it and the mains are line honed and the chain was never shortend.

anyone ever see anything like this before? Any suggestions?

 

Anytime you do a machining operation that moves the crank closer to the cam it's going to add some "slop" in the timing chain. Typically, this machining is not so severe that you can't use a standard timing chain- we're talking a few thousandths of an inch taken off.

Get a fresh chain and put it on. See how loose it is. If it's pretty tight then you just had a bunch of timing chain stretch before, not a basic block machining problem.

Cheap timing chains stretch like salt water taffy. Most of the stretch happens in the first few hundred miles. If you're not spending at least $50 for a timing chain you're probably buying stuff that's inferior quality. Full roller chain. Brand name. Soak it in motor oil overnight before installing (or bake it in the oven at 300* for an hour in motor oil if your wife will let you). Do just about anything you can think of to make sure that chain is thoroughly oiled before the engine ever spins a single revolution.

 

So what chain do you recommend for the LT1. The cloyes 3145 seems to stretch easily

 

Gears

The cloyes or any other brand billet sets are awesome, but not needed in most apps.

Just the cloyes true roller HD version is around $50 and have heard good things.

I am assuming you have no water pump and its vented right? Not calling you dumb, just making sure.

 

Correct!

I did some checking around and found a set that offers the upper and lower gears billet. I believe I will use the chain from before since its already done its strectching and possibly have to use a +5 gear to make up the slack....

Maybe this will keep the cam timing correct..

 

RollMaster makes a nice Billet fully-machined, cam sprocket, and multi-indexable machined billet crank sprocket , their true-roller chain seems to outlast and stay tighter than the Cloyes i've used

a potential source of premature wear/stretch is
cam sprocket -VS- crank sprocket alignment in same vertical plane

if one of those 2 sprocket's plane is more than .010" forwards or backwards of the other, you will get premature wear/stretch

i use a simple method ...a custom length straight edge layed across cam sprocket face ..then measure distance bottom crank sprocket is off in relationship

SBC =
you can fix any misalignment... i use a Canadian 10-Bolt differential pinion shim which i put between crank snout register and back of crank sprocket to achieve perfect sprocket alignment

BBC=
for BBC Chevys ... use 12-bolt pinion shim assorted packet , find correct thickness, use a medium round file to grind a round notch in pinion shim , then slip over keyway between crank snout register and back of crank sprocket

perfect top/bottom sprocket alignment w/proper cam button clearance goes a long way in getting the longest life out of your timing chain regardless of manufacturer !

 

Good post, proper alighnment is critical to chain life and stretch! That's why most aftermarket chains break and factory ones don't.

Bret

 

Thanks Bret , but i forgot to add another very important aspect

i use a 32 tooth hacksaw blade with very fine cut and pressure
cut a slot on the backside of 1st cam bearing to oil hole

then on babbit side i have a small round file to deburr raised babbit edges and go a little further and chamfer a small valley
...all this is done in machinist vise without teeth

then i knock in 1st cam bearing into block...what you windup is a small pressurized channel feeding oil to cam/block thrust surfaces and spraying oil on the timing chain for extended chain/sprocket teeth life.

when the cam's in , there is a small pressurized tunnel effect formed

not for a beginner

 

Larry,

One way to do it, another way is after you drill the .030 air bleed in the center screw in plug above the camshaft, you drill a .050 in the thrust face surface at the 12 o'clock position. Easy in a old school SBC, harder when there is a cam retention plate in the way.

Never though of doing it your way but makes sense to me.

Thanks,

Bret

 

the reason i didn't mention the drill hole method was that its a tiny size drill bit , i've had 2 different racers over the years come to my shop to ask me if i knew a way to remove the broken drill bit out of the block in that location

another time while trying different cams in dyno session, we went to change cams and i noticed the racer had a broken off drill bit ground flush with thrust surface and 2 holes he did manage to complete.

but another reason is with the slot you get pressurized oil between cam journal and cam bearing surfaces in front half of cam bearing..when i take engines down and look at cam bearing modified this way, they always look almost brand new , even with tight chain

with very tight chain there is more load in this area on bottom surface of cam bearing in 1st location
if you drill holes to spray oil, the chain is taken care of, but the 1st cam bearing's bottom surface has a lot of load from tight chain that you didn't account for added oil protection in that location


the 1st cam bearing is hacksawed "half-way" along in "length" till cam bearing hole ...the other half of cam bearing is left alone

i've done this on hundreds+ of blocks , never once did that front cam bearing not look almost brand new after plenty of miles on it

i'll try to post pic of cam bearing later on

 

Thanks for the info.

Pictures would be great!

 

http://www.maxracesoftware.com/Cam_Slot.jpg

sorry that pic isn't clearer, the block is under a work table
where lighting isn't great, and block needs final cleaning.

 

when i use the pinion shims on the bottom crank sprocket
for alignment ..its because i'm also using a brass thrust shim (like Manley's) behind the cam sprocket also .

forgot to mention that .

 

Seems like that would make the bearing weaker or something related, guess not though.

 

Yeah plus...Have you ever seen how much oil comes out of there unaltered? Plenty IMO