Timing chain oiling on dart big M block
 

I'm assembling my 540 using my new dart big M block,there is no 1/2 dollar size hole behind the top timing chain gear like a typical big block has,I'm using a cloyes hex adjust timing chain and gears with a torrington thrust bearing behind top gear. I want to ensure enough oil gets to the chain and bearing,I have seen in the past where timing chain manufactures reccomend cutting a slot in the cam bearing with a hack saw blade to let oil come out to the bearing (I'm not keen on doing this on these fancy coated cam bearings). My other option is drilling a hole in the block or one or both of the oil gallery plugs to let oil squirt out,how big of hole should I drill? I know if its too small (like .035-.040 ) it could plug fairly easy but I don't want to make it too big and lose too much oil either. It doesn't look like enough oil would ever wash out of the main bearing and cam bearing to keep the chain and torrington bearing lubricated to me. Cloyes just says in there instructions to ensure enough oil gets to the chain with no specific reccomendations,what do the big name engine builders do? On a side note,for anyone considering using a cloyes hex adjust timing chain and gears the chain is a piece of crap with nasty seams where the outer rollers are crimped over the pins,I throw the chain in the trash and use a better chain with machined rollers with no seams,I used one of these "true roller" IWIS cloyes chains before that had these crimp seams and at 130 hours there was pits in the crimps and the chain wasn't looking too healthy,Smitty

your best bet is to call dart and see what they recomend for there block, I'm sure they will have some answers.
good luck:

Smitty,
I have never had a problem with a Cloyes chain. Personally, I would be more concerned that the other chain is not manufactured to the same exact specs as the Cloyes one and might not really fit the sprockets correctly. If you dont feel comfortable with the Cloyes set, find another brand, but I would use all matched parts from the same manufacturer.

Just my Opinion,

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Bill,as far as using replacement chains on cloyes sprockets,manley chains and roll master chains have the same .250 dia pins,width and pitch,I have been using them for years on cloyes sprockets.On circle track motors and when freshening big blocks often the timing gears haven't started to exhibit any wear yet but the chain has stretched so you can replace the chain at least once before replacing the whole set. It sux that cloyes has a nice hex adjust timing gear set but supplies a chain with seams or crimps on the rollers. If you look at one closely you will see what I mean,a good timing chain has "true roller" sprocket bushings that spin on the inner pins(cloyes and most quailty ones do,cheap ones do not) but some but not all of cloyes chains have seams in the rollers where they are "crimped" from a piece of flat stock,a really good timing chain uses solid outer bushings that are machined vs crimped,I have had a crimped cloyes chain start to eat the rollers away at the seam where they are crimped,they are not even completey round at that point and bite into the sprockets,especially when running high spring pressures.This doesn't seem to happen on the bigger dia gen 6 chains but on the gen 4 and small block chains with .250 dia rollers.
As far as drilling oiling holes in the block galley plugs to help extra oil get to the chain,have you done this and what dia did you use? A stock block has the 1/2 dollar size hole behind the upper sprocket and some oil from the lifters/vallet area lubes the timing chain,on the dart big m this is casted out so the only oil the chain will see is the leak-off from the cam bearing and main bearing which I feel is not enough,some tech I have read says to slice a hacksaw width slot in the cam bearing to allow extra oil to flow out of the cam bearing but these cam bearings have a special coating on them and I'm not going that route,Smitty

Smitty,

I have 150 + hours on my 540 which has a Dart Big M block. I didnt do any modifications to the oiling system for the chain. To tell you the truth, I didnt even think of it, nor did I notice a potential problem. This winter, I am going to freshen it up, now you have me thinking of this as well. I am do to talk to Bib Madera this week. He is setting me up with his cam, lifters and T&D rocker set-ups. I will ask his opinion on this and let you know. Maybe he has some experience with it.

Vinny

Just went thru a 540 Big M Dart that had burnt 2 pistons and the double roller chain and the cam gear was missing 16 teeth. I wonder what caused this - was it from not enough oil? Gen 5 & 6 502's have those galley plugs with oil holes in them. This motor had about 95 hours on it.

Take it to a machine shop, have them put it in the mill and tap the hole in the lifter valley. I had to do the same thing on a Dart Iron Eagle small block for my drag car. This will allow oil to reach the front of the motor with no issues. One other thing to check......make sure the timing cover isn't pressed against the front main cap. If there isn't enough space between the two, your timing set will run wet and rob power.

My .02

I'm leaning towards drilling a .050 thousandth hole in one of the oil gallery plugs which will allow some oil to spray onto the chain vs the chain getting its oiling just from the leakoff from front main bearing and cam bearing. I know a guy who builds alot of 598/632's using dart blocks and said I'm worrying about nothing BUT he's a drag motor guy and measures life expectency of motors in passes not hours,Smitty

Did your chain show signs of lack of lube like bluing or extremely worn pins/bushings? You might have had other problems like your cam started seizing then the chain snapped o rvalve train bound up or hit causing a extreme load,you should have been able to tell when your motor was dissected,Smitty

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