Timing Gear/chain Set Confusion

Well, looks like my 304 will be needing a new timing chain. Checked the back lash at the distributor. I am right at the limit. The set in there has about 90k on it. Don't recall any details of what type I installed as it was around 40 years ago. CRS. Shopping for a new set is daunting. Summit Racing, Rock Auto, ect all offer multiple brands/designs and so on. Some have link chains, some roller chains, some double roller racing chain ect. What have you had good luck with, what is best brand ect. Thanks, Jim

 

Cloyes double roller is among the best timing chains. I prefer roller chains, but any quality brand link or roller chain will be fine.
Its a bonus if the crank sprocket has 3 keyway choices to fine-tune the cam timing, provided you have the instruments to measure this.
-Donny

 

Thanks for your reply. I did notice that some of them did have extra key ways. However I am not educated on timing/cam adjustments enough to know how to measure or make any performance improvements. The only improvements I would be interested in would be maybe fuel mileage increase and or low end torque improvements. I would want to maintain smooth idle. and no decrease in fuel mileage if possible. Can a person simply use one of the alternate keyways to accomplish some type of improvement or is a lot of other changes that must accompany the new keyway selected? I have an idea that I am asking too broad of a question.

 

Not to dis the expertise of the people here, but there is lots of discussion of this question on both the AMC and Wagoneer forums. The Wagoneers are almost all running the 360, and anything that applies there will apply to your 304.

I would start here, and follow the key words that this thread bring up. SC397 is an AMC engine builder that has a presence here and on the AMC forums. http://www.ifsja.org/forums/vb/showthread.php?p=1678711 It seems there's not a lot of choice anymore - most are reboxed from one supplier.

 

In general, advancing the cam relative the crank produces more low end torque at the expense of top end power. Retarding the cam produces more top end power at the expense of low end torque. The effects are not huge but can be large enough to be noticeable.



Advancing the cam could improve your gas mileage a bit. If it makes more torque in your crusting range, you can use less throttle to maintain the same speed.

You can get into issues advancing/retarding the cam too much in performance engines with high compression and large lift, long duration cam shafts. If you advance/retard too much the valves can hit the pistons. In your case with a stock motor and stockish cam, there's no reason not to advance it the 2 degrees. It probably won't make much real life difference but at least it's directionally correct to increase low end torque in a Jeep.

 

If you invest in one of the better dyno simulation programs, you can get a really good evaluation of what advancing/retarding the cam various amounts will do to power/torque across the entire rpm band. I've been using Comp Cams Dyno Sim for years. I ran the 381 cam 3 degrees advanced but the custom cam I had ground for the 441 is installed straight up. I'm not sure what is available for AMC's but for Chevy's, there are several timing sets that are infinitely adjustable. As noted, the difference isn't too great but it can be a useful tool getting an engine to run at low rpm without it eating its self.

 

I just noticed I have an alert saying this thread was moved to a different forum. But I cannot find it.
Can anyone help? Sorry if I posted in the wrong place. Jim

 

Intermediate forum.

http://www.earlycj5.com/xf_cj5/index.php?threads/150943/

 

Now I’m curious, I used the comp cams chain last year on my 304. I seem to recall the one main thing is to ensure the gear has the proper oil hole to allow lune to the distributor drive gear? I may be wrong, that was a bunch of beers ago I was messing with that. The comp cam chain seemed to work well though.

 

The link that timgr posted above. there is lots of info on that subject there. Here is the link.

 

Ok, now I have an embarrassing question to ask you cam expert guys. I know the answer is probably right there but dummy me I just cannot reason it.
I have been studying the new timing sets that are available. Some of them have 3 keyway slots in the crank gear to chose from for advancing or retarding the valve timing. It appears all of the sets available are alike with the 3 key ways equally spaced around at 120 degrees apart. One will be set straight up for standard/factory timing position, the other two are 120 degrees either direction for advance or retarding the timing 4 degrees or so it says in the description. I know that the crank gear to cam gear ratio is 2:1, so it would seem to me that moving the crank gear to the next position (120 degrees) would advance the timing on the cam gear 60 degrees, a lot more than the needed 2 or 4 degrees that is needed. So go ahead and laugh at me then point out what I am missing.

 

Sorry I can't help you on the degrees subject. Just wondered if you ever decided on which brand to go with? I am in the same situation trying to find the best replacement set. My resources to re-work oil grooves and what not are limited, was hoping to find a good bolt-on and go set.

 

This page (for sprockets with even more keyways) explains it pretty well: https://www.cloyes.com/9-keyway-crank-sprockets/

Basically there are multiple index marks and you need to use the one associated with the keyway you are using.

 

I finally got time to look at the new timing set I have from Summit Racing. I still have not installed it yet. Here are some photos of my new set. After studying up a bit, reading timgr's link on his post above and asking opinions on here I made the decision to purchase this Edelbrock set. This set #7818 appeared to be a double roller chain that seems to be recommended over the regular chains and it had the means to adjust the cam timing a little with extra keyways in the crank gear. I think the main thing is making sure the oil grove in the back of the new cam gear lines up perfectly with the oil supply hole in the end of the cam shaft so that distributor gear will get enough oil. Some of after market sets are machined wrong and cause oil starving of the dist gear. (again read and study timgrs link abovehttp://www.ifsja.org/forums/vb/showthread.php?p=1678711 ) .I will be able to tell you more when I get time to install my new set.

 

Thank You, I am now learning a lot about Cam timing and how I affects engine operation and the benefits of the adjustments.

 

What's the purpose of the roller chain? I would assume it takes less power to drive the roller chain, so it's a hot rod / go-fast thing. I think the main area of wear for the steel chains is the link pivots. This lengthens the chain (eventually) causing a sloppy connection between the crank and the cam/distributor. Except for the nylon gears, they have to wear a lot to be sloppy enough to jump time.

Will the roller chain last longer than the conventional fixed link chain, in terms of lengthening? I would think not.

 

Not sure either, seems most people prefer them for some reason, I am not exactly sure how they work but the drive chain on some motorcycles are "o-ring roller chains" They did last a bit longer than conventional chains my experience. .

 

They resist stretching a lot better than a conventional fixed link chain, which is one of the points of running one. While it is a hot rod thing, stock applications can benefit from it. Higher lift cams, stronger valve springs, higher cylinder pressures contribute to premature wear or failure in a stock style chain, hence the double row roller chain. The next step up from this would be a gear drive timing set which is completely unnecessary except for real high performance applications. Kind of a pain to set up to as you have to have something to control the thrust on the gears (timing cover clearance and thrust).

 

Kind of following up on an older thread. I did some poking around and reading about this timing chain issue, specifically the lack of availability of the exact OEM style (not the plastic ones) timing chain and gears. From what I have read, the "correct" one from Cloyes was part number 3118. That apparently is no longer made. You might find NOS somewhere, but they are getting scarce. The substitute for that from Cloyes is part number C-3008K. That part number is actually a rebranded one from SA Gears part number 78118R. I guess other ones on the market are largely rebranded from the SA Gears folks, guessing they actually manufacture it? With all of the newer ones, the important issue is to make sure the oil passage from the cam (source) aligns with oil cavity on the side of the gear that goes towards the inside (block). I am still reading on the importance of filling in some of the extra grooves on the front side of the gear. Most of the newer ones apparently have six which some say is too many and will reduce the oil pressure that is actually getting to the distributor gears. Some folks over on an AMC forum have said they have just replaced the chain in recent years due to the lack of proper gears.
Anyway, I just wanted to sort of condense the information I have seen and if anyone has information to share (or correct), I would appreciate it. Thanks.
My info: 1973 CJ5, engine 360 transplant from 72 Wagoneer.

 

Using the timing set to advance the cam means you installed the wrong cam. Or are looking for a little gain from factory cam since you dont want to change it.

Or, as was the case with my cam, the cam grind did not match the card. So the extra key slots enabled me to get the cam times closer to what the card showed (and what I wanted).

I installed a Rollmaster. Made in Australia. Pretty sure it's endorsed by Mad Max.

Here's a tip on timing chains. They are shipped with a rust preventive coating, which is NOT a lubricant. Completely degrease the chain with acetone or similar. Thoroughly dry. Mix up some break-in oil (extra zinc) in an empty can like used for canned chicken breast. Roll your chain up in that can and let it sit for a few days to percolate out all the air bubbles. I even put it on coffee pot heater to drive out more air. This way your chain is COMPLETELY oiled for startup. Maybe it matters, maybe not. But seems like a good idea and doesnt cost anything.