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Timing chain

TulsaFred

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Putting the 1275 back together, the timing chain and gears had no visible wear.
After putting the assembly back on the crank and cam, I notice there is a fair amount of laxity in the chain, ie. I can deflect the chain about a half inch at its midpoint between the cogs. The teeth look fine and the chain fits snugly on the gears.

This engine has very little wear, it was sitting in a garage since the early 1980s.

I hate to simply replace original parts with aftermarket items of dubious quality. My thinking is that the original parts, if showing little wear, are better than brand new Taiwan or Chinese parts. Lord knows I've had fit and function issues with lots of aftermarket parts.

That said, is there a problem with the timing chain?
I notice there is no tensioner on the 1275.

Thanks,

Fred
 

Gerard

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Wear is difficult to detect on these components. Your chain might be stretched. APT and I think 7Ent have good quality chains. (German made, I think) I usually replace all 3 as they aren't all that expensive.
 
D

Deleted member 8987

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Sometimes you can hold the chain, and compress/decompress the links and see movement, which means the link pins are worn.
 

BlueMax

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You may encounter an issue with a slack timing chain that will be completely out of your control after you replace all of your new components. Unless you know the full history of your engine block it could have possibly been line hone or line bored once in its life. If this machining procedure was done to your block the crank sits deeper in the block causing the chain to have slack in it. It want be much, but if your block has been machine you may have a few degrees of slack, nothing to be overly concern about. If its has been machine a lot you will have to find a supplier that can provide custom made chains, but that would be very rare. However, it would be wise to replace both gears, paying close attention on the quality of the timing chain you use. If you can find one the best chain for the A type engines will be Rollmaster made in Germany, no cutting corners in this area.
 
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I've got a new IWIS German timing chain if you interested, after hearing the price you mazy not be that interested but it seems your does need repalcment. IWIS is who makes the chain for the Mercedes Benz and BMW over the years, and are considered the very best inthe world, oh and did I mention they are very proud of them. I don't know of anyone that ever stocked the separate IWIS timing chains other than me, some sold the Rollmaster units and that came with them, but not the separate chains, but the Rollmaster vernier unit are not longer made.

FWIW, the AE is decnet chain, and all of them , including the IWIS chain will stretch over time, and yes you should replace this in a rebuild.

Alan, a line hone job can reduce the distance between the cam and crank centerlines, but we're talking a couple thousands of a inch, line boring removes hardly anything, because it removes very little from the block side, where a honing remove a bit more from the block side, but still a minimum amount.

Bottom line , chains just stretch over time, and chain with a fair amount of stretch can directly relfects your cam timing.
 

BlueMax

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It’s my conclusion that line honing removes less material than line boring. Line boring leaves greater peaks and valleys were by line honing has smaller peaks and valley. In other words the smaller the Ra value the smaller the peaks which create more surface area were by the bearing has more area to sit on with less chance or metal fatigue from the peaks. From my own experience just a few thousands removed from the block will create as much as 1.5 degrees of chain slack, not much, but something that has to be accounted for. Just one of the down falls of the A type engine, no timing chain tensioner. The A+ and 1500 engines carried them to compensate for the chain stretch, very helpful in maintaining ignition timing.
 
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BlueMax said:
It’s my conclusion that line honing removes less material than line boring. Line boring leaves greater peaks and valleys were by line honing has smaller peaks and valley. In other words the smaller the Ra value the smaller the peaks which create more surface area were by the bearing has more area to sit on with less chance or metal fatigue from the peaks. From my own experience just a few thousands removed from the block will create as much as 1.5 degrees of chain slack, not much, but something that has to be accounted for. Just one of the down falls of the A type engine, no timing chain tensioner. The A+ and 1500 engines carried them to compensate for the chain stretch, very helpful in maintaining ignition timing.

Alan, sorry can't buy into that, line honing takes more off the block side due to the nature of a hone trying to cut equal amounts off the entire housing bore, where a line bore is set to only skim the block side and cut the housing bore back round and in spec by doing the majority of cutting to the cap side. Bottom line neither one take a noticable amount off to make the chain looser, we're talking a few thousands of inch with either procedure. Nice try though grasshopper :jester:

Plain and simple this guy just needs to buy a new chain.
 

BlueMax

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Hap,I think you miss the mark from my comments about line hoeing verses line boring. Line boring is primarily use when a lot of metal needs to be remove from the caps, hence more material is removed. With the line hone again your only removing tenth’s of a thousands and again your Ra is smaller were by the bearing has a smoother surface to seat on. But as we both know the more that is remove from the block the shorter the chain.
 
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OK, I've never looked closely at an old chain. Does the metal actually stretch or is it wear in the link pins that cause them to "stretch"?
 

DrEntropy

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Roller and pin wear. Hold one horizontally (pins/rollers to the vertical) and compare old with new. Old (worn) chain will exhibit considerable "droop" or curvature compared to a new in spec one.

Hap said:
Plain and simple this guy just needs to buy a new chain.

Yup.
 
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BlueMax said:
Hap,I think you miss the mark from my comments about line hoeing verses line boring. Line boring is primarily use when a lot of metal needs to be remove from the caps, hence more material is removed. With the line hone again your only removing tenth’s of a thousands and again your Ra is smaller were by the bearing has a smoother surface to seat on. But as we both know the more that is remove from the block the shorter the chain.

Alan, you remember me sizing your connecting rod big ends, remember the Sunnen cap grinder, we put each rod top and cap on the cap grinder and removed about .002" off them, then bolted them back together and honed them, the same sort of procedure is done with a line hone or line bore in fact the same exact type of cap grinder is used, now on a mains, you can't grind the parting lines on the block side, just the cap side for obvious reasons, so that's all the is removed from the cap is a couple of thousands of inch, what this does is make the housing bore smaller than spec and then the hone the circle back out to round and to spec size again, because the nature of the hone it is trying to take as much material from the block side as the cap side, now it doesn't because there's not as much to be remvoed, but nevertheless the hone is trying to remove equals parts, now a line boring machine has a cutter on it that turn and goes thru the main housing and it is set up by zeroing it out on the block side, and then when the cutting begins all it does is trace cut the block side and take the majority off the cap side, I know, I used both machines. Bottom line, it really does not matter, and has absolutely nothing to with this guy's chain issue. Alan, as normal, you way over complicate matters. :jester:
 
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TulsaFred

TulsaFred

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Had a few parts I needed from Vicky Brit, so I ordered a timing chain as well for all of $8.95.

Hap, how much for your IWIS chain? (send me an email at fwillison@mac.com)

Anyone have experience with the chains from VB or Moss?

The car is not a racer, it's being restored for nostalgic purposes and will cruise the boulevards and local drive-in shows when done.

Thanks all,

Fred
 
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TulsaFred

TulsaFred

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Oh,
and anyone know a spec on the chain laxity/tension? Maybe it is supposed to have a little slack?
I see on some of the other A series there is some type of chain tensioner, but not on the 1275.

Fred
 
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TulsaFred

TulsaFred

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Here are some pics:

2hnp5js.jpg

riukax.jpg

29p908h.jpg

xee4he.jpg


Notice on photo C and D the marks I placed on the engine plate to indicate amount of deflection with chain taught and loose via turning crank.
The deflection, measured this way is about 3/16 to 1/4 inch.
I've seen some say up to 1/2 in is ok on some engines.

Fred
 

BlueMax

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Fred, my engine had almost the same amount of chain deflection. As I said the 1275 engines really needs a good chain since they do not have a tensioner to take out the slack. You just can't cut corners on the quality. As the chain stretches your timing will not stay accurate and you will have to advance the distributor to compensate.. That’s why even racers keep a close eye for chain stretch. If it makes you feel any better I’ve provided a photo of my chain, you can see some droop with mine too.
 
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Fred the IWIS timing chains are goofy, stupid expensive, $45.00, that is IWIS chain you see on Alan's engine, he got it from me. Iwis' rivets seem to be a tad larger than the other chains, so it's good idea to do test fit with the balancer and oil slingers tight, if you see the rivets too close to the oil slinger reverse the oil slinger and that give you more clearence. I mostly use AE chains, they are under $20.00 , I tend not to buy from VB, they offer one line of parts, el~cheapo :smile:


Here's another IWIS Chain on a Rollmaster vernier timing gear.
 

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DrEntropy

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Hap said:
it is set up by zeroing it out on the block side, and then when the cutting begins all it does is trace cut the block side and take the majority off the cap side

Again, no more than a thou or two difference twixt crank and cam centers. Not a consideration. Mating surface of the cap-to-block is shorn to "sacrifice" the cap material and keep the centers (cam/crank) close enuff to spec.

As for the slack, the "pull" side determines the cam/crank relationship. If the chain is slightly worn, the timing relationship can be as slightly affected. Renewing the chain will bring that "slop tolerance" into a closer approximation of the original specs. A chain worn to the point of 1.5 degrees or more would likely make great ugly noise and either fail or soon jump teeth.

<span style="font-style: italic"> EDIT: That vernier cam gear is teats, Hap!</span> :wink:
 
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TulsaFred

TulsaFred

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Hap,

What is a good source for better quality parts, like the AE chain you mention?
thanks,

Fred
 
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TulsaFred said:
Hap,

What is a good source for better quality parts, like the AE chain you mention?
thanks,

Fred

British Parts NW is where I get mine. The thing I like about BPNW is Greg and Leyton offer the entry level part, knowing good and well that is all some folks will buy, but also offer uprated parts as well, which in most cases is all I buy.
 

69sprite

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Hap,

You don't know how relieved you have just made me!

I completed my rebuilding after a long delay due to work, family, and procrastination I completed my rebuild about a year ago....

AND I had used lot of parts (including the timing chain) from BPNW... I agree that they are pretty decent guys and they seem to carry at least two levels of parts and are reasonably priced in each level.

I was worried about using the timing chain from them, as I hadn't heard many on this forum talk about BPNW...but it seems to be doing well. The only parts where I might have a concern is the water pump I got from them. It makes a little noise. It could be just that '1 in a million' bad one in the batch. The other concern is the quality of the gasket set. The one for the timing chain cover didn't hold up well and I have a small puddle showing up from it. (but then again, it probably is user error and not manufacturing quality!)...

Larry
 
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