Timing chain conversion 1*row -> 2*row
Moderators: GRNSHRK, ron, bfons
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hansniskatuki
Timing chain conversion 1*row -> 2*row
Hello all wise men/women. I have read most topics about the timing chain issues but I am wondering is the conversion direct bolt on task? Single row parts out and double row parts in? Or do I need to do modifications somewhere? thanks
It's not a bolt-on for sure.
I have the link somewhere on what to do and how, but at work right now.
I'm sure others will chip in with more info as well!
I have the link somewhere on what to do and how, but at work right now.
I'm sure others will chip in with more info as well!
The M88/3 was all about power, no cats. At idle the raw fuel from the exhaust will make your eyes water like an old V-8 powered muscle car's exhaust did.
I used to think this would be an 'all gain, no loss' conversion. I guess if your only priority is strength, it still might be.
But.....
I had the good fortune to discuss high speed chain drives with a really s**t hot motor engineer/designer (who works in F1 and no I'm not saying who or what team).
He pointed out to me that every time a chain changes direction there are not only friction losses but inertial losses too.
Now call me an idiot if you like but I had never considered the latter before. It turns out that such losses are far from insignificant at high speeds especially and doubling the mass of a camchain will immediately cost you some real world power.
This may be of no importance in a 6er motor and I haven't done the maths to figure out exactly how much on one of these motors, but it may be worth bearing in mind.
My understanding is that the single row chain is plenty unless a guide fails in which case it is 'goodnight vienna' twin or single row alike.....
-just my two pence worth...
cheers
But.....
I had the good fortune to discuss high speed chain drives with a really s**t hot motor engineer/designer (who works in F1 and no I'm not saying who or what team).
He pointed out to me that every time a chain changes direction there are not only friction losses but inertial losses too.
Now call me an idiot if you like but I had never considered the latter before. It turns out that such losses are far from insignificant at high speeds especially and doubling the mass of a camchain will immediately cost you some real world power.
This may be of no importance in a 6er motor and I haven't done the maths to figure out exactly how much on one of these motors, but it may be worth bearing in mind.
My understanding is that the single row chain is plenty unless a guide fails in which case it is 'goodnight vienna' twin or single row alike.....
-just my two pence worth...
cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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hansniskatuki
The power issue had not crossed my mind but I think I am willing to make a sacrifice towards endurance. My average mileage per year is around 5000-7000km and I think that the time will have the same affect to guide rails single or double. So the next guide rail maintenance would be around 2037 regarding number of rows.. All the same I am still interested to know about the modification needed, and opinions..
i have been thinking about single VS dual for my m88/3 as it has right at 100k miles, i am inclined to go single but last time i looked some of the parts were NLA
3/81 633 m30b35 & getrag 260/6, motronic 1.3 -sold
86 635 with nearly all goodies from rotted away 85 m635 including the m88/3, tuning in progress on motronic 3.3.1
86 635 with nearly all goodies from rotted away 85 m635 including the m88/3, tuning in progress on motronic 3.3.1
I considered the dual row timing change when refreshing my M635 (133K miles) but was told about the additional machining needed as well. Since mine was doing fine with the single chain after 100K+ miles ..... I went with the "stock" single chain/new guide setup. My mechanic was able to get the necessary parts. PM me and I'll put you in contact with him.Pod wrote:I seem to remember reading that to fit the double chain in a Euro engine, you need to have one of the strengthening webs of the block machined for clearance - which weakens it.
Ed
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1985 M635 #1998 (gone but not forgotten)
1994 850CSi (also gone but not forgotten)
1985 M635 #589
1985 M635 #1998 (gone but not forgotten)
1994 850CSi (also gone but not forgotten)
1985 M635 #589
+1 on Brucey's comment.
You can read my engine conversion project write-up in the project section but that did indeed cross my mind when I had my M88 (single row) overhauled.
I'm quite sure that it does not require significant machining but firstly, the parts cost for a double chain was over 1000 Euro. On top of that, getting the sprocket removed and having a new one fitted would cost more money.
That is why I ultimately did not convert to double row.
If you are conerned about durability, I know one individual who scrapped his M88 motor due to a broken valve spring. I have not heard of any engine failure caused by the timing chain.
You can read my engine conversion project write-up in the project section but that did indeed cross my mind when I had my M88 (single row) overhauled.
I'm quite sure that it does not require significant machining but firstly, the parts cost for a double chain was over 1000 Euro. On top of that, getting the sprocket removed and having a new one fitted would cost more money.
That is why I ultimately did not convert to double row.
If you are conerned about durability, I know one individual who scrapped his M88 motor due to a broken valve spring. I have not heard of any engine failure caused by the timing chain.
sskang
1987 M6 Alpinweiss
Tokyo, Japan
"Aller guten Dinge sind Sechs"
1987 M6 Alpinweiss
Tokyo, Japan
"Aller guten Dinge sind Sechs"
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hansniskatuki
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spankey
If you havent done the work yet, I rebuilt an M88/3 engine on my M635, and elected to go with the single row chain. My chain had actually gone 184k miles with no refresh before I got ahold of it, and did the work.
My primary concern was the inertial losses mentioned above, along with the secondary concern of the modifications needed to make the swap.
Also, there is a long history of these things going quite a ways on the single row chain, and I have never (and I looked hard) found a report of an engine loss that was due entirely to timing chain failure. The old M90 euro engine also had a very similar single row chain, which worked well for a long time. Helped a friend rebuild one with 195k on the original chain...it probably would have continued to run for quite a while. The chain showed little to no wear.
Parts are gettable. I had no trouble...they are just bloody expensive.
My primary concern was the inertial losses mentioned above, along with the secondary concern of the modifications needed to make the swap.
Also, there is a long history of these things going quite a ways on the single row chain, and I have never (and I looked hard) found a report of an engine loss that was due entirely to timing chain failure. The old M90 euro engine also had a very similar single row chain, which worked well for a long time. Helped a friend rebuild one with 195k on the original chain...it probably would have continued to run for quite a while. The chain showed little to no wear.
Parts are gettable. I had no trouble...they are just bloody expensive.
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E9erCS
The perils of not going to 2 timing chains
I recently purchased a 1984 Euro M635CSi, with 96,200 miles on it. There was considerable uncertainty as to whether or not the valve spring upgrade had ever been done on its M88 engine-- the PA "thought" it had bee done, but service records were incomplete.
I had Mario Langsten of Vintage Sports & Racing, a highly respected BMW engine rebuilder in Bow, NH, open it up. Sure enough, the springs upgrade had not been done. Here is what he found, along with his commentary:
"Attached is what we found this AM when we removed the front timing chain cover, feel free to post this to the forums, but this is another example of why turning an new single row chain onto a worn single row sprocket is a recipe for disaster.
I have never seen this pattern of wear on a double row chain sprocket in any of the ///M engines I have had apart.
Picture shows wear in large oval, teeth with small circles showing almost none, this is caused by the loading and unloading of the
cam chain by the valve springs acting on the cams."
I had Mario Langsten of Vintage Sports & Racing, a highly respected BMW engine rebuilder in Bow, NH, open it up. Sure enough, the springs upgrade had not been done. Here is what he found, along with his commentary:
"Attached is what we found this AM when we removed the front timing chain cover, feel free to post this to the forums, but this is another example of why turning an new single row chain onto a worn single row sprocket is a recipe for disaster.
I have never seen this pattern of wear on a double row chain sprocket in any of the ///M engines I have had apart.
Picture shows wear in large oval, teeth with small circles showing almost none, this is caused by the loading and unloading of the
cam chain by the valve springs acting on the cams."
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- P1030022A.JPG (244 KiB) Viewed 13657 times
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E9erCS
My head is a stock M635 head, with the original valve springs!Voltmeter wrote:YIKES. Is this type of wear limited to the dual-cam head, or upgraded valve springs? I sure hope that's not wear typical for a stock head...
Nate
Additional comments from Mario before the timing chain was exposed when we were discussing the pros and cons of going to two chains (after I showed him this discussion string):
"BMW later chose to upgrade these to a very mild double spring set up; recall that worldwide parts kit campaign and recall.
This was done primarily to ensure that if a valve spring broke the valve doesn?t fall onto a piston.
These original double springs are NLA worldwide from BMW, I have had one car that broke a timing chain at 55K km! Belonged to a military officer who drove the car in suburban Washington, DC . . I suspect similar to your use in CT and NY . . he also never drove the car at high engine rpm. Two years ago I replaced the single row chain in a 77K km M635CSI with a single chain; the original chain was so stretched that the cams were retarded and the car ran like crap. Talk about a hand grenade in it?s last few seconds before exploding!..
Your car has the original single spring . . doesn?t take a lot of energy to drive the cam over these . .
To replace the valve springs now, one has to use the S38 3.5 and/or S14 2.3 stock springs, change the spring seat and the retainer and keepers. These are the only BMW springs that fit.
These springs are larger and stronger and require greater energy to compress and control.
There is no alteration to the engine block, as written the earlier posting is misleading . . to change the chain to a double row does require some machining of an aluminum ridge inside the front timing chain cover, but this is certainly not a strength-carrying part of the engine.
At 100k miles any of these chains are stretched, this will wear out the lower chain sprocket on the crankshaft . . installing a new chain on this worn sprocket will stress a new chain exactly where they fail . . . on the end loops of the links . . . "
I hope all of this is helpful to others in similar circumstances, trying to figure out what to do or not do, with their M88 engines.
--Steve
Confused
Not sure I got the point about the double sprung vales. Does the extra pressure needed to compress them create wear ?Also, was the point about updating the timing chain to update the single row sprocket at the same time?
2011 1 Series M
1974 2002 Turbo
1987 M6 (2/87) - Sold
1984 M635CSi (10/84) - Sold
2012 335 xi
2009 328 xi
1974 2002 Turbo
1987 M6 (2/87) - Sold
1984 M635CSi (10/84) - Sold
2012 335 xi
2009 328 xi
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Mario Langsten
My first post on this forum, hopefully many of you know me from other BMW forums over the years . . .
M6 Smitten wrote:
"Not sure I got the point about the double sprung valves. Does the extra pressure needed to compress them create wear ? Also, was the point about updating the timing chain to update the single row sprocket at the same time?"
The original light duty double valve springs that were the campaign kit for these car from many years back are NLA. So in the case of Steve's engine which still had the single springs, we needed to upgrade to double springs. The only set up that works for this is the double springs from the S14 2.3 or the S38 3.5. These are substantially stiffer, and will require more forces to be applied to compress and control upon valve closing. The original single chain is inadequete for this in a long term use application.
In the photo that Steve posted there is wear visable as indicated, but also close inspection of the picture shows some other interesting wear.
The bottom of the timing chain tensioner rail on the left shows where the loose chain has wrapped around and worn away the bottom edge of the rail. Shown in the picture below in the red with arrows.
The dark blue shows where the chain was starting to rub against the chain guide. The chain will actually rub enough here to ultimately break that corner off and the broken piece rolls under the chain around the crankshaft sprocket . . we've all heard of this happening . . resulting in bent valves as the cams are no longer correctly timed.
The light blue on the crankshft snout shows what is the start of wear caused by the soft BMW OE crankshaft hub. Look closely and you can see a very small edge built up on the woodruff key from wear. On this engine we'll be replacing the hub with a FF hub . . we will have these instock shortly. This is all caused by 2nd and 3rd order harmonics from the crankshaft where the soft stock hub deforms at high rpm.
M6 Smitten wrote:
"Not sure I got the point about the double sprung valves. Does the extra pressure needed to compress them create wear ? Also, was the point about updating the timing chain to update the single row sprocket at the same time?"
The original light duty double valve springs that were the campaign kit for these car from many years back are NLA. So in the case of Steve's engine which still had the single springs, we needed to upgrade to double springs. The only set up that works for this is the double springs from the S14 2.3 or the S38 3.5. These are substantially stiffer, and will require more forces to be applied to compress and control upon valve closing. The original single chain is inadequete for this in a long term use application.
In the photo that Steve posted there is wear visable as indicated, but also close inspection of the picture shows some other interesting wear.
The bottom of the timing chain tensioner rail on the left shows where the loose chain has wrapped around and worn away the bottom edge of the rail. Shown in the picture below in the red with arrows.
The dark blue shows where the chain was starting to rub against the chain guide. The chain will actually rub enough here to ultimately break that corner off and the broken piece rolls under the chain around the crankshaft sprocket . . we've all heard of this happening . . resulting in bent valves as the cams are no longer correctly timed.
The light blue on the crankshft snout shows what is the start of wear caused by the soft BMW OE crankshaft hub. Look closely and you can see a very small edge built up on the woodruff key from wear. On this engine we'll be replacing the hub with a FF hub . . we will have these instock shortly. This is all caused by 2nd and 3rd order harmonics from the crankshaft where the soft stock hub deforms at high rpm.
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- P1030022B.JPG (244.88 KiB) Viewed 13585 times
does anyone have the spec for the original springs? closing pressure and pressure at XXmm lift? anyway of telling if the update has been done other then disassembley? would this be in the dealers records if i give them the VIN? i am going to do the chain and rails but if i don't have to pull the head apart to check for double springs i don't wanna, already doing expensive preventive repair with the chain and don't need to add to the price of this build
3/81 633 m30b35 & getrag 260/6, motronic 1.3 -sold
86 635 with nearly all goodies from rotted away 85 m635 including the m88/3, tuning in progress on motronic 3.3.1
86 635 with nearly all goodies from rotted away 85 m635 including the m88/3, tuning in progress on motronic 3.3.1
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Mario Langsten
to see if your engine has single or double valve springs you need to pull the cam cover / valve cover
then with a bright light look under the cam box between the cams at the valve springs. There will be a coil inside the outer if there are double springs.
I use a bore scope as it allows me get inside the space the where the springs are, You might be able to do this with a small mirror as visability is not line of sight.
then with a bright light look under the cam box between the cams at the valve springs. There will be a coil inside the outer if there are double springs.
I use a bore scope as it allows me get inside the space the where the springs are, You might be able to do this with a small mirror as visability is not line of sight.
if they can be seen with a scope cool, i had the valve cover off once for a look around and to glance at the valve adjustment but didn't think to look at the springs while it was off, i wasn't sure if it was possible to see em. probably going to start breaking the car down in a month or two and want to sure up the motor while its out before introducing it to its new non rusty home
Mario Langsten wrote:to see if your engine has single or double valve springs you need to pull the cam cover / valve cover
then with a bright light look under the cam box between the cams at the valve springs. There will be a coil inside the outer if there are double springs.
I use a bore scope as it allows me get inside the space the where the springs are, You might be able to do this with a small mirror as visability is not line of sight.
3/81 633 m30b35 & getrag 260/6, motronic 1.3 -sold
86 635 with nearly all goodies from rotted away 85 m635 including the m88/3, tuning in progress on motronic 3.3.1
86 635 with nearly all goodies from rotted away 85 m635 including the m88/3, tuning in progress on motronic 3.3.1
Hi Mario,Mario Langsten wrote:to see if your engine has single or double valve springs you need to pull the cam cover / valve cover
then with a bright light look under the cam box between the cams at the valve springs. There will be a coil inside the outer if there are double springs.
I use a bore scope as it allows me get inside the space the where the springs are, You might be able to do this with a small mirror as visability is not line of sight.
I asked my mechanic to pull the valve cover and check for double springs on my '85 M635. He pulled the valve cover but can't see the springs using your guide above. Could you give additional info ..... maybe a diagram that would help him with this check ?
Thanks,
Ed
Last edited by Ed Lyerly on Wed Jan 26, 2011 1:23 am, edited 1 time in total.
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1985 M635 #1998 (gone but not forgotten)
1994 850CSi (also gone but not forgotten)
1985 M635 #589
1985 M635 #1998 (gone but not forgotten)
1994 850CSi (also gone but not forgotten)
1985 M635 #589
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naren
Is there a timing belt as well as the timing chain? I just bought an L6.. and I didn't have it checked out b/c I was in a fix.. and just found this paper that was in the glove box showing he had put in a timing belt last April...
it reads $75 for timing belt, $150 for water pump, and $175 labor... unfortunately not done at a BMW specialty shop.
it reads $75 for timing belt, $150 for water pump, and $175 labor... unfortunately not done at a BMW specialty shop.
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naren
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ray_koke
My understanding is that the factory recall specified that when the upgrade was performed, two punch marks were to be made at the front left of the head, just below the valve cover. Whether this was frequently done is anybody's guess.
GL,
Ray (driving a ticking bomb)
GL,
Ray (driving a ticking bomb)
Ed Lyerly wrote:Hi Mario,Mario Langsten wrote:to see if your engine has single or double valve springs you need to pull the cam cover / valve cover
then with a bright light look under the cam box between the cams at the valve springs. There will be a coil inside the outer if there are double springs.
I use a bore scope as it allows me get inside the space the where the springs are, You might be able to do this with a small mirror as visability is not line of sight.
I asked my mechanic to pull the valve cover and check for double springs on my '85 M635. He pulled the valve cover but can't see the springs using your guide above. Could you give additional info ..... maybe a diagram that would help him with this check ?
Thanks,
Ed
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hansniskatuki