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#828940 11/05/20 4:55 pm
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DavidP Offline OP
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There have been some warnings about coil binding with certain aftermarket valve springs, so I thought I'd check.
The thickest feeler gauge I have is 0.032". At full lift that will fit between the coils, just barely.
My fitted outer spring length is 1.311", WSM spec is 1.37". However, I am using Black Diamond valves. To quote JH, "Note: The margin on Black Diamond valves are .020 in. thicker than factory valves. This can close up both the fitted valve spring length and the valve-to-piston clearance."
Should I be concerned? Maybe use a thicker head gasket?


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
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DavidP #828961 11/05/20 10:34 pm
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Originally Posted by DavidP
There have been some warnings about coil binding with certain aftermarket valve springs, so I thought I'd check.
The thickest feeler gauge I have is 0.032". At full lift that will fit between the coils, just barely.
My fitted outer spring length is 1.311", WSM spec is 1.37". However, I am using Black Diamond valves. To quote JH, "Note: The margin on Black Diamond valves are .020 in. thicker than factory valves. This can close up both the fitted valve spring length and the valve-to-piston clearance."
Should I be concerned? Maybe use a thicker head gasket?

Valve spring coil bind is always a concern with non stock parts. If the engine is assembled, a rough check is to lever the rocker with the valve full open to see if the valve will open more. Not that accurate unless you get in there with a dial indicator to measure but it will give you an idea.

If you just took the springs out of their wrappers, a drill press, and old valve and digital calipers can give you an accurate coil bind dimension. This photo gives the basic idea, just use a caliper instead of a ruler and omit the plastic scale.

[Linked Image from i.postimg.cc]

Lastly, head gasket thickness has no effect on valve spring fitted length so don't worry about that, at least for this problem, but it will have an effect on valve to piston clearance.

To check that, use a blob of clay in your valve reliefs, rotate the engine 2 full revolutions and disassemble to find out if you have a valve to piston clearance problem. .060" to .080" is usually considered safe.

DavidP #828963 11/05/20 10:52 pm
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I dont know what the coil binding clearance spec is on these old bikes but I do know that insufficient clearance can cause bent pushrods etc.

I had this very problem on my A65 when first assembled and run. Turned out that the generic springs had a wire gauge too thick which caused coil binding. SRM sorted me out with smaller wire gauge springs which fixed the issue.

I dont remember the SRM spring wire gauge but they were standard not race springs.

If you Google coil binding spring clearances it looks like 0.04 to 0.06 is the norm. So a bit more than you have at present.


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
DavidP #828970 11/06/20 12:26 am
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Thanks,
Of course none of this came to light until a couple of years after I assembled this head. I forget where I bought the springs.
Maybe if I check again with clearance set at nil?


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
DavidP #828986 11/06/20 4:55 am
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Originally Posted by DavidP
The thickest feeler gauge I have is 0.032". At full lift that will fit between the coils, just barely.
Dave,
I don't think you have a coil bind problem. You need to think about it this way. How many spaces do you count on that spring? For example, I just counted 5 spaces (the gaps between the coils) on an A10 valve spring sitting on my bench. If I multiply those 5 spaces by your .032" measurement I get .160". Obviously your springs may have different coil count and that will will change your number but 160 thou is a big safety margin. I usually shoot for .040" spring travel minimum. One caveat would be progressive springs where some coils are closer together than the others. You would probably just want to measure those type with a spring checker. (Or the drill press idea.)

Just to give you a idea of where I am coming from on all this, I've built my share of OHC Jag XK motors with high lift cams and big valves, and the usual drill for valve springs is to sit down with the valve spring checker set up with a dial indicator and grade the inner and outer springs for actual measured coil bind length. I've found variations of over .060" in some of the lower quality sets. Then, if the lengths are workable I selectively install them where the fit is best. This is necessary due to differences in valve seat depth, lower spring seat machining from the factory, variations in valve lengths, collets and top spring retainers and the unpleasant fact that the camshaft bearing bores usually aren't parallel to the rest of the head. A royal PITA. Push rod valve trains are a lot more forgiving.

DavidP #830122 11/17/20 5:06 pm
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I have the same problem. Test ride three ended with bent push rods and a broken rocker. CBS has a link that describes the problem. CBS Coil Binding Blog.

I purchased the springs they offer from Germany. My problem appears to be exactly as stated in their blog.
Here are two pics of the outers. I marked the spring Old and New, but the Old spring is actually new installed by the mechanic who serviced the head. The New spring is the one just obtained from CBS.
Note the Old is longer and has 6 coils, New has 5 and a and a more open design.

[Linked Image from i.postimg.cc]
[Linked Image from i.postimg.cc]

The length of the inner springs is even more pronounced.
[Linked Image from i.postimg.cc]

I assembled the head last evening. I hope to assemble the top end with new pushrods and rockers tonight and check the springs at max lift.

DavidP #830133 11/17/20 7:55 pm
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Why did you buy springs from Germany when you could have got them from CBS or Ed V who would have sold you quality items in the first place?


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

DavidP #830136 11/17/20 8:21 pm
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I did purchase from CBS. Read their tech blog. They found the problem about 4 years ago with "some" springs from UK and found a source in Germany. According to their site the springs are adequate for A65 stock and sport cam's.

DavidP #830140 11/17/20 8:31 pm
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The coil binding springs were installed by the mechanic who serviced the head. Kibblewhite valves were installed. I called CBS who informed me that Kibblewhite does not make springs for the A65. Their guess was the mechanic probably sourced from UK. I don't blame him because they were probably sold as A65 springs and all he had was the head. Those springs fit the CBS description, 6 coils that bind. The German springs are from CBS and I assume they are quality parts.

DavidP #830175 11/18/20 5:20 am
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Well, I said that I could barely shove a 0.032" feeler between the center coils. But, I could see no clearance without the feeler in place.
So, I bought new springs from MAP, only five coils and the wire is thinner gauge than the ones which came out.
I'll report back once the springs are installed and the head is back on.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"

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