TheSamba.com :: View topic

Wed Mar 13, 2013 10:38 pm

I might be having coil bind with my motor, but all the posts I've read here about coil bind have me confused. I am a "shade tree engineer" and I don't have cool measuring equipment to check the valve springs for coil bind. I've also read that there should be .060" between the coils. Between which coils? The ones right in the middle, or all the way around? Between just the outer coils, or the inner ones, too? If the inner ones too, how do you get in there to measure with the head completely assembled? What do you use to measure this? Looks like I'd need a 90 deg. angled feeler gauge. As you know the clearance between the coils is tighter closer to the retainer and head. Also, this engine is already completely assembled; too late for a mock up. I'd like to determine if coil bind is happening with the engine assembled before taking it down. Some direction for a club carrying, knuckle dragger would be appreciated!
8)

Wed Mar 13, 2013 10:46 pm

Um, I think you'll find suggestions of a total of 60 or 70 thou before coil bind - so divide this by the number of gaps between coils for the thickness of your feeler gauge. Or see if you can pass a ten thou feeler through, though as you pointed out, some springs are not wound evenly as they are after a progressive rather than linear action. Most real mechanics eyeball it, though - if you can see gaps between all of the coils it probably isn't going to bind.

Yes, it is difficult to check the inner springs if the outer are in place, so you either have to trust they will be OK with the outers checked, or pop off the outers and check the inners on their own.

What kind of lift are you running that you think you have coil bind? (what heads/springs/retainers might help here, too.)

Wed Mar 13, 2013 11:00 pm

Quokka42 wrote: Um, I think you'll find suggestions of a total of 60 or 70 thou before coil bind - so divide this by the number of gaps between coils for the thickness of your feeler gauge. Or see if you can pass a ten thou feeler through, though as you pointed out, some springs are not wound evenly as they are after a progressive rather than linear action. Most real mechanics eyeball it, though - if you can see gaps between all of the coils it probably isn't going to bind.

Yes, it is difficult to check the inner springs if the outer are in place, so you either have to trust they will be OK with the outers checked, or pop off the outers and check the inners on their own.

What kind of lift are you running that you think you have coil bind? (what heads/springs/retainers might help here, too.)

Haven't measured actual lift. Theoretical lift is .530" (SLR XR 302 cam w/ CB 1.4:1 rockers). Heads are old casting CB 044's, dual springs (don't know brand), and retainers... ? No clue.
I've run into this before many years ago and I didn't address it properly and wasted 3 cams, a handful of valve springs, and a bunch of other stuff. I'm more cautious now, and when I turn the motor over by hand it feels tight when valves are coming to full lift. I've already run this motor for about 30 minutes for cam break in, and it sounded healthy while it was running. Then I had to remove it to fix an oil leak. While it was out I visually inspected the cam through the cylinder holes and it looked good, at least on the lobes I could see. But, when I put the rocker arms back on and turned it over, it felt pretty tight as described above. I also noticed on the #1 intake valve at full lift, it looks pretty squished, but I don't have anything to compare it with. I turned the motor over some more and the other valves didn't "look" as squished, but it is hard to tell. Here's the best pic I could get of it. You can see the inner spring there in the middle.

Wed Mar 13, 2013 11:06 pm

Have a go at Quokka's method, if you can easily get a feeler guage in there then the spring should be ok, the other thing to look for is interference between the valve guide and spring retainer, its often over looked but could cause a tight spot till it clearances itself or chews up cam, lifters etc

Just saw the pic, looks to be ok with a gap between the coils

Thu Mar 14, 2013 12:16 am

Looks good to me, too. I believe those heads with the supplied retainers and springs were supposed to be good for .600"

Good point by 88brm, though. Again you should be fine, the retainer (actually keeper to guide clearance can be improved by machining i\the guide down or different retainers, but I don't expect a problem with those heads and that lift.

There are guys out there with more experience than I with these, and it never hurts to check.

Thu Mar 14, 2013 10:54 am

Use a feeler gauge to check coilbind. Not only that, you also have to check the retainer it does not hit the top of guide at full lift.

This is why it so important to do a mock-up assembly to find these clearance issues.

You can run as tight as 0.020" before coilbind. I do not think you have that problem w/ the outer springs. But you definitely need to check the inner springs as they look pretty tight in there. Good time to also check the retainer-to-top of guide clearance.

Thu Mar 14, 2013 11:52 am

nsracing wrote: Use a feeler gauge to check coilbind. Not only that, you also have to check the retainer it does not hit the top of guide at full lift.

This is why it so important to do a mock-up assembly to find these clearance issues.

You can run as tight as 0.020" before coilbind. I do not think you have that problem w/ the outer springs. But you definitely need to check the inner springs as they look pretty tight in there. Good time to also check the retainer-to-top of guide clearance.

But, how do you physically check these things? I see no way to get in there to check. Can't get in there to check the inner springs or retainer/guide clearance.

Thu Mar 14, 2013 12:16 pm

You have to check each part. First the inner springs by themselves, put on full lift when you turn the motor by hand. Then check the outer springs by themselves.

But you should have checked the retainer interference first to make sure you have enough clearance. you just use very light springs to check this one like the springs on Type IV rockers. Just visualize if at full lift, the retainer is clear or not touching the top of bronze guides. Do this to each one.

Don't assume anything. Check it and know it if anything is going to hit.

Thu Mar 14, 2013 12:49 pm

Actually, you can remove the springs and do a mockup of the valve, retainer and keepers. Then just measure the distance between the keeper and the guide as you pull on the retainer.

Thu Mar 14, 2013 12:54 pm

cb has atleast 2 diferent spring combos (duell)1 takes about .550 lift& the other is around .625 form what I remember, you need to check it , dont gess, just do it.

Thu Mar 14, 2013 2:37 pm

Would love to, if I had the tools to do so. I wonder if anybody local has a spring compressor for sale...

Also, given who last had their hands on these heads, I'd guess that the springs and retainers are from Berg.

Fri Mar 15, 2013 8:14 pm

Tools needed: Drill press (cheap at HF), drill bit or steel rod, dial indicator set with extensions/mounts, steel plate.

I have used a drill press to measure mine. You can use a drill bit with the spiral part in the drill head so the flat part of the drill bit shank sits against the valve stem or use a piece of steel rod. The head will need to be off the drill press plate enough to allow the valve to open if using real high lift and you will have to use somethong to get it level, like a piece of flat steel to put under one side so the head "tilts". You will measure using a dial indicator mounted so it can seat against the head or something on the drill press fixture. Lower the drill shank to the valve then zero it out, push down to your advertised cam lift with ratio rocker. Once you hit that number then gently keep pushing the valve down until the spring "binds". The diifference is your coil bind. Do this for each valve.

Mike

Fri Mar 15, 2013 9:41 pm

If the valve in the picture is at full lift, I would say you don't have any coil bind, It appears you can you have more than .060" clearance between the coils.

As for checking the clearance between the retainer and guide, you will need an overhead spring compressor-
http://vwparts.aircooled.net/Heavy-Duty-Valve-Spri...l-rent.htm

To check retainer to guide clearance- remove the spring with the tool, re-stall the keeper, retainer, and rockers. Run up to full lift, and check clearance. Re-install spring when done.

Sat Mar 16, 2013 4:53 am

Would it be possible to "feel" bind at the adjuster? Like turn it in a full turn and "feel" how it rotates?

Sat Mar 16, 2013 10:57 am

I appreciate everyone's thoughts. Thank you.

The drill press idea is really the "correct" way to do it, however I really don't want to remove the heads again. I talked to Rocky Jennings yesterday (the guy who makes the tool that Aircooled.net sells) and the drill press way is how he does it. I asked him if his valve spring compressor tool could be used to measure for coil bind and he didn't recommend that. He did say after I described how I'd do it that I was "in the ballpark." I notice that all of the springs have different coil measurements at full lift, and I believe this is because they are all shimmed differently. I believe this was done to get all the spring pressures the same when the valves are seated. That one in the picture is the tightest of the 8. Correct me if I'm wrong, but I would say that addressing coil bind is more important than getting all the spring pressures right.

As far as the valve adjuster way of doing it, this is NOT accurate enough. I tried this method on an engine a few years ago and the measurement I got was not the measurement that was actually happening. I wasted a couple cams, bent pushrods, broke springs, etc., until I finally figured out what was really going on. DOH! Plus you are really stressing the threads on your adjuster and in the rocker arm. These parts were not meant to compress the valve spring on their own.

Sat Mar 16, 2013 11:29 am

Since I dont have a spring pressure gauge I always like to make sure I had the same coil bind on each spring. I would imagine if someone has a spring pressure gauge they would want the set to all be the same and not adjust with shims.
Without measuring them you wont know what their true intenion was, but if that one in your photo is the tightest and it measures good with the feeler gauge then you should be fine with the others.
If you really want to get into measuring then the next time you have the heads off and disassembled you can measure from the valve cover surface to the spring seats and see if there is any difference there. But coil bind is coil bind, you would like to have the same for each spring.

Mike