Valve spring bind tolerance values pls?

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70Hardtop

70Hardtop

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Hi, does anyone know for sure if this spring will work, please see pictures

Does anyone know what tolerance value constitutes coil bind on a valve spring? Shown in picture is the spring I have installed and the valve is shown fully open - at max lift at the lobe (using a solid lifter for accurate measurements). The coils are not touching in three places (middle and the coils above and below) and the max I can measure is about 30 thou (0.030") between middle coils. Coils are tight at the top and bottom. I read that there is no hard and fast rule with binding tolerance, it all varies between spring types and materials. From 0.020 to 120.

This is a hydraulic cam, these springs are not locked up solid but I think these springs might be a little close for comfort (lift is advertised at 0.525/0.525). What are other people's thoughts on using these springs for running in this new cam? Thanks

Spring at max lift.jpg


273 spring at max lift.jpg
 
Crane Cams |

.060 or more from Crane info.
I would get a better suited spring.
Trickflow, comp, crane, etc have spring charts for download.
Crane chart:
 

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Thanks for that info. These springs are not intended to be a permanent thing, just in for 30min to run in the cam, as they are old low pressure springs. Swapping them out for the recommended CC springs after the cam is run. And only taking the engine up to around 2500 anyway. So I thought they might be ok in that situation, since they don't seem to be binding now
 
Looks like they may be pretty tight on the side away from the camera. Good that you measured the lifter movement with a solid lifter while you were doing this check.

FWIW, .060" total margin to bind seems to be the standard now; years ago, .100" margin to bind was the most commonly given number.

FWIW #2 Rusty springs would seem to be more prone to break.

What total lift are you running, and what spring pressure do you expect at full lift? FWIW#3, my personal decision point is that if the operating open spring pressure is going to be under 300 lbs, I break in with the final springs. But my lifts are not much over .500" for what I do.
 
I applaud your looking for the fine details. Have you also checked all the guide boss top (and stem seal) to underside of retainer clearances, too? Yeah, the existing coil bind clearance looks marginal to me. How much preload on the hydraulic lifters? I would run minimum preload, like 1/4 to 1/2 turn on adjusting screw. It's your call, but I would be uncomfortable with that clearance, albeit only for cam run-in.
Have you checked for spring/retainer to rocker body clearance? Sometimes that can be an issue, too.
 
If you check the pressure as you compress the pressure steadily increases and at one point the pressure starts to rocket up very fast that is were I call it max lift and it is usually way before the coils come close to hitting
 
nm9stheham said:
Looks like they may be pretty tight on the side away from the camera. Good that you measured the lifter movement with a solid lifter while you were doing this check.

FWIW, .060" total margin to bind seems to be the standard now; years ago, .100" margin to bind was the most commonly given number.

FWIW #2 Rusty springs would seem to be more prone to break.

What total lift are you running, and what spring pressure do you expect at full lift? FWIW#3, my personal decision point is that if the operating open spring pressure is going to be under 300 lbs, I break in with the final springs. But my lifts are not much over .500" for what I do.
Click to expand...

Thanks, Yes that is well deduced - the spring is a little tighter on the other side of the camera. Not sure if you said about rusty springs because of the slight discolouration of that spring. It had been soaking in kerosene and after a wash off with water, it's still a bit dirty. These are only 50 year old OEM springs from a 273 - I was looking at using them just for the 15 minutes of break-in for this cam. That's all. I wanted nice light springs for that exercise, I won't be going over 2500 rpm. I stated the total lift in the initial post - 0.525 / 0.525. However after three times measuring with a dial gauge as shown, I can only seem to get a maximum of 0.505". That is only from one lobe though. I should measure at least 4-5 lobes. The cam is new. Maybe the dial gauge is incorrect (made in You-Know-Where).

60 thou seems like the number I am hearing most. 30 thou at only one place on the spring is probably pushing my luck!

Commonsense should tell me that this is a large cam, with springs that were only meant for a small factory cam (under 0.45 I would say)

Thanks

reading max lift.jpg


Position of dial gauge.jpg
 
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rustycowll69 said:
I applaud your looking for the fine details. Have you also checked all the guide boss top (and stem seal) to underside of retainer clearances, too? Yeah, the existing coil bind clearance looks marginal to me. How much preload on the hydraulic lifters? I would run minimum preload, like 1/4 to 1/2 turn on adjusting screw. It's your call, but I would be uncomfortable with that clearance, albeit only for cam run-in.
Have you checked for spring/retainer to rocker body clearance? Sometimes that can be an issue, too.
Click to expand...

thanks, but I am not sure what that first sentence means, although I know what underside of the retainer is. As stated in the initial post, I am using a solid lifter for this measurement exercise (only one , as I had to modify it to make it the same height as the hydraulic lifters I will be using for this cam, so the pushrod would work. Previously, the solid lifter was too short). I actually did not look directly at the retainer to rocker clearance. Good point. I will look at that also. Only looked at the top of the pushrod cup to the rocker. The rockers I am using are Isky adjustable ones and they look to be a direct copy of Ma Mopar's 273 ones which I have a set right next them!
 
Daves69 said:
I think I'd pass on that spring just by looking at the picture. I'd worry about over stressing it and the thing breaking.
Another mfg..............See what IQ52 says.
Click to expand...
. Yes I know it doesn't look overly pretty, but I was only wanting them for 15min to break in the new cam, without worrying about heavier springs loading up the lobes too much. I wasn't worried about breaking a spring (although that is never a good thing to happen), I was more worried about the spring getting too tight and damaging other components, including the cam. It's a good quality CC one so maybe I am worrying unnecessarily. I do have some TrickFlow springs but I think they are about 285lb open which is still too heavy for my liking. They have even manufactured special light valve springs just for the purpose of breaking in new cams, so obviously doing this has some merit..
 
brian6pac said:
If you check the pressure as you compress the pressure steadily increases and at one point the pressure starts to rocket up very fast that is were I call it max lift and it is usually way before the coils come close to hitting
Click to expand...
Yes that is interesting. But these springs are only old 273/318 OEM ones, they might be all way out by now. I've noticed the aftermarket springs meant for performance cams have a higher angle of the coils, compared to the more horizontal look of OEM springs. Less winds per height
 
There is no way to tell for certain without measuring all the components and spring pressures. Visually........it's real close to coil bind. I'd have a second cam, pushrod, lifter and spring set ready to go in case I wiped the first one out.
 
when you reach that plus 0.500in lift threshold, you have to begin to look at a lot of things, you might otherwise take for granted. The way you check for guide boss to retainer clearance is, you assemble each valve and retainer in its final location, withough a valve spring and then measure the distance between the top of the guide and the bottom of the retainer. Just like the coil bind measurement it should allow for the lift of the cam, plus a safety factor distance. Of course, the stem seal takes up space and must be allowed for. too.
This measurement could also be accomplished like you showed, but with a light checking spring installed. That way you could push the valve open easily with your thumb, and "feel" the retainer contact the guide and note the dial indicator sweep.
 
rustycowll69 said:
when you reach that plus 0.500in lift threshold, you have to begin to look at a lot of things, you might otherwise take for granted. The way you check for guide boss to retainer clearance is, you assemble each valve and retainer in its final location, without a valve spring and then measure the distance between the top of the guide and the bottom of the retainer. Just like the coil bind measurement it should allow for the lift of the cam, plus a safety factor distance. Of course, the stem seal takes up space and must be allowed for. too.
This measurement could also be accomplished like you showed, but with a light checking spring installed. That way you could push the valve open easily with your thumb, and "feel" the retainer contact the guide and note the dial indicator sweep.
Click to expand...

Ahh, now I understand. Thanks for that clear explanation. I have never heard of that measurement though. Although it makes sense that you you DO NOT want the retainer to hit the top of the valve guide boss. But I didn't think the cast heads would be so accurate that that measurement could be used as a spring bind measure. But cams over 0.5", which is way over factory spec, yes it makes a lot of sense to know about these other critical areas. I will have a look at mine now.
 
IQ52 said:
There is no way to tell for certain without measuring all the components and spring pressures. Visually........it's real close to coil bind. I'd have a second cam, pushrod, lifter and spring set ready to go in case I wiped the first one out.
Click to expand...

Nice in theory...if I was rich enough to have two of all those components (about A$1100 worth) I would probably be paying a machine shop to set it up for me.
 
it's much better, all around, to check these things on the bench, before you have a catastrophe in the car. I used to do head work, on the side, that's how I know about some of these things. And you're never too old to learn something new.
 
rustycowll69 said:
it's much better, all around, to check these things on the bench, before you have a catastrophe in the car. I used to do head work, on the side, that's how I know about some of these things. And you're never too old to learn something new.
Click to expand...
So True. It's good when forums have good info from people who actually worked in that field of practice. Thanks.
 
The comment on rust was that any rust will create surface pits and these become possible stress riser points, where cracks and breaks will more easily initiate. Add that to the fact that these springs are old and subject already to some possible internal material fatigue. And they are being pushed well past their intended design compression limit, which means that the stress in the material is far higher than intended. All of these would tend to increase the probability of a spring breakage, even at lower RPM's. I don't think any of us can quantify this from an internet pix, but just identify the increased risk. I personally would not use them at this level of stress and age and surface rust.

BTW, the loss of lift at the valve in your measurement is not at all surprising. You are pushing the 273 adjustable rockers past their normal design range, and that by itself will cause less lift at the valve than 1.5 times the lobe lift. I wonder if anything like shims under the shafts, or optimizing the pushrod length and ball adjustment position for best geometry, have been done to improve the overall geometry with this high level of lift to reduce the loss of lift. And lift measurement will be low if the indicator plunger is not perfectly parallel to the valve stem; sometimes that takes a few tries to achieve.

And you are correct on the higher performance springs: thicker wire diameter and fewer coils is normal.
 
IQ52 said:
There is no way to tell for certain without measuring all the components and spring pressures. Visually........it's real close to coil bind. I'd have a second cam, pushrod, lifter and spring set ready to go in case I wiped the first one out.
Click to expand...

70Hardtop said:
Nice in theory...if I was rich enough to have two of all those components (about A$1100 worth) I would probably be paying a machine shop to set it up for me.
Click to expand...

Nobody really expects you to have all those components for back up. But if you don't measure everything you risk having to come up with that $1,100.

You asked about the springs?.....Can't tell from a picture.

Measure the installed height and take the spring to someone who can measure the pressures and coil bind height. It's the only safe way if you don't have the tools.

Don't like that idea? Then sock away another $1,100.....just in case.
 
nm9stheham said:
The comment on rust was that any rust will create surface pits and these become possible stress riser points, where cracks and breaks will more easily initiate. Add that to the fact that these springs are old and subject already to some possible internal material fatigue. And they are being pushed well past their intended design compression limit, which means that the stress in the material is far higher than intended. All of these would tend to increase the probability of a spring breakage, even at lower RPM's. I don't think any of us can quantify this from an internet pix, but just identify the increased risk. I personally would not use them at this level of stress and age and surface rust.

BTW, the loss of lift at the valve in your measurement is not at all surprising. You are pushing the 273 adjustable rockers past their normal design range, and that by itself will cause less lift at the valve than 1.5 times the lobe lift. I wonder if anything like shims under the shafts, or optimizing the pushrod length and ball adjustment position for best geometry, have been done to improve the overall geometry with this high level of lift to reduce the loss of lift. And lift measurement will be low if the indicator plunger is not perfectly parallel to the valve stem; sometimes that takes a few tries to achieve.
Click to expand...

Yes you are correct, thanks for that good info. I will not use these springs now after considering these points. Esp not on this valuable engine. Although there is no rust on these (just residual dirt from the wash), but yes any slight abrasion from corrosion to the surface of the coil will create weak spots (same as in torsion bars).

I didn't fully appreciate about the compression limits of the springs and that's true, they would be forced to act within an area they are not designed for, in addition to their metal fatigue from 30 years of use. Playing with fire - even if they are only intended to be run for 15 minutes, you just don't know what is going on inside the metal.

These adjustable rockers are not 273 ones, they are Iskendarian, as I said previously; but they LOOK to be a direct copy of the 273 ones. But that doesn't mean they are identical in geometry, I'm sure they have been designed to handle this sort of lift. But good point, I also have some Crane adjustables, the good ones made in the USA, which look very similar, I will try them and see what I come up with. Re the dial gauge position - it took quite a while of fiddling to get it visually parallel to the valve. I have a friend with another gauge, it might pay to compare with his also, to eliminate an inaccurate gauge. After all, it WAS the cheapest one I could find on Ebay! Even though it is identical to all the other priced ones which are all probably made in the same factory in China.

Another unsatisfactory thing is that I don't have an adjustable pushrod. So yes, the geometry at the pushrod and ball adjuster may not be ideal to get the full claimed lift
 
Ok on the rockers. They do indeed look like stock 273 rockers. Ok on 'affordable' tools!

A coupla other notes just from viewing your pix:
1) In the last pix with the dial indicator, the 3rd adjuster back in the pix looks to be a lot further down than the ones in the foreground; I would be wondering why. (Perhaps the hydraulic lifter preload is not even all across? Or valve heights different?)
2) In the same pix, the first rocker (on what appears to be a fully closed valve), looks to be contacting the valve tip waaaay over on the rocker side of the valve tip. This may be a good clue that the rocker shafts need shimming up (and perhaps the pushrods a bit longer to keep the rockers balls up high). It looks like the rocker contact point is 'walking' a long distance across the valve stem tip from fully closed to fully open. But I'll admit it is hard to really tell from just a pix.
 
nm9stheham said:
Ok on the rockers. They do indeed look like stock 273 rockers. Ok on 'affordable' tools!

A coupla other notes just from viewing your pix:
1) In the last pix with the dial indicator, the 3rd adjuster back in the pix looks to be a lot further down than the ones in the foreground; I would be wondering why. (Perhaps the hydraulic lifter preload is not even all across? Or valve heights different?)
2) In the same pix, the first rocker (on what appears to be a fully closed valve), looks to be contacting the valve tip waaaay over on the rocker side of the valve tip. This may be a good clue that the rocker shafts need shimming up (and perhaps the pushrods a bit longer to keep the rockers balls up high). It looks like the rocker contact point is 'walking' a long distance across the valve stem tip from fully closed to fully open. But I'll admit it is hard to really tell from just a pix.
Click to expand...

Hi and yes, you are very observant. They look like that because that's exactly how they are (even as we speak). When that photo was taken I was only working on one valve - the inlet of # 1 cylinder. That's because I had only modified one lifter for the measurements! It took almost 2 hours to make the solid lifter (from a 273) approx the same height as the hydraulic lifters that I will using (from pushrod seat inside the lifter to the base of the lifter). I originally installed the solid and it was too short. And not having an adjustable pushrod, I was forced to modify the lifter. Of course I didn't want to use the hydraulic because that will vary as you squeeze it tight. I am also still halfway in checking the degree of the cam - you can just see that degree wheel in this first photo, it is a Moroso super wheel that my friend had (yay) and lent to me. It is great, esp for me with older eyes (BTW the cam, a Comp Cams XE275HL-10, looks pretty well spot on for accuracy with the open/close points, so far). But anyway, all the other valves still had the original springs I was going to use (Trick Flow I think), along with 10deg retainers/locks. And the Isky rockers were just sitting there and I had only paid attention to the geometry of that one one valve. You can see in the second photo, only one pushrod is installed for that check. The others will all need attention, either billet hold downs or shims or both to get them correct. At this time I am just working out which are the lightest springs I can use for the cam break in period and I have two other sets to measure the pressure of. That was the reason for this thread, I was considering using the old OEM 318 springs for the cam break in and I saw that they had not reached spring bind, so that's why I wanted other people's opinions. But all things considered, I think it is too risky to use them, (esp on this valuable 1969 X head 340 engine) - they are old and not designed for that high lift, who knows what could happen, even if they didn't bind, one could break in the first 5 minutes and then disaster. Sorry for the long ramble!

reatiners.jpg


rocker adjuster.jpg
 
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