Topic: Setting Installed Height on CB750 valve springs

[MCRider]

I have diverted this from my "Phaedrus" project thread as it may better serve us as a stand alone discussion.  Setting valve spring height came up in a prior thread. MRieck shamed me into pursuing it. I hadn't ever on previous engine builds, but I had never heard of it.
Here is a good discussion. http://www.cranecams.com/?show=faq&id=5

So now that I know about it, and I am building what may be my swan song (who knows?) I want to do whatever I know is right.

So I have once again removed the springs from my head. But first I went to Harbor Freight to score some tools. A digital caliper, to the third decimal (with the fourth decimal alternating between "5" and "0"). For $10! and a measuring set which contained what I wanted, an internal spring divider, for $8!.


They seem to be decent quality.
So I reassembled the valves using only the internal spring. This allowed me to put the internal divider in for a measurement.

Then I measured the divider with the caliper.

In each case on the intake valves I got between 1.44 and 1.4555". (Saving the exhaust side for later)
MRieck indicated that an installed height might be 1.32 to 1.34" But we all have different components. He was referenceing Kibblewhite springs. I have APE springs, APE Ti retainers, recycled SS valves from Phaedrus I, I think they were Manley. And the ultimate variable was the valve job itself.

So tomorrow I'll call APE for their installed height.

In the meantime any comments as to my methodolgy?

I acknowledge that for my purposes (non-racing street bike), this drill may be overkill, but hey, its my hobby and its my therapy. I'd like to do it just to say I did.

[RRRToolSolutions]

Ron, your tools are fine and your method sound if you are supposed to be measuring the installed spring height. If it's valve height - then it's from the head surface to the tip of the stem. I think that's where it should be (based on my work with the Kawasaki head). The Hondas with their adjustable rockerarms are much more forgiving than those engines having shims. I rebuilt my 900 Kawi this year and with head/valve work and new valves, the installed height for each valve had to be recorded. Those were then compared to a chart which "approximated" the shim stock to be used on top of every valve.

This step is so common that Kawasaki sells a simple tool that fits over the valve stem and shows the right stem height. If too short - the valve has to be replaced, if too long - then the valve can be ground/faced a small amount (keepers require a minimum amount of stem be left on top of the groove). Outside of this and the valve and/or seat has to be replaced.

Regards,
Gordon

[MRieck]

 Your method looks OK. It really doesn't matter which retainers are used as you measure the height the same regardless of brands. The best thing to do is check the seat pressure when the spring is compressed to the installed height. You probably are at around 70lbs at that height which will work OK. If you put a .015 shim under the base you will get more pressure than you need.
  I've found it kinda odd APE does not supply IH numbers with the springs. I also wonder if Kibblewhite supplies APE with springs?

[RRRToolSolutions]

Mike, none of the springs I've gotten from Kibble White have had installed height specified. I don't remember seeing that spec in the 1.5" think factory Honda service manual. I'll have to give it another look. The Kawasaki manual has 2 full pages devoted to the specs, the checking, the adjustments, and the tables on "installed height".

I'l like to know what they should be once known.

Regards,
Gordon

[MCRider]

Mike, none of the springs I've gotten from Kibble White have had installed height specified. I don't remember seeing that spec in the 1.5" think factory Honda service manual. I'll have to give it another look. The Kawasaki manual has 2 full pages devoted to the specs, the checking, the adjustments, and the tables on "installed height".

I'l like to know what they should be once known.

Regards,
Gordon

I'm doing Googles on "valve spring heights" and variants. Seems the car guys are really into this. Found a special micrometer just for this: http://www.jegs.com/p/JEGS/753947/12552/-1

Mike you may have slipped a decimal on my readings. If 1.34 is the target, and I'm at 1.45, I'll need a .060, .030 and a .015 to get close to the 1.34. Not just the .015.

What type of device is used to check the seat pressure? I'm googling that right now, nothing yet.

I'll report back what i may hear from APE once they open.

[MRieck]

Mike, none of the springs I've gotten from Kibble White have had installed height specified. I don't remember seeing that spec in the 1.5" think factory Honda service manual. I'll have to give it another look. The Kawasaki manual has 2 full pages devoted to the specs, the checking, the adjustments, and the tables on "installed height".

I'l like to know what they should be once known.

Regards,
Gordon

Gordon
  All the sets of CB750 springs I've received from Kibblewhite have 1.320 to 1.340 on the label. Some of their kits don't list any height so I go by seat pressure.

[MRieck]

Mike, none of the springs I've gotten from Kibble White have had installed height specified. I don't remember seeing that spec in the 1.5" think factory Honda service manual. I'll have to give it another look. The Kawasaki manual has 2 full pages devoted to the specs, the checking, the adjustments, and the tables on "installed height".

I'l like to know what they should be once known.

Regards,
Gordon

I'm doing Googles on "valve spring heights" and variants. Seems the car guys are really into this. Found a special micrometer just for this: http://www.jegs.com/p/JEGS/753947/12552/-1

Mike you may have slipped a decimal on my readings. If 1.34 is the target, and I'm at 1.45, I'll need a .060, .030 and a .015 to get close to the 1.34. Not just the .015.

What type of device is used to check the seat pressure? I'm googling that right now, nothing yet.

I'll report back what i may hear from APE once they open.

Yep...you're right. Trying to do paperwork at work and type at the same time. I've got the correct shims if you need them.

[MCRider]

Mike, none of the springs I've gotten from Kibble White have had installed height specified. I don't remember seeing that spec in the 1.5" think factory Honda service manual. I'll have to give it another look. The Kawasaki manual has 2 full pages devoted to the specs, the checking, the adjustments, and the tables on "installed height".

I'l like to know what they should be once known.

Regards,
Gordon

I'm doing Googles on "valve spring heights" and variants. Seems the car guys are really into this. Found a special micrometer just for this: http://www.jegs.com/p/JEGS/753947/12552/-1

Mike you may have slipped a decimal on my readings. If 1.34 is the target, and I'm at 1.45, I'll need a .060, .030 and a .015 to get close to the 1.34. Not just the .015.

What type of device is used to check the seat pressure? I'm googling that right now, nothing yet.

I'll report back what i may hear from APE once they open.

Yep...you're right. Trying to do paperwork at work and type at the same time. I've got the correct shims if you need them.

OK, great, glad to know I'm thinking right. I'll measure all and let you know.

On the car guy sites, seems the proper way is seat pressure, but seat pressure test tools are $250 and up. Too much for me.

Installed height only assumes no variance in the quality of the springs, the car guys say the springs can vary a lot even from the same production run. So measure the pressure, and use that height for each spring is their method.

I'll see what APE says. Then I'll make the appropriate compromises.
Thanks!

[MRieck]

 I use my friends Rimac spring tester. They cost about 700.00. There are small units that aren't to expensive (I have one). They are not as accurate as the Rimac but they put you in the ballpark. APE used to sell them.

[MCRider]

I asked the flunkie at AutoZone for a valve spring pressure tester. They had one for $815, I'll pass. But he also has one for $35! I think the difference is the expensive ones are to check pressure while the spring is mounted. If the spring is loose like mine, maybe its cheaper.

Anyway I'll be going there this AM to see it. If its for real, I'll order it for 2 day delivery. Nice to have in the box.

And once again this is probably overkill for my type of riding, but every thing that I can do a little better than the last time I did it means progress.

[MCRider]

I use my friends Rimac spring tester. They cost about 700.00. There are small units that aren't to expensive (I have one). They are not as accurate as the Rimac but they put you in the ballpark. APE used to sell them.

Seems I just discovered what you are saying. Good news. So 70lbs is a good number?

And I assume I check the inside and outside spring at the same time? Measure the height at 70lbs and use that for my installed height?

[MCRider]

While waiting on my valve spring pressure tester I have searched for info on valve seat pressure.
Besides Mike telling me that 70lbs is good, I just wanted to see other references. I could find little
on the subject. I did find that 4-5 valve per cyl motorcycle motors have seat pressures of 40lbs or less.
A Corvair at around 120lbs (much bigger valves). Nothing for a CB750 size motor.

Andrews had a page on determining installed height. They say smash the spring to "solid" in a vice (be careful).
Then "Calculate INSTALLED SPRING HEIGHT (min.) as follows: INSTALLED HT.= Solid Height + .060 + Max. Valve Lift".
Seems to me that if ones cam has nominal lift above stock, this formula may leave one with huge seat pressure which is a drag on performance if not needed.

Any way, does anyone (including Mike Rieck) have an additional 10 words or less on the subject? Don't want to be a pest.

My projected procedure would be, compress the springs in the tester to 70lbs. (Mike's recommendation) Measure and that will be my installed height target. Each spring measured and shimmed appropriately. From what i have read springs even from same production run can vary a bit, so shimming them all to a certain seat pressure is the elegant thing to do. The seat pressure should be enough but not too much, as too much has no benefit and is a drag on performance.

[MCRider]

This from CraneCams indicates higher seat pressure is NOT a drag on performance:
"Common Misconception:
Many people mistakenly think that using higher seat pressures causes a reduction in the horsepower delivered to the flywheel because higher seat pressures (and also higher spring rates required for high performance) require horsepower to compress the springs. This thinking is simply incomplete! For every valve that is opening and its valve spring being compressed, another valve is closing and its valve spring is expanding. This expansion returns the energy to the valve train and the engine. This results in a net power loss of "0" hp. Many engineering texts refer to this as the "regenerative characteristic" of the valve train. Recent tests at Crane have shown no horsepower loss on a hydraulic roller equipped engine when changing the seat pressure from 135# to 165#. Power actually improved significantly at top end, probably due to better control of the relatively heavy valves in the engine.

In Summary:
Always run enough seat pressure to control the valve action as it returns to the seat. Heavier valves require more seat pressure. Strong, lightweight valves require less seat pressure. When in doubt, run slightly more seat pressure . . . not less. " end quote

Still it would be more of a wear and tear issue.

[MCRider]

No guidance on the issue of installed height or seat pressure from APE. Disappointing.

[MRieck]

In general.....2 valve engines 80 to 120lbs with larger cams and high revs (racing). 4 valve engines 40 to 60 same application. This is very dependent on how heavy the valve/buchet/shim is, use (occasional racing/dedicated racing), cam lift(s) etc. Street bike seat pressures should be a bit lower. Harleys run much higher pressures but their valves are automotive (big and very heavy). Always check to see where coil bind is too.

[MCRider]

In general.....2 valve engines 80 to 120lbs with larger cams and high revs (racing). 4 valve engines 40 to 60 same application. This is very dependent on how heavy the valve/buchet/shim is, use (occasional racing/dedicated racing), cam lift(s) etc. Street bike seat pressures should be a bit lower. Harleys run much higher pressures but their valves are automotive (big and very heavy). Always check to see where coil bind is too.

As always, thanks so much. Once I get my tools together I'll make my measurements and decisions. I like the idea of covering these bases. It differentiates this project from prior "shade-tree" projects. Which were very satisfying, regardless if less sophisticated. I'm just trying to one up myself this time.

[Big Jay]

Sorry we didn't have that old info. I told our phone guy to have you give us the valve tip to spring base pad ( under the spring base) and we would tell you what the pressure is.

We don't use installed height when setting up heads, we use assembled height. It is way more accurate. In the case of the 750, we put the retainer on a valve with keepers and measure from the valve tip to the top of the retainer. We subtract that figure from the valve tip to spring base pad and set the Rimac tester to that figure. Then we take the spring, spring base, and retainer and put it in the tester as an assembly and pull it doen to the set figure.

This way we are getting a reading that is exactly the same as the assembly will be in the head. This method takes into consideration, steps on the retainer and base for the inner spring etc. It is a real reading.

We do not have a 750 head in the shop at this time to get these measurements from.  Busas and GSXRs I can recite from memory.

Jay

[MCRider]

Wow! Thanks for the response and apologies for the negative remark. The phone guy (Pat) tried to relay your comments to me but the communication was weak and I couldn't decipher what he was getting at, your explanation was clear. I don't blame him any more than me.

I'll phone in that dimension Friday morning.

I've learned a lot through this process. One thing is that unless someone really wants to learn a lot of trivia and get their hands dirty, it may be more cost and time effective to let a professional set up the head.

I'm sure your GSXR abd Busa busines is the bread and butter these days. SOHC can only be a labor of personal interest, so thank you for taking the interest.

[Big Jay]

You got that right. Love the old Hondas as this is what I started APE doing.... Cast 836 kits by the hundreds

We developed the assembled height method when engines like the KZ Kawasaki came out, and the spring assembly is down inside a tappet bore. You can't get anything down in there to measure between the retainer and spring base.

I will tell you that Pat and Dustin came to me several times trying to get this info. They were really trying to help you out.

Jay

[MCRider]

You got that right. Love the old Hondas as this is what I started APE doing.... Cast 836 kits by the hundreds

We developed the assembled height method when engines like the KZ Kawasaki came out, and the spring assembly is down inside a tappet bore. You can't get anything down in there to measure between the retainer and spring base.

I will tell you that Pat and Dustin came to me several times trying to get this info. They were really trying to help you out.

Jay

Thanks for all that, and I think we were just suffering a "failure to communicate".

PS: I can't help but think Pat and Dustin probably weren't even born when these bikes were current!

[goon 1492]

Not sure if this will help much but I learned last weekend a tip on valve/piston clearence for v-8's (not sure how much it helps us). It stated using tootsie rolls, lay it on the #1 piston at TDC then install head/gasket, rockers, pushrods then turn motor over 306deg.
Then disasemble, carefully take tootsie roll and freeze it(for hardness) then mic the thickness of said tootsie roll, clearence should be no less than .07
I know thats for v-8's but the info was interesting and I wanted to share with others, Mrieck have you heard of this?

[MCRider]

Not sure if this will help much but I learned last weekend a tip on valve/piston clearence for v-8's (not sure how much it helps us). It stated using tootsie rolls, lay it on the #1 piston at TDC then install head/gasket, rockers, pushrods then turn motor over 306deg.
Then disasemble, carefully take tootsie roll and freeze it(for hardness) then mic the thickness of said tootsie roll, clearence should be no less than .07
I know thats for v-8's but the info was interesting and I wanted to share with others, Mrieck have you heard of this?

A little off topic, but good nevertheless. What I'm talking about is the valve spring setup, and how much seat pressure it will exert when closed.

Your example is for valve to piston clearance when the valve is open. I'm above the head, you are below it.

I know I'll be OK in the clearance area as my Arias pistons have valve pockets for big cams and I'm using something only slightly more than stock. But I think i will check it anyways as i never have developed that technique. Tootsie roll sounds good, or I've heard of a certain type clay being used in the piston pockets.

[goon 1492]

Yeah, I'm sorry its off topic but I had to share. I also forgot to mention that you get a treat after its done, and their basis behind the tootsie roll was the wax paper wrapper with its clay like core.

[MCRider]

Yeah, I'm sorry its off topic but I had to share. I also forgot to mention that you get a treat after its done

Oh no problem, just wanted to be clear. treats are always good. 

I should have my spring tester and data for the weekend, I can reassemble the head and move on.

[calikid]

Your method looks OK. It really doesn't matter which retainers are used as you measure the height the same regardless of brands. The best thing to do is check the seat pressure when the spring is compressed to the installed height. You probably are at around 70lbs at that height which will work OK. If you put a .015 shim under the base you will get more pressure than you need.
  I've found it kinda odd APE does not supply IH numbers with the springs. I also wonder if Kibblewhite supplies APE with springs?

is this correct? 70 lbs? I have a 1978 cb750f and im trying to figure out the valve spring pressure. to put my head back together. if not, what is the correct pressure