dumb question about head clearance

[Terry Flynn]

OK guys heres a dumb question. I have a speedmaster head clearance gauge that I have been using with no problems. well the other day a buddy at work and I were talking about a different way to check head clearance, here it is. I have some 30 thousands thick solder and I placed it on top of the piston rolled the engine over got a squash and measured it with a pair of calipers.

Now when I measured it with the Speedmaster gauge it said that I had 12 thousands now when I used the solder I got 22 thousands. I checked this engine several times with the same results. I also checked a few different ones and I got the same results about 10 thousands deferent's what am I missing.

Terry

 

[Chris Wood]

terry,

does the piston have a dish in it.. maybe the solider is sitting in the dish.. if not i am not sure what else to say.. unless you speedmaster guage is off??

chris

 

[Terry Flynn]

terry,

does the piston have a dish in it.. maybe the solider is sitting in the dish.. if not i am not sure what else to say.. unless you speedmaster guage is off??

chris

Hi Chris

No dish in the piston, I have the solder to the edge of the sleeve and run the piston up so it shouldn't matter if there was a dish it's on the outer side of the piston. Speedmaster gauge off? never thought about that I'll have to check it. Thanks

Terry

 

[Twinsrule]

maybe you have wear in the connecting rod.

 

[DaveMarles]

You will always get a difference between the two methods simply because with the solder method you are pressing hard down on the piston taking up the clearance in conrod, bearings etc.

Dave

 

[bzubee]

also the head button usually has a taper so it depends on where you are measuring.

 

[Topfuel666]

You will always get a difference between the two methods simply because with the solder method you are pressing hard down on the piston taking up the clearance in conrod, bearings etc.

Dave

Hey Guys,

As soft as solder is, I don't think it will get fully compressed (rod end play, etc). When building 4 cycle engines, I always used Plasti-guage to check valve to piston clearance. A lot of folks also used it to check bearing to crankshaft clearance. Cheap stuff and easy to use. When you get to tolerances this close, I would not rely standard calipers but instead use a small micrometer.

My .02

Bill Kozuck

 

[PHM Racing]

The reason you are getting a false reading is that the solder is expanding by 10 thou. after it has been compressed this will happen with play dough also .

When we do our drag racing motors there's no room for error so the best thing to use is plastersen it hold it's size 100% after being compressed.

Put a little oil on the head button and on the piston top so it dosen't stick to either part.

After you have compressed the plastersen slice it threw the middle and measure it with your caliper's and that will be your head clearance .

We've done hundred's of motor's this way and never had a problem , Hope this helps

 

[Joe Warren]

OK guys heres a dumb question. I have a speedmaster head clearance gauge that I have been using with no problems. well the other day a buddy at work and I were talking about a different way to check head clearance, here it is. I have some 30 thousands thick solder and I placed it on top of the piston rolled the engine over got a squash and measured it with a pair of calipers.

Now when I measured it with the Speedmaster gauge it said that I had 12 thousands now when I used the solder I got 22 thousands. I checked this engine several times with the same results. I also checked a few different ones and I got the same results about 10 thousands deferent's what am I missing.

Terry

Terry you have the tool (Accucheck) it is the best way to check the Head clearence. if used properly it is dead nut accurate. CMB actually uses a Depth mic with the head removed to make the readings. & Terry keely use to make a tool that had diffence sizes or prebent hard wire Like a GO - NO GO. the solder is a poor way of measuring the squish band this is why the Accucheck was invented...... B)

 

[Don Ferrette]

Terry Keeley use to make a tool that had diffence sizes or prebent hard wire Like a GO - NO GO. the solder is a poor way of measuring the squish band this is why the Accucheck was invented...... B)

Terry still makes the head clearance guages & they are now available down to .008". You can purchase them through Gary Pruesse @ G&M Models. I have been using Terry's guages for a number of years now & they work real well. B)

 

[DaveMarles]

The reason you are getting a false reading is that the solder is expanding by 10 thou. after it has been compressed this will happen with play dough also .

When we do our drag racing motors there's no room for error so the best thing to use is plastersen it hold it's size 100% after being compressed.

We've done hundred's of motor's this way and never had a problem , Hope this helps

I'm not saying which is the best way to measure but I know plenty of people who use the solder method successfully. I don't know what solder you use but the solder I have does not expand 10 thou after after its been compressed. I just did a test on some 27 thou thick solder. squashed it between the caliper jaws down to 16 thou, took it out , remeasured it and it was 16 thou.

 

[AWaddle322]

If you do not get the solder over to the edge of the sleeve you will never get an accurate measurement as most motors do not have a flat squish band. Also you have to measure the very edge of the solder. The thinner the solder the better.

Most of the time I use Terry gauges.

Allen

 

[Terry Keeley]

Actually they do 0.006"- 0.016", Gary Preusse has them:

https://www.intlwaters.com/gallery/displayimage...m=70&pos=32

(end shameless plug)

I also use solder but you have to be careful to get it all the way to the edge and if the squishband is tapered all the way (no flat spot) you have to be sure to measure only the edge. Also, you can get a little "burr" when the solder goes into the space left by the champher between the head button and clylinder wall, I just trim that with an x-acto blade.

 

[mark voorhies]

Actually they do 0.006"- 0.016", Gary Preusse has them:
https://www.intlwaters.com/gallery/displayimage...m=70&pos=32

(end shameless plug)

I also use solder but you have to be careful to get it all the way to the edge and if the squishband is tapered all the way (no flat spot) you have to be sure to measure only the edge. Also, you can get a little "burr" when the solder goes into the space left by the champher between the head button and clylinder wall, I just trim that with an x-acto blade.

Terrys guage is very accurate if used correctly, must be positioned at I.D. of sleeve wall, if you

need to know lower than .006, or want to know each .001, you can cut feeler gauges, heat,

and bend to your needs.

 

[jeff baham]

when useing the accucheck, i set my pointer to zero while the head is still tightened by the water jacket, then i remove the head and place it on apiece of glass, this has been very accurate for me,