Ambient temp and cylinder honing

goodoldvic

goodoldvic

Senior Member
Hi, I'm looking for some feed back and guidance. I'm going to hone the cylinders in my car and fit oversize pistons. If the block, pistons and measuring tools, 3-4 inch Starrett outside mic and Mitutoyo dial bore gage are the same temp in my unheated garage, say 50 degrees, can I rely on my running clearance to be correct this summer. Thanx in advance for the feedback.
 
Interesting question for sure.

If your shop is 50 now, maybe compare to what the shop would be in the spring or summer, say 80.

Will there be some difference? prolly. Would it amount to .001? I do not know, prolly not. Possibly only 1/2 a thou.

I have a 1" gauge block. I should put it in the freezer and re-mic it and see what I get.
I will do that and post again. I will leave my mic at room temp, meaning 70. That way only one thing has changed.

In any case, I would suggest that selecting the correct number for clearancing your pistons in the first place would be the most important design factor

i am putting the gauge block in the freezer now.

I would love to hear from George on this.....
 
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goodoldvic said:
Hi, I'm looking for some feed back and guidance. I'm going to hone the cylinders in my car and fit oversize pistons. If the block, pistons and measuring tools, 3-4 inch Starrett outside mic and Mitutoyo dial bore gage are the same temp in my unheated garage, say 50 degrees, can I rely on my running clearance to be correct this summer. Thanx in advance for the feedback.
Click to expand...

When I'm doing the clearances for the mains and rods and it's cold,
I leave the heat on in the shop,...70° too 75°. I use a Sunnen dial
bore fitted with a Starrett tenth indicator(.0001") and Starrett mikes,
also in tenths. All related parts are sitting out and at the same temperature. Aluminum blocks and rods are critical on temperature and
with Aluminum main caps, iron caps on Aluminum blocks are a little
less sensitive.

I would use caution when honing not to raise the temperature of
the block(not a full length water jacket),......let the block cool, then
check the bore,...then repeat too the correct clearance.

Also,... that the master for the dial bore is also sitting out..
 
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Thanx for the response and experiment. I'm going for .001 per inch of bore. I'm fitting .055 over pistons so like .0035-.004. This knowledge gleaned from some more experienced people on this forum. Like you and Purdy
 
Dudley, when I am honing a block (Kwik-Way) honing machine, I start with #2, then I hone #4, then #1 then 3. That way each cylinder has a chance to cool/equalize with the honing oil flowing over the block.
 
BRENT in 10-uh-C said:
Dudley, when I am honing a block (Kwik-Way) honing machine, I start with #2, then I hone #4, then #1 then 3. That way each cylinder has a chance to cool/equalize with the honing oil flowing over the block.
Click to expand...

That's a good idea! Have you checked the block, say, 1 hour later
to see if it's changed?

You know, this whole topic could get messy.........lol
 
Really a simple, straight forward problem.

1st, since the outside mic and bore gauge are both steel, having the same thermal expansion coefficient, they will effectively cancel each other out if you only use them for a comparison at the same temperature. (They will not, however, read true to a gage block standard at 20C or 68F).

2nd, There will be a variance between the piston alloy and the gray cast iron. Let's look at that: The piston alloy has a thermal expansion coefficient of about 22 parts per million per degree Kelvin. Gray iron (the block) is about 10.5 P.P.M./deg K., a smaller coefficient.

The difference is 11.5 P.P.M/deg K, and since the coefficient is smaller for the block, at 50F you will find a four inch piston will show 0.000046" (forty-six millionths of an inch) more clearance than at the standard 20C/68F measuring temperature.

That means you will be 'off' by slightly less than one half of one TEN-thousanth if you measure with everything at 50F instead of 68F.

Since NOBODY in a shop with primitive tools like a micrometer and bore gauge can reliably and repeatedly measure in inches to the fifth decimal place you will be just fine. Just be careful not to hold that cold 3-4" mic in your hot hand too long or you will end up with a measurable error. Yep, you could calculate that, too.
 
Ha! :p OK, you guys have convinced me I know nothing about how to work on an engine, and should never try it again, even though I've assembled several without problems (that I am aware of). Ignorance is bliss, I guess. :o
 
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OK, I left the mic at room temp 70*
after an hr and a half in the freezer (30*) the 1" gauge block (a machinist's standardizing block by which to calibrate his mic) shrunk .0005 or half a thou.
so, for steel, anyway, a 40* drop in temp got a .0005 shrink.
This shrink would obv. be less than .0005 at a 20* change in temp as you are proposing (70*-50*).
So, in my mind anyway, the temperature differences you are proposing would not be a problem. In any case, I myself would be comfortable with these differences.

I am attaching a pic of a Brown and Sharpe 1" gauge block

Looks like Mike and I got to the same point using different methods. Which is super; good to have confirmation of a method

I agree on being careful of the temp of cyl walls when honing and measuring.
 

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So MikeK, the temp being the same for all materials involved in my project means that I would have that fifth decimal point towards MORE running clearance? If that's so looks like I'm good to go. The knowledge on this site is invaluable. FYI for all, these are Egge pistons and I'm fitting .060 os Hasting rings. I will post my results in a few weeks when I'm done. Thanx again to all who've responded and helped in the past.
 
goodoldvic said:
So MikeK, the temp being the same for all materials involved in my project means that I would have that fifth decimal point towards MORE running clearance? If that's so looks like I'm good to go. The knowledge on this site is invaluable. FYI for all, these are Egge pistons and I'm fitting .060 os Hasting rings. I will post my results in a few weeks when I'm done. Thanx again to all who've responded and helped in the past.
Click to expand...

You would have 0.000046" LESS clearance when the piston and block go from 50F to 68F. Still, essentially nothing even measurable.

A really good engine builder will get the clearances within a few tenths of the desired set point for a particular build. 46 millionths is less than one half of one ten-thousanth. A non-issue.
 
Even if honing or machining are done perfectly in a controlled environment, there is no way to perform quality control checks during assembly if the assembly room and the components being assembled are not temperature controlled.

All quality micrometers are designed to be used at a standardized temperature, usually 68 degrees F.
 
Oh and don't forget to check your ring gaps!
This will stir up the hornet's nest again but we use .022 for top ring (subjected to the most heat and therefore the most expansion) and .016-.018 for middle and oil. Be sure to stagger the gaps

I have worked on motors that would lock up hot because the builder failed this simple step

remember the old adage, 'there is never time to do it right but always time to do it over'
 
I have seen 2 sizes mentioned, .055, and ,060, I am curious what size the cylinders are now, and how much material you intend to remove with a hone, and what kind of hone you are using,

For temperature compensation it should be easy for you to check using the standards for checking your measuring instruments ( what do you use to check the accuracy of your micrometer and bore gauge)---if you have the standards cold, the micrometer warm--then have the micrometer cold and the standards warm it will be easier to see what compensation you will need for working "cold" ---if you are trying to freehand hone quite a bit of material in a worn tapered out of round bore there is more of a chance of not having the bore square to the crankshaft than changing a round true bore .005 with a rigid hone---if you are usiing a flexible spring loaded hone you don't have much of a chance at round and true no matter what the temperature
 
The mic is calibrated using the 3 inch gage that came with the micrometer. The bore gage I check by turning the thimble on the mic and watching the needle move. I've had these tools for years and they work great. The engine is .045 over now with bores that measure 3.918- 3.928 taper, tight at the bottom and they are round within .003. The size .060 refers to the os ring size I'm gonna fit as I cannot find .055 os rings on the market. The boring, honing ring fitting procedures are not foreign to me I was a Harley tech and regularly used a serv-equip boring bar and rottler powerstroke hone. This work is being done with a lisle ridged hone and 1/2 gear drive drill, by hand,a set up I have used in the past on flathead dodges, sb chevys and other pieces of power equip. My question was about the cold temp in my garage and doing the work. I will follow up with my results when completed.
 
700rpm said:
Ha! :p OK, you guys have convinced me I know nothing about how to work on an engine, and should never try it again, even though I've assembled several without problems (that I am aware of). Ignorance is bliss, I guess. :o
Click to expand...

Ray, the man asked a technical question that 99.9% of the fellas here
on the Barn never thought about,....and there are some sharp guys
on this sight! The Model A is a low compression, low RPM engine, much
different than that of a high performance engine.

I'll give you some things to think about,..that I do....

When I'm having an engine align honed, and the oil pump is bolted
too one of the main caps. I bolt a dummy pump to the cap to distort
the cap,.....so when it's done the bore is round. Ya,..we even talked
about running the pump with pressure too distort the cap even further.

Torque plates too distort the block for boring and honing. I believe
the "big 3" do this on the cars we buy.

Pumping hot water in the block when boring and honing to simulate
when the engine is running at temperature.

I have more,...but you get the idea...
Dudley

Also, on mikes and standards,....All of my stuff "reads" the same, and that
includes the dial bores. The shops that I do business,...I make sure that
we all read the same. If not,...they will use my tools to do the job, so we
have no surprises.
 
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Are we guilty of being TOO anal in our engine machine work? :D
.......(And to think the Fine-Point resto guys are considered too 'anal'!!
ROFL.gif
)


OHHH, and here is one..... Did y'all know there is at least one guy participating in this discussion who gathers up all of his mics., dial bore gauges, and standards a couple times a month, then he meets other guys for lunch where they can sit around checking all of their measuring equipment against all of the other's measuring tools just to see whose is the most accurate!! Can anyone guess who it is??
LOL.gif
 
d.j. moordigian said:
Ray, the man asked a technical question that 99.9% of the fellas here
on the Barn never thought about,....and there are some sharp guys
on this sight! The Model A is a low compression, low RPM engine, much
different than that of a high performance engine.

I'll give you some things to think about,..that I do....

When I'm having an engine align honed, and the oil pump is bolted
too one of the main caps. I bolt a dummy pump to the cap to distort
the cap,.....so when it's done the bore is round. Ya,..we even talked
about running the pump with pressure too distort the cap even further.

Torque plates too distort the block for boring and honing. I believe
the "big 3" do this on the cars we buy.

Pumping hot water in the block when boring and honing to simulate
when the engine is running at temperature.

I have more,...but you get the idea...
Dudley

Also, on mikes and standards,....All of my stuff "reads" the same, and that
includes the dial bores. The shops that I do business,...I make sure that
we all read the same. If not,...they will use my tools to do the job, so we
have no surprises.
Click to expand...

Thanks Dudley. This thread discusses stuff I have never even considered, hence my comment. And it's also why I take my engines to pro shops for all machining and limit my participation to reassembly. I am solidly in the 99% and fully aware of my limitations! :p
 
tbirdtbird said:
Oh and don't forget to check your ring gaps!
This will stir up the hornet's nest again but we use .022 for top ring (subjected to the most heat and therefore the most expansion) and .016-.018 for middle and oil. Be sure to stagger the gaps

I have worked on motors that would lock up hot because the builder failed this simple step

remember the old adage, 'there is never time to do it right but always time to do it over'
Click to expand...

It has been my experience that piston/cylinder clearance is not that critical provided it is sufficient. Goodoldvic in post #4 alluded to it but did not press the issue. I was always taught that the minimum clearance is 1 thou plus 1 thou per inch of bore. This gets more interesting when considering slipper pistons, or as I have used, pistons relieved on the sides below the piston pin by use of hand file!

But as tbirdtbird states, piston ring fitting is very important in ensuring a long lasting and good running engine.

Ian
 
Here's whats been going on in cool jersey. I honed my cylinders, fit the pistons for .0045 clearance. Had new wrist pin bushings honed for the new pins. Set my ring end gaps as suggested on the site. Before I put the pan on I checked the clearances on the rods and mains using the tin foil method. (There are no shims left in this engine) Bolted the rest together, oil down dist hole, oil in the pan, water in the radiator. The car started right up and runs so smooth. Nice throttle response, stopped smoking after like five minutes of running. Took it out for a 10 mile run to get it up to temp, then into the garage for the night. Next morning re-torqued the head using the loosen, then torque method. Took the car out for a 30 mile run, I'm very pleased with my results ran it up to 30 mph in second gear like ten times to seat the rings in. Runs and sounds great. No here comes the pain....on the way home from this drive I wound it up in third, as the speedo passed 55 mph I heard the dull metallic knock, let off the pedal no knock, cruise and the knock is light but you can hear it. If you put any load on it it knocks, retard the timing and it goes away alittle. Dropped the pan and the center main is hammered. I wanted to get the summer out of this engine before It went for a complete rebuild but..Engine going to Schwalms for a long block, crank flywheel and pressure plate balance. I'm out about 200 bucks in pistons rings and gaskets.
 
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