modok wrote: ↑Mon May 07, 2018 8:44 pm
Just in case, you didn't mention....
Was a torque plate used?
Are the skirts coated?
And have you checked the actual clearance comparing skirts to block bore.... or just bore size?
Pistons are getting really good, but I still like to check each one just to be sure.
I;ll assume at worst there could be .0005 difference in measuring due to being a different hand using different measuring equipment, and on a "home gamer" level that could be twice as much. Nothing personal, but it would not be the first time at all.
If the cylinders were heated....they would be larger. They are blowing smoke. But did you buy that?
Giving more info:
a torque plate was used during hot honing.
My digital micrometer correctly reads what manufacturer claims on the spec sheet (3.3925), so my digital bore gauge should really see .0032 more in the bores.
And yes, I was too thinking that they should be larger when heated!
I'm going to get there and see when heated then
Are you taking your readings near the top where torque plate / no torque plate will make a difference?
Might try measuring low in the cylinder.
Are both parties measuring the piston skirt in the same location?
I will assume that you have some kind of master gauge you set the bore gauge with.
Might take your digital mic and use it on the bore gauge to see if they agree.
Were the pistons soaked in the same heated oil?
If this is a race engine will the extra clearance hurt performance? Doubtful.
Dave Koehler - Koehler Injection Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Dave Koehler wrote: ↑Tue May 08, 2018 8:36 am
Are both parties measuring the piston skirt in the same location?
Excellent point. Piston manufacturers determine the location at which piston diameter is to be measured and the measurements must be taken at this exact location in order to be correct. Just another of the many important details to be considered when dealing with performance engines . . . . .
Bill
Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist
Since a torque plate was used, the cylinders will not be true without the plate. Right?
Although the HOT honing was a red herring..... It is HIGHLY likely that the top and the main thrust area of the cylinder will actually measure smaller with the torque plate in place. Especially if the head bolts are not directly attached to the cylinder itself, torquing the bolts will COMPRESS the cylinder and make the top half smaller.
If I was asked to measure this for clearance without the plate on it, I would measure the diameter of the cylinders around the bottom third of the bore and call that the diameter. NOW what is the clearance?
What did you measure that with you canbarley read that on a bore gage if your that particular i suggest you spend $150,000 by yourself a Rottler CNC machine and do it yourself
Keith Morganstein wrote: ↑Sun May 13, 2018 6:46 pm
When I saw this title, at first I thought it was “Engine machine shop destroyed my back”
I was like, oh yeah, my back, my shoulders, my hands, my knees, my hearing...
True Dat!
Dave Koehler - Koehler Injection Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Instead of suggested piston to wall clearance shouldn't .0032 be the minimal piston to wall clearance with a tolerance of up to.005 +-? It's not perfect maybe even a tad sloppy from some machine shop standards but depending on your RPM range if it's not a terribly high performance Engine I'd run with it
modok wrote: ↑Mon May 07, 2018 8:44 pm
Just in case, you didn't mention....
Was a torque plate used?
Are the skirts coated?
And have you checked the actual clearance comparing skirts to block bore.... or just bore size?
Pistons are getting really good, but I still like to check each one just to be sure.
I;ll assume at worst there could be .0005 difference in measuring due to being a different hand using different measuring equipment, and on a "home gamer" level that could be twice as much. Nothing personal, but it would not be the first time at all.
If the cylinders were heated....they would be larger. They are blowing smoke. But did you buy that?
Giving more info:
a torque plate was used during hot honing.
My digital micrometer correctly reads what manufacturer claims on the spec sheet (3.3925), so my digital bore gauge should really see .0032 more in the bores.
And yes, I was too thinking that they should be larger when heated!
I'm going to get there and see when heated then
This may be a silly question but just making sure did you calibrate your bore gauge with a mic that you measure the Piston with to make sure it was on zero before you measure the bore or are you just using the digital readouts of each to give you the sum of the differences
Without calibrating the two measuring instruments to each other?
B Original wrote: ↑Sun May 13, 2018 8:18 pm...
And yes, I was too thinking that they should be larger when heated!
I'm going to get there and see when heated then
The heat expansion can be more accurately calculated than measured. The coefficient of thermal expansion for cast iron is 6 ppm, so say a 4.000" bore heated from 70°F. to 200° would expand by (6 x 4 x 130)/1,000,000, or 0.00312".
B Original wrote: ↑Sun May 13, 2018 8:18 pm...
And yes, I was too thinking that they should be larger when heated!
I'm going to get there and see when heated then
The heat expansion can be more accurately calculated than measured. The coefficient of thermal expansion for cast iron is 6 ppm, so say a 4.000" bore heated from 70°F. to 200° would expand by (6 x 4 x 130)/1,000,000, or 0.00312".
although your calculation is spot-on what about the thermal expansion of the aluminum piston somewhere between 10 and 13 parts per million per degree Fahrenheit? Approximately twice rate of expansion as the iron
By the way my memory does fail me sometimes but I just don't remember posting this?
Last edited by B Original on Sun May 13, 2018 9:27 pm, edited 1 time in total.
B Original wrote: ↑Sun May 13, 2018 8:18 pm...
And yes, I was too thinking that they should be larger when heated!
I'm going to get there and see when heated then
The heat expansion can be more accurately calculated than measured. The coefficient of thermal expansion for cast iron is 6 ppm, so say a 4.000" bore heated from 70°F. to 200° would expand by (6 x 4 x 130)/1,000,000, or 0.00312".
although your calculation is spot-on what about the thermal expansion of the aluminum piston somewhere between 10 and 13 parts per million per degree Fahrenheit?
By the way my memory does fail me sometimes but I just don't remember posting this?
Sorry about that, in trimming the original, I snipped John@RED out ( his post is a few above), leaving you as the apparent author.
And yes, an all-aluminum piston will expand at about twice the rate of the bore, but that's really a separate issue.
MadBill wrote: ↑Sun May 13, 2018 8:48 pm
The heat expansion can be more accurately calculated than measured. The coefficient of thermal expansion for cast iron is 6 ppm, so say a 4.000" bore heated from 70°F. to 200° would expand by (6 x 4 x 130)/1,000,000, or 0.00312".
although your calculation is spot-on what about the thermal expansion of the aluminum piston somewhere between 10 and 13 parts per million per degree Fahrenheit?
By the way my memory does fail me sometimes but I just don't remember posting this?
Sorry about that, in trimming the original, I snipped John@RED out ( his post is a few above), leaving you as the apparent author.
And yes, an all-aluminum piston will expand at about twice the rate of the bore, but that's really a separate issue.
It's all good bill you're definitely a friend and not a foe LoL
And yes I understand it's a separate issue about the Machining but I was putting it into context of calculating the clearance between the two
Basically you can't measure the bore sizes correctly unless you re-install the torque plate. You could fit the head with the head gasket, studs with proper lube and torqued to spec and fit the mains and torque and then measure from underneath to get a bore size. This may give you some idea but it still does not allow for the hot honing. The expansion rates of this cannot really be calculated either as different parts of the block will have different structure, density and variations in thickness which will all affect the expansion rate. I would be very surprised if a shop, that is so fastidious with their process [hot honing], would give you a crude backyarder result. Any shop that sets themselves up to do hot honing is obviously looking for that last bit of perfection so it does not make sense that they would leave it at .0015" oversize. I hope this helps.