Cylinder bore honing.
 

Anyone have a preference as to the process of honing a cylinder and how straight and round it should be when done??
Steel plate, aluminum plate, studs, bolts, lubes, torques, etc.
Then what about measuring process, how do you know it measurements are real?

Seems there are a lot of opinions on it. I am referring to a Dart Big M block.

Thanks
Dick

has to do with the rings you are going to be running...different ones want a very specific finish...and it is important...Rob

I have been talking to Dick extensively on this. He doesnt mean what grit stone or type of finish. He is questioning some of measurements he is getting when checking the bores for piston to wall clearance and being round and straight.

You need a dial bore gauge that moves up and down in the cylinder and you can watch the reading on the dial indicater as you do so. This will show you low and high spots. You can then use a inside mic to measure the cylinder and then measure the inside mic with the outside mic which you are using to measure your pistons with. This is unless your positive your inside mic and out side mic are perfectly calibrate the same.

I ask my builder to use a steel plate when honing my motors. Good builders will have plates for applications using head studs and non-studded applications. I always have them use non-studded head bolts, as I want to be able to get the heads off without having to pull the motor.

I would say that more than .0005 out of round should be unacceptable. I have a 4-5" mic that I use on my pistons (at room temp) and I measure the bores of my motor at room temp in multiple locations. The only really good way to check the run-out (or straightness) of a bore is to use a CMM. You can kind of use a dial indicator, but you'd need an angle plate mounting system and a precision rotating device. You may be able to do it on their setup, if they let you.

These work very well. Pricey, but accurate.

http://www.sunnen.com/ProductDetails...D=23&NavID=666

Sunnen's are great.

I should have added... Don't buy or use one of those junk gauges from Summit. They're terrible. If you're getting bad readings with one of those things, it is just as likely to be the gauge as it is a machining problem (maybe even more likely to be the gauge).

Thought maybe some of the Big Engine Builders would share a few secrets, or a least tell you what you should be looking for.

I don't build marine engines, but I have built hundreds of race engines that are in the $20k-60k range. No junk, I have been in a premeir engine shop for almost 2 decades... To measure the bore after the plate is taken off is a waste of time. the bore needs to be measured with the plates on by your machinist. This is why you need to drop off your pistons when you drop the block off to get honed.
The type of plate matters, but it isn't as critical as some might say. On a Sprint Cup or a Pro Stock engine we try to simulate the head as close as possible, but we are looking for 1-2 hp. The most important aspect of a plate is how it simulates how the fasteners pull on the cylinder walls. The actual fasteners, lube, torque and gasket need to be used when honing. I try to use Cometic MLS gaskets on everything I build. I use the actual gaskets to hone with, then clean them and use them in the build.

I hope I answered your questions.

Fresh hone with torque plate, the cylinders are barrel shaped. I think the question is how straight and round do they need to be, or should they be.

The bore will move a good bit after the plates are taken off. If the bores a dead straight, there is a good chance plates were not used. Aftermarket blocks are more stable than stock blocks.
I think .0004-.0005 is acceptable. Those numbers will hurt your feelings if you write them on paper, because engine builders like things to be "perfect", but I don't feel as if you would see any performance loss.

make sure the piston measurement is taken at the correct guage point on thr piston with a micrometer. This guage poit varies greatly from piston manufacturers. See you piston spec sheet foe where to measure. Than transfer that measurement to a dial bore gauge. Actually the gauges from Summit and Jegs work well. They are not as good as a Sunnen, but who has $1200 laying around to buy a tool that will only be used a few times.
If you are truely concerned, torque the heads on the bare block, flip it over on the stand and measure the bores with your gauge from the bottom.

All good info!! Thank you all for you comments.

Please keep them coming!

How far are you from Dart, it's their block maybe have them bore and hone it to fit the new pistons.

Hey Dick - give Joe Soller a call at Champion Performance 586.755.7400 a shout. He does the majority of the machine work for the area performance shops as well as their own builds. He'll be able to get you setup or can do the work for ya. Tell him Neil sent ya.

Dick,

I try to get bores within a couple of "tenths" .0002" from top to bottom. It takes a lot of time to do this properly. I always let the block cool off for an hour or so before a final measurment and hone, they will move around a little as they cool off.

Although I have tried as hard as I can, I have yet to see a Dart block move more than a tenth or so when you put a torque plate on it ?? GM blocks certainly move, but I have yet to see it on a Dart block. I still use the plates, but really wonder sometimes if you need them on the Dart's :)

Also, as some others have mentioned ...... you CANNOT measure roundness with a bore gauge. Only size between 2 points on the cylinder. Only a CMM or laser type measuring device can tell you if the cylinder is actually "round"


Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Thanks Bill, that is the info I am looking for. Trying to learn something as go. Tell me what a DMM is. I would like to see info on that process.
Hearing a lot of ideas on how people look at this subject. Very interesting! Motor building has always had a lot of questions in my mind.

Dick

I would also plate hone it with the same head gaskets you intend on running also

Dick - I think you mean CMM. It's a coordinate measuring machine. It's a very precise robotic measuring device. I use to program one for an aerospace company, and prototype stamping company. We did the Cobra R parts, and the gen 1 dodge Viper prototype work.

It costs about $165 per hour to use one, plus programming time. Not really feasible for engine measurements.

Thanks WJB.. I kind of figured it was a high dollar experience.

Thanks!
Dick

Why aren't the blocks and internals heated to operating temp to simulate true running condition when doing the machine work? It seems, to me, that by checking it while cool will make for a perfect motor before it is started, then moves away from that perfect motor as it heats up.
Thanks

Engineers build and tolerace components to measure properly in a controlled environment (generally room temperature, with a controlled humidity level). I use to have to keep logs of the temperature and humidity levels in my office (where I did plate measurements) and in the CMM room at ACR - an aerospace company. They do this on purpose. It creates a lab setting with a "control" atmosphere. It's the only way to get true #'s. You can't really measure something accurately at 200-300 degrees. Everything is toleranced to "nominal" and engineers account for heat expansion with controlled #'s added later.

Your motor is actually designed to run with X bearing clearances and you achieve those clearances by machining them to the tolerances recommended, and then heating up your motor. That's why you're supposed to warm your motors up before you beat the snot out of them...

Also, different metals react differently. Some metals expand I.D. bores when heated, and some actually shrink lightly. It depends on the grain of the metal and the type of alloy... It's a science and they've researched it for hundreds of years, and dedicated college degrees to understanding it. I'd except it as the best way. There's no sense in trying to re-invent the wheel on something that they've virtually perfected.

Interesting thread. I too wonder what effect the change in temperature has on bore distortion. Seems to me you want the bore round at running temperature as long as the pistons/rings are round too. Aren't pistons somewhat oval at room temperature so they are round at running temperature? I believe the effect thermal expansion has on cylinder roundness has a lot to do with the uniformity of cylinder wall thickness and design, as well as material grade. The attached link shows equipment used to hone blocks at running temperature. According to the graph the cylindricity (roundness) of a cast iron SB-2 block changes .001 from room temp to 220F. An aluminum Brodix changes .003.

btw, I have no idea if this equipment works well or the validity of their claims, I just came across it...

http://www.c-ktechnologies.com/images/hothone.pdf

Oh the Hone Hone........ There has been great debate on hot honing. Some say its nessesary some say its a waste of time.
Many times we do things because we can, not because we need to. The bottom line on clearances in an engine comes down to trial and error. The actual piston to wall at temperature is near 0, but cold it may be .010 depending on the application. The Idea is an aluminum piston grows at a greater rate than the cylinder bore. At operating temperature the piston will grow enough to take up most of the claerance, but not seize.
I don't set my bearing clearance to what a book says, instead I set it according to how the last set of bearings looked upon tear down.
I think I just confused myself.......:drink:

"Build it tight, and everyone will know. Build it loose and no one will know but you..."

We had nitrous motors that we built at 0.010 piston to wall clearance, and only ran one ring. The motors were so lose that they would have a slight knock at idle, but they would sound great at 2500 rpm staged up and run like a raped ape...

I would never recommend that for anyone running a motor on the street, or in a marine app, but the point is that build clearances vary from application to application.

Got to wonder what's happening inside the blower motor when the water temp is less than 100 and the Egts are 1400

I have always loved that saying! It is very true! :)

I am certain that finishing the block at operating temperature is absolutely the best way to achieve the best cylinder sealing and enable you to run the tightest running clearances. But .... the guys that do this, mainly the Nascar teams, also have elaborate rigs to heat the engines to operating temperature before they are started on race day. If they did not heat the engines prior to starting them, there is a good chance that damage would occur.

In the real world, you have to compromise. You have to build an engine knowing that the owner might decide to go for a ride on 40 deg day and not warm it up :( Manufacturers design pistons, bearings and other parts with this in mind.

not all the NASCAR guys hot hone ;)

Great thread, these are all questions I have had before. There is good reason to not reinvent with the wheel with every build. Thanks.

I was thinking the same thing!

This is why serious auto race engines stay plugged into an oil heater before going onto the track. Cold coolant temp is not so bad, cold oil is REALLY bad!:eek:

Very good point/question, I have wondered the same thing. I can tell you from my own experience that dart big m blocks are very stable and mine was honed on a steel tq plate but my machinist said the same thing that was mentioned earlier, these particular blocks are so thick and rugged that the measurements don't change much from having the plate on to having it off, as far as how much it changes at temp I don't know. I also have kept my cylinder bores at 4.500 instead of trying to gain a few cubic inches at the exspense of wall thickness, I believe that the amount of side load/cylinder load when making 140 hp per cylinder is extreme and having as thick of a cylinder as possible helps to hold it somewhat stable when running hard, just my opinion though, Smitty
My cylinders varied by .002-.003 max when checking them with a dial bore gauge after all machine work was done and block was back at my own shop with no tq plate on it, Smitty

Here is a really good thread on Speedtalk. Speedtalk is a great site for engine building. Not much flaming over there either, its pretty cool.:
http://speedtalk.com/forum/viewtopic.php?f=1&t=24533

Smitty,

Are you sure they were .002"-.003" and not .0002" - .0003" ??? If they really did vary 2 to 3 thousanths, you need to find a new machine shop :( Clearance on some pistons is only .003" ..... if the bores varied that much the engine will never be right.

Just my opinion,

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

That was with out plate torqued on it.