Would you try this

[northeastconfederate]

I have a couple of Harley cylinders which have been sleeved, and the base gasket surface was poorly finished. There are at least 2 "steps" on the sealing surface, fairly close to the spigot. The result is a pair of cylinders that leak profusely! Also, the head gasket surface is poorly finished. Flat, as far as I can tell, but very course finish, and the head gasket manufacturer is very specific about surface finish: They want a RA of 58, which is very smooth.

This is the third time I've had this apart, the previous two having had it back to the machinist to clean up these surfaces and make them flat, and they still aren't. So, I am now very seriously thinking about attempting to fix this on my South Bend Heavy 10. I think I remember seeing someone on here several years ago who was using his SB 9" to machine old Porsche heads, so I don't really see any reason not to try it. Thoughts?

I also need to machine the head gasket surface of the heads themselves, to reduce combustion chamber size. I'm not sure the heads will fit on a 10" swing lathe, but if the do I think I'm going to bolt them to my faceplate an let her rip.....

 

[Ken-Bergen]

I would think it's doable but depending on how much has been taken off the surfaces already and how much you need to take off I could see pistons and heads meeting and they wouldn't be happy about that.

 

[promacjoe]

Something else you need to worry about, if you get the compression to high, it will start pre-igniting the fuel and make it difficult to turn off without turning off the fuel. Anything over about 13 to 1 compression ratio will give you problems. 11 to 1 compression ratio is average for most engines. Although some newer engines have a higher compression ratio.

Note: any carbon buildup within the cylinders can raise the compression ratio causing pre-ignition. Because of this, the compression ratio should be kept on the lower side. Check your manual for the recommended compression of your engine.


Remember anytime you compress a gas, you compress the heat within that gas. The temperature rises with the pressure.

Stay safe and have fun.

Joe.

 

[Big B]

I would have thought that the average compression ratio for most modern engines to be around 8.5 to 1 or 9 to 1. The piston sets and heads that I see in summit catalogs that are 11 to 1 are referred to as high compression. I do have to admit that I am a little out of the engine loop so things may have changed while I wasn't paying attention. lol

Big B

Something else you need to worry about, if you get the compression to high, it will start pre-igniting the fuel and make it difficult to turn off without turning off the fuel. Anything over about 13 to 1 compression ratio will give you problems. 11 to 1 compression ratio is average for most engines. Although some newer engines have a higher compression ratio.

Note: any carbon buildup within the cylinders can raise the compression ratio causing pre-ignition. Because of this, the compression ratio should be kept on the lower side. Check your manual for the recommended compression of your engine.


Remember anytime you compress a gas, you compress the heat within that gas. The temperature rises with the pressure.

Stay safe and have fun.

Joe.

 

[promacjoe]

Flathead engines were considered low compression engines, and that was about top end of the compression for those engines. Overhead valve engines raised the compression up to about 11 to 1. High-performance engines can go slightly higher than that. There is a limit, and it depends on the temperature. In colder climates you can get away with a slightly higher compression. That is until the engine warms up good. Then it will give you problems. 13 to 1 and above is in the diesel range. Not good for a gas engine.
As I said, check your manual for the recommended compression of your engine.

Note: low-energy ignition system did not burn the fuel as well as high-energy ignition systems, creating carbon buildup. Engines with low energy ignition systems "35KV" needed a lower compression ratio. High-energy ignition systems "60KV" can use a higher compression Ratio. Less carbon buildup.


Stay safe and have fun.

Joe.

 

[bridgedog]

Not knowing what model engine you are working with doesn't help. I am not fond of sleeves in older H.D. cylinders. Don't know about anything newer than a shovelhead. You can buy new almost anything except maybe an old 80 inch flathead and they might even be available.

 

[Shimitup]

As I recall, flatheads ran somewhere in the 6 to 7 range with overheads rising to around 10 on the average for everyday drivers in the late 50's until the early 70's pollution engines brought em down to low to mid 8's. Exceptions for the 60's 10/1 average were the HP engines such as the Mopar hemis that ran around 12/1, GM and Ford also had high performance offerings between 11 and 13/1 at the most if I remember correctly. I'm afraid you have it backwards with air temps, cold air is denser requiring either lower compression ratios or higher octane to prevent detonation. I'm not sure diesels will ignite at 13 I think it takes at least 16 or 17. I know these days SI (spark ignition) engines are back up a bit with computer monitored knock sensors and exhaust recirculation, not sure how much, don't keep up with that any more.

Sorry that was off topic, sure I'd do it. Unless it's really horrible you shouldn't have to take off more than a few thou. Can you get thicker gaskets if you need the lost height? What about lapping? I've also taken care of a few such tasks with a file. Good luck.

 

[aspp]

As I recall, flatheads ran somewhere in the 6 to 7 range with overheads rising to around 10 for everyday drivers in the late 50's until the early 70's pollution engines brought em down to low to mid 8's. Exceptions were the HP engines such as the Mopar hemis that ran around 12/1 if I remember correctly. I'm afraid you have it backwards with air temps, cold air is denser requiring either lower compression ratios or higher octane to prevent detonation. I'm not sure diesels will ignite at 13 I think it takes at least 16 or 17.

10:1 is the lowest diesel compression I have worked on, a naturally aspirated Buda from the late 30s/early 40s. It was a small engine, about 8hp, for pumping water when there was no wind for the windmill. Crank start off a 3' flywheel, ran at 140-160rpm. Very neat little engine.

 

[Shimitup]

aspp, I've never heard of a diesel that ran that low, I bet it had a glow plug that stayed hot for an ignition surface. Sounds indeed like a very neat little engine. I love to hear thing like that run. I used to hear lots of these in my younger days I miss em.
Starting Old Arrow Engine - YouTube

 

[northeastconfederate]

Maybe I should have been more specific. I know all about the compression ratio and head to piston clearance. I have all that figured out. I can get whatever thickness head and bas gaskets in whatever combination I need to set the compression ratio where I want it (in this case 10.25:1). I was asking about machining such a critical surface on my old SB. The bike is an 02 Twinkie; far, FAR from stock. Cylinders are 4.125 inches. Lathe is a 1942 10L.

Since this turned into a compression ratio discussion rather than a machining discussion, I gather that no one thinks I shouldn't do it. Once again leaving aside the engine design issues; like I said, I have that all carefully calculated.

Yes, I could buy new cylinders, but they are profoundly expensive, for one thing, and would require another case boring operation, as the current case bore won't accommodate the aftermarket cylinders I would use if I went that route.

 

[m stoner]

I don't think it is a machine capabilty,I think its operator confidence in doing the job,$ is big deal mess it up and it's $ down the tube,but look at all the experience you'll get,did you look into those oil return tubes V Twin sells? My old 1924 SB 13 is more able to do it than me,LOL

 

[northeastconfederate]

You're right about that. Think I'm going to do it. I planned to go ahead and replace the cylinders but now that I found this it seems like I should be able to fix it. If so, it costs me a few gaskets. If not I replace cylinders as planned. In which case it costs whatever that costs (about $1100 by the time it's all done) plus the gaskets I waste by trying. Plus the time, bof course.

 

[m stoner]

You're right about that. Think I'm going to do it. I planned to go ahead and replace the cylinders but now that I found this it seems like I should be able to fix it. If so, it costs me a few gaskets. If not I replace cylinders as planned. In which case it costs whatever that costs (about $1100 by the time it's all done) plus the gaskets I waste by trying. Plus the time, bof course.

you have fixtures made up to mount those beasts,workin 8 '' off the head stock,got to have em true that's the hardest part,take your time and think things threw,5 or 6 beers out to do it.I'm going to make a fixture to mount Iron heads from the top end and use the steady rest to keep it in line,keep every think square should be ok,or make your own lap plate,every thing must be kept square.New ones are throw aways,unless you do your own work,My op,IRON HEADS FOREVER

 

[Greg Menke]

Upgrade to a crotch rocket instead?

sorry just joking.. that sounds like a nice project. Its always a bit scary when you're putting a fair $$$ on the line. Poor form for your prev guy to have made such a mess and then handed it back to you, do you know how he messed up the job- bad setup etc which might provide a clue for you?

Greg

 

[timvercoe]

Supporting the cylinder at the tail stock seems to me to maybe be an issue. I have a three jaw chuck mounted on a bearing that has a tapper for my tail stock. I also have tail stocks with little bearings on the jaws of a three jaw chuck that mount in the tail stock. Such a set up should stiffen the the right side of the set up sufficiently for the machining to eliminate the chatter you might get working a fairly large diameter that far from the chuck. If a photo is needed of these devices, PM me and I will try and post one here later.

Tim

 

[northeastconfederate]

I used to work at a hot rod bike shop and while I never did any cylinder boring myself, a 50's Monarch 17" did that along with a lot of other work there. I did run that machine quite a bit. That guy had a huge bullnose center for supporting the right end of cylinders. I don't have such a thing, and my tailstock has a little wear in it, which might make things a little hairy.

As for the machinist who did the work on it: I'm sure he was just in a hurry. It's a long story. Bottom line is, this project started in Las Vegas and I and my bike are now back in NJ. Yeah, it sucks, but at least I know what's wrong and what needs to happen to fix it.

I hadn't thought about supporting the right side of the cylinder. Overall length is under 5 inches but it seems like it does need support... Have to think on this some more... Maybe have to make a bullnose center.

 

[moonlight machine]

I used to work at a hot rod bike shop and while I never did any cylinder boring myself, a 50's Monarch 17" did that along with a lot of other work there. I did run that machine quite a bit. That guy had a huge bullnose center for supporting the right end of cylinders. I don't have such a thing, and my tailstock has a little wear in it, which might make things a little hairy.

As for the machinist who did the work on it: I'm sure he was just in a hurry. It's a long story. Bottom line is, this project started in Las Vegas and I and my bike are now back in NJ. Yeah, it sucks, but at least I know what's wrong and what needs to happen to fix it.

I hadn't thought about supporting the right side of the cylinder. Overall length is under 5 inches but it seems like it does need support... Have to think on this some more... Maybe have to make a bullnose center.

Just make a disc, 1/2" or whatever thick, cylinder diameter with a shoulder that is the sleeve od. Center drill it, slip it in the cyl. and use your live center. I do it all the time, must have 30 of those step discs.

 

[Greg Menke]

You could try a DIY "bullnose"; a while back I did part of a telescope mount consisting of a 2' piece of 8" black iron pipe, I made up a plug out of a few pieces of 2x4, turned for a mild driving fit into the pipe, then drilled for the tailstock live center. I used inside jaws on the headstock end. The op was putting in some threads one end and turning down a foot or so on the other, the wooden plug held up fine since it wasn't a heavy piece and operations were limited, skim cuts on the cylinder don't sound like a demanding op. If putting the center into the wood doesn't sound good you could always screw down a piece of steel plate onto the outside face then center-drill that.

 

[m stoner]

You could try a DIY "bullnose"; a while back I did part of a telescope mount consisting of a 2' piece of 8" black iron pipe, I made up a plug out of a few pieces of 2x4, turned for a mild driving fit into the pipe, then drilled for the tailstock live center. I used inside jaws on the headstock end. The op was putting in some threads one end and turning down a foot or so on the other, the wooden plug held up fine since it wasn't a heavy piece and operations were limited, skim cuts on the cylinder don't sound like a demanding op. If putting the center into the wood doesn't sound good you could always screw down a piece of steel plate onto the outside face then center-drill that.

very much difference in a 50 cent piece of pipe and an 1100.00 dollar set of jugs WOW

 

[Greg Menke]

very much difference in a 50 cent piece of pipe and an 1100.00 dollar set of jugs WOW

Shrug.. sure but what we're talking about is facing the gasket sealing surface on the end of a cylinder head- a hollow 5" long workpiece and only taking off a few thousanths. My ops were 8 tpi on one end of the pipe and removing 1/16" from about 10" of the other end- much more demanding of the tailstock support. Granted its probably preferable to make something out of plate- particularly if theres a 2nd cylinder to do- but sometimes you use what you have. Some reason why a wooden plug wouldn't work?