Mode A Piston expander/ knurling tool to Buy

Don’t use these tools, it’s simply a bandaid tool. Like saw dust in the rear end.

Get a new piston or set of pistons, ball hone the cylinders and put it together. Pistons are relatively cheap, and you’ll be glad you fixed it the right way.
 
You will probably get an earful from people telling you how knurling is a bad, outdated, waste of time, why don't you do it the right way, etc. but it does work for a while. I have one of those expanders but I have NO idea where it is, sorry. Have you considered the old "skirt expanders" springy metal things that go up inside the piston? They show up online sometimes and also in boxes of old stuff.
 
Have you taken the engine apart yet? It could be a cracked or scored piston that would need replacement. If it has the original split skirts be sure the were all facing the correct way.
 
So, you are hearing noises from the engine some where. I have no idea how mechanically competent you are so I'll leave it at telling you about a motor that was in a car I imported from the US. The pistons had been knurled and bores parallel honed to recover from 0.006" wear in them. The gudgeons (wrist pins) had been very poorly redone with 0.005" O/S ones and new rings fitted. I wasn't happy with the noises emanating from under there so I decided to do something about it. The noises I was hearing came from the wrist pins. Are you sure yours is not the same? My advice would be to take it apart and carefully measure and check things before deciding what to do.
BTW, the bottom end was loose too and I haven't been able to get it right yet.
 
Jack Shaft said:
a set of pistons is 95 bucks.. look at it this way, why go through all the labor of pulling the head and oil pan, buy a gasket set, and adjust all your rod bearings to 'patch' the engine? If the main and rod bearings are good pull the pistons, hone the bores, lap the valves and adjust the bearings..and have a good old fashioned overhauled engine you can rely on..


https://www.snydersantiqueauto.com/...040_PISTONS--040?fromCategory=SearchByKeyword
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Problem is, if he is, in fact experiencing piston slap, doing as you suggest will do nothing to solve the problem he is experiencing. Piston slap is from too much clearance in the bore. Unless by "Honing" you mean to hone it out to the next size rather than honing to restore the cross hatch, Honing and putting new pistons of the same size will do nothing to solve the problem because the problem is not with the pistons Per se, but with the cylinders. The cylinders will have to be bored to the next piston size. When I was faced with a similar issue, I did a lot of research into knurling. I read a lot of negative opinions on it pretty much exclusively from people that don't fully understand it. After finding several sources from people that no only fully understand it but have done it, I arrived at the conclusion that, not only is it acceptable in the right situation, it has some benefits and I would not hesitate to do it if i found myself in a situation that warranted it. In my particular case, I had wicked cylinder taper (.009") and therefore chose to go to the next size piston and hone out the taper and bring the cylinders to the next size. That was a big job. If the cylinders were relatively straight, I would MUCH rather knurl the pistons.
 
Yeah, my A ening has a ton of piston slop and smokes pretty good at idle but I have a stock bore B engine under bench waiting so meh. :)
 
Licensed to kill said:
Problem is, if he is, in fact experiencing piston slap, doing as you suggest will do nothing to solve the problem he is experiencing. Piston slap is from too much clearance in the bore. Unless by "Honing" you mean to hone it out to the next size rather than honing to restore the cross hatch, Honing and putting new pistons of the same size will do nothing to solve the problem because the problem is not with the pistons Per se, but with the cylinders. The cylinders will have to be bored to the next piston size. When I was faced with a similar issue, I did a lot of research into knurling. I read a lot of negative opinions on it pretty much exclusively from people that don't fully understand it. After finding several sources from people that no only fully understand it but have done it, I arrived at the conclusion that, not only is it acceptable in the right situation, it has some benefits and I would not hesitate to do it if i found myself in a situation that warranted it. In my particular case, I had wicked cylinder taper (.009") and therefore chose to go to the next size piston and hone out the taper and bring the cylinders to the next size. That was a big job. If the cylinders were relatively straight, I would MUCH rather knurl the pistons.
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I actually, fully understand knurling, but you personally don’t know me, so I’ll assume you are not talking to me directly. Knurling is outdated technology from the time when new pistons were of poor quality when compared to oem pistons. Today’s new pistons for model a’s are of superior quality for 95% of the users out there. For the same amount of effort, time, and cost, why wouldn’t you go with new rings and pistons?

Piston slap is the result of one or both things, either the piston collapsed, or the cylinder is worn enough to taper, allowing the slap. The real solution is new pistons, or bore/hone to the next size AND new pistons.

Knurling is a bandaid. It’s one best applied by the old total seal (or others) knurling machines. Far more rare and expensive than a new set of pistons.
 
Thanks for the input. I still would purchase the tool and perform the expansion as a learning tool for my club seminars. Yes, the purchase of a set of pistons is not expensive and the cost is not at issue The purpose will be a learning tool.
 
I own a Perfect Circle Nurlizer machine. I collected it as strictly a conversation piece and in case some pistons for which there not have been a reasonably priced replacement. Nurlizing was even suggested for new pistons as it tightened up the clearance and provided a place for lubricating oil to slide in the bores. As for all the good advice these previous gentleman have given, they are right on the money. Don't judge or predict what the real problem may be. Loose wrist pins, bent rods, ill fitting pistons, worn rings. A set of new pistons with fitted wrist pins and new rings along with proper fitting in the cylinders, a rebore may be needed, and you will be money ahead.
 
Hitman said:
I actually, fully understand knurling, but you personally don’t know me, so I’ll assume you are not talking to me directly. Knurling is outdated technology from the time when new pistons were of poor quality when compared to oem pistons. Today’s new pistons for model a’s are of superior quality for 95% of the users out there. For the same amount of effort, time, and cost, why wouldn’t you go with new rings and pistons?

Piston slap is the result of one or both things, either the piston collapsed, or the cylinder is worn enough to taper, allowing the slap. The real solution is new pistons, or bore/hone to the next size AND new pistons.

Knurling is a bandaid. It’s one best applied by the old total seal (or others) knurling machines. Far more rare and expensive than a new set of pistons.
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You are correct, I was not talking directly to you or anyone else, just in general from what I found during my earlier research. I agree with everything you said with one exception and that is that there is a 3rd cause for piston slap and that is a bore that was bored with too much clearance. In this case, when the bore is too big but not tapped, knurling is, IMO the preferred solution over reboring to the next size and getting new pistons. In my particular case, my pistons had quite a bit of slop and there was zero ridge at the top of the cylinders so I assumed that the bores were just bored too much by whoever built it last in which case knurling would have been the answer. However, once I mic'ed the bores and found the taper I was only left with two options. Bore them to the next size or sleeve the cylinders and start from stock. I chose to hone the cylinders to the next size myself.
 
KR500 said:
I own a Perfect Circle Nurlizer machine. I collected it as strictly a conversation piece and in case some pistons for which there not have been a reasonably priced replacement. Nurlizing was even suggested for new pistons as it tightened up the clearance and provided a place for lubricating oil to slide in the bores. As for all the good advice these previous gentleman have given, they are right on the money. Don't judge or predict what the real problem may be. Loose wrist pins, bent rods, ill fitting pistons, worn rings. A set of new pistons with fitted wrist pins and new rings along with proper fitting in the cylinders, a rebore may be needed, and you will be money ahead.
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Interestingly, when I got my new pistons, in the instructions it suggested that if the piston/wall clearance was over spec to knurl the pistons to achieve the proper clearance. During my research, among those that supported the use of knurling (in the right circumstance) at least one that I recall said that "back in the day" he used to knurl new pistons as a matter of practice on his race engines for the added lubrication and piston cooling achieved by the knurling.
 
Licensed to kill said:
Interestingly, when I got my new pistons, in the instructions it suggested that if the piston/wall clearance was over spec to knurl the pistons to achieve the proper clearance. During my research, among those that supported the use of knurling (in the right circumstance) at least one that I recall said that "back in the day" he used to knurl new pistons as a matter of practice on his race engines for the added lubrication and piston cooling achieved by the knurling.
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You are right, Knurling is a very good repair when done correctly.

Bill
 
30blindback said:
Thanks for the input. I still would purchase the tool and perform the expansion as a learning tool for my club seminars. Yes, the purchase of a set of pistons is not expensive and the cost is not at issue The purpose will be a learning tool.
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Any chance your pistons are actually old split-skirt pistons? If so, there were specially designed "expanders" for correcting slap. They were called 'Piston Expanders'. :D Easy to install and will work as good as knurling.
 
The alternative to knurling is Koetherizing, wherein the piston is squeezed through the gudgeon bores by a bolt and thrust bearings into a more cammed shape on the thrust faces. While under this compression it is shot peened inside, relieving the alloy stresses so it retains part of the squeezed in expansion when released.
There was an article on this forum about a portable koetheriser in a truck by Old Motor a while ago.
I just 4-stone honed an engine to straighten worn bores and bought new Omega solid skirt pistons which I resized on my koetherizer by 0.0095 for the worst bore. The others were around 0.005 inch. That engine now runs nicely with no piston slap.
Obviously not as good as a rebore, but fun to do and should last another 50000 miles at least, going on past history with older repairs by the firm which donated the machine to me.
How many koetherizers are left in the USA I wonder? I think I have the only one of 2 that were sent out to NZ.
The engine was a 2.5 litre Riley, not a Model A. Compression pressures are now all 167 psi. 8.8 to 1 pistons used
SAJ in NZ
 
I was going to mention shot blasting but didn't because the topic was knurling. I think the shot blasting is a better method but knurling gets it done with less equipment.
 
Curious. To those that did not like the idea of knurling to expand a piston, could share your reasons please??. While my current opinion is that it's a good thing (in the right circumstances) that opinion is subject to change pending compelling arguments to the contrary.
 
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