Magnadyne Flat 6

[Lucas9214]

Hello, I am in the process of rebuilding a Mack model EQSW with a flat head 6 cylinder Magnadyne engine. When I bought it they said it was a 52 but I'm not convinced of that, I believe it is a 49. It had a seized engine so I had to beat the pistons out and cannot find replacements for them. This is my first post and I'm far from a professional mechanic but any help would be appreciated. 

 

Edited February 10, 2022 by Lucas9214

[67RModel]

I just realized that the Detroit Pistons basketball team were named as such because they were started by Fred Zollner, who started Zollner Corporation as an OEM piston supplier to just about everyone (including the pistons you have there). If you google Zollner pistons all you get is basketball information.......Sorry I'm no help but somebody will be along here with useful information....

[Vladislav]

Looking your pics I dont see a reason you need new pistons. Cylinders relining is too probably on the way and suitable compression rings chosen by the size. When you recondition the liners you just bore new ones to get required gap to the existing pistons. There may be another way of ordering new custom made pistons already oversized to rebore the block. If you find yourself lucky finding a NOS set of oversized pistons and rings for them that's the most straight and correct way.

Those flathead Mack engines were of multiple models and of different displacements. Yours is probably EN354 of 354 ci. But this point definitely needs determination since you should start from it in your search.

Vlad

[Lucas9214]

15 hours ago, Vladislav said:

Looking your pics I dont see a reason you need new pistons. Cylinders relining is too probably on the way and suitable compression rings chosen by the size. When you recondition the liners you just bore new ones to get required gap to the existing pistons. There may be another way of ordering new custom made pistons already oversized to rebore the block. If you find yourself lucky finding a NOS set of oversized pistons and rings for them that's the most straight and correct way.

Those flathead Mack engines were of multiple models and of different displacements. Yours is probably EN354 of 354 ci. But this point definitely needs determination since you should start from it in your search.

Vlad

Thank you for your response, unfortunately that was one of the better pistons that I took out. the skirt on one broke off and the guts on most of the rest are pretty well deformed. I'm afraid that if the pistons aren't properly balanced it could cause a problem at high rpm. I have thought about resizing the cylinders but think it would be best to have a machine shop do that so I was hoping to get lucky finding the original pistons.

[67RModel]

I think Zollner became or was bought by Mahle of Germany. If you go to a high quality machine shop that works on heavy duty engines they may have some old catalogs or may be able to find a catalog cross for the old pistons. All the machinists that worked on and overhauled those engines back in the 60s and 70s are probably long gone but there is somebody somewhere can probably find an modern replacement?

[Vladislav]

I went through such a story in the past. Obtained good result but the amount of the efforts involved doesn't seem very pleasurant now.

The bores in the block were of a standard size and the pistons went poor as in your case. I was lucky purchasing a set of NOS pistons but they were STD either. The block had dry liners and I could remove them in a press. Was going to use pre-cast tubings for fabrication of new liners but got no luck due to the size of my liners. I could only get shorter or wider tubings. Ended up purchasing custom cast tubes with further machining, pressing into the place and reboring-honing. All was described here:

As you can see it wasn't the easiest way to resolve the problem. Now having that experience I would try another option. There are shops which machine new pistons of forged aluminium, mostly for race cars. Their performances are much higher than old truck engines had and tolerances too. So seems I better ordered 6 new pistons milled of solid alu and made them already oversized. Than bored the original liners in the block and found compression rings to fit the size.

Edited February 13, 2022 by Vladislav

[mrsmackpaul]

Vlad is right about getting custom pistons made

This is what I would do, get it resleeved and custom pistons made

Then get the whole shooting matched balanced and assembled as a short block

It's gunna cost a bit but it will out last all of us and well worth it in the end 

 

Paul