Advice needed on L-head Tecumseh engine Durability.

[Hreagle]

Hey Guys, I'm looking for some advice on a Tecumseh 5.5 HP L head engine. The Engine in question is new and has an all aluminum cylinder wall. I would like to port out this engine, shave the head, and install a reground Tim Isky cam. My question is, how durable is an Aluminum cylinder wall engine? I don't want to waste my time and efforts to build up this engine if the cylinder wall is going to get trashed quickly. What do you experienced engine builders think is the chance this engine is going to hold up well to adding some HP to it? I've seen a number of old engines with trashed Aluminum cylinder walls, but none of them have been owned by me since they were new so I have no Idea how they were treated and if they had regular oil changes done to them.

The Snow King engine I have has lighting coils on it, which I need, and those parts are close to impossible to find for the older Steel sleeved HS50 engines. I would actually be willing to fit a steel sleeve into my newer LH195 SP block, but looking over this engine it doesn't appear to have enough cylinder wall material to over bore it and fit one in. I'd also be willing to use an older steel sleeved HS50 block I have if I could find some lighting coils to fit it.

So do you think an Aluminum cylinder wall block will to be durable enough or do you think I should look elsewhere? Is it possible that some other model Snow King 5.5 HP engine has a steel sleeve? Thanks!

Eagle

 

[ATKRIDER]

The aluminum bore with proper maintenance holds up just fine. IF you put a steel sleeve in it than you will need to find an unplated piston for it. Good Luck with that. Also all of the new replacement Tecumseh ring sets come with an expander that is designed to go under the second compression ring, on certain engines. Don't use it on an aluminum bore HS series engine.
Also if you decide to port it-don't get too crazy on the insides of the ports where the intake and exhaust almost come together. There is very little material there especially where the step is in the area that it transitions into the bowl area. Removing too much there and you will break through the port wall instantly creating about 2 pounds of scrap- :doah:

 

[Hreagle]

Thanks ATK, so I assume you've had experience doing Mods to an Aluminum bore engine and got to see how well it holds up? I was also considering the need for a different piston but after checking the part numbers for an older steel sleeved HS50 VS my LH195SP I find they're the same part number. I thought that was odd because as far as I knew an Aluminum bore engine required an iron plated piston like was in the Chevy Vega engine. Could it be that the HS50 had different sub-models some with Iron bore and some Aluminum? Does anyone know if any of the LH195 series blocks used a sleeve and some not?

 

[rmm727]

You would need a chrome piston for aluminum bore. Iron lined are unplated but can use the chrome as well. So no need for a different piston if you decided to get a sleeve installed. As for durability, think of the 5hp Briggs. Before the Raptor came along, most of them used in karting were kool bores.

 

[Hreagle]

Rmm, I have this engine apart and as far as I can see the piston just looks like a standard Aluminum one. I've never seen a chrome plated Piston, but I have seen some Aluminum bore Motorcycle cylinders that were chrome plated. Some of the older 2 cycle Motorcycle engines were made like that, not sure if they still make them that way. The Bridgestone 175 engines in the 60's were that way. Do these chrome plated Pistons you've seen look like shiny chrome or are they dull finished? It puzzles me that an iron bore HS50 and the aluminum bore LH195 series engines list the same part number piston. I always was taught that aluminum against aluminum would chew itself up.

The Chevy Vega engines were all aluminum bore but they were acid honed after sizing to etch the aluminum away, leaving silicon on the surface. The pistons were plated with iron as the top layer so they were compatible. The only issue those engines had was if you overheated it, the silicon would flake off and then the piston skirts dug into the bore and ruined the engine. I replaced a lot of Vega blocks back in the 70's when I worked for Chevy.

 

[125ccCrazy]

Rmm, I have this engine apart and as far as I can see the piston just looks like a standard Aluminum one. I've never seen a chrome plated Piston,

they are not chrome as you would normally think of chrome...they don't have a mirror finish... they have to have the coating to keep the piston from galling to the bore.. as mentioned above you can run a chrome piston in a steel bore but not a non-coated piston in a kool bore, well not for long anyways..
below are Briggs pistons, the one on the left is Non-chrome and the one right is a chrome... by looks you would think they would the the other way around..