Cylinder heads take a beating on Heinkel cars and scooters. I have a rogue’s gallery of broken, beaten, and melted (yes, melted) cylinder heads floating around. I don’t even know why I save them but that’s another story.
When I rebuilt my transmission a few weeks ago I had to re-use my head gasket. I knew I had another one in my parts supply, but I couldn’t locate it at 1:30 in the morning when I was on a tear rebuilding my engine. Reusing the head gasket was the only way I was going to get to the GouldMicrocar rally, so back on it went.
Last week I found the new head gasket so I decided to install it. First I had to determine if I had to remove the engine to complete the procedure. I asked three Heinkel Kabine experts; two told me I could, and one said no, so I went with the majority opinion and decided that to replace it with the engine in the car My fallback position would be to remove the engine if necessary.
I use the head gaskets with a crushable copper ring.
|Heinkel Head Gasket with Copper Ring|
It is not part of the standard gasket set you purchase from the clubs. I use these because I blew through a standard head gasket on my Heinkel Tourist scooter. When you tighten the head the copper ring gets crushed into place and provides an excellent seal.
Copper is soft, but Aluminum is softer, and the head is made of aluminum alloy. When I took off my head gasket I noticed my head had a semi-circular indentation from the gasket. When I reused the gasket it was already crushed, and when I torqued it down during the rebuild the only thing that could give was the aluminum in the head. Another expensive lesson to learn!
|Location of Indent on Heinkel Head|
I went to my local machine shop and had the head skimmed to remove the indentation. I was lucky- I have a great relationship with my machinist and he had it done in an hour on a Saturday morning! So, time to reassemble.
I’ve written before about finding Top Dead Center with a simple indicator. I received several complaints telling me this was a “flawed” approach since it didn’t account for the dwell at the top of the piston arc. So, while I had the head removed, I decided to use a runout dial indicator to precisely measure TDC. You can see my setup in the picture below.
|Finding Heinkel TDC With a Gauge|
The idea here is to turn the crank in the direction of the engine (clockwise) until you reach TDC and make a note of the reading with a mark on the flywheel. Then, turn the engine in the opposite direction until you reach the same dial measurement. Mark that on the case as well. Half the distance between the two marks is TDC. In my case the both line up in the same place, which was exactly where I had marked TDC before with my simple indicator. I repeated this several times to make sure I didn’t make an error.
Whenever you skim a head you need to make sure the clearance between the piston and the valves has not been compromised. The best way to do this is to do a dry fit without the gasket. The Heinkel head gasket is about 2mm thick. To get a good measurement I took some Play-doh modeling compound and laid it across the piston, then dry fit the head. I turned the fan by hand to run the engine through one revolution, then took the head off and examined the Play-doh. The thought here is that the valves will make an impression in the Play-doh. You can measure the clearance and determine if it is sufficient. In my case everything was fine, so I had the clearance to go ahead with the rebuild.
After setting the valve clearance I re-tested the compression to make sure everything was ok. I took it for a spin and it still seems a little pokey.
Did I have to remove the engine- No!
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