Pushrod tubes

[adz25]

Can anyone offer advice on my pushrod tube lengths please. I bought a bitsa which was loosely assembled but came rebored with new internals. Its a 1953 model 18 with a flat top hepolite poston. I have just purchased new short pushrod tubes ready to assemble but there is an 8mm gap between the head and the barrel and a dare not try and pull the head down at that as Im pretty sure the seals will not compress that much.

[adz25]

I have the o ring at the base of the pushrod tube pushed over the valve guide, sitting in the radius. In the head i have the plain washer, rubber sealing tube and conical washer. I will try to add a picture. The piston at tdc sits just flush with the barrel lip.

Many thanks

Adam

[adz25]

Pictures uploaded to the parts postwar singles section as i dont have an image host.

Many thanks

Adam

[Rob Harknett]

I have answered on your pic. Looks like you have 7 15/16" tubes but need 7 9/16" You have not told us the length you have. It does look like you have a 3/8" gap

[adz25]

Rob,

Thanks for the reply. I have 7 9/16 inch pushrod tubes ( the shorter ones). This is whats confusing me.

Regards

Adam

[adz25]

Have added a picture of the piston at tdc, does it look right?

I removed all old washers and rubbers from the head then media blasted it, the new washers i installed are visible from the top side of the head so am sure theres nothing else in there.

Many thanks

Adam

[Rob Harknett]

The head looks odd to me for 53 fins seem to curl round the push rod tubes. show a pic of the head for all to see.
I assume you did actually measure the tubes to make sure they are not 7 15/16

[adz25]

Rob,

Picture of the head added.

Yes removed and remeasured, end to end 7 9/16". I guess this is one of the many problems when building from boxes.

Should this engine have a compression plate?

Regards

Adam

[Rob Harknett]

A compression plate would not make up the gap. It was the fins the push rod tube side of the head that looked odd to me.

[clive]

I have the o ring at the base of the pushrod tube pushed over the valve guide, sitting in the radius. In the head i have the plain washer, rubber sealing tube and conical washer. I will try to add a picture. The piston at tdc sits just flush with the barrel lip.

Many thanks

Adam

Adam sounds like you have them in the correct order. If there really were no additional plain washers in the head (I have seen at two when stripping one engine, fitted when a decompression plate is used. ) then I think the problem is that the pushrod tube is not far enough into the head. They should project beyond the top plain washer. Original pushrod tubes were rolled over fractionally at the top so easing their movement through the washer. later replacement pushrod tubes do not have this feature and can get jammed under the washer. I suggest you disassemble and grease the inside and outside of the rubber, make sure the conical washer copies the angle on the pushrod tube. Then press the whole lot into the head and see if you can get the end of the tube to pass through the washer. You should then have less gap.