Piston to Valve clearance?

[mrniceguy351]

Hello everyone,

Just about ready to start putting the top end of the motor back together and set the cam timing up. I've noticed in all that I've read about these engines there is almost no mention of piston to Valve clearance.

I've had the heads shaved just enough to get a clean sealing surface.

Is it possible to get this wrong enough to have valves hitting pistons?

I was thinking of getting the number one piston to TDC with both valves open equally, then gently turning the cam back and forth till one of the valves touches the piston, just as an indication of how close they are at TDC.

Or I could assemble the whole lot with lumps of plasticine on top of the pistons, set the cams, turn it over a few times then pull it all apart and check the plasticine thickness. And hope I didn't give myself a false reading whilst setting the cams up.

Thoughts?

Edited by mrniceguy351 on Sunday 10th September 01:51

[NicBowman]

Hi. I enjoying using an endoscope for visualisation. They are quite cheap and plenty small enough to go in the plug hole. Mine has a side camera as well as front which is really useful. Once you see it turns over with no contact. Put a sausage of bluetack in the valve cutouts and turn it over by hand, then dismantle and measure the thickness. Only needs to be a 3mm diameter sausage. Not much.

I ended up with 2.5mm clearance.

If you haven’t changed the spec much it should still be ok.

Nic

[mrniceguy351]

I like the idea of an endoscope. And I have one. Thankyou.

[ukkid35]

NicBowman said:

I ended up with 2.5mm clearance.

If you haven’t changed the spec much it should still be ok.

Nic

That is really useful info

The risk of piston valve contact when installing the cam chain makes my blood run cold

That's why I've been using this method for several years rather than the one in the WSM

https://www.pistonheads.com/gassing/topic.asp?h=0&...

[Mr Cerbera]

Hi Simon,

you could always ask Al Melling on his facebook page "Melling's Musings".
(Sorry I don`'t have the Link but, as you know, I've been banned)

I think that he still has the original drawings (but you'd better be specific about what size and year of motor it is ).

Hope your weather is good

PJ

[mrniceguy351]

Mr Cerbera said:

Hi Simon,

you could always ask Al Melling on his facebook page "Melling's Musings".
(Sorry I don`'t have the Link but, as you know, I've been banned)

I think that he still has the original drawings (but you'd better be specific about what size and year of motor it is ).

Hope your weather is good

PJ

Yeah he has spoken about it in the past, I will have another look.

Your book is going to be published soon BTW haha.

The weather is awful atm!

[Mr Cerbera]

mrniceguy351 said:

Your book is going to be published soon BTW haha.

That is the funniest joke I've heard this year.

I've challenged him on FaceBook and he has come out with sucha total load of lies that the only way I can get some piece is via legislation and I don't have the money for that so, as Mrs. Cerbera has advised me, I've just gotta let it all go (like so many of his unfortunate partners in the past, had to).

Another one chalked up for "Prize Idiot" again

[mrniceguy351]

Mr Cerbera said:

That is the funniest joke I've heard this year.

I've challenged him on FaceBook and he has come out with sucha total load of lies that the only way I can get some piece is via legislation and I don't have the money for that so, as Mrs. Cerbera has advised me, I've just gotta let it all go (like so many of his unfortunate partners in the past, had to).

Another one chalked up for "Prize Idiot" again

Yeah I don't think there will be enough meat on the bone to be worth fighting over. Don't get me wrong, I'd love to see it do well, but it's a very niche audience I think.