1955 350 valve guide protrusion.

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1955 350 valve guide protrusion.

Postby laxy » Sun May 12, 2019 3:41 pm

Just doing top end overhaul on my 16ms 1955. Ive noticed circlip fitted to both guides rather than just the exhaust which was introduced for 55. Thats not really a problem cos with circlips fitted the guide cant move downwards and hold the valve off its seat. What is puzzling me is that in F Neils manual the protrusion for inlet guide is nine sixteenths . Mine is eight sixteenth and valve seat and valve face are both in good condition. However the exhaust protrusion should be five eights and mine is four eights. Valve seat looks very black and burnt as does the valve face. It might lap in ok then i can refit valves and springs then check by petrol in upturned head method to see if its petrol tight seal. Would i be right in thinking replacement valve guides have different protrusions than orginals

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Re: 1955 350 valve guide protrusion.

Postby SPRIDDLER » Sun May 12, 2019 6:25 pm

I don't know about protrusions varying from original to pattern guides but IMHO an eighth of an inch difference is neither here nor there.
The exhaust throat and back of the valve and stem won't be as clean as the inlet as it's subject to burnt/burning gas when open whereas the inlet valve seat is only exposed to the clean fresh cooling petrol/air mix. However, the sealing ring of the seat and valve should be reasonably clean/shiny unless it has been seating badly.
Did you decide to overhaul the head for any particular reason?
I poke badgers with spoons.

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Re: 1955 350 valve guide protrusion.

Postby aobp11 » Sun May 12, 2019 7:28 pm

Keith, you might be referring to Fig. 2 in Neill "1948-1957 5th edition". But according to the Technical Data overview the protusion for the years 1954-58 is 1/2" for both inlet and outlet.
I am not sure whether the words protrusion and projection mean different things. The Instruction Manual lists Projection as 1/2" for both guides. Do you mean the piston side or the rocker box side?
Albert

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Re: 1955 350 valve guide protrusion.

Postby laxy » Fri May 17, 2019 2:06 pm

Thanks sprid and albert for your replies. The reason for top end overhaul was the engine not been apart in the ten years since i rebuilt it. Noticed a few small leaks so decided a good dose of looking at was in order .after a decoke and lapping valves in im less than happy with the condition of the exhast seat in particilar. I dont know wether its as a result of ethanol in the petrol or several years of unleaded petrol. Any way i rangTandL this morning and as a result of that conversation ive sent the head to them for inspection and advice. Only problem i had was at the post office when i told them what was in the parcel they refused to accept it. Apparently anthing thats been in contact EVER with petrol oil etc they wont accept. Solved the problem by going to to another post office and telling them it was a wheel hub

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Re: 1955 350 valve guide protrusion.

Postby 56G80S » Sat May 18, 2019 1:20 pm

I took a similar approach when sending a cylinder head to T&L.

Johnny B

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