ET: Engine (Twin) Valve Liners, Recommended Clearance

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Sebastian Huber

Well Known and Active Forum User
VOC Member
Hello Experts,

my carbide reamer makes 9,52 (3/8") and 7,94 what means 0,07 (2 3/4 thou) clearance on both ends for inlet and exhaust.
Has somebody experiences with samler clearance?

Think about for to reduce oil passing on ex. side. Even with shaft sealing (rotorcaps) after 10 tousand miles they are ineffectively hard.

Many thanks in advance!
Sebastian
the Bavarian
 
Vincent Brake

Vincent Brake

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i do about 0,02 for inlet and 0,03 for outlet, on either alu bronze or Ampco 45 and a long guide about 32 mm with a knife edge on top, first lapp in the alu hole (guided by the top guide) than measure Machine up guides at about 0,03-4 mm interf fit, than lapp the guide to sise.
 
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Sebastian Huber

Well Known and Active Forum User
VOC Member
Vincent Brake said:
i do about 0,02 for inlet and 0,03 for outlet, on either alu bronze or Ampco 45 and a long guide about 32 mm with a knife edge on top, first lapp in the alu hole (guided by the top guide) than measure Machine up guides at about 0,03-4 mm interf fit, than lapp the guide to sise.
Click to expand...

Hi Vincent Brake,
Thanks a lot for prompt response.
Expect you use standard valves as sold by Spare Part Company too, the only source I know. The shafts are 9.45/7.87mm. Different material for inlet and exhaust.

Did I catch it right, here you recommend liner dia 9.48 and 7.89 with tolerances of plus some microns?
Does this really work without seizing?

Thought about Amco (regularly used in our Plast. Injection Dept) and knife edge without shaftsealing.
Followed so far an well experienced old guy, the co-boss of the company, they do all the work I can´t, f.ex. drilling and finishing cylinder liners a.s.o.
He always tolled me "never do it smaller as 0,08mm. One time we did it with only 0,06 on JAP-Speesway racers and they all seized".

Kindly regards,
Sebastian
 
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clevtrev

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The valves were designed to fit a 3/8" diameter hole, and the clearance is determined by the valve stem diameter. Measure them and you will find the exhaust to be smaller in diameter than the Inlet.
 
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Sebastian Huber

Well Known and Active Forum User
VOC Member
Yes, that's the second point. I weakened it because of to much carbon deposit on front spark.
Will follow your advice on clearance when new liners will be done next week.
Will send reamer back to griding shop for to reduce dia. together with ordering guide shaft for my Hunger Device. Standard shaft is fixed with collet only in lower liner. It works but had once some problems on perfect alignment. For to avoid this in the future I`ll use lower and upper liner bush.

Have the chance to choose between HOVADUR B10 (= AMPCO 18) or HOVADUR K 220 (AMPCOLOY 940). Think I`ll take the first one (HB 180 -220, min. 620 N/mm²) for it's very close to AMPCO 45 you recommended. We have good experiences when used on sliders in injection tools.

Where to buy Neal Videan Tulfided valves and could you please forward me ordering code?

Thanks again for your help,
Sebastian
 
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Sebastian Huber

Well Known and Active Forum User
VOC Member
Thanks for your help, Bruce. See how often you give help and advices and this is what makes the Forum so great.
This morning I was still wondering whether to improve valve liners or not. Now I fell much more safe in doing it.

Cheers ,
Sebastian
 
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