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+--- Thread: Tappets (/showthread.php?tid=3996)
RE: Tappets - JonE - 02-05-2021
So what IS the issue with "noise" please? - does it increase as the gap left at setting gets larger?
RE: Tappets - Howard Wright - 02-05-2021
Hi Jon
The thing is that you are dealing with subjective issues.
Setting the tappets to the narrowest possible gap possibly increases lift and therefore performance but by how much is debatable. However striving for this tightest gap leaves no room for margin. I certainly need a reasonable safety margin in everything I do on the car to make up for my meagre engineering skills
.Then the question of noise. What sounds like a “bag of chisels” to one is hardly discernible tinkling to others.
I’ll stick with 6’s and 7’s cos it gives me a reasonable margin of error and my poor hearing makes me think I have a quiet engine
.Cheers
Howard
RE: Tappets - JonE - 02-05-2021
I'm only asking in theory as my skills are meagre like you declare yours to be!! I just want to understand the issues - hence from your answer presuming that perhaps they get quieter as gap narrows...
RE: Tappets - Bob Culver - 02-05-2021
With no closing ramp as moderns, with increasing gap the closing impact is notably increased. With the weak springs of a standard engine hardly a threat to valve breakage or seat wear, although it is with other makes.
Even with just no measureable gap there is a strong load on the seat.
As far above, most modern valve steels have greter expansion than XB or earlier so some increase over the origianl is appropriate.
RE: Tappets - Nick Lettington - 02-05-2021
I went to grind a set of new valves into my block today but couldn't find the stick with the suction cups on. I have a pile of those really strong magnets so attached 3 to an old valve. When I tried to use this to spin the new ones... hmmm... stainless steel?
RE: Tappets - Bob Culver - 03-05-2021
Magnetic exh vaves are generally of XB steel or lesser. This was commonly used in many makes until late 50s. Burned valves and grinds were commonplace. The subsequent valves usually go the life of the car, 200,000 miles plus withut attention. The non magnetic valves, unless two piece, expand more when hot.
Extensive valve grinding is now frowned upon. If to correct the valve it unnecessarily wears the seat. Also forms a step on the valve. Seats can be tidied with a scrap valve, preferably refaced. If the valve has been refaced without chatter and with fine stone just a very slight lap then required. All been covered extensively but takes time to find.