Valve clearances on P1800S

[paulcbr]

My manual tells me that i should set my valve clearances to 0.043 in on a cold engine
My car is a 1970 P1800s with a B20a engine
The car is very noisey - "tappety" with these settings
I've looked at forums & similar engines seem to have a setting much narrower
ie. usually 0.02 in to 0.022

Any advice please ?

[Derek UK]

Unless some changes have been made, no 1800 came with an "A" series engine. A means single carb with an A cam. 1800S with a B20 should have a B20 B with a C cam. If that's the case then the valve clearances should be 0.020"-0.22" for both inlet an exhaust, set with cold or warm engine. The B20A is 0.016-0.018" if you do indeed have a B20A.

You are getting confused by the numbers in the manual. The numbers you quote are for setting up the cam timing, something that an engine builder may need to do. For clearances look under "Valves".
By modern standards none of these engines are "quiet". In fact quietness may mean that the exhaust valve clearances are being reduced by valve seat recession due to having no lead in the petrol. If checking the valve clearances it's a good idea to measure them all first before you start. Note the measurements and keep it for the next time you do it. That way you can catch any that are suffering.

[swedishandgerman]

I often contemplate this because a wider gap provides an improved way of opening and closing the valves more instantly which gives better sealing on the compression stroke. On the other hand, a small gap allows the cam follower to "follow" the cam profile better and the exhaust valve is open for longer allowing more time for the exhaust gases to get out.

All said, the recommended gaps in the book are calculated on the ramp of the cam to achieve the optimum opening and closing of the valves as well as time duration. So for an a-cam it's the narrower gap because the cam lobes aren't as tall, then the valves are open long enough to give proper inlet and outlet of gases. For a b-cam it's the wide gap (taller cam lobes). For a fuel injection cam, it's the narrow gap - I guess so that the valves are open for longer. If you accidentally use 0.043 setting you've found somewhere, it just won't run properly.

As such, you need to find out what cam is in there, rather than what engine you have. IE: If it's a B20A fitted with a b-cam, it's the wide settings. As above, a 1970 1800S shouldn't have a B20A!

[CLIVERALLY]

In over 40 years I have always errd on having a noisy tappet rather than a silent but deadly one

[Faust]

Originally Posted by CLIVERALLY

In over 40 years I have always errd on having a noisy tappet rather than a silent but deadly one

As a wise man once said: a slappy tappet is a happy tappet.