912 valve train question

[S hammer]

Have an issue with the valve train. Recently rebuilt a couple thousand miles ago. When I go to adjust the valves, all is good till I get to #4. Adjustment is difficult due to the adjustment screw is hard to turn, in & out!
Can anyone help me out on this as it seems to not be too difficult! Or would there be more machining considering the threads for adjustment are binding. Also how to re align the valve train. If a phone conversation would be of benefit, please let me know.

Thank you

[touringmandan]

I have encountered adjusting screws that were "stretched" when someone over-torqued the locking nut. The non-threaded section in the middle can stretch. This distorts the thread pitch and causes the adjuster screw to bind. I like to replace all of the adjuster screws on a fresh rebuild.
Hope this helps.

[S hammer]

Thank you for this information. Sounds very logical.

[S hammer]

I replaced the offending lock nut. The old nut was galled & the new nut went on by hand! Problem solved! Guess the adjuster is a harder steel than the lock nut. Makes sense to me.

[jaybrame7]

Anyone knows what is the unit on the left with the cooling fins on it connected to a metal pipe?
Thanks

[peter leinberge]

SMOG PUMP / TIRE INFLATOR
(but only works if you can find the uber-rare german produced reverse thread valve)

[wkrtsm]

That's a good one (SMOG PUMP), but wouldn't doubt it. I'm in Texas, and would take that off and throw it away in a minute unless it boosts performance (doubt it).

[John2244]

1968 smog pump. Don't throw it away, somewhat rare and valuable. But use it as a show piece only not as an active unit. I have only seen three on a 1968 in the last 5 years.

[Prsh356]

It was a must back in the day when guys with 68's had to smog their 911 + 912's .

[No Sweat]

Originally Posted by Prsh356

It was a must back in the day when guys with 68's had to smog their 911 + 912's .

Was factory installed to meet emissions, Hard to find as the were used in race motors as a vacuum pump to get a lower blow by.

[Robert Terrill]

Almost impossible to find. Required for emissions testing in California. It was standard on 1968 912 Porsche's in California. I have a 1968 912 engine advertised on Craigslist - Las Vegas that has the double pulleys, but not the smog pump. It supplies air injection into the intake fuel stream.

[Peter Graham]

Originally Posted by Robert Terrill

It supplies air injection into the intake fuel stream.

Actually it injects air into the exhaust stream to help burn exhausted fuel. It raised the head temperature to the point where USA MY68 suffered more cracks than other USA model years: cracks usually start at the spark plug boss and emanate towards/to intake seat. In any state outside of California in the USA, this equipment was often removed and discarded with the cylinder head air injection holes plugged. I believe the MY69 heads retained the injection port casting but were not drilled (other mods to meet USA emission standards to include Teflon-coated intake manifolds). The double pulley is desirable due to increase mass and subsequent crankshaft dampening. The pump-modified engine mount is often found cracked/welded...

Typical MY68 head crack:


Plugged injection ports (circled in red; #1 obscured by tape/generator stand):


Typical cracked MY68 motor mount:


'Full' repair with 'blanking plate':


Peter