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Fri May 30, 2008 11:05 am

Hi Everyone,

Can anyone clarify the correct 25hp valves sizes for me, looking at the Karmann Konnection catalogue (UK parts supplier) it states the following, which indicates that the 25 and 30hp intakes are different sizes:-

Exhaust valve 25, 30hp 111 109 611A
Intake valve 25hp 111 109 601
Intake valve 30hp 111 109 601A

The 52 -57 VW workshop manual states the measurements for intake and exhaust valves are the same for 1131 engines, so I am more inclined to believe this (Valve head size diameter 27.9 - 28.1mm)

The 3 engines I have dimantled for parts all have different valve size combinations (all are 25hp heads) so I'm not sure if it was common practice to machine seats to take 30hp intakes ?

Any help would be much appreciated.

Thanks
Kev

Fri May 30, 2008 12:58 pm

Yes, the 25 hp intake and exhaust valves are the same size. The valves themselves are different but the size is the same.

Fri May 30, 2008 1:10 pm

oh ok, thanks Chris, so is it the face cut different or the valve head thicker ? Is it easy to tell one from the other looking at them ?

Thanks
Kev

Fri May 30, 2008 4:22 pm

The 25 hp intake valves have much less meat on them, compared to the exhausts. (Heat transfer isn't as much of a problem for the intakes as it is for the exhausts) The intake valves are a little more slender under their heads, possibly resulting in better flow of combustion gases.

Fri May 30, 2008 5:33 pm

Zwitterkafer wrote: The 25 hp intake valves have much less meat on them, compared to the exhausts. (Heat transfer isn't as much of a problem for the intakes as it is for the exhausts) The intake valves are a little more slender under their heads, possibly resulting in better flow of combustion gases.

that is correct. exhaust valves are more trumpet shaped and in the intakes have a very abrupt taper from stem to head.

The factory intakes also has a "S" on them to distinguish them.

Sat May 31, 2008 2:02 am

ok thanks for your replies I now know what I am looking at, one pair of heads I have does have the correct intakes on them with the S on the head but the ends of the stems are worn, can these be machined or will I need to replace them ? Of course I was already planning to replace the exhaust valves and these are easy to come by.

Thanks
Kev

Sat May 31, 2008 4:49 am

The very end of the stem where the lifter hits can be ground flat as long as it is not too bad. This is pretty common practice.

Sat May 31, 2008 11:00 am

thanks Chris.