[T2] Bus running too hot.

[Merrill Lawson]

I have a VW bus that's running hot, 250-255 on the hwy, when only driving about 55-60 mph max for about 15-20 min.  It's a 1976 VW bus with fuel injection.  I had a VW mechanic recently install rebuilt VW cylinder heads & valves (96mm piston & cylinder), new oil cooler and all the tins are in place.  New engine seal, too.  I thought the new heads, cylinders and oil cooler would help the oil temps but they have not.  The mechanic feels like he has tested everything that he could think of but does not have a dyno so cannot test fuel mix at highway speeds and suspects there may be an issue with either the fuel injectors (which he feels is unlikely because at idol they seem fine) or the air flow meter on the fuel injection system.

I suggested he test the distributor after reading that a bad vacuum can will cause an engine to run hot.  Just as a test he swapped my Bosch SVDA distributor with a Bosch 009 and it's running about 10-20 degrees cooler.  Do you have any idea why when swapping the Bosch SVDA distributor for a Bosch 009 it runs 10-20 degrees cooler?  Do you think if I replaced my Bosch SVDA distributor with a new one, part #043905205, it would do the same thing or better than the 009 and run cooler?

The advance on my SVDA distributor was working when I tested it with a strobe (it returned back to 7.5 after pulling the throttle) and manually testing by sucking on the hose; the diaphragm and springs seem to be working.

He’s tested for vacuum leaks, too and says I don't have any.

He also swapped the oil temp gauge and sensor with a new ones and readings are consistent.

Any input or feedback as to why one distributor would run cooler than the other and / or any ideas as to how to get my oil temps down would be greatly appreciated.

Thanks!

Merrill