1600 dual port 71-74

[dods1600]

Between 71 and 74 were there any changes made to the actual block of the 1600 dual port?
I an engine in the beetle now that is a 74 from block to heads, and then everything else on it is from the 71 engine.... I have had this engine set up like this for about 2 years and the entire time it has been a struggle to tune and get it through aircare. Is there any difference that would cause this?

Thanks

Tristan

[egspot]

I am no expert but, see if you can get more information:

What carb, rebuilt or new?

Stock heads, and valves are adjusted?

What distributor?

muffler?

Any leaks on the fuel system?

Timming?

You can also post your vin# so they can see the results of your test and give you an idea of what you need to do.

 

[dods1600]

It is all stock... But is there a difference in the block casting between 71 and 74?

[Bruce]

There are only 2 significant changes.  The CR on the 74 is lower by .25:1, and the 74 uses 8mm head studs with steel inserts, while the 71 uses 10mm studs with no inserts.
Neither of these will affect aircare.  Likely it is something external.  Do you have an 009 distributor?  Best is to post a pic of your engine.

[dods1600]

Here it is

[Bruce]

That's a start.  There are several different distributors and carbs.  It is possible your carb doesn't match the dist, or vice-versa.
Need a close-up pic of the engine, showing detail of the carb and dist.

[egspot]

That looks like a one vacume distributor (71?) the carb looks like a 34pict and i am not sure but, the carb would then have two ins for vacume.