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Re: [T3] Some T4 engine questions.....


Hello-

> Porsche made a number of changes to the type 4 engines they used. I've
only
> heard about these and can't verify them first hand. The ones I've heard of
are
> that the fan hub and flywheel are castings on the VW engines, while they
are
> forgings on the Porsche.

The flywheel, yes, but not the fan hub.

Also, between 411/412 Variant, 411/412 Sedan, Bus, and 914, there are a
number of configurations for cooling tin (the parts that seal the engine
bay), oil filler setup, oil breather setup, dipstick position, exhaust,
mechanical fuel pump mount, fuel injection (specifically how the heck the
air cleaner fits), etc.

These are mostly "superficial" changes.  The most major ones were
specifically with the 2.0L 914 engine and its heads, exhaust, and fuel
injection.


> I believe the change from 1700 to 1800 was an increase in bore, while the
> change from 1800 to 2000 was an increase in stroke, so upgrading from 1800
to
> 2000 is expensive, requiring a new crank. If you're thinking about going
this
> direction, look for a 2L to start with.

Odd as it seems, that's not the correct chronology.  First, there was the
1.7 (90x66).  Then, there was the 2.0 (94x71).  It was first developed for
914-4 to replace the 914-6 in 1973, and was later detuned for bus engines in
1976.  In 1974, the 1.7 was upgraded to a 1.8 (93x66).


> You should also know that repair parts for the 1800 are much more
expensive
> than either the 1700 or 2L, so that is another reason to avoid it.

They really aren't more expensive.  Only the P&C are really unique.  To
replace them, bore out the cylinders to a bigger size and get different
pistons.  93-96mm cylinders have the same register - only the 1.7 cylinders
are smaller (and unsuitable for a reliable overbore to 96mm).

Take care,
Shad Laws
LN Engineering - Aircooled Precision Performance
http://www.lnengineering.com

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