NF or 7A block substitution (and possibly MC)

[Ben Swann]

Thanks Paul, all!

OK - How will the combination of NF block with 3B Pistons and Rods work?  This is a
combination I have/can assemble with parts on hand.

Is the NF block different than the MC blocks or is the difference crank and rods?

Ben

-----Original Message-----
From: P Cole [mailto:pcolegrps at comcast.net] 
Sent: Friday, March 26, 2010 10:25 PM
To: Ben Swann
Subject: RE: NF or 7A block substitution (and possibly MC)

On Fri, 26 Mar 2010 19:48:04 -0400, Ben Swann wrote:

>Thanks all for the replies so far.  I just wanted to know if I could use the NF block
as a reasonable substitute for a blown 3B.   I have in my garage with all parts to
rebuild the NF.  I may have an MC sitting here too.  I have internals for both MC-1 and
NF.
> 
>Interesting that the NF which is high compression motor makes low comp when putting on
a 3B head - doesn't make sense.  When you put an NF head on an MC-1 block - that is good
combination.  MC-1 is a good substitute for the 3B.  So, what makes the compression go
so low?
> 

Combustion chamber SIZE- in the 10v heads it's 27cc in the 20v heads it's 44cc ( or
something like that)

>I thought that the NF and 7A were similar, if not the same block? I don't have a 7A but
can get one if that is a better alternative.
>

Piston size and dish depth are another BIG difference between the various I5 engines.
The high compression 10v's have small dish pistons in the same combustion chamber as the
10 turbo cars do hence the higher CR.

>Is there an ideal combination:  on hand - NF block, 3B pistons and rods,  MC-1 pistons
and rods,  NF pistons and rods.  Rings and bearings, seals for them.
> 
>I would like to use what I have to put together a decent block to install 3B head on -
without getting into procuring odd and esoteric combinations.  Just want to use what I
have on hand, possibly procuring head-gasket and a few odd bits.  No problem machining
oil return line - BTDT.
>

The bigger issue is the crank and pistons - I think all the I5's had forged cranks, all
the turbo cars did for sure. The pistons in most NA cars are cast whereas the turbo cars
all had forged pistons. I think Audi used forged rods in all the I5's but I'd have to
check the NA cars.

>Ben
> 
>S-car-list in copy because I thought I'd seen this done for AAN
> 
--
//************************
Paul R. Cole::pcolegrps at comcast.net