[s-cars] NF or 7A block substitution (and possibly MC)

[Cody Forbes]

Nope, the 20v cars used different size rod journals on the crankshaft.  
You'd need a 20v crank to match the 20v rods. Or you can use a 10v  
crank (turbo and NA are the same) with MC rods and 3B pistons.

IIRC the only difference in the bare block between post 1985 10v  
blocks is the hole for the turbo oil return and I'm not sure if the  
non-turbo blocks have the piston oil squirters. All other turbo  
related parts (oil filter housing, turbo coolant return freeze plug,  
head, etc) is all a matter of bolting it on.

-Cody (mobile)

On Mar 26, 2010, at 11:04 PM, "Ben Swann" <benswann at verizon.net> wrote:

> 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
>
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