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

[Ben Swann]

Showstopper?  Etka shows NF piston as 82.5 vs. 3B/MC as 81 which I take is diameter.

So I'd need oversize pistons  - 7A uses 82.5 too and has the recess for valves.

Would have been nice to use this block.  Just threw away a couple JX/KT that no one
wanted.

Ben

-----Original Message-----
From: Ben Swann [mailto:benswann at verizon.net] 
Sent: Saturday, March 27, 2010 12:50 AM
To: 'Cody Forbes'
Cc: 'P Cole'; 's-car-list at audifans.com'; 'Quattro List'; '200q20v at audifans.com'
Subject: RE: [s-cars] NF or 7A block substitution (and possibly MC)

OK - looks like I'm getting somewhere.

NF block (have the NF crank, pistons and rods but probably won't use) with some
combination of pistons and rods. AFAIK this block does come with piston oil squirters
installed.  If not I can install some - if I recall it is not a difficult retrofit.  No
problem machining oil return into the boss on the block - I forget if there is a return
in the 3B pan like there is on the AAN.

I might be able to use the 3B(20V) crank from wasted engine if it is not shot peened by
the flailing rod ***story below***

If 3B crank shot then I have MC(10V) crank 

I have complete set of 3B rods and Pistons - not the ones in the messed up engine.  

I also should have MC pistons and rods, but sounds like using 3B internals is best.

So in short, I think if the 3B crank is wasted then my best choice it to install MC-1
crank with 3B rods and pistons.  There ought not be any need to use special head gasket
or anything like that.

Hopefully I can do a quick teardown and build in order to get the car on the road.  In
the long run, I have the 3.7 aluminum V8 I'm building to accommodate twin turbos!  

Ben

Story *** I lent the Deerslayer http://www.gtquattro.com/200Q20V8.html to a friend - ig
mistake.  He must have mashed the gas pedal while merging.  Said he was not able to shut
it down immediately and engine bounced off the rev. limiter for about 15 sec.  He called
to report what he thought was noisy lifters.  The car went over 150 miles with the rod
coming loose and eventually flapping about.  All this time thinking it was noisy
lifters!  Driver finally realized the problem was not coming from the top of the engine
when the car stalled.  Upon restart, noticed the noise had gotten worse and saw some oil
leaking around the turbo - still thought problem was due to losing oil pressure thru the
oil line.   And no I was not the driver!  The minute I started the car up I winced at
the carnage! So much for no good deeds going unpunished.

-----Original Message-----
From: Cody Forbes [mailto:cody at 5000tq.com]
Sent: Saturday, March 27, 2010 12:15 AM
To: Ben Swann
Cc: P Cole; s-car-list at audifans.com; Quattro List; 200q20v at audifans.com
Subject: Re: [s-cars] NF or 7A block substitution (and possibly MC)

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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