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

Sat Mar 27 06:54:08 PDT 2010

No, 3B rods will not fit a MC crank. All 10v cranks are 46mm rod  
journals, all 20v cranks are 48mm journals. All rods fit all pistons,  
but 10v rods must be on a 10v crank and 20v rods on a 20v crank.

I'll add that my direct experiance is with turbo engines of 20v and  
10v plus 7A, but I am very sure that the above applies to all Audi  
5cyl before the new ones of recent manufacture.

-Cody (mobile)

On Mar 27, 2010, at 12:50 AM, "Ben Swann" <benswann at verizon.net> wrote:

> 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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