Potential NF Piston Option??? Engine Experts Help.

Fri Oct 4 17:51:46 EDT 2002

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Mike,

Yes the head is almost done.. I flowed it in a DIY bench flow, not very
reliable, but I can't afford all these costs in engine preparation. Everyti=
me
I think about it, I remind myself, "...you have to buy more tires..." So, I
measure the $$$ in tire #'s. We'll see next week what improvement I have.
Also, I have before pics, and will have after pics leter this month.

I have 3 cams. The stock, a 272, and a 296. I can go really deep. The plan =
is
in a tight rally like Rapidan,VA, I would use either the stock or the 272, =
but
in a high speed one, Sandblast SC, I would use the 296. Also, I need the st=
ock
one for the annual state inspection. ;).

I have a tubular EM to 2.5" tubes, a generic V8 cat (I'm surprised it passes
inspection with flying colors) and a glasspack.

Ian,

This is a rally car, so reliability is very important. Also, I want in an
emergency situation run with 93 gas. I would be uncomfortable to go to a
highyway with 93 gas and 14:1 CR.

Also, the works N/A coupe(quattro though) used 11.5:1 putting out 200hp.
Granted they had individual TB's (one for each cyl.!!!), and I will be using
the stock TB with a 1.5mm bigger disk, and a welded pin to open the 2nd
butterfly a tad earlier. So, the target is something like 170hp.

Thanks again for the all the inputs,

Carlos.

ps. Javad, you can see that I end up getting a radical cam. Mihnea, yes I
bought the one we talked about.
>From: "Michael Gough"
>To: passat TS
>Subject: Re: Potential NF Piston Option??? Engine Experts Help.
>Date: Fri, 04 Oct 2002 08:48:50 -0700
>
>I gave you the link in the last email....
>http://not2fast.gotdns.com/turbo/compression/compression.html
>What I did to find the #s....
>The 7A and 16v motors both have the same size combustion chambers. They al=
so
>have very similar compression ratio. So I put in the 16v piston, with the
>10v head volume and got about 14:1. You'd probably need to notch them since
>the valve reliefs would be in the wrong place, but no big deal. Cost is
>always an issue. I see no reason why you can't mill the head to 1mm. I'd
>check with a scrap head first just in case, but I've milled Alfa heads down
>to the valve seats (It's a hemi head) If you cut into a water passage or
>something (unlikely) you can always mill the rest off the block. The issue=
 I
>see is the timing belt, but it's been a wile since I've done one, so I don=
't
>exactly remember how much adjustment there is for it.
>I assume with all this compression you're going to port the head a bit, use
>a hot cam, and efi? :)
>Mike
>
>I had great answers so far.
>
>Just to help the discussion.
>
>1. I got the 7A information from 2 very good sources (one is Ron Wood, of =
VW
>Specialties). So, it is possible. I tried to get a bottom from a 7A, but h=
ad
>no success (too much $$$ for a good one).
>
>2. The is a full blown race car. It will use only race gas, hence the high
>CR.
>3. Mike, I'll check these places again. The key is the money. I can get
>custom pistons, but that will add a big $$$ to this project.
>
>4. Another lister(Alan Kramer) suggested the clay test. I just wanted to
>avoid it, since I'll have to R/R couple of times during the process, and t=
he
>ARP head bolts I bought were in back order until the end of the month. I
>think if I use the stretched bolts I have in the donor NF, the results can
>be fouled.
>
>5. One of the answers came up with the 1mm deck. I have 0.75mm in the head
>to reach the max stated at the Bentley. Can you point me to the site you d=
id
>the calculations, and the values you put in the formula? I might be using a
>wrong number. or Can I go beyond the Bentley number?
>
>Thanks again for all the answers.
>
>Carlos.
>
>
> >From: "Michael Gough"
> >To: passat TS
> >Subject: Re: Potential NF Piston Option??? Engine Experts Help.
> >Date: Fri, 04 Oct 2002 08:10:48 -0700
> >
> >I'd get the whole 7A bottom end and toss the NF head on top. From the
> >calculations I have it'd give you like 14:1 compression though....
> >http://not2fast.gotdns.com/turbo/compression/compression.html
> >Also there are a TON of VW tuners with high comp pistons floating around.
> >Euro spec seems to have a huge selection
> >http://www.eurospecsport.com/caspist.html
> >HTH
> >Mike
> >
> > > [ Converted text/html to text/plain ]
> > > I want to raise the CR of a NF Engine as much as possible. The target=
 is
> > > 11.5:1 but
> > > anything better than the 10:1 I have today will be welcome.
> > >
> > > The ideal situation would be custom pistons, but all the places I
contacted
> > > want a
> > > minimum of 2 sets ordered.
> > >
> > > Here are the options I found so far:
> > >
> > > 1. Find someone interested in split the custom run at around $500 for
each
> > > set.
> > > Pistons anyone?
> > >
> > > 2. Stock 7A pistons. They will raise the CR to 11.2:1, but the ones I
>founded
> > > are
> > > too expensive. Can anyone find a set for under $600.
> > >
> > > 3. I found at the Wiseco catalog a set for VW 1.8l that has several
ideal
> > > measurements. I called them yesterday and the tech person seems to ag=
ree
>that
> > > it
> > > would work. It will raise the CR to 10:8:1. The good thing is that it
will
> > > cost under
> > > $400/set, the bad thing is that it has flat top. It has enough materi=
al
to
> > > machine the
> > > pockets, but that would reduce the compression to 10.3:1. This is the
same
>as
> > > deck
> > > the cyl head at $40.
> > > Questions:
> > > 3.1 Can I use flat tops? (valve clearance, combustion problems)
> > > 3.2 Can I use flat tops and deck the cyl head to achieve a higher
> > > compression
> > > without the above problems?
> > >
> > > I really appreciate any help, I'm about to finish the head work(last
>polishing
> > > phase)
> > > and need to make this decision.
> > >
> > > Carlos.
> > >
> > >
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