20vt head on 10vt block? Possible?
01-02-2004, 02:22 PM
#31
Re: ok so I see there are 2 issues in putting a 7A head on an MC block... I have one more- and a few
The MC rods should work with the NF or NG pistons, going from memory the wrist pins are the same diameter.
You'd have to get the crank balanced for the new piston/rod combo however. Not too expensive at a competant machine shop.
You'd have to get the crank balanced for the new piston/rod combo however. Not too expensive at a competant machine shop.
01-02-2004, 02:22 PM
#32
lol! Thats certainly one way to look at it!
I'll be CNC'ing one of my 7A heads (probably the ported one, it needs rebuilt and gone through by a machine shop) if I can get a hold of a 3B water manifold (I know someone that has one I can borrow) and seals and dig out the text that has info on seals so I get the depth correct.
01-02-2004, 07:34 PM
#36
Re: Can't use MC rods in place of NG
How are they going to be shorter? I thought all 86.4mm stroke engines used the 144mm rods? Unless they had to move the wrist pin that much lower on the MC. My MC-1 pistons/rods are 210mi from me right now, but I have the 7A's with me.
01-03-2004, 05:38 AM
#37
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The pin height is different
The top ring is lower (more turbo friendly) on the MC pistons which is probably why they made the rods shorter. Yes of course the stroke is the same but the pin height is certainly different between the two.
01-03-2004, 05:42 AM
#38
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38cc combustion chamber on the 20v head, 29cc for the 10v
My calculations are done out on the 034efi forums in this thread: <a href="http://audi.newtsplace.com/forum/viewtopic.php?t=84">http://audi.newtsplace.com/forum/viewtopic.php?t=84</a>
01-03-2004, 09:02 AM
#39
Re: The pin height is different
That makes perfect sense. Lower top ring (compression ring) will result in a lower CR. Move the wrist pin down to help with reaction forces/moments on the pistons and cylinder wall due to the dish and added cylinder pressures.
I took a pic of an old 7A HG if you want to look at it. It is NOT all metal, metal/paper like all others except the AAN/ABY/ADU which is all metal and sized for 81mm pistons. Mark W.(Squidix9) has a copper gasket on his Kolb/AS 2480cc 7A, its a slight spacer to make up for the milled deck on the head. I'd imagine that company could fab one in a different thickness if you wanted to go that route.
I took a pic of an old 7A HG if you want to look at it. It is NOT all metal, metal/paper like all others except the AAN/ABY/ADU which is all metal and sized for 81mm pistons. Mark W.(Squidix9) has a copper gasket on his Kolb/AS 2480cc 7A, its a slight spacer to make up for the milled deck on the head. I'd imagine that company could fab one in a different thickness if you wanted to go that route.
01-03-2004, 11:36 AM
#40
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Re: The pin height is different
The difference in CR by moving the top ring down would be minimal, but certainly a factor.
I'd be interested in pics of the 7A HG. I'm torn between two different head gasket options for my setup.. I could either go with the stock 2.3 head gasket and hope that the added clamping force and resistance to streatching offered by head studs will keep things clamped OR go with the much stronger 3B/AAN HG... the problem there being that I would need to have the gasket bored out as the diameter is only 82mm (needs to be 82.5) as you mentioned..
I'd be interested in pics of the 7A HG. I'm torn between two different head gasket options for my setup.. I could either go with the stock 2.3 head gasket and hope that the added clamping force and resistance to streatching offered by head studs will keep things clamped OR go with the much stronger 3B/AAN HG... the problem there being that I would need to have the gasket bored out as the diameter is only 82mm (needs to be 82.5) as you mentioned..
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