Block rebore

[mcandmar]

Interesting on the 83mm, didn’t know anybody had taken them that far. I went for 81.5mm when i got my block done, could have got away with half that just to clean the bores up but i didn’t see the harm in rounding up to .5mm oversize. Maybe i should have gone a bit more to squeeze a few more cc's out of it

On that point the 7A's are 82.5mm bore, but yet all the turbo motors were 81mm. I wonder why the Audi gods never enlarged the turbos motors

[pixsaudisex2]

isnt a 1400cc engine ment to be the ideal size to put a turbo on ..

[porkkis]

The valve behind oil pressure sensor is a check valve. It leaves oil in the rising head channel and does not let it drain. It's only for the head channel and not for mains etc.

Beware when tightening it. It's quite soft and over tightening will break it and therefore block the channel.

[Flat on my back]

Techy question.

Anyone know the centre to centre dimension between bores on the various 5 pots, eg does the 7A have more 'meat' between them compared to the turbo blocks.

Ta.

[A80Avant]

i had a rebore.it was 81.26mm for mahle pistons 81.20mm.This is concidered the 1st stage rebore.After that there is another rebore than can be done to 81.56mm for 81.50mm pistons again from mahle.
After that you only get custom pistons and rebore up to 83mm.
Javad from 034motorsport told me that i could use the OEM metal gasket with 82.5mm pistons

[mcandmar]

Same spacing, so 7A has less between each cyl. Pic here,

http://www.cr-x.org/cq20v/manifold/images/block4.JPG

Mark.

Anyone know the centre to centre dimension between bores on the various 5 pots, eg does the 7A have more 'meat' between them compared to the turbo blocks.

Ta.

[Flat on my back]

Errrrrrrr no, please?

so, that means i have 1.5mm less to play with compared to the standard bore on the turbo lump. Just as well mines only having a 20 thou overbore?

Any chance of measuring the metal between the pistons whilst i go and check out my 7A lump.

Just measured mine at 5.5mm so that means the turbo lumps should be 7mm?

[aelred]

Do not forget that each set of piston rings has to be gapped to its own cylinder. This is very important specially with after market pistons and rings and hi performance engines.

[A80Avant]

aelred,what do you mean gapped?

[s2dude]

aelred,what do you mean gapped?

He means there has to be a manufacturer specced 'gap' for the ring to have some expansion under heat and pressure.

The 'gap' has to be measured individually around each piston for each bore.
just use a feeler gauge and file to get it correct

[mcandmar]

@Papvas i found this vid a while back, jump to 2:20 and you see him do it.

http://ie.youtube.com/watch?v=kVXj4ULvPJQ

[A80Avant]

will do!
thanks!!!

[markrs2]

Looking at this valve I would say it would fit all blocks. The o seal on the end fits into the feed from the oil gallery and the spring holds it in place. The main difference to the standard valve is that, instead of the oil flowing through the valve and exiting from the opposite end, the oil exits through the side of the valve and then must pass through the small gaps between the hexagonal sides of the valve and the threaded section of the oil channel that the standard valve screws into. Do you think this restricts flow to the head a bit?

I've seen a pic of the "modified valve" on here and it looked very different, so much so i dont think it will fit an early block. Think it was in one of MarkH's engine build threads.

[Big_kev]

spray

Guys this is probably a very amatuerish thing to ask, but in the video the mechanic was spraying something on to the gaskets. What was it and what is its purpose.

[Jamo]

Do not forget that each set of piston rings has to be gapped to its own cylinder. This is very important specially with after market pistons and rings and hi performance engines.

Guys what are the recommened places to do this?

Aelred how much do you rough charge?