Golf Mk.2 1.8 8v max rebore?/headwork/crank combo

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georgecooper06
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Golf Mk.2 1.8 8v max rebore?/headwork/crank combo

Post by georgecooper06 »

Hi guys, i have a 1989 mk2 1.8 gti 8v, and want to get the most out of it that i can, for insurance reasons i cannot change the block, however i can rebore and change cams/cranks etc, so was wondering what the best combination was for a good amount of power but retain the drivability, as in i dont want a full on race engine that wont tick over and has no power below 4krpm etc.
Currently my thoughts are to swap the cam, do a rebore, and the current wisdom on the head seems to be to go for a gas flow porting, and valve size increase, from 40i/33e to 40i/35e, are these the best valve sizes? (ive seen 42i/35e, 40.5i/35e around online) also, im unable to find a really definitive answer on what the max rebore size of this engine is, its a digifant from 1989, and as far as i can work out that means its an engine code PB - and currently has 81mm bore with 86.4mm stroke, giving 1781cc. Pistons for this engine are available up to 83.5mm bore but im unsure as to whether they are for different blocks with thicker walls or something, and which ones my block will take, i want the engine to last and not need a rebuild after 100 glorious miles with massive power.
Also there seems to be talk of the possibility of using a crank from a different engine and grinding some clearance on the block to fit it, and will take it to even higher displacement, what are your thoughts?
Thanks - George
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PapaJo
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Re: Golf Mk.2 1.8 8v max rebore?/headwork/crank combo

Post by PapaJo »

You will be fine to bore to 83mm or 83,5mm. Go for 83mm to leave some room if required later on in engine live if something happen to pistons or rings. 40/35 is a good combination valve set and compliment tgat with a port and flow job and a 276 duration cam and then get a proper tune and you have a very good magical 1900cc motor. Putting a 2L crank is doable with the required clearancing needed to the block, intermediate shaft gear and changing to the 2e oil pump. Different pistons though due to longer stroke on crank.
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panic-mechanic
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Re: Golf Mk.2 1.8 8v max rebore?/headwork/crank combo

Post by panic-mechanic »

I am assuming you are not form South africa as we did not get a 1.8 on digifant. Locally we had a microbus that had a 2.6 L 5 Cyl engine and we use those pistons with the 2l crank to make a slightly larger than 2l engine.
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georgecooper06
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Re: Golf Mk.2 1.8 8v max rebore?/headwork/crank combo

Post by georgecooper06 »

Thanks for the replies! yes i'm from England, which crank is the best one to use?
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PapaJo
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Re: Golf Mk.2 1.8 8v max rebore?/headwork/crank combo

Post by PapaJo »

panic-mechanic wrote: Mon May 21, 2018 1:00 pm I am assuming you are not form South africa as we did not get a 1.8 on digifant. Locally we had a microbus that had a 2.6 L 5 Cyl engine and we use those pistons with the 2l crank to make a slightly larger than 2l engine.
Follow this advise from panic. Use a 2L crank and do the clearancing for the crank as I mentioned earlier.
georgecooper06
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Re: Golf Mk.2 1.8 8v max rebore?/headwork/crank combo

Post by georgecooper06 »

After some more digging it looks like the best way to go is, 2l crank with new pistons, what i dont know is what new pistons exactly i need, i cna buy an ADY 2l 8v engine complete for very cheap, will the crank and pistons from this go onto the 1.8 block i have with a rebore? and if im reboring anyway would it be better to bore to 83mm and get new pistons too? if i were getting new pistons which ones do i need? http://techtonicstuning.com/main/index. ... ts_id=3198 these?
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