KV NA stroker build

[K Simmonds]

Thanks. Pulls like a train especially up hills which always puts a big smile on your face. Gearboxes are not a strong point on these so got to keep boost levels under control. What are you aiming for Kit with your future build?

Yeah I can imagine the gearbox's aren't too keen on all the extra torque!

I was very seriously considering building up a Eastern European style 'Ghetto Stroker' using Supra pistons and BMW rods with my old NG block/crank by having it re-bored to suit and the big end journals ground off centre to give roughly 2.4. However I've scratched that idea for the time being as I'm soon to be collecting Andy10V's old 3B engine which he rebuilt with forged roads and new bearing's, he's done me good deal on it which I'm really grateful for. Nice one Andy!!!

That's not to say I won't do something interesting with the NG block/crank when time and funds allow.

I have a K26/7 with a Sport quattro comp wheel I'm in the process of getting upgraded, looks like I've managed to find a #8 hot-side for it via eBay for a bargain price.

Target is 450 bhp on 98 ron.

[twoqu]

ADV 2.6 95.5 should be 30.4mm, deck height 221.35 comp 10:1
AAY 2.5 92.8 should be 32.4mm, deck height 220 comp 10:1
Back in the day 2.5 pistons were fitted to 2.6 engines for better compression ratio as these standard SA engines were in a low state of tune due to varying altitude, heat and fuel quality etc.
So in Simons case his 2.5 pistons would need 1.35mm skimmed off the tops for use in 220 block with 95.5 crank. Comp would be up from standard 10:1 which is a good thing, up to Simon as to what comp he is looking for, 10.3 - 10.5:1 would work well with cam and free flow exhaust.

That would work with the 2.6 pistons but not the 2.5 pistons. There is the difference in the compression height to deal with. So its more like 1.35+ 2mm.
Its difficult without seing accurate piston dimensions. But he is using the shortest block with the longer stroke crank and the taller comp height pistons. It would appear that the block height increase on the SA 2.6 was to accept the difference in the stroke. Having said that it would imply that there were no other differences in either the pistons or rods. If the difference in the capacity is nothing other than the stroke increase then the 2.5 must have used either different rods or pistons. Strangely I have seen a BE bearing spec on the 2.5 which implies it has the smaller 10V journal.
I guess all will be revealed at the mock up!

[SA BOY]

Yeah I can imagine the gearbox's aren't too keen on all the extra torque!

I was very seriously considering building up a Eastern European style 'Ghetto Stroker' using Supra pistons and BMW rods with my old NG block/crank by having it re-bored to suit and the big end journals ground off centre to give roughly 2.4. However I've scratched that idea for the time being as I'm soon to be collecting Andy10V's old 3B engine which he rebuilt with forged roads and new bearing's, he's done me good deal on it which I'm really grateful for. Nice one Andy!!!

That's not to say I won't do something interesting with the NG block/crank when time and funds allow.

I have a K26/7 with a Sport quattro comp wheel I'm in the process of getting upgraded, looks like I've managed to find a #8 hot-side for it via eBay for a bargain price.

Target is 450 bhp on 98 ron.

Nice I am also busy with a 3b for my old 10v ur, would be happy with 280 horse.

[SA BOY]

That would work with the 2.6 pistons but not the 2.5 pistons. There is the difference in the compression height to deal with. So its more like 1.35+ 2mm.
Its difficult without seing accurate piston dimensions. But he is using the shortest block with the longer stroke crank and the taller comp height pistons. It would appear that the block height increase on the SA 2.6 was to accept the difference in the stroke. Having said that it would imply that there were no other differences in either the pistons or rods. If the difference in the capacity is nothing other than the stroke increase then the 2.5 must have used either different rods or pistons. Strangely I have seen a BE bearing spec on the 2.5 which implies it has the smaller 10V journal.
I guess all will be revealed at the mock up!

You're right, less 1.35mm and less 2mm = 3.35mm would take you back to standard 10:1 comp. What would a good comp ratio for Simons build be in your opinion? I've had quite a few 2.5s, even sold a few 92.8 cranks. Journal size is definitely the later bigger type same as 7a etc.

[twoqu]

In my opinion Simon should seek help for his masochism! Tuning a NA 10V is not very rewarding. The most cost effective solution is turbocharging and efi. I would think the biggest gains would be from reworking the head rather than a capacity increase.
You cannot just skim mm's off pistons and retain the same comp ratio. As the 10V relies on the piston dish, reducing its volume would increase the comp ratio. Removing that amount of material would almost remove the piston dish completely.

[SA BOY]

In my opinion Simon should seek help for his masochism! Tuning a NA 10V is not very rewarding. The most cost effective solution is turbocharging and efi. I would think the biggest gains would be from reworking the head rather than a capacity increase.
You cannot just skim mm's off pistons and retain the same comp ratio. As the 10V relies on the piston dish, reducing its volume would increase the comp ratio. Removing that amount of material would almost remove the piston dish completely.

thats your opinion but its his build!

[simon20vq]

Thanks for the input by all thus far.
Extra CC's always worth it. The dish in the piston wont be removed even if 1.35mm is skimmed from the piston crown. Hope to have more info Friday once I've seen the guy who does the machining.

[SA BOY]

Thanks for the input by all thus far.
Extra CC's always worth it. The dish in the piston wont be removed even if 1.35mm is skimmed from the piston crown. Hope to have more info Friday once I've seen the guy who does the machining.

Extra cc's always worth it Mr positive here obviously hasn't driven a stroker 2.5/2.6 Why would VW even bothered if there were no gains

[simon20vq]

Pistons machined, my guy works in thou's. Need some m13 con-rod nuts as the m14's are hitting the block even when he machined one down to check (flywheel end).

[SA BOY]

Excellent. I just filed the block, only number 5 needed it, flywheel side as you say. How do the pistons look?

[simon20vq]

OK wondered if that could be an option but will gauge once the rods are all connected up. Yeah good
Got to hone the bores and a few other little jobs and then I can rebuild the bottom end.