KV NA stroker build

[K Simmonds]

Have gone turbo as these pistons are perfect with the big dish for lower compression mated with the 20v head. Roughly works out at 9.3:1 same as standard 3b. Added valve cutaways for valve clearance.

Fair play that's quite inventive and not a combo I've seen before, are those my old NG pistons?

I have to wonder how they'll cope with the higher temps & stresses they will be subject to with forced induction, what sort of turbo and boost level are you running?

I'm slowly brewing up something with my old NG block but am going to be using custom pistons and rods, quite likely from a Supra/BMW.

[SA BOY]

Thanks Nev for posting pic's. That's good info. Are you using NG head gasket?

It's a SA supplied head gasket for the 2.5/2.6 Kombis, got them when I was on holiday there. They are Victor Reinz 61-28955-00 Sure to be the same as 7a and ng.

[SA BOY]

Fair play that's quite inventive and not a combo I've seen before, are those my old NG pistons?

I have to wonder how they'll cope with the higher temps & stresses they will be subject to with forced induction, what sort of turbo and boost level are you running?

I'm slowly brewing up something with my old NG block but am going to be using custom pistons and rods, quite likely from a Supra/BMW.

No not your old Ng pistons as they where 2.3 86.4mm stroke. But they do live on in my Kombi with 7a block, crank, rods with 10v cyl head, turbo of coarse Only running low boost on these engines as they are both for Kombi installs. Heat build up in the rear engine bay is a big problem but if boost is kept relatively low then OK. Good torque is what I am after and not 7000-8000rpms.

[simon20vq]

It's a SA supplied head gasket for the 2.5/2.6 Kombis, got them when I was on holiday there. They are Victor Reinz 61-28955-00 Sure to be the same as 7a and ng.

Cool thanks for confirming. When I had VW Splits/T2 & T25 in the past I made ducting to direct cool air and never had an issue with heat build up.
Lots of torque...nice.

Kit funny you mention NG pistons, do you have any spare?

Cheers all.

[K Simmonds]

Sorry Simon unfortunately I can't help with that one, SA Boy had my old NG pistons otherwise you'd have been welcome to them, it shouldn't be too hard find a set or even a complete motor though.

SA Boy- That sound's cool, fair play for working out the combination's.

As you say it's torque not massive top end power your looking for with van installs so I can see low boost with a small turbo working very well, especially with the extra capacity, what do you do about heat, vents and fans?

Edit....any pic's of it all crammed in to a T25?

[SA BOY]

Some engine bay pics.

[simon20vq]

Very smart thanks for sharing. I had a guy come buy some bits off me a few months back and he had a 7a in his t25.

[SA BOY]

7a is a good conversion but lacks low end especially in the t25. Diesel crank definitely helps with much better low down response and still revs OK.

[K Simmonds]

Looks very tidy, good job sir!!!

I bet it sounds pretty dam cool to boot.

[SA BOY]

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?

[twoqu]

Still a bit confused as to how this all stacks up.
Eurospec lists pistons for a 221.35mm block which is supposed to be the SA version. With a 92.8mm stroke crank and 144mm rods the pistons have a compression height of 30.4mm. You have a shorter block at 220mm and a longer stroke of 95.5mm so the piston compression height would need to be 30.4mm - 1.35mm (deck height) and 1.35mm (stroke increase) and still have enough meat to accept the dish that 10V's have.
The only reference to the ADV piston I could find implies the compression height is 32.4mm which may be incorrect if the Eurospec dimensions are correct.
Basically you would need to reduce either the piston compression height or the rod centre to centre to account for the increase in stroke. So for the 92.8mm stroke it would be 3.2mm and 95.5mm stroke it would be 4.55mm (@50% of stroke increase). There is a difference between the longer strokes of 1.35mm which coincides with the increase in deck height from 220mm to 221.35mm.

[SA BOY]

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.

[SA BOY]

Simon let me know what comp ratio you are looking for and I will work out how much to remove from the bottom of the dish.

[simon20vq]

Thank you Nev. What do you recommend? I will be running after market cam big valve head and I'm building a tubular manifold for better flow (although not 100% sure the later will do much).

[SA BOY]

Been working out comp ratio via a comp calculator online. After skimming off 1.35mm off the tops of your pistons, comp ratio would be roughly 11:1. If you were to machine 1.35mm off the tops and the bottom of the bowl you would end up at roughly 10.5:1 which is probably the way to go? Your thoughts anyone.