B20 Vtec piston questions

[.Dave]

Hey guys, looking to build a b20 vtec, and have started collecting parts for the swap.
After a bit of research ive heard of notching the pistons for use.
My question here is... well what exactly does this mean (forgive my noobness, gotta start somewhere) and which pistons would be best to use (can I use b16a pistons or would b20 standard ones be better (looking to stay on a tight budget))
For reference, it will be a b16 head with b20b8 bottom end

also, any recommendations/experience regarding workshops around Sydney area?

Thanks in advance

[Adrian @ SAS]

Std bore for B20 is 84.00mm
B16A & B18C are 81.00mm
So no, that won't work.

The talk about the notching of the pistons is because the b-series vtec head has valves 1mm bigger in diameter than the flycuts in the b20 pistons.
Aftermarket pistons don't have this issue

Use CP pistons - part number SC7117 (84.00mm), SC7118 (84.50mm) or SC7119 (85.00mm)
or if you stretch your budget use Toda 85.00mm pistons P/N: 13010-B20-000
If you go oversize, be sure to use a dummy head when bore & hone is done.
You'll need rods with these or modify the std rods (but that's kinda uneconomical)
also balance the bottom end properly (2nd order harmonics kill these engines)

hope that helps

[.Dave]

much appreciated!

Assumming youre able to do the balancing of the engine? will pm regarding balancing and tuning once ive collected all the parts :)

thanks again

[prockey12]

Anyone know much about RS Machines 84.00 mm for b20? Are they suitable for turbo?

[dougie_504]

If they're forged I don't see why not.

Just make sure that 84mm is what you need. Get your cylinders measured before you buy pistons...

[cbauto]

Std bore for B20 is 84.00mm
B16A & B18C are 81.00mm
So no, that won't work.

The talk about the notching of the pistons is because the b-series vtec head has valves 1mm bigger in diameter than the flycuts in the b20 pistons.
Aftermarket pistons don't have this issue

Use CP pistons - part number SC7117 (84.00mm), SC7118 (84.50mm) or SC7119 (85.00mm)
or if you stretch your budget use Toda 85.00mm pistons P/N: 13010-B20-000
If you go oversize, be sure to use a dummy head when bore & hone is done.
You'll need rods with these or modify the std rods (but that's kinda uneconomical)
also balance the bottom end properly (2nd order harmonics kill these engines)

hope that helps
whats your view on Toda 85mm bore longevity on a highly strung engine?
Good for 100k plus km's DD duties?
Would you prefer 89mm stroke or 87.2mm?





Anyone know much about RS Machines 84.00 mm for b20? Are they suitable for turbo?
I would prefer to use b18 if you want to go forced induction.

[Adrian @ SAS]

whats your view on Toda 85mm bore longevity on a highly strung engine?
Good for 100k plus km's DD duties?
Would you prefer 89mm stroke or 87.2mm?

85.0mm bore is no issue for high milage daily driver.
For a highly strung engine.
Reliability for high milage comes from both the machining & the assembly.
But also critically the engine break in procedure & then the tune & long term maintenance.
Run it in hard & it'll last forever... treat it like a silk worm & it'll be an oil burning shitter.
Machining...
The piston to bore clearance needs to be 0.0009". (For the above pistons)
The finnish needs to be a plateau hone.
The machining needs to be done with a torque plate in plate & girdle etc attached.
The balance also needs to be spot on to + or - 0.05g as a minimum
90% of machine shops won't, can't or simply don't believe that...
Assembly...
Clean enough to eat off....
Ring gaps & bearing clearances must be exactly right, no exceptions
Pistons go in dry - rings clocked per manufactures spec
No chamfer at the top of the bore - it should be square & finished by hand with 800 wet'n dry.
& the bottom of the bore needs to be de-burred in the same way.
(So many people forget this - many famous US block sleevers included)
Head gaskets should match bore size exactly & always provide at least 0.030" piston to head clearance.
B-series... Use K20A valve angles, it's a 5kw leg up everywhere for nothing.
Don't use oversize valves... & only port the throats & leave the exhaust pretty much untouched.

If your cams are symmetrical (even) or intake around 10deg more than exhaust, you pretty much can't go wrong. (Eg 305@12.5In / 295@12.5 Ex)

Re stroke,
I prefer B18C stroke, rod, rod bearing & rod ratio to B20.
I also prefer a sleeved B18C over a B20 block too.
Others prefer the B20 stroke.
Both work

Anyways... too much blaaa & this is not my thread

[.Dave]

feel free... always good to hear it

[prockey12]

I got the rs machines in my b20 vtec
Was just wondering whether they're suitable for forced induction
If u want more info suss my for sale ad as im trying to sell it haha