alternate R16 pistons

gmiles · Post by **gmiles** » Wed May 02, 2012 1:33 am

A year or so ago I bought some Toyota 20R pistons to play around with as an option for my R16 (5 main). The Toyota pistons, IIRC, had a stock bore of 89mm? I don't know if an R16 can be bored out that far. The pin diameter was the same as the R16. The problem I ran into, however, was the Toyota pistons had a pin height that placed the piston about .25" lower than the stock R16 domed pistons. With what D Smith posted in another post (see below), I wonder about the possibility of using a 5 main R16 block, R16 rods, Toyota pistons, and an H20 crank?

Based on my crude math, it would put the pistons very close to deck height. I'll look at the pistons again when I have time next week.

D Smith
"Guess I mis-typed there.

The main point I was trying to make above was that you CANNOT use the H20/U20/R16 pistons with the R16 rods and the H20/U20 crankshaft. It puts the top of the piston too far above the block deck.

"1/2 stroke + rod length + piston pin height = approx deck height (approximate because we don't know whether the blocks have been "shaved" either....it needs to be measured if you plan on getting close to .040"!)

Deck height is approx. 227 mm
1/2 stroke (H20/U20) = 41.5 mm
R16 Rod = 152.45 mm
H20/U20/R16 pin height = 41 mm (yes they are all the same)

41.5 + 152.45 + 41 = 234.95 mm or approx. 7.95 mm (0.313") above deck

That is why I suggested custom or those talked about but never specified VG30 pistons........(which I also tried to find but wasn't able to......maybe they are modifying the piston? )

(edited to correct the 1/2 stroke #)"

SLOroadster · Post by **SLOroadster** » Wed May 02, 2012 8:12 am

I guess you could have custom rods made to use the pistons. I'm not sure if it would be worth doing or not.

Will

gmiles · Post by **gmiles** » Wed May 02, 2012 10:46 am

Depending on parts $ it may not be cost effective. I was intrigued after reading that post for the millionth time. I hadn't realized it may work with Toyota pistons, an H20 crank and R16 rods. The Toyota pistons are flat tops so it may be really close. New R16 pistons are $450 so I would need an H20 crank for less than that. Another downside would be once the block is bored out to 90mm that's it. A resleeve would be necessary.

SLOroadster · Post by **SLOroadster** » Wed May 02, 2012 2:23 pm

gmiles wrote:Depending on parts $ it may not be cost effective. I was intrigued after reading that post for the millionth time. I hadn't realized it may work with Toyota pistons, an H20 crank and R16 rods. The Toyota pistons are flat tops so it may be really close. New R16 pistons are $450 so I would need an H20 crank for less than that. Another downside would be once the block is bored out to 90mm that's it. A resleeve would be necessary.

The good news is that Nissan blocks are notoriously hard so doing an overbore is rarely needed. There are also worse things than sleeving a block. It might be an interesting experiment.

Will

Post by **ppeters914** » Wed May 02, 2012 8:49 pm

gmiles wrote:New R16 pistons are $450 ...

Really? Seriously? Crap........

Garm · Post by **Garm** » Wed May 02, 2012 9:51 pm

How big can an R16 get with sleeving? That sounds like a fun project with custom pistons.

SLOroadster · Post by **SLOroadster** » Wed May 02, 2012 11:12 pm

Garm wrote:How big can an R16 get with sleeving? That sounds like a fun project with custom pistons.

I'd say talk to Lou Mondello. I think he's done an R22 or something crazy. A stroker, extra long rod, overbored R16 (assuming you can get a headgasket made for it.) could be interesting. Still, from what I know, the R16 head is the limiting factor. Still, it would be a mega torque monster, build a 3.5 rear end and you'd be rolling with something cool. With a 5 spd it wouldn't be quick off the line but it would make for a sweet freeway car.

Will

Daryl Smith · Post by **Daryl Smith** » Thu May 03, 2012 9:33 am

Well, doing the math, that would still leave the Toyota piston .063" above the block deck, and hitting the head...... prolly don't want to go more than ~.010" above the deck (check with your machinist).

If doing the stroker, try to find the VG30 pistons that are mentioned all the time but no part # ever shows up so I tend to think it's imaginary........

Custom pistons can be had for near the $450 mark........

SLOroadster · Post by **SLOroadster** » Thu May 03, 2012 9:55 am

Its not a matter of VG30 pistons being mythical, its knowing which vg30 pistons to use. My guess is that they are the NA first generation version, but I don't know for sure.

Will

Post by **spl310** » Thu May 03, 2012 10:10 am

Who knows which ones to use Will?

fj20spl311 · Post by **fj20spl311** » Thu May 03, 2012 10:25 am

Daryl Smith wrote:Well, doing the math, that would still leave the Toyota piston .063" above the block deck, and hitting the head...... prolly don't want to go more than ~.010" above the deck (check with your machinist).
........

Cutting the top of a piston to get the correct deck height is standard.

You might even cut a dome profile.

Post by **tjp** » Thu May 03, 2012 10:55 am

fj20spl311 wrote:
Daryl Smith wrote:Well, doing the math, that would still leave the Toyota piston .063" above the block deck, and hitting the head...... prolly don't want to go more than ~.010" above the deck (check with your machinist).
........
Cutting the top of a piston to get the correct deck height is standard.
You might even cut a dome profile.

If you are popping up that much, would "eyebrow" cuts be enough to clear the valves, or would the piston have to be cut down AND eyebrow cut if domed?

tim

fj20spl311 · Post by **fj20spl311** » Fri May 04, 2012 12:15 am

tputland wrote:
If you are popping up that much, would "eyebrow" cuts be enough to clear the valves, or would the piston have to be cut down AND eyebrow cut if domed?

tim

That is dependent upon the cam profile and how much has been milled from the head.
I would be important to calculated the compression ratio.

IIRC, the stock 1600 dome pistons are not eyebrowed.

gmiles · Post by **gmiles** » Fri May 04, 2012 5:05 am

The Toyota pistons are flat tops and notched for valve clearance and the .25" difference in pin height was an estimate. I have a picture somewhere of the two pistons next to each other, on the same piston pin. I'll post it, for the curios and bored. When I get back to SoCal, I'll look at the pistons again and get measurements.

Anyone bought an H20 crank recently? This may all be for naught if the crank is too pricey. For me, it's all about ease of maintenance and easy to get replacement parts. And the engine doesn't care what pistons are in it....

something else that's been on my mind is fuel injection on an R16...hmmmmm,,,another topic for another day....

Post by **Poobah** » Mon May 28, 2012 1:49 pm

I bought a whole H20 motor last Friday. I'm trying to figure out what pistons to use. R16 domed pistons are 12.x to 1 compression and have to have the skirts trimmed? U20 flat top pistons are 10/11 to 1 compression and are used as is? H20 dished pistons are 8/9 to 1 compression and are used as is? (the H20 data I have says the motor has 8.1 to compression).

Which pistons are the best to use?
U20 pistons are pretty expensive. Are they NLA from Nissan?
Do they make a flat top H20 piston? (I read some H20's have flat tops)
What is the max oversize without having overheating problems?
Can I get the H20 cam reground?

Thanks for all the help.

Steve

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