Jump to content
SAU Community

Recommended Posts

Hi everyone.

I have a fellow board member who wants to sell me some custom wiseco forgies, with wrist pins and rings and locks.

87mm

1.260 compression height

.165 dome rise

16cc dome volume

what i've been told is that I can get 11:1 compression by decking the block to get the piston out of the bore by 0.01 inches, get a 1.2 mm (0.47) headgasket, and shave the head to achieve 60cc's or whatever is required to get 11:1. they are for RB25/30 combo, but I'm using an RB26 head.

is this a good idea. by that, i mean, is using the headgasket area an ideal way of building up the quench, or should it ideally be built up using the block and piston at 0 over or under the deck?

does anyone know if the valve clearances will be an issue with 8.7mm cams? Also, what if i want to go higher at one point? will i be able to, if increase the lift (after making the head compatible with the longer/higher cams), and still not hit the pistons?

they are originally to obtain a 9.3:1 CR, so I think they will be pretty close to what I need. But then again, wiseco measured up their RB26 head at 66cc. So It's possible that by putting this into a head with lets say.... 64cc, i'd have closer to 9.8 or something to start with.

I've posted a picture.

The reason I ask is that I'm getting this set (brand new) for half the price of a custom set from a distributor, and it's also free shipping too.

my machinist wants to know if they will be compatible with this setup before i buy it, but I think it is, and i have a feeling he's gonna say no.

(im also posting this in both the n/a and engine forums, because there is no "general engine" forum ,and i'd like both turbo and n/a enthusiasts to be able to view this and help me out. Thanks :P )

post-29116-1184375460_thumb.jpg

Sorry, piston height should be close, i would deck it so the pistons sit 10thou(.25mm) proud, and then use a 1mm head gasket, then deck the head for correct comp.(check all the measurements includding ccing the pistons and head before you machine anything)

Sorry, piston height should be close, i would deck it so the pistons sit 10thou(.25mm) proud, and then use a 1mm head gasket, then deck the head for correct comp.(check all the measurements includding ccing the pistons and head before you machine anything)

Always coming through adriano. how do i send you a 24 of Toronto's own beer :blink:

1 thou proud is over the deck, correct? with a 1.2mm gasket, that would mean i could get .46 quench area, correct?

I guess I should shoot for .36?

what's everyone's thoughts on quench with the RB head, some engines require different quench is what I hear, depending on combustion chamber design.

is decking the head a smidgen usually a good thing?

the pistons are 16cc dome. however, wiseco states that the RB26 head is 66cc. I don't think that's correct, therefore, I've already got a leg up on the compression, being that usually heads are 64cc and thereabouts.

I think their combustion chamber was polished.

Edited by Careless
Always coming through adriano. how do i send you a 24 of Toronto's own beer :blink:

1 thou proud is over the deck, correct? with a 1.2mm gasket, that would mean i could get .46 quench area, correct?

I guess I should shoot for .36?

what's everyone's thoughts on quench with the RB head, some engines require different quench is what I hear, depending on combustion chamber design.

is decking the head a smidgen usually a good thing?

the pistons are 16cc dome, btw.

Expres post of course!LOL, i would try to get 30 thou. The smaller you can run without hitting, the better. If the pistons sit 10 thou proud over the deck, and you run a 40thou(1mm)gasket then you end up with 30 thou. You may have to machine the dome of those pistons down a little, as a rough calc gives it 12.1:1 comp, but you should bore and hone the block, then dummy assemble the bottom end. Then do all the measurements, and figure out what needs to be decked how much, then your home and hosed. Just remember whenever you build an engine like this, treat it as a custom job and dont rely on anything written on the part boxes, as a small difference here can make a huge difference in compression.

Expres post of course!LOL, i would try to get 30 thou. The smaller you can run without hitting, the better. If the pistons sit 10 thou proud over the deck, and you run a 40thou(1mm)gasket then you end up with 30 thou. You may have to machine the dome of those pistons down a little, as a rough calc gives it 12.1:1 comp, but you should bore and hone the block, then dummy assemble the bottom end. Then do all the measurements, and figure out what needs to be decked how much, then your home and hosed. Just remember whenever you build an engine like this, treat it as a custom job and dont rely on anything written on the part boxes, as a small difference here can make a huge difference in compression.

awesome.

My only beef with the pistons is that the dome height and the dome volume attribute to their weight, sitting at 411 grams per.

I might get them machined out to lighten them to 350 grams if possible.

awesome.

My only beef with the pistons is that the dome height and the dome volume attribute to their weight, sitting at 411 grams per.

I might get them machined out to lighten them to 350 grams if possible.

Are you able to check the dome[crown thickness before you buy them?

Are you able to check the dome[crown thickness before you buy them?

well. the pistons are 1200 dollars new.

i'm getting them for 600, still new, but not useful to the current owner.

therefore, whether they are heavy or not, I bought them because it's a steal of a deal.

sure it's a little heavy for N/A, but whatever.

I'm sure they've got a deep crown, and that they can be machined quite a bit.

Are you able to check the dome[crown thickness before you buy them?

I have a set of these and emailed Wiseco about shaving the dome. This was the reply.

If there is milling inside of the dome to hollow it out, I would say no.

If it looks to be a solid dome, then yes. Minimum thickness for any part of the

crown would be .150".

Best Regards,

Wiseco Piston Co. Inc.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I know why it happened and I’m embarrassed to say but I was testing the polarity of one of the led bulb to see which side was positive with a 12v battery and that’s when it decided to fry hoping I didn’t damage anything else
    • I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
×
×
  • Create New...