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Zoid Builds A 25\30

zoidbergmerc

By zoidbergmerc,
in Tasmania

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zoidbergmerc Mentor

zoidbergmerc

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That's right, that's happening!

I'm doing a much of the work as I can too.

I got the RB30 block from my old VL commodore after I cooked the head in good old VL commodore fashion. :)

I've just finished tearing down the short motor and everything is pretty much bang on with factory tolerances which is awesome.

The deck needs a machine as it's slightly high in between two of the cylinders.

The head I've got is coming off my the RB25 that was in my 33 until I cooked it. it's a little melted in cylinder #1 as you might have seen in my other thread, it's also not perfectly straight, but I was thinking if I take about 0.8mm off the head it'll remove all the melted crusty shit and increase my compression ratio too. As 25\30 combinations with stock RB30 short motor and stock R33 25 VCT head will yeild about 8.2:1 Compression Ratio, saving the head that much will reduce the Combustion chamber volume by about 7cc which will increase the compression ratio up to around 9:1.

I'm not sure if I want to do that yet though, with the doughy compression ratio and a safe tune I'll be able to use the shitty fuel, down on the peninsula and other Rural areas that I frequent, safely.

I just measured my head and it was 61cc. While I was measuring it I left the water in there for an hour and found all the valves leak a little, some more than others, but they'll all need some love.

I plan to do the internal VCT mod as outlined in this thread. http://www.skylinesaustralia.com/forums/topic/251669-rb2530-rb30det-vvt-internal-oil-control/ Page 5 'The mafia' comments with some pics that breaks down the process really well. Looks easy enough :)

After reading the 25\30 thread in the forced induction section, it all looks too easy... (famous last words)

The only thing on the shopping list is an oil pump, I'm thinking stock RB25 until should do the job? If anyone has one lying around after an upgrade, let me know!

I think I'm almost at the stage where I can send stuff off to get machined! It's looking good so far :)

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zoidbergmerc Mentor

zoidbergmerc

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Pics

20121227_103310.jpg

RB30 goodness

:D

20121227_103327.jpg

Proof of concept

20121231_123324.jpg

Measuring combustion chamber and valve leak testing.

20121231_123309.jpg

After about 1 hour this is what they all looked like

20121227_104600.jpg

This piston is the only one I'm worried about, opinions? Spark plug ceramic trolled it.

zoidbergmerc Mentor

zoidbergmerc

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Posted (edited)

Extended shopping list:

Oil pump

Water Pump

Full length crank collar

Oil restrictors

New bearings

New head bolts\studs

New head gaskets.

Bottom timing belt gear.

Harmonic balancer

If anyone has this stuff lying around, let me know!

I'm also after a turbo, not decided on what I want to do yet though :/

Edited by zoidbergmerc
XRATED Veteran

XRATED

Posted
Posted

This is for the VL isn't it? Not your 33...

.8mm is chopping a fair bit out of a 25 head... I'll be interested in what Matt/insert chosen machinist has to say about it. You'll have to watch your valve clearance too. That head looked pretty fkn cooked though!

I have some slightly used wiseco rb25/30 pistons/pins/locks without rings going cheap if you wan't some :-)

If it's just a slapper, the sparkplug tip damaged piston will be okish, just smooth the divits out a little, also check the bore very carefully.

I have some 25/30 bits and bobs kicking about. I'll have a look, see what I can find.

The conversion is easy. There are a couple of things that arn't covered in the guide, sing out if you need a hand.

J.

sav man Grand Master

sav man

Posted
Posted

When you measured the head did you put clear platic + grease over the combustion chamber for an accurate measurement? 0.8 will not give you 7cc, 86mm diamiter at 0.8 height gives you 4.6cc, so it will probably be 4cc by the time you equate for the sqish zones.

I asked Rodgers to take 4cc out of Steves RB20 head (stock head is 40cc), and he wouldn't do it. He would only change the deck height on the block. He will be able to sort the piston though.

I can't see valve clearance being an issue with the design of the rb30 piston, what is the volume of the piston dish?

Use brake cleaner to test the valve seal before final reassembly, If you used it now it'd be alike a tsunami coming though.

zoidbergmerc Mentor

zoidbergmerc

Posted
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Posted (edited)

This is for the VL isn't it? Not your 33...

.8mm is chopping a fair bit out of a 25 head... I'll be interested in what Matt/insert chosen machinist has to say about it. You'll have to watch your valve clearance too. That head looked pretty fkn cooked though!

I have some slightly used wiseco rb25/30 pistons/pins/locks without rings going cheap if you wan't some :-)

If it's just a slapper, the sparkplug tip damaged piston will be okish, just smooth the divits out a little, also check the bore very carefully.

I have some 25/30 bits and bobs kicking about. I'll have a look, see what I can find.

The conversion is easy. There are a couple of things that arn't covered in the guide, sing out if you need a hand.

J.

Yeah this first one will go in the VL, assuming it's a raging success I might build another one for the 33 :)

I might take you up on that offer for extra assistance. Let me know what bits you've got, I might require them.

The bores are pretty healthy, they've got some marks where the pistons were sitting stationary for 5 years though, and that comes out rather that eating in, so I'm assuming that can be honed out, the marks came off the piston skirts with a good rub.

When you measured the head did you put clear platic + grease over the combustion chamber for an accurate measurement? 0.8 will not give you 7cc, 86mm diamiter at 0.8 height gives you 4.6cc, so it will probably be 4cc by the time you equate for the sqish zones.

I asked Rodgers to take 4cc out of Steves RB20 head (stock head is 40cc), and he wouldn't do it. He would only change the deck height on the block. He will be able to sort the piston though.

I can't see valve clearance being an issue with the design of the rb30 piston, what is the volume of the piston dish?

Use brake cleaner to test the valve seal before final reassembly, If you used it now it'd be alike a tsunami coming though.

I've got to drop some stuff off to Rogers on Wednesday so I'll spin a yarn and see what he reckons.

You're right about the cc part too, f**k knows what was wrong with my maths :P

When I did the head CCs I didn't have any grease or plastic so I just made sure it was perfectly flat and ran a ring of detergent around the lip of the combustion chamber to eliminate the meniscus.

Measuring the Piston dome trolled me a little, it took a while to figure it out, it's got a little dome and a little valve relief. I could measure the relief quite easily but to measure the dish; I made some play dough and pressed the piston into it and measured the dome like it, it wasn't the most accurate way to do it but it's all I could think of :/ By my awesome calculations, the valve relief pretty much cancels out the dome. Both 3.9cc

I'll be sure to clean up the valve seats and try it again later :) It wasn't quite a tsunami, but it wasn't pretty...

Edited by zoidbergmerc
sav man Grand Master

sav man

Posted
Posted

are the pistons domed or dished in the middle? it's hard to tell from the photo.

You'd be best just to get Rodgers to reseat the valves, it's not that expensive, and it'll save you 11ty hundred hours

zoidbergmerc Mentor

zoidbergmerc

Posted
  • Author
Posted

They're domed in the middle, and dished with the valve relief is.

I'm trying to do as much as I can in this engine build, so next time when I hand over my hard earned cash I can fully appreciate the value of the work being done.

XRATED Veteran

XRATED

Posted
Posted

Hey Nowley,

Do you have turbo/hot side allready? Do you have a loom ecu yet?

If not, why not put a single cam head back on?

With all the money/time you save, you can put a nice big cam and rocker gear in.... and be able to use the stock loom with a nistune in the VL ecu.

... just a thought

Justin.

DJRIFT Veteran

DJRIFT

Posted
Posted

There is actually a high flowed 34 turbo here....

Hmmmm.

I don't rate hifliws buy on a 3l it wouldn't be to bad. Depends what you are after. I've got exhaust manifold and turbo lines if you think you mite go that way.

zoidbergmerc Mentor

zoidbergmerc

Posted
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Posted

yeah I've still got my stock exhaust manifold and a small collection of turbo lines. So I should be right. I'll keep it in mind though :)

I was also eyeing off that GT3540 for sale in the other thread, will that fit in stock low mount position?

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