Jump to content
SAU Community

Recommended Posts

Guys, VG30DETT rods are 2mm longer than the RB30 rods. And the RB25DET pistons have the shorter compression height, if I use both of these should give the correct height depending on combustion chamber volumes.

Does this sound like a viable option?

Probably firstly depends on the crank journal sizes - how much difference is there between the VG and RB rods? You'd need things side by side to measure up, and maybe look at a dummy assembly if you can get the bits at low cost.

Alternatively, why not look at just using RB25 pistons and deck the block by the required amount? Sure you might be retaining cast pistons and stock RB30 rods, but gets the result you want.

There should be a number of viable ways to achieve a similar outcome. It takes $$ to put in the parts that make for a stout 30DET, but the lower spec pistons and rods would still make for a good street build IMO.

Given the options, I'd rather install a longer rod (from an engine that was factory turbo) opposed to decking the block to compensate for the lower height pistons. Also, I'm aiming to get a comp ratio approx 9:1 so I think there would be a fair bit of block decking to reach that with just the 25DET pistons, apparently the galleries start widening once you take off 2mm off the block.

From what I've read the VG30 rods fit in the RB30 block/crank, might need to organise something different for the gudeon pins/bearings depending on the piston used.

But this all depends on combustion chamber volume, if the block and/or head need shaving to ensure it's true, from the rough calcs I did, the VG30 rods and RB25 pistons could result in compression ratios over 10:1, in which case I may need to use RB26 pistons (lower compression height again). Also, another thing I need to factor is if the block is worn and needs boring out I'll need overbore pistons, which may prove difficult to find 2nd hand.

Basically, I see it the similar as using factory RB30 rods and pistons, instead the rod happens to be longer and the piston a bit shorter. The parts are going to be balanced and new bearings etc installed either way and the VG30/RB25 parts can be obtained relatively easily and cheap.

Just want to know if it's stupid idea in theory.

Edited by daisu
7. SPOOL RB30 conrods and CP Forged Pistons $2050
Direct from their page

As opposed to picking up a set of VG30 rods/pistons for about $100 and haven't looked at RB25 piston prices but I'm assuming they would be similar priced.

Considering alot of people are making good power figures using standard bottom ends in both RB30's, VG30's, and RB25's I don't see the need to upgrade to aftermarket pistons/rods.

Direct from their page

As opposed to picking up a set of VG30 rods/pistons for about $100 and haven't looked at RB25 piston prices but I'm assuming they would be similar priced.

Considering alot of people are making good power figures using standard bottom ends in both RB30's, VG30's, and RB25's I don't see the need to upgrade to aftermarket pistons/rods.

I can tell you for a fact that vg30 rods fit. thats what im using. However i got custom JE pistons made to suit and eagle rods. VG30 rods are 154mm (6.070in) and rb30 are 6in or 152.5mm thereabouts. so vg30 are 2.5mm longer, i havnt bothered trying to find out if they work with std. pistons etc. VG30 DOHC rods from 300zx etc have a 22mm rod bush, SOHC use a 21mm rod bush, same as all RB engines, so to start with youd need SOHC 300zx rods from something like a maxima. both VG rods use the same bottom end as RB so use the same bearings, even the acl website use the same partnumber

vg30 rods are about 1.5mm to 2mm thinner across the rod ( thickness ) than RB30 rods - so when using VG30 rods you end up with a rod that slides back and fourth on the big end journal.

I can tell you for a fact that vg30 rods fit. thats what im using. However i got custom JE pistons made to suit and eagle rods. VG30 rods are 154mm (6.070in) and rb30 are 6in or 152.5mm thereabouts. so vg30 are 2.5mm longer, i havnt bothered trying to find out if they work with std. pistons etc. VG30 DOHC rods from 300zx etc have a 22mm rod bush, SOHC use a 21mm rod bush, same as all RB engines, so to start with youd need SOHC 300zx rods from something like a maxima. both VG rods use the same bottom end as RB so use the same bearings, even the acl website use the same partnumber
I can tell you for a fact that vg30 rods fit. thats what im using. However i got custom JE pistons made to suit and eagle rods. VG30 rods are 154mm (6.070in) and rb30 are 6in or 152.5mm thereabouts. so vg30 are 2.5mm longer, i havnt bothered trying to find out if they work with std. pistons etc. VG30 DOHC rods from 300zx etc have a 22mm rod bush, SOHC use a 21mm rod bush, same as all RB engines, so to start with youd need SOHC 300zx rods from something like a maxima. both VG rods use the same bottom end as RB so use the same bearings, even the acl website use the same partnumber

Ah yes, I saw those pistons you had for sale on trademe.nz, question for you, with the pistons you had and using the VG30 rods you said it would give approx 8.3:1 compression ratio. Can I ask what was the compression height of the piston and whether how many CC's if it was dome top or dished?

If the VG30E(T) rods have the correct bush size then this would be easier than machining pistons to suit 22mm pin or having bushes made to suit 21mm pin. Only problem is knowing how strong/reliable they are. The factory power output of the engine is very similar to the ratings of the RB30. We'll see if I can find some people pushing decent power through these engines on standard bottom ends.

K577M87 - NISSAN RB30 GTR DISH 6577M87 - $852.12 That's US dollars without shipping.

And I'm not making anywhere near 530kW. I really don't see the need to use aftermarket pistons in my application.

The rods being thinner could be a problem though.

K577M87 Wiseco Pistons Rb30 GTR, Used by UK owners and proven to work

$648.84 USD from No limit motorsport be around $120 usd ship

$770 USD delivered + Spool rods $750 AUD= saves u around $500?

since they sell CP pistons + rods for 2k

vg30 rods are about 1.5mm to 2mm thinner across the rod ( thickness ) than RB30 rods - so when using VG30 rods you end up with a rod that slides back and fourth on the big end journal.

'Spoolup', do you know how this issue is overcome on the VG30 engines by any chance?

yes that is exactly corret - on the VG30 there are two rods per journal ( being a V6 ).

So the width of the journal is just different to the RB30 and that is why the VG30 is different

i dont no for sure but i would presume that the crank is just sized/designed differently to accomodate the thinner rod.

for your power - just run a set of std RB30 rods and NA RB30 pistons - they will handle it and obviously a direct fit with no issues.

$1500 is still much more than I want to pay when standard items have been proven more than capable in the power range I'm aiming for.
Edited by Spoolup

this may be a stupid question for sum, but do you get your block work done and then purchase your pistons and bearings so forth or do you just get over sized pistons and then got the block done to match. or does it not really matter what way you do it

Yeah, I was contemplating just using standard rod/pistons, but as said before I want higher comp.

I guess I should start by CC'ing the head and having the block checked first. No point in figuring out I can use X pistons only to find out the block needs to be bored out and the pistons won't fit anymore.

I'll just have to go with decked block/shaved head and thin head gasket.

I would assume you'd have the block inspected first and then decide if oversize pistons are needed. Or if you had already planned on oversize pistons I guess it wouldn't matter which way you did it.

Clarification please?

Edited by daisu

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

    • Thanks for that, I'll check it all out. I can always do the brakes last anyway if its a problem.  The 16's are super cool, if they do fit I'll cruise around with them for a bit.  
    • Well, that's kinda the point. The calipers might interfere with the inside of the barrels 16" rims are only about 14" inside the barrels, which is ~350mm, and 334mm rotors only leave about 8mm outboard for the caliper before you get to 350, And.... that;s not gunna be enough. If the rims have a larger ID than that, you might sneak it in. I'd be putting a measuring stick inside the wheel and eyeballing the extra required for the caliper outboard of the rotor before committing to bolting it all on.
    • OK, so again it has been a bit of a break but it was around researching what had been done since I didn't have access to Neil's records and not everything is obvious without pulling stuff apart. Happily the guy who assembled the engine had kept reasonable records, so we now know the final spec is: Bottom end: Standard block and crank Ross 86.5mm forgies, 9:1 compression Spool forged rods Standard main bolts Oil pump Spool billet gears in standard housing Aeroflow extended and baffled sump Head Freshly rebuilt standard head with new 80lb valve springs Mild porting/port match Head oil feed restrictor VCT disabled Tighe 805C reground cams (255 duration, 8.93 lift)  Adjustable cam gears on inlet/exhaust Standard head bolts, gasket not confirmed but assumed MLS External 555cc Nismo injectors Z32 AFM Bosch 023 Intank fuel pump Garret 2871 (factory housings and manifold) Hypertune FFP plenum with standard throttle   Time to book in a trip to Unigroup
    • I forgot about my shiny new plates!
    • Well, apparently they do fit, however this wont be a problem if not because the car will be stationary while i do the suspension work. I was just going to use the 16's to roll the old girl around if I needed to. I just need to get the E90 back on the road first. Yes! I'm a believer! 🙌 So, I contacted them because the site kinda sucks and I was really confused about what I'd need. They put together a package for me and because I was spraying all the seat surfaces and not doing spot fixes I decided not to send them a headrest to colour match, I just used their colour on file (and it was spot on).  I got some heavy duty cleaner, 1L of colour, a small bottle of dye hardener and a small bottle of the dye top coat. I also got a spray gun as I needed a larger nozzle than the gun I had and it was only $40 extra. From memory the total was ~$450 ish. Its not cheap but the result is awesome. They did add repair bits and pieces to the quote originally and the cost came down significantly when I said I didn't need any repair products. I did it over a weekend. The only issues I had were my own; I forgot to mix the hardener into the dye two coats but I had enough dye for 2 more coats with the hardener. I also just used up all the dye because why not and i rushed the last coat which gave me some runs. Thankfully the runs are under the headrests. The gun pattern wasn't great, very round and would have been better if it was a line. It made it a little tricky to get consistent coverage and I think having done the extra coats probably helped conceal any coverage issues. I contacted them again a few months later so I could get our X5 done (who the f**k thought white leather was a good idea for a family car?!) and they said they had some training to do in Sydney and I could get a reduced rate on the leather fix in the X5 if I let them demo their product on our car. So I agreed. When I took Bec in the E39 to pick it up, I showed them the job I'd done in my car and they were all (students included) really impressed. Note that they said the runs I created could be fixed easily at the time with a brush or an air compressor gun. So, now with the two cars done I can absolutely recommend Colourlock.  I'll take pics of both interiors and create a new thread.
×
×
  • Create New...