Rb25/30 Na High Comp Build Up

[GTS4WD]

I few people have.

From what I remeber reading;

The RB30 geodgen pin sits closer to the face of the piston than the RB25 piston. So the CR is higher. But if going to make a half decent rb25/30 NA build.. your going to build an engine with higer CR than just 10.5:1.

Im looking at 12:1

[dondesoto]

Is anyone doing the RB25/30 N/A Conversion with RB25DE N/A pistons, remembering hearing about this fellow with a 240z who used,

RB30E block, crank and rods, RB25DE N/A pistons and decked the block to get about 10.5:1 compression ratio - using the pistons to get a higher compression ratio as opposed to shaving 2mm of the head would be a better idea wouldnt it?

Has anyone gone down the RB25DE N/A piston route when building there RB25/30 N/A motor?

Yes i built the rb25/30 , that i sold to Skit . I used the stock rb25de pistons on the rb30e rods . Edge of pistons were sitting 1.2 mm below top edge of block , that was supposed to be good for 10.5 -1 compression , but i have recalculated that because head gasket thickness wasnt allowed for before . Also the rb25de pistons sit above the edge of the block , i measured .5 mm , just as well the head gasket is around 1 mm thick . So i figure the compression to be around 9.8-1

I,m now building another rb25/30 , again using rb25de pistons on the rb30e rods . This time the block is being decked 1.2 mm to bring edge of pistons flush with top of block at tdc . I dont want the pistons sitting above the deck like they do in rb25de . i calculate the compression to be 11.0-1 with this set up .

[Tony1981]

Yes i built the rb25/30 , that i sold to Skit . I used the stock rb25de pistons on the rb30e rods . Edge of pistons were sitting 1.2 mm below top edge of block , that was supposed to be good for 10.5 -1 compression , but i have recalculated that because head gasket thickness wasnt allowed for before . Also the rb25de pistons sit above the edge of the block , i measured .5 mm , just as well the head gasket is around 1 mm thick . So i figure the compression to be around 9.8-1

I,m now building another rb25/30 , again using rb25de pistons on the rb30e rods . This time the block is being decked 1.2 mm to bring edge of pistons flush with top of block at tdc . I dont want the pistons sitting above the deck like they do in rb25de . i calculate the compression to be 11.0-1 with this set up .

When you say deck the block to bring the edge of the pistons flush with the top of the block, probably a dumb question, but your meaning the top of the dome of the piston right?

I have just pulled the head of my RB25DE motor, its an R33 with the VCT, which I am going to keep using - I have a really decent complete RB30E motor and 2 other RB30E engines kicking around, thinking I will pull apart one of the other RB30E engines and rebuilt it, both appear to have good bores still meauring 86mm, was thinking of the following, advice is greatly appreciated!!!

Re-using the RB25DE Belt tensioner, RB25DE pistons and Oil Pump from the RB25DE engine, get a new set of ACL piston rings, ACL bearings and use RB30E head gasket and new RB25DE head bolts (both will be just Genuine Nissan), Gates version of the Dayco 94407 belt, or just grab one from Justjap (I assume its the same belt),

New waterpump and thermostat, once again genuine Nissan (Since I slapped a turbo on the side of my RB30E engine I have had a bastard of a time keeping the engine cool) - no more Repco Triton brand for me!!!

As for the RB30 Block,

Dip it, hone the bores, new welsh plugs and drill a nice new hole above the water pump for the 2nd timing belt tensioner, also deck the block - I will follow your example dondesoto, just do a dummy install so I dont get to much taken off :-),

Put a collar on the RB30E crank for the RB25DE oil pump,

Mate is drilling a hole just below the VCT solenoid on the RB25DE head and getting me the plumbing required to T-Piece some oil from the oil pressure sender unit,

Make up an extension for the Timing cover,

Then get some high temp gasket goo for my rear mounted sump,

Cant get adjustable cam gear for the intake side because of the VCT, but will grab adjustable gear for the exhaust side - any recommendations???

Only thing I am not really sure about is the Rods - I will be keeping the stock ones for sure, but not to sure what sort of treatment I should give them???

Am I missing anything???

[Cubes]

Leave the rods stock. If your going to spend any more on them its a waste of $$ as by the time you prep them, resize them and buy decent bolts you may as well have bought a set of spoolimport rods for $750 that come with ARP rod bolts.

Even considering the price of $750 by the time you buy decent rod bolts and resize the std rods your not all that far away from $750.

http://www.spoolimports.com/content/SPOOLRB30CONRODS.asp

As for adj cam gears. Spoolimports you really can't go wrong.

[frogstomp_R31]

std preped rds like balanced and shot peened resized etc .. all help longjeverty.

i have 2530det using std preped rds making 330+rwkw..... boostworks have made over 471rwkw on std rods so

they are strong for they application in your na build

[dondesoto]

When you say deck the block to bring the edge of the pistons flush with the top of the block, probably a dumb question, but your meaning the top of the dome of the piston right?

Nup . I mean the outside edge of the piston , all of the dome is above the top of the block .

Everything else you got pretty right . The 1st engine I didnt do anything to the rods , this time I,m getting rods crank and pistons balanced . As you will probly make less than 200 rwkw , the standard rods are plenty good enough .

[Tony1981]

Your going to be making more than 200rwk with an N/A 3L motor???

[Cubes]

std preped rds like balanced and shot peened resized etc .. all help longjeverty.

i have 2530det using std preped rds making 330+rwkw..... boostworks have made over 471rwkw on std rods so

they are strong for they application in your na build

Thats correct. The rods hold an almost infinite amount of power.

The issue is by the time you spend $$ on prepping and resizing the rods + a set of good rod bolts you are damn close to the $$ figure of a set of forged rods that come with ARP bolts.

So why would one bother with the stock items especially in an N/A application.

N/A will NEED the higher rev's if you want to make decent numbers so it will make use of a set of forged rods more so than the a turbo motor. Unless the turbo's pushing HUGE 500rwkw+ numbers.

Stock rods HATE rev's. Darrens 471rwkw std rb30et @ Boostworx was rev limited to 7000rpm.

Push the motor much past 7000rpm and you will run in to problems if you don't run with forged rods.

Don't look at it from a power perspective.. Look at it from a rev's perspective.

[GTS4WD]

I dont think the issue here is the strength of the standard rods.. I think its an issue of how hard your revving the engine. Standard RB30 will start to go south over 7000RPM.

If your looking at making a solid NA with cams, port and polish that will rev past 7K, id be looking into getting them shot peened.

ARP rod bolts and balance I would consider almost a must if your seeing 7K or more, simply for peice of mind as it is an engine with most likely well over 150,000km on it and 20 years old. RB30's wern't designed to see 7K. At such a higher RPM you dont want to throw a rod out. Balance is another $70 - $100 well spent.

Think about new rings too. Chances are that an engine of its age has seen better days. The last thing you want is to build a new engine and then have a ring shit itself. $80 well invested.

[Tony1981]

Yeah going to get new rings, new bearings, new head gasket, new head bolts, new waterpump, new thermostat, pretty much everything will be new except the pistons, rods and crank,

With a set of forged rods or getting the stock ones shot peened, how far can the RB30 rev? how far past 7000rpm??? If I spent $750 on a set of rods and bolts for an N/A application I would want to be able to rev its a@s off all day everyday :-)!!!

How do the stock RB25DE pistons hold up to this sort of power? I was thinking of using the set out of the RB25DE motor I grabbed the head off,

[Cubes]

Regardless what you have done to the stock rods I still wouldn't push them much past 7000rpm.

Forged pistons reduce weight hanging off the end of the road so a motor with forged pistons will be able to handle a few more rev's than one that runs the std cast.

The rb30 with a full length crank collar, good balancer, forged rods and pistons take them to 8.5k.

[GTS4WD]

New forged RB30 Rods - $750

Rb25/30 Fogies $1200

Simply not worth it for an NA with less than 200kw.

RB25 pistons are a better option in all ways for the build

How far does it rev? well depends what mods you want. what cam profile you have. How heavy your port is etc. but it is possible to rev past 7K

Im thinking shot peen and balance is fine for a mild NA build

[Tony1981]

Well with that sort of expense can build one to suit a turbo and aim for 400rwkw, my little 260z would have a heart attack with that much power in it, but yeah was thinking forged rods and pistons for an N/A build wouldnt really be worth the expense :-),

How much does shot peening cost? just approximate prices,

Just reading through some older posts and I think it was you, who got a quote of $80 for a crank collar to use the RB25 oil pump? - I was quoted $150 by a local engine builder - just want to have a rough idea about what is an appropriate cost for shot peening my conrods,

Ages ago I bought an RB30 twin throttle bodied manifold where someone had basically slapped two RB30E throttle bodies onto the stock manifold - cut out the entire front, welded on a new front piece, welded on two flanges to mount the TB's and connected them via a rod - so when you open one throttle, both open at the same time and same rate - is this what you fellows are doing with the 150-200rwkw RB30DE engines or are you still running the stock manifold and throttle bodies???

Edited July 8, 2008 by Tony1981

[GTS4WD]

Im not going to lie and say I know how much shot peening is.. becasue I dont.. I bought my rods already peened.

Yeah.. I got a quote for that from somewhere in syd. But if you have a metal work lathe it will cost you all of $2

But bear in mind you dont need new rods and pistons for a good NA engine

[Tony1981]

Isnt shot peening a process basically sand-blasting the rods with plastic instead of sand?

Apparently there isnt anyone who can actually do it in Canberra anyways :-),

Got some prices and I think I will not bother with the shot peening, dosent seem like it is worth the expense,

For $280 - get the block decked 1-1.2mm (as much as it is required to get the pistons flush), chemical clean, new welsh plugs, hone the bores and drill a tap a 2nd hole for the 2nd belt tensioner,

$280 - for balancing the crank, rods, pistons, balancer and flywheel/clutch,

Then re-use the RB25DE pistons, RB30E rods and crank with new ACL bearings, Pistons rings,

[GTS4WD]

Rod bolts?.. keep the old ones?

[Tony1981]

Actually got a quote of only $210 for a set of ARP ones today - that sounds cheap :-), pretty funny the retail prices in Canberra sometimes, almost amazing really :-),

I was probably just going to go with geniune RB30E items, or is that being just a little bit to cheap?

[GTS4WD]

I either got an awesome deal or that is waaaayyy too steep..

http://www.arp-bolts.com/Images/Aus-NZ_Distributors.pdf

Call ARP and double cheak your not getting your pants pulled down over the price

[CeJay]

How is the build going? Wouldn't mind having a look at your car and finding some info out about your issues with the rb30, will probably be up for the putty cruise in october.

[GTS4WD]

How is the build going? Wouldn't mind having a look at your car and finding some info out about your issues with the rb30, will probably be up for the putty cruise in october.

Well mate.. at the moment im trying to sort out a cheaper version of an adaptor plate for the front diff and block.. $500 is just rediculous..