Rb25 reliability upgrades. Rb gurus help me!!

Hi, i am building my rb25 with forged pistons and rods and i am aiming for 600hp.

My question is regarding the reliability of oil isseus of the rb engine and what upgrades i need to defenility do to avoid problems in the future for what i am using the engine for.

The engine is gonna be used primarly on the street and a occasional trackday like nurburgring

What is your experience and are there any real rb gurus here.

Thanks in advance

The main problems with the oil system in the RB engines include the weak oil pump, too much oil flow into the head, and insufficient or poor return of oil into the sump. This thread covers these problems and fixes thoroughly so I'd suggest you read the first few pages: http://www.skylinesaustralia.com/forums/topic/110680-oil-control-in-rbs-for-circuit-drag-or-drift/page__hl__sk+oil+control

Thanks for responding andre, but wont al these mods restricting the flow to the cylinder head cause isseus if i were to use the engine at low rpm for a long period of time that there isnt enough oil in the cylinder head.

And would you recommend a different oilpump or could i stick to the oem pump without isseus??

The amount of oil required in the cylinder head isn't actually that great and the problem with the engine is that the oil doesn't return from the head particularly well. The loading on the cam journals is nothing like the crankshaft journals and it's been well tested and proven that restrictors in the RB blocks are effective and reliable. The stock pump is problematic at high rpm as they are known to break so the decision on the pump comes down to what rpm range you intend to use. I haven't built any RB25's myself but plenty of RB26's. The stock pump fails at about 8000 rpm and then there is the drive issues on the early cranks that can also be a problem.

I have oil restrictors to the head, enlarged oil returns and drain back from the rear of the head. I've never had any issues at low rpm and mt car is mainly a road car. The oil will still be receiving plenty of oil even at idle. I also have breather plate baffles and have never had an issue with my catch can filing up.

I use an N1 pump (long nose crank also) and have had no problems but I make sure not to bash the limiter, if I ever rebuild I'd be tempted to convert to a spline drive setup.

If you get your oil system well setup (dry sump if you can budget) you've solved a lot of issues, they also make a lot of heat so you want to make sure your cooling system is up to scratch.

figured it al out with the oil restrictions except 1 thing, cant find a defenite answer on what size to drill the oil returns in the block and head, mine are stock 8mm and the headgasket hole is 12mm, should i drill in between 10mm or go as big as possible 12mm??

i am ordering parts now and wondering if i need new crankshaft main bolts. the bolts look in really good condition and the torque spec is only 50NM ,i have heard if i would take arp studs the crankshaft journals need machining because they get misaligned. what would you recommend doing?

I haven't drilled the block myself as I've had this done by the machinist during the machining process. Sadly I can't say for certain what size they have gone to but they seem to be a good match for the gasket after modification. From memory there's nothing in the area that you'd risk drilling through if you went to 12mm.

The stock bolts for the mains aren't TTY so they are reusable. I personally use an ARP main stud kit on pretty much any build as a matter of course but it's not strictly necessary on lower power applications. I'd say for a 600 hp build you should be fine. The ARP studs can distort the main bearing tunnel and you'd definitely want to check this but in my experience problems with distortion are more prevalent on alloy blocks.

Haha i like how these days 600hp is a low power application.

Haha it is a sign of the times. 600 hp however is a nice target for an engine that's still going to be streetable and offer nice road manners along with good reliability.