Forum » General Engine Building Discussion » Rb25det measurements and clearances

Rb25det measurements and clearances

General Engine Building Discussion

Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.

Page 1

Hi guys im building a rb25det at the moment. Im using wossner pistons. I plan to run a precision 6062 turbo. Car will be used for drifting. I have attached a sheet showing the measurements i took from the engine. You will notice some are in mm and some in inches. Also the 0.02mm i have added to piston clearance was for coating. I had to use plastigauge for big end clearance as bore gauge wouldnt fit. Please give me some feedback as to what you think.

Attached Files

Hi Joseph, it looks like your clearances are mostly in line with what I'd use on an RB25. I generally aim for a touch tighter on the mains, where as you're at the high end of what I'd use. As a guide I normally want to be around 0.002" on the big ends and 0.0025" on the mains. As for the pistons I can't really comment as it's not a brand I'm familiar with and I don't know the specific alloy they're using. The spec sheet should tell you what their recommended piston to bore clearance is and I'd go with that unless there's a good reason not to.

Cheers for the feedback Andre. Would have liked ever so slightly tighter on the mains but i will be running quite a heavy viscosity fully synthetic oil and looking alot of hp over standard engine. Ive added a few photos of the engine build so far. You will see the 36-1 trigger wheel and sensor bracket setup i plan to run off the crank pulley to give a good reading at high revs, the bracket also allows the addition of an external oil pump if i decide to go that route in the future. What would your thoughts be on running a standard fuel pump to a little tank in the engine bay then a mechanical pump from it to the rail?

Attached Files

You may find that if your fuel usage is high (which I'm gathering it is likely to be) then the factory pump won't be enough to keep the engine bay tank full. The lift pump in this situation needs to be able to support the entire fuel flow for the engine. While it will be working against low pressure which will improve flow, a standard fuel pump is likely ot fall short here. Otherwise though the plan is solid and pretty common.

I'd also just note that when you're machining a missing tooth trigger wheel for a reluctor sensor, it can be a good idea to machine the missing tooth at half height instead of the full depth of the tooth. With a full depth missing tooth, often this creates a strange signal on the tooth after the gap and the signal may not fall back through zero so the ECU essentially misses it. Doesn't always happen but it's caught me out a couple of times. Only tends to happen at high rpm.

Cheers for the advice i will upgrade my in tank pump. Will be using a hall effect sensor so hopefully should be ok.

Decided to upgrade the head to solid single piece lifters and running a 256 intake cam retaining the vct and a 264 exhaust with adjustable pulley. Was suprised how much dirt i extracted from the head stud threads in the block even after the block got quite a clean. I Attached a few photos

Attached Files

It's not uncommon to see that level of debris come out of the head stud holes when you run a tap through them.

Bit more progress

Attached Files

Looking great!

Cheers andre! What are the thoughts on the gated, winged sump guys? Anything i could do to improve it? Pickup has been extended down to suit also.

Attached Files

Looks like it should do the job. I'd recommend adding an oil pressure sensor so you can keep an eye on how it's performing.