Jump to content
SAU Community

Recommended Posts

Hey Folks,

I was wondering if one of the hotshot engine builders on here would give me some advice. Im in the process of doing my very first full/ground up engine build and im having some issues with oil clearances. I am using plastigague as a measuring tool and I want to double check im doing it correctly. The plastigauge "splat" matched up to the card between 0.050mm and the 0.038mm marks giving me an estimated clearance of around 0.046mm (ish) do i then divide that figure by 2 to give me the actual clearance of 0.023mm? IE: Bang on the Nissan spec of 0.022-0.046 mm??

Or is my actual clearance 0.046 (ie: on the very limit of the OEM specs)

I think im right that the plastigauge figure has to be divided by two to account for the two oil surfaces (one on each side of the crank) but i just want to be 100% sure.

I measured the BE bearing and that came out at dead on 0.050mm which if i divided it by 2 would be bang on spec, but if it's not then i think im way out.

The engine is an R32 RB26DETT with a brand new ACL standard size bearings. Crank has been polished and nothing else.

Cheers

Chris

Edited by Guishnu
Link to comment
https://www.sau.com.au/forums/topic/309592-rb26dett-oil-clearance-question/
Share on other sites

If your engine is upside down the crank is fully rested against the bearing material on the low side so your measuring the clearance on the high side (sum of both clearances) no need to divide by 2.

That said i no longer (since i was an apprentice) use plastigage as it is not precise enough, it will often read tighter than it actually is giving you a loose engine. A mic is the only way to go TBH

see stolen interwebs picture.

post-34927-1267055244_thumb.jpg

mic first...plasti second.

yep thats right...i measure twice...using each method.

I know of an engine that failed very recently that would have been saved if the builder used this method, as the plastigage would have picked up the huge error in his micrometer.

its just a good double check of the micrometer measurements and its not as inaccurate as one may think if used correctly.

mic first...plasti second.

yep thats right...i measure twice...using each method.

I know of an engine that failed very recently that would have been saved if the builder used this method, as the plastigage would have picked up the huge error in his micrometer.

its just a good double check of the micrometer measurements and its not as inaccurate as one may think if used correctly.

Not disagreeing with you here Paul, and anything that works for you has gotta be a good thing as you build a mean engine.

The example you provided with the micrometer having an error? If measured properly and the micrometer calibrated correctly and the engineer all doing their job correctly, any error in a micrometer can be picked up without needing plasti gauge to back it up.

If you use the same micrometer for the journal measurement as you do for the tunnel measurement, the micrometer doesn't even have to be accurate, it just has to be consistent.

Not disagreeing with you here Paul, and anything that works for you has gotta be a good thing as you build a mean engine.

The example you provided with the micrometer having an error? If measured properly and the micrometer calibrated correctly and the engineer all doing their job correctly, any error in a micrometer can be picked up without needing plasti gauge to back it up.

If you use the same micrometer for the journal measurement as you do for the tunnel measurement, the micrometer doesn't even have to be accurate, it just has to be consistent.

Using just plastigage and nothing else is folly in the extreme...i understand exactly what you were saying and also what you have just said above. Im assuming the tunnels and the journals must have been measured on different equipment or even different days? It didn't sound right to me but that was the excuse he provided to the customer.

A quick check of mic. calibration with the setting bars is also a good idea each time it is pulled out of the case as well.

the engine in question had a huge knock on startup...big mistake that could have been easily picked up.

Edited by DiRTgarage
mic first...plasti second.

yep thats right...i measure twice...using each method.

I know of an engine that failed very recently that would have been saved if the builder used this method, as the plastigage would have picked up the huge error in his micrometer.

its just a good double check of the micrometer measurements and its not as inaccurate as one may think if used correctly.

Not a bad comparo, some one pm'd it to me today (mirrored what i was saying earlier)

http://www.carcraft.com/techfaq/116_0701_p...eter/index.html

I'll pull out the crank, clean, replace and re-check the measurements.

If the big end clearances are too big, can i get a few thou machined off the cap face to tighten them up? Same with the main bearing gurdle?

I'll pull out the crank, clean, replace and re-check the measurements.

If the big end clearances are too big, can i get a few thou machined off the cap face to tighten them up? Same with the main bearing gurdle?

Lol

Never mind - I know milling the caps isn't possible.

I’m even more retarded then usual (but it's always good to make 110% sure!)

Oil Clearances

Mains

OEM Standard Bearings 0.028mm ~ 0.046mm / 0.0011” ~ 0.0018” with a limit of 0.090mm/0.0035”

Big Ends

OEM Standard Bearings 0.020mm ~ 0.039mm / 0.0007” ~ 0.0015” with a limit of 0.090mm/0.0035”

My mains are running 0.046mm/0.0018” (aprox)

My big ends are running 0.050mm/0.0020” (aprox)

So I’m golden.

Few.

Edited by Guishnu

Any comments. Machining your crank, Measuring up your bearings to your exact chosen spec's, after then, bolting on your sump, then bolting on the head with let's say with a multi layered steel shimmed head gasket. Any changers to your bearing measurement's after this process?

  • 2 months later...
Thread revival!

Where in the bearing tunnel is the best spot to measure for clearance?

Should the caps be torqued up with out the crank inplace or...?

put in your bearings, then mains caps, girdle and bolts that you will use (torques down). measure each main tunnel. U can measure at different spots on each tunnel. at say 12 and 6, 2 and 8, 4 and 10 o'clock etc.then measure up each journal of the crank. If the clearances are too big then you can get the caps machined down and the block line bored again to a size that is more appropriate.

Edited by GTR1993

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

    • Hey Dave, welcome aboard! Good to see another soon-to-be Stagea owner here. The wagons are awesome — plenty of space, still got that Skyline DNA, and loads of potential if you’re into mods. Definitely post up pics when you get it, everyone here loves seeing new builds. What model/year are you looking at?
    • See if you can thermal epoxy a heatsink or two onto it?
    • The other problem was one of those "oh shit we are going to die moments". Basically the high spec Q50s have a full electric steering rack, and the povo ones had a regular hydraulic rack with an electric pump.  So couple of laps into session 5 as I came into turn 2 (big run off now, happily), the dash turned into a christmas tree and the steering became super heavy and I went well off. I assumed it was a tyre failure so limped to the pits, but everything was OK. But....the master warning light was still on so I checked the DTCs and saw – C13E6 “Heat Protection”. Yes, that bloody steering rack computer sitting where the oil cooler should be has its own sensors and error logic, and decided I was using the steering wheel too much. I really appreciated the helpful information in the manual (my bold) POSSIBLE CAUSE • Continuing the overloading steering (Sports driving in the circuit etc,) “DATA MONITOR” >> “C/M TEMPERATURE”. The rise of steering force motor internal temperature caused the protection function to operate. This is not a system malfunction. INSPECTION END So, basically the electric motor in the steering rack got to 150c, and it decided to shut down without warning for my safety. Didn't feel safe. Short term I'll see if I can duct some air to that motor (the engine bay is sealed pretty tight). Long term, depending on how often this happens, I'll look into swapping the povo spec electric/hydraulic rack in. While the rack should be fine the power supply to the pump will be a pain and might be best to deal with it when I add a PDM.
    • And finally, 2 problems I really need to sort.  Firstly as Matt said the auto trans is not happy as it gets hot - I couldn't log the temps but the gauge showed 90o. On the first day I took it out back in Feb, because the coolant was getting hot I never got to any auto trans issues; but on this day by late session 3 and then really clearly in 4 and 5 as it got hotter it just would not shift up. You can hear the issue really clearly at 12:55 and 16:20 on the vid. So the good news is, literally this week Ecutek finally released tuning for the jatco 7 speed. I'll have a chat to Racebox and see what they can do electrically to keep it cooler and to get the gears, if anything. That will likely take some R&D and can only really happen on track as it never gets even warm with road use. I've also picked up some eye wateringly expensive Redline D6 ATF to try, it had the highest viscosity I could find at 100o so we will see if that helps (just waiting for some oil pan gaskets so I can change it properly). If neither of those work I need to remove the coolant/trans interwarmer and the radiator cooler and go to an external cooler....somewhere.....(goodbye washer reservoir?), and if that fails give up on this mad idea and wait for Nissan to release the manual 400R
    • So, what else.... Power. I don't know what it is making because I haven't done a post tune dyno run yet; I will when I get a chance. It was 240rwkw dead stock. Conclusion from the day....it does not need a single kw more until I sort some other stuff. It comes on so hard that I could hear the twin N1 turbos on the R32 crying, and I just can't use what it has around a tight track with the current setup. Brakes. They are perfect. Hit them hard all day and they never felt like having an issue; you can see in the video we were making ground on much lighter cars on better tyres under brakes. They are standard (red sport) calipers, standard size discs in DBA5000 2 piece, Winmax pads and Motul RBF600 fluid, all from Matty at Racebrakes Sydney. Keeping in mind the car is more powerful than my R32 and weighs 1780, he clearly knows his shit. Suspension. This is one of the first areas I need to change. It has electronically controlled dampers from factory, but everything is just way too soft for track work even on the hardest setting (it is nice when hustling on country roads though). In particular it rolls into oversteer mid corner and pitches too much under hard braking so it becomes unstable eg in the turn 1 kink I need to brake early, turn through the kink then brake again so I don't pirouette like an AE86. I need to get some decent shocks with matched springs and sway bars ASAP, even if it is just a v1 setup until I work out a proper race/rally setup later. Tyres. I am running Yoko A052 in 235/45/18 all round, because that was what I could get in approximately the right height on wheels I had in the shed (Rays/Nismo 18x8 off the old Leaf actually!). As track tyres they are pretty poor; I note GTSBoy recently posted a porker comparo video including them where they were about the same as AD09.....that is nothing like a top line track tyre. I'll start getting that sorted but realistically I should get proper sized wheels first (likely 9.5 +38 front and 11 +55 at the rear, so a custom order, and I can't rotate them like the R32), then work out what the best tyre option is. BTW on that, Targa Tas had gone to road tyres instead of semi slicks now so that is a whole other world of choices to sort. Diff. This is the other thing that urgently needs to be addressed. It left massive 1s out of the fish hook all day, even when I was trying not too (you can also hear it reving on the video, and see the RPM rising too fast compared to speed in the data). It has an open diff that Infiniti optimistically called a B-LSD for "Brake Limited Slip Diff". It does good straight line standing start 11s but it is woeful on the track. Nismo seem to make a 2 way for it.
×
×
  • Create New...