New Crank, New Block , Acl Hx Series Bearings 0.063Mm

[ZimNismoBoy]

Sorry for the stupid post but just confirming, i have just done a plastigauge on my new assembly using Acl race series bearings HX type with extra oil clearance.

I have dont some measuring with dry bearings, and got roughly 0.063mm across the board + or - a little on some bearings but all are falling slightly less then 0.063mm on mains.

I am going to be reving the engine hard to 8400rpm occasionally .

I wanted to know if this is a ok bearing clearance using a tomei pump and uprated baffled sump running 8 litres of oil.

I know most run 0.050mm for a hard reving motor, but just wanted to confirm is this is ok on a new build ?

If i go for acl series standard bearings the clearance will for 1" of a inch less so around 0.045mm

What do you recommend and what are your thoughts on this ?

Cheers for the help in advance, ps i will message any one that has asked about the 1280 usd block from states soon, just need to dig up details as i have changed computers.

My apologies.

[rob82]

I wouldn't have a problem with that bearing clearance with that pump. I know of build's with greater clearance with similar rev limits without issues.

[abr33]

That works out at 2.5 thou basically, thats exactly what i run in my 25 running a tomei pump, ill be pulling similar revs once tuned. Be sure to run a thick oil. I run redline 15w/50

BTW mine was blueprinted, id suggest that for big output

[The Dan]

The number is fine but the clearance doesn't look right for what you would expect from a HX bearing. They are 0.001" extra clearance. I would have thought you'd see a clearance of 0.076mm (0.003") at least on a HX bearing from mid tolerance crank etc.

Why is it tight?

[ZimNismoBoy]

Thanks for the responses .

The crank grading was something like bbbbbb and 0000000 if im not mistaken the B's at the top and the 0's at the bottom .

But you have to remember this is a new crank .

Most build threads have listed a medium clearance of 0.050mm and this seems to be the norm even for the tomei genesis engine .

But on mine seems like its gone even bigger .

I plastigauged all of the mains and thats the clearance we got across the board .

thanks for the reassuring posts.

Now for something very different .

Got new rings and new pistons, tested ring gaps in the new block, and keep in mind rings are new from Nissan Jp.

Top clearance was 0.45 mm

second ring was 0.35 mm

Second ring falls in the larger end of the specs from the Gtr33 rebuild manual but the top ring is over the max allowed specs ?

Why would this be on a new set of Nur piston rings, do you think maybe nissan decided they would change the clearances because it was too small ?

Just seems weird?

[The Dan]

It is weird.

As I said earlier, it's not the measurements we would normally see with that combination. New crankshaft with HX bearings I would expect to see 0.003" clearance, not 0.0024"

As for rings, you should definitely consider a larger gap for the second ring.

I understand the manual says certain things and yes, the clearance of 0.0024" on these engines is perfectly fine. What I am getting at is that it's not consistent with what I'm used to seeing (and yes I have used many new cranks and blocks before)

There are still certain general rules that should be adhered to when building your engine. One of them is second ring gap should be larger than top ring gap

[T04GTR]

ACL have a pretty wide tolerance. ive measurerd them to vary almost 1/2 a thou. 1.5-2.5 thou is aok. any loser it will be lazy to raise oil pressure/ any tigher it will have to much pressure/and/or ware out under high power.

[ZimNismoBoy]

inherently thats what i have 0.0024" or 0.063 mm

across all the mains and i would expect it is a loose fit but having a tomei oil pump will help as the stock rev limit is 8400rpm.

On a second note the ring gaps ....

Top ring Chrome ring has a clearance of 0.50mm

Second ring has a clearance of 0.45mm measured again .

8

sorry im new to the terms and measurements please forgive any errors as measuring and using .00's is never been what im used as i dont work with engine everyday or measuring tools lol.

thanks for the input

[ZimNismoBoy]

sorry this post above is going off memory for the clearances i need to check with the paper i wrote on and make sure i have the right readings please hold fire on ring gaps let me get the actual readings and will post them up as far as i know the second ring gap falls in the tolerances but the top one is too wide and doesnt even meet the max ring gap ....listed in the manual .

[T04GTR]

having the big pump wll compensate for the looser fit.

2nd ring should have more gap than the top.or it will breath heaps at high revs.

[r33_racer]

having the big pump wll compensate for the looser fit.

2nd ring should have more gap than the top.or it will breath heaps at high revs.

Can you explain why it will breathe heavier with a tighter second ring gap?

All the race engines I know of run a tighter second ring gap and our ring manufacturer strictly recommends a tighter second ring gap, about 0.002" per inch tighter then the top ring. These engines dont suffer from any breathing issues and all have less then 2% leakdown. These engines typically run between 8.5k - 9.5k rpm also.

I was taught running a looser second ring would encourage it to breathe heavier as you are letting the bypassing pressure get into the crankcase easier. The other reason why you dont need a looser second ring is it doesnt run as hot as the top and because of this it doesnt grow as much.

Thats what I was taught anyway and is my 2 cents.

[ZimNismoBoy]

ok as of yesterday i have confirmed weird results but this is how it goes.

Across the board all 6 cylinders are 0.45mm on the top ring <======= TOP RING

Across all 6 second ring is 0.45mm <===== SECOND RING

And these are new rings going into a new block ??? i dont understand how come they are so big ? has nissan decided to make the gaps bigger ?

So that you dont run the small gaps on a small bore ?

I dont get it ?