Strange Rattle rb26/30

[Skitzvk]

hey guys just got my engine together and once it started. from around 3000rpm there is a rattle from the top end. at first it sounded like a broken valve spring. but at idle car is quiet. so decided to take head off and have it sent off to be inspected and checked. head came back a week later and turned out fine. all parts were inspected and checked for clearances. also in mean time i checked the piston heights incase it was a bottom end bearing. but motor before 26 head conversion was very sound. so head go's back on and start car up and noise is still there. now the ecu is a haltech elite witch has just got a base map on it. one person from the machine shop where the head was done. said it could be detonation ?  car is running e85 with 2200cc injectors. im just looking for some feedback or ideas. as this is got me stuffed and i dont wanna give the car to the tuner with issues

 

cheers guys

 

[GTSBoy]

It won't detonate running no load, unless one of the injectors is spraying only a tiny % of what it is supposed to.  And even then, I wouldn't expect it to ping so that you could hear it and think it was mechanical noise.

And it will also be very unlikely to ping audibly on E85 anyway.

[Skitzvk]

ah ok so guess that rules that out.

can a cas cause a sound like this. my tenisoner and idly puller and belt are all brand new

[GTSBoy]

The CAS would need to be quite broken.  If you haven't/can't isolate it to the CAS or any other part of the top end, use a lump of wood as a stethoscope and try to find the noisiest part.

[Skitzvk]

we did try that and it sounded like it was coming from exhaust head side on number 1.unplugged each coil one at a time . noise still remained . its a real head scratcher

[Rusty Nuts]

Check the cam gear bolts, recently had a rattle in this area on a RB25 the bolts were clipping the inside of the cas.

[Skitzvk]

2 minutes ago, Rusty Nuts said:

Check the cam gear bolts, recently had a rattle in this area on a RB25 the bolts were clipping the inside of the cas.

ah ok ive heard this. especially when not running the cam cover. witch im not. i would of thought the noise would be from idle. not from certain rpm. but i will have a look at that. cheers mate

[Rusty Nuts]

The same thing happened with mine, I think the camshaft is pulled fowards very slightly as revs increase, I found very very fine aluminium filings on the back of the cas. Otherwise did you have lifter bores checked they can stick if they rock in the bores. Were small end bushes new??

[Skitzvk]

do you mean lifer buckets that the shims are under ? if so yep i had them checked and all were in spec. not to sure what you mean by small end bushes.

[Rusty Nuts]

Sorry, small end bushes in your rods,  piston (or gudgeon) pin bush

[Skitzvk]

ah ok na there will all good from the motor i used. all was running fine before it was used for this conversion. would you happen to know how bigger spacing would be needed for c.a.s not to knock cam gear bolts

[Rusty Nuts]

There are small steel bushes in the cam belt cover that space the cas the correct distance. Make sure you have original mounting bolts for cam gear installed ,the original bolts have quite shallow heads. 

[Skitzvk]

9 minutes ago, Rusty Nuts said:

There are small steel bushes in the cam belt cover that space the cas the correct distance. Make sure you have original mounting bolts for cam gear installed ,the original bolts have quite shallow heads. 

I did order the oem cam gear bolts from Nissan but ill check the spacing of the cas to gear tomorrow. Thanks for your help so far

[iruvyouskyrine]

You can just buy the CAS gasket and use that to space it out if not running the front timing cover. Should come with the bushes in there to space it properly.

[Rusty Nuts]

Thanks Josh, that would definitely work.

[Skitzvk]

On 1/3/2018 at 8:45 AM, iruvyouskyrine said:

well pulled out cas and checked if it has been touching the cam gear bolts and it hasnt.

 

 

[vito_96]

I know it's old post but did you ever find out what it was.