What Is Wrong With My Rb26?

[Duncan]

So....what is wrong with my RB26?

Recently rebuilt by a engine builder with very suspect abilities. Completed 2000klm since rebuild including 4 oil changes. Running standard computer and standard boost. Rev limit is 8500.

Last 1000klm since running in finished have been a practice day at Wakefiled Park, a race meet at Oran Park and a race meet at Wakefield. In the last race at wakefeild I heard a knock on the last lap, finished the cool down lap and parked it.

The problem - there is a knock/tap in the motor. rises with revs

Oil pressure is normal (great)

Compression test results:

# - Dry test - wet test

1 - 10.5 kg/cm2 - 12.5 kg/cm2

2 - 12 kg/cm2 - 14 kg/cm2

3 - 12 kg/cm2 - 14 kg/cm2

4 - 12 kg/cm2 - 14 kg/cm2

5 - 12 kg/cm2 - 14 kg/cm2

6 - 11.5 kg/cm2 - 13.5 kg/cm2

Battery was boosted by a running car, engine was dead cold. No leakdown test

The noise sounds like it is coming from the top of the motor, maybe at the front or maybe I am imagining it. I put a screwdriver on the head next to my ear, and looked like a person with a screwdriver in my ear.

Anyway....lets have some educated guesses about what is wrong...answers to come sometime in the next few weeks when I get around to pulling it out.

[BU5TER]

I vote we find the engine builder and kick him in the nuts

[Duncan]

hey there is no dyno graph in this thread so there should be no dick swinging. BTW shut ur mouth in ur avatar and take another photo

[wrxhoon]

Duncan ,

It doesn't sound good mate , at a guess ( wild one at that ) i would say its a big and bearing , usualy one at the rear ( number 6 ) but you have a built engine so who knows if they checked clearances or not when they assembled it .

Compression on number one is very suss for a built engine as well as number 6 .

when you say wet test ai would assume you mean you put oil in the cil and heaps of it by the look of the resaults .

The comp test shoul be done on a warm engine and the throttle fully open .

Do a leakdown test it will give you a bit more info ( more reliable ) .

Does the knock get louder as it warms up ? Is it there when you first start it cold ?It could be a lifter or even an injector but my money is on a big end , but i hope i'm wrong .

[Duncan]

yeah I wasn't shy with the oil....

Will actually get hold of a leak down tester at some stage but it wont help decide if I have a head or ring problem will it?

The knock is there from cold, not noticably noisier when warm. But I didn't run it up to temp today I dont want to do any further damage.

Bearing clearances were checked at the rebuild and they suggested standard size bearings which i was a bit surprised about I thought an older crank that had been machined might need oversize bearings. Unfortunately I didn't measure the clearances myself

Injector is interesting....when can an injector get noisey? I might throw another one in and see if there is any difference to the noise.

What can fail in a lifter? got any pics to edumacate me?

[Duncan]

Did you check for woodpeckers inside before u put the block back together? Hope it's not anything serious

[wrxhoon]

  Duncan said:

yeah I wasn't shy with the oil....

Will actually get hold of a leak down tester at some stage but it wont help decide if I have a head or ring problem will it?

The knock is there from cold, not noticably noisier when warm.  But I didn't run it up to temp today I dont want to do any further damage.

Bearing clearances were checked at the rebuild and they suggested standard size bearings which i was a bit surprised about I thought an older crank that had been machined might need oversize bearings.  Unfortunately I didn't measure the clearances myself

Injector is interesting....when can an injector get noisey? I might throw another one in and see if there is any difference to the noise.

What can fail in a lifter? got any pics to edumacate me?

<{POST_SNAPBACK}>

I have a leakdown tester but you will need a compressor to do the test , i can do for you if you like and i maybe able to give you a more educated guess as to whats wrong with it .

If its a bearing you will do more damage to the crank by running it but if you pulle it out you should change the crank with a new one anyway , if you spin the bearing then conrod through the block is possible .

If the crank was machined they would have used undersize bearings .

Injector can be noisy warm or cold .

A lifter can be come noisy when the clearances grow , there nothing wrong with the lifter , just bigger clearance . you can check with a filler gauge but you need to take the rocker covers off .

The lower comp on the 2 cil maybe because they had the valve clearances to tight ( to have a quiet engine ) and the valves are starting to burn a little .

Did you check comp before ?

You are correct in saying a leakdown test wont tell you if it leaks for valves or rings but it will still tell you more than a comp test .

To much oil in the cil thats the reason comp went up so much ( you made the combustion chamber smaller ( like having higher comp ratio ) .

Edited October 3, 2005 by wrxhoon

[Duncan]

Thanks Jerry at this stage Im going to pull it out anyway so all well be revealed.....

[Duncan]

  Duncan said:

Did you check for woodpeckers inside before u put the block back together? Hope it's not anything serious

BTW this was funny....but I didn't post it.....SAU stuffing up or have I been ha><0r3d?

[wrxhoon]

Duncan ,

I just thought of another possibility , just make things abit more complex , could be a gudgeon pin as well , depending on what they used , pistons and circlips or spirolocks , one of them may have come off !!! Then the knock you hear could be the gudgeon pin hiting the bore , you said it sounds like coming from the front didnt you ? That will explain the lower comp on number one as well , the circlip could have scored the bore .

Hard to say without hearing it and knowing how / what they used in the build .

[Duncan]

The dodgy builder just reused the standard circlips so that could be another possibility, I could see that with a bore scope right? i need more tools

[ylwgtr2]

sounds like a big end

[Duncan]

will you guys stop with the bad news

Any suggestions on how to tell if it is a bearing before I pull the sump off it?

[NXTIME]

who was this dodgy builder?

[Beer Baron]

i can say with certainty that it's not a big end bearing... i would definately look into the woodpecker idea though. they can make a noise quite similar to bearing knock as their beaks aren't compatible with the cast iron RB block...

also, could be tinitis from standing around Niels race car or other hearing damage caused be the screwdriver in your ear (you did put the handle in you ear right?) or a combination of the two problems. and actually you have no problem at all. except for the permenantly damaged hearing which is preferable to another RB26 rebuild...

feel better duncan?

[Duncan]

no bastard I dont feel better

nxtime....the dodgy bastard is....

sorry cant name them in a thread, but pm me for details.

[Duncan]

HAHAHHAHAHAH as if! the dodgy builder is ME!

[NXTIME]

I thought so - just needed you to confirm the dodginess! :D

[Tommyk]

i also put my hand up for the woodpeckers !

Mustve somehow gotten into the engine when it was b eing built

:s

[Duncan]

BTW it sounds more like a gnome with a small hammer than a woodpecker