td42 blowby after rebuild

[phatmandy]

Hey guys,

After my old gq was claimed by the rust demon i purchased a 89 swb safari. I rebulit my silver top td42 using upgraded 30mm dia conrods and pistons, new injectors, reco fuel pump, new head (as crack was found). plus installed a denco turbo kit. and installed it into the shorty. it had quite a bit of blow by, forcing oil to seep around oil filler cap and tappet cover.

So i installed an oil catch can in the hope it would settle as the rings wore in. im around 10 000 ks and she dont seem to be getting better. i did a comprssion test which were all above normal. i also done a leak down test which showed around 10 % leakage at 100 psi. with some leaking thru the intake valve also adding oil to the cyclinders did not make much difference. also the blowby seems to get worse when at running temp rather than cold. also same blow by with turbo pipe not installed.

Could a leaking intake valves be the issue? is there a better way to isolate where the blow by is comming from? any ideas and questions to help me solve this are apprietiated.

[huey_gq]

Just at a guess it could be your head gasket leaking and you could be getting compression down the oil return galleries. Is it getting any smoke or misty oil coming out of the filler hole with the engine running / boosting? I thought i might of done that before i did a compression test and one of my cyliners was way below the others.

[phatmandy]

It is misty yes but no real difference between cylinder compression

[nissannewby]

How much is to much? They do blow a little. If all the compression are above spec then I would worry to much. Maybe check the pcv make sure its breathing freely and not allowing the crankcase to build a little pressure. Did you use any oil in that 10k?

[phatmandy]

the pcv is defiantly free flowing. but there is so much flow the standard outlet seems to be restricting it. that is y I believe it to be excessive. I added a provent with an adapter to use larger diameter hose which helps somewhat but still has the initial restriction at the outlet. maybe i should try upload a vid.

[nissannewby]

Is there any oil usage?

[phatmandy]

some but bugger all. only whats ening up in the provent as i dont have it return to sump.

[nissannewby]

Is it possible on the rebuild some of the ring gaps are in the same place?

[phatmandy]

Nope checked them suckers 3 times

[Parksy]

Did the cylinders get honed before the pistons were fitted? Apparently there's an old trick of sprinkling a washing detergent, namely Bon Ami into the intake, and it would rough up the cylinders to help bed in rings that hadn't bed in properly. Haven't done it myself, only heard about it. I'm sure google would come up with something.

[phatmandy]

yea they were honed by the machine shop and cleaned had a really good crosshatch

[the ferret]

Take it down the beach and give it a good flogg'n, this will de glaze the bores and help the rings bed in.
Cheers, the ferret.

[89gqpatrol4x4]

Don't know if this helps but I have a skyline with 10% leakage and runs fine! Where I used to get it tuned, they had a nine second GTR with 13% blow by and weren't conserned.

[phatmandy]

she has had many beach trips and lots of towing a full car trailer. She runs fine just has what i think as excessive blowby. maybe im just paranoid lol.

[SupRob]

Did you build the engine yourself?

When you checked ring gaps, did you check them over time or 3 times before you put the head back on?

[phatmandy]

Did you build the engine yourself?

When you checked ring gaps, did you check them over time or 3 times before you put the head back on?

Yep i sure did. I checked the gap once as it was all machined at the shop with the pistions and rings.

[SupRob]

Just curious, did you put oil squirters in the block ?

Afew things im sure you did, Right head gasket suit pistions? Changed Head bolts? Block wasnt warped? Natural head or Turbo head?

What brand was the parts you used?


Rob,

[phatmandy]

Yup oil squirters were brand new. thickest headgasket, no same headbolts but corretly set, block was fine from machine shop, natural head.. im guessing you can get different precombustion chambers? all pistons and bearings, seals came from engine australia. from memory they are riken rings.

[SupRob]

Buddy sorry to say you more then likely got chinese parts pending on what kit you bought from them..

Were the pistons a horsie branded pistons?

I have had quite a few people do a td42 natural and reconed it with turbo internals, not %100 sure however i have been told the td42t head drops straight on. Ill try and sus it out at work tomorrow.

With the headbolts, did you measure the length of the bolts and how deep the thread hole was? After they have been torqued down once alot of engine rebuilders will toss the old bolts out and buy new ones as they are a strech bolt.

Rob,

[phatmandy]

G'day Rob,

I cant recall the brand off the top of my head i might try find my receipt. that would be good to know about the head if it comes to me pulling her down again. Had no drama with the head bolts bottoming out or anything and they were tightened an extra 10 nm past standard spec. but will replace them if i need to take the head off.

[Burto]

G"Day, Are you using a top quality oil?, Have had happen the past, people overhaul the engine and then in good faith use the best oil they can get, the problem sometimes is that the oil is too good and wont allow the rings to wear/bed in. try using a straight engine oil without all the antiwear additives etc, and then after a 5000km runin period change the oil and filter using the oil you would normally use. Hope this helps. As if you had a crosshatch pattern, the rings gaps were not excessive and not aligned on the piston on fitting, the rings and bore should wear together

[phatmandy]

* #15 * *
Today, 03:06 PM

phatmandy
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Garage

It got worse so I have pulled her all down again. Pistons caked in Carbon. Leak down test proved all the intake valves were leaking. Bores had vertical scores and hone marks were gone with shinny spots on the pin sides. Turbo had leaking seals. Will upload photos when I get a chance. Ring gap was .5mm and piston to bore was .003" . Pulled turbo apart. Movement was not excessive and looked good from some light scoring on the shaft it looked good. Have a feeling the crank case pressure was so bad it upset the turbo drain causing it to fill the turbo housing. Will be getting the injectors crack tested soon.