New Engine Blown Up At Tuners

[Guilt-Toy]

in 15 years ive never come across that scenario tbh....

yeah i'm still trying to work out how that could happen........

[DVS JEZ]

Rod stretch at high rpm?

One of my trucks dropped a valve and the amount of blowby an smoke it created was crazy. New head and it was all fixed.

[Rolls]

Possible, but I really doubt it is the cause of his issues though.

[tridentt150v]

Not really related, but I once built an engine for somebody [had them there watching and being my gopher], strapped the head on and started to set the valve clearances and the motor wouldn't turn over TDC [turning it by hand]. Would go up and clunk, not hard, but a solid lock, I didn't force it like my gopher wanted me to do.....lol hitting the head, I 'd wound the valve adjusters out so knew it couldn't be them???

I stripped the head off and all the pistons were coming up proud in the bore by 2-3mm. Went and got the boxes the pistons came in and they were the correct ones by the box and part numbers. And it was a major and trusted company. It was something I didn't check.......didn't expect it.

I ended up sending them back to the business that I got them off and had another set sent to me. They couldn't believe it either - and wasn't their fault, the wrong pistons had come in the right box from the factory. We couldn't even figure out what engine the pistons were for? The gudgeon pin height was set lower in the piston giving it more length at TDC. the piston dia was good, the rings and lands fit, but the wrong pin height. It wasn't a Nissan BTW.

[joe blo]

maybe the mahle cast pistons arent as strong as the nissan ones?

[STATUS]

maybe the mahle cast pistons arent as strong as the nissan ones?

im betting a bit of det pushed em over the edge.

[joe blo]

with the block bored 40 thou over and minimum use after it would i be able to put some other brand cast pistons in this motor to try again? different tuner. the guy wasnt real good at the wolf to start off with

should i do leakdown test still or is the compression test enough to warrant pulling it apart?

wanna go full forged motor but id blow so much on it if i did. coz id get this and that and then i might aswell get that and that also sorta thing

Edited July 30, 2011 by joe blo

[Rolls]

There is obviously something seriously wrong with those compression results, get someone who knows what they are doing to strip it down and give you a report on the failure.

[lilcrash]

I may be wrong but that engine was not run in properly. It's as simple as that, pistons out, re hone the bores and new rings at a minimum.

[mico]

thats way too much oil aswell. while the engine is out use a 1.5mm restrictor and block the other off. what oil pump, n1 ?

[AngryRB]

That compression test shows some cylinders at 60

so all the gases are blowing by and into the sump, then that would result in oil and gas venting up to the head and out the breathers wouldnt it?

Did you say the workshop installed the pistons and rings?

When you bore out the cylinders they have to be left with very light scratches, deep scratches stop it bedding in, and i dont think 4000rpm and 20psi is a good idea for atleast a few thousand km's,

You might be glazing up the rings instead of bedding them, to bed them you load the engine up under 3000rpm in a high gear for a 1000ks or so or can someone correct me if its changed?

I think the problem is either the ring installation, the boring and clearance , and the run in procedure,

I think the whole process sounds rushed , you cant just build a motor and be on the dyno after a few hundred km's and be boosting up to 20psi

surely that isnt good for rings that are trying to bed in, maybe that caused a few rings to break if they werent already

Edited July 31, 2011 by SliverS2

[STATUS]

I may be wrong but that engine was not run in properly. It's as simple as that, pistons out, re hone the bores and new rings at a minimum.

run in is simple, load it up, let it cool load it up, let it cool then tune flat out..... done it that way for years no failures... very often the farthest it drives is from engine hoist to dyno.

[r33_racer]

run in is simple, load it up, let it cool load it up, let it cool then tune flat out..... done it that way for years no failures... very often the farthest it drives is from engine hoist to dyno.

Exactly right!

People get carried away with run in when its not necessary. You want a good amount of load straight off to get the rings to 'bed in', otherwise it just wont happen and if it does, it wont be as good as it can or should be. And it happens alot faster then people think.

Driving around for 1000kms on a safe low power, rpm restricted tune is a wives tale and only slowing down the process. Get a proper understanding how rings work first then you can figure out why thats not the best way to bed in a new engine.

Its the same with engines that are assembled with heaps of oil on the rings and bores....just makes it harder to get rings to seal and 'bed in' properly.

[joe blo]

going by the compression test results is it time to pull the motor out? leakdown test not required now?

[r33_racer]

Yep. Definitely.

To pull it out i mean.

[AngryRB]

Exactly right!

People get carried away with run in when its not necessary. You want a good amount of load straight off to get the rings to 'bed in', otherwise it just wont happen and if it does, it wont be as good as it can or should be. And it happens alot faster then people think.

Driving around for 1000kms on a safe low power, rpm restricted tune is a wives tale and only slowing down the process. Get a proper understanding how rings work first then you can figure out why thats not the best way to bed in a new engine.

Its the same with engines that are assembled with heaps of oil on the rings and bores....just makes it harder to get rings to seal and 'bed in' properly.

Ive always been a bit confused bout the run in procedure, some different opinions around, but if you guys say you've done hundreds of engines with no failure then ill take your word on it..

[Rolls]

The general consensus on here is bed rings in then go for gold. It's all the old school guys that say to drive them for 1000kms etc, it just isn't necessary today.

[AngryRB]

just a quick question, how many revs do those rb25/30 engines rev to safely, assuming they are standard parts etc?

and what piston to bore clearance is ideal?

[Rolls]

I wouldn't take it much over 6500-7k with standard everything, plus with stock cams and a non stupid sized turbo you don't need to take it over that to make big power.

piston clearance is all based on the pistons being used, they will state what is recommended. Forged are usually quite a bit larger due to expansion.

[lilcrash]

Status I agree with what you have said, also my understanding is boost actually helps the rings bed in quicker, but from those compression test results my experience says those rings didn't bed in.