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Another Boomin850 Problem

mbaker

By mbaker
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partsguy Newbie

partsguy

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also reading that lower compression, but okay leak numbers could mean timing is off a bit, which was also found.

no, these pistons were stock compression pistons from Wiseco....if anything, after overboring, the compression might have dropped a bit.

Inorrect, if you are using the same piston configuration just in an oversize, the cr will rise since you are squeezing a larger volume into the same size combustion chamber. low compression and increased blow by can also be from the timing belt being 2 teeth off, but I would expect the blow-by or leakdown #s to be closer across all 5 cylinders.

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partsguy Newbie

partsguy

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now, lets say the compression and leak down is what is stated, which from what I gather, is acceptable, and pretty good.....what do they mean, and what other issues can cause this blow-by? bad turbo? PCV? something to do with too much oil pressure?

did you keep the spec sheet? this is where you might have had the issue with piston slap....if for some reason you got 9:1 pistons, and the boring was done for 8.5:1, or something of that nature, maybe it would cause the issue?

Blow by and leakdown are caused by 3 things

1 - too much end gap at the rings allowing pressure to blow-by or leakdown

2 - valve timing being off causing the valves to be open at the wrong time allowing pressure to blow-by or leakdown.

3 - a crack in the cylinder head again allowing pressure to blow-by or leakdown

I doubt #3 since one cylinder is not dramatically different from the others.

Since we know #2 is fact, correct that and then do the tests again to get more accurate #s

Last but not least, you do not overbore to a cr, you overbore to the piston diameter. As I stated earlier, you will raise cr by overboring since you are now squeezing a larger volume in to the same size combustin chamber.

;)

The dealer did not fix it beacuse all that was authorized was an inspection (I assume since they did not do touch the belt), and the writer would need to contact the customer for the OK to perform work past what it was in for since it was not a warranty situation.

Not picking on you Pras, just felt the need to point out incorrect statements, unfortunatly, both of them by you, and give the correct info......... :lol:

Boy an I glad I have 1 of 74 Volvo certified Expert Techs in my corner when I'm unsure of something. I gave him a 4 litre bottle of Volvo trans fluid and asked him what model(s) it's used in since it came in as an incorrect shipment and I was unfamiliar with the part #. He screwed off the top and smelled it then told me what models it was for!!

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prasamin Newbie

prasamin

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Blow by and leakdown are caused by 3 things

1 - too much end gap at the rings allowing pressure to blow-by or leakdown

2 - valve timing being off causing the valves to be open at the wrong time allowing pressure to blow-by or leakdown.

3 - a crack in the cylinder head again allowing pressure to blow-by or leakdown

I doubt #3 since one cylinder is not dramatically different from the others.

Since we know #2 is fact, correct that and then do the tests again to get more accurate #s

Last but not least, you do not overbore to a cr, you overbore to the piston diameter. As I stated earlier, you will raise cr by overboring since you are now squeezing a larger volume in to the same size combustin chamber.

;)

The dealer did not fix it beacuse all that was authorized was an inspection (I assume since they did not do touch the belt), and the writer would need to contact the customer for the OK to perform work past what it was in for since it was not a warranty situation.

Not picking on you Pras, just felt the need to point out incorrect statements, unfortunatly, both of them by you, and give the correct info......... :lol:

Boy an I glad I have 1 of 74 Volvo certified Expert Techs in my corner when I'm unsure of something. I gave him a 4 litre bottle of Volvo trans fluid and asked him what model(s) it's used in since it came in as an incorrect shipment and I was unfamiliar with the part #. He screwed off the top and smelled it then told me what models it was for!!

oh, no worries at all. i don't know much about the numbers, so i'm glad you chimed in and explained it.....you're right, then. the first step needs to be to adjust the timing to what it should be....

Fuck you! I didn't fuck anyone over!

get over it you dirty whore! get back to fishing or boating or whatever the hell it is that you do :P

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prasamin Newbie

prasamin

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So are we now conceding that fucking up the timing is not an issue in and of itself?

it's definitely an issue, but doesn't mean that the engine is bad. the entire point of getting it checked was to give the kid some hope. shit, if it's as simple as timing, then he's golden. he's got a built engine, and it's not a complete loss like he was initially thinking. and, to give Mike a little credibility back, it's not as bad as initially thought. i really hope it's just the timing...Baker can get what he paid for....yes, a slight hiccup in between, but believe me, we all have them during builds and things of this nature.

still, i'm holding judgement till the timing is fixed. i hope that's the solution here.

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mbaker Newbie

mbaker

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So are we now conceding that fucking up the timing is not an issue in and of itself?

ohh it is and i am going to do the pcv system soon and then have my timing belt and everything changed and fixed.

mike

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mbaker Newbie

mbaker

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it's definitely an issue, but doesn't mean that the engine is bad. the entire point of getting it checked was to give the kid some hope. shit, if it's as simple as timing, then he's golden. he's got a built engine, and it's not a complete loss like he was initially thinking. and, to give Mike a little credibility back, it's not as bad as initially thought. i really hope it's just the timing...Baker can get what he paid for....yes, a slight hiccup in between, but believe me, we all have them during builds and things of this nature.

still, i'm holding judgement till the timing is fixed. i hope that's the solution here.

yea i hope you are right about all this!!!

mike

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