pistons keep cracking
Re: pistons keep cracking
My first thought... With any rebuild with over 100k miles on it, all the bore specs should be measured. In the pics the op put up, there is quite a bit of scoring on the bores. The block may have been past the point of a simple hone job to clean up the surface.
Was anything measured?
Checked for roundness?
Piston to wall clearance measured?
The new piston may not have been within specs for your used block.
Were the rings sized and oriented correctly?
Piston rings themselves arent meant to support the pressure of combustion, they are supposed to work together with the piston, when at operating temp, to form a better seal.
If the bore was out of round or worn to the point of excessive piston to wall clearance, this may happen due to higher stress on rings and ringlands.
Im no professional tuner/ engine builder, This is just my .02 cents
Was anything measured?
Checked for roundness?
Piston to wall clearance measured?
The new piston may not have been within specs for your used block.
Were the rings sized and oriented correctly?
Piston rings themselves arent meant to support the pressure of combustion, they are supposed to work together with the piston, when at operating temp, to form a better seal.
If the bore was out of round or worn to the point of excessive piston to wall clearance, this may happen due to higher stress on rings and ringlands.
Im no professional tuner/ engine builder, This is just my .02 cents
Rebuild this engine complete. As in, go up to 81.5 mm pistons, fresh bore and hone. I've seen this happen on a turbo motor where the pistons and ring were replaced on the motor with the original bores. It turns out the bores were out of spec and there was significant blow by.
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Re: pistons keep cracking
what do you guys think im running. i have a stock distributor but im using msd wires thats it theres no other msd product on my car. i have the service manual by acura so ive been doing what the end ring position are pictured on the page. and this is what ive been doing
but then i looked around and saw this picture which is completely different then the what the service manual has been telling me. so who is right.
http://www.team-integra.net/sections...4bb0768c9d.jpg
but then i looked around and saw this picture which is completely different then the what the service manual has been telling me. so who is right.
http://www.team-integra.net/sections...4bb0768c9d.jpg
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From: upstate, ny, us
Re: pistons keep cracking
If the valves floated there would be evidence of piston to valve or valve to valve contact, which usually ends in broken valves and hole in a piston. I dont see any of that in your pictures.
My money is on out of round or severely worn out cylinder bores.
My room mates ls vtec turbo del sol lost the ringlands on 3 of the 4 pistons after making 3 track passes same day it got dyno'd by a decent tuner. After a rebuild with oem pistons it runs perfect. The oem pistons and rings had over 200k on them. But after alot of measuring, found that it was strait, true and within specs from oem service manual.
The pic posted of ring orientation is right out of the helms manual and is how honda does it from the factory. The link you posted to the other diagram looks like one someone drew on ms paint. Ive built 3 motors this season with the helms manual and they all run perfecly.
My money is on out of round or severely worn out cylinder bores.
My room mates ls vtec turbo del sol lost the ringlands on 3 of the 4 pistons after making 3 track passes same day it got dyno'd by a decent tuner. After a rebuild with oem pistons it runs perfect. The oem pistons and rings had over 200k on them. But after alot of measuring, found that it was strait, true and within specs from oem service manual.
The pic posted of ring orientation is right out of the helms manual and is how honda does it from the factory. The link you posted to the other diagram looks like one someone drew on ms paint. Ive built 3 motors this season with the helms manual and they all run perfecly.
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From: schooling kids in ny, usa
Re: pistons keep cracking
that pic is how i position my ring gaps. the actual gap and piston to wall i use comes from the piston manufacturer.
i agree with some of the other people, go 81.5, get new pistons and bring them to the machine shop with the block so you can have all the tolerences be exact
i agree with some of the other people, go 81.5, get new pistons and bring them to the machine shop with the block so you can have all the tolerences be exact
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From: texas
Re: pistons keep cracking
go forged! gap rings rite! use good gas! maybe new tuner but id do this 4sho to be safe cus u keep cackin then all that money gona add up but hopefully that works if not yea tuner sucks specially if he blowin it up on dyno haha
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From: Seahawks WA, USA
Re: pistons keep cracking
Hes got a good tuner, the rings were gapped correctly, its just a weird situation.
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From: Ontario, CANADA
Re: pistons keep cracking
There is a tonne of great advice and overall knowledge/experience-sharing happening in here. A thread like this is very refreshing and reminds me why forums are a great tool in the right hands.
I hope your rebuild goes well, I'm going to encourage you to pursue this as many others have.
I hope your rebuild goes well, I'm going to encourage you to pursue this as many others have.
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Joined: Aug 2009
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From: Baton Rouge,Louisiana
Re: pistons keep cracking
Nah, my first instinct is to get all of the facts...
I get two or three phone calls a day from people who have just been tuned by someone else with questions and I do my very best not to throw my comrades under the bus unless there is blatant irresponsibility, and even then...
Two weeks ago I retuned a full blown track car that someone else had tuned previously (and blown up)...I puked in my mouth a little when I saw the maps, but retuned the car and the customer told me he was happy. A week later I get an email from the customer asking me to write a letter indicating the old tune was crap and that I fixed it so he could dispute charges against his old tuner (who he said he went to for years)...I declined.
The tuner is always the last to get his hands on the car and the first to be blamed if a problem happens...I fight my *** off to always make the customer happy, I dont need to fight with other tuners on my abilities to map a car or their lack of abilities to do the same.
The customer is most important...
I get two or three phone calls a day from people who have just been tuned by someone else with questions and I do my very best not to throw my comrades under the bus unless there is blatant irresponsibility, and even then...
Two weeks ago I retuned a full blown track car that someone else had tuned previously (and blown up)...I puked in my mouth a little when I saw the maps, but retuned the car and the customer told me he was happy. A week later I get an email from the customer asking me to write a letter indicating the old tune was crap and that I fixed it so he could dispute charges against his old tuner (who he said he went to for years)...I declined.
The tuner is always the last to get his hands on the car and the first to be blamed if a problem happens...I fight my *** off to always make the customer happy, I dont need to fight with other tuners on my abilities to map a car or their lack of abilities to do the same.
The customer is most important...
The last person to touch it is always the last person to be blamed.. its amazing.. how quick people are to judge without all the facts..
Here's some things to try and for informative purposes
- Plug gap? and heat range used
- I run msd wires no problems, thats about the only thing from msd i'd run. However.. have you tried new wires, if so which
- Have you tested your dizzy out, ign and coil.. honestly from looking at the pistons they look evenly burned until the ones your having problems with, which seem to be running really...really lean..
check the above, is it possible a injector is getting stuck close?? or maybe a injector wire is loose and not making good contact..
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From: Baton Rouge,Louisiana
Re: pistons keep cracking
I dont think valvefloating had anything to do with this situation, your pistons look lean, and i'll personally vouche for chris, its not the tune, this is something else causing you to go lean, i'd look at your injector wiring.. something isn't working properly.
Re: pistons keep cracking
will i get an engine light if one injector wire pops out? ill try locking the clips in with some wire how does that sound. or can it be that im useing a gsr exhaust cam and ctr intake cam? cause i think that could be it too.
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Joined: Aug 2009
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From: Baton Rouge,Louisiana
Re: pistons keep cracking
Check the wiring to your injectors, make sure there's no cuts or anything of that nature and make sure that they are all snug.
I'd like to know what plugs / gap your using and as well have you tried new wires?
I'd also like to know if you've looked into using another dizzy.. this still seems like a odd problem.
All Motor Mentor
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From: 902, Nova Scotia, Canada
Re: pistons keep cracking
When piston rings aren't "clocked" properly, or are worn out, or the cylinders are worn out of spec and there's a lot of blow-by in the engine, engine oil gets introduced to the combustion process. This has a bad effect on the engine in that it effectively lowers the octane rating of the fuel, causing it to be prone to detonating and cracking ring lands.
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From: Baton Rouge,Louisiana
Re: pistons keep cracking
When piston rings aren't "clocked" properly, or are worn out, or the cylinders are worn out of spec and there's a lot of blow-by in the engine, engine oil gets introduced to the combustion process. This has a bad effect on the engine in that it effectively lowers the octane rating of the fuel, causing it to be prone to detonating and cracking ring lands.
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From: Birmingham, UK
Re: pistons keep cracking
When piston rings aren't "clocked" properly, or are worn out, or the cylinders are worn out of spec and there's a lot of blow-by in the engine, engine oil gets introduced to the combustion process. This has a bad effect on the engine in that it effectively lowers the octane rating of the fuel, causing it to be prone to detonating and cracking ring lands.
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From: b00sting my D16s, SoWis, USA
Re: pistons keep cracking
When was the head last rebuilt? A 95 GSR head is 15 yrs old. Certain parts, like dohc vtec heads, may have circulated to several people and beat countless miles before making it onto a turbo motor. In my experience, stationary rubber parts only last 10-15 years max. Much less when exposed to heat, petrolium, and constant friction.
If anyone remembers the CP debacle, they claimed their pistons were melting due to oil in the mix. Leaking valve seals or rings (from bad sleeves) allowed oil into the CC, which burns hot, and causes detonation. Forged pistons took it, but eventually melted. That brings up the other point - the addition of forged pistons won't fix the original problem, just prolong the effect of that problem.
If anyone remembers the CP debacle, they claimed their pistons were melting due to oil in the mix. Leaking valve seals or rings (from bad sleeves) allowed oil into the CC, which burns hot, and causes detonation. Forged pistons took it, but eventually melted. That brings up the other point - the addition of forged pistons won't fix the original problem, just prolong the effect of that problem.
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From: Ontario, CANADA
Re: pistons keep cracking
Agreed^
If pistons are going to be replaced with forged units, take it .5 over while it's apart. Eliminate it as a potential problem. This seems to be the issue that more people are pointing toward.
If pistons are going to be replaced with forged units, take it .5 over while it's apart. Eliminate it as a potential problem. This seems to be the issue that more people are pointing toward.
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From: Cincinnati,, Oh
Re: pistons keep cracking
When piston rings aren't "clocked" properly, or are worn out, or the cylinders are worn out of spec and there's a lot of blow-by in the engine, engine oil gets introduced to the combustion process. This has a bad effect on the engine in that it effectively lowers the octane rating of the fuel, causing it to be prone to detonating and cracking ring lands.
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From: schooling kids in ny, usa
Re: pistons keep cracking
and yes you should get a cel if an injector pops off (code 16 iirc)
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From: jacksonville, fl
Re: pistons keep cracking
im going to vote improper ring gaps. since its relative to only 2 cylinders. it could be piston to wall clearance, gap, improper ring seal causing oil to enter the chamber and drop the overall octane rating of the fuel in those 2 specific cylindersl.