dts300z Posted May 6, 2008 Share Posted May 6, 2008 Well as you know I blew a head gasket.. hahaa So I got some new head gaskets and ARP head bolts and a few other goodies... Got it back together this past weekend button everything up and I noticed when I was adjusting the new rockers that the crankcase was smoking a little ( a fuckit ) so finished it up and put the valve covers on. Time for a test drive! lol wellit had a slight miss under load (man ♥♥♥♥!). So I took the day off today and did a compression test 2-8 inbetween 205-210. Number 1 35 or so lololll put a little oil in there up to 45 hahahaaa! Quote Link to comment Share on other sites More sharing options...
rustorbust Posted May 6, 2008 Share Posted May 6, 2008 oops Quote Link to comment Share on other sites More sharing options...
Pyro Posted May 6, 2008 Share Posted May 6, 2008 205 to 210 psi is a little high for pump gas, right? what compression ratio and cam spec? Quote Link to comment Share on other sites More sharing options...
dts300z Posted May 6, 2008 Author Share Posted May 6, 2008 205 to 210 psi is a little high for pump gas, right? what compression ratio and cam spec? not too sure if it is... It is stock compression (10.4:1 I think) and stock cam actually its a stock engine... it should be able to handle around 6-8 psi on stock internals but as you can see timming is not my friend... Quote Link to comment Share on other sites More sharing options...
zmaster Posted May 6, 2008 Share Posted May 6, 2008 that hurts a little, how is the cylnder wall for that piston? Quote Link to comment Share on other sites More sharing options...
dts300z Posted May 7, 2008 Author Share Posted May 7, 2008 that hurts a little, how is the cylnder wall for that piston? surprisingly enough it looks fine. all the chunks seem to stay intact until I pulled out the piston and picked them out.. Quote Link to comment Share on other sites More sharing options...
zmaster Posted May 7, 2008 Share Posted May 7, 2008 well thats good, at least you don't have to get the block machined Quote Link to comment Share on other sites More sharing options...
280zwitha383 Posted May 7, 2008 Share Posted May 7, 2008 two different rings broke? what could have caused that? Quote Link to comment Share on other sites More sharing options...
zmaster Posted May 8, 2008 Share Posted May 8, 2008 could be too high of a compression which could be a fluke..., or detonation, but there would be damage to the top of the piston if there was detonation.too high of rpm's can you recall what the rpm's were when this happened, thats all i can think of right now. Or the piston rings could have been instaled improperly, which would cause them to fracture, and when you hit those high rpm's, or high compression, or if that cylnder had a little detonation could have caused the fracture to break completely. Thats just my .02 cents on my engine knowledge. Quote Link to comment Share on other sites More sharing options...
dts300z Posted May 8, 2008 Author Share Posted May 8, 2008 two different rings broke? what could have caused that? actually it was the ring lands... This was cause by detination at a low rpm under load... If I had to guess it was prolly around 4500 or so... too much timing for the boost level +/- 6psi and factory timing.. I was too caught up in the moment and forgot to back the timing off a few degrees Quote Link to comment Share on other sites More sharing options...
dts300z Posted May 8, 2008 Author Share Posted May 8, 2008 could be too high of a compression which could be a fluke..., or detonation, but there would be damage to the top of the piston if there was detonation.too high of rpm's can you recall what the rpm's were when this happened, thats all i can think of right now. Or the piston rings could have been instaled improperly, which would cause them to fracture, and when you hit those high rpm's, or high compression, or if that cylnder had a little detonation could have caused the fracture to break completely. Thats just my .02 cents on my engine knowledge. yup it was detination but at low rpm, too much timing under load. BTW this is a stock 130k mile engine... with hypercracknic pistons loll.... Quote Link to comment Share on other sites More sharing options...
a6t8vw Posted May 8, 2008 Share Posted May 8, 2008 what ring gap where you running? the rings could have butted under boost should be opened up to .025 for boosted apps Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 8, 2008 Share Posted May 8, 2008 You need a descriptive title on your threads so that when people search they won't have to open "The Result" to find out if it has anything to do with their problem or question. Changing it now... Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted May 8, 2008 Share Posted May 8, 2008 broken rings are frequently the result of improper install with the non-correct clearances , on the rings OR the piston to bore clearances OR lack of proper oil flow to cool the bore and rings OR detonation, resulting in excessive heat, and frequently having the ring end gap drop to zero locking the piston in the bore for an instant until the rings or piston fracture. look closely at the ring ends look for contact marks and the piston lands , on the upper edges, look for a frosted crystaline surface appearance Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted May 8, 2008 Share Posted May 8, 2008 what ring gap where you running? the rings could have butted under boost should be opened up to .025 for boosted apps broken rings are frequently the result of improper install with the non-correct clearances , on the rings OR the piston to bore clearances OR lack of proper oil flow to cool the bore and rings OR detonation, resulting in excessive heat, and frequently having the ring end gap drop to zero locking the piston in the bore for an instant until the rings or piston fracture.look closely at the ring ends look for contact marks and the piston lands , on the upper edges, look for a frosted crystaline surface appearance I'd bet $$$ on what the two above have said. Been there and done that. Mild detonation often doesn't leave tell tale marks like you think. The increased heat likely did what you see there IMO. Like I said, don't ask how or why I know. If it can be broken, I've probably already done it. Quote Link to comment Share on other sites More sharing options...
dts300z Posted May 8, 2008 Author Share Posted May 8, 2008 You need a descriptive title on your threads so that when people search they won't have to open "The Result" to find out if it has anything to do with their problem or question. Changing it now... no problem! my apologies.. Quote Link to comment Share on other sites More sharing options...
jack46 Posted May 8, 2008 Share Posted May 8, 2008 should be able to handle around 6-8 psi on stock internals but as you can see timming is not my friend... I always hear 6 - 8 psi on stock pistons but have not seen anyone have one last. I lost a set of stock with 8 psi and so did a friend. Timing and 'good' tune will help them last but ... As an additional data point a friend has a Z06 running intercooled 8 psi WITH Methanol and professionally tuned on dyno. He is huffing and puffing and has similiar compression in 2 cylinders. This is after only ~5,000 miles. Boost is deadly replace them with a good set of forged piston and immediately have a tune in place that lowers timing and allows more timing to be removed when/if needed. Don't forget to adjust the minimum timing if this is an LT1. Sorry about your loss but you will be fine Good luck Jack Quote Link to comment Share on other sites More sharing options...
dts300z Posted May 8, 2008 Author Share Posted May 8, 2008 what ring gap where you running? the rings could have butted under boost should be opened up to .025 for boosted apps It would be a stock ring gap as this is a stock engine with 130k miles that has had alot of abuse at least since I have had it..loll I understand what you are saying though. Quote Link to comment Share on other sites More sharing options...
dts300z Posted May 8, 2008 Author Share Posted May 8, 2008 broken rings are frequently the result of improper install with the non-correct clearances , on the rings OR the piston to bore clearances OR lack of proper oil flow to cool the bore and rings OR detonation, resulting in excessive heat, and frequently having the ring end gap drop to zero locking the piston in the bore for an instant until the rings or piston fracture.look closely at the ring ends look for contact marks and the piston lands , on the upper edges, look for a frosted crystaline surface appearance Man you guys are insane... You are way too knowledgable for your own good... loll Thanks for the help and I will be sure to check these things tonight.... Quote Link to comment Share on other sites More sharing options...
dts300z Posted May 8, 2008 Author Share Posted May 8, 2008 should be able to handle around 6-8 psi on stock internals but as you can see timming is not my friend... I always hear 6 - 8 psi on stock pistons but have not seen anyone have one last. I lost a set of stock with 8 psi and so did a friend. Timing and 'good' tune will help them last but ... As an additional data point a friend has a Z06 running intercooled 8 psi WITH Methanol and professionally tuned on dyno. He is huffing and puffing and has similiar compression in 2 cylinders. This is after only ~5,000 miles. Boost is deadly replace them with a good set of forged piston and immediately have a tune in place that lowers timing and allows more timing to be removed when/if needed. Don't forget to adjust the minimum timing if this is an LT1. Sorry about your loss but you will be fine Good luck Jack Yes it is an LT1 and I have the factory tune with an FMU hahaaaa!! I know, I know I just wanted to get it on the road and now look where thats got me.. I am working on getting a short block right now so I can do the works to it.. Splayed mains, h-beam rods, JE pistons, forged crank (although this will be a long process) and I will surely have someone tune this for me as I understand tuning and its concept just not patient enough... Thanks again Quote Link to comment Share on other sites More sharing options...
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