help again. burnt pistons
04-22-2008, 03:29 AM
#41
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I've used the Sealed Power plasma moly & hellfire rings, Ackerly & Childs Hellfire rings, Hastings Power Flex, & Total Seal's line up of rings without any troubles before. As long as you use a quality piston ring and file fit them correctly you should be just fine.
04-22-2008, 08:51 AM
#42
Forged pistons tend to "go plastic" before they would ever crack. They are softer material than the hypereutectic pistons and will bend/melt/flex before they break. You shouldn't have cracking issues with the forged pistons unless something goes terribly wrong.
04-22-2008, 10:43 PM
#43
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Based on all of the posts Gadget made I doubt this is a piston or ring problem...
Detonation broke those pistons.
I would bet "93 octane and octane booster" and not knowing where the timing was with over 12 to 1 compression hammered those pistons apart.
I've seen it many times.
Ordering just two pistons is another recipe for disaster, all of those pistons were subject to the same forces. I would look for closed up ring lands in the remaining 6 as evidence of the hammering. Look at the rod bearings for this type of damage.
With that much compression a minimum of 110 octane fuel, 14 to 16 degrees initial, 36 total with it all in by 3500 rpm and that engine will live with either the Forged or Hypertetic pistons. If you want to spray it back the timing down 6 degrees at the hit.
Detonation broke those pistons.
I would bet "93 octane and octane booster" and not knowing where the timing was with over 12 to 1 compression hammered those pistons apart.
I've seen it many times.
Ordering just two pistons is another recipe for disaster, all of those pistons were subject to the same forces. I would look for closed up ring lands in the remaining 6 as evidence of the hammering. Look at the rod bearings for this type of damage.
With that much compression a minimum of 110 octane fuel, 14 to 16 degrees initial, 36 total with it all in by 3500 rpm and that engine will live with either the Forged or Hypertetic pistons. If you want to spray it back the timing down 6 degrees at the hit.
04-23-2008, 12:06 AM
#45
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Based on all of the posts Gadget made I doubt this is a piston or ring problem...
Detonation broke those pistons.
I would bet "93 octane and octane booster" and not knowing where the timing was with over 12 to 1 compression hammered those pistons apart.
I've seen it many times.
Ordering just two pistons is another recipe for disaster, all of those pistons were subject to the same forces. I would look for closed up ring lands in the remaining 6 as evidence of the hammering. Look at the rod bearings for this type of damage.
With that much compression a minimum of 110 octane fuel, 14 to 16 degrees initial, 36 total with it all in by 3500 rpm and that engine will live with either the Forged or Hypertetic pistons. If you want to spray it back the timing down 6 degrees at the hit.
Detonation broke those pistons.
I would bet "93 octane and octane booster" and not knowing where the timing was with over 12 to 1 compression hammered those pistons apart.
I've seen it many times.
Ordering just two pistons is another recipe for disaster, all of those pistons were subject to the same forces. I would look for closed up ring lands in the remaining 6 as evidence of the hammering. Look at the rod bearings for this type of damage.
With that much compression a minimum of 110 octane fuel, 14 to 16 degrees initial, 36 total with it all in by 3500 rpm and that engine will live with either the Forged or Hypertetic pistons. If you want to spray it back the timing down 6 degrees at the hit.
i have a set of speed pro h140cl hyperutectics but one of those was actually melted when i got this motor.
its been boggeling my mind. the H140cl is only supposed to have 9.6:1CR but for some reason one of those was melted.
Im to the point where i want to start over but dont really have the time or money, the reason im stuck with this motor is because i traded a friend for a 383 i built. i wanted this motor because it has bigger heads forged crank 6" H beam rods fully blueprinted block, but turned out to be a headache and a half. i have never had so many problems with a SBC in my life.
04-23-2008, 01:11 AM
#46
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Actually with wet flow testing (Joe Mondello) they have found it better to keep the sharp edges on the piston's. It was true of old, that they thought that the shap edges helped the motor go into detonation faster. With the R&D they have spent trying to find more HP, they have found quite the opposite true.
04-23-2008, 09:37 AM
#47
Normally I'd agree with you 100% (and I still do agree with you about 90%), but this is a known issue with KB pistons. Some years ago, I used to work at Jegs in tech support and anytime someone put an engine together with the KB's and didn't read the instructions, they'd wind up calling in with the "my pistons broke" problem, we'd ask them the ring gap they used and they'd say that they used basically "standard" gaps. They will break the lands (as shown in the photos) every single time.
The compression and pump gas might not be helping matters much though.
By the way, welcome aboard Truckracer. It's always nice to see more knowledgeable people joining us here.
04-23-2008, 12:24 PM
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Actually with wet flow testing (Joe Mondello) they have found it better to keep the sharp edges on the piston's. It was true of old, that they thought that the shap edges helped the motor go into detonation faster. With the R&D they have spent trying to find more HP, they have found quite the opposite true.
Actually I was being sarcastic, thats a good looking shortblock.
I forgot keyboard sarcasim doesn't translate well....
04-23-2008, 12:32 PM
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Normally I'd agree with you 100% (and I still do agree with you about 90%), but this is a known issue with KB pistons. Some years ago, I used to work at Jegs in tech support and anytime someone put an engine together with the KB's and didn't read the instructions, they'd wind up calling in with the "my pistons broke" problem, we'd ask them the ring gap they used and they'd say that they used basically "standard" gaps. They will break the lands (as shown in the photos) every single time.
The compression and pump gas might not be helping matters much though.
By the way, welcome aboard Truckracer. It's always nice to see more knowledgeable people joining us here.
The compression and pump gas might not be helping matters much though.
By the way, welcome aboard Truckracer. It's always nice to see more knowledgeable people joining us here.
And I do agree to an extent about the ring gaps with the KB's. I've fixed several of those for engine customers trying to use them in claimer style motors.
It just seems to me the list of other potential issues is long with this engine. I tend to blame the parts last, machine work second, and the human factor first...
I'm not ******* Mr. Gadget, the learning curve is sometimes expensive & extended. I know, I learn everything the hard way.
04-29-2008, 07:27 PM
#56
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so today i weighed my pistons so i could get my new one's. i figure i might as well measure everything to the T now that i've had so many problems...
long story short. the 2 broken pistions were the wrong size. they measure out 4.030. and my bore size is 4.040. as were the rest of my pistons
what a joke!
long story short. the 2 broken pistions were the wrong size. they measure out 4.030. and my bore size is 4.040. as were the rest of my pistons
what a joke!
