help my engine blew up
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Joined: Mar 2006
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From: WY
Also boring the cylinders out isn't going to change your compression ratio, as its the ratio of BDC volume to TDC volume so that ration won't change.
Just getting technicle here but the compression ratio will change with bigger pistons. there is now more volume from bottom to top now!
the reason that the compretion is not any higher is that the rist pin in moved slightly up causing the piston to be slightly lower in the bore causing the same ratio between stock pistons and .010,.020,.030 exc.
Just getting technicle here but the compression ratio will change with bigger pistons. there is now more volume from bottom to top now!
the reason that the compretion is not any higher is that the rist pin in moved slightly up causing the piston to be slightly lower in the bore causing the same ratio between stock pistons and .010,.020,.030 exc.
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From: oakdale, california
Originally Posted by apwatson50
I would only bore the amount needed to make that cylinder good again. You can only take so much material out so in case you need to bore again in the future only take out what you need. Of course you will need to bore all the cylinders the same and use the same pistons. Get all your parts from cummins, they can get you .10, .20, .30 over pistons i'm sure.
Lowering compression in itself isn't going to give you more power, neither is boring your cylinders out as big as you can go. Many of the high high HP guys will lower their compression ratio so that when they run higher manifold pressures so they can inject more fuel they will keep their peak in cylinder pressures down. This helps save the head gasket. This is my take on the whole thing. The problem I have with lowering your compression ratio too much is that when it gets cold the engine will have a much harder time starting. You don't want it to start like a chevy do you? lol You can also get thicker head gaskets to lower your compression.
Also boring the cylinders out isn't going to change your compression ratio, as its the ratio of BDC volume to TDC volume so that ration won't change.
The high HP guys all basically run stock internals, maybe the 1000+hp guys have stuff special made for them but stock internals are good for 600+hp. A cam would help, but even at 600hp I don't think people really run a block girdle or anything.
So basically if you have a block that only needs one cylinder bored .10 over get all the cylinders bored .10 over and get the matching pistons from cummins.
Lowering compression in itself isn't going to give you more power, neither is boring your cylinders out as big as you can go. Many of the high high HP guys will lower their compression ratio so that when they run higher manifold pressures so they can inject more fuel they will keep their peak in cylinder pressures down. This helps save the head gasket. This is my take on the whole thing. The problem I have with lowering your compression ratio too much is that when it gets cold the engine will have a much harder time starting. You don't want it to start like a chevy do you? lol You can also get thicker head gaskets to lower your compression.
Also boring the cylinders out isn't going to change your compression ratio, as its the ratio of BDC volume to TDC volume so that ration won't change.
The high HP guys all basically run stock internals, maybe the 1000+hp guys have stuff special made for them but stock internals are good for 600+hp. A cam would help, but even at 600hp I don't think people really run a block girdle or anything.
So basically if you have a block that only needs one cylinder bored .10 over get all the cylinders bored .10 over and get the matching pistons from cummins.
thanks, and do you know where i can get a cam, do i just call up cummins and order the parts straight from them? and do they have bigger cams? also if i lower my compression, how much should i lower it? thanks
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Joined: Mar 2003
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From: New Holland, PA
It's common practice to bore one cylnder on these engines in order to repair it cheaply. Works OK, although it's not ideal. Have you torn yours apart yet to find out what died?
Get a cam from one of the performance shops. The Helix II from F1 Diesel is supposed to be really good.
If you're planning on big injectors and lots of boost, you can drop the compression. Don't go below 16:1. Keep in mind it will not be as powerful with the stock fueling.
Get a cam from one of the performance shops. The Helix II from F1 Diesel is supposed to be really good.
If you're planning on big injectors and lots of boost, you can drop the compression. Don't go below 16:1. Keep in mind it will not be as powerful with the stock fueling.
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From: oakdale, california
Originally Posted by wannadiesel
It's common practice to bore one cylnder on these engines in order to repair it cheaply. Works OK, although it's not ideal. Have you torn yours apart yet to find out what died?
Get a cam from one of the performance shops. The Helix II from F1 Diesel is supposed to be really good.
If you're planning on big injectors and lots of boost, you can drop the compression. Don't go below 16:1. Keep in mind it will not be as powerful with the stock fueling.
Get a cam from one of the performance shops. The Helix II from F1 Diesel is supposed to be really good.
If you're planning on big injectors and lots of boost, you can drop the compression. Don't go below 16:1. Keep in mind it will not be as powerful with the stock fueling.
SWEET!! thanks for the help with the compression ratio and cam, what is the compression ratio on the stock pistons, and yes i plan to put in bigger injectors an old smokey fuel pin and a 3200 or 4000rpm governor spring, and of course 60lb springs if i go with the 4000 spring. thank you much
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Joined: Sep 2004
Posts: 4,053
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From: Tijeras, New Mexico, 7,000ft up
Originally Posted by wannadiesel
It's common practice to bore one cylnder on these engines in order to repair it cheaply. Works OK, although it's not ideal. Have you torn yours apart yet to find out what died?
Get a cam from one of the performance shops. The Helix II from F1 Diesel is supposed to be really good.
If you're planning on big injectors and lots of boost, you can drop the compression. Don't go below 16:1. Keep in mind it will not be as powerful with the stock fueling.
Get a cam from one of the performance shops. The Helix II from F1 Diesel is supposed to be really good.
If you're planning on big injectors and lots of boost, you can drop the compression. Don't go below 16:1. Keep in mind it will not be as powerful with the stock fueling.
I would run a very fast ramp cam, but it would require mushroom or roller lifters....
Adminstrator-ess
Joined: Mar 2003
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From: New Holland, PA
Cam marketers are very secretive about their specs. The Helix II does have more lift and duration than stock, but they ain't saying how much. To give you an idea about how aggressive the cam is compared to other performance cams, the usual "60 psi" valve springs are not good enough. You need special beehive springs to run the Helix II.
Uh, Mark? We already have mushroom tappets...
Uh, Mark? We already have mushroom tappets...
Registered User
Joined: Sep 2004
Posts: 4,053
Likes: 135
From: Tijeras, New Mexico, 7,000ft up
Originally Posted by wannadiesel
Cam marketers are very secretive about their specs. The Helix II does have more lift and duration than stock, but they ain't saying how much. To give you an idea about how aggressive the cam is compared to other performance cams, the usual "60 psi" valve springs are not good enough. You need special beehive springs to run the Helix II.
Uh, Mark? We already have mushroom tappets...
Uh, Mark? We already have mushroom tappets...
Are there any dyno numbers our there? I would love to know the difference it makes.
Thread Starter
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Joined: Apr 2006
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From: oakdale, california
hey guys, got the head off and WOW!!!!! 
what the 
#$@% happened!!??? 
the third piston back from the front is toast, it looks like it got super hot and then shattered, my valves had piston material melted all over them and they would open by pushing on the valve springs, like i was able to on all the other springs. today im going to try and get some pics of the head and piston for yall to see, also the exhaust port from that piston on the exhaust manifold looked all aluminized and the same on the head port. almost like my engine was trying to use pieces of my piston to use as fuel
what the #$@% happened!!??? the third piston back from the front is toast, it looks like it got super hot and then shattered, my valves had piston material melted all over them and they would open by pushing on the valve springs, like i was able to on all the other springs. today im going to try and get some pics of the head and piston for yall to see, also the exhaust port from that piston on the exhaust manifold looked all aluminized and the same on the head port. almost like my engine was trying to use pieces of my piston to use as fuel
Thread Starter
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Joined: Apr 2006
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From: oakdale, california
hey i have pics of everything but haven't figured out how to put them on yet, i computer dumb , any ways i haven't looked at the cylinder wall yet i was going to go hand crank the engine after i got these pictures on, the piston is at the very top right know so i couldn't see the wall.
, any ways i haven't looked at the cylinder wall yet i was going to go hand crank the engine after i got these pictures on, the piston is at the very top right know so i couldn't see the wall.
SO WHAT DO YOU ALL THINK IS THE PISTON STILL GOOD?