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Discussion Starter #1
How much compression is to much to spray 3 systems???? Thanks
 

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It is my understanding that higher compression is not an issue, but rather it just narrows the tuning window on n20. I have almost 15:1 compression on my 582. When in doubt, take another couple of degrees out, and read the plugs from there.
 

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also cyl pressure/cam specs play into it.
 

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fulton knows how to tune and most of his big engines go to guys that really have a handle on it so they can get away with more and if they burn a piston its no big deal to them.but for just a part time hobby racer the larger tuning window with lower compression costs us less in the long run.thats just one way to look at it.
 

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Discussion Starter #10
It is my understanding that higher compression is not an issue, but rather it just narrows the tuning window on n20. I have almost 15:1 compression on my 582. When in doubt, take another couple of degrees out, and read the plugs from there.
Not true!!! With a lot of compression you can simply only stuff so much nitrous into the cylinder. My current combo has 16+. 1 !!!! On two systems its awesome, but soon as I try and light 3 its a different ballgame. I was told that 13.1 to 14.5 is great for 3 plus systems but 15+.1 and up is only good for 2 systems. Steve Johnson you out there????
 

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The nitrous guy
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Not really about static compression, but more about "dynamic compression", which is actually what the motor sees when it's running. Static compression, quench and cam timing, ALL effect the dynamic compression. On a big block, I typically don't like to see more than 14.5, although I have had some Pro-Mod customers with over 15 and had no issues. Some of the motors we had with over 15, when we freshened them, we lowered the compression .5 to 1 point and saw no decrease in power and the tuning window was larger. Some of it also depends on the head. To get lots of compression in a conve headed motor, generally means huge domes. Not the best thing for flame travel and a clean burn. So if I had to pick a number, I would say 13.5 max on a conv motor and 14.5 on a spreadport.

Monte
 

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Discussion Starter #13
Not really about static compression, but more about "dynamic compression", which is actually what the motor sees when it's running. Static compression, quench and cam timing, ALL effect the dynamic compression. On a big block, I typically don't like to see more than 14.5, although I have had some Pro-Mod customers with over 15 and had no issues. Some of the motors we had with over 15, when we freshened them, we lowered the compression .5 to 1 point and saw no decrease in power and the tuning window was larger. Some of it also depends on the head. To get lots of compression in a conve headed motor, generally means huge domes. Not the best thing for flame travel and a clean burn. So if I had to pick a number, I would say 13.5 max on a conv motor and 14.5 on a spreadport.

Monte
Thanks Monte!!! Its a 14.5 Sonny's non conv. headed BBC. So far I havent had any problems tuning the 2 systems!!! Its when I turn on the 3rd is the problem, it starts popping and banging through the exhaust!!!! Dont have chance to read the plugs on 3 cause it instantly starts popping so I lift.
 

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Thanks Monte!!! Its a 14.5 Sonny's non conv. headed BBC. So far I havent had any problems tuning the 2 systems!!! Its when I turn on the 3rd is the problem, it starts popping and banging through the exhaust!!!! Dont have chance to read the plugs on 3 cause it instantly starts popping so I lift.
Sounds like possibly a tune up issue ??? Missing the fuel and or the timing..

Sorry for the slow reply, was just away from the computer all weekend..

As most said, I shoot for around 13.5 to 1 in most cases as well. But as Monte also pointed out there are more things involved then just that number. Thanks, SJ
 

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The nitrous guy
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Popping and banging, could be a number of things, but usually more electrical than tune up. The cylinder pressure, could just be putting the fire out. You need a tight gap, .015 or so. Also a weak coil can do that, as well as rotor phase off the mark.

Be advised though, most Sonny's head are pretty damn timing sensitive. Not saying they won't work, they will, just need some chamber mods to spray large amounts. Sonny's stuff, is geared more for N/A, so in a nitrous app, you need to slow the chamber down.

Monte
 

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the chamer mod will knock some compression out of it too

my 14.5* are on their way to curtis for the chamber mod, he said it will take a couple cc's
 

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Discussion Starter #19 (Edited)
Hey guys I forgot to mention one thing. I have an aluminum Brodix block that is not o-ringed. I tried a different set of head gaskets this past season. When I pulled the engine down I found that the cylinders were crossing over to each other because the Cometic MLS gasket was leaking. I decided to leak it down hot before calling it a season. The engine only had 35 passes on it with two systems max. I had 3 or 4 cylinders at 60% leak and the rest were at 30% to 40% leak. Had a shit ton of reversion in the intake side of the head and into the intake runners. I am switching back to the black 1077 Fel Pro MLS gaskets. I am having the heads and block machined just enough to straighten them out and we are also going to machine a little off the pistons. This is probably a stupid question but could some or all of the problem have been that the head was not properly sealed to the block?
 

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Discussion Starter #20
Hey guys I forgot to mention one thing. I have an aluminum Brodix block that is not o-ringed. I tried a different set of head gaskets this past season. When I pulled the engine down I found that the cylinders were crossing over to each other because the Cometic MLS gasket was leaking. I decided to leak it down hot before calling it a season. The engine only had 35 passes on it with two systems max. I had 3 or 4 cylinders at 60% leak and the rest were at 30% to 40% leak. Had a shit ton of reversion in the intake side of the head and into the intake runners. I am switching back to the black 1077 Fel Pro MLS gaskets. I am having the heads and block machined just enough to straighten them out and we are also going to machine a little off the pistons. This is probably a stupid question but could some or all of the problem have been that the head was not properly sealed to the block?
OK where is Monte and Steve???????
 
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