Just another "impossible" build
Lead Driver
Joined: Jan 2006
Posts: 6,267
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The little air cooled diesel in my go kart project has a lever on top, and I believe it holds the exhaust valve open for 1 revolution, so that the starter can get some momentum to turn it over through a compression stroke.
As for the starting issue, maybe an air intake grid heater off a cummins?
As for the starting issue, maybe an air intake grid heater off a cummins?
Posting Guru
Joined: Feb 2013
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If you plug it in all night it still won't start with out glow plugs or starting fuild.
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Senior User
Joined: Jun 2012
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yep I've played with the timing, it had new injectors when it was rebuilt, Put a new ip on it thought that might help. new glow plugs. It only uses oil when pulling hard and it has very little blow-by.
If you plug it in all night it still won't start with out glow plugs or starting fuild.
If you plug it in all night it still won't start with out glow plugs or starting fuild.
Lead Driver
Joined: Apr 2008
Posts: 6,945
Likes: 13
huh, mine wont start without help if its 100* out lol. My dads will eventually if its 80 or so, but you have to crank a WHILE
But my point is i guess, i know two guys with 18:1 or less and both starts just fine with GPs
But my point is i guess, i know two guys with 18:1 or less and both starts just fine with GPs
Postmaster
Joined: Aug 2010
Posts: 2,554
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From: Northern Arizona
Thanks, Racin', for taking the time to type up that explanation. Very good cam info., and very much appreciated.
Mike, Actually, the big thing to bleeding off compression is the intake valve being open longer. Overlap has very little to do with "bleeding" compression, because 9 times out of 10 (thats conservative) exhaust pressure is going to be more than intake pressure, and that works the opposite way of bleeding compression off... A cam with very little overlap and an intake event with decent duration and a late ICL is going to bleed compression off. Ill compare the Stock cam, The R&D, and The J2 below (Id toss the typ4 in there as well, but russ hasent given me the specs yet):
The stock cam has 37* of total overlap (-27*@.050"), and the intake valve stays open for 42* after bottom dead center. It effectively stays open for 7* after BDC at .050", which is a good lift for dynamic measurement.
The R&D cam is 56* of total overlap (-24*@.050"), and the intake valve stays open for 52* after bottom dead center. It effectively stays open for 21* after BDC at .050"...
The J2 cam is 56* of total overlap (-12*@.050"), and the intake valve stays open for 74* after bottom dead center. It effectively stays open for 32* after BDC at .050"...
Putting these together... The further the intake stays open after BDC, the more compression is bled off. Reversion happens when there is too much overlap at too little flow (read:RPM or boost)... The stock cam doesnt have much total overlap, but has as much dynamic overlap as the R&D (which is negative anyway, meaning both valves overlap for less than 0* of duration when the valves are open to .050" of lift...)... The J2 cam has about as much total overlap as the R&D, but has more dynamic overlap at .050", meaning more chance for reversion at lower RPM's, but when higher RPM's and boost are achieved, there is more cylinder filling, and therefore more power.... This just covers the intake side though, there is more as far as the exhaust sides are concerned...
As far as the TYP4 cam is concerned, the best I can do with the knowledge I have of it, is that it increases lower end cylinder filling by increasing duration on the intake side, but maintaining stockish lifts and timing events as much as possible... This is why it works great in low boost and N/A situations, there is no exhaust pressure inhibiting cylinder filling, and the extra filling it gets from the intake event makes a little more torque lower in the RPM range.
Basically it coems down to where you want your cam to perform... The stocker is a good all around cam for everyhing, the TYP4 is better than the stocker at low RPM, the R&D is great for engines that spend their time boosting 10-20psi while doing work, and the J2 is great for WOT/Higher RPM/higher boost situations while doing work... They all have their place...
The stock cam has 37* of total overlap (-27*@.050"), and the intake valve stays open for 42* after bottom dead center. It effectively stays open for 7* after BDC at .050", which is a good lift for dynamic measurement.
The R&D cam is 56* of total overlap (-24*@.050"), and the intake valve stays open for 52* after bottom dead center. It effectively stays open for 21* after BDC at .050"...
The J2 cam is 56* of total overlap (-12*@.050"), and the intake valve stays open for 74* after bottom dead center. It effectively stays open for 32* after BDC at .050"...
Putting these together... The further the intake stays open after BDC, the more compression is bled off. Reversion happens when there is too much overlap at too little flow (read:RPM or boost)... The stock cam doesnt have much total overlap, but has as much dynamic overlap as the R&D (which is negative anyway, meaning both valves overlap for less than 0* of duration when the valves are open to .050" of lift...)... The J2 cam has about as much total overlap as the R&D, but has more dynamic overlap at .050", meaning more chance for reversion at lower RPM's, but when higher RPM's and boost are achieved, there is more cylinder filling, and therefore more power.... This just covers the intake side though, there is more as far as the exhaust sides are concerned...
As far as the TYP4 cam is concerned, the best I can do with the knowledge I have of it, is that it increases lower end cylinder filling by increasing duration on the intake side, but maintaining stockish lifts and timing events as much as possible... This is why it works great in low boost and N/A situations, there is no exhaust pressure inhibiting cylinder filling, and the extra filling it gets from the intake event makes a little more torque lower in the RPM range.
Basically it coems down to where you want your cam to perform... The stocker is a good all around cam for everyhing, the TYP4 is better than the stocker at low RPM, the R&D is great for engines that spend their time boosting 10-20psi while doing work, and the J2 is great for WOT/Higher RPM/higher boost situations while doing work... They all have their place...
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Posting Guru
Joined: Feb 2013
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If it is 20 or below even with good glow pulgs it is hard to start un less it has been pluged in for a few hours.
My other truck will start around 0 with out being pluged in, but it takes some cranking and you have to cycle the gps twice.
I'm going to to replace the pistons when I get the chance not matter what.
Lead Driver
Joined: Apr 2008
Posts: 6,945
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yep I have a carter rotery pump on it It will start on easily when it is 40+ if the gps are working. so I don't have an air problem, I used the truck mostly in the winter time so you can see why I don't like it.
If it is 20 or below even with good glow pulgs it is hard to start un less it has been pluged in for a few hours.
My other truck will start around 0 with out being pluged in, but it takes some cranking and you have to cycle the gps twice.
I'm going to to replace the pistons when I get the chance not matter what.
If it is 20 or below even with good glow pulgs it is hard to start un less it has been pluged in for a few hours.
My other truck will start around 0 with out being pluged in, but it takes some cranking and you have to cycle the gps twice.
I'm going to to replace the pistons when I get the chance not matter what.
Posting Guru
Joined: Feb 2013
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There just stock 30 over that the machnie shop guy took 050. off the top, he didn't touch the valve releave, right now they only have 7 or 8 thouand miles on them. I don't know when I will get it done it a cash flow problem. I want to rebuild my other one first. So it might be this time next year.
IF I remember that you want them all you would have to do is pay for the shipping and there yours
IF I remember that you want them all you would have to do is pay for the shipping and there yours
Posting Guru
Joined: Feb 2013
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How did you come up with that? I was told when I did this that .010 was one compression point. I was going for 17:1 The block was decked .009
when I try this again I'm going for 20 to 1 I was told that hyper-max sells a set, but I havent called them yet.
when I try this again I'm going for 20 to 1 I was told that hyper-max sells a set, but I havent called them yet.
Lead Driver
Joined: Apr 2008
Posts: 6,945
Likes: 13
There just stock 30 over that the machnie shop guy took 050. off the top, he didn't touch the valve releave, right now they only have 7 or 8 thouand miles on them. I don't know when I will get it done it a cash flow problem. I want to rebuild my other one first. So it might be this time next year.
IF I remember that you want them all you would have to do is pay for the shipping and there yours
IF I remember that you want them all you would have to do is pay for the shipping and there yours
Stock .030" over? Please clarify.. what brand are they?
Short of doing math im going to say youre nowhere near 16:1, more like 19:1