500hp anybody?

[david85]

Why shave the pistons, how close do they come to the crank, if it would fit then I would think that shorter connecting rods would be the way to go. For lower compression, and you would keep the strength of the piston.

Its cheaper to cut pistons down than to have them or conrods made up from scratch. Flatlander ended up learning a few lessons the hard way for the rest of us and from what I know he cut off more than anyone else.

I would also start to wonder how dropping the top flat part of the piston down will start to effect combustion efficiency. Maybe a custom piston with a deeper prechamber dish would be a better option?

Of course, if you lower the top of the piston down, it would allow for slightly more valve lift.

In the case of the turbo diesel that some rangers had, the prechamber was actually shaped so it doubled as valve reliefs. That 2.3L engine actually has a larger prechamber dish in the piston than on a 6.9/7.3. I wonder if such a custom piston could be made to drop compression, increase valve lift and all without changing any of the key rotating/reciprocating parts. Would make for a pretty big wide on the piston, but could it work?

 

[Death85e]

Just as a thought why has no one looked into having a full copper head gasket made to try out on these IDI's ? I mean they are used for high horsepower and high compression gassers so why would they not work for a diesel? If this is one of the weak spots in our IDI's then would that not alleviate that problem?
I also realize that horsepower is nice but it seems to me that the torque that these engines make is one of the primary reasons that we all buy and like them so much.

Not trying to irritate anyone here just trying to learn.

 

[cetanefreek]

everywhere I've seen a full copper gasket develops leaks in one galley or another, O-rings or fire rings would be a better bet, I would like to try O-rings, I've had good luck with them in my cummins.

 

[bike-maker]

I used to build race motors for a living. The big horsepower motors I messed with were blown/alcy motors. They all had O-ring grooves machined into the block and heads, then a stainless o-ring material was pounded into the head. The head gaskets were just a sheet of copper shaped like a standard head gasket. The copper head gaskets were also available in many different thicknesses. From about .025" clear up to .125". I see no reason why this couldn't be done to an IDI. They would seal better, and it would provide a better option for decompression.

 

[cetanefreek]

I used to build race motors for a living. The big horsepower motors I messed with were blown/alcy motors. They all had O-ring grooves machined into the block and heads, then a stainless o-ring material was pounded into the head. The head gaskets were just a sheet of copper shaped like a standard head gasket. The copper head gaskets were also available in many different thicknesses. From about .025" clear up to .125". I see no reason why this couldn't be done to an IDI. They would seal better, and it would provide a better option for decompression.

thats pretty much what we do with the DI diesels, except that we don't use a copper sheet, we just use a stock gasket or a little thicker one, the O-rings I put in my cummins are .011" protrusion into a stock head gasket, it's held up to to 85 psi at 17.2 :1 compression.

 

[7.3_IDI_guy]

Could there be any way to make a stroker 6.9 or 7.3? And these diesels are big blocks and the cranks are extremely heavy. I got to wonderin if there was some way maybe you could put some big block gasser's crank in the and would be a little lighter and would stroke it up or down one. Of course it would take alot of fab work but its something to think about just think about a bored and stroked 7.3 though

 

[cetanefreek]

I don't know that lightening the crank is going to be much benefit or even a good Idea, it might give you more "snap" as in quicker winding engine, but it's not going to affect power output and that's not somewhere I would want to sacrifice strength.

I don't know of any stroker cranks out there, although you could offset grind the rod journals for a little more, maybe .020" more stroke?

 

[sootman73]

remember that with putting "o-rings" in the head or block would mean you would have to have custom ones made as the precups are outside of the cylinder diameter in the head. you would have to have a oring that would have a little nub to go around the precup area too......

 

[7.3_IDI_guy]

Ah it wasjust an idea.. I'm still learning

 

[cetanefreek]

remember that with putting "o-rings" in the head or block would mean you would have to have custom ones made as the precups are outside of the cylinder diameter in the head. you would have to have a oring that would have a little nub to go around the precup area too......

didn't even think of that, I think you could do it to the block, although you would need a CNC machine to do it because it wouldn't be a true circle.

 

[david85]

I don't suppose anyone could comment on my idea to carve valve reliefs in the tops of the pistons? We have a CNC machine that could probably do it with a simple tapered "pocketing" operation.

Once that is done, I think a camshaft could then be custom ground to have more lift.

I have no idea what sort of a difference that could make, but more valve lift and a bigger combustion chamber should help a little. The larger dish in the piston should drop CR and allow more combustion zone for a longer, bigger burn without ruining the basic prechamber operation. Also, since the top flat portion of the piston remains at the same height as stock, you don't have any increased risk of burned or coked up top compression rings.

 

[cetanefreek]

I actually like that idea, it's a way better way to drop compression, that's what I like to do on the cummins engines, open up the bowl. that also creates more combustion chamber turbulence which should lead to better combustion chamber efficiency.

 

[88beast]

ok heres my build as money allows
stock 7.3 turbo
moose pump
twin compounds
arp studs (1.25 times stock torque)
intercooler
type4s logging cam
1900 psi pop injectors
custom intake manifold
psd springs if they fit for stiffness
fully flowing exhaust manifolds and piping
19.5 to one comp
either to start (already do it cause no gps so might as well)
and im considering either injection to start with tipless gps so that itll lower comp more
im gonna look into the dished pistons sounds like a good idea

i have a stroker crank now but its a torque monster not much hp plus the hp is max around 3k and the torque is about 1500 so its a big span

the p/o had it custom made by a local shop i saw the reciept for it but didnt catch the shop and didnt think to ask for reciepts wen i bought it (stupid kid at the time)
but mine is very slow but will pull anything ex 4k in bed 4k in trailer 1200 lb trailer up a 30 degree grade doing 2000 rpm and about 15 mph if i start on grade

maybe thats why my gps will never start it cause the higher comp

byw so far for this project ive aquired
donor motor
stuff to pop test
one of each type injector to test for best pattern
stock turbo thatll ill run with a t3 style turbo both wastegated into each other so one can limit boost or both can

any questions ill try to stop in or you can just pm me
but i plan for 300 and 600 trq

 

[Diesel JD]

Hey David I had never thought about the valve relief area as a way to drop compression. You're thinking this could be done on stock pistons? I suck at math and have less knowledge of how to figure compression ratios. Any idea what your final compression ratio could be if you did what you intended to do? Maybe somebody could donate a used IDI piston and let you try it on one nobody cares about and see how it comes out? The thing I have always been bothered by is that I would like to use the 7.3 turbo rods but these will not bolt to a 6.9 piston and i don't know of any good way to make it happen. I would expect the smaller piston pins to become more of a problem at higher boost levels. For those of us that don't overboost and take good care of our engines I would figure it to never be a problem in a stockish to mildly turned up engine.

 

[88beast]

if youll do one for free ill send you a spare and ill run the numbers to see the changed cr if you wanna do this pm me