Detroit Diesel, breaking cranks, what to do...

[ShaferDiesel]

Well guys, (and gals!) I never though i'd be here, but I'm breaking stuff...

I'm running a 3-53 detroit in a toyota, with twins, and 155mm of fuel. I have the high speed limit on the govorner disabled, but it doesn't like to twist past 3800 without popping and missing, I assume it is valve spring harmonics giving me trouble because if I push it past, it will pick up power again. But that's not my real problem, I can work through that.

A couple weeks ago, I was tuning for a tractor pull, took it out on the road, eased into it in 4th gear to do a timed 30 to 80 mph run, and everything cut loose. It snapped the input shaft on the trans, so I pulled it into the shop and replaced it. The only reason I'm telling you this is it may have something to do with my next problem. Next week, I was doing the same thing, when all hell broke loose again. The crank broke, I knew it, but I drove it back in anyway. Upon teardown i found that it broke at every single rod journal. Is this just a result of snapping the input, and can I keep pusing it with a stock crank, or should I be getting Moldex to do a billet for me.

I actually called around and talked to 5 or 6 different crank builders, and I liked the guys at moldex the best. and it looks like just a tad under 5 grand will get one. I cannot afford it, but if it has to happen it will. Now if I go that route, I am thinking to stroke it, get billet rods, and titanium pushrods and rockers and trying to push 8k rpm. That should also start pushing that big turbo close to it's limits:Cheer:

Sorry this is so rambling and not to the point, but thats just some of the questions and decisions I'm rolling over in my head right now. Thanks ahead of time for any ideas or help.

 

[TMONEYDIESEL]

Input could have weakened it, you dont want titanum pushrods FYI

 

[lenahan05]

Input could have weakened it, you dont want titanum pushrods FYI

other than them being expensive...why not? its stronger than what we sell. and almost half the weight. its been done many times.

 

[lenahan05]

Well guys, (and gals!) I never though i'd be here, but I'm breaking stuff...

I'm running a 3-53 detroit in a toyota, with twins, and 155mm of fuel. I have the high speed limit on the govorner disabled, but it doesn't like to twist past 3800 without popping and missing, I assume it is valve spring harmonics giving me trouble because if I push it past, it will pick up power again. But that's not my real problem, I can work through that.

A couple weeks ago, I was tuning for a tractor pull, took it out on the road, eased into it in 4th gear to do a timed 30 to 80 mph run, and everything cut loose. It snapped the input shaft on the trans, so I pulled it into the shop and replaced it. The only reason I'm telling you this is it may have something to do with my next problem. Next week, I was doing the same thing, when all hell broke loose again. The crank broke, I knew it, but I drove it back in anyway. Upon teardown i found that it broke at every single rod journal. Is this just a result of snapping the input, and can I keep pusing it with a stock crank, or should I be getting Moldex to do a billet for me.

I actually called around and talked to 5 or 6 different crank builders, and I liked the guys at moldex the best. and it looks like just a tad under 5 grand will get one. I cannot afford it, but if it has to happen it will. Now if I go that route, I am thinking to stroke it, get billet rods, and titanium pushrods and rockers and trying to push 8k rpm. That should also start pushing that big turbo close to it's limits:Cheer:

Sorry this is so rambling and not to the point, but thats just some of the questions and decisions I'm rolling over in my head right now. Thanks ahead of time for any ideas or help.

sounds like your guna spend some money. i have a couple questions tho.

-why 8,000rpm in a diesel? thats non-sense.
-titanium pushrods? those are too costly. get your length and cup sizes and diameter of pushrod and call me. i'll send you to a place that will make you a set
-what spring pressure @ seat/nose are you running? could be your popping issue. but its more likely timing too low.
- are you drag racing it? or pulling it? that makes a big diffference if your wanting to stroke the crank or not. most likely your crank broke from vibration. stock may work for you if you have it internlly balanced first. or go billet if you wana spend some $.
- why you wanting rockers? stock ratio not enough? if you want a better rocker use steel if your running high boost and a heavy spring. if your not, then an aluminum should suffice.
- and the "big" turbo being pushed to its limits has nothing to do with rpm. its camshaft and turbine/housing/drive pressure that results in pushing it harder.

overall it sounds interesting to me. hope you dont think im knockin ya, just wanting you to think about what your doing before you waste $. call/pm me anytime if you have any questions. take care.

 

[Bponci]

Do you have the two piece ballancer? Cone and sleeve style.

 

[TMONEYDIESEL]

other than them being expensive...why not? its stronger than what we sell. and almost half the weight. its been done many times.

Eh not really, While TI is lighter, you are lowering the bending frequency. It would also effect the column bending & compressive nature of the rod. You would lose a lot of stiffness since the modulus of the titanium is half of the steel.


TI Is great in bikes etc, and we use them a lot in out Harley motors, but he should stick with either Chromoly, or spend the coin on some nice tool steel pushrods. He would be money ahead.

 

[ShaferDiesel]

Sorry I didn't get back to this sooner, I've been at the Lyons NTPA super national pull all afternoon!
This is exactly the feedback I needed. Lenahan, it doesn't sound like you're knockin me at all. I'm just a newbe and don't know what the heck I'm doing...

-why 8,000rpm in a diesel? thats non-sense.

Why? I have already built one that runs consistantly to 5500 for one of my customers, why not another 2500?

-titanium pushrods? those are too costly. get your length and cup sizes and diameter of pushrod and call me. i'll send you to a place that will make you a set

I do want to call you, but my pushrods are only about 4" long, already steel, and are threaded on both ends. There is also a spring on top of the roller folower that helps return the rocker/pushrod assy. here is a drawing of the top of the pushrod and it's attachment to the rocker.

So in my head, bending is not near the problem as it is in say a cummins, but weight/inertia is the main concern. At even just 5500 the valve train is operating at the same speed a 4-stroke would be at 11000 rpm.

-what spring pressure @ seat/nose are you running? could be your popping issue. but its more likely timing too low.

34 lbs, but remember the spring pack on the lifter does the work of returning the rocker/pushrod/lifter

- are you drag racing it? or pulling it? that makes a big diffference if your wanting to stroke the crank or not. most likely your crank broke from vibration. stock may work for you if you have it internlly balanced first. or go billet if you wana spend some $.

I have been pulling, and that is its main purpose, but want to try some drag racing as well.

- why you wanting rockers? stock ratio not enough? if you want a better rocker use steel if your running high boost and a heavy spring. if your not, then an aluminum should suffice.

Again, weight.

- and the "big" turbo being pushed to its limits has nothing to do with rpm. its camshaft and turbine/housing/drive pressure that results in pushing it harder.

Yes I know, but engine RPM also plays a huge factor in turbo sizing/performance. You build a turbo to run at one RPM, and then change the engine so you can run faster, and all of the suden the turbo setup is all wrong.

I also have a machine shop as part of my business, and have had a little experiance screwing with Ti, not fun! but Ti rockers and pushers are not out of my skill range to produce. So maybe it's not worth it, thats just why I was thinking that way. These engines are a lot different every way you look at them.

Not dissing your input at all, I'm listning carefully!

 

[TMONEYDIESEL]

The weight on the pushrod end isnt as important as the weight on the spring & retainer side. Thats where you want to lighten it up. In the pushrod side you want to go as sttong as possible. Thats why most go to a tool steel rod, BUT with yours only being 4" long you could probably get away with a titanium piece.

 

[lenahan05]

heres my oinion for what its worth.

1.) your going to have to decide what your wanting to do with it. drag or pull.
my opinion is build it for a pullng engine. lighten up everything as much as you can on the valve side of the engine. dont concern yourself with the pushrod side of the engine weights. flex is way more of a concern than weight IMO. use a dished titanium intake and a dished inconel exhaust valve. it will surpise you.

2.)all those rpms are not needed. its hard on valvetrain that size and it wont make power up in those rpm ranges. rpms will be handy in drag racing to ditch the torque off the line in the bigger rpms. if you feel you need to turn it that hard, have at it. but diesel fuel doesnt burn fast enough in those type of rpms. its just not efficient above 6000rpm on fuel only.

3.) spend your money on the air side of your setup and youll be way ahead. forget the titanium ideas. very minimal gains in hp/torque. spend as much as you can on the latest and greatest turbo development and lighten your valves/retainers/locks as much as you can. the rest of the details are minimal.

4.) when you decide what you wana do on a crank, add some stroke. youll pick up some torque and swept volume. bigger bore wont do much for you if im picturing this engine correctly in my mind.

5.) those pushrods shouldnt be to hard to make being that short. get ahold of me whenever and i'll point you in the right direction where to get them made.

im still a little confused on your engine. does it have an intake valve? reed? or is the intake event started/stopped by the piston?

 

[Joesixpack]

heres my oinion for what its worth.

1.) your going to have to decide what your wanting to do with it. drag or pull.
my opinion is build it for a pullng engine. lighten up everything as much as you can on the valve side of the engine. dont concern yourself with the pushrod side of the engine weights. flex is way more of a concern than weight IMO. use a dished titanium intake and a dished inconel exhaust valve. it will surpise you.

2.)all those rpms are not needed. its hard on valvetrain that size and it wont make power up in those rpm ranges. rpms will be handy in drag racing to ditch the torque off the line in the bigger rpms. if you feel you need to turn it that hard, have at it. but diesel fuel doesnt burn fast enough in those type of rpms. its just not efficient above 6000rpm on fuel only.

3.) spend your money on the air side of your setup and youll be way ahead. forget the titanium ideas. very minimal gains in hp/torque. spend as much as you can on the latest and greatest turbo development and lighten your valves/retainers/locks as much as you can. the rest of the details are minimal.

4.) when you decide what you wana do on a crank, add some stroke. youll pick up some torque and swept volume. bigger bore wont do much for you if im picturing this engine correctly in my mind.

5.) those pushrods shouldnt be to hard to make being that short. get ahold of me whenever and i'll point you in the right direction where to get them made.

im still a little confused on your engine. does it have an intake valve? reed? or is the intake event started/stopped by the piston?

Young grasshopper, its a 2 cycle detroit. Likely the last of those were built well before you were born....LOL

 

[scat]

If i can remember right but the air is entered in a chamber like a 2 stoke but the exhaust is relived using valves in the head. The Pushrods control the exhaust valves and the Injectors. Correct me if im wrong.

Are you still running a supercharger on the engine or only relying on the turbos?

 

[lenahan05]

Young grasshopper, its a 2 cycle detroit. Likely the last of those were built well before you were born....LOL

young grasshopper not new to 2 stroke engine...just new to detroit antiques.
maybe old grasshopper can answer my question?

 

[lenahan05]

If i can remember right but the air is entered in a chamber like a 2 stoke but the exhaust is relived using valves in the head. The Pushrods control the exhaust valves and the Injectors. Correct me if im wrong.

QUOTE]

chamber? ive never read about detroits but the one i seen years ago had a roots blower of some sort on it i thought. i assumed the air entered a hole at BDC in side of the block. some engines also have a valve thats actuated. and ive seen reeds also. im not sure i can see a chamber on a two stroke but ya learn something new everyday. maybe old grasshopper can enlighten us young hopgrappers.

 

[scat]

marinediesels.co.uk The Two Stroke Diesel Engine History and Introduction

Basic principal pretty much.

 

[Lightman46]

The two-stroke Detroit's will not run without a roots blower. The blower serves two purposes provides pressure to remove the exhaust and give fresh air for intake, intake comes in the lower side of the cylinder, The exhaust valves are open at the same time as the intake stroke and the pressure from the roots blower removes the exhaust gas.

 

[YOUNG GUNS15]

2 stroke diesels are a complete different animal from your gas powered 2 stroke chainsaw LOL

I love it when people ask where the reed valves are and why they have "intake" valves.

 

[ShaferDiesel]

Ok, really young grasshopper help you out here!

This is where the air goes in

There is a roots blower that pressurizes the airbox around the intake ports. the airbox is totally seperate from the crankcase, so the engine can be pressure lubed just like any other 4 stroke

They have four exhaust valves, and an exhaust manifold that would make any cummins jelous. They are one of the easiest engines to get to flow extreme amounts of air.

 

[ShaferDiesel]

Young grasshopper, its a 2 cycle detroit. Likely the last of those were built well before you were born....LOL

Hey, Old grasshopper, you can still buy a new one, and if the president doesn't tank our economy, the mil has contracts with Detroit until 2053 for lots more 2 strokes.

 

[Joesixpack]

I suppose they'd have an ongoing contract with the military to keep all that antiquated crap going.

Other than the super large Marine 2 strokes, there's not much out there using 2 stroke any more in a Diesel. Emissions regulations makes it just about impossible.

 

[RonA]

I suppose they'd have an ongoing contract with the military to keep all that antiquated crap going.

Other than the super large Marine 2 strokes, there's not much out there using 2 stroke any more in a Diesel. Emissions regulations makes it just about impossible.

Their whisper quiet sound levels at full throttle make them ideally suited to generator use in Canada. That's why they say, "eh" all the time.