Open stroker animal issue

spincycle

spincycle

Member
Had mine freshened, builder put it on dyno for a pull, let it warm up a bit, cracked throttle a couple times, then PING....pulled it back apart, the billet rod SPLIT down the middle starting with the wrist pin end, 2 vents on valve cover, 1 pc valve vent on front top of billet side cover and 2 additional vent tubes from back of billet side cover....told maybe source of failure was possibly due to "vapor lock"... anyone ever hear of this, or know of any other possible causes? It's back together, trying to gain knowledge to avoid it happening again....thx!
 
Rod damage sounds like it hydro locked. But correct me if I’m wrong, hydro locking and catastrophic failure only happens when you are initially starting the engine like on a dragster or sprint car when it’s not running right? I’m no expert on this, and have been wanting to ask this for awhile. Someone awhile back somewhere (I think it was Carlson) talked about animals and compression/fuel at TDC, breaking components from it and hydro/vapor locking. @CarlsonMotorsports
 
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Hydro lock could be possible . Liquid fills cylinder till its enough volume to prevent it compressing and rolling over . Was it a new rod ?
Wap wap quick on the throttle may draw in enough fuel too do it .
Though I would be skeptical on that .
Especially with it already running .
 
Hydro lock would normally not happen if the engine is running.
YES it does happen in fuel dragsters, But they are pumping 4 gallons of fuel per second. If a cylinder misfires, yes it will blow the head and everything else off in a nitro fuel dragster.
My guess would be something else was the problem. Possibly ? a defect in the rod. But unlikely to be hydro lock.
In a stroker Animal it is critical to watch your piston pop up! Especially if you bored it out Say to .030 over and used a thin head gasket. But I can't think of any situation that would split the rod down the middle. I personally have never seen that happen! Seen many bent, broken, bearing failures, crank issues, failures. but not like you describe.
Maybe Brian will jump in here and teach us something.
 
I would have to say the only damage gas pressure inside the block would cause is blown out side cover gaskets, the pressure in the block is tiny compared to the pressures inside the cylinder. Hydro lock can happen as others have said if you fill a cylinder with fuel when starting or fill a cylinder with coolant, or the dragster example listed above, and yes it does happen. I have to agree with One Fast Kart that hydro locking a running kart engine would be very unlikely.
 
I would want to know what the ignition timing was set at (using a degree wheel) the actual measured compression ratio and what other damage was done?
What fuel?

Here's one i found in a motor someone sent me to rebuild.

1615595613929.png
 
Jimbo said:
I would want to know what the ignition timing was set at (using a degree wheel) the actual measured compression ratio and what other damage was done?
What fuel?

Here's one i found in a motor someone sent me to rebuild.

View attachment 14496
Click to expand...
The rod that came out of the motor looks nearly like this except the wrist pin end is still intact...pretty much split right down the middle, I don't know the exact specs on the build....the "vapor lock" thing was possibly brought up as a possible cause when my builder spoke to the guys at ARC...not upset with anyone, just trying to learn as to try to avoid the same thing happening ever again...😁
 
Was it a new rod ?
If you inspect it real well in good light with a magnifying glass you may be able to see tell tale signs . Old break will be dull, new will be bright and shinny .
 
flattop1 said:
Was it a new rod ?
If you inspect it real well in good light with a magnifying glass you may be able to see tell tale signs . Old break will be dull, new will be bright and shinny .
Click to expand...
Entire bottom end assembly had one race on it....was in the shop for some cylinder head/fuel delivery upgrades and was on the dyno when it broke...
 
I can't buy the "vapor lock" (hydro lock) story. If it had that much fuel going into it I can't believe it would even run.
I would still like to know what the timing was set at and the compression ratio. Ask your engine builder for those answers.
You can get some extremely high cylinder pressures with too much timing. Add some pre ignition or detonation and watch the parts fly.
You sure don't want this to happen again.
What kind of cylinder head / fuel delivery upgrades?
 
Jimbo said:
I can't buy the "vapor lock" (hydro lock) story. If it had that much fuel going into it I can't believe it would even run.
I would still like to know what the timing was set at and the compression ratio. Ask your engine builder for those answers.
You can get some extremely high cylinder pressures with too much timing. Add some pre ignition or detonation and watch the parts fly.
You sure don't want this to happen again.
What kind of cylinder head / fuel delivery upgrades?
Click to expand...
I'll talk to my builder and will get back to you on your questions...before the upgrade it was more of a very limited modified....opened the intake port on the stock animal head to 1.000 and put a 28mm alky tillotson carb on it, and went to 32/28 valves and heavy duty dual valve springs, it's got a stock 5hp flathead crank, billet rod and big bore piston (that's the stuff that had 1 show on it)....😉
 
If the cylinder "hydrauliced," it would have been from NOT starting -- this doesn't happen while the engine is running.
The cylinder is filled with excess fuel, then compressed when trying to start. Common damage is a bent connecting rod or bent wrist pin. When it does ignite, those bent parts break -- which "could" have happened...but I am leaning toward something else being the cause here. Your builder should be able to perform an "autopsy" when disassembling and have a better idea what caused the damage. If the rod bent, then collided with other parts (bottom of cylinder, cam, etc) then broke vertically is a possibility -- and will be easily identified with rub marks where the collision occurred.
Way too much timing (ie spark knock & detonation) could be the culprit. Only your builder will know for sure.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
32 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
CarlsonMotorsports said:
If the cylinder "hydrauliced," it would have been from NOT starting -- this doesn't happen while the engine is running.
The cylinder is filled with excess fuel, then compressed when trying to start. Common damage is a bent connecting rod or bent wrist pin. When it does ignite, those bent parts break -- which "could" have happened...but I am leaning toward something else being the cause here. Your builder should be able to perform an "autopsy" when disassembling and have a better idea what caused the damage. If the rod bent, then collided with other parts (bottom of cylinder, cam, etc) then broke vertically is a possibility -- and will be easily identified with rub marks where the collision occurred.
Way too much timing (ie spark knock & detonation) could be the culprit. Only your builder will know for sure.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
32 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Click to expand...
It's got an adjustable timing billet flywheel, maybe it slipped after it was started, maybe when the throttle was hit a couple times.... and timing advanced excessively? Thx!
 
Jimbo said:
I can't buy the "vapor lock" (hydro lock) story. If it had that much fuel going into it I can't believe it would even run.
I would still like to know what the timing was set at and the compression ratio. Ask your engine builder for those answers.
You can get some extremely high cylinder pressures with too much timing. Add some pre ignition or detonation and watch the parts fly.
You sure don't want this to happen again.
What kind of cylinder head / fuel delivery upgrades?
Click to expand...
Head came off a different ltd mod engine, it had been milled down some unknown amount, so builder didn't check compression, timing set at about 34-35 degrees, crank was lapped and torqued down without a key, crank end showed no signs of slippage...🧐
 
spincycle said:
Entire bottom end assembly had one race on it....was in the shop for some cylinder head/fuel delivery upgrades and was on the dyno when it broke...
Click to expand...
The bottom end had one race and you changed the head carb combination .
No work on the bottom end ?
Thickness of the head gasket , pop up and head to piston clearance are things that could be in play .
 
Well, it sure could have been any of those things, I have to take full responsibility for it, we got it back together, took it to the maloofa race at Emma Mo a couple weeks ago and won the open class feature with it...and ran fastest laps I've ever ran there...😁
 
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