Engine failure after 10hours

[Hydraulica]

Only recently i had my 2.4ltr rebuilt due to an overheating seizure.

The engine builder stripped the powerhead, machined & sleeved the block, new crank, heavy rods, fitted a 7 petal reed set, decked the heads to 35cc & cleaned up the exhaust & ports, rebuilt/re-jetted the carb & Holley red pump.compression on start up 125psi/ cylinder

For the first 5 hours on the water the engine run retard spark & rich jets. 98 Octane pump fuel with 25:1 fuel:oil mix (100 litres/ 25 gallons). Run the engine at a max RPM of approx 3000-3500rpm, with the occasional squirt to 5000rpm. compression test 130psi. water pressure about 15-20kPa & 3500rpm.

After 5 hours running, I returned to the engine builder.
He tested the compression that had increased to 135psi, due to bedding & all look good. Water tested the engine again with the run in jets & timing & checked the compression, still good
The engine builder then rejetted the carbs to decrease fuel & advanced the spark to 23 degrees. Water test after tunning, power has increased. compression tesat all good.


Run the engine for another 4 hours 98 Octane 40:1 fuel:oil mix. Power has increased. Cruising at 4500RPM-5000RPM, & a couple of squirts to 6000rpm.

At 10 hours...cruising at between 4500rpm & 5000rpm instant loss of power buy 1000rpm....and small rattle in motor. switched the motor off & paddled to the ramp.

Pulled the plugs, the right bank was wet & oily, the left bank seemed dry compared to right (dryer coffee coloured type stains on new NGK left plugs). The bottom left cylinder (6,I think) on the plug diode is a mass of what looks like ground aluminium or hardened powder. I have looked in the cylinder head through the plug socket & can see the same...Any suggestions.

Hydraulica

[Fast Fred]

sounds like that cyl leaned over, that powder look, pull the head, have a lookin in thare, then pull it off.:(

[Techno]

15 kPa = 2 psi
20 kPa = 2.9 psi

15 psi = 104 Kpa
20 psi = 139 Kpa.

If this makes sense to you then this is the reason. It might be possible that the rich mixture was keeping the engine cool. Once you went to correct mixture 3 psi just wasn't enough.
If you just made the mistake of kPa for PSI then this isn't it.

kPa --> PSI
* kPa x 0.145 = psi
eg. 100kPa x 0.145 = 14.5psi

PSI --> kPa
* PSI x 6.98 = kPa
eg. 150psi x 6.98 = 1047kPa

Another item I noticed is you rebuilt due to an overheating failure. What caused it and how did you fix it?

[Hydraulica]

Thanks for the reply..

The motor overheated due to a large amount of debris catching around the water intake, causing excessive temps.

During the initial running of the engine over a 3-4 hour period the engine builder compression tested approx 6 times, the engines compression was increasing.


Hydraulica

[The Big Al]

Most of the time when engine runs hot for water cooling restriction it gets the top cyc not the bottom.

Question, was this number 6 the same cyc that was damaged before?

[Hottrucks]

If it got cooked due to a covered water intake it probablly cooked the water impellor ( no water in the pump)
A compression test only tell you whats going on at that minute.... If I add correctly you ran that motor for 9 hours @ 5000 rpm or less....
I would hope your motor rebuilder is going to take care of you if it's a steel sleeve he just replaced at least your only out a piston and it should be a quick repair....

Jeff

[Techno]

What about the 3 psi you were getting? Was it 3 psi or 15-20 psi?