What would cause a carbureted 12A to seize with no warning?
02-05-06, 06:27 PM
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What would cause a carbureted 12A to seize with no warning?
My Abomination (rotary powered Spitfire) seized the engine today. 
A little background: it's a '82 or '83 12A. I bought the car it came out of about 150 miles away, and my brother in law drove it back. Ran fine, didn't overheat, good oil pressure.
The motor's been in the donor car for about two years while I got the Spitfire chassis prepped. I would crank it up every month or so, let it run till it opened the thermostat, then shut it down.
I swapped a Dellorto onto it, put fresh oil and coolant in it, primed the oil injection tubes with a vacuum pump before starting the engine, and put a couple of teaspoons of oil down the carb before I fired it up. It lit right off, ran great. Good oil pressure (50-60 PSI at 2500 RPM, Castrol 20w50 GTX.) The temp would climb to 190, then drop back to 180-185 once the thermostat opened. I've run the engine several times since the initial startup, and even bumped the injection pump up a bit (tweaked the actuating rod w/ pliers till I had approx. 080 gap between the lever and the stop). I don't care if it smokes a bit, but I do care if it seizes. By lifting the actuating rod, I could see some small air bubbles in the injection lines; I kept it lifted until the air bubbles all bled out. That was about ten days ago, the engine has been run several times since then. There are no air bubbles in the injection lines now.
I'm using a stock early style (big) RX7 oil cooler and lines, BTW. No weird trannies etc, stock RX7 clutch and flywheel, AFAIK motor has never been apart.
Weather conditions today: clear, sunny, cold (high '40's/low '50's). trailered the car to the autocross, started it up to back it off, ran great: good oil pressure etc. Ran the motor till the thermostat opened, then shut it down. No noise, nothing, no warning sounds/smells/anything to indicate a problem in the works.
Worked the start for the first run group, went back to the car afterwards to get ready for my run group. Coolant temp was still about 105 degrees. Started the engine, lit right off, no abnormal noise etc. It did blubber a bit (fuel in the intake? a bit rich on startup) so I blipped the throttle a couple of times to clear it out, about 2500-3000 RPM.
On the second blip at about 3000 RPM, it went 'clunk' and shut off. It's seized solid now, can't turn it with a breaker bar. WTF!?!?
Any ideas?
Just thought of this: due to space considerations, I had to route the oil cooler lines as shown below:
Could this have an effect?
A little background: it's a '82 or '83 12A. I bought the car it came out of about 150 miles away, and my brother in law drove it back. Ran fine, didn't overheat, good oil pressure.
The motor's been in the donor car for about two years while I got the Spitfire chassis prepped. I would crank it up every month or so, let it run till it opened the thermostat, then shut it down.
I swapped a Dellorto onto it, put fresh oil and coolant in it, primed the oil injection tubes with a vacuum pump before starting the engine, and put a couple of teaspoons of oil down the carb before I fired it up. It lit right off, ran great. Good oil pressure (50-60 PSI at 2500 RPM, Castrol 20w50 GTX.) The temp would climb to 190, then drop back to 180-185 once the thermostat opened. I've run the engine several times since the initial startup, and even bumped the injection pump up a bit (tweaked the actuating rod w/ pliers till I had approx. 080 gap between the lever and the stop). I don't care if it smokes a bit, but I do care if it seizes. By lifting the actuating rod, I could see some small air bubbles in the injection lines; I kept it lifted until the air bubbles all bled out. That was about ten days ago, the engine has been run several times since then. There are no air bubbles in the injection lines now.
I'm using a stock early style (big) RX7 oil cooler and lines, BTW. No weird trannies etc, stock RX7 clutch and flywheel, AFAIK motor has never been apart.
Weather conditions today: clear, sunny, cold (high '40's/low '50's). trailered the car to the autocross, started it up to back it off, ran great: good oil pressure etc. Ran the motor till the thermostat opened, then shut it down. No noise, nothing, no warning sounds/smells/anything to indicate a problem in the works.
Worked the start for the first run group, went back to the car afterwards to get ready for my run group. Coolant temp was still about 105 degrees. Started the engine, lit right off, no abnormal noise etc. It did blubber a bit (fuel in the intake? a bit rich on startup) so I blipped the throttle a couple of times to clear it out, about 2500-3000 RPM.
On the second blip at about 3000 RPM, it went 'clunk' and shut off. It's seized solid now, can't turn it with a breaker bar. WTF!?!?
Any ideas?
Just thought of this: due to space considerations, I had to route the oil cooler lines as shown below:
Could this have an effect?
Last edited by RX744CSP; 02-05-06 at 06:57 PM.
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