'72 500L with 700cc performance engine. Has been running great. Throttle stuck, revs climbed high, I thought I had shut it off in time to avoid damage. Checked linkage, nothing stuck... restarted, idled smooth but now with severe engine knock. Tried advancing and retarding timing and putting the choke on, no change. Can anyone recommend what I might check prior to a complete rebuild?? Pic for reference of my hardware.

-Andrew

I would be tempted to do a carefull step by step strip-down---starting with the head and valves. Sadly, this doesn't sound good. Also, with the sump removed, check play in the bearings--any vertical movement? (which would indicate bearing damage)

Hutbed said:

'72 500L with 700cc performance engine. Has been running great. Throttle stuck, revs climbed high, I thought I had shut it off in time to avoid damage. Checked linkage, nothing stuck... restarted, idled smooth but now with severe engine knock. Tried advancing and retarding timing and putting the choke on, no change. Can anyone recommend what I might check prior to a complete rebuild?? Pic for reference of my hardware.

-Andrew

Click to expand...

Hi Andrew, overspending an engine can cause differing damage depending on the actual engine, but I would check for wear on the big ends (if you can get your hand in) grab the conrod and rotate the crank back and forth while feeling for movement at the big end. If you rock the crank gently you can sometimes feel wear at the forward main bearing (flywheel end) check for any cracks in the crankshaft immediately forward of the front main bearing. The crankshaft fails in this area from overspeed. Otherwise it's an engine out and strip/check all components. Bad luck.
Ian.

Unfortunately it has started pouring sideways rain in the wind, so my outdoor inspections and repairs will be at a pause. Thank you for the inputs. I might just swap the original engine back in now as I must prior to shipping the car in 4 1/2 months anyway.

Swapping the original engine back would seem to be the most sensible course of action. However, with the old engine back in, it would be wise to try and ascertain what you need to rectify your 700cc engine, and purchase the parts required so that you can take them back with you (packed up in the Fiat). (a) this will save you a fair bit of money (parts will be cheaper in Italy, and no carriage costs) and, (b) you won't have to wait an age to obtain the parts. You would be surprised as to how much you can pack into a 3-1/2 litre sump; even when bolted back onto the engine!