High rpm misfire under load

sowen · Post by **sowen** » Tue May 12, 2015 7:30 am

I've washed the sump out, and was suprised at how little crud and sludge there was in the bottom, the timing cover didn't have the usual baked on black crap inside which was a suprise too! The oil pump cover has only slight polishing in the grey surface where the gears run, none of my previous V8's were like that, and there is minimal scoring inside the gear housing. I've decided not to split the main and big end caps for now, that's something I can do at a later date if I wish. Overall it's a good engine apart from the amount of oil leaks it's developed over the years, either the bolts come out with no effort or sheared clean off!

sidecar · Post by **sidecar** » Tue May 12, 2015 10:38 am

In my humble Spongo was agreeing with DaveEFI without understanding what DaveEFI was trying to explain. I think that Dave was basically saying that if the oil pump does not show damage (which it could as it would be picking up particles directly from the sump) then it is unlikely that the rest of the engine would have suffered because the next thing in the oil flow is the filter, this would have trapped the metal so the rest of the engine would receive clean oil. (Only the oil pump has the unfortunate task of running in unfiltered oil).

So to sum up, if the pump looks OK then the rest of the engine will be OK, or at least will not have been damaged by the particles from the missing cam lobe.

DaveEFI, if I have misunderstood your post then I apologise to both you and Spongo!

DaveEFI · Post by **DaveEFI** » Tue May 12, 2015 11:18 am

Yes - that's what I was on about. Every bearing area will wear over a period of time producing debris of some sort, even if very small particles. It's the sole purpose of the filter to remove them from the oil being pumped to those bearings.

sowen · Post by **sowen** » Wed May 27, 2015 7:24 am

Update time

I got the engine back together, in and running late Saturday, had a few issues with snapped bolts and bodges to the timing cover water pump bosses that needed sorting along the way. Only last night was I able to take the SD1 out for a proper blast, and now there's no misfires or horrible noises, pulls all the way up the rev range happily now

Interestingly the fueling was way off on the Megasquirt after re-assembly, the engine running really lean based on lambda readings. Seems a lot better now after an hour fiddling about with the settings