High rpm misfire under load

ChrisJC · Post by **ChrisJC** » Thu May 07, 2015 7:11 am

Indeed you have!

Any idea on mileage of those?

Chris.

sowen · Post by **sowen** » Thu May 07, 2015 7:49 am

97k miles reading on the dashboard. Odd as it's the only one, all the others are fine, nice flat lifters and clean lobes on the camshaft. It was obscured by the web of the gallery, and being no lobe at all I missed it entirely, looking for a heavily flattened off lobe!

DaveEFI · Post by **DaveEFI** » Thu May 07, 2015 8:56 am

Excellent news. Always good to find the fault.

sowen · Post by **sowen** » Thu May 07, 2015 9:34 am

DaveEFI wrote:Excellent news. Always good to find the fault.

Completely, I can only imagine as the exhaust is essentially blocked off on no.3 that as it went over 4000rpm it was enough to audibly blow back through the intake killing performance. Also be interesting to see how the general economy and emissions change with 8 working cylinders

Spongo · Post by **Spongo** » Thu May 07, 2015 12:34 pm

One thing occurs to me though, where are all the filings from what is a relatively large lump of metal?

I would be inclined to fully strip and rebuild the engine after that one as you dont know what else may have been damaged by all those bits of metal flying around.

DaveEFI · Post by **DaveEFI** » Thu May 07, 2015 12:54 pm

Spongo wrote:One thing occurs to me though, where are all the filings from what is a relatively large lump of metal?

I would be inclined to fully strip and rebuild the engine after that one as you dont know what else may have been damaged by all those bits of metal flying around.

I'd say overkill. The oil filter will stop any such particles. Same as any from the bores and rings etc.

sidecar · Post by **sidecar** » Thu May 07, 2015 6:25 pm

DaveEFI wrote:
Spongo wrote:One thing occurs to me though, where are all the filings from what is a relatively large lump of metal?

I would be inclined to fully strip and rebuild the engine after that one as you dont know what else may have been damaged by all those bits of metal flying around.
I'd say overkill. The oil filter will stop any such particles. Same as any from the bores and rings etc.

I agree, the metal will not be in big lumps, it will be in small filings which will have been trapped in the filter.

This is the third cam that I've seen with a lobe totally worn away in as many weeks, it is odd how one lobe can be totally removed and the others don't show the same amount of damage. Anyway this is a good advert for regular oil changes and using an oil with a load of ZDDP in it such as Valvoline VR1

ChrisJC · Post by **ChrisJC** » Thu May 07, 2015 7:16 pm

I suggest it isn't a problem with the lubricant, otherwise they'd all be the same. Perhaps some issue with the cam or follower?

Chris.

sowen · Post by **sowen** » Sat May 09, 2015 8:50 am

Spongo wrote:One thing occurs to me though, where are all the filings from what is a relatively large lump of metal?

I would be inclined to fully strip and rebuild the engine after that one as you dont know what else may have been damaged by all those bits of metal flying around.

As others have said it looks like it's been an ongoing issue for a long time, the rest of the lobes are fine, when turning the engine over I was looking for lifters that weren't lifting as much as others, completely missed the lifter that didn't lift! The oil pump housing is pretty good too, minimal scoring inside and very little wear on the pump cover plate too, good indications as far as I'm concerned.

I have a variety of other V8's knocking about so there simply isn't any desire to strip the 3.5 down any further. After re-assembly I'll be putting my effort into a suitable replacement powerplant to suit my needs and wants

Denis247 · Post by **Denis247** » Sat May 09, 2015 5:55 pm

The magnetic sump plug has probably stopped a lot circulating too.

sidecar · Post by **sidecar** » Sat May 09, 2015 7:26 pm

Denis247 wrote:The magnetic sump plug has probably stopped a lot circulating too.

All the Rover lumps that I've worked on have not had a magnetic sump plug???

mgbv8 · Post by **mgbv8** » Sat May 09, 2015 7:30 pm

OUCH!!

Yep that will cause a problem

And luckily its not an expensive fix

DaveEFI · Post by **DaveEFI** » Sun May 10, 2015 12:20 am

If metal particles were getting past the gauze on the pump pickup, surely the pump itself would be the first thing to wear? After that, the filter will stop them.

Spongo · Post by **Spongo** » Mon May 11, 2015 1:01 pm

My thougts exactly which is why I suggested some further investigation to check the wear state of the engine.

bigaldart · Post by **bigaldart** » Mon May 11, 2015 7:25 pm

A lot of the time one lobe goes because the lifter struggles to rotate, carbon build up because of the outer row of bolts letting combustion gasses into the valley over time. Once the lifter stops rotating it doesn't take very long to wipe out the lobe.

Alan