13-02-2018, 02:57 PM
(This post was last modified: 13-02-2018, 03:04 PM by Reckless Rat.)
Not wishing to intrude on the former thread, my RP has developed a slight problem where it oils/cokes up the plug on n°3 cylinder. In an attempt to reduce the problem I have changed over from B6HS plugs to a set of hotter running BP5HS. The car is a standard RP saloon with a 37 head and H1 1 1/8" SU carb.
On Sunday 4th we took the car out for the annual winter rally and I had to stop twice to change the plug on n°3 because the car started misfiring. The car also seemed to be a bit down on power, but I put that down to the fact that I had a slightly over average sized co-pilot...
I have since done a compression test, thinking that it was a bore wear problem - the engine has been +.030 oversize since time mint imperial and had a new set of rings, valves & valve guides circa 2005, possibly a bit earlier.
The results of the compression test are as follows: (cylinders 1, 2, 3 & 4)
Cold: (psi) 100, 100, 110, 95 (I put the slightly higher reading on n°3 down to the presence of oil in the bore).
Hot: (psi) 130, 125, 125, 130
So I guess there's not much wrong there.
I will be removing the engine/gearbox when the weather gets a bit warmer because the clutch release bearing needs replacing, at which time I will strip the valves out, regrind and check the seats & valve guides. I suspect that oil is being drawn up the valve stem on n°3 cylinder - when I did the "Col de la Bonnette" some years back there was a valve sticking afterwards but I can't remember which.
Oh yes, one other thing. As I was stripping down the engine prior to the compression test it looked like the piston ion the carb was stuck in the down position, but I can't be sure if that was just down to me working on the engine or whether it had been like that during the run. Mind you plugs 1,2 and 4 were all the right colour. Just n°3 was acting up.
Apparently we're in "La Vie de l'Auto" again too...
Any other ideas?
On Sunday 4th we took the car out for the annual winter rally and I had to stop twice to change the plug on n°3 because the car started misfiring. The car also seemed to be a bit down on power, but I put that down to the fact that I had a slightly over average sized co-pilot...
I have since done a compression test, thinking that it was a bore wear problem - the engine has been +.030 oversize since time mint imperial and had a new set of rings, valves & valve guides circa 2005, possibly a bit earlier.
The results of the compression test are as follows: (cylinders 1, 2, 3 & 4)
Cold: (psi) 100, 100, 110, 95 (I put the slightly higher reading on n°3 down to the presence of oil in the bore).
Hot: (psi) 130, 125, 125, 130
So I guess there's not much wrong there.
I will be removing the engine/gearbox when the weather gets a bit warmer because the clutch release bearing needs replacing, at which time I will strip the valves out, regrind and check the seats & valve guides. I suspect that oil is being drawn up the valve stem on n°3 cylinder - when I did the "Col de la Bonnette" some years back there was a valve sticking afterwards but I can't remember which.
Oh yes, one other thing. As I was stripping down the engine prior to the compression test it looked like the piston ion the carb was stuck in the down position, but I can't be sure if that was just down to me working on the engine or whether it had been like that during the run. Mind you plugs 1,2 and 4 were all the right colour. Just n°3 was acting up.
Apparently we're in "La Vie de l'Auto" again too...
Any other ideas?