jamesmartin
Well-Known Member
it would fire at tdc but the wrong one 180 is one turn of the crank but half of the cam
Colthebrummie
Well-Known Member
Skimming pistons is a very brave thing to do. Years ago, I used to do a bit of freelance mechanicing in a franchised garage. They had a TR7 in that had its head skimmed once to often. Their remedy was to fit two head gaskets, I advised against it but they went ahead. I left shortly after so I dunno what the result was.
Col
TheMegaMan
Well-Known Member
Hmmm. Are you sure about that? Given TDC is a crank-thing and it's measured on the crank shaft pulley, I always thought angles with respect to TDC were angles on the crankshaft, not the camshaft/dizzy. So 180 degrees out would be half a crank rotation, and a quarter of a cam/rotor arm rotation.
Doesn't really make a lot of difference - the engine won't run like that no matter how you measure it.
jamesmartin
Well-Known Member
yes im sure people get it 180 degrees out as crank needs to turn twice to cam so often they get the tdc when cam is 180 out
TheMegaMan
Well-Known Member
OK, you are specifically talking about the dizzy being 180 degrees out, then. I'd have described that as the ignition being 360 degrees out, given the 4-stroke cycle is 720 degrees. Not sure which interpretation @Landy1979 meant, but the result will be the same - engine wouldn't run at all.
jamesmartin
Well-Known Member
true but 180 our refers to cam position,when people say is it 180 out thats whats meantOK, you are specifically talking about the dizzy being 180 degrees out, then. I'd have described that as the ignition being 360 degrees out, given the 4-stroke cycle is 720 degrees. Not sure which interpretation @Landy1979 meant, but the result will be the same - engine wouldn't run at all.
Easy solution, to testing it.
Remove each plug lead at the dizzy and swop it with its opposite number. so one becomes 4 etc.
then try it again.
Happened to me after working on wifey's kit car.
Dunno how it happened but this sure cured it!
The longer way of doing it is to move crank to TDC, look at the valves for number 1 which should both be closed , then make sure the rotor arm is pointing to number one position on the dizzy cap.
If it ain't then make sure you know the direction the rotor turns in and the firing order, then reposition all the leads correctly.
Remove each plug lead at the dizzy and swop it with its opposite number. so one becomes 4 etc.
then try it again.
Happened to me after working on wifey's kit car.
Dunno how it happened but this sure cured it!
The longer way of doing it is to move crank to TDC, look at the valves for number 1 which should both be closed , then make sure the rotor arm is pointing to number one position on the dizzy cap.
If it ain't then make sure you know the direction the rotor turns in and the firing order, then reposition all the leads correctly.
