| Author | Message | ||
     Trevor Pickering Experienced User Username: commander1 Post Number: 154 Registered: 06-2012 |
Could anyone help with the best accurate method of finding TDC (with the head in place)on my 1953 4.5 engine. I have tried a rod through the spark plug hole but this is not very good as the rod is at an angle. I can of couse just use the mark and pointer on the fly wheel but as the engine has been apart I want to check this is correct. | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 150 Registered: 07-2018 |
Why not use the intake valve on #1, it should get you close enough with a dial gauge. Certain precautions should be taken of course, like disconnecting the battery and removal of all the plugs would make it easier. Make sure it's out if gear etc... Removing the valve cover and rocker shaft isn't too difficult. I use this method to replace my valve seals too, I just let the intake valves rest on the top of the pistons. There's enough friction with the new seals to keep the valve in place when installing the keepers. | ||
| Christopher Carnley Unregistered guest Posted From: 77.234.43.173 |
As the offset bolt on the flywheel only permits of it being fixed in its original position, that should suffice. Is the tongue on the distributor drive at 10 to 11? (Message approved by david_gore) | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 151 Registered: 07-2018 |
That's the other thing as Chris says, there's only one way for the flywheel to be mounted, so why would the TDC timing marks be off ? It's very unlikely for RR to get them wrong. | ||
| Trevor Pickering Experienced User Username: commander1 Post Number: 155 Registered: 06-2012 |
My concern was the fact that the pointer is attached to the bottom cover of the fly wheel and it is only thin sheet metal and the screw holes to secure it are not accuratly drilled so its very easy to suspect at least 2 or 3 degrees of error either side of TDC. Perhaps I am beings too pedantic!!!!! | ||
| David Hughes Experienced User Username: wedcar Post Number: 116 Registered: 07-2004 |
Trevor The most accurate method to find TDC with the head attached to an engine with a tool inserted through the spark plug hole, this tool would take the form of a spark plug with the internals removed and an adjustable rod fixed through the middle, long enough to touch the top of the piston. Determine the firing stroke, raised the piston slowly in clockwise rotation to touch the adjustable rod close to TDC, mark the crankshaft pulley in relation to a mark on the timing case, turn the engine in the reverse direction until the piston touches the adjustable rod again on the way up close to TDC, mark the pulley in relation to the timing case mark, TDC is half way between the two marks. Regards David | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 152 Registered: 07-2018 |
What David said, one could use a threaded piece of ready rod and thread the spark plug to suit, either 1/4 or 5/16, maybe 3/8. The thicker the rod the better so it won't deflect. There may be a concern that the intake valve may come in contact with the rod ??? I suppose the intake valve could be used too. Once the valve spring is removed, a small hose clamp on the stem could be used to keep the valve from dropping into the engine. After that a "stop" could be devised for the end of the valve stem to come up against as a reference. Given the fact the great deal of time RR took to get the valve timing as close as possible to "IO", I would think that the pointer is pretty accurate though. I can't imagine RR would be prone to sloppy machining practices to get the pointer out by as much as 2 or 3 degrees. Who knows though right, no one is perfect, not even RR. | ||
| Trevor Pickering Experienced User Username: commander1 Post Number: 156 Registered: 06-2012 |
Thanks for the replies Jeff I did try removing the center of a spark plug a couple of days ago and inserted a 3/8 rod through to try and touch the top of the piston but found that the rod touches the edge of the block and not the piston. I then turned down the bottom part of the rod to just under 1/4! but because of the angle it touches the piston at it just locks up when the piston comes up I tried using a thinner rod but because of the extra movement was unable to get accurate readings. If you look at the bottom cover you can see it could easily be out by a couple of degrees because of the way its made. Not one of RR better designs! Thanks again to all | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 153 Registered: 07-2018 |
So now I'm confused, you say after you turned the rod down to 1/4 inch you say it touches the piston and locks up _ isn't that what you want ? If the rod is locking the engine what coming in contact with the piston, that's when you make a reference mark on the flywheel. The engine is then turned in the opposite direction until it locks again. Another mark is made on the flywheel. TDC is in-between the two marks. Interesting how RR changed the timing mark, on my 4.25 litre, there is a window just above the starter and if I rember correctly the pointer is riveted to the bell housing _ it's quite substantial and not flimsy at all. There are no pointers on the bottom cover that are screwed to the cover. If there is no window just above the starter, how do you time the ignition ? | ||
| Trevor Pickering Experienced User Username: commander1 Post Number: 157 Registered: 06-2012 |
Jeff it is only locking up because of the angle as the piston is trying to bend the rod. I did try and do what you suggest but was getting a different result every time. I am now going with the pointer indicated TDC and hope that its near enough. Thanks again for taking the time to help me. | ||
| Christopher Carnley Unregistered guest Posted From: 77.234.43.148 |
Trevor, so is yours the automatic one? C. (Message approved by david_gore) | ||
| Trevor Pickering Experienced User Username: commander1 Post Number: 158 Registered: 06-2012 |
Yes it is Chris Hooper Body My intention is to get the engine and gearbox back in and then sell the car I have completly rebuilt everything on the chassis but the body requires restoration | ||
| Jeff Martin Experienced User Username: jeff_r_1 Post Number: 154 Registered: 07-2018 |
If you have not started the engine, it is permissible to re-use the same head gasket, it just takes less torqueing because it's already crushed. Even if the engine has been run for a little, the copper asbestos head gasket can be re-used, one just has to be careful of getting any carbon bits trapped between the surfaces. It all depends just how much you want to know for sure about the timing mark. | ||
| Trevor Pickering Experienced User Username: commander1 Post Number: 159 Registered: 06-2012 |
Not as much as taking the head off again Jeff I will trust the pointer and set up timing using that.  | ||
| Trevor Pickering Experienced User Username: commander1 Post Number: 160 Registered: 06-2012 |
I have just reset the timing using the pointer to TDC as reference and the inlet valve jut starting to open with the tappet set to.030" as per the book. Mananged to get the cam gear on after several attempts to get the bolt holes in line and not winding up the damper. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 2383 Registered: 09-2004 |
Cases like these I use the whistle on number 1 spark plug hole and then a dial gauge on number one inlet valve. | ||
| Bill Vatter Experienced User Username: bill_vatter Post Number: 128 Registered: 09-2004 |
You cannot directly determine the location of TDC when the piston is at its heighest position and have best accuracy. For accuracy, you need to mark flywheel position at equal piston heights 10 or more degrees before and after and then TDC is the point half way between those marks. Direct determination will get you at best + or - 2 or 3 degrees of true TDC but probably not that good. The indirect method will get you within 1 degree of true. David Hughes method above will do that. |
