Thread: Timing 2.25 Petrol....round 2...

set it by ear.....

the quality of the fuel has gone up since the plate was made and the lead has gone.

trying to set these engines by the book is now no longer the way to go. but the book is still an excelent starting point.

That said with the engine set by the book it should still run smoothly, Id suggest that you might have a problem else where like a dodgy plug or lead.

6 degrees ATDC is for 85 octane fuel from memory, TDC for 90 and 6 degrees BTDC for 95.

Make sure the valve gaps are set correctly,I couldn't get one of my old 2.25 to run very good by the timing i did everything to no avail & for some reason i decided to check & reset all the valve gaps then do the timing & it ran & sounded much beter.But you must do it in order by the book not the front to back..hangon that mite of been for the deisel valves .anyway just give them a check...

OK.

What I cant work out is that I have a persistent problem with the engine running on when you switch the ignition off.

I think it is related to timing because if I run premium (98) it does not do it.
Even when advanced quite a bit. (runs nice)
Does this sound right?

I am currently running standard unleaded with more conservative timing, 6 ATDC as listed on the plate - surprise...it runs on.

I would like to be able to run standard unleaded because I think premium is a waste, how the hell do I solve this run on?

very very roughly it running on because of carbon deposits. with ATDC ignition the combustion process isnt as complete so youre getting carbon deposits soaking up some fuel mix and becoming hot spots which allow the engine to diesel. With BTDC timing the combustion process becomes more agressive so you dont get the carbon deposits as much. (and those you do have dont soak up the fuel mix because its all busy being burnt)

you might also be running a touch rich.

As the cam is only a simple profile and its got 90 degree phasing on it put the crank on TDC and adjust/check any rockers that are loose, spin the engine 360 degrees in the direction of normal running and then do the others. all valves are 10 tho hot or cold.

For the spark timing Id set for TDC static timing and start it up, if its running smoothly let it warm up then advance it till its knocking, back it off a bit (say 5 degrees) and give it a rev up to something like 4K rpm. If it doesnt knock on the mechanical advance lock it there and take it for a drive (take your spanners with you), give it WOT on a good climb and if it knocks under load back the timing off in small increments. Once its stopped knocking take it back load it up, hook up the trailer and do it again. Keep the spanner for the dizzy timing in the car so you can adjust the timing again if you get a bad batch of fuel.

if its not running smoothly its time to fault find.

Thanks alot mate, really appreciate it.
Ill do some tweaking this weekend.

Do you reckon its worth pulling the head and checking for carbon buildup?
If its running on its likely to be fairly choked up yeah?

urmmm yes no maybe....

theres a couple of redneck tune tricks that can shift the carbon.

take it out for a good long hard drive make the bugger work.
run it a little lean for a little while
get it running fast and spritz some water down the carby
mix in a little avgas into the fuel for a couple of tanks

If you are running thermo fans directly off the alternator positive, then the fans spinning (electric motor) can create a momentary backfeed of power to the ignition circuit and cause the engine to run on for a bit.

- or so I found.