Help! GT40 Starting Problem......

bones · Post by **bones** » Tue Nov 03, 2009 12:08 pm

if youve already done this ,then i will say sorry know. Check you have number 1 piston at TDC ( but not by the pulley markings ), if you can use an old spark plug and modify it to take a metal rod of some sought and weld it to the plug bottom,then put engine to what you think is tdc,and clean the damper markings screw it into number 1 plug ,remember to turn back the engine so it goes in full, turn the engine by hand clockwise until it hits the rod, mark the pulley in-line with the pointer, turn engine back anti clockwise until it hits the rod, mark the pulley again, find the middle of the 2 marks and that should be tdc. Remove the plug and check the rotor arm, adjust the dizzy if needed to be in-line with number 1 lead,with engine doing 1000rpm set the timing with light to 6 deg btdc, its a good starting point. Finding TDC is important as i found out, If youve already done this then sorry again for going on

rich

marcoos_1 · Post by **marcoos_1** » Thu Nov 05, 2009 10:04 am

Hi Rich,

I'll give this a go......I have a stupid question though (in fact two stupid questions!):

1) How do you know what length of rod to use (to short won't hit and too long will not be TDC?) Do I drill te center out an old plug and let the rod slide through the hole as the piston comes up, then weld it at it's highest point?

2) Can the pulley marks be wrong - have you found this before? I assumed it was on a keyway and couldn't be wrong?

Thanks for your patience Rich.

bones · Post by **bones** » Thu Nov 05, 2009 10:54 am

Hi, when i made mine up i think it was about 1 1/2" or so out the bottom,you just need the threaded part so what ever way you find easier to do it, just make sure the rod is fixed good so as it doesnt fall out or move. you want the piston to hit the rod in both directions to give you the marks on the pulley,hence why its turned by hand, its halfway between the 2 marks that will give you tdc then just take the plug out and move the pulley to the halfway mark, and that will be tdc, then just check the rotor is lined up. I had to do mine this way after some advice from people on the forum. hope it helps

rich when i rebuilt my engine i checked the pointer, and that wasnt right, i think about 1 or 2 deg out from tdc

ChrisJC · Post by **ChrisJC** » Thu Nov 05, 2009 12:00 pm

Silly question, you are triggering your strobe from no. 1?

Chris.

marcoos_1 · Post by **marcoos_1** » Fri Nov 06, 2009 10:14 am

yeah, definately checked that (I was doubting myself!). Strobe is on No1.

jefferybond · Post by **jefferybond** » Fri Nov 13, 2009 1:05 pm

marcoos_1 wrote:OK - hopefully this will work. This should be a pic of the distributor internals and the module I have.

That first picture of the aluminium thing is the ballast resistor, most likely a Lucas 9BR. There is no electronic 'magic' going on in here, just a resistor. If I remember correctly it has 3 spades on each side. I have the wiring diagram at home somewhere!

Your distributor looks like an Opus 35DE8, as fitted to some (all?) SD1s (same as mine!). These distributors are notoriously unreliable apparently, but mine still works!

Jeff

jefferybond · Post by **jefferybond** » Fri Nov 13, 2009 1:16 pm

marcoos_1 wrote:OK...an update on the problem.

I have disconnected the vac advance from the carb to the distributor. The car nows runs, but when I attempt to set the timing with the strobe I can only get so far, then just as the timing marks are approaching the pointer (within about 10-20 degrees) the timing light stops working and the car runs rough.

Are you sure you are triggering the strobe off no.1 cylinder? This is of course the front cylinder nearest the distributor.

It sounds like you are trying to swing the timing so far that the rotor arm is no longer pointing to the correct segment on the cap!

You can get a reasonable timing by ear by swinging the dissy to get the fastest idle (which will be waaay advanced), then retard the timing so that it starts to slow down a bit, but not so far as it starts to run rough. This should be good enough to drive it and see if it pinks! (then adjust/try again etc).

Jeff

marcoos_1 · Post by **marcoos_1** » Sat Nov 14, 2009 1:41 pm

Ok guys,

I have done all the timing etc and it appears my Opus is indeed (as some of you suggeted) Opeless! I have managed to get a substitute unit from Jim Robinson at JRV8. I cannot recommend this guy strongly enough....he knows his stuff, is very willing to give advice and is very well priced! You guys may already know him, but this is my first contact and he was a real pleasure to deal with. My new dizzy and ignition arrived over night and is going in this weekend. Fingers crossed......hopefully no more head scratching!

Thanks to all for the help and advice so far.

CastleMGBV8 · Post by **CastleMGBV8** » Sat Nov 14, 2009 3:58 pm

Jim at JRV8 does indeed give excellent service and is one of our forum sposors.

Kevin.

gbtv8 · Post by **gbtv8** » Sun Mar 11, 2012 7:26 pm

Has this problem been resolved yet? I have been having exactly the same problems, have gone down the same routes and after having fitted a new dissy and coil I still cant get it to start when cold. After going through all the basic steps yesterday I did get it to run and thought I had cracked it. Today I went back and it wouldn't start. I have just removed the plugs and found them to sooted up. Try some new plugs and start again?

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Help! GT40 Starting Problem......

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