Adjusting timing
Discussion
I have been advised by the previous owner that the timing might be out on my '98 Chimaera 450 - so want to get this looked at.
I understand the process of timing up an adjustable dizzy - but my question is, do our EFI RV8's retain an old-skool adjustable distributor that can be loosened-off and rotated to alter the timing?
If it does, is it something you guys think I could do myself - and can someone tell me the process to loosening off the dizzy? Or in your opinions is it best left up to a TVR specialist...? Or perhaps just a normal garage? (I have a fellow nearby I trust, but the nearest TVR specialist I trust requires taking a day off from work, driving 100+miles there, etc)
Car has an unusual flatspot and exacerbated low-rpm shunting, and ideally would want to get this sorted sooner rather than later...
cheers,
Dom
I understand the process of timing up an adjustable dizzy - but my question is, do our EFI RV8's retain an old-skool adjustable distributor that can be loosened-off and rotated to alter the timing?
If it does, is it something you guys think I could do myself - and can someone tell me the process to loosening off the dizzy? Or in your opinions is it best left up to a TVR specialist...? Or perhaps just a normal garage? (I have a fellow nearby I trust, but the nearest TVR specialist I trust requires taking a day off from work, driving 100+miles there, etc)
Car has an unusual flatspot and exacerbated low-rpm shunting, and ideally would want to get this sorted sooner rather than later...
cheers,
Dom
Edited by domV8 on Sunday 14th June 11:01
yes, old school dizzy which can be rotated after loosening 'pinch' bolt 9/16 inch imperial spanner but a 14mm metric should fit if an old un. Got to be done by feel and is overtightened so watch knuckle skin.
Old school timing light but you need a 12v supply as the battery is not easy 2 got 2 (just use another battery)
Dead easy but you must be accurate with the correct timing, with/without vaccuum, rpm, 4 your engine, they vary...
Get the figures and its easy to do. Clean crank pulley and mark tdc etc with tippex.
Don't overtighten pinch bolt but you always do...
Old school timing light but you need a 12v supply as the battery is not easy 2 got 2 (just use another battery)
Dead easy but you must be accurate with the correct timing, with/without vaccuum, rpm, 4 your engine, they vary...
Get the figures and its easy to do. Clean crank pulley and mark tdc etc with tippex.
Don't overtighten pinch bolt but you always do...
Here's a few tips.
TDC is inaccurately marked on some engines so it's best to check it on your engine by removing no. 1 spark plug and using a rod to determine when the piston's at the top of its travel.
Set the timing at 8° BTDC static. As it has electronic ignition it's not actually possible to do statically, but it will be close enough to set it at idle with the vacuum pipe removed.
TDC is inaccurately marked on some engines so it's best to check it on your engine by removing no. 1 spark plug and using a rod to determine when the piston's at the top of its travel.
Set the timing at 8° BTDC static. As it has electronic ignition it's not actually possible to do statically, but it will be close enough to set it at idle with the vacuum pipe removed.
I wrote this today 4 anothe lnk but t has some relevance here I think....
Got a new seal today from Polar Bearings(£4.50 you robbin TVR shop!!)and it solved the problem, not even a drop now...
There is nothing visibly wrong with the seal I removed!
I could see the ‘core plug’ but it looked okay and dirty, unlike the bottom of the timing cover, spotless from washing with oil...
To remove the pulley/damper bolt requires some effort and I found that applying the handbrake/chocking the wheels and in gear will not lock the crank enough to undo it! You have to lock the ring gear of the flywheel..
There is some play in the pulley and on inspection the keyway in the damper was found worn, needs replacement. Coincidentally this engine is suffering from a miss-fire, particularly when accelerating from low revs and I am looking at ignition timing as we have just about checked everything else!
One of the tricks of the LPG trade is to close the plug gaps down to 0.6mm, this aids weak sparks to perform better and avoids misfires. We have done this and it is still a spark strength problem. A new coil, checks of all wring/resistors, replaced amplifier (from an Austin Maestro), leads, cap, arm etc. I have checked the ignition timing at 8 BTDC.
After refitting the damper assy. I timed the ignition with a vacuum gauge, swinging the distributor to the point of max on the gauge, after carefully marking with tippex the starting point on the base of the dizzy shaft. I left the dizzy loose for further adjustment.... And it is very hot just there.
After a test drive the misfire has gone!!
I cannot trust the timing marks, the pulley has some play and from previous experience I know it was 2 degrees out of line. I had to use the old school of timing the ignition, from the days unleaded was just new..
On petrol with the engine running turn the dizzy anticlockwise until the engine note changes noticeably, this is over-advancing the ignition timing. Drive the car and listen for ‘pinking’, you only have to go a couple of hundred yards or so, change up so that the engine is working in low revs. You can hear it unless the dizzy is not rotated anticlockwise enough. Stop and rotate the dizzy clockwise just a fraction. Drive again. Carry on until it stops pinging completely. Tighten dizzy pinch bolt, not too much but you will anyway.
After carrying out the above I checked the timing, 14 BTDC on the pulley! It drives perfectly now.
The bolt is supposed to be torqued to 280Nm!! It is not full tight yet as its gotta come off again, but that is some torque! And there are stories of that bolt breaking, I find that hard to believe! The damper rubber looks okay but the worn keyway demands replacement of it.
It’s no good checking the accuracy of the timing marks on the pulley by just removing the No 1 Spark plug and feeling when the piston is at the top, the crank can move several degrees without the piston moving! it's called ‘ineffective crank angle’ from my apprentice days (when unleaded was unheard of!).
Through the No 1 spark plug (remove them all) find TDC on the power stroke (both valves closed) . Rotate the crank anticlockwise about 90 degrees and measure the depth of the piston from any convenient point, the top of the spark plug threads would be ideal but it is hard to get to, I used a point on the rocker box cover. Use a cable tie as the depth gauge, it safe, unlike a pencil (which will break if inadvertent rotation of the crank takes place.. It happens) or as I one saw a drill, which did break...
Mark the crank pulley at the timing pointer.
Rotate the crank clockwise to about 90 degrees ATDC and accurately get the depth of the piston the same as before. Mark the pulley again. The exact centre of the two marks on the pulley is TDC!!
Nobody but nobody has as many tippex marks on their crank pulley/damper as Teetertank, I put six there today!
And its Teetertanks birthday!!!
He wants me to fit a toothed wheel on the damper to facilitate an improved ignition system but I think I fixed it now. He asks me if fitting said system will have any effect, I say only in your mind and wallet. Save your money for me to convert to LPG NITROUS!!!
Got a new seal today from Polar Bearings(£4.50 you robbin TVR shop!!)and it solved the problem, not even a drop now...
There is nothing visibly wrong with the seal I removed!
I could see the ‘core plug’ but it looked okay and dirty, unlike the bottom of the timing cover, spotless from washing with oil...
To remove the pulley/damper bolt requires some effort and I found that applying the handbrake/chocking the wheels and in gear will not lock the crank enough to undo it! You have to lock the ring gear of the flywheel..
There is some play in the pulley and on inspection the keyway in the damper was found worn, needs replacement. Coincidentally this engine is suffering from a miss-fire, particularly when accelerating from low revs and I am looking at ignition timing as we have just about checked everything else!
One of the tricks of the LPG trade is to close the plug gaps down to 0.6mm, this aids weak sparks to perform better and avoids misfires. We have done this and it is still a spark strength problem. A new coil, checks of all wring/resistors, replaced amplifier (from an Austin Maestro), leads, cap, arm etc. I have checked the ignition timing at 8 BTDC.
After refitting the damper assy. I timed the ignition with a vacuum gauge, swinging the distributor to the point of max on the gauge, after carefully marking with tippex the starting point on the base of the dizzy shaft. I left the dizzy loose for further adjustment.... And it is very hot just there.
After a test drive the misfire has gone!!
I cannot trust the timing marks, the pulley has some play and from previous experience I know it was 2 degrees out of line. I had to use the old school of timing the ignition, from the days unleaded was just new..
On petrol with the engine running turn the dizzy anticlockwise until the engine note changes noticeably, this is over-advancing the ignition timing. Drive the car and listen for ‘pinking’, you only have to go a couple of hundred yards or so, change up so that the engine is working in low revs. You can hear it unless the dizzy is not rotated anticlockwise enough. Stop and rotate the dizzy clockwise just a fraction. Drive again. Carry on until it stops pinging completely. Tighten dizzy pinch bolt, not too much but you will anyway.
After carrying out the above I checked the timing, 14 BTDC on the pulley! It drives perfectly now.
The bolt is supposed to be torqued to 280Nm!! It is not full tight yet as its gotta come off again, but that is some torque! And there are stories of that bolt breaking, I find that hard to believe! The damper rubber looks okay but the worn keyway demands replacement of it.
It’s no good checking the accuracy of the timing marks on the pulley by just removing the No 1 Spark plug and feeling when the piston is at the top, the crank can move several degrees without the piston moving! it's called ‘ineffective crank angle’ from my apprentice days (when unleaded was unheard of!).
Through the No 1 spark plug (remove them all) find TDC on the power stroke (both valves closed) . Rotate the crank anticlockwise about 90 degrees and measure the depth of the piston from any convenient point, the top of the spark plug threads would be ideal but it is hard to get to, I used a point on the rocker box cover. Use a cable tie as the depth gauge, it safe, unlike a pencil (which will break if inadvertent rotation of the crank takes place.. It happens) or as I one saw a drill, which did break...
Mark the crank pulley at the timing pointer.
Rotate the crank clockwise to about 90 degrees ATDC and accurately get the depth of the piston the same as before. Mark the pulley again. The exact centre of the two marks on the pulley is TDC!!
Nobody but nobody has as many tippex marks on their crank pulley/damper as Teetertank, I put six there today!
And its Teetertanks birthday!!!
He wants me to fit a toothed wheel on the damper to facilitate an improved ignition system but I think I fixed it now. He asks me if fitting said system will have any effect, I say only in your mind and wallet. Save your money for me to convert to LPG NITROUS!!!
domV8 said:
THanks Hoach!
Where do I get the figures from..?
Many thanks,
Dom
You should be aiming at around 28deg at full advance, normally anything over 3250 rpm, the idle timing is less important, but do check it at idle and anything less than 12 deg and you could with someone altering the dizzy weights for youWhere do I get the figures from..?
Many thanks,
Dom
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