Ignition timing curve 4.3 Griffith

[tvr4ever]

Does anyone know how the ingnition timing curve for a 4.3 Griffith with cat should look like. Mine pinks every now and then, especially with the warm weather. I was thinking of checking the timing but can't find any info on how much it should be at certain revs. My guess would be somewhere inbetween 28 to 38 degrees at about 4000 rpm without the vacume hose attached.

I know there are certain mechanical ignitions where you can adjust the weights so the advance changes. Can this be done with the 4.3 ignition.

Any ideas/suggestions ??

Fred

[HarryW]

Every car is different, but a nominal 28 degrees at 4K is a good start (vac off), so long as it doesn't pink, in which case its gotta be lower. Some enigines out here have extreme high compresions and won't even tolerate this.
The RV8 is mainly mechanically advanced, if the advance comes in too early then its all over on that front, I believe that advance starts around 2-3K. The weights can be reduced to delay the advance, but this is a 'get yor swiss file out type of thing and if you leave any burrs then it could puink lower down if the weights don't return cleanly.
I understand that a fully mapped ignition is the way to go for real improvements. The existing system whilst OK is a compromise, the engine will take more advance higher up the rev range (assuming you have enough petrol going in) but will pink itself to death getting there .
Anyone fitted a mapped system, if so costs/benefits/ results would be nice .
All IMHO and probably wrong as per normal .

Harry

[gerjo]

tvr4ever said:

Does anyone know how the ingnition timing curve for a 4.3 Griffith with cat should look like. Mine pinks every now and then, especially with the warm weather. I was thinking of checking the timing but can't find any info on how much it should be at certain revs. My guess would be somewhere inbetween 28 to 38 degrees at about 4000 rpm without the vacume hose attached.

hi Fred,

My former 4.3 with cat was somewhere around 32 degrees at 4.000 rpm, vacuum off, but indeed, every engine is different. Try it till it pinks. You can also ask Jens.

[tvr4ever]

As it turns out the ignition is at 25 degrees at 4000 rpm. Maybe the pinking is caused by the spark plugs, i will change them.

Fred

[HarryW]

tvr4ever said:

As it turns out the ignition is at 25 degrees at 4000 rpm. Maybe the pinking is caused by the spark plugs, i will change them. Fred

At what point does the pinking start , as you say the mechanical advance may be coming in too early (worn springs in it?). You could even have one of those not so rare Tivs with a large compression ratio (well over 10:1) in which case it probably can't take more than 22 deg.
Personnally I'd get it checked out on a RR by the likes of Mark Adams. Observed very similar work being done on one of the earliest 500 griffs with exactly your symptoms. It was sorted out and relased roughly 40bhp/50lb torque for him a the same time.

Harry

[tvr4ever]

Pingking usualy started around 3000 rpm. Just this morning when i had the ignition checked the car did not pink at all. I pushed it hard, no pingking. Figures, maybe one of those gremlins..

Fred

[HarryW]

tvr4ever said:

Pingking usualy started around 3000 rpm. Just this morning when i had the ignition checked the car did not pink at all. I pushed it hard, no pingking. Figures, maybe one of those gremlins.. Fred

Could be the weights sticking in the dizzy sometimes.

Harry

[gerjo]

tvr4ever said:

As it turns out the ignition is at 25 degrees at 4000 rpm. Maybe the pinking is caused by the spark plugs, i will change them. Fred

At 25 degrees I think you're losing out on quite a bit of power (or maybe your base level hasn't been marked correctly). Something else must be causing the pinking. Running 98 octane might help (a bit). I would call Jens/Bert to discuss or maybe Steve/Pete/Tim can shed some light on this.