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GT6 Timing question


coops7
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Hi All

 

The gist of this question is, that my mkll gt6 has a bit of a 'Frankenstien' under the bonnet. To cut a long story short, when I bought it the previous owner told me that the block was not the original but had possibly come from a Vitesse, though he wasn't sure as it came with the car, from the previous owner to him. There is no engine no. to go by, so I cannot confirm the model. The car came with all receipts to show that it has been brought up to gt6 spec and I have no reason to doubt this after three years of ownership. 

The engine does have domed pistons( which he informed me of and I have since checked to be correct)  but when I checked the timing it was quite a bit out (can't remember how much but retarded). I have since fitted electronic ignition to it's Lucas  d22 dizzy, which I know is also not the original Delco but he felt was a better dizzy.

My question is, what degree of timing should I be applying? I believe the mkll was set at 10 deg btdc, but with the domed pistons should I use this or the mklll setting, which I think is about 12 deg, or have I got my facts wrong altogether?

             

                               Thanks in advance Jeff

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No engine number? It should be stamped on the top of block on the dizzy side, but blocks can get skimmed.  If you don't know the number how do you know domed pistons are correct? I thought domed were introduced in 1972 on mk3.

 

The timing is arbitrary, these engines were designed for 5 star fuel, no longer available. According to Haynes mine should be 13 BTDC but others suggest for modern fuel 7 or 8. Static timing can be a lottery, there can be slack in the timing chain and other components so even when set to what you think is correct, it aint right!

 

The old fashioned method, start the engine twist the dizzy for maximum revs, turn it back a gnats and take it for a run. If correct it shouldn't pink and after a longer run the plugs should be biscuit coloured.

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Forget timing lights and marks. As Doug says, do it by ear. drive the car (light throttle mild incline and gently accelerate) and then keep advancing teh timing until it pinks. Then retard it a little until no pinking happens, the timing is as correct as it is possible to get. I have had cars on rolling road, and they could not improve on the timing set in this way.

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Thanks for speedy replies, appreciated, there is no engine number on block as I said it came from god knows where many years ago into the hands of a previous owner who then installed it in the car. When I said checked the domed pistons to be correct I meant the info given by the guy I bought car off was correct, which I checked with a flashlight down the plug hole.

If that's all there is to it, then I shall continue as per your advice guys, cheers.

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