E: Engine Big Bore Comet

[timell]

I own a Bob Dunn converted big bore Comet and need some advice re ignition and possibly cam timing. I know there are people on here with similar and wonder if they would mind contacting me to discuss please?
Thanks, Tim

 

[brian gains]

Hi Tim Have a scroll through recent threads, I'm sure there was one that touched on this. ?.

 

[timell]

Hi Tim Have a scroll through recent threads, I'm sure there was one that touched on this. ?.

Thanks Brian. I have searched, but haven't found anything that specifically answers my questions. It would be good to talk to a current owner that is running the same engine.

 

[chankly bore]

Give me a yell, Tim. I run the "Comet on Steroids" and we met at Stafford about four years back. hardarser(at) outlook.com. Cheers, Charlie.

 

[vibrac]

I have a big bore Comet and then sometimes its not ie I have a top hat bush for the crankcase if I want to revert to 500 cc I have never altered my timing from 34 deg BTDC or varied from a target of 4deg BTDC valves fully open (the Compression ratios being simillar) I have also run it up on Bens rolling road and the timing is the best

 

[timell]

I have a big bore Comet and then sometimes its not ie I have a top hat bush for the crankcase if I want to revert to 500 cc I have never altered my timing from 34 deg BTDC or varied from a target of 4deg BTDC valves fully open (the Compression ratios being simillar) I have also run it up on Bens rolling road and the timing is the best

Thanks, thats helpful. What carb, cam and compression are you running?

 

[timell]

Give me a yell, Tim. I run the "Comet on Steroids" and we met at Stafford about four years back. hardarser(at) outlook.com. Cheers, Charlie.

Message sent Charlie thanks.

 

[A_HRD]

For what it's worth, I remember Bob Dunn telling me that, for his big-bore Comet engines, you should start experimenting with the ignition timing at around 26 BTDC - and expect to end-up somewhere around 26 to 30 as the sweet-spot.

Peter B

 

[timell]

For what it's worth, I remember Bob Dunn telling me that, for his big-bore Comet engines, you should start experimenting with the ignition timing at around 26 BTDC - and expect to end-up somewhere around 26 to 30 as the sweet-spot.

Peter B

, Thanks Peter, that's helpful.

 

[Robert Watson]

Interesting, I have been playing with a 626 engine that had a BTH which was very hard starting. Swapped it out for a coil setup and ATD and not much better, changed out the top 1/2 of the ATD for one which gave only 24 degrees of advance and set it at about 30 full advance --- much improved....