Hitchcocks Forum

hi all,

i have been working on a mk1 interceptor, it has had a full rebuild and has been fitted with new amal concentric carbs.

it has been converted from 6v to 12v and it has also been converted to coil and points. first problem is the spark seems very weak for a 12v system. second problem is when it actually decides to start for me it runs fairly smoothly but as soon as i blip the throttle it blows/spits Alot of fuel vapour out the carbs. i have also given it a test ride and it is completly flat, i.e. it doesnt want to accelerate with any conviction.

i am wondering i know i have timed the cam shafts so that the timing marks are inline. but i am wondering if because i used an exhaust cam in place of the inlet cam (supplied by our hosts) if the valve timing is slightly out and the inlet cam needs retarding by a tooth on the chain.

your thoughts will be greatly appreciated.

thanks
ed

Hi Barnes, I would agree that the valve timing is probably incorrect, in a situation like this I would ignore the timing marks and reset both inlet and exhast by their opening and closing points. you should have this information in the workshop manual.

Substituting cams on the Interceptors (and Twins generally,) is covered in a section of the manual as Dennis says (assuming you have the right book!) but if you read the notes section in the table it warns against various side effects. Our Hosts are very well informed on this (Allan sent me some info to identify cam types, there are probably fewer of them than the literature suggests,) so talk to them!
REgards, Mark

hi,

thanks for your replies. i shall check the manual but i havnt seen anything to date in there about cams so i may not have the right one. i shall try speak to allan regarding this. i am fairly sure the exhaust cam is correct as there is no back firing or knocking in the pipes.

what do you think regarding the weak spark?

many thanks
ed

A weak spark can really only be due to five things 1/ low voltage on the battery, 2/ low voltage at the coil (due to poor wiring/connector), 3/ faulty/incorrect coil, 4/ faulty condensor/capacitor, 5/ incorrect HT lead plug cap spark plug combination (more than one is a resistor type).

Now someone will think of other causes!!.