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Camshaft Timing Issues

Phil Wright

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Evening all,

After 3-4 years of hard work the second restoration of my spitfire is now complete, and i'm looking forward to getting involved in club events again.

Unfortunately however i'm having an issue which has left me stumped so thought i'd see if anyone else has any ideas. The car is just about ready for MOT now, however I can't get it to run right. The engine has been rebuilt totally, with a Kent Fast Road 83 cam (TH5), 123 ignition, rebuilt carbs, gas flowed head, new loom etc. When I start her up she's tricky to fire and when she does run the engine is clearly out, as if the timing is way off. When I connect my timing light I can see the flash is very retarded. However, if I advance the ignition to where it should be (8 BTDC) the engine just stops and won't restart. Backtracking slightly, the install procedure for the 123 dizzy has been followed, and the static timing set point is where the strobe thinks the timing should be, but the engine won't run on this setting.

I've checked the cam timing, and with No. 1 on the firing stroke @TDC, valves 7 & 8 are 'on the rock'. Also, I set and re-checked the install figure of the cam, which is inlet valve of No. 1 (valve No. 2) at full lift at 103 degrees, the install figure for the cam.

Everything seems right but i'm not getting anywhere. I'm all out of tea now too! If anyone on here has any suggestions i'd love to hear them. I feel i'm doing something daft, but cant think what it is...



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Thanks Pete,

Yes - with No.1 on its firing stroke the rotor arm is pointing at No. 1 plug lead (which does go to the correct cylinder. The leads are also in the right order, CCW around the distributor 1342 as you suggest.

I also checked and reset the carburettors this afternoon; I wound the jets back up so the top was level with the bridge than wound each down 12 flats to get a starting position. I don't think its a fuelling issue though, and the carbs were rebuilt by Andy T. Whats confusing me is the motors refusal to run when I set the timing to 8 degrees BTDC, either statically or dynamically. I assume this may not be the perfect setting for this cam, but it should at least get me started?

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cam timing even out by a few degrees either way should allow the engine to start if everything else is good.you may have to open the throttles slightly,richen the mixture or swing the timing some more.correct cam timing is more relevant to producing power within its designed operating envelope.
do you have an original dizzy you can install just to get it running and maybe help point to the problem.it sounds like a mismatch with the 123 dizzy somewhere.
an engine needs what it needs in respect of timing and fuel so don't always go by the book and think this must be so.

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Think i'm getting somewhere with this. I thought the default map on the 123 would get me started but not so. I found a spit 1500 profile on here and set that up and it's running better, but still not quite there yet. If anyone has any profiles they use for a 123 Tune for a stage 2 1300 i'd be interested to try.


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