Technical 4 Banger tuning

Looking for help on initial setup/tuning for my mildly hopped up 4 banger.

Stock motor to which I have fitted new tubular inlet and exhaust manifolds, new Stromberg 97, new electronic distributor, plugs and leads etc.

Put the timing pin in at top dead centre then pointed to rotor arm at No.1 plug, carb mixture screws 1 1 1/2 turns out

Starts right up but initially running too fast even with idle screw all the way out, tried adjusting mixture screws in and out but still too fast so turned dizzy until it slowed but now popping and backfiring, Went back and forth trying different adjustments but not running smooth yet.

Is it just a matter of trial and error or is there set method I should follow? ANy help greatly appreciated.

Thanks

 

Vacuum leak ? Do the mixture screws do anything ? Does it stumble when you blip it ? Last one of these that I had was a vacuum leak. Mixture screws had little effect on anything and it didn't take throttle well but would smooth out at any rpm. Average vacuum was a bit low and the needle waved around a bunch. Idle screw was dead. Enough air was getting in through the leak to get it to run fast enough to come off the idle circuit. Good luck, Mike

(Not saying this because of your trick fabricated manifold I like it a lot !)

 

Good point, I'll check that out, All new gaskets fitted so may have to add some sealant if it's leaking
Thanks Mike

 

You backed the idle stop screw all the way out, right? Look into the throttle throat (engine off) and verify that the throttle plates are actually closing. They may be binding or hitting something on the manifold flange.

Backing down the timing to slow it down results in a lazy motor and possible backfire as you have already seen. You could also end up with cherry red exhaust manifolds with retarded timing.

 

^^^ this^^^

Never read anywhere in op's post that mentioned adjusting the idle speed screw, just adjustment screws....

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