93_5.0_gt

i got a car at tha shop that a dude brought me today that has been swapped to carb. fella says it ran quietly when it was efi but since the swap, all it does is spark knocks when you get on the throttle. he has a 650 edelbrock carb, performer 289 intake, 1 inch spacer between the two, and his bottom end is all stock... i cant figure out wtf is going on here as to y its doing this.... any ideas as to why its spark knocking soo badly?

93_5.0_gt

so i guess that no one has ever actually had a carbed car to do this???

brentloftis

Either over advanced timing or low octane gas.... what year, and what do the plugs look like, are they getting hot and discolored?

mustangguy82

what dizzy are they using? vacuum advance or the tfi?

mjr46

check timing, what heads is he using?? and it may have carbon build up on pistons and when it was efi the egr worked in conjunction to mask this issue??

67mustang302

Check the plugs first, that will tell you a lot. You simply can NOT properly tune a carb'd car if you don't know how to read plugs. It may be just too lean. Look and see.

Post pics if you can, clean the threads so there's no oil or anti sieze etc on them, and post pics showing the threads, and a clear view of the ground strap, as well as the porcelein. Also, if you have a scope of some sort(like a doctor's ear scope) or an actual plug reader, then look deep down in the plugs at the base where the porcelein meets the plug body.

93_5.0_gt

he is a completely stock engine from a 90 gt all except for the carb setup. and its using the points dizzy(definately not my first choice of dizzy's). and YEA, its got the bronze gear on it. ill dick around with the plugs this weekend and all that. the car is also running hot quickly(that prollem is getting on my nerves worse than the timing issue)... this guy has issues badly with his car, i may possibly get it off him if it pisses him off much more.

on that running hot thing, why the hell would this stupid car blow water out of the coolant hose port on the radiator soon as it gets warmed up? i swapped the cap and the thermostat today and its still doin this... head gasket?????[&o]

mjr46

as a liquid is heated it expands that is normal and if temp continues to rise liquid will continue to expand unless the overheat issue is cured or temp is regulated...it could be a head gasket and if you believe such perform a block check.....but a malfunctioning cooling system would also contribute to spark knock/detonation cause detonation is a result of excessive combustion chamber temps which when you have such a secondary flame front spontaneously combusts and the knock you hear is a result of the two flame fronts colliding...so in short before going after the detonation issue/spark knock..I'd more so have aproperly operating cooling system as fixing such may kill two birds with one stone

93_5.0_gt

thanks mjr. ill look into this car more this weekend and see why its running hot then see if the spark knock goes away with it.