otazup Posted August 3, 2012 Share Posted August 3, 2012 Hey guys i am having a continuing problem with my 302 cleveland, being backfiring out the carb. First a quick run down..... standard cam and heads, edelbrock performer manifold, holley 600 carb, 65 main jets, rebuilt carb, new pump cam, new pump, all adjusted properly (i think). squirts heaps when i look into carb and immediately. carb spacer, new hei distributor etc. The car starts mint, with the slightest pump of gas. idles fine without choke even when stone cold. idles at 1000rpm (manual) and has about 22 showing on the vac gauge with a steady needle. ive done a compression test too with no more variance over 10% of each other. Pretty much the car runs sweet when i drive it, under load and i feel the secondaries slowly ease in, as i should be. but when its parked and in neutral if i floor it flat it will stumble and backfire out the carb and stall, however if i pump the gas up and down quickly, it roars and revs right out. why does it stall when not driving and yet when i do it flat when on the road it kanes it. Does this mean its leaning out? and the secondaries are giving me the extra fuel needed when they come in? ive got no vacuum leaks i know of. but the curve ball is when i pull the plugs they are fouled to fuck. ive tried the timing in all sorts of places. but i havent played with advance curves etc yet but surely out of the box it should still rev at all stages your thoughts are much appreciated cheers jason Quote Link to comment Share on other sites More sharing options...
shizzl Posted August 3, 2012 Share Posted August 3, 2012 sounds to me like its timing...too advanced? Quote Link to comment Share on other sites More sharing options...
otazup Posted August 3, 2012 Author Share Posted August 3, 2012 yeah?? i cant hear any pinging etc and wouldnt that make my plugs white? ive always leaned towards timing i checked it a while back but ive tutooed with it again since. im thinking maybe weights and springs need changing in the msd?and maybe thats why it idles nicely cold and that it could be compensating. Jason Quote Link to comment Share on other sites More sharing options...
cletus Posted August 3, 2012 Share Posted August 3, 2012 # make sure the accelerator pump squirter is squirting fuel as soon as the throttle moves. # idle mixture screw adjustment too lean?, i usually start with 1 1/2 turns out from all the way in. # too much static timing? #leads on right/ firing order correct/ leads in good order, not crossfiring # i had a similar problem with a engine i had , had a 650dp on it, the air cleaner lid was too close to the choke horn, had a stumble on a full throttle stab, didnt do it with the air cleaner lid off. Quote Link to comment Share on other sites More sharing options...
otazup Posted August 3, 2012 Author Share Posted August 3, 2012 hi cletus thanks for the reply my fuel is squirting soon as throttle moves (had this problem previously myself) ive had my mixture screws at 1.1/2, but now are at 2 turns for highest vac at idle could possibly be too much static timing, im gona research this again tomorrow firing order is correct 13726548, plugs and leads both brand new and yes ive tried the air filter thing, i thought because ive got a bug catcher that maybe that was interfering but even with that and filter removed it still does it. im thinking timing like you said. my spark seems quite weak for a new hei dizzy, maybe its faulty? i might try hooking in my 6AL to improve it, but still think i should be able to sort without, plenty of others do. cheers jason Quote Link to comment Share on other sites More sharing options...
otazup Posted August 3, 2012 Author Share Posted August 3, 2012 also has anyone played with pump cams and nozzle squirters? ive got an orange cam and 31 squirter, i thought maybe changing these will change my duration and squirt time. will this cure problems like mine or is it more for fine tuning and extra hp at hi rpm etc Quote Link to comment Share on other sites More sharing options...
yetchh Posted August 3, 2012 Share Posted August 3, 2012 does it ever kick back on the starter? check to see your power valve is the correct size, should be roughly half whatever your vacuum reading is Quote Link to comment Share on other sites More sharing options...
SOHC Posted August 3, 2012 Share Posted August 3, 2012 I had a falcon I put a 302 Cleveland, it would crank and fire then backfire through the carb and the engine would turn backward a cople turns, then it would run mint once it started. The problem was the way the coil was wired up, there was a cranking circuit and a running circuit, the Cleveland's electronic dizzy clashed with the 6 cylinders ballast system. Not saying this your problem but maby s Quote Link to comment Share on other sites More sharing options...
yetchh Posted August 3, 2012 Share Posted August 3, 2012 also, what brand is your dizzy? if its procomp, bin it.. Quote Link to comment Share on other sites More sharing options...
otazup Posted August 3, 2012 Author Share Posted August 3, 2012 its a msd streetfire, basically msds chinese brand i think. im so close to binning it man but surely it cant be that bad brand new? im thinking maybe the advance circuit in its pretty shit Quote Link to comment Share on other sites More sharing options...
yetchh Posted August 3, 2012 Share Posted August 3, 2012 why aren't you running your 6AL? does sounds like a lean condition.. I'd just put the bigger nozzle in and see how it goes.. Quote Link to comment Share on other sites More sharing options...
Valiant Posted August 3, 2012 Share Posted August 3, 2012 Try backing off your jet sizes a couple. If it runs and idles mint even when it's cold and the plugs are fouling suggests it's to ritch. Make sure the plugs are all clean/new before you try it again or you won't get a true result. Or has it backfired and burst a power valve and started sucking fuel through it? Quote Link to comment Share on other sites More sharing options...
otazup Posted August 3, 2012 Author Share Posted August 3, 2012 hi valiant, ive been down to 60s and still done it. i reguarly take the plugs out and clean them. they are 6s, maybe i need hotter ones, and i think my power valve is sweet cause when i turn the screws in the engine dies meaning valve is good. i think rich also. im still gonna concentrate on timing i think curves and a nozzle increase Quote Link to comment Share on other sites More sharing options...
otazup Posted August 3, 2012 Author Share Posted August 3, 2012 and hey i just didnt wire it in cause i didnt want to have to unwire to eliminate again. and ive got to cut 5 wires in the hei to wire it so its abit daunting, haha. yeah i might try a 35 nozzle size and i think the orange pump cam should be sweet thats standard Quote Link to comment Share on other sites More sharing options...
Valiant Posted August 3, 2012 Share Posted August 3, 2012 Was it better, worse or the same with the smaller jets? Quote Link to comment Share on other sites More sharing options...
otazup Posted August 3, 2012 Author Share Posted August 3, 2012 it was hard to say, definately didnt solve the backfire when floored in neutral, but seemed more responsive, i didnt have an exhaust built then. now i do i thought id put the carb back to standard specs to get it running properly, the carb seems mint squirt wise, floats are perfect etc. surely 60s too small for a clevo, my mate has a 302 winsdor and has factory holley with same specs as mine and runs perfect. bastard wont borrow me his carb though haha Quote Link to comment Share on other sites More sharing options...
yetchh Posted August 3, 2012 Share Posted August 3, 2012 hows the float levels in your bowls? have you adjusted the primary's so the transfer slot is square? I have my cleveland running rich enough that I don't need any choke but once it warms up the plugs clean up.. Quote Link to comment Share on other sites More sharing options...
Jase Posted August 3, 2012 Share Posted August 3, 2012 put a vacuum gauge on your trans line and see what its doing in neutral? Quote Link to comment Share on other sites More sharing options...
otazup Posted August 3, 2012 Author Share Posted August 3, 2012 Hey guys, floats are good. I've got the clear sight bungs. And no auto in here sorry man its manual. I've got a vac gauge it reads 22 at idle in neutral. And I'm not sure about setting the primaries? I may have missed that, can u tell me please. Do u know what number/brand of plugs ur running cheers guys Quote Link to comment Share on other sites More sharing options...
yetchh Posted August 3, 2012 Share Posted August 3, 2012 I run NGK BP6S, mine only ever clear after a good run.. To set the primaries you have to pull the carb off and check the amount of transfer slot showing while shut, there should a small square showing (.020") you prob also need to make sure your accel pump isn't bottoming out at WOT, there should still be a small amount of travel there.. Quote Link to comment Share on other sites More sharing options...
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