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BACK FIRE

Posted By: bonefish

BACK FIRE - 01/06/09 04:44 PM

1050 dom,7al3,crank trigg. all i did was build a new short block and put everything back together,now i have to hold the trottle wide open for it to srart and it back fires through the ex.ive benn through the carb,timing ,wires a few times ,WHAT AM I MISSING(no pun intended)
Posted By: Cab_Burge

Re: BACK FIRE - 01/06/09 05:15 PM

Quote:

1050 dom,7al3,crank trigg. all i did was build a new short block and put everything back together,now i have to hold the trottle wide open for it to srart and it back fires through the ex.ive benn through the carb,timing ,wires a few times ,WHAT AM I MISSING(no pun intended)

The basics, valve lash set correctly, firing order with verification of every spark plug wire on the correct cyliner, distributor cap not cracked and so on. I did have one new street Hemi motor that was backfiring on the dyno due to the jetting I changed on a new set of carbs before running them on any motor, put the primary jetting back to stock from the manufacturer and the back firing stop Check the carb jets to make sure there is no trash in the jets plugging them up Same thing on the bleeds IHTHs
Posted By: QWK_ENUF

Re: BACK FIRE - 01/06/09 05:23 PM

ign timing retarded

valve not seated

cam timing
Posted By: aarcuda

Re: BACK FIRE - 01/06/09 05:56 PM

start from the start.

did you degree the cam in. and verify that its in proper? did you adjust the valves right? are the plugs wires correct (check again)
Posted By: bonefish

Re: BACK FIRE - 01/06/09 09:58 PM

ok TOOK EVERYONES ADVICE AND WENT BACK THROUGH.fixed the back fire,i hate to admitt it but i had 2-4 crossed,still had to hold it to the floor to start so i took the carb back apart and i had a 4150 metring block gasket in my dommy now it starts right up.now if i can just get it to idle.
Posted By: aarcuda

Re: BACK FIRE - 01/06/09 10:37 PM

i hate to admit it but plug wires 5 and 7 got me this summer..... DOH!

might wanna take a look at your plugs and get a new set. they are probably tore up. And for idle, you'll want your initial timing pretty high if you have a big cam in there and then you'll be able to back the idle screw back down...
Posted By: Cab_Burge

Re: BACK FIRE - 01/07/09 03:13 AM

Quote:

ok TOOK EVERYONES ADVICE AND WENT BACK THROUGH.fixed the back fire,i hate to admitt it but i had 2-4 crossed,still had to hold it to the floor to start so i took the carb back apart and i had a 4150 metring block gasket in my dommy now it starts right up.now if i can just get it to idle.

what idle speed do you want it to idle at? What brand and size Dominator are you running? Is your carb equipt with power valves or not? If so what vacume rating are you currently using and what is the idle vacume in gear?
Posted By: NITROUSN

Re: BACK FIRE - 01/07/09 04:51 AM

You could of blown the power valves.
Posted By: kens avenger

Re: BACK FIRE - 01/07/09 04:53 AM

Posted By: bonefish

Re: BACK FIRE - 01/07/09 12:43 PM

Quote:

Quote:

ok TOOK EVERYONES ADVICE AND WENT BACK THROUGH.fixed the back fire,i hate to admitt it but i had 2-4 crossed,still had to hold it to the floor to start so i took the carb back apart and i had a 4150 metring block gasket in my dommy now it starts right up.now if i can just get it to idle.

what idle speed do you want it to idle at? What brand and size Dominator are you running? Is your carb equipt with power valves or not? If so what vacume rating are you currently using and what is the idle vacume in gear?

ITS A 8896 NO PV I HAVE To TURN THE AIR SCREWS OUT 2 1/2 TURNS TO GET IT To IDLE, i need it to idle STRONG at 1500 otherwise it kills the motor when i put it in gear.
Posted By: Cab_Burge

Re: BACK FIRE - 01/07/09 06:45 PM

Have you verified that the throttle blades are open the same amount on both ends of the carb.? If not try that, it sounds like your not idling on the idle circuit now. Also, if you can, see what size the idle bleeds are now on all four corners and post that size. You should be able to have the motor idle at 1000 rpm in nuetral and drop around 100 to 200 rpm when you put it in gear. What is the initial timing at now, can you get the motor to idle at 1000 rpm and check the timing? Another easy thing to try to fix the idle is to get some small wire,.020 or smaller and make some short L that will fit into the idle bleeds to see if the current idle bleeds are to big I like to make my carbs idle at or below 800 rpm in gear and only need around 1/4 to 1 full turn out on the idle mixture screws to idle clean and not stink out the exhaust That usually requires custom tuning the idle circuits and the bleed sizes on all four corners
Posted By: bonefish

Re: BACK FIRE - 01/08/09 02:45 AM

i changed from 49 to 53 on the air bleeds and i had to atually had to turn the air screws out even more so i would guess thats the wrong direction,the blades are even,thats one of the first things i do,timing is now at 36 i tried 34 -38 made no diff.its a crank trigg.and the dist is phased in perfect.so i think i really need to consintrate on that idle circut,maby go the other direction with the air bleeds,ill try your wire techneek first that seems like a good idea,
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