388 stroker timing problem

If i set the timing to 12 degrees my engine dont run as good and hesitates and backfires, but if i advance it to 22 degrees on the timing tape at idel, it doesnt hesitate, and doesnt backfire as much. 0 on the crank and timing tab is tdc and compression is good on all cylinders, it only back fires on the drivers side, i have tryed changing carburators but has no affect, i have checked everything from the ignition system to timing and the cam, does anyone have any ideas?


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Hi,
Backfire through the carb?

exhaust backfire

Hi,
Check the intake for a vacuum leak.
Rich

i sprayed starting fluid all over the intake to heads and carb to intake and all fittings, and everything is sealed, i put the #1 pistion at tdc on compression stroke and found the 0 on the crank tape lining up on the 0 on the timing tab.

With everything being checked, I must say
At this time I'm stumped.
Rich

just thought about something, how is your balancer could it have slipped?
rich

do you know what I'm talking about, there is some rubber stuff in the center of the balancer that can break loose & the outside of the balancer slips. This my be your problem as 34* at idle isn't right. 12*built in dist; 22* on dampener=34*
Rich

cracked dist cap. valve adjustment.

thats what i thought it was at first but when i put the engine at tdc and seen that the zeros lined perfectly up, that thought was down the drain. The distributor cap and rotor are tight and fine, the distributo has had a magnetic trigger put in the stock distributor but other then that i belive everything is stock

the valves and rollor rockers are adjusted properly and the cam doesnt have any low spots on any lobes, all the valves move an even amount. i am running 91 fuel also, thought it might help but hasnt really.

what about the distributor gear, can that be wrong or have an affect?

What kind of plug wires and coil? Were either of the carbs custom tuned, or just out-of-the-box and adjusted? What brand carbs?

What parts/ specs on the motor?

msd spark plug wires 8.5mm, Blaster 2 coil, points eliminator/gm distributor, ac delco spark plugs, Edelbrock out of the box 750, Holley 600 older carb, hasnt been changed internally. the motor is a 350 block bored 60 over, with a 383 scat crank, 5.7 rods, flat top hypertunic pistons, vortec heads 1.94/1.50 stock heads, with 1.5 rollor rockers, crane energizer cam with hydrolic lifters, 467 lift both intake and exhaust, timing @.50 opens 6* btdc closes 36* abdc 222 duration, 6 quart oil pan, gm water pump and fuel pump. crosswind vortec intake air gap two plane with air gap. proffesion products harmonic balancer. double rollor timing chain.

Does it backfire run rough at idle and just off idle or what? This engine might need more timing than 12 degrees and need vacuum advance from manifold vacuum. Set the timing for what the engine wants-where you get the highet vacuum reading and back off a little. What is your compression and vacuum? I think this combo should give at least 180psi compression and 15in or so of vacuum. Usually when you get a backfire it means the fuel mixture isn't right. What does the plugs look like, does it look like the engine is running lean? How many turns out from seated are your idle mixture screws and what's your idle speed? The carburetor might just need some adjustment, maybe a bigger idle feed restriction and/or different idle air bleed size.