engine pinging and backfires and stalls

[stang32]

ok guys, this one is kicking my ass and has me going nuts.
rebuild engine installed, 5.7, thunderbolt 5 with knock sensor. 4 barrel weber. proffesionally rebuilt carb, new knock sensor, new mechanical fuel pump, new ignition sensor and coil, new plugs, wires, installed remote fuel tank to insure good clean gas. timing checked several times , base and advance system ok. the boat will idle and rev in neutral all day long but put a load on it and as you pick up speed and rpms, you'll hear it pinging, if i do not pull back on the throttle, it will backfire and stall out but start right back up. and act the same way.

The carb was rebuilt and then after the 1st occurrence I brought it back to him to go through it again with this issue in mind. He found nothing wrong.

the timing is set up 10 btdc. firing order is correct..
yes, ignition parts are merc. cap/rotor , wires, coil, plugs. all new
even when it is detonating, it still runs smooth, no vibration, no stumbling, nothing to indicate an issue.
last trip out, i tried moving the distributor, and still had detonation advancing and retarding timing
http://www.marineengine.com/boat-forum/newreply.php?do=newreply&p=718927

 

[nola mike]

Have you checked fuel pressure?

 

[stang32]

yes, and even though it was fine ,the pump was original so i installed a new one

 

[Bt Doctur]

Some type of intake leak causing a over lean condition?

 

[tank1949]

Run it w/o knock sensor connected and see if there are any changes. Was base timing set w/o sensor connected???? Do you go back with correct timing mark? Did you replace TC cover? I have seen TC covers with different tab locations.

 

[stang32]

Run it w/o knock sensor connected and see if there are any changes. Was base timing set w/o sensor connected???? Do you go back with correct timing mark? Did you replace TC cover? I have seen TC covers with different tab locations..

i think i did but i have done so much, i cant keep it straight, i will re run it w//o the knock sensor connected, but wouldnt that just cause it to ping more? hte engine was built by an engine builder in NY, i was the installer and fo that, i am tasked with runnong down this issue, as for the t/c, i f memory servie me ciorrect the civer didnt have a tab so i installed one from summit. but that is why i tried to time it by ear while ruuning it under load and moving the distributor.

 

[stang32]

Some type of intake leak causing a over lean condition?

spraying the intake with carb cleaner yeilded no change.

 

[Scott Danforth]

spraying the intake with carb cleaner yeilded no change.

Pinging and backfiring is improper timing, running lean, dirty carb or bad fuel

 

[stang32]

Pinging and backfiring is improper timing, running lean, dirty carb or bad fuel

yes, i know and i addressed timing, carb, fuel and pressure. so i am at a dead end

 

[76SeaRay]

Some new crank timing gears have extra keyway slots that can be used to clock the gear relative to the camshaft. Are you sure the gear is on correctly?

 

[Scott Danforth]

Some new crank timing gears have extra keyway slots that can be used to clock the gear relative to the camshaft. Are you sure the gear is on correctly?

degreeing the cam would catch this

 

[tank1949]

yes, i know and i addressed timing, carb, fuel and pressure. so i am at a dead end

Perhaps you have plug wires on wrong plugs or wires are leaking fire? Been there!

 

[stang32]

i was not the builder, the builder was a professional shop. i was the installer so i have no clue what was done with the cam but i guess i have to dive into it, the problem is, once i pull that cover off, it is all but impossible to reinstall because of the 1 piece oil pan gasket. ill have to drop the pan at least partially.

 

[Scott Danforth]

i was not the builder, the builder was a professional shop. i was the installer so i have no clue what was done with the cam but i guess i have to dive into it, the problem is, once i pull that cover off, it is all but impossible to reinstall because of the 1 piece oil pan gasket. ill have to drop the pan at least partially.

no, you drop the pan fully

and if the builder did his job, he used a rubber gasket which you can pull the pan many many many times prior to replacing.

 

[stang32]

no, you drop the pan fully

and if the builder did his job, he used a rubber gasket which you can pull the pan many many many times prior to replacing.

i have done it by dropping the pan partially, so its hangin by the back 6 bolts. it sucks to do upside down but ive done it.