Offshoreonly.com - Backfire thru carb problem on starbord engine------HELP

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0F124358

Backfire through carb above 1200 rpm

454 MAG. BRAVO (GEN. V) GM 454 V-8 1992-1994 - 0D805069 THRU 0F304999

The serial number range can be either TB4 or TB5. In another thread OP said there is only 4 wires coming from the ICM which makes it a TB4

Timing should be 8* BTDC

Compression 130 to 145 psi

Swap carbs with no change

Edit: no knock sensor or module

I'm thinking Dist module 87-892150Q02
Even more so if the module is the old 2 wire style

Quote:

Originally Posted by F-2 Speedy (Post 4740214)

any ticking sound at idle, collapsed lifter, intake valve way out of adjustment, time to pull a valve cover

No ticking at all. engine stars great and idles smooth. Engine is completely stock and has 450 hours on it.

Valve train or hung valve, doesn’t take much. Pop the valve covers.

spark has to be super screwed up to act that bad without load

I’m still banking on the TB-V f’ing up but only because I’ve had similar happen. Hoping it’s not mechanical.

Quote:

Originally Posted by TomZ (Post 4740302)

I’m still banking on the TB-V f’ing up but only because I’ve had similar happen. Hoping it’s not mechanical.

Was it your module or the pickup in the distributor?

Friend’s boat... He was told the module was bad and unobtainable.

I ordered a Voyager conversion for it and ran the hell out of it.

I guess its time to switch distr. and module and see if its not a mechanical problem.

NEWEST UPDATE---- 5/25/20. swapped over a known good coil, still backfiring. Tried retarding the timing to 0 deg BTDC and even ATDC and still backfiring.
timed engine to 0 deg BTDC, marked the alignment of the #1 tower with the coil tower, spun engine over to 0 deg BTDC on the balancer, pulled the cap off and noticed that the rotor was not pointing towards the #1 tower but was actually about 20 degrees BTDC on #1. Swapped distributors and the engine ran fine and no backfiring. So now 1 of three possible solutions. A bad module, a bad pickup coil, or the rotor was not phased correctly. The module for this distributor is $400 and is obsolete and the pickup coil is another $50. At this point, I dont have ready access to the boat. and have told the guy that we can upgrade both distributors for a little more than the cost of replacing parts on just one distributor. I'm looking either at the DUI distributors (HEI) type distributor or the A-Team Performance (marine HEI ) distributor. I want to replace the whole distributor. Does anyone have personal preference of these two brands or another brand/system that is better?

The A-Team is complete low cost Chyna right ? Compared to medium cost questionable Chy-na things.