GM 262 4.3 V6 Issues – maybe timing? Halp?

Hey guys,
So I’m a long time automotive mechanic, but my niche is European and Asian vehicles, and as ridiculous as it sounds for living in Texas, I’ve never built an American designed engine. The engine in my boat exploded, and needed a rebuild, so I took up the challenge.

The engine is rebuilt, installed and running, but I need some tuning help. So the boat is a 2009 Sea Ray 185 Sport, and came with a 2009 GM 4.3 V6. I couldn’t find a block that matched casting numbers, but I did find a 2002 block in good shape, sent it to the machine shop and had it machined and rebuilt with new bearings, rings, etc etc. I purchased a brand new set of heads (not remanufactured, new production) and installed everything per the manual. I then purchased an Edelbrock Performer intake (for the Vortec heads so it matches) and topped it with an Edelbrock 1409 carburetor. Per Edelbrock, I Installed Edelbrock calibration kit #1485 (which came with new rods and springs) and fired it up.

Now, here comes my stupidity. I’ve literally never used a timing light before this build, so naturally I bumbled through it, didn’t figure it out properly but assumed i’d accomplished what I meant to (because I have nothing if not lots of false bravado.) Come to find out my timing was way off, and apparently I’d used the wrong carb spacer as well. After figuring all this stuff out (and trying to diagnose low power situation) I swapped to the correct carb spacer with four small holes (the spacer is absolutely necessary for the boat – I have to fit a bunch of coolant lines and crap underneath the carb, and the factory carb has at least a 2in spacer built in to accomplish this.) but I still can’t figure out a carb popping issue. It seems that when aggressively increasing throttle, it stumbles a bit on its face, pops a little through the carb then seems to pick up power and gets up on plane. The carb pops were enough to melt the air cleaner I had on it originally (although it turns out I was supposed to have a flame arrester, so I guess no big deal…) and have since gotten better, but it’s still not gone.

Almost everyone I talk to tells me that carb popping is indicative of incorrect timing – apparently it’s less likely to be an incorrectly adjusted carb. I know for 100% fact that the engine is now timed correctly at 10* BTDC (at least according to my harmonic balancer…) but here’s the question – the newer block didn’t fit the original metal timing cover that came off of the blown engine, so I had to purchase a new 2002 timing cover to fit the block. The harmonic balancer part # is identical between the ’02 and the ’09, so I find it hard to believe, but is there any way my old balancer/new timing cover don’t match correctly, and is putting me out of time?

I’ve also repeatedly followed the “mean-best” idle speed adjustment instructions from Edelbrock, I’ve repeatedly adjusted timing to 10*, but the issue is still there.

I guess what I’m asking is, should I just advance the timing to where the engine runs correctly, and forget the timing light? People have said that timing needs will change based on what’s bolted to the engine – is it possible that my combination of 2111 performer manifold, the 1409 carb and a 2″ spacer requires different timing than the engine did standard? Should I try to resolve my obvious timing inconsistencies, or just adjust the dist. until the engine runs right and makes power and then just ignore whatever was originally the problem? I did put the wrong plugs in at first and have since swapped them to the correct copper plugs. My boat doesn’t have any cats or anything to foul up so I guess the worst case scenario for a slightly rich condition would be killing plugs more often than usual which I’m not too worried about, but I’ve put so many hours into learning about these damn engines (on hard mode too, I have no family in this country and my wife’s entire family collectively know less about carbs than I do.) I don’t really know where to find a greybeard locally to school me on how the **** to work on carbs, so I guess for now I’m still bumbling through.

I’ve watched every video on how carbs work and etc etc I can find and I mean I have a basic understanding, but I just have absolutely no experience. Literally, the first time I ever touched a carb was when I bolted this one to my engine.

Looking forward to hearing your advice,

Jon