new engine swap, not running right

[Shea_G]

I swapped out the 4.3 lx with a 95 vortec chevy 350 in my 97 regal 2100 lsr. Still running the original gearing (1.84) but i swapped out the 3 blade 17p prop with a four blade 21p SS. The engine runs great on land with no load, revs up great, starts and idles beautifully but it the water it doesn't want to go over 4000 rpm. It'll work its way up no problem but as soon as i give it a bit more throttle when im at 4k the engine kind of bogs down and doesn't want to go higher and just runs ****ty. Still runs great before and i can get it to 40 mph at 4k rpm. Im running a delco est ignition system and a carter afb 750 cfm marine carb that was originally for a big block.

 

[Bt Doctur]

is the timing advancing correctly
is the fuel delivery adequate
is the carb too large

 

[NHGuy]

You can look up the secondary jet and rod combinations for that carb as used in a 350. Sounds like that's where to be, since it's messing up at higher rpm, which means larger throttle openings.
In fact I saw them in my shop manual, I'll try to look em up later when I'm home. I'm on lunch right now.

 

[Bondo]

Ayuh,..... I'm gonna Guess the 4.3l was killed by detonation,......

Now the V8 is still starvin' for fuel,.....

 

[Shea_G]

The v6 ran great. Until righted manifolds fed it water. Different carb and ignition system.
It happens very suddenly and only under load if that can narrow down where the issue may lie. At 4k it runs great at 4100 it does not.

 

[flyman219]

You say you are running the EST ignition system, I would check the module for full advance at 4K RPMS. With a timing light on the motor at idle you'll be say at 12 degrees, rev up the motor to about 3K (even in neutral on the muffs) for a short bit, the advance should move noticeably up another 10-13 degrees for a total of about 25 degrees. You'll need to check you motor's specs for total advance required. If you are not getting the additional advance you'll need to replace the ignition module in the distributor.

Mike

 

[Shea_G]

're read the delco instructions. Apparently there is a plug that helps you set initial timing that you rremove after setting it. Guess it doesn't let it advance? I left it in, checked advance, got to 26 at 4k. Took it out and got the same result. Which is where it should go to. So guess that means its a carb issue?