Please can someone help me. 2 years ago my engine seized. This year I bought a long block along with an engine that had done 10 hours then when taken out of the water, the water froze inside the engine, cracking the manifolds, the ancillary parts were fine and pretty much new.
I have used the doner engine to transfer all the ancillaries onto the new 4.3 block. I have had to replace the wiring loom in the boat and the steering ram for the quick release fittings and new style electrical plug.
I have now installed everything and started it up today. I checked all the timing by getting to TDC after checking compression on no.1 cylinder and lining up marks. I made sure the rotor of the distributor was pointing at no.1 lead and that it worked round clockwise 1-6-5-4-3-2. Everything started up fine, it idled nicely so I did the timing advance to 10 degrees with strobe light (although the revs did tend to drop at the 10 degree mark). All set to give some revs yes? NO!, it just kept backfiring at both ends at about 2500 rpm (mainly through the carb). I read some forums which pointed towards the carb, so I swapped over to my spare carb - did the same thing. I then swapped over the distributor and leads, which were only a year old when the old engine seized. This did improve things a bit as I was able to rev through the backiring range to get a clear rev range between 4000 - 5000 rpm. I swapped over the coil for my old spare one, but it did the same. I haven't checked plugs yet but they were new as they came with the long block. Is there an obvious problem or any ideas of what it could be?
If it idles fine and revs fine at the top range, would this mean that it's unlikely to be (flat cam problem? (I have no idea what that means but a thread was talking about it).
I really hope someone can help as this engineis just driving me crazy.
Thanks
I have used the doner engine to transfer all the ancillaries onto the new 4.3 block. I have had to replace the wiring loom in the boat and the steering ram for the quick release fittings and new style electrical plug.
I have now installed everything and started it up today. I checked all the timing by getting to TDC after checking compression on no.1 cylinder and lining up marks. I made sure the rotor of the distributor was pointing at no.1 lead and that it worked round clockwise 1-6-5-4-3-2. Everything started up fine, it idled nicely so I did the timing advance to 10 degrees with strobe light (although the revs did tend to drop at the 10 degree mark). All set to give some revs yes? NO!, it just kept backfiring at both ends at about 2500 rpm (mainly through the carb). I read some forums which pointed towards the carb, so I swapped over to my spare carb - did the same thing. I then swapped over the distributor and leads, which were only a year old when the old engine seized. This did improve things a bit as I was able to rev through the backiring range to get a clear rev range between 4000 - 5000 rpm. I swapped over the coil for my old spare one, but it did the same. I haven't checked plugs yet but they were new as they came with the long block. Is there an obvious problem or any ideas of what it could be?
If it idles fine and revs fine at the top range, would this mean that it's unlikely to be (flat cam problem? (I have no idea what that means but a thread was talking about it).
I really hope someone can help as this engineis just driving me crazy.
Thanks