So I installed lighting headers on my 496 and tested yesterday..boat picked up about 300 rpm and some mph. Boat idles better cruises better and alot more responsive over the old log manifolds. However at 4000 rpm cruising to 5000 rpm wot theres a surging sound w/no change in rpm doesn't seem to miss and its only a sound you can't feel it in the boat..any ideas Thanks in advance..
You may want to hook up the water to the boat on the trailer and besure that you are getting the right amount of water flow, you maybe hereing a water surge through the pipes, meaning you may not be getting a good flow of water through. through transom or no? check and make sure there are no kinks in the water lines!! just my .02
Sounds like it is lean.
as far as the water issue im still running the same setup with a ball valve off pump, no press regulator. water in through water pump openings out of thermostat housing to headers. Lightning headers are through transom w/ 4" tips..also I have not checked plugs so the lean idea may just be the answer..the only change was the headers.woud this require more jetting at the same RPM...Prior to the headers the engine only spun about 4600 RPM
yes it will require jetting it up a few notches. Its breathing easier now and getting more air.
So I installed lighting headers on my 496 and tested yesterday..boat picked up about 300 rpm and some mph. Boat idles better cruises better and alot more responsive over the old log manifolds. However at 4000 rpm cruising to 5000 rpm wot theres a surging sound w/no change in rpm doesn't seem to miss and its only a sound you can't feel it in the boat..any ideas Thanks in advance..
I have noticed the exact same effect at cruising rpm.
I had someone else drive a while, while I looked (oh the wonders of having a covered engine) over the back at the exahust. There was indeed what appeared to be a side to side water "surge". It seemed to momentarilly blow more water out 1 exhaust, then changed to the other, then back again, with the increased noise volume following the outlet with less water flow.
This water difference does not seem possible, but definitely appears to be the case. 2 years of running her, and no problems, so I pay no attention to it any more.
yes it will require jetting it up a few notches. Its breathing easier now and getting more air.
I only went up 1 size. Anything more was too rich, and I wasn't overly rich to start with.
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