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454 mag with b&m blower, tech qiestions???

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454 mag with b&m blower, tech qiestions???

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Old 07-22-2009 | 02:24 PM
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Originally Posted by Griff
What happens to the boost past 4200rpms??? Does it increase, or stay flat or decrease???? Its possible the blower belt might be slipping at higher rpms.
Good idea! Another one, is your gas fresh and 93 octane? I would also verify thet your ignition timing is 30-32 degrees above 3000 rpm's.

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Old 07-22-2009 | 04:02 PM
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Originally Posted by PatriYacht
Good idea! Another one, is your gas fresh and 93 octane? I would also verify thet your ignition timing is 30-32 degrees above 3000 rpm's.
i was worried about the gas, so i drained as much as i could, added fresh 93, and even threw in 4-5 gals of 110 race gas just in case there was some old stuff in there...

im pulling th carb tonite, taking it to get cleaned and checked,, when i get it back im gonna get some one to help me check the timming,,

im just frusterated cause this motor/carb/blower/wires/ignition/pumps/belts/ everything, is all the same from the previous owner, and he was getting 5400rpms..? the only difference is fuel pumps and exhaust...? so maby carb gummed up from sitting, but is was supposed to be less than a yr the motor was sitting...
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Old 07-22-2009 | 04:04 PM
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Originally Posted by Griff
What happens to the boost past 4200rpms??? Does it increase, or stay flat or decrease???? Its possible the blower belt might be slipping at higher rpms.
it runns up to 5-6 lbs of boost and holds there....
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Old 07-22-2009 | 04:11 PM
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Check the timing !!!
Just be sure! when it was pulled and reinstalled and moved around we have see the chain or hoist move the dist just a little.
Check it to be sure!!!
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Old 07-23-2009 | 06:29 AM
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you only want 26 deg of timing max with that set up....
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Old 07-23-2009 | 07:40 AM
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To little timing is as bad as too much. Too little will kill the exhaust valves with heat. Do a search, the vast majority here run 28-32. I think this is a pretty mild set up and a couple more degrees will help around the dock.
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Old 07-24-2009 | 12:25 PM
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i lined up a set of headers, i believe their Lightning, should have them next week... i dropped my carb off at a performance carb shop in town, and with just the bowls off, and looking down the plentum, he said it looked bad..??? but i dont know why, the previous owner said it it was running fine last summer?? but i get the carb back today, and will run it this weekend witht he stock exhaust and see what kinds of gains i get, then well check the timming... and next week add headers... trying to 100% eliminate all possible problems.... im runnin out of summer in ohio!!!
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Old 07-24-2009 | 12:28 PM
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also, the boat has 4' GIL tips, but they have a spiril baffel in them,,, the boat is super quiet, is this hurrting perfromance? or just for noise??? should i change these, esp when im running headers??

thanks again everyone...
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Old 07-26-2009 | 01:33 PM
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Originally Posted by Sport 280
Once you get the carb cleaned/setup, and headers you may want to try a 25 pitch mirage + (three blade) prop. You said this engine came out of a twin setup. The 4 blade bravo may be a little to much prop. Plus older bajas run the drive very deep in the water and do not work well with 4 blade props.

The swirl tips do not cause much if any loss of power on engines under 500 cu in. I have a 280 sport with twin 400 hp and I changed out the swirl tips and it made no difference in performance, just better sound.

Good luck with your new boat.
i was worried it was over propped, but it planes out soooo nice, at like 2300 rpms it pulls right out of the water, with tabs all the way up... my 226, had a 330hp, and a 23 3blade,,, and it was a hog out of the hole, i had to burry the tabs if i wanted out in a hurry.... but my friend has a 25 3 blade i can borrow... is your 280 a twin? or single?
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