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Lifted_tea7.3

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460 Breaking Up
« on: September 19, 2021, 07:59:59 pm »
First and foremost I will admit right off the bat you’re dealing with a millennial here. Not the POS give me everything for nothing kind of millennial though…just the kind who’s only ever dealt with carburetors on small engines. Over the past winter I got my first real boat an all original 82’ CVX-20 last winter and with that my first toy with a carb’d V8. Thing’s ran really good all year except it had some quirks which I believed to be carburetor related and planned to address over the winter when I’d either get the carb flow tested/rebuilt or switch to EFI. These quirks were that I could never “floor” the boat if I was at an idle. If I did “floor” it out of a hole shot it would just break up. It also did this breaking up at about 3/4 throttle. If I put it at 3/4 throttle after I was on plane it would start to break up but if I gave it full throttle after getting up on plane it would stumble a bit at first but then clear up and take off without hesitation. Now today we had it out and ran “normal” but later in the day seamed to be breaking up slightly all over the place now and more exaggerated and noticeable then before. It also seamed to have a random vibration but it had no noticeable consistency. Wasn’t rpm or speed based. Possibly could of been normal water chop vibrations but since the motor was acting up at that point my senses were just heightened. Thing starts up and idles fine and has the power to get on plane and all still…just breaking up a lot now. Thoughts?
  • Boat #1: 1982 Glastron CVX-20
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Knightnight

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Re: 460 Breaking Up
« Reply #1 on: September 21, 2021, 08:54:19 am »
I have a 460 I have been messing with for awhile. I put a new carb on it (quick fuel 600CFM vacuum secondary) (old carb has cracked fuel metering blocks, wasn't marine rated, and rusted all the hell) and distributor on it (noticed my old distributor timing was slightly varying constantly at a constant rpm can causing mis-fires; the mis-fires are sometimes hard to hear on a big block v8 with loud exhaust, there was play in the shaft and bad bushings on a 35 year old distributor).

I was getting slight hesitation on-throttle from idle but I just needed to adjust the accelerator pump arm pressure. I had a tiny bit of slack in my linkage. Once moving though I didnt get any more break up or hesitation. If you are getting hesitation through RPM band I would check your float levels to make sure you are getting enough fuel. The bowls should be half full and adjusted based on fuel PSI. My new carb was factory set to 6.5PSI but I had to adjust it since my mechanical pump only delivers around ~5psi.

Also I would verify your timing settings. My original manual called for 40 degrees all in at 4000 RPM and 10 degrees at idle but 40 degree is nuts/risk of pinging. I am running around 8 degree at idle and all in (mechanical advance only, my distributor maxes at 24), so 32 degree total all in at 3500rpm. I am still able to hit around 5000rpm on a mostly stock 460 packajet.

I am a millennial also.

This video helped:
« Last Edit: September 21, 2021, 09:08:40 am by Knightnight »
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Lifted_tea7.3

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Re: 460 Breaking Up
« Reply #2 on: September 26, 2021, 07:14:21 pm »
I have a 460 I have been messing with for awhile. I put a new carb on it (quick fuel 600CFM vacuum secondary) (old carb has cracked fuel metering blocks, wasn't marine rated, and rusted all the hell) and distributor on it (noticed my old distributor timing was slightly varying constantly at a constant rpm can causing mis-fires; the mis-fires are sometimes hard to hear on a big block v8 with loud exhaust, there was play in the shaft and bad bushings on a 35 year old distributor).

I was getting slight hesitation on-throttle from idle but I just needed to adjust the accelerator pump arm pressure. I had a tiny bit of slack in my linkage. Once moving though I didnt get any more break up or hesitation. If you are getting hesitation through RPM band I would check your float levels to make sure you are getting enough fuel. The bowls should be half full and adjusted based on fuel PSI. My new carb was factory set to 6.5PSI but I had to adjust it since my mechanical pump only delivers around ~5psi.

Also I would verify your timing settings. My original manual called for 40 degrees all in at 4000 RPM and 10 degrees at idle but 40 degree is nuts/risk of pinging. I am running around 8 degree at idle and all in (mechanical advance only, my distributor maxes at 24), so 32 degree total all in at 3500rpm. I am still able to hit around 5000rpm on a mostly stock 460 packajet.

I am a millennial also.

This video helped:


Turned out to be a bad resistor that also fried my condenser. But it was a good experience with setting dwell angle and points and all which I’ve never worked with before. All for not as I’ll be going to electronic ignition this winter but at least I’ll be able to get a few more rides in. Musta had bad resistor/condenser the whole time as all my breaking up was cured and I can hole shot it full throttle without any breaking up.
  • Boat #1: 1982 Glastron CVX-20
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Knightnight

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Re: 460 Breaking Up
« Reply #3 on: October 01, 2021, 04:41:42 pm »
How fast are you able to go now, I can hit 4900 rpm but after 20 seconds if seems I start running out of fuel
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Lifted_tea7.3

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Re: 460 Breaking Up
« Reply #4 on: October 02, 2021, 06:11:38 am »
How fast are you able to go now, I can hit 4900 rpm but after 20 seconds if seems I start running out of fuel

I actually just fixed the tach as well which trouble shooting this issue and it’s saying I’m turning 5,000 rpm at a GPS’d 62 mph.
  • Boat #1: 1982 Glastron CVX-20
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Knightnight

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Re: 460 Breaking Up
« Reply #5 on: October 02, 2021, 06:39:27 am »
Do you have trim? I was only able to get 56 with full tank of gas with trim at 4900rpm according to my tach but I am not sure how accurate the tach is. I measured the 56 at GPS. Based on my light hull and trim I should be able to do like 65mph, but I am only running 30 degrees of timing at 3000 rpm all in, I may up it slightly but I seem to start leaning out at WOT after about 20 seconds or so, so not sure if I have a fuel pump issue.

My dash tach measured around ~900 at idle but I have a lawn mower/digital tach that you wrap coils around spark plug wire and it measures around ~850rpm at idle, not sure which tach is more accurate...

My hull weights 900lbs + 900lbs for 460 engine + 27 gallons of gas (220lbs) + gear (100lbs) + me  = ~2300lbs.

I can't use a wideband due to the center riser wet exhaust..
« Last Edit: October 02, 2021, 06:51:13 am by Knightnight »
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dkcerven352

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Re: 460 Breaking Up
« Reply #6 on: November 20, 2021, 12:46:02 am »
Have you pulled plugs and looked at color?  Sounds lean. When carburetors sit with fuel in them, they tend to get plugged up.
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Knightnight

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Re: 460 Breaking Up
« Reply #7 on: December 06, 2021, 06:15:34 am »
I figured out my issue with fuel starvation at higher rpms, I had a very restrictive fuel filter between the pump and the carb. I already have a fuel/water separator between tank and pump which is good enough for me. Once I removed that restrictive filter, I was able to hit 65mph gps at 5100rpm. It feels like the engine has plenty more past 5100 rpm but I have the spark cut-off set to that given I don't know the internal specs of this 460 and most are rated around max ~5000rpm. I know it was rebuilt at one point and possibly a different cam, but I am playing it safe. I did but a purple 3" place diverter nozzle insert that I plan to test during the next season, maybe I can squeeze out 67-68mph.
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77fordwind

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Re: 460 Breaking Up
« Reply #8 on: December 06, 2021, 08:55:45 pm »
I had a 650 dp on my 460 with a pos fuel pump, switched to a jetted 750 dp with a nice fuel pump/filter and 2"spacer on a performer 460 edelbrock. Night and day difference so im going to a 3 circuit 950 this summer on an air gap manifold .
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Knightnight

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Re: 460 Breaking Up
« Reply #9 on: December 07, 2021, 06:09:37 am »
what RPM do you plan to run with that setup? I am already near 5000rpm which I believe is near max for the engines for longetivity. I have the stock edlebrock performer intake which I believe is good for 5500rpm but I also am running stock 5qt oil pan so I hate to oil starve the engine, gassing it from 3000rpm while cruising and being oil starved. The boat is more pleasure/ski boat than max mph. 70mph+ would get a nice goal and I could probably hit that if I let the engine go to 5500rpm but not sure of longevity.

To hit 6000rpm would probably require different rockers, stiffer springs, and different heads/cam/intake manifold/pistons probably, a lot money for 500 more rpm...
« Last Edit: December 07, 2021, 06:12:11 am by Knightnight »
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77fordwind

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Re: 460 Breaking Up
« Reply #10 on: December 07, 2021, 11:52:49 am »
what RPM do you plan to run with that setup? I am already near 5000rpm which I believe is near max for the engines for longetivity. I have the stock edlebrock performer intake which I believe is good for 5500rpm but I also am running stock 5qt oil pan so I hate to oil starve the engine, gassing it from 3000rpm while cruising and being oil starved. The boat is more pleasure/ski boat than max mph. 70mph+ would get a nice goal and I could probably hit that if I let the engine go to 5500rpm but not sure of longevity.

To hit 6000rpm would probably require different rockers, stiffer springs, and different heads/cam/intake manifold/pistons probably, a lot money for 500 more rpm...
Before i had the motor and pump rebuilt it was 4800rpm max nd i think it did like 60mph tops.It spins the A imp in my 12jc to 5000 all day how it is, itll go a couple hundred more or so but the motor is still fresh and thats what the rev limiter is at for now. 5qt sounds like trouble forsure.well i Hit 67-68 on the gps in my cruiser@ 5000  i dont think id trust it going much faster.
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todsme

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Re: 460 Breaking Up
« Reply #11 on: February 24, 2022, 10:25:29 am »
I have had fuel problems with sticky fuel tank anti-shiphon valves. any crap in your fuel tank or tanks goes through valves before it reaches you filter.
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