SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: beerjet on March 01, 2010, 08:20:24 PM

Title: Upper RPM miss
Post by: beerjet on March 01, 2010, 08:20:24 PM

So I helped my buddy put some minor things together on his Hallett Mini Cruiser and we took it out today.
This is a SKI BOAT!
His wife and several others ski behind it all day if you let them.
He masshes the gas to about 4-4500rpm and there is a slight miss but after a second or two it clears up.
He has one of those tire chaulk carbs (edlebrock) on it and I told him it was the culprit.
I'm thinkin, he's getting a lean condition when he stomps on it.
I think he's getting about 5-6 psi on the fuel, but I guess the edle-junks dont like more psi , or so their web site says.

Any ideas.
or suggestions.

-beerjet-

Title: Re: Upper RPM miss
Post by: enginedoctor on March 01, 2010, 08:41:35 PM

Same as always......
1. Tuning issues
2. valve train issues

Title: Re: Upper RPM miss
Post by: crewchief22 on March 02, 2010, 06:06:37 AM

Quote from: beerjet on March 01, 2010, 08:20:24 PM

I think he's getting about 5-6 psi on the fuel, but I guess the edle-junks dont like more psi , or so their web site says.

-beerjet-

True, the Carter AFB/Edelbrock carbs don't like much fuel pressure.

If you're pretty sure about it being carburetion, have him buy a "strip kit" assortment of jets and needles and start making changes.  Don't forget to write down what was in it to start so you can go back if necessary.  :banghead:

Title: Re: Upper RPM miss
Post by: beerjet on March 02, 2010, 05:36:48 PM

That's kind of the kicker, he said he tried messing with the knobs and if course they didn't do squat unlike the videos on their site says. Other than the miss, it runs like champ.

-beerjet-

Title: Re: Upper RPM miss
Post by: Beaveretriever on March 02, 2010, 06:01:50 PM

put a sight glass in the float bowls and check the level of the floats. my .02 is when the thottle is mashed down the boat rotates alot and sloshes fuel away from the front pick up if the float level is to high, but if its to high then it will over flow and run thru the top of the carb. the demon i have set up on the stock ford motor in the spectra is set up like that and i have no problems.


The Beav

Title: Re: Upper RPM miss
Post by: IRRebel on March 03, 2010, 10:50:03 AM

Kinda sounds like it's WHEN he mashes the throttle it develops this miss. Omar?

If that's the case, it's the powervalve or dirt or both causing it. Did a lot of work with AFB's (Where the Edelbrock came from) back in the day.  The AFB, in my experience, was VERY throttle responsive, tuneable, and why every Hemi powered car had them. Very resilient carb, but you cannot look at it like a Holley. Very different animal.

Ray

Title: Re: Upper RPM miss
Post by: beerjet on March 03, 2010, 11:54:27 AM

Quote from: IRRebel on March 03, 2010, 10:50:03 AM

Kinda sounds like it's WHEN he mashes the throttle it develops this miss. Omar?

If that's the case, it's the powervalve or dirt or both causing it. Did a lot of work with AFB's (Where the Edelbrock came from) back in the day.  The AFB, in my experience, was VERY throttle responsive, tuneable, and why every Hemi powered car had them. Very resilient carb, but you cannot look at it like a Holley. Very different animal.

Ray

It is very responsive.

Quote from: beerjet on March 01, 2010, 08:20:24 PM

He masshes the gas to about 4-4500rpm and there is a slight miss but after a second or two it clears up.

When I drove it, I rolled into the throttle and it didnt skip a beat, only when he flat foots it.
I'll probably talk him into putting a holley I have on it and putting the edlebrock where it belongs, under the tire to keep the trailer from rolling away.

-beerjet-

Title: Re: Upper RPM miss
Post by: IRRebel on March 03, 2010, 11:07:48 PM

That's just a Powervalve (That's what we called them then, on old AFB's and ThermoQuads) issue then. Very simple, and cheap fix. Might need a slight retune after. Bad news, gotta tear it completely down to do it. Simple rebuild kit should solve it, doesn't sound like he needs any hot rod parts in it. In some cases, since the AFB primary throttle shaft pretty much runs everything, could be bent or worn substantially. On old Carters, I can see this, not on a reasonably new Edelbrock.

LOL! I wouldn't do that with it! I kinda feel that way about my Holleys QUITE often, lol. They ain't that user friendly either. All in what you're used to.

BUT, on your side of things, I think he's leaving some performance on the table in CFM, depending on his engine and build. I think most of us agree that 750-850 CFM on a mild build is where we should be on most Big Block engines. The Eddie MAY be leaving a little to be desired in that respect. But what you just described is normal, just with slight PV issues. There's not a screw on the thing to fix that.

Ray