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I bought a 1997 Commander near the end of last season. It has a Marine power 454 with a Holley carb on it. Boat came from Havasu and I live outside Durango, CO read 6000+ ft elevation. I boat here at Navajo lake, but also go to Phoenix, AZ to see family often. Are there any marine carbs I should look at that can change jetting easily ? Thanks boys I know this is THE place for good info.
Cheers !
Ron
 

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Simplest thing to do would be to install Holley's quick jet change bowls and a jet "wrench". That way you do not have to remove the bowls for a jet change.
Another solution would be to install the ProForm "dial-a-jet kit". All jetting adjustments are external on the top of the replaced metering blocks. I think they still sell these kits. Google it. Jocko
 

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Air Density gauge

Invest in an "Air Density" gauge and learn how to use it. Buy an assortment of jets, and a notebook. Once you establish a "baseline" of performance at either end of your travels, high or low, you'll be able to make the necessary changes based on "Data", and not some wild guess.... Write it ALL down for future use, you'll be the talk of the lakes when you "hit the tune up" right off the trailer...
Ray
 

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Invest in an "Air Density" gauge and learn how to use it. Buy an assortment of jets, and a notebook. Once you establish a "baseline" of performance at either end of your travels, high or low, you'll be able to make the necessary changes based on "Data", and not some wild guess.... Write it ALL down for future use, you'll be the talk of the lakes when you "hit the tune up" right off the trailer...
Ray
thats good info right there! You can change jets in a heart beat once you know what works at 6k and what works when the air gets thicker(so to speak) at 1k. Plugs tell the story and a weather station can get confusing. M
 

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Holley carburetors are about as simple to change main jets on as any.
NO! the Holley is probably the worst PITA carb to change jets in. I can't think of another carb that is as bad. Tunable yes, PITA, definitely.
Simplest thing to do would be to install Holley's quick jet change bowls and a jet "wrench". That way you do not have to remove the bowls for a jet change.
Another solution would be to install the ProForm "dial-a-jet kit". All jetting adjustments are external on the top of the replaced metering blocks. I think they still sell these kits. Google it. Jocko
I agree, that would be the easiest. I don't think Proform ever made the externally adjustable blocks. I believe Percy's is the only one making them. Holley did sell them, but I believe they sold the deal to Percy's or Percy's was always making them for Holley and Holley is no longer distributing them. Anyway, they are available.
LINK: Percy's externally adjustable metering plates

The very easiest is Willy's setup, and it doesn't make the carb any longer, and you get a billet metering block in the deal to boot.


By far the easiest CARB to change jets in is what was the old holley 4010 series carbs now sold exclusively by Summit. You can change the jets in these things in less than half the time of a 4150/4160 Holley. And they are available in manual secondary double pumpers in 600 and 750 sizes.




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Bob, your right.......I forgot it was Percy's (not Proform) that made that kit. I put one on a generic 1850 Holley on my roadster and it worked really good. It did extend the carb length as you said, requiring longer bowl transfer tubes included in the kit. Jocko
 

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Discussion Starter #8
Thanks guys ! I knew I came to the right place. All great suggestions, I like the idea of the air density gauge and getting my set up dialed just right. I'm off to do my homework !
Cheers
Ron
 

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Dare I even say it? It's true, why not?

...Are there any marine carbs I should look at that can change jetting easily ?
The metering rods (jetting) in a Carter AFB style (Edelbrock) carburetor are THE quickest, cleanest, and easiest to change... At least in my personal experience. It can be done in less than a minute, probably closer to 30 seconds if you don't count the time it takes to remove the air cleaner.

They are less understood, so less average engine guy tuning advice is available, but it is available. If a simple jetting change is what your after, this may be your ticket. I'm pretty sure Edelbrock has a marine version.

-Seth-
 

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The metering rods (jetting) in a Carter AFB style (Edelbrock) carburetor are THE quickest, cleanest, and easiest to change... At least in my personal experience. It can be done in less than a minute, probably closer to 30 seconds if you don't count the time it takes to remove the air cleaner.

They are less understood, so less average engine guy tuning advice is available, but it is available. If a simple jetting change is what your after, this may be your ticket. I'm pretty sure Edelbrock has a marine version.

-Seth-
The rods in a Carter/Edelrock are not a true jet change but more of a fuel curve trim. No different than the needle in a M/C carb slide. You don't re jet a bike with the needle, you trim the fuel curve with it. They will make an overall A/F change, but its minor compared to a jet change. Not usually enough for an altitude change, or a serious air density change.
Also, they are vac operated and double as the fuel enrichment like a Holley PV
If you are looking for an across the board fuel delivery change, you have to go inside and change the jets just like a Holley 4010.



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Gn7 Have you looked at a EDE tunning manual lately, up to 22%. Prob. with the EDE is they never keep the power tip constant,like the best carb for this app the Q-Jet. Not too easy to change primaries like the others but who cruises anyway. Q-Jet sec. rod adj. 40 seconds.
 

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Gn7 Have you looked at a EDE tunning manual lately, up to 22%. Prob. with the EDE is they never keep the power tip constant,like the best carb for this app the Q-Jet. Not too easy to change primaries like the others but who cruises anyway. Q-Jet sec. rod adj. 40 seconds.
Like I said, it will change the jetting, but its design is to change the CURVE,
AND it is VAC dependent. So its not only like changing a jet, its also like changing the VAC number and the PVR as well, all at the same time. Not EXACTLY the EASIEST change in the carb tuning for alttitude/air density change.

When I make a change in a Holley, I usually don't change ALL those things at the same time, specially because I climbed a few thousand feet, or the weather changed.



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You have a holley, get the Percys frt. and rr. ($270) And an O2 and AD gauge ($370 5-wire and $120), and the binder and pen ($8) and a dyno with a good opperator to enterpolate the numbers ($625). Or just read the plugs! I dont think its going to hurt its self if its too rich. Oh, get the dry tips so the O2 wont crumble. ($600-$6800) Oh boy! I think you just bought (dare I say it) E F I
 

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The rods in a Carter/Edelrock are not a true jet change but more of a fuel curve trim. No different than the needle in a M/C carb slide. You don't re jet a bike with the needle, you trim the fuel curve with it. They will make an overall A/F change, but its minor compared to a jet change. Not usually enough for an altitude change, or a serious air density change.
Also, they are vac operated and double as the fuel enrichment like a Holley PV
If you are looking for an across the board fuel delivery change, you have to go inside and change the jets just like a Holley 4010.
I know that you know what you're talking about, just clearing a few things up for accuracy.

There are, in fact, 4 screw in jets in an AFB style carburetor.
The secondary jets meter fuel in the traditional sense, solely based on the diameter (area) of the hole in the jet. (along with air bleeds, but we'll leave that alone for now)
The primary side of the carburetor uses a large jet and a metering rod. The metering rod has two distinct diameters (thin at the tip and thicker above) and slides up and down inside the jet, increasing and reducing the overall area of the jet and fuel flow based on engine vacuum.
The larger portion of the metering rod (and its relation in size to the jet) could be compared to a main jet in a Holley. Changing the diameter of this portion of the rod IS IN FACT directly related to a jet change when speaking in Holley terminology. However, it's the combination of the jet and metering rod that is important, not one or the other.

Navaho Lake is at 6086' elevation and Phoenix is 1124', a difference of 4962 (5000). A quick look at Edelbrocks Reference chart reveals this MAY be able to be tuned with a simple metering rod change. Although, I agree with you, it probably will need a different jet(s) and metering rod to get it spot on. (Intentionally left out other air density factors for simplicity)


Like I said, it will change the jetting, but its design is to change the CURVE,
AND it is VAC dependent. So its not only like changing a jet, its also like changing the VAC number and the PVR as well, all at the same time. Not EXACTLY the EASIEST change in the carb tuning for alttitude/air density change.

When I make a change in a Holley, I usually don't change ALL those things at the same time, specially because I climbed a few thousand feet, or the weather changed.
I completely disagree on this statement.

The thin part of the metering rod (and it's relation in size to the jet) determines the amount of fuel that flows through the jet under high load (low vacuum) situations. The metering rod in and of itself, has absolutely nothing to do with vacuum at all, ONLY fuel volume (flow). Basically a Power Valve Circuit Restrictor (PVCR) in Holley terms.

However, changing the spring under the metering rod is just like changing a Power Valve VAC number on a Holley and will determine the point of vacuum it takes to enrich the AFR.

Either can be changed independently and have their own function.

I think your use or the term "CURVE" is very loose. Any change to any carb will change the "curve".

If my goal was easy jet changes, the AFB would be my choice. Even if I did have to pop the lid off. Very easy and quick... and no mess. Although any of the other carbs mentioned will work well too.
 

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If my goal was easy jet changes, the AFB would be my choice. Even if I did have to pop the lid off. Very easy and quick... and no mess. Although any of the other carbs mentioned will work well too.
No different than the Holley 4010 I posted in my first post. Same exact design, only the jets and PVs are much more common and easier to get almost any where. And the tuning is the same as any other Hiolley. Same jets, same PV. If you can tune a Holley 4150, you can tune a 4010. Can't say the same for a Edelbrock/Carter.

Yes, you can "jet" a Edelbrock/Carter with just the rods. You can also tune a with just the PVRs, but that doesn't make it the RIGHT tune.
Jets in a Holley have little to do with the CURVE. They simply raise and lower the curve. They don't reshape it. The rods in the Edelbrock do infact RESHAPE the curve if you change the taper. If the taper changes the same percentage top to bottom, the curve remains the the same. Not ALL rods follow the same taper. Wrong rod, wrong curve. A simple Holley jet change does not make a change in the curve. Any more than the jet ALONE in the Edelbrock does.

The needle in the Edelbrock is more like changing the PVR in the Holley.
You can keep the EXACT lowe RPM A/F and change just the hi RPM A/F using just the rods. Thats a fuel curve!



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No different than the Holley 4010 I posted in my first post. Same exact design, only the jets and PVs are much more common and easier to get almost any where. And the tuning is the same as any other Hiolley. Same jets, same PV. If you can tune a Holley 4150, you can tune a 4010. Can't say the same for a Edelbrock/Carter.
I absolutely agree. This would be a great choice, and for the reasons stated... probably the smarter choice, given the circumstances.

Yes, you can "jet" a Edelbrock/Carter with just the rods. You can also tune a with just the PVRs, but that doesn't make it the RIGHT tune.
Jets in a Holley have little to do with the CURVE. They simply raise and lower the curve. They don't reshape it. The rods in the Edelbrock do infact RESHAPE the curve if you change the taper. If the taper changes the same percentage top to bottom, the curve remains the the same. Not ALL rods follow the same taper. Wrong rod, wrong curve. A simple Holley jet change does not make a change in the curve. Any more than the jet ALONE in the Edelbrock does.

The needle in the Edelbrock is more like changing the PVR in the Holley.
You can keep the EXACT lowe RPM A/F and change just the hi RPM A/F using just the rods. Thats a fuel curve!
Are you sure you aren't thinking about Quadrajet metering rods? Comparatively, your experience FAR outweighs mine. But, all the AFB metering rods I've seen are not (per say) tapered. Yes, there is a considerably small section that transitions between the thick and thin part of the rod that is tapered. I assume it is there to avoid turbulence that a sharp "step" would create in the fuel stream. The rods are sold in distinct diameters, .075" x .047" for example, and appear not to have a taper to them at all. One distinct diameter, a transition, and another distinct diameter.

Q-jet Metering Rod


AFB Metering Rod
 

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Yeah, you could be right about that. It is possible that Eddy rods are straight. And if they all are, then they would not change the curve, just move it. Every "rod" type carb I have ever worked on has had tapered rods like the Qjet and M/C carbs. If you say that the Eddy's all have straight rods, then yes, you are correct. Although they are very tunable, and Eddy does have a great chart system for tuning them, they aren't the easiest carb in the world to get jets and rods for "in the real world". That would be my single biggest reason for not recommending one in this application. They do hold their tune quite well, no gaskets below the fuel level and very few parts. Its why I have always like them for street use.

Never really understood why the Holley 4010 never caught on. Really its just a Autolite carb for the most part. Maybe thats why:happy:



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