Why can a marine carburetor not be used on a street application?

Most marine Holley's have the bowl vent tubes that are a j shape that direct the fuel back into the manifold in case a needle and seat stick. They also typically have different bushings on the throttle blade shafts, seal I believe, but I may be wrong. My 950 was acting up so I sent it back to the builder. I put on a friends old marine 850, did a little tweaking to the idle screws and it ran fine. I wouldn't buy a marine carb for the street but if you had one available, I don't see any issue.

 

Trip wires everywhere as soon as the topic changes to Q-jet.

 

I seem to be in the minority. after years a f*&%ing with old warped and worn q jets I went to an edlebrock thunder series 850 on my GS 455. The car NEVER ran so Strong or was so reliable. Its been 10 years since the change and i havent needed to do ANYTHING to that carb and still runs like the day it was new. Id buy another in a second.

About the boat carb, sure it will work but there are probably better less expensive options, but The guy that said boats may experience lower rpms sounds like a landlubber. My ski boat has a chevy SB with a 4bbl and wide open its set to cruize around 4600-4800 rpm's. You do not usually see that high or sustained RPM on the street too often.

 

Q-jets are complicated, which is why they work well when they work well and run like **** when they don't. Path of least resistance is to take the old carb off and put a new one on, tune it best to fit application and obviously it will get better mileage than what it was replacing, no matter what it was.

..but to say the holley will do better in economy is no doubt because it's being compared to a poorly functioning Q-jet.

As I said, there's a place in the market for either. Logic fails here so we'll just go with the ole barbarian uhg me luv dis or dat cuz me noze bettah den yoo cuz I exerpience dis so it mus be troo for everyone and every application.

Why do you keep insisting no one but you knows how to tune a carb? Is it because you yourself took so long in understanding how one works and finally gave up and went the holley path? Would explain all those Q-jets...

So whatever. I knew I should have just passed this thread by. I have better things to do with my time.

Buy whatever you want, think whatever you want. No sweat off my back. I have nothing to gain by trying to force someone into thinking my way or nothing. A different point of view is all it takes sometimes.

 

I found this carb. It is "Holley like." It is made by Chevrolet Performance, formerly GM Performance. It meets all my requirements: 850 cfm, 4-Barrel, Mechanical Secondaries, Electric Choke. Anybody know anything about this brand, carb, etc. Oh, and it is not a marine carb.

 

It won't be MADE by "Chevrolet Performance", but it may be sold by them.

Provide a link.

First guess: Made by Holley, or made by Demon (which is now owned by the same company that owns Holley.)













The biggest single problem with fuel economy when using a Holley carb, is that almost no-one understands how the power valve system works. Folks change the jets to richen-up the WFO fuel curve, and that is NOT the correct method. The jets and air bleed system are used to set the PART-THROTTLE fuel curve, if you need more fuel at WFO, you should be opening up the Power Valve Channel Restriction behind the power valve. That way you have best economy at part throttle while still supplying enough fuel at WFO.

There is still the design difference that a Holley has an On/Off power enrichment while a Q-Jet uses a variable power enrichment via the metering rods; a Q-Jet has a wonderfully-efficient booster system on the primary side. Taken together, the Q-Jet typically runs more efficiently than a Holley--but if the Holley is tuned PROPERLY, the difference is not so huge as when the Holley is JETTED for max-power.

 

Yeah, I'll have to agree with ya' there, my 509 BBC will cruise about 70 mph at 4000 rpm, then if you jam on it, she'll spin to 6 grand. Unlike a car, once you get to cruise speed, you can't back off the throttle in a boat, it's always under a full load due to the friction of the hull.

 

From my gathering here if you want to use the marine carb then give it a shot. But only if you get it at a cheap price. If this is a brand new carb then I would not buy it and I would just get a regular Holley to use. I live in northeast Ohio and I do not even have a choke on my car. At 70* outside I turn on the electric fuel pump and let it run for a few then pump the gas 4 times and wait about 10 seconds and this car starts up faster than my new car. You live in Florida so you do not even need a choke, or at least I would not worry about it.

I really have nothing against the Q-Jet other than the fact it is a real pain to take apart and if you have to keep changing jets and such to get it tuned in then it can be a real pain. If I was going to really use this carb I would just buy one from one of the gurus here that service this carb, they seem to be very good at the calibrations for the application.

The Q-jet is a old carb and most of the time the throttle blades leak air where the shaft goes through the carb base from my understanding and this has to be rebuilt here. At least with the Holley or any other carb they are new and everything works good on them.

Besides, when the engine is on the floor I don't think the engine cares what carb is on there as long as the jetting is correct.

What the heck are we worried about gas mileage for it is a Hot Rod isn't it?

 

My gas milage has sucked with Holley's and Q-Jets. ou:

 

Just like most Q-jet lovers...

Wild assumptions and insults if someone disagrees

Not that I feel I owe you any response at all, but...

The reason I own a pile of Q-junk is because when I was a GM Tech people would bring their cars to the dealership needing their carbs rebuilt.

The dealership stopped working on carbs 20 years ago...

So I would do carb rebuilds on the side for extra cash:TU:

Its shocking how many people cant even rebuild a carbou:

And if you work on Q-jets, you need a literal freaking JUNKYARD of the things!

And hell no, I don't think I know everything and never once claimed I did...

But Ill believe what I have seen and tested myself over some crap I read on the interweb.

When people go around spreading misinformation and falsehoods that I know for a fact are wrong, Im going to speak up and I don't much care if you think its ''troo'' or not:blast:

 

From the carb ad...

◾Custom-calibrated for the zz572/620 crate engine

◾Recommended for 502 crate engines and suitable for Big-Block engines, including street, competition, towing and off-road vehicles


What exactly are your requirements?

Because this carb would only be needed on the wildest of 350suzzled:

 

I using Kenne Bell's research "Ancient mid 12s secrets for your Buick 350"), as well as others. I want a big carb. I want the convenience of an electric choke. I have basically three choices in carbs (I know there are others). Q jet (I am neutral about it, and I am not crazy about the way they look [that trip wire:bglasses: got me]). Edelbrock (I have never had one let me down), and Holley (no it is not the Holy Grail, but they do have 100 years of experience). Plus I like the look of a Holley. I have the hood cold air vents as streamlined as possible, with out actually modifying the hood grilles. I have a set of ported heads to be put on (one completed and the other just the intake runners left. I have TA 290-94H cam w/TA grooved cam bearings waiting to be installed. That leaves torque converter (2800) and gears (3:4ish). That is the Reader's Digest version. I am keeping track of completed work in my Garage page......

 

Without a wideband it's just a wild guess, but i'm thinking this might be a little (pig) rich on a 350. I'm not sure why the OP is dying for an 850 anyway. A 750 with a vacuum secondary that is properly tuned would be a nice addition. A wideband 02 would be even better money spent.

I'm fortunate to have a q-jet that runs like fuel injection, but I also have two that don't in boxes..

The mighty demon on the turbo car runs like a champ at 14.0 AFR at cruise all day long. 12.2 at 8psi..

 

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I am building a system that is unique, competitive, and fun. I do appreciate all view points. But the bottom line is, I am not sure if there is anyway not to seem obtuse: because I can.

 

You can make an 850 run just fine all day long..

If you really want somrthing unique and fun, check the for sale section..

 

That is where I bought the cam and cam bearings. And I am always on the lookout for parts and ideas. THIS PLACE IS GREAT!

 

No problems with that 12.2? I am at 10.8 and going to pull a little jet out of the secondaries. Thinking I want to be in the mid 11's.

 

I'm spraying a big gulp of water/methanol too at 5psi.. Hig 11s or low 12s is what they Snow suggested with the kit.