Alternate carb to replace a Quad jet with

[solar7647]

I am thinking about replacing the Quad jet on my 87 4.3l 262ci 205 hp Mercruiser. I am having a problem trying to find info concerning the CFM of the Quad jet, does anyone know this or perhaps the proper size replacement card, I was thinking Holly.

 

[Bondo]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Ayuh,.... Get the marine Edlebrock 650 cfm performer carb...

It's a carbon copy of the carb Merc uses from the factory...

 

[solar7647]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Thanks Bond-o, that was quicker then I thought!

 

[achris]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Bond-o beat me to it, but I would also suggest the Edelbrock 1409... It's a direct replacement for the Weber 4 bbl used after the Q-junk got 'deleted' (see Doctor Who and the Cybermen for more explanations of 'deleted' ). It's 600 CFM.... I would NEVER use a Holley in a boat! (or anywhere else for that matter, plenty of way better carbs around.)

Click -> http://www.edelbrock.com/automotive_new/mc/carbs_acc/marine.shtml
or here -> http://www.jegs.com/i/Edelbrock/350/1409/10002/-1
or here -> http://www.summitracing.com/parts/EDL-1409/
or even -> http://www.amazon.com/Edelbrock-1409-Performer-Secondary-Carburetor/dp/B00062YA80

Even at 5000 rpm a 4.3 litre engine can't pull more than about 330cfm.

Chris..........

 

[John_S]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

There is a calibration kit to convert the 1409 standard SBC V8 calibration to a 4.3L: http://store.edelbrock.com/1485calibrationkitfor1409performercarbon43lv-6.aspx

You probably need a squarebore to spreadbore intake manifold adapter or new intake, along with a new fuel line.

 

[solar7647]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

well i was origionaly holding $600 bucks for this carb replacement just because that seems to be the going price for a Q-jet replacement but you guys got the wheels turning now and as i was looking through the links you provided i cam across this----->http://www.summitracing.com/parts/EDL-2111/Application/?query=Engine+Size%7c4.3L%2f262..... Now i am thinking, you know that intake on the engine is origional and could use replacing and hey with the price of that Edlebrock 1409 and the intake together i still got enough of my budget for shipping! lol You guys think it would work? Looking at the front end were the T-stat housing mounts i see a few extra ports, could just plug them right?

To be honest the cooloing passages in the intake are pretty rough along with the casting it self has seen better days!

Why is it that when getting into a motor and going through these web site i always seem to find more that needs replaced!

 

[achris]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

That's an aluminium manifold, and if used in seawater on a raw water cooled engine will have a shortened lifespan.... Just saying....

 

[solar7647]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

I keep to the fresh water. To far to drive to get to seawater! Good old lake Erie is good enough to satisfy any urge i have for big water.

 

[John_S]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Looks like it would be the right intake for a non-vortec head 4.3L.

The port near the distributer hole is for vacuum. You can plug that, but I would recommend a fitting such that you can easily hook-up a vacuum gauge to it. Will help for tuning carb, and any engine diagnoises down the road.

Two of the front three, look like stardard coolant bypass ports, and if not using any currently, would be just plugged.

The one on the edge of coolant passage I'm not 100% sure of. If it is only to water passage, then plug is fine. Maybe a 4.3L expert knows for sure.

Examine you current thermostat housing, and make sure it will bolt on an not have any clearance issues.

 

[solar7647]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

The T-stat housing has a two bolt pattern, but it looks like Edelbrock allows for several different options. It looks like it would fit, I would just have two open bolt holes that would need a plug. I was thinking the same thing with adding a vacuum gage.

 

[CurrentObsession]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Looks like you have plenty of experience with engines, so this is probably a dumb question, but why not just send the existing carb to a shop to be rebuilt? I did this for a 3.0 I had last year and I loved the fact that they used my exact carb so there was no issues about whether it would fit, etc.

 

[joewithaboat]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Even at 5000 rpm a 4.3 litre engine can't pull more than about 330cfm.

Chris..........

Chris I have always learned from your posts.... but can this be right?
How are you figuring that?

 

[joewithaboat]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

OK just found this....... looks like your spot on, good job!

http://www.4secondsflat.com/Carb_CFM_Calculator.html

 

[achris]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Chris I have always learned from your posts.... but can this be right?
How are you figuring that?

2 ways to work this out.

1. Do the math yourself. The formula is actually very simple. The engine displacement (in litres) /2 (it's a 4 stroke) * max RPM /28.3 (converts from litres to cubic feet) *0.85 (volumetric efficiency of a normal engine, not super/turbo charged or for racing).

4.3 / 2 * 5000 / 28.3 * 0.85 = 322.879.... I call that close enough to 330 (I like a little 'fudge factor' in these types of calculations.)

So, that's method 1, method 2 is go to Summit Racing website and use their on-line calculator (only found it AFTER I posted that figure, but nice to verify my calculation) http://www.summitracing.com/expertadvice/popup.aspx?Control=CFMCalculator

Chris.....

 

[John_S]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Do you think the 750cfm Q-jet was enough?

 

[achris]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Do you think the 750cfm Q-jet was enough?

For a 454? Yep!

It used to amuse me no end when I was younger (am I really that old now? :facepalm when friends would put HUGE carburettors on a small engine, and then wonder why it used more fuel, idled like crap, and didn't go any faster...

Chris..............

 

[John_S]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

According to Merc, it was worth 30HP over the 2brl version, back in '87. While there might have been other engine changes, the cams appeared to be the same.

The 750cfm Q-jets were used on 4.3, 305, 350, and 454. The flexibilitiy of tiny primaries and vacuum sec.

When they changed to webers, the 600-625cfm was on the 4.3, 305, and some 5.7. The 350LX, Mag and above got the 750cfm. Even merc 357 remans still get 750cfm webers, today. The 4.3L reman gets the 600 still.

But, if you run the calculator, it will tell you they are all grossly over carbed. Go figure?

 

[solar7647]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

Looks like you have plenty of experience with engines, so this is probably a dumb question, but why not just send the existing carb to a shop to be rebuilt? I did this for a 3.0 I had last year and I loved the fact that they used my exact carb so there was no issues about whether it would fit, etc.

Cause The currant carb needs new jets and a few other parts so labor and parts is about the price of a hole new carb.

 

[solar7647]

Re: Alternate card to replace a Quad jet with

Re: Alternate card to replace a Quad jet with

According to Merc, it was worth 30HP over the 2brl version, back in '87. While there might have been other engine changes, the cams appeared to be the same.

The 750cfm Q-jets were used on 4.3, 305, 350, and 454. The flexibilitiy of tiny primaries and vacuum sec.

When they changed to webers, the 600-625cfm was on the 4.3, 305, and some 5.7. The 350LX, Mag and above got the 750cfm. Even merc 357 remans still get 750cfm webers, today. The 4.3L reman gets the 600 still.

But, if you run the calculator, it will tell you they are all grossly over carbed. Go figure?

Yea it's funny how that works out.