[QUOTE=Harte3;13417964]"... jetting has absolutely nothing to do with the engine"

I believe what you are saying is that a given carb will use just about the same jets on different size engines. I agree. The Autolite I mentioned above used .047's on a 390, and .046's on my 300.

But...that doesn't mean a given carb will work equally well on different size engines. Any carb is designed to have a given flow of air, a cfm range, past the venturi, which pulls fuel into the flow. If that cfm drops, then the signal to the boosters is weak and throttle response is poor.

 

Totally agreed.

And it also doesn't mean a given carb with a given jetting will necessarily perform the same on all 300s. Not all 300s are equal.

 

I am selling all my Autolite 4100's, two 480 cfm's and one 600 cfm, and a collection of parts. If all goes well on ebay I should have a Summit carb in a few days.

I also hope to score a wide band sensor at the auto swap meet in Sept.

 

I was shocked to see the price of the Summit carbs went up today, back to $265. But I called and they gave me the $239 price with free shipping.

I should have it in three days. I'll be sure to post some photos and impressions.

 

REALLY looking forward to hearing what you think of this carb, since I'm teetering right now between it and an 80555c. Bummer the price went back up, but at least it wasn't some $100 off special.

 

I need to make up a soft line for the carb. It comes with a duel feed rigid line, but with the DP manifold the rigid line will put my fuel inlet up against the v.cover. So I need to make a new soft line with the fuel supply line in the center.

I don't have experience making up such a line, with braided line and the aviation fittings, and was wondering how difficult it is, and what the cost would be.

Does anyone have experience with this?

 

I dunno about the braided but that sounds like a pita, can you bend the feed line up and get it to clear without kinking anything? Or perhaps putting a spacer under the carb to lift it up? Also call summit they make duel feed braided lines, may be able to find one that sits tighter to the carb and is braided in the middle instead of fixed.

 

You don't have to use braided. The pushlok hose from aeroquip is rated for gas and is much simpler(and less expensive) than the braided. I used it from my fpr to my carb. With the pushlok fittings, it was easy. And you can cut it with regular scissors. You can get it in blue or black. That's what I would recommend. -6an would likely do it.

Something like this:
http://www.summitracing.com/parts/aer-fcv0610/overview/

http://www.summitracing.com/parts/aer-fbm1532

 

Well, looking it over, one thing stuck out before I take it apart to clean any debris from the bowls. That was the hard line. The ends seem to have had molten brass brazed onto them. They are, if fact, still black from the torch flame. Has the double flared end been repaired?



Many have seen other reviews of this carb online. I don't wish to compete with those. I am just a private owner, without financial interest, not doing this as a professional writer getting a check from any party. I wanted to make that clear.

Let me give some background. I was originally attracted to the 4100 three years ago when I first decided to replace a 390 with a 300 inline six. Yes, I paid $500 to have Pony Carbs rebuild a 1.08 venturi 4100 Autolite. Ouch. Although it got great mpg, I still could not work out all the bugs and parted with it. But I was in love with the annular discharge booster. When I found that Summit had brought the Autolite 4100 back to life, and had incorporated many features of Holley carbs (float level windows, floats adjusted from outside the carb, Holley jets, secondary springs, and acc. pump), I had to have one.

Finally, I would not be dealing with a 40+ year old carb. Tomorrow I will remove the air horn (the top), and have a look.

I have to find a wide band o2 sensor to dial it properly.









You can see the annular boosters. I have read they are interchangable with the 4100 boosters. I find it amusing that 'annular' means nothing more than squirting multiple streams of fuel into the in coming air stream from a circular booster, instead of one thick stream like every other carburetor. In the sixties Holley paid Ford to use this technology for the 4010 Holley.

I am hoping to see an improvement in mpg.





I shall have to send away for an insulating gasket without the open plenum. Summit? I've heard some 300 owners say it ran good out of the box. Another said he took the primary jets and put them on the secondaries, dropped two jet sizes on the primaries, and installed a stiffer spring on the secondaries so they barely open. To each their own. Every engine is different. I'm going to run as is and see, then, before too long, I hope a wide band o2 scanner falls into my life. Cheaply. I'm also hoping I don't have to make up a braided line with AN fittings, or an Aeroquip line. With the DP manifold it put the Summit hard line up against the valve cover. If I can find a 90* fitting I'll be alright. Or, I may run the inlet from the other side of the carb, with the input line coming in closer to the passenger fender. I am motivated to save $50+ bucks. As long as it doesn't look Mickey Mouse.

 

" Every engine is different. I'm going to run as is and see,..."

A most excellent way to proceed. Let the games begin!

 

What impresses me is the engineering. By that I mean that Summit has taken a proven design and improved on it. Now the accelerator discharge nozzle is adjustable, as is the idle restriction and air bleeds. And all the parts are Holley. The secondaries can be dialed in later or earlier too. And all the help you need is on the dvd or a phone call away. A person no longer has to call Pony Carbs.

Because of this carb and how Summit took an old design and improved it, I'd be surprised if someone doesn't do the same with the Quadrajet.

 

IIRC the Qjets are very much application specific and I suspect (especially after your write-ups) that a 'generic' Qjet that fits a wide range of applications might be difficult to engineer.

 

As seen by GM's use of the QJ on v6's and big block v8 Caddy engines alike, the QJ can be dialed in to fit any engine. GM tailored it to the intended engine by changing air bleeds, jets, idle restrictions, and acc. pump shot. Just as Summit did with the 4100, those air bleeds and restrictions can be drilled and tapped for screw in/out restrictions can be made so the owner can alter the characteristics of the carb w/o having to drill.

The wise marketing strategy, as Summit did, would be to make it fit the vast sea of medium size v8's, but offer everything you need to dial it in to those owners of 'fringe' engines such as yours and mine.

 

Exactly. The GM engineers had the benefit of a 'lab' to make application specific Qjets. We don't have the benefit of the lab and end up doing a lot of experimentation/tinkering like you did to get one custom tailored to an engine. It seems that an AFB/Edelbrock comes the closest to being an out-of-the-box fit for a wide variety of engines.

 

I think you missed my point, or maybe I was not clear. I meant that I thought another company, like Summit did with the Autolite 4100, would take the QJ and do the research and testing to redesign it into a more 'user friendly' carb, with screw in/out restrictions, etc.