300 clifford intake and carb

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300 clifford intake and carb

Postby Repeat offender » Wed Oct 27, 2010 4:23 pm

After having the head on my 300 totally re-done I can finally move on to doing some upgrades. I already have a clifford 4 barrel intake manifold and I have access to cheap a 600 cfm Edelbrock carb. I want to use the manifold, but I have only heard of a few people who have used a carb this big(600 cfm). Everyone else I talked to went with a Holley 390 or Edelbrock 500. I was going to possibly go with a propane conversion at one time, but after looking into it I don't think it was what I want to do.

My question is, would the 600 cfm carb be too much on my bone stock 300? I have seen them on hundreds of 302's and the CU IN are very close so I wouldn't think it would be a problem. Eventually I am going to go over to the efi exhaust manifold as well and possibly a different cam. I will be doing it piece at time, but the carb and manifold were going to be first. Any ideas on how this will work?
1982 Ford Bronco 300 l6 rust-bucket. Semi restore in progress, but just enough to keep it a hunting rig.
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Re: 300 clifford intake and carb

Postby THE FRENCHTOWN FLYER » Wed Oct 27, 2010 6:19 pm

bIGGER IS NOT ALWAYS BETTER, AND IN THIS CASE A SMALLER CARB WOULD BE MORE TOWARD THE OPTIMUM. hAVING SAID THAT THE 600 CFM WITH vacuum secondaries will work OK on your engine, but you will never use it to its full 600 cfm potential. A smaller carb will likely run a little crisper at slow speeds. But cheap is good and if cheap it is I would use it.
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Re: 300 clifford intake and carb

Postby Repeat offender » Wed Oct 27, 2010 6:56 pm

Would the efi exhaust and a rv cam do me any good to get the any more potential from the 600 cfm carb?
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Re: 300 clifford intake and carb

Postby CJ455 » Wed Oct 27, 2010 8:01 pm

A CFM calculator will give you an idea of what the engine is capable of taking in.
Just need cubic inch, max rpm, and volumetric efficiency (estimate)
http://www.csgnetwork.com/cfmcalc.html
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Re: 300 clifford intake and carb

Postby Repeat offender » Wed Oct 27, 2010 11:10 pm

Good tool, but what would be the volumetric efficiency of a stock Ford 300?
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Re: 300 clifford intake and carb

Postby 66 E100 Pickup » Thu Oct 28, 2010 12:42 am

pony carbs puts the 240 inline six at 75% VE, 4000 rpm category. 300 is a truck engine, so it isn't listed by pony carbs.

They do jump the 4 barrel 289/302 up to 90% VE, 6000 rpm category.

If you are looking at a performance intake, EFI exhaust, and 4 barrel carb (no head work), I'd say 75% would be about right, 80% optimistic for the 300. Do some porting and larger valves, about 80% or 85% at best.

It's tough to fill the square bore 300 very efficiently...I suspect the 240 has a 5% or so better VE than the 300, due to the longer rods, shorter stroke, and lower cu inches with the same plumbing as the 300.

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Re: 300 clifford intake and carb

Postby Repeat offender » Thu Oct 28, 2010 1:08 pm

What about putting a Weber 38 or 40 with a 2 barrel adapter on. What type of results would that yield?
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Re: 300 clifford intake and carb

Postby 66 E100 Pickup » Thu Oct 28, 2010 1:59 pm

If you mean a 2 barrel adapter on the Clifford intake, I personally like that idea, to the point of having bought a brand new complete setup w/ Weber 38/38 that a guy had bought for his truck and never installed. Haven't installed it yet, so I can't report back.

Just beware, the Weber setup will cost a few hundred extra.

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Re: 300 clifford intake and carb

Postby Repeat offender » Thu Oct 28, 2010 2:12 pm

Do you know of a good source to price/buy new genuine Weber carbs and the adapter to the clifford intake?
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Re: 300 clifford intake and carb

Postby 66 E100 Pickup » Thu Oct 28, 2010 2:22 pm

if you want it NOW and have lots of money, go through Clifford. If you are patient to shop around, you can be better deals through ebay or the buddy system here at F6. The Webers themselves can be had fairly cheap through RedLine. The adapter is possibly a Clifford only thing, or make your own.

The small six guys use the Webers much more than us with BB6's...that's the best place to source them on Ford Six.

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Re: 300 clifford intake and carb

Postby THE FRENCHTOWN FLYER » Thu Oct 28, 2010 4:18 pm

I think you will be just as happy with an Autolite 2V on a Clifford intake. And it just so happens I have nine of them for sale in the want ads section.
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Re: 300 clifford intake and carb

Postby 66 E100 Pickup » Thu Oct 28, 2010 4:49 pm

I agree...I had to get away from the 2300 footprint in order to stuff the carb into the early econoline doghouse. Otherwise I'd be using a small Holley or Autolite 2V.

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Re: 300 clifford intake and carb

Postby Repeat offender » Tue Nov 02, 2010 2:13 pm

Well looks like I am going to go with the Autolite carb eventually, seems to be the best option. Bad news, the wife put a kabosh on spending any more money, with christmas coming and all, but thanks for pointing me in the right direction. I am sure I will need help when the time comes :wink:
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Re: 300 clifford intake and carb

Postby Harte3 » Tue Nov 02, 2010 11:26 pm

A wife sometimes has no sense of humor when it comes to our trucks. :shock:
'83 F150 300, 0.030 over, Offy DP, Holley 4160/1848-1 465 cfm, Comp Cam 260H. P/P head, EFI exhaust manifolds, Walker Y Pipe, Super Cat, Turbo muffler, Recurved DSII, Mallory HyFire 6a, ACCEL Super Stock Coil, Taylor 8mm Wires, EFI plugs.
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Re: 300 clifford intake and carb

Postby Repeat offender » Wed Nov 03, 2010 10:22 am

All too true... :mrgreen: you should have seen her face when I originally brought it home! She was horrified! Wish I could have got her reaction on camera and posted it here, eveyone would have got a good laugh.
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Re: 300 clifford intake and carb

Postby tiresmoke410 » Wed Nov 03, 2010 3:45 pm

You can buy a 4v to 2v adapter from Jegs or summit. probably have to call since they typically don't "waste" magazine space on stuff like that.
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Re: 300 clifford intake and carb

Postby Buddy Rawls » Thu Nov 04, 2010 2:36 pm

You will not have any problem with the 600 cfm carb on your motor. Its a 300 cid motor. when you run the calcs it will show the carb too big. But I have ran 600 and larger on many 290-350 v8 cid motors. Without having to do any sort of odd tuning due to it being too large. In general, too large of carb will not provide a good booster draw, forcing you to jet it richer, whcih in turn causes other problems. I have never had to jet any more than 1-2 sizes differently. even ran a 289 at one point with a 700 double pumper that actually needed to be jetted down on a couple of the holes, indicating very good high velocity inlet draw.

On my 300 six. I am currently running a clifford with a 625 AFB and have had no tuning or running issues whatsoever. When i was running a Offy DP, I would swap between a holley 1850 (600 vac sec) and the same AFB without any issues (once I found the source for the inconsistent vacuum leak). I ended up using the AFB becasue to me it simply looked better than the holley, oriented the way the DP carb is. I orinted the top on the clifford the same way. With the carb facing the cylinder bank, it should be getting better charge distribution. I am getting right around 15 mpg for city and country driving.

running a smaller carb is a plus in that there is some opportunity for economy and response. But the tunability, drivability, etc with the 600 cfm carbs on a 300 cid is not the issue that everyone seems to make it out to be. The carb should bolt right on with the factory jetting and prep and run just fine. the accelerator pump tuning may need some tweaking for perfection.

Many times I have been seeing all these problems on the carbs. Most issues of carbs are from buying a carb that someone else "tweaked" (albeit wrongly, usually). even recently on this board, such a story occurred.

I did a cam for a 10 second combination, in which the motor simply did not perform to expectation (10.90's at best). they insisted on 5-7 sizes richer (it was a race car after all!) regardless of what the A/F said. they never could get it right, and it was OBVIOUSLY the cam's fault. The motor was sold and the new owner bolted his intake/carb/headers and his vehicle ran 10.20's (similar weight) and both capable drag set-ups. MAybe it wasn't the combination afterall, but simply the tuning.
It doesn't run quick at the track, but it gets long stares wherever it goes.
Never in a million years did I think I would have an antique hot rod truck, much less with its own name emblazoned on the front fender and a freakin' six cylinder for power;
but it is a Ford, it is old, and it is definitely one of the funnest vehicles I have driven.
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