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Does anyone have any experience with the Clifford 6-8 dual carb setup?

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Curtnut
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Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #1 by Curtnut » Fri Nov 23, 2018 2:43 am

So I’ve recently been given the nod from the Dragon Lady (wife) that I can build a motor for a 66 F100 longbed that was my granddads truck. He bought the thing brand new and it’s been in the family it’s whole life.
The first thought was to stuff a FE big block in it but I like the idea of keeping with the original set up only warmed up a bit.
I’ve done a bit of poking around on here and it seems there is quite a bit of knowledge availabile on this site.
I’ve been a dealer tech for Dodge for twenty plus years but this is the first big six I’ve ever built and I would love some input from people who’ve been working on these things for a while, before I dump a bunch of money and maybe go down the wrong path with the build.
Clifford has what they call the 6=8 package. It’s a dual carb setup with a two piece header. They actually have a blueprint for the lower end as well that seems fairly straight forward. But if I’m going to be spending the money I don’t want to leave power at the table if I dont have to. To be honest the biggest reason I’ve been looking at twin two barrel setup is the principal of air and fuel dispersement being spread out as apposed to the single four barrel setup. That and it looks pretty cool too. They are claiming that as a package it should be putting out around 300 hp and over 400 ft/lbs of torque. How accurate that is is questionable as that’s a sales brochure.
I won’t lie I am not 100% sold on anything yet. I’d like to keep the motor build around 5-6k including machine work. Assembly isn’t an issue I have plenty of experience with that sort of stuff. What I’m really looking for is advice on what can I do to best optimize the money spent. I’ve seen on here people talking about running larger valves and roller rockers. Better airflow is the name of the game. But if I do that am I going to end up starving for fuel and would the twin 38’s be a choke point for air.
I have attached two pictures of the package. What it consists of as well as their recommended blueprint for the build. I am hoping that you might all take a look and see what you think. Does this seem legit or is there a better way to spend the money. I am leaning towards keeping it naturally aspirated. It’s not going to be a race truck by any means. It is also running a C4 slush box with the old Green Dot pattern. I just recently put a shift kit in it and had to clean out the governor assembly as I was having an issue with my two three upshift. I have a bit of a disability that impares my left leg so I will probably be staying with the C4 for now but the gears will need to be swapped as the thing is screaming like a banshee at freeway speeds. Possibly switch to a four speed auto if that’s a possibility in the future. They say you can build a C4 to take the power but it wouldn’t suck to be able to keep fuel in it without breaking the bank.
Please, if you have some time look over what their suggesting and see what you think. If someone has experience with this set up please chime in, good or bad. If there are better options that I’ve overlooked let me know. If you know someone on this site who you think could help, please have them take a look also.
I’m am open to all considerations and would appreciate any and all advice I can get.
Thanks so much for taking the time and I look forward to hearing what you all think.
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THE FRENCHTOWN FLYER
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #2 by THE FRENCHTOWN FLYER » Sat Nov 24, 2018 10:09 pm

First thing: I like the Clifford dual 2V intake for the reasons you mentioned.

Second: Take any advertising claims with a large grain of salt.

Third: If you would like the truck to outlive you into the next generation use EFI exhaust manifolds instead of headers.

Finally: I like Autolite 2150 / 2100 carbs as an inexpensive alternate.

But having said that, the package they offer is a good one. I like to shop around for used stuff.
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

Curtnut
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #3 by Curtnut » Sun Nov 25, 2018 12:41 am

Thanks Frenchie,
Just curious as to the benefit of the EFI manifolds over the headers?
Will they flow as well as the header or am I look8ng for back pressure to help with torque on the low end? (I wouldn’t think that would be a problem for a Big Six)
Thanks,
Curtis

pmuller9
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #4 by pmuller9 » Sun Nov 25, 2018 12:58 am

The Weber 38s flow 390 cfm each for a total of 780 cfm.
The equivalent 4 barrel flow is 780 x .707 = 550 cfm
That will supply enough airflow for what you will be doing.

The 1965 to 1968 300 connecting rods have a .912" piston pin and use Ford 351 V8 pistons. AFAIK there aren't any dedicated 300 pistons for those years. The 1969 and later 300/4.9 have a .975" pin and have a few pistons available.

Your cylinder head has press fit rocker arm studs so if you use a higher lift cam with more spring pressure it is highly recommended to convert to screw-in studs.

The cylinder head is the main restriction to making power above 3500 rpm.
SI valves carries a larger 1.94" intake valve along with a 1.60" exhaust valve.
If you are handy with a die grinder, after the head is machined for the larger valves you can blend the larger throat into the bowl area and do some reshaping of the valve guide in the bowl area.

Use a cam with an .050" duration around 220 degrees which will have around .500" valve lift with a 1.6 ratio rocker.
You have the option to use roller rocker arms.

Set the engine up with a 9:1 compression ratio with the above cam.
Your head has a 76cc combustion chamber.

The Clifford Kit only has 206 degree .050" duration cam (The 264 hydraulic cam). Their next size catalog cam is a little too big
No telling what the pistons are in the kit?
You do not want cast pistons unless they are Hypereutectic.
The other option is forged 4032 aluminum alloy pistons.

In order to get 300+ hp the head needs to be fully ported with larger valves (Intake port flow above 200 cfm @ .500 lift) 650 cfm carb or TBI/EFI equivalent, Cam .050" duration in the 230 range, near 10:1 compression ratio and a header.

Max_Effort
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #5 by Max_Effort » Sun Nov 25, 2018 3:02 pm

I’m going to assume the $899. Is parts only?
What up with the chrome rings? I would not be using chrome unless worried about dirt and dust from off road.
Is it a popular 300-6 deal?

9F410722-7F1F-4A79-BA98-6F069E33BB06.jpeg
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jason832
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #6 by jason832 » Sun Nov 25, 2018 3:57 pm

I bought a used truck with the Clifford "rebuild kit" and all their other parts installed. Here's what it all had

Clifford 4barrel intake
Clifford shorty headers
Clifford valve cover
Clifford cam (208@0.50, .474 lift)
Clifford gears
Screw in studs
Stamped rockers
Clifford Springs
Head Milled 0.60
Bored 0.30
I'm assuming main and rod bearings 0.10, I can go out to the garage and see what they were

Now the funny thing is, the pistons were speed pro H519p 0.30. Honestly you can buy everything on summit that you need and likely come out cheaper. I'd work with a machine shop and see what all bearings and bore you need and go from there. The Clifford cams have made many on this forum including me worried about quality control. Only Clifford parts I'd recommend are the intake for the built in heat passage, and shorty headers as they can be setup to clear the starter.

For the heck of it I threw together a similar parts setup on summit. Came out to 675$ US and I would trust these parts over Cliffords.
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old28racer
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #7 by old28racer » Sun Nov 25, 2018 5:50 pm

Well just to keep in mind, I have a set of name brand headers with complete dual exhaust system on my 1971 F250. The system works great, but as FTF said EFI exhaust manifold are the way to go, my headers already have a few small holes in them and headers on a 240 / 300 inline 6 make changing the starter a pain in the xxx. My 300 has all the torque I will ever need and the EFI exhaust manifold over the headers is not a factor, A complete dual 2 1/2" or 3" exhaust system is a great power & mileage improvement. I will be installing my EFI manifolds in a few months.
Bad Day Racing Is Better Than A Day In The Stands :mrgreen:

Fordman75
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #8 by Fordman75 » Sun Nov 25, 2018 11:37 pm

I would only buy from Clifford the parts you can't get elsewhere. Like their intake manifolds or the finned aluminum valve covers. Everything else I'd get from Summit racing, Jeg's, etc.

I love the Clifford dual carb intake manifold. But like FTF mentioned I would run Autolite 2100 or Motorcraft 2150 2V carbs on them.
Ted

54 Ford F100/F150 4x4
300, NP435 4spd, NP205 transfercase

Soldmy66
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #9 by Soldmy66 » Mon Nov 26, 2018 1:32 pm

Curtnut wrote: ... or am I look8ng for back pressure to help with torque on the low end?


You do not ever need backpressure to help with torque. What you need is a system designed to provide sufficient exhaust gas velocity -- and that has more to do with exhaust system sizing (primary tube diameter (if applicable) and exhaust pipe diameter). Using correctly sized exhaust system/exhaust pipe diameter helps exhaust scavenging.

I hope this helps - the "backpressure to help torque" is a common misconception. A properly designed system with sufficient exhaust gas velocity and little/no backpressure will yield better results than an exhaust system having backpressure.

BigBlue94
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #10 by BigBlue94 » Mon Nov 26, 2018 2:08 pm

I'm running a Clifford single 4bbl manifold and presumably a set of their long tube headers. They are both 15 years old. The headers have no leaks, but were quite dirty with burnt on mud. I had them coated by jet-hot for my build that's nearly complete.
1985 Bronco. 309ci I6, NP435, 4.56 gears, Detroit locker and tru-trac, 4" lift, and 37" swamper tires. The 309 is 9.75:1 CR with a Schneider 140H cam, 4bbl, roller rockers, larger valves, and headers.

F-250 Restorer
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Re: Does anyone have any experience with the Clifford 6-8 dual carb setup?

Post #11 by F-250 Restorer » Sun Dec 09, 2018 11:32 am

I find that very interesting that one of the posters has a set of headers that's been going for 15 years. I have been running my Hedman set for 10+ years. Of course the efi manifolds will last nearly forever, but restrict your flow.

One tip I would toss in here is to use grade 8 studs and crimp nuts on your exhaust, along with a Mr.Gasket #260 gasket, if you can find one. Use the copper anti-seize on the threads into the head. If you run a header, use the thick oem washers to hold the exh. and int. manifolds, but you'll have to grind down one side of those washers to compensate for the header flange and intake being diff. thicknesses.

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