Camshaft selection for 250, zero deck, 55 cc aluminum head

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62Ranchero200
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Camshaft selection for 250, zero deck, 55 cc aluminum head

Post #1 by 62Ranchero200 » Tue May 14, 2013 3:14 pm

Greetings Ford Six Fans,

My 250 is is finally coming together and I need to order the cam soon so that I have it when the custom pistons arrive.

The 250 is a '74 from a Maverick. It will use early 300 rods and custom forged pistons. The pistons will have a high pin position to bring the piston deck near a zero deck height, and a sizable dish to keep the CR reasonable (static CR 9.6). The aluminum head will complete the ensemble - with 55 cc chambers. Peripheral parts:

CI 1.6:1 adjustable rocker assembly (the roller tipped and full roller rockers are too expensive for my budget)
CI aluminum intake
Autolite or Holley 350 CFM 2 BBL carb (for shock tower clearance, I understand a 4 BBL would have issues)
CI low profile cold air intake
CI three piece headers (polished stainless steel)
May tie into the existing single exhaust for now, but probably Flowmaster(s) eventually
DUI/Livewires
New stock mechanical fuel pump
New stock oil pump
New stock water pump
V-8 3-core radiator
Car has been upgraded to alternator (originally equipped with generator)
Moderate stall speed torque converter (2,000 RPM or less)
C-4
Currently stock 7.25" open differential, 3.50 gears, but probably 8" eventually
Currently manual drum brakes, probably upgrade to manual discs eventually
Manual steering, plan to keep it that way
No A/C

This is all in a '62 Ranchero that weighed 2,400 pounds with its original 170-6 and 3-on-the-tree.

Goal: I'll take all the horsepower that I can get, but stoplight-to-stoplight, off idle torque is my main objective. The Ranchero will be street driven to rallys, car shows, etc, potentially in extremely heavy traffic and 100 degree temps. Don't want it to die at stop lights. Will probably put 93 octane "super unleaded" gas into it whenever I can, but it's possible I might be stuck somewhere with only "regular" unleaded available (87 octane) and I don't want to have to worry if I do so.

My thoughts so far are either the Clay Smith 264/264/110 cam (I ran one before in a 200, idled roughly and moderately low vacuum, but pulled hard mid-range) or the 274/274/108. I considered a solid lifter cam, but they don't start pulling until 2,500 RPM and the RPM range goes up into territory that would be unsafe for my 250. According to Mike, the single springs with dampers that came with my aluminum head are good up to, but not including 280 degree duration cams.

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Thoughts?

Thank you,
Bob the Builder
62 Ranchero, 252 cid, 300 rods, RaceTek pstns, ARP mains bolts & studs, balanced & blueprinted, CI AL head, 1.6 adj rckrs, Smith Bros, 274/274/108 cam, CI int, Holley 500, DSII, CI SS hdrs, PowerMaster strtr and 1wire alt, Optima, V8 rad, T-5z, 10" organic clutch, 5 lug 8" w/3.80 Trac Loc, rear drums, front 5 lug discs, Centerlines. Next: ?.

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FalconSedanDelivery
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Re: Camshaft selection for 250, zero deck, 55 cc aluminum he

Post #2 by FalconSedanDelivery » Tue May 14, 2013 5:45 pm

If money is an issue , stick with the cam you have , Id ditch the DUI and live wires ( waste of money ) for a re-curved Duraspark , some Taylor Spiro Pros and a MSD 6AL , and pocket the over 100.00 savings a mild ( 10 inch for a V-8 ) Converter rated at 2800-3200 ( will flash stall to 2500 tops in your 6cyl , would really wake up the combo , also make sure the 350 Holley Faces the Valve Cover , ( use a bell crank )
Falcon 6's, FE's I Like them both , Sold all My 6 cyl stuff ( for now at least ) glad to pass along some tips though

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Re: Camshaft selection for 250, zero deck, 55 cc aluminum he

Post #3 by 62Ranchero200 » Tue May 14, 2013 9:00 pm

FalconSedanDelivery wrote:If money is an issue , stick with the cam you have , Id ditch the DUI and live wires ( waste of money ) for a re-curved Duraspark , some Taylor Spiro Pros and a MSD 6AL , and pocket the over 100.00 savings a mild ( 10 inch for a V-8 ) Converter rated at 2800-3200 ( will flash stall to 2500 tops in your 6cyl , would really wake up the combo , also make sure the 350 Holley Faces the Valve Cover , ( use a bell crank )


@FSD,

No longer have the 264/264/110 cam I ran in the 200, so I'll have to buy a cam either way, even if I buy another identical 264/264/110.

Already have the DUI, and have probably had it too long to return it for a refund.

So if I understand correctly, the converter will flash at a lower RPM with the six than it would with a V-8? So it will flash at lower than advertised RPM.

When you say the Holley faces the valve cover, do you mean install the carb with the throttle shaft parallel to the crankshaft?

Thanks
Bob
62 Ranchero, 252 cid, 300 rods, RaceTek pstns, ARP mains bolts & studs, balanced & blueprinted, CI AL head, 1.6 adj rckrs, Smith Bros, 274/274/108 cam, CI int, Holley 500, DSII, CI SS hdrs, PowerMaster strtr and 1wire alt, Optima, V8 rad, T-5z, 10" organic clutch, 5 lug 8" w/3.80 Trac Loc, rear drums, front 5 lug discs, Centerlines. Next: ?.

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Re: Camshaft selection for 250, zero deck, 55 cc aluminum he

Post #4 by FalconSedanDelivery » Tue May 14, 2013 9:18 pm

Yes the bowl will face the valve cover , and yes the converter will NOT come close to the advertised flash ,because the industry basis it on a stock 350 V-8 torque spec , so you need to choose about 1000-1500 more than you think you should , now this is for a off the shelf C-4 not a custom built unit
Falcon 6's, FE's I Like them both , Sold all My 6 cyl stuff ( for now at least ) glad to pass along some tips though

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Re: Camshaft selection for 250, zero deck, 55 cc aluminum he

Post #5 by 62Ranchero200 » Wed May 15, 2013 2:04 pm

@FSD,

That's good information about the torque converter and the Holley, but it still leaves my original question unanswered: I no longer have the 264/264/110 cam, and I need to order a cam so that it will be available as the short block is assembled. For longevity, I don't plan to rev the 250 significantly past 5,000 RPM. It will be balanced statically and dynamically, but it's still a long crankshaft that was not designed for high RPM operation. I'm spending so much on this build that I don't want to engage in any unnecessary risks. If a catastrophic failure occurred, I'd probably have to sideline the project for many months, even years.

For the solid lifter cams I have seen, the torque/horsepower curve tends to kick in relatively late for a street-driven car (2,500 RPM and above) and these cams might encourage the engine to rev past 6,000 RPM, which I consider unsafe to do on an ongoing basis. From what I have read, the aluminum head's exhaust ports operate at about 80% of the flow capacity of the intake ports, making a dual pattern cam (more duration on exhaust side) unneccessary. So it seems that a single pattern, hydraulic cam would be my best choice.

I have run the 264/264/110 in a 200 and I generally liked it, but I wondering if I would get more torque output, but still acceptable idle and vacuum, from the 274/274/108. Have several conflicting indications:

As I understand it, any given cam "feels" like a lower duration cam in a larger displacement engine, i.e. any given cam will "feel" like a lower duration cam in a 250 compared to a 200
As I understand it, any given cam "feels" like a higher duration cam with the aluminum head, with it's very large, efficient ports
Will probably go with a moderately high-rated stall speed converter, which will "feel" moderately low stall speed with my 250
Will not use ANY vacuum accessories (manual brakes), so if the engine idles and drives well, don't care too much about good vacuum
Like a lopey idle, but don't want the engine to idle so badly that it stalls at stop lights

Thanks
Bob
62 Ranchero, 252 cid, 300 rods, RaceTek pstns, ARP mains bolts & studs, balanced & blueprinted, CI AL head, 1.6 adj rckrs, Smith Bros, 274/274/108 cam, CI int, Holley 500, DSII, CI SS hdrs, PowerMaster strtr and 1wire alt, Optima, V8 rad, T-5z, 10" organic clutch, 5 lug 8" w/3.80 Trac Loc, rear drums, front 5 lug discs, Centerlines. Next: ?.

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Re: Camshaft selection for 250, zero deck, 55 cc aluminum he

Post #6 by FalconSedanDelivery » Wed May 15, 2013 4:08 pm

OK First the 3.91 stroke is NOT that long , what keeps it from revving is not its length but its lack of being able to make power because of the induction limitation , I work with 4.375 stokes all day and they rev past 7500 The Crane cam in My combo would easily rev to 6000 in your setup ( alum head ) and it has great Idle qualities too , crane will grind it on special order , that being said if you want a available grind , AND you use a converter That I suggested the 278/278-110* Solid Lifter Cam
Product ID: CSC-278-SSP-10
278/278-110* Solid Lifter Cam
Falcon 6's, FE's I Like them both , Sold all My 6 cyl stuff ( for now at least ) glad to pass along some tips though

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Re: Camshaft selection for 250, zero deck, 55 cc aluminum he

Post #7 by MustangSix » Fri May 17, 2013 9:38 am

I think you'll be under-carbureted with just the 350 2bbl on that engine.

With the cam and improved flow thru the head I'd be considering a 500cfm 4bbl. An Edelbrock AVS is more compact than the Holley and is easy to tune.
Jack Collins

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Re: Camshaft selection for 250, zero deck, 55 cc aluminum he

Post #8 by 62Ranchero200 » Fri May 17, 2013 10:13 am

@MustangSix,

On my "round body" Falcon Ranchero, a 4 BBL carb will interfere with the shock towers - as far as I can see, all of the Edelbrock AVS carbs are 4 BBL. I am replacing the factory export braces with removable aftermarket ones, but I don't want to compromise the integrity of the shock towers, which support the motor mounts, by cutting or hammering on them. I'm already replacing the original 170 with a larger, heavier motor of 50% more displacement, and I don't want to weaken the 50-year-old metal of the shock towers.

However, a larger Autolite or Holley carb might be an option (Holley makes a 500 CFM 2 BBL). I'm not a willing carb "tweaker" so I don't want a Weber that needs many adjustments to get just right.

Thanks
Bob the Builder
62 Ranchero, 252 cid, 300 rods, RaceTek pstns, ARP mains bolts & studs, balanced & blueprinted, CI AL head, 1.6 adj rckrs, Smith Bros, 274/274/108 cam, CI int, Holley 500, DSII, CI SS hdrs, PowerMaster strtr and 1wire alt, Optima, V8 rad, T-5z, 10" organic clutch, 5 lug 8" w/3.80 Trac Loc, rear drums, front 5 lug discs, Centerlines. Next: ?.

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Re: Camshaft selection for 250, zero deck, 55 cc aluminum he

Post #9 by FalconSedanDelivery » Fri May 17, 2013 9:49 pm

You Might consider an Edelbrock , they are shorter in length and I bet would fit , the 600 cfm 1406 would be my choice
Falcon 6's, FE's I Like them both , Sold all My 6 cyl stuff ( for now at least ) glad to pass along some tips though

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