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jamieson 11-23-2010 05:52 PM

Which cam for supercharged 440 on the street?
1973 Dodge Challenger. 440 with 6-71 supercharger. 440source aluminum heads. 1.5 aluminum roller rockers. 8.5:1 forged pistons. Stock forged crank. Either a 727 or A518 automatic; did not buy a TC yet, but thinking around 2400 stall and open to suggestions. 3.23:1 posi. I do not have tires / wheels yet. Will have P/B and A/C.

Car will be used on the street only so I need a reliable idle and enough vacuum for my brakes and A/C. I just need to to blow the doors off the imports that pull up next to me at stop lights.

I submitted this info to the COMP cams website and they suggested "part number 21-223-4 but I would ask for it to be custom ground on a 114 LSA to better accommodate the supercharger."

I then found a cam that seems similar but already has 114 LSA from Summit. The specs for both cams are pasted below. Would anyone recommend either of these or a different one? I have had decent luck with Summit cams in the past and am willing to use another one.

COMP CamsManufacturer's Part Number
21-223-4Part Type
CamshaftsProduct Line
COMP Cams Xtreme Energy CamshaftsSummit Racing Part Number

Cam Style
Hydraulic flat tappet
Basic Operating RPM Range 1,600-5,800
Intake Duration at 050 inch Lift 224
Exhaust Duration at 050 inch Lift 230
Duration at 050 inch Lift
224 int./230 exh.
Advertised Intake Duration
Advertised Exhaust Duration
Advertised Duration
268 int./280 exh.
Intake Valve Lift with Factory Rocker Arm Ratio
0.477 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio
0.480 in.
Valve Lift with Factory Rocker Arm Ratio
0.477 int./0.480 exh.
Lobe Separation (degrees)
Camshaft Gear Attachment
Computer-Controlled Compatible No
Grind Number CRB XE268H-10
Valve Springs Required Yes


Summit Racing
Manufacturer's Part Number SUM-6401Part Type
CamshaftsProduct Line
Summit Racing® CamshaftsSummit Racing Part Number

Cam Style Hydraulic flat tappet
Basic Operating RPM Range
Intake Duration at 050 inch Lift
Exhaust Duration at 050 inch Lift
Duration at 050 inch Lift
224 int./234 exh.
Advertised Intake Duration
Advertised Exhaust Duration
Advertised Duration
282 int./292 exh.
Intake Valve Lift with Factory Rocker Arm Ratio
0.465 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio
0.488 in.
Valve Lift with Factory Rocker Arm Ratio
0.465 int./0.488 exh.
Lobe Separation (degrees)
Camshaft Gear Attachment
Computer-Controlled Compatible
Valve Springs Required
Camshaft Manufacturers Description
Fair idle, good midrange power camshaft. Requires 9.5:1 and higher compression, 2,000+ stall, and gearing. Good mild bracket racing cam.Quantity


bentwings 11-24-2010 09:45 AM

You may want to look at the Edelbrock Rpm cam. They are 234/246 and .480/.495 lift. I do agree with you lobe center thought. I think it will help the idle vac some.

I put 12k miles on mine (SBC) this year and really like the way it worked. I have a smooth but authoritive idle at 800/850 and it will atually idle at 700 if I want it to. Absolutely no Detroit roll. I won't even drive the car if it does....something is wrong. I get 13 inches of vacuum at 800 rpm. I also use a vacuum advance on the dist. This will give you additional vacuum...2 inches on mine. Much better gas mileage too.
You have the same cruise plans as I do so here are my thoughts.

I use a 2800/3000 converter so the e-brake will hold it in gear. This is a perfect converter for a blown car in my mind. Do get a good one however as you will have enough power to balloon a cheap one.

I'd look at Hoosier Pro Street tires. These are great when it gets wet and have good all around handling. Mine show very little wear after a full year of hotrodding. You don't really need burnouts with these either. Get as big as you will need them with your combo.

As for blowing off the imports....just be carfull....they mine have medical condition after you blast them haha

I normally don't do street racing but a Mini Cooper asked for it one day. All I can say is that I don't think he will be messing around any more with "antique cars" with goofy looking scoops sticking out of the hood. haha

jamieson 11-24-2010 12:23 PM


The detailed reply was much appreciated. Thanks! I will definitely be putting your advice to good use.


bentwings 11-24-2010 04:59 PM

I forgot to note that you will need a 3" exhaust system all the way back. I use 'turbo' mufflers which are ok for my 355. They are much quieter than most but you may have to use less restriction with the big motor. I don't use any cross over....can't see why one is necessary. Too complicated for me. :sweat:

techinspector1 11-24-2010 08:37 PM


Originally Posted by jamieson
"I would ask for it to be custom ground on a 114 LSA to better accommodate the supercharger."

Just so you know, Blower Drive Service, the fellows who have been doing blowers for several decades, recommend 110 LSA on gasoline. They recommend the wider LSA's for use with alcohol. Here's a direct quote....

"The lobe center of the cam will play an important role in determining the performance characteristics of an engine. Wide lobe centers (112 to 114 degrees etc.) will create higher cylinder pressure providing more horsepower with cooler burning fuel such as alcohol and methanol. We have found 110° lobe centers to produce the best overall power on gasoline.
Whatever cam you choose, make sure that it will operate and perform properly in the RPM range required for your application."

I suspect that some time ago, some wise old fellow told another fellow that he should run 114 on alcohol. I further suspect that the word got around that you should use 114 with a blower and that the alcohol part of it was forgotten.

It's like we used to do at a party. You line up 10 people. You tell a simple sentence to the first person and have him whisper it to the second person, who will whisper it to the third person, who will whisper it to the fourth person. By the time the sentence gets to the tenth person and he tells it out loud, it bears absolutely no resemblance to the original sentence. I suspect that's what happened to the 114/alcohol tip.

jamieson 11-24-2010 11:04 PM

Hmmm, very interesting. Now I do not know who to believe... COMP cams or BDS. One knows more about blowers and the other knows more about cams! I'm leaning toward BDS's opinion. You do hear the large LSA opinion a lot though. Maybe the Edelbrock RPM isn't a bad move then.

Thanks for all of the input.

bentwings 11-25-2010 08:51 AM

I have to agree with tech.... especially how the details seem to get forgotten. And I did run a 114 deg alcohol cam back in the 70's.

I paged through Edelbrock's catalog on cams. A vast majority of the RPM cams are 112 deg. There are a few that are not. I suspect that they have more test mule motors laying around than many guys build in a life time. The RPM motors are about the max that you can live with day in and day out. In my own case I ran a single 4 Holley 750 vac at first until the blower was ready. It idled at 1000 rpm min and was really a bear in traffic on a hot day. I had the 3000 converter which was a must. It was all I could do to make the fine adjustments to keep the idle at 900-1000 in gear. It loped hard but I managed to fine tune the AFR at idle to keep it clean enough so I could sit for 10-20 minutes on a hot day in rush hour. It maintained about 10 in of vacuum in gear but that was about it.

Installing the blower made the car a dream to drive. The idle smoothed out and now is about 800 in gear with just a touch of roughness. Just enough to let the car next to you know there are serious horses under the hood. I can idle as long as necessary in traffic any day rain or shine. I made 14 laps around the fair grounds at Back To The 50's never stepped on the gas except to park. 45 min a lap.

Now I don't get paid by Edelbrock but I have to say that I think they have done their home work on their street stuff. They even simply add a blower to the 350 or 383 and instant 500+ hp. Not cheap of course but it is there and on a single 4 bl carb. They claim that they get 10-13 inches of vac (true)which I think is due to the little bit wider lobe sep cams.

I'm sure you make a lot more hp with other cams and better flowing heads but why?? When you are out in the country cruising on 2 lane roads isn't it more fun to just enjoy the ride, step on the gas once in a while for a sec or two and get back in line behind your cruise buddys?? It sure is nice to pull into the gass station, wait your turn and fill up with what ever comes out of the pump and not have to worry about it.

One last little sure to get a good AFR gage either permanent mount or hand held. Its an invaluable tuning device for blowers.

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