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Old 04-28-2011, 10:49 PM   #1
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Best performance cam for Mopar w/ AC?

Hey guys,



I am hoping you can give me some advice. This is my first performance engine build and I canít decide on a cam. My goal is to have a strong street motor that offers decent street manners, but also have enough ***** to give me an erection when I put my lead foot into it. I love the old school big cam lopey idle, but I live in AZ and need my air conditioning too. I think Iíve decided to go with a lower split duration, larger lsa, but still high lift cam. If I choose one of these milder street performance cams, can I still run AC without idle vacuum issues? ( Lunati Voodoo 262, Comp XE268 or XE274) Or would a 110* lsa Mopar Purple 280/.474 cam work ok? Here are my engine specs:


408 stroker (LA block came out of a 79 dodge truck, will be zero decked/stroker crank clearanced and machined for Magnum heads)


Flat top KB Hyper pistons w/ valve reliefs, Scat series 9000 cast crank, Scat I beam rods. (closed chamber stroker kit purchased from Hughes)


Cast iron Magnum heads, 2.02/1.60 valves, 3 angle valve seats, mild porting and push rod angle clearance checked by machine shop


Edelbrock Performer Air Gap intake (Magnum style)


Demon 750 carb


About a 10 or 10:2 to 1 comp ratio


A833 4 speed


Manual disk brakes


Power steering


Thanks in advance for all of your input,
Chuck
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Old 04-28-2011, 11:11 PM   #2
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The type of cam really has no basis on whether you can run air conditioning. If it is a high RPM motor you might want to install a switch to shut the air conditioning off at full throttle. Why not use some eldelbrock aluminum heads on your 360 ??
To get a zero deck will take aprox .040-.050 removed from the block. I had .030 removed (74 360) and took the block back to the machine shop for another .020. You will need to custom fit the intake or the intake to head surface for it to fit

Last edited by TVLynn; 04-28-2011 at 11:26 PM.
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Old 04-28-2011, 11:40 PM   #3
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I was thinking the narrow lsa / wider duration would decrease the engines idle vacuum enough to cause problems when running power accessories like AC, power brakes, and power steering. So I should be able to run one of the cams I listed without issues?
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Old 04-28-2011, 11:46 PM   #4
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I had this set of magnum heads and the intake/carb in my garage already, so I it would save me some money to do the LA/Magnum combo. These parts were thrown in with the purchase of my 66 Belvedere.

I never considered how the zero decking would effect the fit of the intake onto the heads. Would not zero decking the block and using a thinner head gasket be better? Or maybe drop my heads off at the machine shop with the block so they can make sure all pieces seat properly?

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Old 04-29-2011, 06:25 PM   #5
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There is a formula for that. I think that for every .010 you take off the heads, you must take .0127 off the intake surface. Or something like that, I'm not a mathemagician! Getting back to the a/c question....If the car had A/c to begin with, it had a vacuum switch that will cut-out the a/c at full throttle. It probably has, or had a solenoid switch at the carb that acts as a secondary throttle-stop at idle. Its a small, round, cylinder that has a plunger in it, that at idle, extends and keeps the throttle off its normal stop a fraction of an inch to increase rpm when the a/c is on. These can be adjusted if you need more throttle with a lumpy cam.
The head on them can screw in or out for fine adjustment.
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Old 04-30-2011, 02:19 AM   #6
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I would convert to standard brakes if you are concerned about vacuum levels. Power steering just needs a belt just like the air. Have you checked into what is required for the conversion to the magnum heads. The heads are oiled differently

Last edited by TVLynn; 04-30-2011 at 02:21 AM.
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Old 04-30-2011, 02:30 PM   #7
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Quote:
Originally Posted by TVLynn View Post
I would convert to standard brakes if you are concerned about vacuum levels. Power steering just needs a belt just like the air. Have you checked into what is required for the conversion to the magnum heads. The heads are oiled differently
Hollow push-rods.
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Old 04-30-2011, 07:16 PM   #8
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Quote:
Originally Posted by TVLynn View Post
I would convert to standard brakes if you are concerned about vacuum levels. Power steering just needs a belt just like the air. Have you checked into what is required for the conversion to the magnum heads. The heads are oiled differently

Yah! My dad and I have been researching this magnum head conversion for awhile. The oiling holes in the block for the LA heads will be drilled and plugged, hollow push tubes, the pushrod angle clearances will by checked. I was told by Hughes engines that the angle the push tubes feed through the head is slightly steeper. I already have a magnum Eddy air gap intake. I would use all LA motor components if I didn't already have the magnum top end sitting in the garage. I'm building this engine on a tight budget. The cost of hyd flat tap cam/lifters are cheaper than the magnum roller combos too. I bought this complete LA 360 for only $100, so I think I came out ahead on that deal. My machine shop bill may be a little high, but allot of people here in AZ seem to be satisfied customers who have allot of trust in them.
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Old 04-30-2011, 07:23 PM   #9
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Quote:
Originally Posted by scotts74birds View Post
There is a formula for that. I think that for every .010 you take off the heads, you must take .0127 off the intake surface. Or something like that, I'm not a mathemagician! Getting back to the a/c question....If the car had A/c to begin with, it had a vacuum switch that will cut-out the a/c at full throttle. It probably has, or had a solenoid switch at the carb that acts as a secondary throttle-stop at idle. Its a small, round, cylinder that has a plunger in it, that at idle, extends and keeps the throttle off its normal stop a fraction of an inch to increase rpm when the a/c is on. These can be adjusted if you need more throttle with a lumpy cam.
The head on them can screw in or out for fine adjustment.
I'll have to check to see if it has something like that. It didn't come with factory AC though, no AC vents in the dash. I'll be installing vintage air after I get her running. Is this vacuum switch something I could buy via aftermarket or from Mopar?
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Old 04-30-2011, 07:23 PM
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