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Old 02-11-2011, 09:22 AM
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Help with cam choice for next motor, please

So I am building a '99 Magnum 360 motor for a 71 Scamp. Car supposedly has a "built" 727 3-speed and a stock 7.25" rear end. I have a posi carrier with 2.96 gears to drop in place of the 2.76 peg leg in there now. I also have an 8-3/4" rear end I will build up in the future.

Motor is .030 over, has flat top pistons with 5cc valve reliefs, and has been zero-decked - ready to assemble, just need to pick a cam. Static compression will be around 10.6:1. Though this is a roller block and I have the spider, I don't have the roller lifters, and considering the cost of a roller cam, I was thinking about staying flat tappet hydraulic.

Following the lead from a buddy on one of the mopar boards, I was going to us the Comp XE268H cam, but I was also looking at the Lunati 60402 voodoo cam. I realize the 60402 is a bit smaller than the 268 and is actually closer to the XS262H cam, but I wonder how much cam I really need.

The 60402 Specs are
262/268 Advertised Duration
220/226 duration at .050
112 LSA, 108 ICL is 4 degrees adv
.475/.494 lift at valve
INT opens at 2, closes at 38
EXT opens at 49, closes at -3

The XE268H Specs are
268/280 Advertised Duration
224/230 duration at .050
110 LSA, 106 ICL is 4 degrees adv
.477/.480 lift at valve
INT opens at 28, closes at 60
EXT opens at 74, closes at 26
-values at .006" lift

From what I have read on this and other boards, the voodoo cams seem to be a evolution in development of the comp grinds and can be more gentle on the valve train. I am interested in longevity and "best fit" for the car.

The car will be a weekend driver and I will be looking for an OD trans at some point to add some fwy economy, for now, it's just a fun runner.

Looking for advice and opinions please.

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Old 02-11-2011, 07:43 PM
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cam choice

The 262 is a nice cam for a bit of a step up cam from stock, nice torque, exceptional bottom end, but not a lot diff from stock. The 268 still isn't huge but a cam I use in a lot of engines. You have a good comp ratio with a not so large car, but the gear ratio is a bit lame even for a cruiser, great on the highway. Myself I would use the 268 and change up the ratio to the mid 3 range and it will work great on the highway and in town. If still wanting the higer 2 range maybe use a bit of a convertor to help initial low end. Good luck, hope this helps some.
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Old 02-11-2011, 10:50 PM
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You have several threads active in different forums about this same cam issue, something the board guidelines discourage. I've merged the ones I have access to in the engine forum into this thread.
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Old 02-12-2011, 06:15 AM
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Quote:
Originally Posted by 68NovaSS
You have several threads active in different forums about this same cam issue, something the board guidelines discourage. I've merged the ones I have access to in the engine forum into this thread.
If by several you meant two, then you failed to realize that the threads were about two different motors, the 350 chevy in my truck and the 360 magnum I am building for a car - two distinctly different threads looking at similar cams for two totally different vehicles/uses

Please re-separate them
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Old 02-12-2011, 12:18 PM
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Done.
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Old 02-14-2011, 09:32 AM
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Comp Cams CamQuest

Took at look at Comp's CamQuest application for this build. Choosing initial criterion "5 - High Performance Street - Choppy to mild rough idle" the top 4 cam choices foisted upon me are:
1. XR274HR-10, Great Fit (20-811-9)
2. 283THR7, Great Fit (20-600-9)
3. XR280HR-10, Good Fit (20-812-9)
4. XR268HR-10, Good Fit (20-810-9) smallest cam in the XR family

#1 - listed as a "Retro-Fit HYDRAULIC ROLLER: 3.55-4.10 gears, 2200+ stall, 9:1 compression, headers, high performance street." - I can cover all those bases, but will my magnum heads support .538/.534 lift? DCR with this cam would be 8.712:1

#2 - I don't like the idea of the Thumpr cam, seems gimicky to me. I don't need a car that sounds a certain way, I'd rather one that runs best.

#3 - is the next larger in the XtremeRoller family up from the 274 and is listed is a "Retro-Fit HYDRAULIC ROLLER: 3.91+ gears, 9.5:1 compression, 2500+ stall, aftermarket intake, headers." Until I have OD, and even then, I'm not sure I want to run 3.91 gears, though I have a set that tested good in a SG carrier for an 8.75 housing I have ready to build less axles. Again, with .541/.537 lift, I'm not sure my factory magnum heads won't need some machine work. DCR with this cam would be 8.510:1

#4 - This one appears to be the roller version of the XS268H I am/was originally considering, but the roller version claims much higher lift that again the factory magnum heads probably won't support without machine work. More interestingly, all the valve timing events are 3 degrees later on the HR version than the FT version. The descriptions of the two are a bit interesting too:

XE268H
"Hydraulic-Excellent response, good mileage, Stock converter 3.23-4.10 gear."
-listed as the #2 Great Fit cam by CamQuest behind the 270H (20-214-4)

XR268HR-10
"HYDRAULIC ROLLER: 3.23-3.91 gears, stock converter in 340 & 360, mild converter in 318, 9:1 compression, street machine"

According to Pat Kelley's calc, my DCR with the XE268H and the XR268H-10 it would be 8.905:1

The reason I'm only just looking the first four is because these all have more intake than exhaust lift, but are also all under 236 @ .050" duration cams, with #4 being the most tame of the bunch and capable of using a stock converter in a 360 application - not that that is a limiting factor for me, but it helps me in driving the car until I pick up an OD trans and correct converter sometime in the future.

I think really want to go with a roller cam for longevity and oil-related issues, plus there is no break in to deal with so the obvious issue is choosing the RIGHT cam the first time; not only due to the cost of the cam, but the effort in replacing it. More importantly, I just want to get it right the first time because I considered all the variables and made an educated choice.

Quick questions:

How much lift will a set of factory magnum heads support and are there aftermarket springs like Chevy Beehive springs that will afford more w/o machining the seats?

Do the magnum heads flow characteristics lend themselves to a split pattern cam or will they flow a single pattern (ie 270/270) just as well?

Would another option to ease the lift-issue be to use 1.5 rockers instead of factory 1.6 or is that self defeating?
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Old 02-15-2011, 07:15 AM
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New cam option emerges

Found a seller on ebay that sells factory roller regrinds. I contacted him and he can make me the following cam for my magnum 360 build:

286/298 adv duration
227/236 @ .050"
110 LSA
.480/.480 lift w 1.5 rockers
-I will be using stock magnum heads with 1.6 rockers so the lift would be .512/.512
-overlap would be around 70 degrees

This would net me a DCR down around 8.3

Something else to think about...
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