Purple Shaft vs XE Comp Cam

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71duster06

71duster06

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I have been reading up on the great reviews for the extreme energy comp cams. Currently I have the Purple Shaft .450, .455 lift which runs great. My goal is to get me car into the high 12's after some tuning. But after reading about the XE cams it sounds like you can get away with a more aggresive cam yet remain streetable. Would it be a good idea to switch over such as the XE 284H or the step below....motor will be disassembled anyways so it would be a good time.
 
i cant wait to hear this one. i have the same cam(3.23 gear)as you and i like it a lot but wonderd if i could make it run better maintain driveability without killing mileage and low end with anouther cam.i thought the xe 268 was a very similar cam.
 
Remember that the original Purple Shafts were designed way back in the day..before computer modeling.

The new modern cams are a big improvement.
 
yellowdartdave said:
Remember that the original Purple Shafts were designed way back in the day..before computer modeling.

The new modern cams are a big improvement.
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although I'm a grate fan of mpp's cams........I would have to agree

Purple cam's are grate, but they need a revise.....

I my self, am change from a .474 purple cam to a less duration more lift cam from LUNATI voodoo (?) cam
 
I'm running the XE275HL in my 360. .525 lift on both sides, but not a wild duration (231/237 @ .050).

Streetable all day long, not an issue at all. I believe the HL series also takes advantage of the wider lobe area that the mopar smallblocks offer, allowing for better life on the street with a higher lift. Can't remember now though. Love it. Motor pulls HARD!
 
la67DartGT said:
I'm running the XE275HL in my 360. .525 lift on both sides, but not a wild duration (231/237 @ .050).

Streetable all day long, not an issue at all. I believe the HL series also takes advantage of the wider lobe area that the mopar smallblocks offer, allowing for better life on the street with a higher lift. Can't remember now though. Love it. Motor pulls HARD!
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I know that the 360's are more tourqey in general but were would you say the best power band is for your motor. Mine revs no problem and Im looking for a bit more low-mid power....pretty much fighting the argument for a cam..haha
 
.450 /.455 lift 228*/231*268/272* 110 ... low 13's ?

you can work on the suspension and lower your ET.
the 268 gives 4* more o lap=scavenge ... and will pull a lil harder on the top.
 
Its impossible to give a camshaft recommendation without knowing a lot more about your combination.

Weight? Displacement? Heads/rebuilt vs stock shortbloc? Stick or Auto? Gear? street/strip? Compression? INtake? Carb? Exhaust?
 
LXguy said:
Its impossible to give a camshaft recommendation without knowing a lot more about your combination.

Weight? Displacement? Heads/rebuilt vs stock shortbloc? Stick or Auto? Gear? street/strip? Compression? INtake? Carb? Exhaust?
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I was focusing more on the differences of the two cams. Currently I have a 71' 340 Duster. About 3000lb with me in the car.
Stock block, bored .03, 10.5 to 1 comp,
3 angle valve grind,
4-speed, centerforce pressure plate, 3.91's (soon to have 3.23's). Primarily street car.
LD340 intake, 850 thermoquad,
2.5" pypes x-pipe w/ cutouts, Dynomax Ultra Flow welded full exhaust.

The car as it sits will do 13's.....have yet to tune it exactly.. But I have heard nothing but good about the comp cams. If its something that would noticably increase my HP or times then thats what I would like to know.
 
I think the Lunati "voodoo" .494/.513 would be perfect for you,you've got the compression for it and your running a 4-speed...mopar cams are old and outdated..
 
71duster06 said:
I was focusing more on the differences of the two cams. Currently I have a 71' 340 Duster. About 3000lb with me in the car.
Stock block, bored .03, 10.5 to 1 comp,
3 angle valve grind,
4-speed, centerforce pressure plate, 3.91's (soon to have 3.23's). Primarily street car.
LD340 intake, 850 thermoquad,
2.5" pypes x-pipe w/ cutouts, Dynomax Ultra Flow welded full exhaust.

The car as it sits will do 13's.....have yet to tune it exactly.. But I have heard nothing but good about the comp cams. If its something that would noticably increase my HP or times then thats what I would like to know.
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If going MP use the .528 solid 284* 241*@.050 112cl

I had the same setup but with .528 solid/750 holley and it ran like a bat outta hell!
 
71duster06 said:
I know that the 360's are more tourqey in general but were would you say the best power band is for your motor. Mine revs no problem and Im looking for a bit more low-mid power....pretty much fighting the argument for a cam..haha
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I don't have a lot to compare it to, but with the 904 behind it it really was strong from bottom to top. It comes on best over 2K though and will pull hard all the way up. I don't have a really good feel for the entire range because i've been fighting transmission woes, and have been finishing the 4 speed conversion over the last few months. The 904 had an 11" PTC 3000 stall converter in it, and really from a stop on up it was strong, normal street driving or full throttle blast. I have no complaints about low end, and definitely no complaints for mid to top end. Strongest though starting at 2k and going up.
 
If the engine is apart, make sure the pistons are really 10.5:1 as they are sitting in your engine. Most are closer to 9.5:1 unless the engine was blueprinted in it's past build. I think there's room to improve what you have, so i wouldnt call that MP done. But for what you're doing I think the XE268 is perfect. The Lunati 268 is another good choice. The Lunati is a little more aggressive in terms of rate of lift over the Comp. Both would need springs matched for them.
 
I pretty much agree with moper,but I would not be afraid of going to the comp xe 274 or 275 hl or the lunati 60404 since you have a four speed.Ive run the xe 274 in a 8.7 compression 360 with great results and its very streetable.
 
I have the XE268H in my 360 with 3.55 gears and the A833OD 4spd. The 360 has a measured 10.6:1 compression. I have run a best of 13.7 @ 102 with a very traction limited 2.2 sec. 60' time. Just sorting out the traction issues off the line should get the car down into the low 13's. This time was also accomplished with a smallish 600 cfm carb.
 
I run an XE268 in my stockish internal 318 with a 2500 TC and 3.23s. It runs well, albeit a tad aggressive for my combo. Still pulls mid 14s easy, with a 14.4 being the best.
 
moper said:
If the engine is apart, make sure the pistons are really 10.5:1 as they are sitting in your engine. Most are closer to 9.5:1 unless the engine was blueprinted in it's past build. I think there's room to improve what you have, so i wouldnt call that MP done. But for what you're doing I think the XE268 is perfect. The Lunati 268 is another good choice. The Lunati is a little more aggressive in terms of rate of lift over the Comp. Both would need springs matched for them.
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Yes, I built this motor a few years ago and made sure to have 10.5-1 pistons...just like stock. Paid the big bucks and got the forged. Runs great but I feel that the motor hasn't come close to reaching its potential.
 
You are going from a 3.91 gear to a 3.23????then you don't want a bigger cam.
Did you ever run your car with slicks at the track???
If you have not, then get slicks first so you can dump the cluck at a higher rpm and improve your 60 foot times.
The second thing i would do is run a bigger tire, if you can, instead of going to a taller gear.
Find out how fast your car is before you change anything.:rolleyes:
 
I have a slightly used compcam XE274 that I took out for a bigger cam if intrested
 
71duster06 said:
Yes, I built this motor a few years ago and made sure to have 10.5-1 pistons...just like stock. Paid the big bucks and got the forged. Runs great but I feel that the motor hasn't come close to reaching its potential.
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Yeah, that's what i said TOO! Until I cc every thing and then said WHAT THE FK!

If you haven't "AKA" blue printed you motor...........which basically means you haven't shaved then 75esh cc combustion chambers down to 64........Well ......sorry man, but you only have 9.4:1 out of a 10.5 piston.

And the 11.5 pistons.......Yeah they are figured on 75 cc combustion chamber...........so your simple choice is 9.4 or 11.5

Not trying to bring you down. They run vary well at 9.4:1

Mine has for over 15 years!:cheers:
 
T67POWER said:
You are going from a 3.91 gear to a 3.23????then you don't want a bigger cam.
Did you ever run your car with slicks at the track???
If you have not, then get slicks first so you can dump the cluck at a higher rpm and improve your 60 foot times.
The second thing i would do is run a bigger tire, if you can, instead of going to a taller gear.
Find out how fast your car is before you change anything.:rolleyes:
Click to expand...

Im hoping to make my car a bit more enjoyable on the street hence going 70mph at 4 grand. 3.23's will help that out but at the same time Im trying to see what I need to do to keep the performance up as well. Sure 3.91's are fun but they are limiting on what you can do other than the track.
 
71duster06 said:
Im hoping to make my car a bit more enjoyable on the street hence going 70mph at 4 grand. 3.23's will help that out but at the same time Im trying to see what I need to do to keep the performance up as well. Sure 3.91's are fun but they are limiting on what you can do other than the track.
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what he's saying though is that its alot easier to just change to a taller tire if you can as opposed to going through a pig swap in the rear end...theres some tire size, rear gear, and tranny gear ratio calculators on the internet...try and find one and play around with them...a taller tire will also give you a bigger footprint, so even though it will reduce the "oomph" of the 3.91's, you will get slightly more traction
 
71duster06 said:
Yes, I built this motor a few years ago and made sure to have 10.5-1 pistons...just like stock. Paid the big bucks and got the forged. Runs great but I feel that the motor hasn't come close to reaching its potential.
Click to expand...

Right... But the stock pistons are really closer to 9:1 in a real engine, and the TRW/Speed Pro "10.5" pistons are only around 9.5:1 with open chamber heads and a typical factory block. You have to deck the block, and cut the heads a bit to get things to be a true 10.5:1. That was my point. A really good engine is more than the sum of it's parts (or reciepts). It also takes the care when making those parts work properly together.

As a quick test, take a cylinder pressure reading on a few holes, engine warmed up, all plugs out, and the throttle wired open.
 
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