ronterry

This thread is carried over from the carb board. My problem kind of took over a thread that was deal with carbs, so I started a new one over here.

The story so far: I installed what I believed was a Performer RPM cam three years ago. The car only has 300-400 miles on it to date.
Did I degree the cam when I installed it? NO
Am I a believer in cam degreeing now? YES

I want to thank F-BIRD'88 for challenging that my 15"-16" of vacuum at idle dosn't seen right for a RPM Cam, and that I might verify that I have the right cam.
I did buy the cam from Checker Auto, in an open box state.
The cam that I pulled seems to look like a ****ing crate motor cam.

-----------------------

Your not going to believe this, but I took my dial caliper to it. (1.250 base - 1.525 lobe)
.275/.275 !!!
So that's .4125 at the valve! Now I know why it fell flat on it's face above 5400 RPM's. It also idled to nice, and of course all that wonderful vacuum at idle.

Don't anybody bother with trying to get a Performer RPM cam. There back ordered across the board. Something to do with a buy out. Your looking at least 3 weeks or longer.
So after many hours of crunching numbers I got a Comp XE284.
Anything bigger than that, the RPM heads can't breath right or something.
I used (3) engine sims : Desktop Dyno 2000, Virtual Engine Dyno 2000, & Performance trends Engine analyzer 3.0.

Anybody have any opinions on the Compcam XE284?
.507/.510 lift
240/246 Duration .050
BTC 14 ABC 46
BBC 57 ATC 09
Centerline 106 ATDC/114 BTDC
Lobe Separation 110
---------------------------
Chevy 350 .040 over - 10/20Ni - 2 bolt studed with windage tray.
Performer RPM 64cc Heads.
Performer RPM Intake
Edelbrock 750.
Crane Roller Rocker 1.5
Flattop forged pistons.
Felpro 1010 head gaskets.
MSD Everything.


Ron

Jer82Z28

damn, thats some sad lift on your supposed performer cam

I woulda thought those edelbrocks would like a bit more lift than that .510 is really a whole heck of a lot..

according to flow numbers the normal performer heads still flow really well at .600


what kinda power does your computer dynos say you will be making?

ronterry

Oh I think someone swapped it out, probably an employee at Checker?

I don't know about the flow numbers, but every dyno says to much, and it dumps. It's like there's a lift limit to those heads.

Here's a Desktop Dyno of the RPM cam.


RPM Head Flow


Diffs with the XE284 & RPM Cam.


Diffs with the XE294 & RPM Cam. The limit ?


Ron

Polecat

I ahve the XE284 in my 383. With 4.11 gears and a 3000 stall, pulls really, really hard after 2200. Now if you have less stall and gears, get the XE274. Still will pull nicely to 6200 rpms.

Fast3rdGen

this is off topic.......but how do you post the images from desktop dyno/drag2000 on here?????

RB83L69

Yup, sounds like some scumbag at the store probably paid for a stock replacement part, and swapped the parts in the box, to get the RPM cam for less.

I would take any prediction that the RPM cam will outpower anything but a 929 or 151 cam with a grain (boulder?) of salt. That is one weak cam.

Keep in mind when evealuating head flow vs. lift that the flow rarely goes down as lift increases. It may stop going up, but it doesn't fall off. Meanwhile, the valve spends far more time at less lift than the peak; so to get the valves to spend more time at, say, .300" instead of .200" where there is a HUGE flow difference, the peak will be higher. The only other way is to have faster ramps on the cam, which is only possible up to a point.

IMHO the XE294 is too much cam for that intake and those heads. It's into single-plane territory. The XE284 should be a very good match. Stall at 42, shift at 58, go through the traps at 65.

ronterry

Boy, can you guys remember the days of picking a cam by guessing? or bigger is better? We knew there was side affects as you went up the scale, but the 305 or what ever cam at the top of the scale, yea that one - it was FASTEST

HAHA with age, comes wisdom.


Thanks guys - glad to see the 284 is a good cam.


'Fast3rdGen' Just press the Prt Scr button, and paste it into paint. Then mod the image from there. When you press the Prt Scr button it takes a picture of the screen & everything on it, and saves it to the clipboard. You can paste into any paint program.

BTW: I just recieved a Summit Degreeing Kit in the mail today I learned my leason! I won't install a cam without one.

Ron

Mark W. Winning

I have an RPM cam I now use to stop my car from rolling down the driveway. I was not a big fan of its design. My Comp pulls a better 1/4 time and idles far better than the Edelbrock ever did. May be just my combo though...

F-BIRD'88

ronterry: Glad to see you're getting every thing sorted out.

The comp 284XE cam you have planned will work quite nicely.

A friend has this cam in his 383 rpm head 80's camaro
with a 3800 converter and 4.56's. It runs 12.3's with a victor jr
and ran a 12.6 with the performer rpm intake.

If you want a "performer rpm cam" you don't have to use an Edelbrock brand., The generic copies are the same cam.
You can get the exact grind from Crane Cams Blazer
Wolverine Blue racer
Summit racing
Federal Mogul
Mellings and many others.

Specs are 234/244@.050 and.488"/.510" 112 LSA.

I would degree this cam in and install the intake lobe at 107.

The comp 284XE cam is a more modern intense design that should make better power but needs good valve springs.
Go for it. I think you'll see a marked improvement in top end horsepower now.!!!

ronterry

Yeaaa, I'm sure I'll see a marked improvment over a .420 lift crate motor cam.
Still that little bugger could move on the low end

I did notice that Summit had a clone of the RPM cam, but I've already got the 284 seated, and ready to degree on Thursday

I was seriously thinking Victor Jr, but thought most of it would be outside of my usefull power band. hmmm I'll have to crunch some numbers.

Whats funny or maybe not, but the old cam had a nick on the last lobe (right at the crest). It looks to be caused by stress, and I was carefull in the removal. So hmmm.

I'm not using it as a wheel stop, but I did hang it on the peg board as an ornament - right next to the copper head gaskets

Ron

Gator_Z28

What happens if you don't degree the cam when installing one?

ronterry

That's easy! In my case I ASSUMED I had installed a Performer RPM cam, and instead installed a completely different cam.

If you look at the card that comes with a cam - when you degree a cam your verifying those numbers with the cam in your engine.

Lets call it an insurance policy. It's like plastic gauging your crank, your just checking the cam timing for accuracy.

BTW: I purchased a timing pointers when I got the new cam the other day, and right out of the box it's 1.5 degrees off. The degree wheel give you the exact TDC. This is the very reason I purchased a Tavia adjustable pointer

Ron

Gator_Z28

Thanks for answering that. I was just wandering because next weekend i'm putting in my Edelbrock Torker plus cam that came with the intake and carb. It has a lift at .488"/.488" and at .050 it is 232/234

F-BIRD'88

Try the 284 XE cam with the rpm intake then if you get a chance
try it with a Vic jr. Either way you'll want a stout torque converter
and some gear to take advantage of the raised power band.

Degreeing cams on install. ......Hummmm.
I wounce installed a new Crane solid cam in my 454 BB.
Bought a new timing chain and top gear too.

Figured since the bottom crank gear was in good shape I'd save work and money and just get the chain and top gear.

Well finished the install and drove the car and it seems to have
a whole lot more bottom end power than you'd expect from the the specs and not a lot of top end.
After degreeing the cam to check the timing , turns out I installed it 9 deg more than the card called for for a total of 14 deg advance. Guess what , timing gears are checked and the timing marks are put on in sets. I assumed they were all the same. Not.... Now I always check the timing points when doing a cam change. And change timing gears in pairs ...

ronterry

Ha Ha, I had that happen to me also. Had a stock crank gear, and an aftermarket cam gear.

Yea, I'm going to keep the RPM Intake on there for now, maybe even get it on a real dyno I keep you posted...
---------------------------


'Gator' I bought a Summit degree kit for 89 bucks.
Good luck trying to find a dial gauge I tried everywhere, so I finally broke down and bought the kit.

FYI...
I fashioned my own pointer, and mounted the wheel in my balancer instead of the crank. The Summit kit tells you to mount the wheel to the crank, but its impossible to rotate the crank in the opposite direction with out loosening up the crank bolt and throwing TDC off. It's much more stable using the balancer & crank bolt on the wheel.

Oh, and don’t sit there scratching your head for an hour wondering why your centerline is 114 degrees, only to figure out that your on the exhaust, and not the intake. Note to self #1 intake is the second lifter! ****

Ron

Gator_Z28

thanks for that tip ronterry! I would probably spend 2hrs trying to figure that.

ronterry

Here, I dropped a picture just in case you decide your going to go through degreeing your cam. It's kinda fun

BTW: My cam checked out...

Take the cam & crank gears to heart, cause a lot of stock gears are 5 degree retarded. I've got a Edelbrock 'true' set that works great, and is straight up.

Ron

Mark W. Winning

I hate "built in" parts. Oh, we build in 5 degree less HP for your safety, but did not tell you.

Just give us what we want to buy. A quality part that you do not have to re-invent the wheel to install. My Crane setup in my truck was the first cam that I ever saw come up dead on with a degree wheel.

RB83L69

most people don't know that about stock timing sets... the 929 cam was used as far back as the early 60s in 283s and ran pretty good, but starting in 71, they changed the timing set (retarded it) but left the cam the same, to get some built-in EGR for emissions reasons... moral of the story is, NEVER use a GM timing set or any part of it.

You can make an otherwise box-stock motor run noticeably different, sometimes dramatically different depending on gearing and such, just by changing the timing set. An aftermarket one will vastly improve low-end torque.

Kingtal0n

My RPM cam came out a year ago, and I just threw it away like a week ago. I've tried a blazer cam, and a comp cam, and found I liked the RPM cam better. I added a blower, and found out the RPM cam is ALSO a great BLOWER cam! On lunati's website, their "Street blower cam" is an exact replica of a performer rpm cam. thats what I bought, so now I've got a great N/A cam and a great blower cam in my engine... lol I didnt know it at the time I bought it but found out later after comparing the specs with my original rpm cam... Just fired it up 3 days ago, 11" at idle on the manifold, and 18" at the carb because of the blower spinning.

I find the "intensity" of the cam a little too much however, with a 303~ advertised and a 234 @ .050, thats alot for even a flat tappet cam. Comp cams 234 @ .050 has only 282 advertised, thus much quicker opening and closing ramps. technically this should mean more vacuum, better idle, and more power... but you cant convice me. I had a crane 224/234 blazer and it made no power for me, anywhere in the rpm range. I went to a comp 280 magnum, had decent top end, but didnt like the high stall and bad gas mileage that follwed. I went to the lunati blower grind, which happened to be the ol' rpm cam in disguise, and now with the blower attached my new LOW 2400 stall should be no challenge for my 500 RWTQ at 2000 rpms.... Oh yeah and im getting 18 MPG thanks to my Adjust-a-jet and my self-drilled manifold ref. power valves. g0d but my carb is so rigged....

ronterry

Well, I broke in the cam. Held it between 2200-3000 for 25 minutes. The only mishap was that I put to much oil in the power steering, and about 15 minutes in to it - it started draining out.
Dang, I was more worried about the from pan seal, and this was the high light of the burn in. Well - changing oil thats about 240 degrees is also a little memorable. hoooootttt.

I'm usualy good at dialing in the timing after a distributor removal, well not today. I had 40+ degrees in at 1000rpms.
The little bugger ran good even with crap loads of advance.
Probably the advantage to being at 6300 feet, and using 91 octane I have about 38 total, and 17 idle now.

At least now I have about 5"- 7" @ 800rpm (vac bonces around pretty good until I rise it to 1000rpms? I'll see if I can dial it in better tomarrow ...blame the Pocono race...).

So 'F-BIRD'88' where the hell ***** we --- Oh yea, I think it needs to be jetted back up now , and a little loser step up springs...

Ron

Jer82Z28

think you lost a bit of vaccum with your new cam?

let us know how she runs when you get 'er out and about

ronterry

Hey 'Jer82Z28', Yea there is definitely a reduction in vacuum (who needs power brakes at idle anywho?)

Yea, I'm getting the same fluctuation in vacuum at idle, but the bottom, and top ends are tight. It does smoothen out at about 9-10" at 1000rpms, so hmmm - might be normal.
I'll play with the carb tomorrow, and see how she feels - Torque wise.


Ron

Harley83

I know this subject hasnt been touched in a little while.. But to all the negative comments on the RPM compared to a Comp Cam. While the RPM might make lower horsepower the lobe seperation makes it idle nicely but I wouldnt suggest it if you are pulling over 6000 rpms because of the lobe seperation the RPM falls on its face after 5500 rpms. But the whole idea behind their Power Package idea was to make it for streetable motors. Compared to the Comp Cams 274XE the idle is so much smoother. By the way Im not in anyway affilated with Edelbrock Products lol

Kingtal0n

<b>While the RPM might make lower horsepower the lobe seperation makes it idle nicely but I wouldnt suggest it if you are pulling over 6000 rpms because of the lobe seperation the RPM falls on its face after 5500 rpms. </b>

Im sorry but im going to disagree. My RPM cam pulls nicelly up to 6500 Rpms. Yes I have the package including heads and intake.

<b>But the whole idea behind their Power Package idea was to make it for streetable motors. </b>

I know thats what they want you to think but I disagree again.
My RPM cam idles like a pro-stocker and shakes the fenders of the cars <b>next to me</b> Its also horrable low end and doesnt pull very well until about 3000 rpms. This is mainly due to my sorry gearing (2.77) but I think you see my point, unless your a little beyond a bolt-on setup the RPM package will not make usable street power until you begin to mess with your drivetrain.

<b>Compared to the Comp Cams 274XE the idle is so much smoother. </b>

*sigh* i disagree. The performer RPM has an advertised duration of about 303/313 as opposed to 274. Which one is going to be smoother? I know .050-.050 plays the biggest role but think about it. I had a 274 AND a 280 magnum comp. The performer RPM is by far more radical than Either of those in my opinion. although the 280 was a bit on the rough side...

<b>By the way Im not in anyway affilated with Edelbrock Products lol </b>

I can tell. NO offense dude, these are my opinions and im not trying to be annoying to you, Im just stating my personal experience with the performer RPM package to help inform people out there.
Now with some 3.73's my car will rock into the mid 12's thanks to edelbrock. The key is to have everything match....

ronterry

Well, since than I've added a Victor Jr. & port matched them to 1205's. The Vacuum is rock solid now, but the days of just firing it up in less than a 1/2 second of starter are over (Not building a street machine anyhow)
The Victor does pull harder than the Performer RPM, but the launches are sluggish. (That give-take thingy).
I also finished up a hell job, of rebuilding the read end. New bearings, new Posi, new 3.42 gears, new reinforced cover, completely new drum setup, and added some Jegs adjustable LCA's (Hell, the suspension is next on my list anywise) for good measure.

Ron

Harley83

"The performer RPM has an advertised duration of about 303/313 as opposed to 274. Which one is going to be smoother? "

Yeah but the Comp Cams XE-274 has a lower duration and lift and a lower lobe separation at 110 degrees while the RPM is a 112 degrees of lobe separation with a beefier duration and lift. So really you are losing horsepower ,vaccum, and idle in a sense if you really think about it. The only advantage on the lower lobe separation is it pulls slightly quick through the RPMS. And advertised duration is usually worthless it is the duration at .050 that matters more. Im not trying to argue with ya or anything dude but you shouldnt pick a bone if you didn't think about those little tidbits. LOL Sorry bro no offense meant to ya but just my thoughts.

dimented24x7

iTrader: (2)

Hmmm... is that a fact? Never knew they retarded the stock timing sets. The GMGOODWRENCH LM1 i have has that same grind (according to the GM specs) and it makes a whole whopping 190 HP. Tempting to change the timing set just to see what would happen.

Kingtal0n

<b>Yeah but the Comp Cams XE-274</b>
Lets examine the Performer RPM cam. Lets use Comp Cams recommendations as a guidline for whats good, and whats not.

First, The Lift. On the street, and on the track, extra lift ALWAYS helps. Up to the maximum lift of the springs, and the maximum flow capability of the heads, yadaa yadaa, lift is very important to any high performance engine. according to comp cams, having the more lift on the street gives you increased low end torque, and increased high end horsepower. its a win/win situation, from a power point of view.

Next, Duration. Saddly, not everyone feels the same way about duration. As I said in my earlier post:
<b>Its also horrable low end and doesnt pull very well until about 3000 rpms.</b> and:
<b>The key is to have everything match....</b>
My point of view from the "horrable low end" is simply because of my gearing. If i Had, say, 3.73's... I would be saying somthing like "the performer RPM cam made my car into a rocket on the low end" but, as i stated, the low end is crap due to my gear. the reason? duration, and intensity.
According to comp cams, having the least amount of cam INTENSITY is the main reason a roller cam ALWAYS out-performs a tappet cam with the same .050/.050 duration specs. Intensity is just the advertised duration, (303/313) minus the .050-.050 duration (234/234) and we get: (69/69)
Lets compare that to, well, your 274XE comp cam:
(274/286) advertised, (230/236) .050-.050 duration. the intensity would be (44/50)
According to comp, the 274XE cam is a much better camshaft due to less intensity.

That is, if they both had the same exact .050-.050 but one had intensity (69/69) and the other (44/50) then the one with (44/50) would pull more vacuum, better idle quality, and no loss in top end horsepower.

What you said:
<b>So really you are losing horsepower ,vaccum, and idle in a sense if you really think about it</b>
is COMPLETELLY CORRECT in this respect, since both cams .050-.050 are almost identical and the advertised is way off....
BUT your REASONS:
<b> Yeah but the Comp Cams XE-274 has a lower duration and lift and a lower lobe separation at 110 degrees while the RPM is a 112 degrees of lobe separation with a beefier duration and lift</b> And:
<b>The only advantage on the lower lobe separation is it pulls slightly quick through the RPMS. And advertised duration is usually worthless it is the duration at .050 that matters more. </b>
Are slightly misplaced. You listed that "More Lift" was a reason the performer RPM cam was worse.
You also said that "And advertised duration is usually worthless it is the duration at .050 that matters more. "
which is half true. As examined above, advertised duration is one of the most important things. important to have LESS of, but still very important and impacting to cam design and application.
and you said "The only advantage on the lower lobe separation is it pulls slightly quick through the RPMS." I assume the "lower lope sep" would be the 112 even though 110 is numerically lower, but since you said "the only advantage" i assume you actually mean the performer cam since you are bashing it (and rightly so). Lets examine LCA for a moment.
Lobe separation angle is imporant. no doubt. how wide? good question. Typically, a cam with a WIDER (numerically HIGHER) LCA will pull more vacuum than the exact cam with a closer LCA. but why why why? its not duration we are playing with... or maybe it is...
Here, Read all about it:
http://www.nightrider.com/biketech/camlsatable.htm

so as you can see I agree that the 274 would be a better "all around horsepower" camshaft, but for MY APPLICATION (that is, Using a blower) the performer RPM cam actually makes more power, vacuum, idle quality, etc... simply because I added a power adder.

jcb999

Its usually done with a reindexed crank gear.

F-BIRD'88

Kingtal0n:

You're making a common mistake of confusing
"advertized duration" with "running duration" or seat duration
the two are not the same.

Different manufacturers assign different lift reference points
to measure or qualify their "advertized duration"
for their *own marketing purposes*.
Unless the advertized duration is measured at the same
lifter height you cannot compare the two different cams.

If you actually measured the lift curves of the two actual
cams ( on a Cam Doctor) you would fine they are probabily very simular in design.
All cam manufactures are simularly limited in the design of their
opening and closing ramps on the cams of a particular motor.

That RPM cam is a copy of a generic (but sucsessfull) design that is produced and sold by numerous different manufacturers.
You can find numberous different "advertized durations"
for the exact same camshaft grind, sold under different names.

Comp Cams, while a good cam company is an even better cam marketing company. They have you fooled into thinking they have reinvented the wheel with their "extreme energy" series cams.
By stating that they have a shorter advertized duration relative to .050" duration than others.
The truth is they just measure it at a higher point on the lobe
than other companies.

There is no free lunch.
Cam design is a compromise of many factors which you are ignoring.
by pushing the limits of cam ramp acceleration they are increasing
stress on the valvetrain and increasing wear. It is always a trade off. Thats not to say that Comps Extreme energy series of cams cannot be used to good effect successfully, BUT...
Let the motor tell you what it wants for cam duration, lift, overlap
ramp acceleration and lobe separation. Leave the numbers game to the "Armchair Dyno Experts" and the camshaft design to the manufacturers. More, or more intense is not always better
or the right choice for your motor.

Neither of these two cams would be a good choice for a car with 2.73 gears and or a low stall converter.
Which one is better is really cutting hairs. They both need a 2800+converter some good heads and intake, headers
and some higher rear gears.

Harley83

Yea I consider advertised useless because basically its a tool to market the cam. I personally have had better luck with other cams that are like Summit..laugh as cheap as they look they are they are the best way to stuff a big cam in a street car because of the high lobe separation you have better idle quality and more vaccum. Ill be the first to say Comp Cams has really nice cam designs but most of my luck comes with nice aluminum heads and a big duration $79 cam kit.

Kingtal0n

<b>They have you fooled into thinking they have reinvented the wheel with their "extreme energy" series cams. </b>

I dont like Extreme energy cams. Never said I did...

<b>That RPM cam is a copy of a generic (but sucsessfull) design that is produced and sold by numerous different manufacturers.
You can find numberous different "advertized durations"
for the exact same camshaft grind, sold under different names.
</b>

!!! My camshaft is NOT a performer RPM cam... its a Lunati Blower Cam. It just so happens, as you say, to have the same exact Lift/Duration figures as the performer rpm. Are they then, the same exact thing? Unlikelly. Though they both pull the same vacuum, idle the same, and produce similar numbers, the limitations imposed (as YOU SAID) by the opening and closing ramps vary accoring to the manufacturer (as you said) and I totally agree.

<b>By stating that they have a shorter advertized duration relative to .050" duration than others.
The truth is they just measure it at a higher point on the lobe
than other companies. </b>

Do they? in the catalog it explains "advertised" as "seat to seat" which would be the same thing... Im not mistaking them. Accoring to comp, their Seat to Seat (.000-.000 lift duraiton) is the same as their Advertised duration.

<b>Neither of these two cams would be a good choice for a car with 2.73 gears and or a low stall converter.
</b>

I totally agree. With a simple gear change I will drop over a full second on my 1/4 time.

<b> F-BIRD'88 </b> I follow what your saying and totally agree with everything you said, except that comp cams (advertised) vs (seat to seat) varys. according to comp, like i said, they are identical.
also, lets get one thing straight. I mislike comp cams. I ran one for less than 2 months and that was it for me. So far my best luck has been with lunati and Summit.
<b>but most of my luck comes with nice aluminum heads and a big duration $79 cam kit.</b>
Just like Harley83 pointed out. As long as you dont get a bum grind, and the cam in the box is what it says on the box, you should be Ok.