Oldguard 7

I plan on replacing my cam and am wondering if this is a good match with the following components installed when I rebuilt the engine a few years ago.

Engine: 350 +.060
Piston head type/material: Flat with slot, forged (TRW#L2417F L-82 piston)
Deck: stock height
Compression ratio: (10.0:1+)
Edelbrock 2101 intake idle-5500rpm (also have Stealth Manifold: idle-6800rpm)
Edelbrock RPM heads (64cc)
Edelbrock 600cfm carb (thinking of ditching for a new in box Mighty Demon 750)
Do not recall cam specs of current cam, it was a Lunati cam.
Stock convertor.

After all of that: Here are the specs of the two cams im looking at:
RPM range: 1,800-5200rpm
Adv Dur: 274/274, Dur @.050: 218/218
Valve Lift: 450/450
LSA: 106
Description: Largest cam for stock convertor 9:1 and higher cr, lopey idle, excellent midrange power.

Cam#2
RPM Range: 1,500-5,000rpm
Adv Dur: 272/272, Dur@.050 lift: 216/216
Valve Lift: 454/454
LSA: 110
Description: Lopey-Rough idle, excellent midrange power 9:1 and higher cr, stock convertor.
Phew, comments please.

cardo0

For a single pattern cam u need a low restriction exhaust system. Headers plus large BB 2&1/2" pipes. What do you have?
Ok stock converter but what rear end ratio?

BTW 108 LSA is optimum for 350" with 2.02" valves - Isky mega cams are on 108 but are all single pattern cams.

Good luck,
cardo0

Oldguard 7

Headers, chambered exhaust, 3.55 gears.

73, Dark Blue 454

I prefer single pattern cams. On the street, with good heads and exhaust, they simply make more power. More here:

http://www.camaros.net/forums/showth...e+dual+pattern

Also, like many, I'm done with flat tappet cams. Go roller. A few more pesos, but in return you'll get more power, never have to worry about ever-changing oil recipes (zinc), a quieter engine, and peace of mind that the chances of wiping a lobe are minimal.

How about one of these:

http://www.summitracing.com/parts/CCA-12-420-8/

http://www.summitracing.com/parts/CCA-12-430-8/

The second selection may be a little much for your stall but if you're planning a future converter upgrade,..

Good luck with your decision.

gkull

This is only true if you are talking about billet or hardened roller cams.

Because I had a Comp Cams XE 286 SR or some number like that and it was made out of mush metal. I was using sub 200# closed with lite weight valve train.

The Money Pit

Cam selection of course has a huge deal to do with your intended use.....With a stock converter,low rise dual plane intake,....a lawn mower cam would do OK.

I ran a Comp HE 268 in my 355 for 120,000 miles or so. It was a flat tappet,(OMG!!!) 218@.050 454/454 110lc cam. Idled like a Caddy, pulled to 5500 or so, got 17 mpg with my 3.70 gears,...and lead foot.

Your Cam 2 Option looks pretty close. If I were redoing my old 355, I may even have gone a little smaller, like the old Edelbrock Performer cam (204/214@.050) I've run that one in many other engines and liked it alot.

73, Dark Blue 454

If you're set on a flat-tappet cam (we'll all send you some Kharma) the cams listed so far are pretty small.

The old Chevy "151" cam (GM part number 3863151), used on 350 HP 327's was a single pattern cam that spec'd at 222 @ .050 and .447" lift.

The "962" cam (GM part number 3896962) used on early L-82 engines spec'd at 222 @ .050 (both E/I) with .450" lift on the intake and .460" on the exhaust.

Both have 114 lobe centerlines so they'll idle nicely and work well with your stall and your 3.55's.

Both are still available at your Chevy counter.

And both, with tried and true ramps (lobes) that are less aggressive that today's performance cams, would stand a better chance or survival.

glackore

Oldguard7,

Your intended purpose is the big question to answer. It appears that you are interested in mild performance and keeping your stock convertor. All engine components noted so far look good - although I would question the 750cfm carb choice - 600 thru 650cfm would be better suited. If it was me I would go for option #1 based on your choices. Also, the Performer cam from Edelbrock is a great street camshaft, mimicking the 327/350hp cam from the late 60's. You're bound to get many, many opinions on the forum! Good luck!

63mako

Here are the specs on the 962 cam

This gives you an intake closing point of 90 ABDC. I can tell you a couple things. You will be able to run 87 octane @ 10 to 1 compression with either choice. Your DCR will be under 7 to 1 with either one, 6.2 to 1 with the 962. You will probably never have to worry about wiping a lobe if you break it in properly and your .575 lift springs are weak enough to match it correctly. It will probably cost you 40 - 50 hp across the entire RPM range compared to a modern ramp profile
Dual pattern cams are designed to help a weak exhaust side due to head flow or exhaust system restriction. If your intake exhaust ratio is around 80% and your running unrestricted exhaust a single pattern will be fine. Notice the more modern grind of the two does have higher lift on the exhaust. Back in the day we used to run 1.6 rockers on the exhaust side to bump power. See other thread.

73, Dark Blue 454

Pete,..your specs square with what I posted,..or are you making another point?

73, Dark Blue 454

Exactly what "modern" cam did you have in mind that would make 40-50 more HP across the entire RPM range vs. the GM "962" cam?,..which BTW, has more duration (222 @ .050) than any cam suggested so far.

gkull

My 79 L-82 was really a dog. Even though the cam is rated at 222/222 the ramps are very wimpy so you don't get much cylinder filling. My first mod was Crane 272 cam, no emissions, headers and true dual exhausts. It started to give me a kick in the pants. My second mod was heads and intake. That is when the raised compression required a the cam change to the Crane 278. That was my solid 12.70 vette for many years and with little items got down to 12.30's

63mako

This cam:
http://www.compcams.com/Company/CC/c...x?csid=97&sb=2
The advertised duration is 270 vs the 312 advertised duration of the 962 cam. This gives you an intake closing point of 63 ABDC instead of 90 ABDC. What does this do? It changes the DCR to 8.1 to 1 instead of 6.2 to 1. (I did the math). Intake duration @ .050 is 226. It is on a 111 LSA. It is higher lift, It has an operating range of 1800 to 6000 RPM so it is compatable with his stock convertor. It is a split duration which will help with the reletively weak intake/exhaust ratio of the RPM heads and the chambered exhaust. I would bet 40 to 50 HP average across the operating range of the cam mainly due to the DCR increase. This cam does have steep ramps. It will require 93 octane fuel. It will need careful attention to spring pressures, valvetrain geometry, proper break in procedures, good moly based assembly lube, break in additive and I would use a 1400+ ZDDP oil.

63mako

And I too respectfully disagree with some of the above.

First: I would always compare advertised duration in any cam choice. This, LSA, ground in advance and install advance/retard determine the actual closing point of the intake valve. Advertised duration is the amount of degrees the valve is actualy open. The two inputs to determine DCR once the compression ratio is set is rod length and actual intake closing point. The difference between the IVCP of the two cams is 28 degrees. The intake closing point is found by dividing the advertised duration by 2, adding in the LSA, subtracting any ground in advance and subtracting 180 from that number assuming the install is straight up. The GM cam has no ground in advance. The comp cam has 4. You do the math.

Second: The cam with the earlier intake closing point will always have higher DCR. The intake closing point is the determining factor. Duration @ .050 has no bearing on DCR in this instance. The cam I listed has a DCR of 8.1 to 1. in this build. The 962 cam has a 6.2 to 1 DCR.

Third: The operating Range of the cam I linked is 1800 - 6000 RPM. Factory Corvette convertors are a higher stall than the stock convertor on other chevys, 1800 to 2000 I believe. This cams operating range is within the stock convertors range. A higher stall convertor will usually help et's even with a smaller cam especially with a higher rear gear but with his 3.55 gears this will work fine.

Fourth: RPM heads are good heads. They flow a lot more than stock, epecially on the intake side. The choice of a dual pattern vs a single pattern is best determined by the intake/exhaust flow ratio of the head and exhaust restriction. The chambered exhaust is either 2" or 2 1/2". Both rely on narrowed areas throughout the pipe to baffle the exhaust. These narrowed areas are down to 2" or less on the 2 1/2" system. This is restriction. The flow is only as much as the narrowest point in the ststem. These narrowed areas also cause turbulence further restricting flow.

Edit: I read the camaro forums link. Many of the posters are running big blocks, quite possibly bigger, freer flowing exhaust, maybe better I/E ratois. Many other factors also come into play. A single pattern cam on a 108 lsa will have the same overlap as a dual pattern cam on a 112 lsa if the intake specs and lobe designs are identical and the exhaust advertsed duration is 8 degrees more with the same lobe design.

Rest of the post: I also suggested a roller cam. I always do. As far as wiped lobes is concerned this is what I said about that in my last post:
"This cam does have steep ramps. It will require 93 octane fuel. It will need careful attention to spring pressures, valvetrain geometry, proper break in procedures, good moly based assembly lube, break in additive and I would use a 1400+ ZDDP oil." The 962 cam will be more forgiving due to the lazy ramps but they come at the price of serious power loss. He could run regular gas and probably use an SM rated oil with it and have no problems.
As for the power difference the L82 puts out 225 HP stock with your cam choice. His heads will help that a little but that 962 cam and the much longer overlap will not make good use of the potential of his heads. Where do you think his power will be with his build specs and an increace in DCR from 6.2 to 1 to 8.1 to 1 with increased lift and duration @ .050?

Again, simple difference of opinion. No disrespect intended.

73, Dark Blue 454

I can't go with much of what you said.

First, we'll agree to disagree on the value of "advertised duration" numbers when comparing similar cams and different manufacturers.

Second, I've no idea how how you get a DCR of 6.2 with the 962 cam. Please better describe your calculation/formula, or the tool used to input the data.

To help, here's the spec sheet from Crane for their "Blueprint 151" cam (same as the "962" with slightly less lift; .447/.447" vs. .450/.460"):

http://www.cranecams.com/product/car...detail&p=23892

Your suggested cam's intake closes at 63 degrees ABDC. The 962 closes at 41 ABDC. Your cam has an intake duration of 226 @ .050. The 962 has 222 @ .050. Your cam has a 111 LSA; the 962 has a 114. Again, how did you arrive at your findings that your cam has a (much) higher DCR?

Thirdly, we'll agree to disagree on what's better in this case; single or dual pattern. Isky tends to agree with me:

From here:

http://www.iskycams.com/index.php

and here:

http://www.iskycams.com/techtips.php#2003

...is this: "(extended exhaust duration is) bleeding off of low to mid range torque, which is always what happens when Exh. Duration is lengthened."

and,..

"...most experienced drivers (circle racers, 99% of which run SB engines) are those who are most likely to run a single pattern (equal on intake and exhaust duration) cam. Why? Because such cams always, I repeat, always make more torque!"

Fourth, your statement that the 962 cam was only good for 225 HP in an L-82 is disingenuous. The low HP numbers for L-82's in the late 70's was hardly the fault of the cam. This same cam, the "151", which actually had slightly less lift than the 962 (same duration), made 350 HP in a 327 (the L-79) in the mid-60's. Do you have any doubts it could make 375-400 HP in a 355 with headers and much better heads than the "Fuelie" heads of the 327?

Fifth, of the two choices, you have to agree the 962, with it's more reasonable ramps, will have a much greater chance of survival vs. the X4270H.

Lastly, you still sticking to your claim that in this case, the X4270H cam will make 40-50 more HP "across the entire RPM range" vs the 962?

Good discussion,..

Oldguard 7

Interesting learning quite a bit. I knew the cam I installed long ago that is presently in the car was a Lunati, but I did not remember what Launti or the specs (misplaced cam card) It iis a Lunati "Hi-Efficency" cam with the following specs. Lift: 420/442, Adv Duration: 270/280, @.050 lift: 204/214, RPM Range 900-4800rpm, LSA: 112. It is a weak cam in my opinion and I'm changing it. I want a 500 lift (on both intake and exhaust) cam with 230+duration that will have a lopey-rough idle.
I'm going with the Voodoo (dual pattern) Cam
#60104
Lift:504/525
Adv Dur: 276/284 @.050 lift: 233/241
RPM range: 2200-6800 LSA/ICL 110/106
I'm aware this cam will be a dog at the bottom for the time being. Will replace Performer manifold with my stealth manifold and the edel afb carb with my mighty demon 750cfm carb. I will upgrade to a high stall convertor and get a trans cooler at a later date. Seat pressure is adaquate and the springs with these heads are compatable.

63mako

That intake closing point on the Crane 151 is @ .050 lift not .000 or .004. You need the actual intake valve closing point. This is the difference, I don't know how to explain the difference advertised duration will affect DCR other than the lengthy and detailed explanation I gave in my last post, I explained in detail how to accuratly figure intake closing point and advertised duration, LSA, ground in advance and advance/retard of the install are the correct information you need to figure that. Maybe if I give you actual figures and calculations it will help explain the need to know your advertised duration when selecting a cam and figuring DCR.

Go here. This calculator is accurate If, and only if you have the correct intake valve closing point. It is not correct if you just add 15 to the closing point @ .050 lift because cam lobe profiles vary so greatly from one grind and manufacturer to another.
Open this in a new window on your browser so you can click back to this page to input numbers,

http://kb-silvolite.com/calc.php?action=comp

Plug in these numbers
head cc 64
piston head volume 4
gasket thickness .039
gasket bore 4.125
cylinder bore 4.060
deck clearance .025
stroke 3.48

Hit calculate

This gives you compression which with these specs is 10.023 to 1
Now we have actual compression which matches Oldguard 7's posted compression.

Now we need to figure DCR.
Plug in these numbersin the next section.
Rod length 5.7

This leaves one blank, actual intake valve closing point.
To figure this you take the advertised duration and divide by 2.
Then you add the LSA to this number.
Then you subtract out the ground in advance.
Then you subtract 180
We will assume the cam we are installing is installed straight up.
This gives you an actual intake valve closing point to use in the DCR calculator

Comp cam 270 ad dur divide by 2 is 135.
135 + 111 lsa = 246
246 -4 degrees ground in advance =242
242 - 180 = 62
The closing point in the cam card is listed at 63
close enough

Plug 62 into the last number in the DCR calculator.
Hit calculate
Final DCR figures 8.177 to 1
Using 63 instead gives you 8.117 to 1
Either one is a good match for an aluminum head engine to get best power and be able to run 93 octane

Now we will figure the last number on the DCR calculator using the 962 cam.

GM 962 advertised duration is 312 divide by 2 is 156.
156 + 114 LSA is 270
270 - 0 ground in advance = 270
270 - 180 = 90
90 is the intake closing point of the 962 cam
now plug 90 in as the last number in the DCR calculator.
Nothing else changes.
The end result is 6.217 to 1.

So, YES I am still claiming the Comp will outperform the 962 cam by 40 to 50 HP average from 1800 to 6000 RPM based on the drastic DCR difference.

The 151 cam you keep bringing back up made 350 HP. It was also in a shorter stroke engine that had 11 to 1 compression with iron heads. You need a lot of overlap to run an 11 to 1 iron head motor and a lot of RPM to make power with a 3.25 stroke. I figured that engine just out of curiosity. The 151 cam has an intake closing point of 80. @ 11 to 1 this calculates to be 7.584 to 1. That is a decent DCR for an iron head motor with big quench to run pump fuel.

63mako

Good choice! Big lift and duration and dual pattern will work great with your heads and exhaust. This cam gets you an intake closing point of 64.

DCR 8.058 to 1. With a higher stall convertor and an intake and carb upgrade it will run like a scalded dog.

Your old cam had a closing point of 63. DCR 8.117 to 1. The poor lift and duration numbers were totally killing the advantage of having good aluminum heads.

Radical ramps! Be carefull. Good Break in, High Moly assembly lube, Good geometry, Springs match (check pressures), High ZDDP oil. I would look at the Royal Purple expensive stuff or Brad Penn You need lots of ZDDP.

Oldguard 7

Wish I had the money to buy a roller cam, but cannot afford one right now. Nice not to be able to drive and go (no a break in period). More expensive as for parts should the cam or rollers lifters go kaput....it can happen. As for flat tappets the cam and lifters can go kaput as well, and more often based on what I have read. Oh well....at least once I complete the swap and upgrade, I will have a car that will be fun to drive.

cardo0

Go one step smaller/shorter for the cam. Try Lunati #60103 and use 1.6 rockers on the intake vlvs only. This should be tame enough for your car as is.

Just my 2 cents and good luck,
cardo0