shmoky

I have been told that the toughest decision to make on an engine rebuild is the camshaft choice. I have been on this for a while now and just can’t seem to make a decision. I NEED HELP.

I have a 68 coupe with a M21 and 3:70 gears. The motor I am rebuilding is a LS5 454. I will be using the car for a LOT of hi-way miles and only at the track a couple of times a year. Although I think we all like the SOTP torque pull around town. My max rpm might reach 6000 but likely a LOT closer to 5000 or 5500. Our premium gas here is 91 octane. I want to use a hydraulic roller cam and am not willing to change the iron heads at this time.

Here are the motor #’s

LS5 454 BBC
bored .030 over. Stock stroke, and stock rod length.
Forged pistons
Cylinder heads… Chev… 3964290 101cc chamber oval closed. (shaved 12 thous)
Intake Valve: 2.19 undercut
Exhaust Valve 1.72 undercut
Rocker ratio 1.72 ratio
Compression: 10.3:1
Carb: Holley Street Avenger 770
Aluminum Edelbrock Performer RPM Intake manifold (# 7161 12105)
Exhaust: 2 ½” Headman headers

I can’t decide which cam to get but here is a couple I am looking at right now.

Comp Cams Magnum Retro-fit 280HR
Adv. Dur 280in./280ex
@.050” 224in./224ex.
lift .566in./.566ex.
LSA 110 (would a 112 LSA give me a flatter torque curve (but longer) and help with the idle?

And the Extreme Energy Retro-fit XR276HR
Adv. Dur. 276in./282ex.
@.050” 224in./230ex.
Lift .510in./.510ex.
LSA 110 (again would a 112 LSA give me a flatter torque curve (but longer) and help with the idle?

I hope I am making myself clear in my concerns and that some of you engine guru’s can help me out. TIA

shmoky

Little Mouse

112 LSA will give a little wider power band smoother idle.
You might consider this cam
part # CRN-139011, lifters part # CRN-13532-16
power range 1600-5600
3000-3400 cruise rpm
9.5 to 11.0 comp. ratio advised
.050 duration 226/234
advertised duration 288/296
valve lift .587/.610
LSA 112

www.summitracing.com

TheSkunkWorks

I like the 112 LSA idea for the range of cams you're looking at, especially if you go with as much as 290'ish advertised duration. I'm assuming that's a PowerMax Little Mouse suggested. Good grind. One could even make an argument for 114 with that one. Of the two Comp's you mentioned, I'd take the Magnum 280HR over the other, but at that 112. My $.02...

shmoky

Thanx guys. That's the kind of info I want to see. Little Mouse that is a good looking cam. I like the operating range. It's a little bigger lift than what I have been looking at but should be okay.

Anyone else want to kick in an opinion?

shmoky

DRIVESHAFT

One thing to think about. If you buy a Comp hydraulic roller, and dont pay extra for a billet shaft, you will get a cast iron cam. Comp is the only company I know of that does that on a roller. There have been an above average number of failures with the cast cam.
I like Cranes hydraulic rollers as well. I would probably go up one size above what Little Mouse reccomended to a CRN-139021.
Here is a link to it at Summit http://store.summitracing.com/partde...1&autoview=sku .

rebc3

where are you gonna shift this thing? if your gonna shift at 7000 then the larger cam is the choice. if you shifting closer to street sanity rpm;s the smaller cam would actually make more power for you. its a tuff choice.

DRIVESHAFT

With a hydraulic roller and oval port heads, peak power will be done by 6000 rpm, even with the larger cam that I recommended.

63mako

Good move posting here! I like the specs on that crane cam Little Mouse recommended too! It will help them factory heads breath. Good duration numbers but the higher the lift the more spring pressure required, the more valvetrain wear you have. There is always a trade off and that is probably the highest lift I would consider. The billet core with a cast gear is good advice for the slight price increase. Failures are more common on the flat tappet cams with fast ramp rates or rollers with high lift and heavy spring pressures. Check with your cam manufacturer about a recommended fuel pump pushrod also. Different manufacturers will want you to use different pushrods (bronze tip lightweight). Also if you buy a matched kit which I would recommend with all valvetrain components, make sure they will allow you to return the pushrods for a different length. They rarely fit correctly once the decking and head resurfacing is done and you go to setup the valvetrain. Don't open the pushrod package!!! Get a length checker and see what you need, check against the required lenght and go from there. Good luck and remember your intended use when getting advice. don't fall into the "but this makes more peak HP" trap. Make sure you are around 7.5 DCR with good quench with your choice.

TheSkunkWorks

Good advice there. BTW, that 7.5 DCR is an iron head recommendation. It can be pushed up to 8 and even a little more with alum.

Little Mouse

No its a new Z-cam hydraulic roller, for some reason in my catalog on
hydraulic rollers for big blocks Crane jumps pretty far up in duration
after this cam to far what rpm range he is interested in.
Getting exhaust out is big for a big block the first cam is a single pattern
the other has a tiny amount of lift for a roller cam, thats why I suggested
a different cam. Not worried about 610 lift on valve springs on a big block
they have a higher installed height nice big diameter springs, duration on springs
holding the the valves open a little longer can also effect spring life not
just lift, but these cams are very mild on duration.
What ever cam he decides on I would use a dual pattern for sure on a big
block and no way in hell would I except 510 lift on any modern big block cam
in a hydraulic roller. I ran around for a lot of miles with a 560/580 lift
cam 310/320 adv. duration with 87 degrees overlap, with just factory springs.
no spring problems.

63mako

.510 lift on a roller cam in a big block is pretty short. Somewhat defeats the $ spent on the Roller cam upgrade. I suggested if he decides on the XR 276HR go with 1.8 rockers. over .600 lift might be close on piston to valve clearance depending on a lot of variables. Always check!

Little Mouse

I really don't know the 580 lift cleared but that cam was holding the valves open for a far longer period of time then the short duration
he is interested in so 610 exhaust lift may work out ok with short duration.
what are the specs on the XR 276 HR ??

shmoky

LittleMouse the specs on the XR276HR are:
Adv. Dur. 276int./282ex. @.050 224int./230ex lift w/1.7 rocker .510/.510 LSA 110 operating range 1900-5600rpm

shmoky

Little Mouse

I would say the duration works but even if you go to the expense
of 1.8 rockers, new pushrods and probably taller valve covers to
make it all work you still don't end up with very good lift for a roller cam.
look for something in a dual pattern with the short duration on the
intake side you want but allows better lift with 1.7 ratio
rockers. Maybe I'm being picky an LS5 cam has very low lift very short
duration, but if your going to spend $800.00 or so for a nice hydraulic
roller I think you should try to get the most out of your investment.

73, Dark Blue 454

With 10.3:1, iron heads, and 224 @ .50, I think she'll knock and ping. I'd go wth at least 230 @ .50 and if you're running headers, I like a single pattern cam. Here's an explanation:

http://www.camaros.net/forums/showth...rn+cam+cabbage

Little Mouse

He must be running around right now with an LS5 cam it has very
low duration.

TheSkunkWorks

In addition to past BB experiences, after countless hours of EA Pro sims I've decided to go dual pattern on my 496 even with my "oversized" Hookers. Seems BBC's just respond well to one step (and sometimes two steps) more exhaust cam than a given intake profile.

BTW, It'll have in the .650" range w/1.7 rockers, and I'm not going to loose a bit of sleep worried about it. Compared to the solid mushroom grinds I played with back in the day, I don't consider it radical at all for a solid roller street cam.

63mako

You will need .650 lift with that many cubes. Probably got .100 longer valves too which help the springs live longer Shmoky, What ever cam you pick, before you plop your $ down, check your DCR. It is critical with iron heads you don't go over 7.5 and have .040 quench or like 73 Dark Blue 454 says it will knock and ping I went with a dual pattern on mine also (SBC). The dyno Sim #s were better.

TheSkunkWorks

It's hard to over-emphasize the importance of quench...

Yep, .100" long Ferrea 6000 EV8's, with titanium retainers.

Jason Staley

I've been using a .544" lift, 300 adv dur (250 @ .050" lift) cam on a BB Olds with 10:1 cast iron heads for quite some time with no pinging. I mainly have it for drag racing, but its still a street car. My idle is a bit rough due to the 108 lobe seperation, but it still has a huge amount of torque just off idle. I love my SBC, but you can't beat cubes for all out power.