Thread: Camshaft Selection

Tweet

I'm looking for ideas on camshaft selection. I've decided on the following;
LS2 aluminum block for weight savings (ordered from my local Chebby dealer)
I'm looking at a Lunati rotating assembly (crank, rods, pistons) with a 4" stroke (402 CI) and compression should 9.0 or 9.1
I'm probably going to get a set of AFR CNC ported heads with 2.05" intakes and 1.60" exhaust valves and the larger 76cc chambers.
Magnuson Magnacharger. These usually spin to 5 PSI on a stock 6.0L. With the added breathing, the included pulley will most likely only give 2 PSI. Will adjust the pulley to gain back the other 3 PSI
My goal is a very streetable engine that I can jump on now and then. A roots-style supercharger is usually only going to work (and make good power) up to 6000-6250 RPM. This is OK because I'm more concerned with off the line torque than ringing out every last little upper end horsepower.

The car should weigh between 3000 and 3200 lbs, as whatever I save off the rolling chassis will be gained back with insulation and all kinds of power gizmos (windows, locks, cruise, seats, stereo equipment, etc.). The target is 3100.

The rear end will be a 3.73 with a double-overdrive T-56.

Now, this is what I'm looking at. It may seem tame, but it's the largest lift GM has put in a Gen III V-8 (yes, a factory cam). It's the LS6 cam and it's also used in the LS2. The specs are;

Lift: 0.555/0.551 (I/E)
Duration (at .050): 204/218
Lobe Centerline: 117.5

A couple of GMPP cams run a longer duration, but the lift is less. The centerline is also smaller (110 and 112) which would be nice for a lumpy idle.

This cam, to me, appears to offer what I'm seeking; a decent idle, a good vacuum signal to operate the brakes, and enough duration to bleed off excess pressure to avoid detonation on pump gas.

I'm not interested in mechanical cams, and I think a .600 lift isn't necessary to get the power numbers I'm looking for (550 HP). I figuire if I need to add a little lift over a chosen cam I can switch from 1.7 ratio rockers to 1.75.

So based on the above, thoughts? Suggestions?

Tom, BDS recommends LDA of 110 degrees on pump gas.....
http://www.blowerdriveservice.com/recommend.php

Pick the grind number from this chart that best describes your combination and intended purpose...
http://www.blowerdriveservice.com/camspecs.php

Then use this table to see the specs they recommend....
http://www.blowerdriveservice.com/bcamspecs.php

i think i have a ls6 cam and the stock gm lifters and gm rockers and pushrods all this cam off aZo6 vett went to TD rocker arms and soild comp cam the stock gm cam WORKS dam good and I can not see why it would not work i would try to keep it to 9to1

Originally posted by techinspector1
Tom, BDS recommends LDA of 110 degrees on pump gas.....
http://www.blowerdriveservice.com/recommend.php

Pick the grind number from this chart that best describes your combination and intended purpose...
http://www.blowerdriveservice.com/camspecs.php

Then use this table to see the specs they recommend....
http://www.blowerdriveservice.com/bcamspecs.php

I guess I should have mentioned that this is an EFI engine with a factory roller cam. BDS only has one hydralic roller cam and it's set up looks like it's for a standard small block (non-LS1, LS2, etc.)

Thanks though.

Tom, somehow I get the feeling that we're not connecting. If you look at their recommendations for a mild, blown, efi motor, you'll see that the recommendation is for a 4600 grind. Going to the other chart, no matter what motor the 4600 grind is listed for, it's still a 4600 grind, with specs of around.....
lift 0.485-0.495
duration 224-234 @ 0.050"
LDA 110 degrees

The point is that no matter who grinds the cam, these specs will work better for you than any other grind whether it's a flat tappet, roller, whatever.

They're also recommending a converter that will stall around 2,200-2,500 rpm's. This is for the automatic crowd, I see that you're going to use a T56.

The newer Gen III V-8's run with a lot more lift than the older SBC's. The lift suggested is approximately what GM uses in their trucks. Now what they are suggesting for duration is interesting, as is the lobe centerline.

But this is why I'm asking. You did notice that the suggestion for a roller cam was considerably different than the other cams listed?

i think with efi with may get a way with more lsa??and watch out. the lifter get out for the bores and the oil hole gets way up to the top of the bore on the 600 lift stuff

Yeah, I'm trying to keep some sensability in what I use. There's been a suggestion of running a little more duration (Crane has a cam with 224*/228* duration, with lift of .551 on each). So that's there.

GM sells a hot cam with 219*/228* and .525 lift with an L/C of 112*. I can't see going much past .570 on lift if it's a good fit for the engine.

yes i would try to keep it around 570 .that crane looks good to me

new generation small blocks and old small blocks are different all the way around.....can't use the same specs in comparasin to camshaft selection because of the differences in the motors them selves....sounds to me you are on the right track in sticking with GM grinds......your motor will scream with the factory camshaft.....going up to .570 lift wouldnt harm anything on your combo.....but again comparing the old small block to the new generation is not going to work....hope this helps and when you get the chance post some track times........you should have an awesome 60' time......

Originally posted by Swifster
I'm looking for ideas on camshaft selection. I've decided on the following;
LS2 aluminum block for weight savings (ordered from my local Chebby dealer)
I'm looking at a Lunati rotating assembly (crank, rods, pistons) with a 4" stroke (402 CI) and compression should 9.0 or 9.1
I'm probably going to get a set of AFR CNC ported heads with 2.05" intakes and 1.60" exhaust valves and the larger 76cc chambers.
Magnuson Magnacharger. These usually spin to 5 PSI on a stock 6.0L. With the added breathing, the included pulley will most likely only give 2 PSI. Will adjust the pulley to gain back the other 3 PSI
My goal is a very streetable engine that I can jump on now and then. A roots-style supercharger is usually only going to work (and make good power) up to 6000-6250 RPM. This is OK because I'm more concerned with off the line torque than ringing out every last little upper end horsepower.

The car should weigh between 3000 and 3200 lbs, as whatever I save off the rolling chassis will be gained back with insulation and all kinds of power gizmos (windows, locks, cruise, seats, stereo equipment, etc.). The target is 3100.

The rear end will be a 3.73 with a double-overdrive T-56.

Now, this is what I'm looking at. It may seem tame, but it's the largest lift GM has put in a Gen III V-8 (yes, a factory cam). It's the LS6 cam and it's also used in the LS2. The specs are;

Lift: 0.555/0.551 (I/E)
Duration (at .050): 204/218
Lobe Centerline: 117.5

A couple of GMPP cams run a longer duration, but the lift is less. The centerline is also smaller (110 and 112) which would be nice for a lumpy idle.

This cam, to me, appears to offer what I'm seeking; a decent idle, a good vacuum signal to operate the brakes, and enough duration to bleed off excess pressure to avoid detonation on pump gas.

I'm not interested in mechanical cams, and I think a .600 lift isn't necessary to get the power numbers I'm looking for (550 HP). I figuire if I need to add a little lift over a chosen cam I can switch from 1.7 ratio rockers to 1.75.

So based on the above, thoughts? Suggestions?

LIKE EVERYONE IS SAYING.I WOULD TRY FOR MORE DURATION AT.050.I DID NOT FOLLOW WHERE YOU TRYING TO RUN 3 OR 5 PSI?I WOULD ALSO TRY TO RUN THR BOOST UP THERE A FEW MORE LBS.OTHER THAN THAT IT SOUNDS LIKE A VERY GOOD PROJECT.

Originally posted by 81 cabellero
new generation small blocks and old small blocks are different all the way around.....can't use the same specs in comparasin to camshaft selection because of the differences in the motors them selves....sounds to me you are on the right track in sticking with GM grinds......your motor will scream with the factory camshaft.....going up to .570 lift wouldnt harm anything on your combo.....but again comparing the old small block to the new generation is not going to work....hope this helps and when you get the chance post some track times........you should have an awesome 60' time......

If you'll examine cam specs from grinder to grinder, you'll find that many times they use the same specs for a Chevy, Pontiac, Olds, etc., etc., so your statement about old to new is full of hot air.

I also would pull back on the lift, you don't need as much lift on a blown motor as you might on a naturally aspirated one. Not only will you kill springs quicker, but it's more of a hassle to establish valve to piston clearance, retainer to guide clearance, etc.

Originally posted by techinspector1
If you'll examine cam specs from grinder to grinder, you'll find that many times they use the same specs for a Chevy, Pontiac, Olds, etc., etc., so your statement about old to new is full of hot air.

I also would pull back on the lift, you don't need as much lift on a blown motor as you might on a naturally aspirated one. Not only will you kill springs quicker, but it's more of a hassle to establish valve to piston clearance, retainer to guide clearance, etc.

In most cases you would be correct. The new Gen III and Gen IV small blocks are completely different animals. The love lift. A stock '02-'04 Covette Z06 and '05 C6 (with LS2) use the very cam spected above and it idles smooth. A starting upgrade cam on the truck engines are .510-.515 lift. I can't stress how different these engines are.

The springs if I use the GM cam would be the LS6/LS2 springs (GM recommendation). Another reason for liking this cam is that there would be no piston interference. The pistons are dished to lower compression (and these are a positive deck engine), and the chambers on truck heads (6.0L LQ9, 74cc)are typically 10cc larger than the Corvette heads (5.7L LS6/6.0L LS2, 64cc). AFR offers closed and open (76cc) chambered heads just as GM does.

I plan on using roller tip rockers, and with the difference in components, I'm going to have to adjust push rod length anyways. I consider engine set up to be part of building a custom engine.

Crane sells a cam with .555 lift on both sides, with durations of .224 and .228. The lobe center is 114*.

Other suggestions?

"Other suggestions?"

Yeah, have it ground on 110* LDA like BDS says.

"The love lift."

Yeah, but they're unblown.

Richard, there is a reason why no one (other than GM) makes an aftermarket camshaft with less than .500" lift. This isn't my grand dad's small block Chevy. Seriously, check out Crane, Comp Cams and GMPP. On these newer engines, too much lift starts at .580".

The BDS site is looking at Gen I and Gen II SBC's and this engine has zero in common with those engines and they don't even address this engine family. It's not a relevant site to this discussion.