Rumor has it, the LS7 is using a larger base circle diameter than the LS1/LS6
engine.

Any truth to this? Does anyone have specs on this bad boy?

I've seen the following:

"Based on C5R racing experience, the LS7’s cam has an all-new profile that provides .591-inch lift (15 mm) on both the intake and exhaust valves."

No sign of valve timing, or any other data in my search.

 

I think I read the duration will be 211/230 @ .050

LSA is MIA...

 

CAM, VALVETRAIN AND MORE
All of that flow capacity would be sitting idle if the cam and valvetrain were not designed to take advantage of it. To that end, the valve lift has been increased from 0.525-inch to a lofty 0.591-inch, again breaking new ground for a production powerplant. Providing the valve action for that lift is a camshaft measuring 211 degrees of duration on the intake, and 230 on the exhaust. The camshaft is aided in achieving valve lift by rockers with a ratio of 1.8:1; up from the 1.7:1 ratio of GM's other current small-blocks. The relatively short duration and dramatically high lift help the LS7 achieve very high power levels while timing valve events for an acceptable level of refinement and emissions.


http://popularhotrodding.com/tech/0504phr_ls7/

Best article on the LS7 I've seen so far.

She's a stout one.... looks like an aluminum 427 small block with a set of sb2.2's on it doesn't it?

Small cam and looots of airflow.... seems to work nicely. Now let's see what she'll do at ~7k rpm.

WRT lsa... I'm thinking 113º or better.

-Mindgame

 

Yeah that LSA is high if you look at the normal negative overlap numbers on a OEM cam.....

Still a 55mm Journal so the base circle is smaller now since there is more lift at the lobe as well as the valve. (.328 vs .324 on the last ZO6)

Bret

 

LS7 Hp/L is just a tad higher than the LS6, even at the new 505 hp rating. I guess Corning built them some freer flowing cats.

With 7000 rpm available, 0-60 can be a first gear only run. That translates into good "magazine" numbers, which was intentional, I'm sure. It won't take Heinrichy driving to get the good number!

LS7 valves are just a bit larger than the early C5R heads. 2.20 vs 2.125 and 1.61 vs 1.60.

So, Bret, do you think you could find another hundred hp in there with a cam and some valvetrain parts?

 

You know, I think the valvetrain on the LS7 is about as good as it's gonna get. Probably going to have to look at other area with the LS7 but one things for sure... a little more rpm is plenty feasible.

-Mindgame

 

I was thinking about more lift, duration and springs. Yeah, the individual parts are nice. I like the offset intake 1.8 intake rockers on a production engine.

 

55 mm journals used in the C5 Z06 as well? That puts the rumor to rest then.

Amazing how "tiny" the duration specs appear to be in relation to the
power being made (500 HP @ ~ 6800 RPM?)

Post the dyno graphs if you have them!

 

I'm reading ~6000 rpm there. The summary at the bottom is showing 6200 FWIW.

Just recently saw a gen1 small block, 415 ci (I was told 381... 2nd hand), do over 650hp 6800rpm with a set of sb2.2 heads and a ~230 @.050 solid roller. Heads for this one flow right at 390 cfm with what some would consider to be ginormous ports (~265cc). Still don't have all the details on this one as it belongs to a friend of a friend but it just goes to show what airflow can do.

-Mindgame

 

Sounds pretty streetable!

 

Mindgame, that is a very detailed write-up.

Is this quite possibly the first time a production motor is paying attention to
exhaust flow for performance?

Photo:
http://popularhotrodding.com/tech/0504phr_ls7_18_z.jpg

"Providing the exhaust scavenging are hydro-formed steel tubular exhaust headers. The individual header tubes meet at a unique quad-outlet collector flange at the end of the header outlet. From there, exhaust is routed by a smoothly-tapered extension into a "wide-mouth" catalytic converter. The design greatly reduces the engine's backpressure."

 

Smokey's setup wasn't as pretty but that looks like something he built in the early 70's late 60's. Anyone remember that setup?

I don't think it's the 1st time exhaust flow was paid homage. GM did it with the LT4 Camaro and then got away from the ram's head log for the LS1. Think they're just finding better ways to build better designs economically. Hydroforming has opened a whole new can of worms at GM and I'm sure the engineers are sitting round' thinking... "What else can I design for hydroform?".

Technology.

-Mindgame

 

I guess it depends on what you mean by production. In 1963 (yeah, 42 years ago), Pontiac rolled Super Duty Catalinas and Tempests off the production line. Each of the 421 Super Duty solid lifter dual quad engines was hand built by two UAW guys in a small area of the engine plant. One guy did the short block, another did the top end. The built 1 or 2 engines a day. The current method is on a larger scale for the LS7 and the 440 hp 4.4L supercharged Northstar, but there is a precedent in GM.

The 421 cube Catalina (big car) had cast iron (or cast aluminum) 4>2>1 headers (exhaust manifolds) with a bolton collector which had a 3 inch outlet covered with a plate held on by two easy to reach bolts. When the plate was on the exhaust went out thru a small muffler system. When it was off the exhaust dumped just after the headers...err manifolds. BTW, the iron ones go back to 1960.

The Tempests had the same engine, but fabricated sheet metal exhaust manifolds. They were 4>1 which were stamped in four pieces, outers and inners, and gas welded together by another UAW guy. They also made a few sets of the big car 4>2>1 manifolds this way.

You can see all of this in Pete McCarthy's book Pontiac Musclecar Performance 1955-1979. I was about Zero's age then and was lucky enough to see all this stuff happening at Pontiac. Being in the right place at the right time is handy.

Not meaning to just tell "war stories", but, IMO, the wheel isn't being reinvented, it's just a lot more sophisticated. Hydroforming is a neat process.


Are you thinking of the 8 into 1 Smokey tried? I thought I had a pic of it, but I couldn't find it.

 

Yea, Chevy and Ford both made a 'special effort' with certain engines in the 60s as well.
Although, not to the extent of 4-2-1 as Pontiac did.

:slapping forehead: Wait a minute. Didn't the early Zs ('68-'69) have headers 'in the trunk', when the optional 'off road' package was ordered? I believe so.

 

ehh you are asking for it with a first gear that high. launching it is going to be both hard on the driver, clock and drivetrain