Re: 2001 Pure Stock Drags
 

Jim:

OK, here is a link to Melling Cams, and at the bottom of the table, are the specs for cam #22396 . This is the same cam as I linked specs to above. Using all of the links above, you should be able to get pretty close on the info you are looking for (I think).

[Edited by Chevy454 (09-24-2001 at 09:21 AM).]

Re: 2001 Pure Stock Drags
 

Here are some numbers for you on a cam that's representative or an LS-6 cam for a 454. This formula involves % cylinder volume vs crankshaft angles. If I can get a 3.76 stroke % cylinder volume vs crankshaft angle chart chart, I'll mke some numbers for the 427 and 396 motors. This is the compression mapping for the 454.

Intake valve closer/ Compression
IVC 68 degrees = 11.54cr
IVC 69 degrees = 11.64cr
IVC 70 degrees = 11.74cr
IVC 71 degrees = 11.86cr
IVC 72 degrees = 11.96cr
IVC 73 degrees = 12.06cr

I bet the LS-6 cam is around the IVC 70. Again, until I can get my LS-6 cam on the cam doctor I can't give you the exact intake valve closer. More info to come!!!!

Jim

[Edited by JLerum (09-24-2001 at 01:34 PM).]

Re: 2001 Pure Stock Drags
 

<BLOCKQUOTE><font size="1" face="">quote:</font><HR>There are some subtle differences between the ZL-1 and the L-88, but I can't remember off hand which carb Pete was running...I think it was the 850, but I wouldn't swear to it.<HR></BLOCKQUOTE>

Actually, there are major differences between a first design L-88 (1967-early 1969) and a ZL-1. The only difference between a second design L-88 and a ZL-1 that I'm aware of was the block. The second design L-88 engine began to appear (with a few exceptions) when Corvette production resumed after the April/May 1969 strike.

Outstanding job at the PSMCDR Rob... Very well done! I was certain that you'd be in the 12s, but it sounds like that you had some minor problems that didn't leave you much time for tuning. In any case, it was great to see you and Pete do so well.

Regards,

Stan Falenski

Re: 2001 Pure Stock Drags
 

Hi Stan, You seem like the person that would know. Is there any old articles on tuning either a L88 or the ZL-1 through stock exhaust manifolds? The only real test I read was the original ZL-1 test on the Blue car that Dick Harrell and Fred Gibb fooled with, in the Super Stock & Drag Illustrated mag. In it, prior to the first run they adjusted the valves at .032. The car had headers and better exhaust which does'nt do me much good.
Since these cars were meant to have headers, I would think the articles would be non-existant!
Are you saying that the second design L-88 and the ZL-1 had the same cam? I thought the ZL-1 cam was a hair wilder, all in lift.
Peter

Re: 2001 Pure Stock Drags
 

Pete:

All you did by making a pull with headers is tempt yourself! If you can get those manifolds to work like headers, then you are a magician!

Oh, I checked out our SS&DI collection, and all of our ZL-1/L-88 articles start off with a header swap, so no help there. The only thing I can find is Porterfiled's test in '94, where he tried to match the factories '69 dyno test. He ran with both manifolds and headers.

Re: 2001 Pure Stock Drags
 

Guys,
I do not want to tell you guys how to cheat because I think that cheating only leads to hollow meaningless victories. The stock eliminator crowd has been messing with questionable modifications for decades now. Are you all allowed to "Extrudehone" exhaust manifolds? Are you allowed to acid port? Maybe speaking with a "guru" like Jere Stahl might help.

Andrew

Re: 2001 Pure Stock Drags
 

Pete,

Congratulations on qualifying #1 at the PSMCDR (with a certified car no less)!

I am not aware of any other track or dynamometer tests of ZL-1s or second design L-88s with the factory exhaust system installed during that time period.

There was a 1995 dyno test of a ZL-1 engine that was published in Chevy High Performance that used the Camaro chambered exhaust, but I don't think there was anything done with the engine in stock configuration other than to establish a baseline for subsequent changes... They didn't spend a whole lot of time fine tuning the stock engine. I would imagine that you have seen that test already, but if not, let me know as I believe I saved the post for my files and can forward you a copy.

To the best of my knowledge, the second design L-88 is identical to the ZL-1 in every way with the exception of the block. The actual option description for RPO ZL-1 (Corvette) reads "aluminum cylinder case" and, in fact, you had to first order the L-88 to get it. There were definitely changes between the the first design cam and the second design ZL-1 cam... I'm going from memory, but it went from something like .540/.560 to .560/.600 (I can verify this and repost along with the GM duration figures as well if you like). The primary reason for this was to take advantage of the new open chamber cylinder heads. In fact, the engineers determined that the new heads and cam were worth about 40 horsepower even with the loss of a half point of compression.

By the way, are you planning on taking the ZL-1 to the PSMCDR next year or maybe leaning towards the LT-1 Nova?

Regards,

Stan

Re: 2001 Pure Stock Drags
 

Andrew:

Those types of mods are kind of frowned on by the majority of the Pure Stock racers, but they are out there. That's what was so great about Pete certifying...not only did he NOT build the engine to the extremes (per NHRA specs), but he chose not to even blueprint it to Chevrolet extremes (such as deck height, head cc's, etc.). Now, I'm sure there was a LOT of care put into the engine, but like JJ said, he could have done a LOT more. Just imagine what a blueprinted (just to GM specs!) ZL-1 would do! During the "Certified Stock", they had all of the runner specs, and checked everything out thoroughly. Believe me, they left no stone unturned!

Extrude honing is going on, but at about $400 for a set of exhaust manifolds, you had better be pretty serious. Dave Dudek tested a set on the dyno on his Hemi Challenger, and picked up 12hp (I think) over his non-honed exhausts. I think Brewer had everything that could be honed gone thru, and that engine definitely makes the power.

Stan:

The test you are referring to is, I believe, the test where Bill Porterfield and Batten Performance spun up a ZL-1 on the dyno, trying to simulate the GM tests. But, like you stated, there isn't much info there on the exhaust manifolds https://www.yenko.net/ubb/smilies/images/icons/frown.gif.

Re: 2001 Pure Stock Drags
 

Stan: Don't have that CHP issue handy. What month issue of 95 was it. If you remember, what hp fiqures did it make with manifolds.As far as next year....that's a long ways away. I still believe there is another tenth or three left in this ZL-1, so will likely play with it a little more. Original plans were to take the LT-1 Nova and try to be the first certified small block car in the 12's. If I do try and do that, Jimmy will be driving, so that still leaves me free to drive the ZL-1. But like I said, it's along ways away. Jimmy's car only ran some 12.6 to 12.8's. He ran three back to back 12.5's before we took it apart. He's not very happy with it, so it will likely be back. Thanks for your time!
Peter

Re: 2001 Pure Stock Drags
 

Rob & Pete,

Rob, that's the article... As mentioned, not a lot of info on the stock setup, but interesting all the same. The following information was taken from the article and posted a while back (by Joe perhaps?).

First off, the engine tested was supplied by Bill Porterfield, who at the time of the test, owned ZL-1s #1 and #3... Anyway, Bill supplied all the NOS parts, and tried to simulate the tests done in '68. So, here are the results:

TEST 1: All accessories, production exhaust manifolds and Camaro chambered exhaust system; 36 degrees of timing; rev limiter set at 6750. Result: 375.7hp@6500 and 358.5lb-ft@4500

TEST 2: Exhaust manifolds were replaced with 2 1/8 inch headers. Result: 418.9@6500 and 404.4lb-ft@4000

TEST 3: The air cleaner, alternator and A.I.R. pump were removed. Result: 447.2hp@6500 and 408.0lb-ft@4000

TEST 4: The Holley carb was rejetted for a richer mixture, and the timing was set at 39 degrees. Result: 444.2hp@6500 and 410.7lb-ft@4000

TEST 5: The chambered exhaust system was removed. Result: 523.6hp@6500 and 469.7lb-ft@5000

Pete, I'll see if I can locate the actual issue tonight when I hunt for the camshaft information.

Regards,

Stan

Re: 2001 Pure Stock Drags
 

See that Rob....you know, about chambered exhaust! Anyway thanks for your answer Andrew, it still brings a smile to my face,but it's not a option. And while I'm being a pain in the a$$, does anyone know anything about the story in High Performance Cars on the ZL-1? It's suppose to be the July 69 issue. And Stan, thanks for all your effort. I appreciate it!
Peter

Re: 2001 Pure Stock Drags
 

Yeah, yeah...if you Canadians wouldn't be so secretive about that ultra hi-tech exhaust technology you have been hiding for years, then maybe us "Show-Me boys" would be in the 12s https://www.yenko.net/ubb/smilies/images/icons/wink.gif!

Oh, on a sie note (Pete & JJ will LOVE this!): Remember when I checked my dwell before our match-ups on Saturday? Well, turns out I have been hooking up the dwell meter wrong! Who KNOWS what my dwell was at! Maybe Dave Greene is right...maybe I do have a lot to learn https://www.yenko.net/ubb/smilies/images/icons/wink.gif...!

Re: 2001 Pure Stock Drags
 

Stan, I had heard the chambered exhaust was restrictive, but never dreamed it would cost 80+ horsepower. Anyone would certainly think twice before using it.

[Edited by COPO (09-25-2001 at 07:38 PM).]

Re: 2001 Pure Stock Drags
 

Pete,

Not a problem at all... Glad to help out!

The camshaft information that I have is as follows:

#3925535 (First Design L-88)

VALVE LIFT

Intake - .540" (includes lash - .022")
Exhaust - .560" (includes lash - .024")

VALVE TIMING

Intake
Opens (BTC) 55

Closes (ABC) 102

Duration 337


Exhaust
Opens (BBC) 98

Closes (ATC) 68

Duration 340


#3959180 (Second Design L-88/ZL-1)

VALVE LIFT

Intake - .560" (includes lash - .024")
Exhaust - .600" (includes lash - .026")

VALVE TIMING

Intake
Opens (BTC) 62

Closes (ABC) 105

Duration 347


Exhaust
Opens (BBC) 106

Closes (ATC) 73

Duration 359


As noted above, the lift figures include valve lash and the opening and closing points are measured (I believe) .004" off the base circle.

Still working on that magazine article...

Regards,

Stan

Re: 2001 Pure Stock Drags
 

Well, I have returned with some results for an LS-6/L-72/L-78 cam. Tuesday I made the trip over to a friends business that has a cam doctor. This equipment is unique in that it will measure a cam at derived points selected by the operator. All measurements are made and printed out on a PC.

The cam that was used was purchased from GM in Dec of 1982. I think youÃll be surprised by the tolerances of this 3863143 cam. The printout from the cam doctor came out as such.

************************THE CAM DOCTORÃS ANALYSIS****************

Cylinder # 1 .050 check height
Part Number 3863143

Intake & Exhaust
Lobe center separation = 111.4 cam degrees
Valve Overlap = 13.9 crank degrees

Intake
Valve Opening = 8.6 œBTDC
Lobe Center = 111.4 œATDC
Valve Closer = 53.1 œABDC
Duration = 241.7 Crank Degrees
Max Cam Lift = .30516 In
Net Valve Lift = .500 In
Lobe Area = 27.36 In * DEG

Exhaust
Valve Opening = 57.5 ŒBBDC
Lobe Center = 111.4 ŒBTDC
Valve Closer = 5.3 ŒATDC
Duration = 242.8 Crank Degrees
Max Cam Lift = .32126 In
Net Valve Lift = .524 In
Lobe Area = 27.6 In * DEG



Notes: Intake .024 hot lash/ Exhaust .028 hot lash
Net Valve Lift=(Max Cam Lift x 1.72)- hot lash
Rocker Arm ratio= 1.72




I thought it was very interesting that a cam that is suppose to have a lobe center separation of 114 degrees cam out to 111.4. This car would idle a little rougher than a cam with 114 degrees. If you noticed that the camÃs exhaust lobe is a little taller than itÃs suppose to be. In a perfect world with a perfect cam the hot lash it should come out to .492. net valve lift. This imperfect grind on the exhaust side should be beneficial to some performance. I have the numbers of this cam at .020 which I'll post in the near future.


Jim