2001 Pure Stock Drags

[Chevy454]

So, anyone else headed to Michigan this year? Pete & JJ are making the trip down from Canada, and I'm supposed to certify Wednesday, but what about everyone else? Marlin: is Neil gonna be there this year?

[Edited by Chevy454 (09-10-2001 at 07:42 AM).]

[YENKO DEUCE REGISTRY]

Rob;
I don't think Neal is going to the event this year. The 'certified' class is hard for some people to fit into their schedule.
M

[Chevy454]

I knew Neil wasn't signed up to certify, but thought he might have been planning on attending the regular activities. I also understand the scheduling problems with the certified stock tech...but, it's all for a good cause http://www.yenko.net/ubb/smilies/images/icons/wink.gif.

[COPO PETE]

What......Neil's not coming this year!!! Not even for the regular event????? Guess I'll have to down size my beer order! http://www.yenko.net/ubb/smilies/images/icons/laugh.gif http://www.yenko.net/ubb/smilies/images/icons/wink.gif See you Thursday Rob. With this certification thing, it's gonna be interesting!!!
Peter

[COPO PETE]

Well, I should likely wait for Rob to announce it but he's still on the road for another 9 hours. Rob had to race "the Stude" for the best two out of three. What a coincidence! It took three, but he got the job done. Car ran a couple of 13.0's. So close to the 12.99 he could taste it.He worked hard for it as he had a lot of problems, but never gave up. Passed his certification with flying colours. Congrats Rob, enjoyed spending the week-end with ya!
There was about 120 cars and he was in the top 16 fastest. Only 6 certified! 3 were DQ'd for not passing tech as they refused to be P&G'd. Dan and Bob put on a first rate show!
Oh ya...almost forgot... #1 qualifier was a Supercar! ;)
Peter

[Edited by COPO PETE (09-15-2001 at 08:38 PM).]

[Mr70]

Pete
Was Randy Miller there?
And if so what did he bring.

[Chevy454]

Pete:

No problem with posting the info! Drive was no big deal...only 790 miles from MMM to the house! Pulled in the drive way about 3am (I think?!) this morning...only took about 13 hours coming home (I must have hit all of the lights just right http://www.yenko.net/ubb/smilies/images/icons/wink.gif).

Like Pete said, it took 3 tries, but I FINALLY got the best of the Stude. I had him on the first run, but was in a coma on the line, and gave up .3+ off of the line. But, I sqeaked out the next 2, and the rest is history. Oddly enough, that is THE CAR that I was wanting to get paired up with! I knew we would be close, and I think Bob/Dan probably made it happen.

I had to settle for 13.0s@106, as I could never get the 108 back on the big end, but I noticed Gateway has a test-n-tune Wednesday night...may sneak up there and see what happens. BUT, I gotten swap in some new rocker studs before I do ANYTHING!

And for you guys that don't know, or haven't heard, Pete yanked his iron engine in favor of an aluminum peice! With just 2 weeks of time on the engine, Pete was in the 12.30s, and that thing has 11s (in PURE STOCK TRIM) written ALL OVER IT! Just a matter of time!

Thanks again, Pete, to you guys (JJ, Tim, Gary(?)) for letting this musclecar crazed redneck hang out with you well mannered Canadian Gents http://www.yenko.net/ubb/smilies/images/icons/wink.gif!

[Edited by Chevy454 (09-16-2001 at 08:32 AM).]

[COPO PETE]

Rob, glad to hear you made it home safe and sound! Hope any and all influences you may have picked up from us " Well Mannered Canadian Gents" will fade away shortly.
Randy Miller did not make an appearance this year.
Peter

[COPO]

Anymore more details about the event? What was the quickest car?

[COPO PETE]

No Ron, I had the white COPO car there. I just slipped a ZL-1 in for the race 2 weeks ago. I need more seat time, but managed a best of 12.34 @ 113 mph. Passed certification with flying colours as Rob did. My F70-14's arn't too excited about the switch! After tech was done and 3 cars weeded out for refuseing to p&g (were running about 119 mph) that left me #1 qualifier and 6 Pak Bob #2. In the end, I got caught up on my sleep at the light the first round, and then had premature excelleration the second round, but was still happy with #1 qualifier. http://www.yenko.net/ubb/smilies/images/icons/laugh.gif
Peter

[RN]

Pete does that mean you have 4 Copo cars as I have seen the yellow Chevelle , Orange Camaro and the Smallblock Nova and a white Camaro also that is running 12.30,s!! Thats awesome and really tuff on us Mopar guys but what a great collection!! Ron

[GMH454]

COPO PETE was that a real (old) ZL-1 you are running or will they let you run one of the NEW ZL-1s

[RN]

Sounds like everyone had a good time! Pete I take it you had the orange Camaro there and ran 12.30,s! Man thats hauling! And everyone is talking about the Studes but I see Rob took em out! Glad to see my Canadian friends had a good time and a safe trip! Ron

[COPO PETE]

Part #'s on the block do not matter, as long as the cubic inch is correct. The block I was using is the new GM block. What a work of art! The heads were a virgin set dated November 68 as was the intake, being untouched GM.
Peter

[Edited by COPO PETE (09-17-2001 at 05:26 AM).]

[MikeA]

Who/what came out on top? Was it a Buick?

Mike

[Avanti]

Just a quick note from one of the Studebaker fans. If Ted had to lose a shoot-out in his Studebaker, he could not have chosen a better car or a kinder group to lose to.
I wish I'd have been there, but from all I've heard, it's been a friendly competition with our the Studebakers gang, and I applaud you guys for that. On behalf of the Studebaker guys, we'll be back.

[Chevy454]

<BLOCKQUOTE><font size="1" face="">quote:</font><HR>Who/what came out on top? Was it a Buick?<HR></BLOCKQUOTE> http://www.yenko.net/ubb/smilies/images/icons/shocked.gif

No, it wasn't a Buick. The quickest qualifier was our very own "CopoPete", in his '69 COPO Camaro w/ZL-1 engine. I think his qualifying time was a 12.34, BUT he participated in the "Certified Stock" tear down, as did Bob Karakashian, the #2 qualifier in his '69.5 SuperBee w/440 6-pack. It's pretty cool that the top 2 qualifiers were "certified". Pete's engine only came in at 10.8:1 compression, and has a TON of room to improve...truly a package capable of 11 second ETs in Pure Stock trim. he's only had it going 2 weeks, so when he gets it dialed in, LOOK OUT!

Avanti:

Nice to see you stop by! I've gotta say, that the rivalry that has develop between our car and the Studes has been a lot of fun. The Stude people I met this past weekend were all VERY friendly, and showed great sportsmanship. In the back of my mind, I was hoping to get paired up with the PBW (that's "Plain Brown Wrapper" in Stude-talk), and that is how it worked out...also, from what I heard after the race, the crowd enjoyed the rivalry as well. Hope to see you guys next year!

[Mr70]

A Win for the Home Team!
Way to go Chevrolet guys.
For Manners and for Speed. http://www.yenko.net/ubb/smilies/burnout.gif

[JoeC]

Great job guys. I hope to see a report on the race in one the magazines or web sites. I wonder if they would allow a ZL1 motor to race a 69 Corvette body? Only two ZL1 Corvettes were produced so it wasn't allowed by NHRA in stock classes. Would that matter for the Pure Stock drags? A 1969 Corvette may be a little bit quicker and faster since it can use a wider tire then the Camaro (F70x15 Vs E70), has better front to rear weight balance, less restrictive exhaust system, and a little better aerodynamics. I was thinking about this because I saw a 1969 Corvette for sale with no engine or trans. Was an original 427 390hp car and even has an L88 hood on it. Would make a nice ZL1 Corvette clone. I better stop thinking about it.

[Chevy454]

Joe:

A ZL-1 Corvette is definitely legal, as it was factory produced. You aren't the only one thinking about that combo...

[JLerum]

Pete

How much HP and Torque did your ZL-1 put out? Great job at putting the Bowtie's on top.

Jim Lerum

[Chevy454]

Jim:

You are right on about the size of the ports, and the fact that the manifolds kill them! When I participated in the "Certified Stock" tear down this past week, I was the only Chevy car there on Wednesday, and I heard several people comment on how Chevrolet had "other intentions" when designing their hi-po BBC heads/ports. There was a 440-6, a 455 Stage 1, and Hemi also certifying that day, and they all commented on the seriousness (sp?) of the Chevy heads straight from the factory. BUT, the great equalizer is the crummy exhaust manifolds. That is one area the Hemi cars are definitely ahead of the game.

[JLerum]

I also think that the more compression that is run, the better the big ports function with the stock GM L-72, L-78, LS-6 cam. I think Pete's L-72 motor is a good example of why more compression is required. The lifters needed more lash to shorten the duration of the cam to fit the compression. I figure that the right dynamic compression should be 11.8 to 1. When you think of it, Pete's motor was running a lift of .480's after the lash was set to get the proper dynamic compression. Their are some good book out there that explain this very well. Pete I'm not picking on you as you have some great really quick rides, it's just that everyone is probably familiar with the really good article on your COPO dyno L-72 in MCR. Look forward to the ZL-1 dyno session. Which soon to be published issue will it be in?

Jim Lerum LS-6

PS: The 291 cast heads have 327cc ports which also hurt the low end port velocity for building torque. This right where we need to operate with the manifolds.

[Chevy454]

Jim:

Tell me more about lash vs. duration vs. compression, etc. This could be very useful...

[COPO PETE]

Jim, The car was weighed just before we pulled the motor and right after to get a accurate comparison, same fuel,etc etc. It weighed about 200 lbs to the ounce less. I run UAP NAPA 50/50 gas shocks on all four corners, as were not allowed to run race shocks. Valve lash for the street so far is .035 on both intake and exhaust. I shift at 7000 every gear and it goes through the end at 7200. Second gear is really loose! But a fun ride! http://www.yenko.net/ubb/smilies/images/icons/laugh.gif
Peter

[COPO PETE]

Jim, I understand what your saying and I agree 100% and it all goes against everything I've done. These GM cams are rediculous and silly. Without giving it that much valve lash I pretty much had no brakes. It could'nt produce enough vaccuum to operate them. Also from going from .024 to .035 I picked up 30 lbs of cranking pressure. Bottom line was I could'nt launch the car with no brakes. Et and mph were not effected at all with the change.
Peter

[JLerum]

Really neat Peter. Thanks for the info on the shocks. Again I look forward to the article on the motor. Did Tom Shaw come to do the article on the dynoed motor?

Jim

[COPO PETE]

465 hp threw the stock exhaust manifolds! Sorry the rest of the facts will be coming out shortly in MCR. They followed along for the day at the dyno. The real story is when we put the headers on!
http://www.yenko.net/ubb/smilies/images/icons/laugh.gif
Peter

[JLerum]

Cool Pete, glad to see that the magazine has come back once again for some Chevy power dyno sessons. It will hopefully reillistrate that the exhaust manifolds on the big blocks are really restrictive because of where the power is made. It's not the average big block that other manufactures designed with low RPM torque in mind. The intake port design says it all, RRRRRRR PPPPPPP MMMMMM's. How much weight did the car drop when the ZL-1 was installed? What type of shocks do you use?

[JLerum]

Peter:

I would think that you would beable to use as much of the exhust duration and lift as you wanted. If you can't it's because the exhaust maniflolds are allowing too much reversion. Use a balance pipe just on the other side of your torque converter housing. You can get them from Jeg's for $35.00 US. The car will run considerable better 2500rpm and up.

Jim

[JLerum]

Their you go guys, that tells you what .011 difference in valve lash will do to a really strong motor. I didn't think it would of increased the cranking pressure that much but it had to help the torque curve a bunch on the bottom end.

My hats off to you Pete for your fine tuning skills. How many inches of vacumm did the motor make at normal lash and your revised lash?

Jim

[Chevy454]

Now we are talking! Ok, Jim, so what is the "optimum" compression ratio for the standard L-71/L-72/L-78/LS-6 cam (.520/.520)?

Now, I understand why Pete did what he did with his ZL-1: he needed the lash for the brakes and to make up for the ZL-1's natural lack of a bottom end, both due to the big cam. BUT, I noticed in his L-72 dyno test that he ran a lot of lash as well, not as much as the ZL-1, but still well off of the factory's 24/28 mark.

Pete: did you get the email with the muffler/crossover tests?

[JLerum]

Pete, did you have to run the 780 vac sec as your ZL-1 carb? I'm sure it was tough getting the secondaries to open properly. If I remember right, the lowest spring tension is a 6.5" of vacuum. I would assume that when you saw 2" of vacuum you said oh sh!t.

Jim

[JLerum]

You need to give me some time on finding measurements for the cam as I can't find any information on when the valve actually closes. I have a cam that I'll take over to a buddies cam doctor(measures lobes and gives read outs)and see what it comes up with. If anyone out there has the measurement for an LS-6/L-72/L-78 cam put it on the site. It can not be a measurement at .020 or .050 as these don't qualify. It must be lift off the base circle.

Jim

[Edited by JLerum (09-21-2001 at 03:40 PM).]

[Chevy454]

<BLOCKQUOTE><font size="1" face="">quote:</font><HR>I would assume that when you saw 2" of vacuum you said oh sh!t.<HR></BLOCKQUOTE>

That would probably be MY reaction! Oh, and I am looking for the cam specs...

[JoeC]

I don't know what Pete is running but the ZL1 engine is a lot different then a L72.
The ZL1 engine was a L88 with an aluminum block. I have seen different spec sheets on them but according to one spec sheet It used a 850 Holley Double pumper, 12.1 compression, open divider intake manifold, a bigger cam, a transistor ignition system, and some other differences vs the L72.

[Chevy454]

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.

[COPO PETE]

Jim. ! 2 inches of vaccum at 1000rpm. With the inreased lash the motor went to 5 inches. It was interesting to note that we had the motor idling at 1000 rpm., increased the lash to .035 and with no other change the motor idled at 1700 rpm. It was nuts. Originally we thought we had a vaccuum leak and ran around the intake with a torch. No increase in rpm. Then we stuck the torch down the carb....no increase in rpm. Man that had us confused. We then stuck the torch tip in the pcv hose, and it picked up about 400 rpm.
Thanks for the tip, I am as we speak looking into a crossover pipe!
Peter

[JLerum]

Duration is the time that a valve opens to the time that a valve closes. On a cam card you get duration on the intake and the exhaust valve. These measurements are usually at certain standard lift values so that you can compare cams. The most important thing to know is when the intake valve closes (use a degree wheel) as this determines how much air/fuel mixture is caught in the cylinder. The later the valve closes the more static compression you need to help the dynamic compression of the motor. The term dynamic compression is the functional compression an engine understands when it is in motion (running). Because of the intake valve closing point being so important, you must build a motor so that the intake valve closes just right for the compression.

In the case of running in a class like Pure Stock Muscle Car Drags it is a little different. When running the (stock) cam you must pay attention to your compression. Design the motor so its compression ratio fits the cam by decking the block, ccing the combustion chambers, and or selecting head gasket thickness. The stock cam is defined by the rules so you must make the compression fit the cam. Do not think that more compression is always better because you can have too much compression for a cam. A good example would be the Buick Stage 1. The PSMDR allows you to blue print the motor to NHRA specs. The specs submitted to AMA would allow this motor to push almost 13.0 to 1 compression. The stock cam valve duration would keep you from using all this compression advantage and would be less than competitive.

To fine tuning a solid lifter cam motor you can change the intake valve closure 2 ways. The first would be on how you degree the cam during setup with the timing chain (advanced or retarded). This is the most effective way to move intake valve closure. When the cam is advanced the intake valve is closed sooner, increasing cylinder pressure effecting low-end torque. Retarded the cam closes the intake valve later and helps top end horsepower. Again this is because better high RPM cylinder filling.

The second would be adjusting lash. (IÃm finally answering your question) The looser the lash the more slack the camshaft lobe must take up before opening the valve. The lifter will have traveled farther up the lobe delaying the valve opening and closing the valve sooner on the back side of the camshaft lobe. In effect you have removed some duration. The other unfortunate result is you have lost lift. Extra slack in the valve train keeps the lobe from displacing its full lift to the valve. This is bad because we know that BB Chevys love lift.

If you are really able to sit on a dyno for an extra day, a lash loop should be tried. Isolate the intake valves and increase/decrease their lash in .004 increments to see how the engine responds. Then try the same thing with the exhaust. This will tell you how well youÃve chosen your compression or camshaft.

If you are running a rapid lift solid lifter camshaft you must be careful how you adjust your lash. Most of these rapid lift cams run .012 to .014 lash(very tight). You can not allow much more lash than the manufacturer has on the cam spec card. If you do the valve train will accelerate so fast that you will get broken valve train parts. Surprisingly you can run considerably less lash. Hope this is informative and gives some insight.



Jim Lerum




[Edited by JLerum (09-24-2001 at 07:11 AM).]

[Edited by JLerum (09-24-2001 at 07:12 AM).]

[Chevy454]

I don't think this will help you any more, but for those curious, here is the CAM CARD (http://dab7.cranecams.com/SpecCard/DisplayCatalogCard.asp?PN=969961&B1=Display+Card) for the L-71/L-72/L-78/LS-6 (http://www.cranecams.com/master/apps/chevy55.htm#5.Blueprint) . Also, here is a CAM CHART (http://www.martelbros.com/cgi-bin/store/ws400CS.cgi?store=COM&category=compcams2001/212.htm&cart_id=1010924092616420&page=compcams2001/compcams.htm) with some more info on this cam.

[Edited by Chevy454 (09-24-2001 at 08:56 AM).]

[Chevy454]

Jim:

OK, here is a link to Melling Cams, and at the bottom of the table, are the specs for cam #22396 (http://www.melling.com/production4.htm) . 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).]

[JLerum]

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).]

[Rowdy Rat]

<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

[COPO PETE]

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

[Chevy454]

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.

[bowtie3168]

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

[Rowdy Rat]

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

[Chevy454]

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 http://www.yenko.net/ubb/smilies/images/icons/frown.gif.

[COPO PETE]

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

[Rowdy Rat]

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

[COPO PETE]

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

[Chevy454]

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 http://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 http://www.yenko.net/ubb/smilies/images/icons/wink.gif...!

[COPO]

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).]

[Rowdy Rat]

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

[JLerum]

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