2001 Pure Stock Drags

[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?

[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]

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.