Intake CL for ZL-1 cam

[TomN]

I am trying to find what would be the best intake CL to install a ZL-1 cam at with the idea of pure stock racing with stock manifolds. Has anybody been there done that or know of someone who has and what results they got.
I know the 396/375 cars/cams like 6 degrees retard, but what about the L-88/ZL-1?
Thanks

[Peter426]

I can't answer your question specifically but do know when you advance a camshaft you increase bottom end and lose some top end and vice versa when you retard a camshaft. Always keep in mind (and don't forget to check) valve-to-piston clearance after doing so. I forget if the intake or exhaust valve-to-piston clearance is decreased when you advance the camshaft and conversely if you retard a camshaft.

The optimal (and easier) method in my opinion would be to do this experimentation on a dyno vs. at the drag strip.

Check out this article:

http://www.hotrod.com/articles/mopp-...ng-a-camshaft/

Good luck.

Pete

[L_e_e]

My "9180" cam was installed at 107 ICL

[TomN]

Yes I understand what advancing and retarding do the cam do but experimenting on dyno cost money and experimenting in the car takes lots of time, if I can get in the neighborhood based on what others have found could really help.

If I understand correctly the "9108" can has an intake CL of 108 degrees an exhaust CL of 112 degrees and a lobe separation of 110, so it is ground 2 degrees advanced. So Lee you advanced your cam 1 extra degree. Did you do that because you found you needed it from your experience with your car? Do you race pure stock with stock manifolds? What compression are you using? Does the compression you are using work well with such a large cam? Lots of questions, sorry.

[L_e_e]

Tom,
Is your cam a Crane "Blueprint" cam or a GM cam?

I used a NOS GM 3959180 cam, I tried to copy/paste the specs that I have here but it would not format correctly and all the words and numbers run together, send me a PM with your email and I can send you a excel file.

Engine has headers and 12.5 comp

[TomN]

Lee, my cam is a Clevite brand. I have been running this cam in my car but with only about 10.3:1 compression. I had it installed at what I would call "straight up"....I didn't add any advance or retard when installing the cam. This set-up did not work well. I had to run valve lash at about .035 hot to get any performance. In another word I was having to take cam out of the engine. Engine is apart now, going to be re-engineered, and I want to get as good a sit-up as I can with the cam. I know many on here and other sites say the ZL-1 cam is no good in any case, but how can I get it as "good" as it can be. Also several on here have much, much more experience than me with this sort of thing and I am hoping to gain from their trials and errors.

[L_e_e]

Tom,
I emailed you the file.
These cams have such a late IVC that with a 10.3:1 static comp ratio your dynamic comp ratio is very low.
Here is a good calc to play with the numbers.
http://www.wallaceracing.com/dynamic-cr.php

[John Brown]

I know of a ZL-1 pure stock car that had a 396 375 horse cam swapped in installed straight up, after removing the 180 cam. Cranking compression went up and the car ran faster. Just sayin.....

[TomN]

"These cams have such a late IVC that with a 10.3:1 static comp ratio your dynamic comp ratio is very low."

I realized that but thought I would street drive the car much more than I do and felt that I could run 93 octane gas. Which I can but I get bad performance.

"I know of a ZL-1 pure stock car that had a 396 375 horse cam swapped in"

I have thought of that. Glad you mentioned "straight up" if indeed you mean the same thing as I do by straight up. Car would be much better on the street later with the deeper gears taken out too.

There seems to be several of these ZL-1 cams and it gets hard to compare them all because their specs are all (it seems) given at different values.

Lee's cam: IO 62, IC 105, EO 106, EC 73. ILC 112, ELC 74 (This 74 doesn't sound right)
LSA 109 Wallace Racing Calc gives ELC 106.5
Looks like timing numbers are seat to seat

TRW cam: IO 23, IC 59, EO 72, EC 20. (ILC 108, ELC 116 Per Wallace Racing Calculator)
LSA 112 per/WRC

Clevite cam: IO 23, IC 59, EO 69, EC 24. (ILC 108, ELC 112.5 Per Wallace Racing Calc)
LSA 116.25 per/box it came in LSA 110.3 per/WRC
Per/Box all valve timing at .050"

It looks to me like Lee's cam in ground retarded so I guess/think he did right by advancing it and installing it at 107 degree ICL. I say that because it is such a large cam and that should help to build dynamic compression.

I have seen thoughts where people said you needed a LSA of 114 (like 396/375 cam) to work good with manifolds and exhaust system. If that is so, and the box is correct, would the Clevite cam with a LSA of 116.25 work or is it still wrong because of the long duration it has?

I guess the safe bet is the 396/375 cam even thou it is wrong for a ZL-1, but looking at the numbers above, unless you have a "9180" factory cam you still ain't perfect.

[VintageMusclecar]

That cam (180) was never intended to be used with a restrictive exhaust system--I'm sure GM "assumed" anyone checking the L88/ZL1 box on the option list would be installing headers before the engine even finished cooling off from the first drive home.

The addition of headers makes it a whole different ball game--and even then, there's definitely better bumpsticks out there--have been for a long time.

Perfect example of "bigger isn't always better".