Paging Marc Haibeck: Cams

[Sgreg]

I noticed reading Marc's schedule of ZR-1 preformance mods, he does not recommend a Stage One cam change with fully ported 350 cube LT-5's. Just curious, is that because of cost /reward or ? Most tuners think a stage one treatment is worth 20-25 HP in a ported 350. Is that optimistic ? A couple of us are making that decision right now and don't need to spend more money if the reward isn't there. :cheers:

[HAWAIIZR-1]

Greg,

Thanks for posting this question. Does Marc post on here? Excellent question as there are many different opinions from the different builders.

:confused:

[rkreigh]

I noticed reading Marc's schedule of ZR-1 preformance mods, he does not recommend a Stage One cam change with fully ported 350 cube LT-5's. Just curious, is that because of cost /reward or ? Most tuners think a stage one treatment is worth 20-25 HP in a ported 350. Is that optimistic ? A couple of us are making that decision right now and don't need to spend more money if the reward isn't there. :cheers:

the FBI guys might have some thoughts on this one, Pete has done a TON of experimentation with cams on stock displacement and likely has the fastest stock bottom end car on the planet

no question you can pick up some HP with cams, even on stock displacement. how much, will vary depending on quite a few factors, porting, tuning, ect...

is it worth it? well, that depends on how "spendy" you are cams are expensive, and again, folks are working on new ones that might not be as bad but figure 1000-1500 PER cam (yikes!!)

look at the black widow and snake skinner projects. both used revised cam profiles I believe on the LT5 and picked up to 475 HP or so with the stock displacement

pete is well over that figure with more agressive porting and proper cam timing.

but it's clearly NOT cheap and should only really be considered when you are pulling the engine and porting the heads, tops end.

with the stock bottom end being rock solid, its a good way if you have "the means" to get more ponies

the amount will all depend on the full combination and getting the cam timing spot on to match the porting and tune

:handshak:

[Hammer]

Marc does not post to any of the forums as far as I know. Call him direct at 630-458-8427. I think it would be more appropriate to talk with him directly on this matter.

[XfireZ51]

I wonder if it wouldn't help to use the 93-95 cams in a ported 90-92.
It was my impression that cam profile was one if the reasons for the 405hp in the latter ZRs.

[Sgreg]

I wonder if it wouldn't help to use the 93-95 cams in a ported 90-92.
It was my impression that cam profile was one if the reasons for the 405hp in the latter ZRs.

Hmm, I thought the difference was primarily in the plenum porting changes from early to late models..

[Locobob]

Hmm, I thought the difference was primarily in the plenum porting changes from early to late models..

It was a combination of things: revised cams, intake and exhaust manifolds.

[Ccmano]

I wonder if it wouldn't help to use the 93-95 cams in a ported 90-92.
It was my impression that cam profile was one if the reasons for the 405hp in the latter ZRs.

There's a 4 degree increase in valve overlap, lift and duration are the same. Most of the increase was due to the porting in the plenum, IH's and cylinder heads. Also the changes to the exhaust system.
H
:cheers:

[Pete]

I will not get into this with cams on an open forum i might get the boot :) some might think i'm bashing/insulting them.
Just compare for yourself.

Stock Cam Specs
Intake .214 .229 .390 .390
Exhaust .214 .214 .390 .390

Stage I Specs
Intake .228 .228 .415 .415
Exhaust .228 .228 .415 .415

Look and compare the two cam set up and tell me what's the differance,besides lift.

You can figure it out yourself.

Pete

[XfireZ51]

There's a 4 degree increase in valve overlap, lift and duration are the same. Most of the increase was due to the porting in the plenum, IH's and cylinder heads. Also the changes to the exhaust system.
H
:cheers:

Hans,

Are you saying cam profile was the same, just LSA was tighter? It would make sense that if both ports are flowing equally, that you'd want same intake for both primary and secondary. Not sure about exhaust needing any help as I have heard it's pretty efficient already and then if you throw on headers...
You want to make certain you don't over-scavenge robbing power.

Pete,

Who would give you the boot over a discussion on cams?!

[FU]

The stock cams look real healthy for a 4 valve per cyl. engine.
In comparison the stage 1 cams appear to be pretty radical (IMO).

[XfireZ51]

The stock cams look real healthy for a 4 valve per cyl. engine.
In comparison the stage 1 cams appear to be pretty radical (IMO).

Frank,

I forget who I was speaking to while at BG, but they mentioned that the stock motor was actually "overcammed". Could explain why ported heads work well with stock cams.

[Ccmano]

Hans,

Are you saying cam profile was the same, just LSA was tighter? It would make sense that if both ports are flowing equally, that you'd want same intake for both primary and secondary. Not sure about exhaust needing any help as I have heard it's pretty efficient already and then if you throw on headers...
You want to make certain you don't over-scavenge robbing power.


This information was published by Mercury Marine in a 1992 bulletin...
H
:cheers:

[FU]

I will not get into this with cams on an open forum i might get the boot :) some might think i'm bashing/insulting them.


Pete

I understand Pete , but also no one would/should think that you are bashing them. Sharing yes.

Frank,

I forget who I was speaking to while at BG, but they mentioned that the stock motor was actually "overcammed". Could explain why ported heads work well with stock cams.

IMO the stock cam's are fine for a stock mildly ported 350.

[Pete]

Hans,
Not sure about exhaust needing any help as I have heard it's pretty efficient already and then if you throw on headers...
You want to make certain you don't over-scavenge robbing power.

Pete,

Who would give you the boot over a discussion on cams?!



Oh,I forgot this is not a corporate sponsered and run forum.


:thumbsup:
Exhaust does not need that much help,the exhaust/intake ratio is well over what N/A motor needs.
Do a web search a good ratio for N/A motor is 75-85% we have well above that on a stock head so porting the intake helps bring those #'s closer to perfect.

With big exhaust cams,unless you go with nitrous or turbo/supercharged you will find it hard to tune, idle quality suffers, loose some low end power/torque,drivability suffers .

DRM had .239 intakes with stock exhaust,LPE had B cams .239 IN. .221 EX
You may ask why have Stage III's or LPE C cams because bigger is always better :)

What i have seen is what GM figured out over 20 years ago keep exhaust duration around 15 degree split.

Pete

[Locobob]

I'm feeling pretty well bashed and insulted Pete, you should be duly booted :mrgreen:

I've been thinking about our talk at BG. To bring the lift up to .425 requires taking .035 off the base circle but to get more duration don't you need to take off more than that? Working on figuring out a way to measure valve height in relation to the cam journals... damn you for giving me ideas Pete :mrgreen: