Cam specs vs. Head flow #'s on 3.8

[Magnus]

Do I have to spell it out for you Scott?

Owners of Thrasher heads have told me the P&P job was crappy. They wouldn't buy another set of heads from Thrasher. It looked like something you could do in your own garage.

But you are the exception Scott so order Thrasher heads and prove me wrong ok. [img]smile.gif[/img]

[scottblack]

Thank you! Was that so hard? [img]smile.gif[/img]
Check your mail, please.

Can we discuss cams now?

Scott

[Magnus]

If you want to look at more sets of GOOD heads like Supersix's.... INTENSE has a set of heads, for a high price, found at www.3800performance.com. Some of the fastest FWD 3800's use them.

They look like a good set of heads. Coming from INTENSE I'm sure that the quality is definately put into each one too. However I think the supersix heads are still a more cost effective solution.

[scottblack]

Thanks.... still going to wait on the Riggs dyno results.

........Cams?

Scott

[Magnus]

What is your question about Cam's?

[Arctc Wolf]

I have a question. What happens if you get a cam that's too big for the engine? Do you lose power, or does it just idle like crap? I'm looking at eventually getting P&P'd heads, dunno who from yet. The cam would have to be able to pass california smog, so nothing really extreme. I'd be looking for great midrange, 600-800 rpm idle, big duration, lift, and lobe separation. basically, I'd be trying to schieve the same overlap as the stock cam, but have more lift and duration, so i figure I'd have to increase lobe separation accordingly. I'd have all of the intake and exhaust stuff already done, all I have to do now is put in my FTRA and buy headers and a bigger outlet cat. and I'd be ready. I'm not looking at getting all this anytime before April of next year, cuz I wanna build up a few more things on the car so I can make the most of the power I'd get from heads/cam. I've seen all the pre-made cams for our engines, but I'm looking at getting max power midrange while passing smog. Any suggestions?

[scottblack]

Well with the cams.........
To me it just seems that our specs are so small for what we try to achieve. No, 212/212 is not small, just that i thought you would try for something a big larger for your NA beast.
I was thinking something like 218/224 112 LSA? I see the math now on why you don't NEED to favor the exhaust side, but I think it is worth a try? If it doesn't work then I'll be the goat okay? I feel the need to take initiative and be the guinea pig since Blucamaro's car is still not up and running.
What are your thoughts?
Also check mail again. [img]smile.gif[/img]
Thanks,

Scott

[scottblack]

I guess it would also help if i posted what i wanted out of the motor....

Basically, huge top end and mid range. I want serious power, driveability is of minimal concern because i will tune it with the MAFT+ .

Edit: I just caught that segment of ported heads application. Strictly NA for me, so how about 224/224? Too large you think?

Thanks,
Scott

[ September 01, 2002: Message edited by: Scott Black ]</p>

[HAZ-Matt]

Scott Black: "Strictly NA for me, so how about 224/224? Too large you think?"

Although I do hesitate to speak for Magnus...

Magnus, from different thread: "I might do 224/224 112 in the future.. who knows."

It would seem Magnus doesn't think it is too large.

My question about cam profiles is whether or not we know where a certain cam will make power on the 3800 besides guessing; meaning that can we narrow it down to the rpm where we will be making peak torque or hp rather than saying things like "in mid range" or "in high range" or possibly "past the rev limiter?" There is bound to be a way to model it, however that is outside the realm of my expertise.

Also, in response to a query posed by Dominic...

Magnus: "Now to answer your question, yes the 115 will be tamer than the 112 however the 112 should make more power, more useable power. The 115 may have a bigger peak however it will be higher in the RPM range, possible past our rev limiter even." August 13, 2002 02:04PM

In a later thread...
Dominic: "A lower LS means more valve overlap. The more overlap, the more idle lope, and the higher the powerband goes." August 24, 2002 12:10PM

Is it my imagination, or are these two statements contradictory? On howstuffworks the cam article shows their "high performance cam" with overlap, while their "simple" cam had no overlap whatsoever. The point was that the "high performance" cam was better above 4K then their "simple" cam, which would not allow the engine to breathe well at higher rpm. If anyone could shed some light on this, it would be helpful.

Moving right along...
Scott Black: "I was thinking something like 218/224 112 LSA? I see the math now on why you don't NEED to favor the exhaust side, but I think it is worth a try? If it doesn't work then I'll be the goat okay? I feel the need to take initiative and be the guinea pig since Blucamaro's car is still not up and running.
What are your thoughts?"

This is probably for Mr. Magnus, but here are my thoughts:

Personally, I don't understand the math, because I haven't seen it, but I would tend to believe Magnus if he says that the math says that you don't need it.

However... there is the old post by Dom:
"Here is an something I got back in the 90s when LT1s still ruled the planet.


CC304 210/220 .500 .510 114
CC305 220/230 .510 .510 114
CC306 230/244 .510 .549 112

Now CC305 is a mild cam, but CC306 is a pretty big cam. They added 10deg to intake and 14deg to exhaust and added 0 lift to intake and a whooping 39 to exhaust. Cars dyno 400rwhp with that cam and heads and headers. I believe chevyguy from mfba is running 11.34@120.3 NA 1.55 60'with that cam. But CC305 is just a mild cam. I see alot of exhaust lift added and no intake lift added. I also see 14 deg more duration on the exhaust side and .39 more lift. So exhaust is favored alot and it works. Hmmm. Balancing the airflow. Why not 210/216 .450 .490 vs 214/214 .450 .450? You will be hard pressed to find an LT1 cam with equal duration on intake and exhaust or even equal lifts. Now to further prove my point. There are alot of equal duration and lift cams for LS1. Why? Cause LS1 heads flow much better then LT1 heads do on the exhaust side so they don't need more help from the cam. At least you're adding compression as you know by now you have to do.

One thing though that noone on this planet knows is how well the 3.8 heads flow. This is still highly experimental period. I'm willing to bet its more like LT1 heads then LS1 heads. But who knows."

So do we know how the 3800 heads flow now? One last thing... it would seem that the stock cam favors exhuast. Why is that, fuel economy? Or should we really consider favored exhuast on a NA 3800?

[ September 01, 2002: Message edited by: HAZ-Matt ]</p>

[Arctc Wolf]

Another question, why are guys saying to go 112 ls or 114 ls? what's wrong w/ 113 ls? also, i think stock cam's favor exhaust because it allows all of the hot exhaust to get out of the cylinder so the cat lights off quicker, allowing less emissions. just a guess.

[scottblack]

Mike Huff's cam is a 113 LSA, he got it that way for nitrous use as well as NA.

Keith has an idea of how well our heads flow after being ported. Seemingly they seem to be pretty balanced (in terms of intake and exhaust flow) so that is why he suggests symmetrical durations.

Personally (and i could be wrong) but if you have stock heads i think your exhaust duration should be favored more. But again I could be wrong. With ported heads i am beginning to agree that they are balanced.

Where are ya Keith? [img]smile.gif[/img]

Scott

[Magnus]

Arctc Wolf, A cam that is too big will idle worse. It will also make peak power higher in the RPM band.. perhaps too high. If your shifting at 6000 and your cam peaks at 6500 then your cam is too big. If your looking to pass emissions then you really shouldn't be thinking about big cams. I have no idea which cams will pass emissions and which wont. Sorry.

Scott, with my cam it continues making power at 6K.. I'm guessing my peak is around 6200. I will dyno this cam before I decide if I want a larger one. If my peak is up there with this cam, I will not be upping duratin. I don't want to spin my motor to 7 grand.

Sure you can try favoring the exhaust. It will just make it idle a little rougher. I cant say for certain you won't make more powre than a symmetrical cam. However in theory I believe symmetrical cams are what we want. (On an intake/exhaust/heads car)

MAF T+ doesn't tune driveability.

224/224 is too large if you want to shift at 6K. If your shifting higher up there it might not be. I really don't know for certain just yet. We need to see more dyno's of COMP grinds.

HAZ-Matt, we just need to see more dyno's of COMP grinds. I'll be dyno'ing mine to 6700 RPM's sooon probably.

I believe Dominick was a little confused. Yes those statements are conradictory.

Both Thrasher and Supersix have posted flow #'s... I'll see if I can get some more in the week. Our heads flow VERY well on the exhaust. Especially ported ones.

Stock cam favors exhaust probably for fuel economy.

Arctic Wolf, you can go with 113 sure. It's just easier to differentiate between 112 and 114

I believe Mike's cam is 113 because they couldn't get 112LS out of the regrind.

With stock heads, sure a small exhaust favor is ok. Especially if you want to use nitrous on stock heads.

Also, I'm glad you guys are doing searches. [img]smile.gif[/img] Very cool.

- Keith

[HAZ-Matt]

Ok, so higher LS moves the peak upward in the rpms.

Also I found a page that might be more useful to people then howstuffworks:

http://www.webcamshafts.com/cam_glossary.html

Near the bottom is a description of the effects of varying lobe separation.

Effects of tightening lobe separation angle:
Moves Torque to Lower RPM
Increases Maximum Torque
Narrow Powerband
Builds Higher Cylinder Pressure
Increase Chance of Engine Knock
Increase Cranking Compression
Increase Effective Compression
Idle Vacuum is Reduced
Idle Quality Suffers
Open Valve-Overlap Increases
Closed Valve-Overlap Increases
Natural EGR Effect Increases
Decreases Piston-to-Valve Clerance

Take the opposite for making the lobe separation wider.

[ September 02, 2002: Message edited by: HAZ-Matt ]</p>

[scottblack]

<blockquote>quote:</font><hr>Originally posted by Magnus:

I'm guessing my peak is around 6200. I will dyno this cam before I decide if I want a larger one. If my peak is up there with this cam, I will not be upping duratin. I don't want to spin my motor to 7 grand.

Sure you can try favoring the exhaust. It will just make it idle a little rougher.

Our heads flow VERY well on the exhaust. Especially ported ones.

With stock heads, sure a small exhaust favor is ok. Especially if you want to use nitrous on stock heads.

Also, I'm glad you guys are doing searches. [img]smile.gif[/img] Very cool.

- Keith<hr></blockquote>


Agreed, I don't want to go to 7k either. :eek:

I don't mind a rough idle one bit.

Ok, when you say that our heads flow VERY well on exhaust, especially ported, i still don't understand why not favor the exhaust side. Is the difference of the intake flow vs. exhaust flow made equaled out once ported? Or does the exhaust STILL flow more after porting?

This is why i still want to favor the exhaust side and run the 218/224. If its not enough i can always go up to 224/224. No nitrous for me. [img]smile.gif[/img]

Searches help you learn. Of course I will take advantage of that feature. [img]smile.gif[/img]

Scott

[pgriffith]

I dont know everything yet...But I do know Supersix makes a great set of heads. They are high quality and very affordable. PLus you get the bonus of working with such a nice guy as TOM. I would recomend these heads to anyone. As far as cam's I think I would listen to Magnus he seems to know alot about our motors and how they work.