Maybe a custom cam would be more your speed. The hotcam would make more TQ, and the C306 would make more HP on a 383.

Yeah get some flow numbers of those heads, and then get the same numbers with the intake on it too. That will tell you how much work needs to be done to the intake.

CAJUN-Z has a great point. No use in a engine with HP in the wrong part of the RPM band, about 75% that is because of too much cam.

Some more on Trey's post. Shifting early is a good sign of bad cam selection. You need to shift as late as possible (where it makes sense) Basically you want the engine to run in a RPM band were it has the most average power. He has a good grasp on all of what he said actually, that's good to see. One thing all the "miniscule and neglegable" things you are talking about is what gets you records, money and good times. Engines are not one thing, they are alot of little things optimized to get the most from what is there.

BTW There is no magic bullet, just like there is no magic cam. It's all physics, magic has nothing to do with it. I hate to see about 50% of the treads on the regular boards about cams. They are not easy to understand, but they are also not magic either.

Bret

 

I have been reading this thread and now have a question. Is it the airflow, velocity, or port size, or a combonation of the 3 that allows a stock LT4 head car be better matched with say a larger cam then a stock LT1 heads can? If that is the case, couldnt a simply DIY p&p of the LT1 heads allow you to not allow the heads to fall on its face at higher rpms? Now that I think of it, isnt it the port velocity that needs to be matched to the cam, so as the cam isnt holding the valve open longer and the heads not being able to keep up the the cam at higher rpms? Like how the TPI LTR setup has great velocity for stump pulling tq, but doesnt have the velocity at higher rpms to keep up with the motors demand, kind of like how you have to have a tb cfm and engine rpms match for the motor to flow that high?

So to make a long conclusion short isnt cfm a verson of measured velocity?

 

CFM is volume, Velocity is speed.

That's a jumbled response, so I'll see what I can answer.

Let's throw out the LT4 vs LT1 stock heads and do a LT1 vs LT1 ported head comparison. All on a 350.

LT1 flows about 215cfm @ .500
LT1 ported flows 255-275cfm @ .600

The velocity is better on the ported version. It's also a bigger port, 198cc vs 170cc.

Both heads are running a LT1 intake.

The ZZ3 cam 208/221 for the LT1 stock heads is what I like
A 218/224 cam for the ported LT1 heads is what I like, unless it's a high rpm engine where a 224/236 will work better.

The stock heads don't have enough port volume or flow to support any flow above 5000rpm really, so the smaller cam will maximize that TQ in that rpm range. The ported heads will flow and have the port to support 6500rpm easy, so you give them more duration.

You could throw more cam at either one of these combos. It's going to require more RPM and the lower RPM band will suffer.

O.k., it's late, but do those ramblings help your rambling any more?

Bret

 

bret,
wouldn't the 306 make more torque as well as more power in the 383?

Also, to add to the list-
what is your personal opinion of the 306CC?
How would you compare to an Xe cam?

the short intake durration when compared to the exhuast or (long exhaust compared to the intake- however you want to look at it) is what bothers me.

 

Bret, thanks for answering that. It was late at night and I have a hard time putting into words what I am thinking.

Also if you run a 383 vs a 350, without change of heads, say stock LT1s, would you be able to run more cam since the 383 would make the same cam in a 350 tamer?

 

Trey,

"bret,
wouldn't the 306 make more torque as well as more power in the 383?

Also, to add to the list-
what is your personal opinion of the 306CC?
How would you compare to an Xe cam?

the short intake durration when compared to the exhuast or (long exhaust compared to the intake- however you want to look at it) is what bothers me."

The reason it would make more TQ is because of the cubes. Cubes eat up duration and port size. That thread on the AFR heads shows a good numerical relationship with that.

The 306 is a decent cam. It's too much for a stock LT1. Unless it's a drag car that turns REALLY high revs, which on a stock bottom end is not good. I'll tell you a good place for it, that Dam MTI 396 in Thunderturd, sorry Chicken. What a waste of a forged bottom end. Spends STUPID money on the nice parts in the bottom end, then no heads on top of it and way to small of a cam in the 305. It needs more head flow, a better intake, more port volume, more RPM, more duration, more lobe area and more lift.

I work alot more with custom cams, because I want something that fits the engine better. So the XE and the High Lift HR lobes are what I work from. The 3192 lobe is a very usefull lobe. Most times a custom cam is the same price as a off the shelf one

The split between the lobes of 14 deg is a bit much. I like less than that normally, around 10-12 is better, but it's all what the engine needs. I really think the duration is too high and there is not enough lift, even with 1.6's.

BTW even in a stroker LT1 I use much less duration than a 306.

mastrdrver,

"Also if you run a 383 vs a 350, without change of heads, say stock LT1s, would you be able to run more cam since the 383 would make the same cam in a 350 tamer?"

Yes, as I said cubes eat up duration and port volume. My golden rule is that spend the $ on the heads first, then match the bottom end to the HP level. You need a bottom end to feed cubes, a 383 with stock heads will not make any power really, just alot of low end TQ. Basically a good truck engine.

Bret

 

I thought the 114 was a bit too much for my NA car as well so i went 112. (236/242 on 112LSA). My car isn't really done since I didn't get the heads on yet (ran out of money durring build up, ran of time now to swap the new heads on) so I just got it generically tuned to shift at like 6100. When I get heads i'll start caring but for now I couldn't care less. Anyway, I REALY feel it pulling right before it shifts.

i'm also confused by this
Weren't you an advicate for larger cams a few lines above that?
Or was that because of the stock heads?


Side note to Brian-
I was not ignoring your IM/Question/Comment-
I was away

 

Bret,

Your're right Thunder chicken is disapointing. Less than 400rwhp from a stroker with a m6????

One of the reasons I like the 306 is because I have heard the cam in a couple cars and I like the lope. It sounds like a real cam.
I realize that this isn't the way to select a cam but I have wanted something like that since I put in the hot cam and was not happy with it.
It's probably stupid but I'm having a hard time spending a lot of money on a engine that doesn't sound like one.
I'm still going to have the heads flowed and cc'd.
How much work can be done to a LT4 intake? I thought not much could be done besides a gasket match????

What is this engine masters challenge?

Thanks
Tom

 

I think the one big reason they went with the cc305 on Tunderchicken is bcuz they had to meet emissions in NJ, though Im sure they could have gone bigger and still passed.

Bret, I was wondering what your option was on the 3100 series lobes from comp is? I know you said that you like them, but when does too much rpm and too fast of lobe ramps become a negitive factor? Also, comparing a cam like the 230/236 112, one with the 3300 series lobes and the other with a 3100 series lobes, will one peak faster then the other or should they peak at the same rpm? I know that the advantage of more lift is more power under the curve, but does faster lobes effect where peak power comes into play?

Reason I asked is bcuz I am looking at getting that sam cam but on the 3100 series lobes on a LT1 350 with ported heads, but wanted your option since no one else I have run across doesnt seem to have an idea. Thanks

 

Too many questions at once here:


Trey,

First, you should really start to feel that cam with heads WAY above that.

And yes, with stock heads I like less duration. With more head I like a little more duration but not alot there either. I'm usually a advocate of small cams.

TCAL95Z,

One day I will have to pick apart that Thunderchicken buildup. You could make a custom cam and still pass emissions in NJ. I had one ready for a big HP 383 LS1.

As for lope, the cam that's going into 96z's 383 is smaller than a 306 but will idle just like a 306 about. You tell me what you want, I can make a cam do just that. Well to the point where physics steps in and says Hey, can't get there from here.

I don't gasket match, I port match. Once you start doing some crazy things with intakes and angle milling, if you gasket match things come out really wrong. The is a down side, it takes FOREVER TO DO! About $210 worth of work to make the ports and port matching do what I want. From the size of the runners that the LT4 intake comes with thought there is power to be had there.

Check out www.enginemasters.com and do a search on this forum for it. You'll find some cool things.

BTW right now I have a finacial problem, that's about my only barrier to getting in that contest again.

Mastrdrver,

I combine the 3100 and 3300 alot even on the same cam. The main barrier to the higher lift stuff is spring pressure. With good springs you can handle 6500-7000 rpm with any of those lobes, but you have to do everything right.

Your peak question is interesting. They should peak at about teh same RPM. The one with more lift should make more power throught the RPM band. There is a point where alot more lift will allow you to run more RPM, and it will move the peak some.

The faster lobes basically eat up lifters. Right now I'm about ready to get the machines fired up and start making those dam Comp R's. Those things are my life blood in HR engines. If Comp doesn't get on the train soon and start selling them again, I might have to get OldSStroker on it. We could build them, they would just cost about $400 a set. But at least you could find them.

If you want to run a 350, with a 230/236 on 112 LSA..... I would rather have a smaller cam. Take about 6 deg out of the intake at least. Something like a 3119/3316 on a 112 would be better. MAKE SURE THAT THEY GRIND IT ON A 112-111 ICL, not a dam 108 ICL like they always do.

Man I gotta be a Comp Cams dealer. I put more cams on this board than the law allows. BTW who is selling Comp's stuff at the best price? And what does a HR LT1 cast and billet custom core go for? I have some idea, but I want to know the market price.

Bret

 

Like I've stated before, if you really want to make a cam selection based on "science" then you'd need a PV diagram of the engine, so as to know where those optimal cam events should take place. That's how the big boys do it..... not to mention they use quite prolific wave simulation software.

Where people seem to make their biggest mistake (from a racers perspective) is in not matching everything up. The cam size doesn't matter as much as getting everything to work in the rpm band where you make your power. We were running less than adequate cylinder heads and lots of cam back some years ago.... we still went quick by gearing the car for the revs we were dealing with.

-Mindgame

 

I should "feel" the cam start to pull AFTER 6000r's?

 

Yeah I would imagine,

I would rather have a cam slightly die off right before I shift.

A cam change could make that happen pretty easy.

 

With all due respect-
I cant see this thing revving past 6800-7000 with good heads in a 383.
Its big, but not that big

I think it will peak around 6500 or so though. thats the butt-o-meter. I'll have a dyno in a few weeks.

 

trey i think its more of an effective lobe area than anything and although your lobes may apear be smaller than the cc306's with your lift being increased over it and the steeper ramps you're probably actually running a cam that has a larger effective flow area than the cc306 but has less overlap and so it is much better behaved.

just an idea. i'm sure bret will pick it apart for me later lol.