Chevy 307 engine

He did say he has a M21 so converter stall is not important for this job.  

Good post. 

Just as I thought, you didn't have a clue when you stated that Comp's "lobes are a lot better designed" than Edelbrock's.  However, I'd still like to hear you tangle yourself up while trying to explain what you meant.  :o   

As for "dyno sims," I think you have me confused with someone else.

Edit:  Hmm.  I noticed you deleted message #31, which this post is in response to. 

Well, again I need help.  I couldn't find the casting numbers on the head, but I do have a publication I received from GM that shows the stock valve sizes in a 307.  Is this what you need to run the dyno sim?

Here are the specs I found:

Intake Valves: Diameter 1.715-1.725

Exhaust Valves:              1.495-1.505

I looks like what you mentioned about the valve size is true..... But, this is all I have to work with at this time.  I hope there is something out there that will somewhat help!!!

Thanks for all your help.  I really appreciate it.....

Yeah, sorry.  I am getting all mixed up on who's here.  I have read a few articles (cannot remember exactly where now) that led me to use the Comp on my current engine. They said the Xtreme energy lobes have a more aggressive ramp design to open the valve a little faster, more like a roller cam lobe.  I cannot produce a bibliography yet but I have used the Edelbrock and Comp Xtreme cam with about the same lift and duration and just find that the Comp makes for a crisper, more torquey feeling engine.  Better throttle response using the same carb.  

What you're discussing - lobe ramp speed - is referred to as "lobe intensity."  This describes how quickly a valve will open and shut.  It's actually quite simple stuff.

When we discuss duration, there's typically two numbers referred to:

- Net duration (computed at 0.050" lift), and

- Gross or advertised duration (typically computed at 0.0040" lift).

Let's say the advertised duration of the intake is 280* and the net duration is 230*.  The difference of 50* is referred to as the "lobe intensity."  For performance applications, less intensity is better.  Less intensity = quicker valve opening and closing.  Additionally - and this is the real boon with less intensity - the valves spend less time at very low lifts which tends to bleed off cylinder pressure, but does not allow for any measurable airflow.

As example, roller cams have shorter or less intensity.  Thus, enabling the valves to open to full lift and shut quicker.

To further illustrate: If two separate cams have the same lobe sep, valve lift and net duration; but different lobe intensity.  The cam with the smaller intensity will idle smoother, have crisper off-idle throttle along with a broader power curve.  Said differently, the lower intensity will offer superior low-end without sacrificing anything on the top-end.   

Your casting number is under the valve cover, usually between the rocker arm(s). its a number that looks like this "333882" or "3927185" .

The information you provided should be good enough. I asked for the casting number as a way to verify the specifications of the head, but since you have that information, we are all good.

Just to give you an idea of cost, the heads I pulled from a 305, cost $16 per head. I don't know what salvage yards in your area charge but, they are probably pretty cheap.

The other thing I am not seeing being mentioned when talking about cam lift, is how it will effect flow through your head.

Obviously more duration and more lift will help flow more air through the head. But in my own tests, and what I have seen others do, stock heads usually don't flow any more air above .400" lift, unless you enlarge the ports, polish etc...  CFM flowrates I have seen for stock heads only give about 1-3 more CFM at .500" over .400". 

Has anyone here posting tested flow rates? Am I pretty close to you're guys thoughts on that?

My initial dyno results are the following:

307 - 3.875" Bore / 3.25" Stroke

9.09 CR  -1.7IV / 1.5EV 70CC Head Stock porting / low performance

Xtreme E-Cam 250H-10 .432"/.444" - 250/260

RPM        HP       TQ             Vol. Eff%

2000     135      353              78.9

3000     201      353              81.8

4000     252      331              83.1

4500     260      303              80.2

5000     252      265              75.3

Edelbrock Performer @.050 .420"/.442" - 204/214

2000     128       337             79.7

3000     198       346             81.7

4000     257       337             87.0

4500     271       316             85.3

5000     267       281             80.8

My next dyno posting will show these cams with a 305 57cc head.

Dyno Sim #2

307 - 57CC 1.85IV/1.5EV CR:10-10.5

All sims are run with 600CFM 4bbl carb, dual plane manifold, Small tube headers with free flowing mufflers.

Xtreme E-cam 250H-10

RPM          HP        TQ        V.E%

2000        142       374       80.6

3000        218       381       84.4

4000        286       375       87.2

4500        312       364       86.8

5000        325       342       84.7

5500        324       309       81.0

6000        311       272       76.2

Edelbrock Performer

2000        136       356       81.5

3000        213       372       86.1

4000        288       378       91.0

5000        336       353       91.3

5500        342       326       87.1

6000        331       290       82.3

As you can see, based on these results, the Xtreme cam falls off sooner in the power band than the ebrock. However the ebrock makes less TQ in low RPM. 

What is more important to you will base your decision here.  I did not post numbers from the 256H cam since they are almost identical to the Ebrock.

My choice of the two would be the Xtreme cam since you need more lowend torque to get moving from a dead stop. The cruise RPM range (2000 - 3500) makes the most power with this cam.

Note: sim shows that with the smaller 305 57CC heads, better flowing with larger valves, the power the camshafts make increase to the 325-350 HP range. The stock heads unfortunately barely muster over 250.

Note:  Stock exhaust manifiolds will restrict performace to the 220HP range when used with existing heads, 260HP range with 305 heads.

x11nt4,

This is great!!!  Looking at your results on the sim has helped me understand more of what I'm trying to do, along with what I should do it with.

I just want to share with you what the same GM document has as far as HP and Torque for my engine:

Gross HP @ 4600 rpm - 200

Net HP @ 4000 rpm - 135

Gross Torque @2400 rpm - 300

Net Torque @ 2400 rpm - 235

Sooooooo, what you're showing me is a significant improvement even with the stock heads.

(Now I'm not sure what the difference between gross and net HP/Torque is, and if your sims calculations are gross or net, but its still better)

My understanding is,  Gross HP and TQ are figures GM used to measure performance without accessories. Such as alternator, AC, PS pump, etc.  Net HP would be with those accessories installed and functioning. Obviously the AC would be the largest of the bunch to draw HP when being used.

The numbers GM gave you are the maximum for the engine. After the RPM stated is where power curves start to fall off. As you can see, with a new cam, your engine will make more power throughout the curve, and will continue to make power well into the 5K range. 

Another Cam I saw which is virtually identicle to the 250H is the Xtreme 4X4 250 Cam.  The 4x4 cam's are basicly the same but the step up in lift and duration between the cam types is less than the steps between the Energy series.   It also looks like they changed to exhaust open/close times slightly compared to the energy cam.

Also, just for fun I ran a dyno with the Energy 250H cam retarded 4 deg. And the results pushed that cam into the 340HP range from 324 with only losing 2HP at 2000k and about 8 at the TQ.  That will probably make that cam, at that degree of retardation the best.

When you run these sims, are they simulating gross or net HP/TQ?  

Gross HP/TQ at flywheel.  Obviously the rotational mass of the driveline, coupled with your accessories will slow the motor down, but this is true with any vehicle.   So if you were to do a rear wheel dyno of your truck, it will probably be 15-20% less than the scores shown.  Also this is based on (I think anyway since there is no option to change it, which is a beef I have with this software) on sea level. I usually figure in a 2% loss of flywheel gross power per 1500ft of altitude.  I do not know if 2% is the most accurate % of loss, but I used that based on the recommended stage down Edelbrock has in their book for jetting their carb based on altitude. Basicly goes, per 1500 ft.,  go 2% leaner.  I figure since this carb is setup at sealevel, they are saying there is 2% less air at 1500ft.   I have no idea if this is right, but I figure if this is off and you show more rear wheel HP, then hey it's all good.  It's just so you have an idea. Gets you a ballpark figure...

Well, again thanks for your help.....  There will be a day (i hope) that a 350 is in line for this truck, but for now this will make a big improvement. 

Ive done some reading and happen to see HP TV last week and I have a pretty good feel on how to do this.  If you have any suggestions Im always open. 

Now off to Summit Racing to order the parts....

My final point, everyone has 350's. Every car and truck ever made by GM that has a V8 is either a 350, 305 or 400.

I'm not sure what you mean by this statement. Of course GM has made so many displacements over the years that I don't have the space to list them all. And, not EVERYONE has 350s, but it IS a popular motor. I can understand you wanting to build up something else to be different, which is admirable, but the SBC is such a great design that it's tough to argue against it. It is commonly available, cheap, efficient, and there are boatloads of parts available for it. What part of that is BAD? I can uderstand if it's not for you but to trash the design is just ridiculous. How many races have been won by the SBC? Too many to name. And, don't a$$ume about jcharliem, he is pretty hardcore, AND walks the walk. Yes, Reading IS learning, but it isn't everything. A dyno simulation is just that, a SIMULATION. I'm glad you like your 307. It is obviously a combination you like, and it works for you, but I don't think trashing one of the best engine designs ever is going to do you any good over here.

Maybe a typo, or I mis-read something. 

The duration numbers you listed (and therefore, I presume these may have been the numbers used for the simulation) don't appear to be measured at the same lift.

The Xtreme cam (250/260) appear to be "advertised" duration*.  While the E-brock cam (204/214) appear to be measured at 0.050".  You might want to double-check these and re-run the numbers.

* Net, a cam with lift below .450" wouldn't have "effective" duration above 250.