Another Camshaft Recommendation Request...

Here's what my Dyno program is telling me...

It looks like the system is meeting my performance goals (flat torque / 425 HP). I am wondering about "streetability" and ease of driving...

Note: Flow Data in the program is based on the 4V heads with port plates...

You asked a cam grinder and he is the expert.

From what I know, this cam is going to have a very stock like idle and the engine will pull with a lot of torque into the 6000 rpm range.

With the duration and overlap shown it will idle hot somewhere in the 750 rpm area and should have 15in-mg at idle.

It is going to like the typical 14-16 degrees initial timing and probably won't have any problem with 36 degrees total advance but that's something you need to determine after you brake in the engine.

The timing curve on pump gas is more an issue of how fast it advances to full rather than the total.

The open chamber heads with the domes in my experience are forgiving in that respect but they give up the crispness that the opposite set up, i.e., the closed chamber heads with flat top pistons give.

The trade off is that the closed chamber heads regardless of the pistons tend to detonate quicker and probably would need to be held to 32 to 34 degrees total.

As a matter of fact I seem to remember playing with the advance in the 38 degree total with the open chambers but that got complicated and 94 octane was needed.

I think that this cam is as close to what you asked for as you can get.

The question is whether or not when you drive it, you find the engine disappointing and expected more?

So that's my "Skippy Peanutbutter Hour show" opinion. You asked for it, you got it.

Thanks Doug -

From earlier discussions on this same topic, you seem to be a guy who likes a lot of cowbell cam in your engines....

It seems like at this point, the choice of "how much" cowbell cam is kind of subjective, especially if a person has not had a lot of experrience with varying amounts...


Christopher Walken on Cam Selection


PS> No disrespect - I think the video is very funny, and it was appropos.

Regards -

Rocky

Nah, a cowbell means a bad rod bearing and if I heard that, then the gold plated diaper would be necessary?

You're right about the sound! Funny.

Hey Rocky,

I'm not sure what specs the vendor recommended, but your screenshot from the cam simulation software is almost my exact cam.

My Engine:
Original 351C bored .020 over and stroked to 383
Edelbrock aluminum heads, ported by DSC Motorsports in SoCal, larger valves than stock Edelbrock (2.11 int / 1.65 exh)
Lunati Pacaloy beehive valve springs
Scorpion 1.73:1 roller rockers
Ford Motorsport Early Block Retrofit linkbar roller lifters
Custom roller camshaft (specs below)
Cometic MSL head gaskets
Forged Scat lightweight 383 stroker crank
Forged I-beam rods
Forged Probe dished (16cc) pistons; Calculated compression ratio 10.65:1
Weiand Xcelerator 2V single plane intake manifold, carb pad milled flat
Holley Avenger 670cfm carb w/ vacuum secondaries
Ansa GTS exhaust
Mallory electronic ignition - Unilite distributor, Mallory 6AL ignition controller, and MSD Blaster 2 coil

Cam specs - Recommended by Dan Jones and then revised by Oregon Camshaft:
Duration @ .050: 224 int / 232 exh
Lift: .578" int / .588" exh
LSA: 110

You can hear the engine here:
http://www.youtube.com/watch?v...QlA&feature=youtu.be

quote:

The trade off is that the closed chamber heads regardless of the pistons tend to detonate quicker and probably would need to be held to 32 to 34 degrees total.

I think Doug meant to say the "open chamber heads" tend to detonate quicker. The closed chamber heads are typically less susceptible to detonation.

quote:

Originally posted by garth66:

quote:

The trade off is that the closed chamber heads regardless of the pistons tend to detonate quicker and probably would need to be held to 32 to 34 degrees total.

I think Doug meant to say the "open chamber heads" tend to detonate quicker. The closed chamber heads are typically less susceptible to detonation.

No. In my experience, everything given equal it took 38 total to make the open chamber heads detonate and 32 on the closed chamber. 93 octane.

In addition, the curve on the closed chamber heads needed to be slowed down so it wouldn't be all in until 5000 engine rpm.

The open chamber was slowed also but was all in at about 3100rpm.

This is oppesed to my Boss quench heads and TRW pop up pistons running on Sunoco 260 that was all in by about 2,200rpm, 36 total, and if the city was going to bring back trollie trains, they would have hired me in that car to cut the grooves in the roads with the tires!

Those are my experiences and I do not claim to be the authority on this at all so there will be no pissing match challenges here by me.

Thanks to all who are looking at this and have commented....

So Garth - I saw you had recently gotten your car running with the new engine (and you may or may not be in the same situation as me, where you may have been running a mostly stock motor with some performance upgrades prior to your engine swap)...

How do you like the motor and the overall performance characteristics? Easy to drive, and goes when you want it to?

Or not enough / too much cowbell ?

Thanks =

Rocky

quote:

Originally posted by PanteraDoug:

quote:

Originally posted by garth66:

quote:

The trade off is that the closed chamber heads regardless of the pistons tend to detonate quicker and probably would need to be held to 32 to 34 degrees total.

I think Doug meant to say the "open chamber heads" tend to detonate quicker. The closed chamber heads are typically less susceptible to detonation.

No. In my experience, everything given equal it took 38 total to make the open chamber heads detonate and 32 on the closed chamber. 93 octane.

In addition, the curve on the closed chamber heads needed to be slowed down so it wouldn't be all in until 5000 engine rpm.

The open chamber was slowed also but was all in at about 3100rpm.

This is oppesed to my Boss quench heads and TRW pop up pistons running on Sunoco 260 that was all in by about 2,200rpm, 36 total, and if the city was going to bring back trollie trains, they would have hired me in that car to cut the grooves in the roads with the tires!

Those are my experiences and I do not claim to be the authority on this at all so there will be no pissing match challenges here by me.

I think Doug would be pretty right on this one.

Open chamber heads and domed pistons will create a crescent shaped combustion volume at TDC. That would require more time for combustion to propagate to the edges of the crescent shape therefore requiring and benefiting from more total ignition advance.

Quench chambers with flat top pistons will burn across the combustion volume fast. Therefore not needing and also not benefiting from more total ignition advance.

Total ignition advance is one of those things where more is not necessarily better. There is a point where excessive ignition advance even if it can be achieved without detonation will become detrimental to power production and past that point more advance will decrease power.

It has to be right for your own set up, not too much, not too little.

My personal preference would be the quench chamber heads and either flat top pistons or partially flat with partially dished pistons.

The engine doesn't seem to notice the difference between the two and feels crispy with both.

Static compression ratio of somewhere between about 9.7 and 10 seem to work fine and therefore pump premium gas is ok. No additives necessary.

Note also that I tried a dual duration pattern on the camshaft with greater duration on the exhaust.

This was recommended by the cam grinder as a way of blowing some of the compression out of the exhausts and fooling the engine into thinking it had a lower compression ratio.

In my case it did not work. Ultimately the compress-ability of the fuel without dieseling, is the determining factor. That is what the octane rating is after all. The higher the number, the higher the cylinder pressure it will take to make it detonate without spark.

I found the closed chamber Cleveland heads very sensitive to this. Seemingly no amount of additive I could put in was adequate to even reduce it.

It got so bad at one point that the engine would just shut itself off completely at about 4,200 rpm.

Currently I am running shaved A3 heads with dished pistons. Actual CR is 9.8:1. Runs great on 93 octane.

Open chamber heads would not be my choice to go with. Simply put, they are just too difficult to make work with this gas and any combination of piston dome configurations.

As AusFord says, it is a different engine with them. They lack the crisp response that the quench heads give.

Again, just my experiences with this engine series. Obviously, I did not try every possible configuration available and frankly, I'm done and this is what I am running and am SATISFIED with it.

As far as cowbells go, I didn't notice any. My engine is too loud.

quote:

Originally posted by Rocky:

NOTE: These specs are so different than what is shown in the link below, I am wondering if there is some "reference difference" that I am not comprehending...

The valve event timing on the cam card is based on duration at 0.050"; the valve event timing in my post is based on advertised duration. I calculated the specs for the cam on the cam card, based on advertised duration:

Intake lobe mathematic centerline = 108° ATDC
Exhaust lobe mathematic centerline = 116° BTDC
112° lobe separation angle (camshaft degrees)
Lobes: Symmetric
---------------------------------
Exhaust valve opening = 76.5° BBDC
Intake valve opening = 29.5° BTDC
54° overlap
Exhaust valve closing = 24.5° ATDC
Intake valve closing = 65.5° ABDC

When discussing valve event timing its customary to discuss "seated" valve events, which is why I use the advertised duration figures (0.006" tappet lift). However, there is merit in considering events at 0.050" when evaluating a camshaft because it takes into account how aggressive the cam lobes are, this is more important as the hydraulic intensity of cam lobes drops below about 60°.

For good drivability with 4V heads I like to see 0° overlap based on duration at 0.050, with the overlap centered around TDC. That means intake valve opens at 0° or later and the exhaust valve closes at 0° or earlier based on duration at 0.050. I also like to see the intake valve closing at 40° ABDC or earlier based on duration at 0.050.

The hydraulic intensity of the cam lobes used on the cam you've been recommended is 51°. Those have got to be Comp Cams Xtreme Energy lobes. I'd recommend using Comp Cam's Magnum lobes instead.

quote:

Xtreme Energy lobes. I'd recommend using Comp Cam's Magnum lobes instead

You guys must have been crime fighting detectives who were also engineers...

Maybe there is a TV show based on it... NCIS - Special Engines Unit.

Thanks, I will talk to the Cams guy.

Regards -

Rocky