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Cylinder Head and Camshaft Comparison.

Well this platform has always had nothing but opinions, ALL based on a butt feeling, and speculation etc.. We both want to know what works and what doesn't, not only to sell something but to have personal knowledge..

There is so much talk on social media and forums about this and that, to show real data is where I want to move towards...
 
Chris, It usually is the journey that ends up being more important than the destination!
Congratulations on the retirement countdown! My bucket list is growing but 22 years of spinning wrenches still awaits me.
I agree with needing more than butt dyno analysis. I promise to share results when I can command lockup in drive. I also promise the results won't be impressive to you guys!
 
Its a big time and money investment to properly test everything that we have discussed on this thread and others. Swapping one part and a time and recording the results. Trying different combinations of parts. Its hard to afford all that unless you have a personal dyno. The only person I know currently doing any good real world testing is Quadstar and Banghart on their project together. They are data logging it with a Banks I-dash along with the chassis dyno. But I doubt we will see John share alot of that. I dont see a guy who hides out on his own private Facebook group page sharing much with anyone else...
 
Speculation isn’t the right answer, but some stuff shouldn’t need a ton more than theory to show helpful.
Unshrouding helps volume flow and speed. So does smooth (even up to polish) finish and since we are dry, no issues of taking fuel out of suspension or coalescing droplets onto walls. Keeping oil buildup off the runners is good, but could the same results be accomplished by the epoxy or ceramic coating trick that is used for oil return in the crankcase area? As in just paint and not die grinder work to smooth and polish?

Dimpling is very expensive and the rate it speeds up surely (imo) wouldn’t be worth it unless someone owned the cnc and could waste so many hours of there free time.

Something to think about: in using the added boost to replace the larger porting size is true, but simply the faster that fancy fan blade spins, the faster the air coming out of it is. So how much of it is increasing air speed vs volume? Our friend Boyle has something to say about it me thinks. Anything to get that 50 inches filled to the desired max quicker is the name of the game.

Doing one long block with one turbo will prove out compared heads- but different turbo that spools faster like 35/40 hybrid vs hx40 means it doesn’t need as much exhaust drive pressure to spool up- so bigger exhaust ports would win just between those two because easier breathing turbo so long as it is maxing required force to get up to speed. So the ‘best’ heads with gm8 and stock manifolds will differ greatly than hx40, or even hx40 but headers instead of manifolds because of the speed is made up there.

Headers and intake manifolds are SO massive in both n/a and turbo gasser builds that its amazing. But, that is yet another round of dyno tests needed to show dollar to power value. Those cnc pipe benders sure are cool...


Something an engineer buddy of mine said years ago- valve opening and closing along with the change in cylinder size while getting filled and when dumping... He wanted to do flow testing using a dummy cylinder and piston. Basically how well does your garden hose put out water vs when you are kinking the hose fully shut for a moment repeatedly. The shock wave and how the cylinders interact is all done theoretical.

It has been many a day since i looked at dyno cost- but used to be an engine dyno was way cheaper than rollers set up. Also gives a lot more accurate readings. Most shops go with rollers because they can recover costs easier by charging to use a couple hours at a time rather than 2 a day at best doing engines. Has that flipped?
 
No it hasn't flipped.. The recovery of moneys would be faster when you can back a truck up and make a coulpe pulls, swapping parts or motors not so easy..

The upfront cost of a dyno is just the start, setup, air flow in & out of the room, temp control in the room, and so on...

Chassis dynos are notorious for being easy to skew the numbers, simple file manipulation after the fact, easier to sell your products, and I'm NOT saying that any of our vendors would or have done that, NOT GOING THERE !!!!!!
I just prefer engine dynos, better to duplicate every pull... I'm all for collecting data, I'm no pro in the electronic area, I don't know how to do 99% of that kind of thing nor how to read it..

As most know, I don't sell anything but a service, other than GEP factory stuff, anything I do can be found elsewhere, I do what I do for my learning, and when I decide to quit working on heads folks can figure it out themself..
 
I still disagree that the exhaust ports need any work at our power levels. The 6.5 (non p400) heads ratio at 30 between the ports. The lb7 is at 34. Going off just cfm numbers the 6.5 heads dont appear to be a bad as I've been lead to believe. Both v8 diesel engines with very similar displacement.

I think opening up the ports and adding a bigger turbo is just a combination for a lazy spool time. Especially if you keep the horrible factory open exhaust system. Think about it why does a smaller turbo spool faster.... its smaller so the air velocity is faster though it. So it drives the turbine faster. Physical size plays a part too.

The exhaust system also comes into play too. Even though a v8 doesn't balance the bank firing order like a I4 or I6 engine. The factory open exhaust housing is a great spot to lose air velocity. A divided system would probably make a huge difference on how a bigger turbo spools by eliminating that air velocity loss.

If your power goals require a very large turbo then I could see opening the ports to support the extra air flow thats needed. But I'm talking like a 1.10 or higher A/R. Which would be useless on a street truck. I think we all can agree that you need to match your heads to the turbo for the operating range and power levels your after.


My only issues with correct factors are they don't necessarily apply to a turbo engine. Your adjusting based on things like barometric pressure, temperature, humidity ect... but a turbo engine doesn't rely on barometric pressure to fill the cylinders. Manifold pressure is more constant at different altitudes because of that.
 
I am tracking with ya, but in second paragraph you ended w/ the caveat -Physical size plays a part too.
That seems to me to have a bigger impact. It gives me flashback to my sbc/bbc days. Couple of buddies and I were arguing out mouse vs rat and 400cid is a magical place. Slight opening of a 396 and the 400 small bock both built the same. We made bore and stroke the same, valve size, etc. The weight of the big block made it loose quite noticeably. It simply couldn’t rev as quick. The torque and hp numbers were so close and nearly same graphs. it was the same practical engine, except 750rpm to 5500 rpm was quicker. 2.5-3 tenths off 1/4 mile nearest we figured.

So the few grams extra and the extra drag created by the extra air moving on its way to 10,000 rpm is really a lot.

I see the exiting velocity as very important in a boosted engine because of lag - but I think proper sized headers would have far more impact. It sure makes a moneter difference in every other application I have seen. 25 ponies is not a lot but thats 10%- and n/a gassers the rule of thumb was 25. On dmax, the bigger 3” Y bridge is good for 30 hp if you already did the rest of the system. 6.5 obviously not the same, but still.

so
 
I was hoping someone would go to the link and do the calculation using the numbers i provided and post there findings, I'm very rusty on the new fangled symbols used these days...
 
Twisted Steel Performance said:
I was hoping someone would go to the link and do the calculation using the numbers i provided and post there findings, I'm very rusty on the new fangled symbols used these days...
Click to expand...


I completely forgot about this. I will try and sit down this weekend and do this. I've been preoccupied with getting my injection pump test bench ready for summer.
 
Zombie thread flash-back.
Any new input? Being as I am doing centermount- I am trying to figure out a log looking header. Basically headers that have the collector at the rear.
Soon to hassle @n8in8or about his header info he learned …

On my p400 heads
I am leaning strong on only smooching the rough surfaces on my intake ports,
Still fighting what to do on the exhaust.
Trying to find a bank to rob for roller rockers & my turbo (yet to be determined)
 
dbrannon79 said:
I really wish GM and or AMG would have designed the heads for the 6.2/6.5 to be like the SBC gassers with a stud for each rocker. things would be so much easier for us.
Click to expand...
I have wished it before. If a feller can do the roller rockers- that design we have is now the most desirable one on shafts. A better design is the type that are adjustable like the sbc- but since our lifters have the way better design - it really isn’t needed.
The only advantage of the sbc as far as valve train is the fact that millions made so parts are cheaper. We have roller lifters with solid designed retaining. Our push rods could be stronger but really not needed until a guy builds really high pressure.
The plastic retainers that are in the rocker arms is cheap- a threaded hole and steel bolt with bronze bushing would have been better. But jumping to the roller rockers solves the weak points there. Gm we t cheap on valve springs and should have beefed them up with addition of the turbo, but again not needed until a guy bumps up the power.

As to the sbc- i wish the 6.5 copied the timing cover separate from the water pump more.
 
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