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Cylinder Head and Camshaft Comparison.

Air flow is air flow. I get what your saying about wet flow bench. But at the end of the day the head flow CFM on a NA engine determines its power potential

You are completely missing the point that on a turbocharged engine the turbo is responsible for thr airflow into the engine. You are basically making your own atmosphere at that point. For example if a turbo is pushing 1000cfm it doesn't matter if the heads flow 200cfm or 250cfm The same 1000 cfm is making it into the engine. The only difference is boost level will differ due to the difference in head flow rate. I dont care if you heads flow 300cfm. THE SAME 1000CFM is making it into the engine. Your overlooking how a turbo engine gets its air supply. Think I've made that clear in my last three post.

My whole point is flow rates don't matter much anyway on a turbo engine so who cares if the math we are using for head flow to HP its 100% accurate. Nothing ever is, but its a good baseline.
 
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No , I'm not missing the point about the turbo . You have a good theory , now prove it .
 
Not really a theory.... plenty of articles state similar things written by people who know more on the subject than myself. This is another good one. I quoted the important part below.

https://www.enginebuildermag.com/20...upercharging-just-discovering-true-potential/

"When building a turbo engine, one of the most common mistakes made is the wrong choice of cylinder head. For some reason or another, it is assumed that since you are going to be forcing air into the cylinders you need a huge intake port. Another misconception is when building for alcohol instead of racing gas. The pattern of thinking among some builders is that you are trying to move more air (especially if using alcohol because you use twice as much fuel compared to gasoline), so you better use a larger port size.

True, port size and valve area dictate how much cfm the cylinder head is capable of. But, the fact is cfm relates to how many cubic inches can be fed. An engine runs and makes power on the premise of the equation of lbs./hr. of air, which translates to density, not cfm. A turbocharged engine is going to consume the same amount of air, but it will be more dense.

Another common mistake is the size of the exhaust ports. The common practice is to use a cylinder head with a larger exhaust port. Actually the cylinder head of choice is one with small exhaust ports. People relate the exhaust port to the intake port thinking that what goes in must come out. In turbo applications, the use of smaller exhaust ports actually help in propelling the turbo. Since the turbo is exhaust driven think of it as a pulse generator. Exhaust pulses leave the cylinder head and travel in the header pipe to spin the turbine wheel. The use of bigger exhaust ports causes the exhaust gas to lose velocity, reducing the effect on the turbine wheel. Proper header size and firing order sequence help maximize turbo efficiency."

Like I said port velocity is more important than CFM. Especially if you want good spool time on a bigger single. If you flow guy is just focused on CFM... then you need a new head guy 😉
 
One of you do the calculation in the link below and post up your figures so I can see if I figured it correctly ... I'll post the measurements of my head with bigger valves tomorrow, but for now use the stock measurements... use 1.5 & 1.6 & 1.7 ratio rockers...

www.feoa.net

How to calculate camshaft maximum lift for a valve

www.feoa.net www.feoa.net
 
Since it seems that the numbers for head flow and cam timing are at least in the ballpark with most of the other diesel truck engines out there, maybe once the compression is lowered to even the playing field the only factors holding back the 6.5 versus the competition are how much fuel a rotary pump can deliver and how much boost and drive pressure the block and rotating assembly can take.

A p400 with studs, o-rings, and a 200+ cc pump could, in theory, be very impressive.
 
Chris , I have heard of the Delta cams and thought there was one larger than the 206 . It would be interesting to get the specs on that cam . Also need the radius of the seat and not the valve for the formula .

As far as the intake ports , where are the specs on diesel porting ? No more on gas or alcohol , just diesel . Where are they ?
 
Their is a delta 202, nothing with more than 206 duration that I know of, I have specs for almost all the older grinds like the crane that isn't around anymore...
I don't know of specs per say posted anywhere, there are a couple larger builders here that do diesels I talk to, they don't run "one large" turbo, they use compounds or vgt's, I sort of take some head Q's from them even tho they don't do the 6.5, but they do build some wicked 7.3 idi's, and they "say" porting is needed... I don't know for sure, I don't have hard data one way or the other...
 
It's hard to find porting info on a 2 valve diesel heads. Everything is 4 valve DI today and they design the ports specifically to create a swirl as it enters the combustion chamber. Very different from our heads. The 12 valve or 7.3 are your best bet to find technical info on porting a 2 valve diesel head.

Here is one one modern diesel heads. They do mention keeping the exhaust size small for port velocity.

https://www.enginebuildermag.com/2018/02/porting-strategies-diesel-cylinder-head-performance/
 
Here are the measurements

Stock head
IN - 1.605 - stem - .341
EX - 1.285 - stem - .371


Other head
IN - 1.765 - stem - .341
EX - 1.440 - stem - .371


I have no idea just how accurate this calculation is, I know my cam guy asked for these measurements as well as many more, so maybe there is something to it..

My thinking towards the whole idea behind the 6.x motor, or heads as this is the conversion here, one could guess the engineering that went into the head design is old and maybe centered around fuel economy, emissions, etc, not any kind of performance, so maybe just maybe something can be improved upon...
 
Yep , my thinking too . Not really worried about other points of view as I've heard this over and over again . I have my thoughts and that's why I had my heads ported and picked up the Crane regrind . Could I be wrong ? Sure but it's my money and time and I might just learn something .

I think the formula wants the seat dia not the valve .
 
No factory heads are designed with performance in mind. They have to meet emissions and MPG standards. But if we are just talking CFM and ignoring every other detail about head ports. Then the 6.5 and lb7 head are extremely close CFM wise. I have plenty of customers with 500-600hp lb7 on stock heads.

At the end of the day unless we do side by side dyno runs and data logging on the same engine with different heads. We won't know if it makes a differences or not. For me I see no reason to open the ports. Our heads support 370hp NA. I can't see why you need to open ports to handle the additional 80hp worth of air im going to need for my power goals (450hp) .

Sure we can get 200cc out of a db2. But to do so it requires the timing to be locked, and a solid billet input shaft to handle the extreme load the large plungers create. CDD has a pile of broken input shafts from getting the .370 to live. A pump like that is awesome for racing. But I'm unsure it's drivability and longevity for a street driven truck. Wes builds awesome pumps. But the added stress of a the big bore pumps could lead to premature wear. So my point to this is if you want a 600hp with a big db2 then I could see head work being beneficial. But it maybe useless on the street or for towing. But as for me keeping the pump in the 150cc range I can keep my dynamic timing, not over stress the pump. And drive it everyday to work.
 
Two of my old employers have a dyno. And there is a speed shop in the other industrial park way by my current work. I'm going to reach out to one of them for some dyno time when my truck is up and running. But thats going to be 2022 more than likely

Really wish I could find a engine dyno to run on tho. That would be awesome for head, precup, and other test im itching to do.
 
Unique Diesel has one but it's not up and going yet, the cost of doing a dyno room right is costly, and the dyno itself wasn't cheap, but it is what is needed for a turbo diesel engine..

There are several engine dynos here but none will do a turbo diesel, they claim it takes a dyno designed for a turbo diesel's low rpm high torque...
 
Thats exciting stuff! It will be awesome to test everything and finally have real evidence of performance gains instead of guessing like we do now.

I have some fuel system stuff im going to be testing this summer on my test bench once its up and running. The lab scope is coming out for this😉
 
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