2 heads better than 1 - power porting E7TE iron.

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Re: 2 heads better than 1 - power porting E7TE iron.

Post by digger » Thu Nov 22, 2018 4:20 am

David Vizard wrote:
Wed Nov 21, 2018 3:59 pm

As for the exhaust we can see the flow was gained at the expense of velocity.This indicates the port is too big and a more efficient but smaller CSA port needs to be sought after. That reduction on velocity means the scavenging effect is reduced and that can have a measurable effect on torque throughout the rpm range but more so at the low rpm used in street driving.
maybe i am missing something but how does the velocity graph falling show that the port is too big? i am talking generally speaking. For example if the port was way too small but it was efficient the velocity would still be high because its on a flow bench and the velocity on the flow bench is a more a function of efficiency but in an absolute sense it may be way too small from a CSA perspective and the velocity on the engine may be way too "choked".

it raises another question at what point (if any) is it just more important to get the CSA inline with what the engine wants and forego a bit of air speed on the flow bench in particular on a compromised port layout/design where it may not be possible to make it bigger and retain or improve the efficiency?

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Re: 2 heads better than 1 - power porting E7TE iron.

Post by jcisworthy » Thu Nov 22, 2018 8:11 am

Before grinding I initially measured the CSA of the intake runners and roughly determined I could, relatively safely, size them for an 1.840 valve max. I thought I turned down 1.940 valves to 1.900 but David mentioned that my heads had 1.94 valves so I may not have. It was a long time ago and I did not write down what I used on these heads. On the exhaust I just went with a 1.6 valve

I am confident the 1.84 valve would have made the same power or more and perhaps a smaller exhaust valve would work better. Without testing it is only guessing.
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by jcisworthy » Thu Nov 22, 2018 8:16 am

Even after grinding, the runners are small. The 347 CID will work better with a "larger runner" than the 306 but I do not think the iron heads can be made too big for either engine CID because of casting limitations
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by Carnut1 » Thu Nov 22, 2018 8:20 am

jcisworthy wrote:
Thu Nov 22, 2018 8:11 am
Before grinding I initially measured the CSA of the intake runners and roughly determined I could, relatively safely, size them for an 1.840 valve max. I thought I turned down 1.940 valves to 1.900 but David mentioned that my heads had 1.94 valves so I may not have. It was a long time ago and I did not write down what I used on these heads. On the exhaust I just went with a 1.6 valve

I am confident the 1.84 valve would have made the same power or more and perhaps a smaller exhaust valve would work better. Without testing it is only guessing.
Intake valves on John's heads measured 1.9"
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by David Vizard » Fri Nov 23, 2018 1:07 pm

68corvette wrote:
Thu Nov 22, 2018 1:44 am
Which of the heads had the biggest port energy?
I'm getting to that soon.
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by David Vizard » Sat Nov 24, 2018 7:15 am

Just so you have a better idea of this continuation my last post on the port velocity of the stock Vs RBJ Racing's ' production ported ' head ended with the following:-

The increase in torque due to better scavenging at O/L and ramming at the end of the induction stroke is due to the increased velocity and air mass involved. In other words the kinetic energy it contains that, when slowed by a resistance can be turned into a higher pressure energy to better fill the cylinders.

and now we have broached the seemingly touchy subject of port energy I will show what the difference is between a stock head and RBJ Johns modified head. I will also answer the question of whether the increased exhaust flow was of grater benefit the the loss of velocity a detriment. Watch out for the flack and my next post.



So now it is time to look at the changes the RBJ porting has made to stock when a comparison of the kinetic energy of the incoming and outgoing flows are made. what this will establish is whether or not the ports are more capable of producing extra power or not. the focuse here would be to question whether of not the extra flow on the RBJ exhaust is countered by the increase in CSA or not - lets find out!

Check out the IOP graph below.

In simple terms as the port energy goes up so does the functional effectiveness of it. As can be seen the intake took a huge leap in the right direction. As for the question of whether or not the exhaust has gained extra flow at the expense of velocity - well here is the answer. Although it could be higher the port energy is up throughout the lift range used. Bottom line - the exhaust, though compromised, will work better.
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by David Vizard » Sat Nov 24, 2018 7:41 am

Somebody remind me in case I forget but I was going to talk about the seat on the heads charlie and I did had seat forms optimized for sonic flow during the first 0.200 lift.
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by digger » Sat Nov 24, 2018 5:18 pm

so the RBJ head would have made more power with the stock exhaust port and just the inlet port modified??

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Re: 2 heads better than 1 - power porting E7TE iron.

Post by David Vizard » Sat Nov 24, 2018 5:32 pm

digger wrote:
Sat Nov 24, 2018 5:18 pm
so the RBJ head would have made more power with the stock exhaust port and just the inlet port modified??
No. Digger Ref the graph above.
The mass flow went up more than the CSA and as a result the port energy was up but not by as much as it could have been.

I will post a comparison of the RBJ head, which was deliberately done without recourse to using port energy as a reference, compared to the heads that Charlie and I did.

Johns work on that RBJ racing head was top notch. I am going to see if he will now apply his porting skills to do just one cylinder using port energy as a guide to what will work best.
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by digger » Sat Nov 24, 2018 6:01 pm

David Vizard wrote:
Sat Nov 24, 2018 5:32 pm
digger wrote:
Sat Nov 24, 2018 5:18 pm
so the RBJ head would have made more power with the stock exhaust port and just the inlet port modified??
No. Digger Ref the graph above.
The mass flow went up more than the CSA and as a result the port energy was up but not by as much as it could have been.

I will post a comparison of the RBJ head, which was deliberately done without recourse to using port energy as a reference, compared to the heads that Charlie and I did.

Johns work on that RBJ racing head was top notch. I am going to see if he will now apply his porting skills to do just one cylinder using port energy as a guide to what will work best.
DV
my bad, couldn't tell the diff between thick and thin :oops:

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Re: 2 heads better than 1 - power porting E7TE iron.

Post by David Vizard » Sun Nov 25, 2018 4:55 pm

I forgot to go into detail a while back about the exhaust seat that I do caters to S/S flow up to about 0.200 lift and after that It does not matter mostly because what the S/S flow needs and what the sub-sonic flow needs appear to be about identical.
The heads I ported for this test all have such for the exhaust ports. As far as I know Charlies ex. seats are very similar but he will enlighten you should that not be the case.
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by Carnut1 » Sun Nov 25, 2018 5:28 pm

Resized_20181125_172241_9858.jpeg
Similar but not the same. This is off my LS3 10 degree thread head. 1.6" valve that flows 280 cfm with a 50 degree seat and cuttered chamber and radius throat. Thanks, Charlie
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by David Vizard » Mon Nov 26, 2018 12:02 am

Charlie,

Your cutter work never creases to impress me.
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by David Vizard » Mon Nov 26, 2018 12:45 am

Here is the last of the comparison graphs of the RBJ racing and the stock E7TE heads.

The deductions that can be made from this Port Energy Density (or specific Energy) chart are:-

* The curves shown here allow us to quantify our efforts as we can now compare the results with any head no matter what type. For instance The intake port on the RBJ head reached 22.5 ft-lbs per square inch per foot of port length at the 0.25 valve dia. lift point (thick blue vertical line). mthe stock port , at it's 0.25 lift point (thin blue vertical line) only made it to 12.5 ft-lbs per square inch per ft.The RBJ head then was up 80% over stock and such a big increase would allow this port to better ram the cylinder. This would be very conducive to more torque which is just what we see from the power curve a few pages back.

* the exhaust specific energy took a down turn. Stock was better in this respect but it was just not big enough for the job.

So what kind of specific energy numbers do we need to see here. for instance what would a ProStock, cup car or a NA F1 engines curves look like? We can make a direct comparison with this info at hand and I will dig up some numbers from my F1 stuff.

Next move is to compare the RBJ head done with conventional techniques and the DV/CS head done with due reference to all these new factors as used in IOP.

DV
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Re: 2 heads better than 1 - power porting E7TE iron.

Post by David Vizard » Mon Nov 26, 2018 2:20 am

Well we have gone thru' the details of the RBJ modified E7TE heads.Let's now take a look at the differences that made the DV/CS ported heads using IOP to assist in porting decisions.
First the torque and power graphs. We will look at the flow bench results that show why the DV/CS heads showed so much better results.
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