Porting and polishing - $1500

I made a drawing to help show what I am trying to describe. This is 1977 2 valve US 308. I have two cars and both are the same on all 16 ports. Minimum offset is 1/16" inch, most are like 1/8" inch. Carb body bores are significantly smaller than manifold ports.

While I do understand that a flow bench would make the job simpler and more correct, I also understand that having these manifolds offset with steps such as this totally destroys any kind of reasonable flow. Flow bench or not this HAS to be corrected. This is what I meant about Luigi just grabbing parts out of a box. Now pretend the intake manifold is the exhaust header, and you can extrapolate how the the exhaust ports match the headers out of the same drawing.

What I would be curious to know, is if one should blend the manifold and cylinder head together, or, modify the manifold to match the head without touching the head. The gasket area is the smallest section of the port after entering the intake manifold, and after passing through, it opens up slightly before entering the valve pocket, creating sort of like a bottle neck. Blending the two together would open the port in that area making the port gradually decrease all the way to the pocket.
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If I were to entertain the thought of port matching I would build a rudimentary flow bench and then make a 1:1 model of one port (as per your drawing) including the carb and intake sections. Playing with matching the interfaces on the model(s) will then allow you to find the best shape before taking a grinder to actual real $$$ parts. Then you have to do the same for the exhaust and then you have to be sure that the overall flow from intake trumpet to exhaust tip is optimal for your purposes.

I doubt that anyone who has successfully done this is prepared to share the exact shape they arrived at. In essence it it their hard earned IP.

Some good sources for theory and practice:
Scientific Design of Exhaust and Intake Systems (Philip H. Smith, 1962)
The Sports Car Engine (Colin Campbell, 1968)
Power Plants for Aircraft (McGraw Hill, 1952)
Combustion Engine Processes (McGraw Hill, previously published as Internal Combustion Engines) initially published in 1915, major (6th) revision in 1968)
I haven't read these since the late sixties (when I was planning to build a continuous injection system for my Mk1 Sprite) but I recollect that they were very thorough and understandable on these topics. As a bonus they all date from the era of carburetors .


Gerrit

 

I would agree. If I were younger and or less experienced, on first glance at this I would make the argument Ferrari was pretty crude. But this is handwork, and because the parts are identically off equal amounts from both engines, I am forced to assume it is intentional. So the question then becomes why?

If Ferrari had ever any intention of racing these cars, or backing private entries, they knew from building the motors what the ports needed to look like. Making them like this would put private entries at a severe disadvantage. If we havnt figured out how to correct it in all these years, I would say Ferrari did a pretty good job.

Supposedly the GT/4 LM Michelotto car, that I believe was factory backed, used 208 cylinder heads. But there isnt enough information out there to make any real definitive conclusions. I am presently thinking that the intake ports in the head are maybe close to right, and modifying the intake manifolds to exactly match the head would be the least drastic alteration. Ants2au seems to had good results that actually improved low end power and he went even more drastic than this by doing actual blending.

 

Be very careful about making decisions on "it feels stronger". It's pretty to "feel" an improvement where none exists or you even did harm, but you feel what you expect to feel.

There is an add running on TV lately that plays to exactly that...some kind of air intake. They show a bunch of people in different trucks saying "list to the power, I can feel the rush" stuff. If there actually was an increase in power, they would quote the dyno numbers. What their product does is make the engine louder adding intake noise, so can hear the difference, and most people will also feel the difference that isn't there. Basically a placebo effect

 

if you 'deck' anything deck the block. flycut the heads to insure a straight flat surface and then you'll need to address the intake manifolds as the angle has now changed, most times those will be flycut also. as you shorten the deck you pull the heads closer to the block this will close the horizontal distance between the manifolds. so if you using carbs you wont have a problem with the carbs but with the cross over as the pipe is too long now. if it's FI then the upper manifold wont fit right.

basicly you need to account for the geometry. not hard if you pay attention.

 

Artvonnne,

My first inclination when I saw your diagram was to think it might be worth while adjusting the fitment or your intake manifolds by enlongating the intake manifold holes and sliding both intake manifolds over. But both manifolds would have to be off in the same direction and you would probably have to provide a locational feature like a couple of pins to keep everything in place. This is probably more trouble than it's worth. You'd still likely have to some port matching and things like retaining nut access become a problem.

I would think there's little risk in just doing some port matching here as I shown in the modified drawing. Proceed slowly and make a nice blend. Don't create any pockets, you only want to straighten out the flow. I would think the sharp corner on the head side is the most disruptive feature and will affect the flow more than the mismatch of the intake side, where a smaller opening transitions into a larger opening.



I'm inclined to not worry so much about the exhaust ports. If you want to treat the exhaust side in a similar manner, just remember the flow direction.
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I was begining to try shaping the first cars manifolds and intake ports, but I stopped and just put it on hold until I could get some idea what anyone might guess for a port size. Then I started looking at building a flow bench, which in turn turned the subject to space (where to keep it) and time (like where will I find more) and the whole thing ground to a halt. Then car number two came along and turned everything upside down.

I know a flow bench would offer a lot of information, but either way, flow bench or not, this area would have to be altered and made smooth as the starting point, either by blending the two ports together or modifying the manifold to match the head. It has to start in one of those two areas regardless. I am also of the opinion that the manifold should match the carb bore, not have it so much larger as it is now. I would imagine the flow bench coming into play after that work was done to try and get even more flow and try to equalise them. I say this simply because the way it is now shows no concern on behalf on the maker to how it flowed to begin with, and with one off a 1/16", and another off an 1/8", there is no port matching that exists in any way shape or form at present. Moving the pipe directly over the hole has to make it flow better than moving off center, no?

 

Yes it will. The step between the carb and the intake will also disrupt flow causing turbulance. This is not necessarily a bad thing as turbulance will likely cause the fuel/air mixture to mix better.

Interesting observation on a 2.0L Formula Ford engine. My builder found that by putting a step in the intake manifold to head gasket I could gain 5 BHP and he had dyno numbers to prove it (Basically, instead of a round to round hole between the intake and head, the steped gasket made it more like a half circle).

His theory was that the step allowed better mixing of the air/fuel, higher velocity (same volume, smaller hole) and there for better combustion and more power.

The 2.0L Ford had a Weber carb as well.
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Steps help a lot of engine believe it or not, and you see it on the flow bench as well as the dyno, so the air is SMOOTHER because of the step, not worse.

Almost every engine I've ported or seen ported, filling the bottom of the port makes the flow better. Tubes flow great in a straight line, but once a curve is added they aren't very good. Filling the inside of the radiusputs more of the air at the same velocity and greatly reduces tumbling that occurs due to centrifugal forces the air seems going around the curve. From personal experience, harley intake ports and 911 exhasut port benifit dramatically from this...like 20-30% and a big block ford I saw dynoed picked up about 5% with a gasket step like you did on your 2.0 ford.

If you want to match ports and don't want to flow bench it may help, it may not, is hard to say. You could try epoxying in the low side instead of grinding the high side...at least it reversible.

 

Russ, I never think it's a great idea to port without a flow bench, but if you're going to try....Kermit told me that he gets a 348 intake gasket and uses it as a template to change the figure-8 into an oval and it helps a lot. I'm pretty sure that is the right idea, but I would probably start by grinding the top of the port and filling the bottom of the port to prevent increasing port volume....but I'd do it on a flow bench.

 

I resurrected this particular thread as it seemed the most appropriate place to discuss this subject. I planned to build a flow bench over a year ago, but time got away from me. That, plus I had a alot of work to do researching the methodology of the whole process. Putting it together was simple. Engineering and designing it with an understanding of what I wanted it to do was the hard part.

The machine came about because I posed a simple question about the intake ports on 2V 308's, namely that none of the ones I currently have align with the intake manifolds. Some are offset as much as an 1/8th inch at the gasket/head interface. I suggested port matching them, and Russ suggested that the work should only be done on a flow bench so you could tell if you improved anything or just messed it up. Wildegroot, wanting to know the answer, sent me a one cylinder section of a 2V 308 head to experiment with. So with that section and my four loose heads, I presently had 17 combustion chambers and four intake manifolds to compare against each other.

Why does this thing look like this? Well, because everything I could find on the subject, and the room I had to work with told me to build it this way. Now I just have to figure out how to do accurate calculations and I should be able to start getting some answers.
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Good job! now go make some HP

I recently got a heavy duty electric die grinder (foredom 1/3 hp)with a speed foot pedal and cable drive to the hand piece....it awesome. I like it better than the air grinder because it's more controllable although it doesn't spin as fast it has plenty of power and I don't have to listen to the compressor running and using 15 times the electricity.

 

It is my understanding from a pretty good Ferrari engine man that the old two valve engines with FI benefit greatly from a P&P job. He says that those early FI heads were ported by Ferrari to help with emissions more than performance...

 

My biggest obstacle so far, has been the level of math and physics invlved. From all the designs ive seen around the internet, most dont really seem to be calculating flow with any true relationship to the science or math. The deeper I went, the more I seen that aerodynamics plays a very primary role in the calculations and engineering principles. And I SUCK at math.

But I built this as close to a scientific model as I could achieve, so if I get to the point where I can figure the math out better, the numbers I get should be pretty accurate. Fluid viscosity and density, Reynolds numbers, coefficients of flow, its pretty complicated stuff, at least for me, and it all seems to be required to get accurate flow numbers. But for now I should be able to get crude numbers with crude calculations and get some kind of % of difference port to port, as well as a % of change through alterations, that should be reasonably accurate. IOW, I should be able to chart changes with good accuracy.

 

All the hard stuff is built into the calculator I sent you
http://www.efunda.com/formulae/fluids/calc_orifice_flowmeter.cfm

use .62 for flow coefficient

The density you'll have to calculate or buy a meter.
http://www.barrygrant.com/bgfuel/default.aspx?page=76

Plug the numbers in and the right (of right enough) flow will come out.

 

Has anybody actually done extrusion honing?

http://www.gethoned.com/parts.php?get_price=yourparts&show=automotive

Those long intake runners on the TR are begging for an EH...

Rgds,
Vince

 

Okay, with my crash course in heavy math and science finally beginning to sink in, I finally felt comfortable making this stuff work, and flowed Will's single cylinder head chunk this morning. I built a crude tool to push the valve open with a screw and just ran two tests. I couldnt really pull more than 10 inches of water at this point, so I used that for my test pressure. At 7mm valve opening I found 79 CFM, and at 9mm it climbed to 85.3. I dont really know how that compares to anyone elses finding's, but I believe my numbers are accurate.

I dont have any kind of clay venturi around the port so that probably messes up the flow a bit. Im going to dig out an intake manifold and try that next, moving it in and out of alignment and see how it screws up flow. If I get it to work I will bolt a carb onto it to see what that does too. I believe the smaller 40 mm carb bore over the large 44 mm manifold bore would screw up air flow, so it will be interesting to see. But I sure would like to see 28 inches of water. Need a bigger vacuum.

 

Well Done!

The numbers sound pretty close, but maybe 6-8 cfm low and that would be due to the lack of stack of any kind. you'll see a big difference when you add one.

I do everything at 10" and have never seen anything to make me thing I had to go to 28. 28" is a more relavent test pressure on a US engine that will run with significant intake restrictions. If you prefer to see 28" numbers the 10" numbers can be easily converted and from what I've seen you will always get the calculated conversion number when you reflow at the new pressure.

 

Hmmmmm. I have tried this multiple times since this morning and I keep getting the same result. Without the intake manifold im consistantly getting 85.3 CFM, even though ive had to correct for air density changes the last few hours. With the manifold mounted to the head it will not flow any more than 83.8. Im still not using a venturi over the port, so not sure how that would improve things, but Im surprised there is a drop in flow. Whats facinating is how far out of alignment with the port I can move the manifold before there is any noticeable drop, almost 1/4 inch before the water moves on either manometer. Im going to hang a carb on it next and see what that does.

 

You always need an air horn of some kind at the inlet whether on the bare hear, top of the manifold or the top of the carb.

The manifold is a flow restriction, as is the carb so the flow will only go down as you add pieces. Now you understand tapered manifolds and big EFI TBs

 

Paul, it looks like you've done a lot of work there. Where did you get the design from or is it the product purely of your research. If not too much trouble, could you share any details? I am kind of interest in buying/making a similar device and could provide some comparison data. Heck.... we could all build them and compare notes!

I also suspect that for what you are doing, flow is like a dyno result. Comparison between different machines is not relevant, but comparison between different heads, before and after porting etc on your bench will be incredibly valuable to you (and hopefully us ).

As a final thought, maybe Mike or you could make a set of calibration tubes that could be used to standardize results across various benches....

 

Mark:

I applaud you on building your own, but the production version of this allows you to compare your results with others, which your will not accurately correlate. That may or may not make any difference.

As for the issues of a 2 valve engine, most Ferrari engines that I've seen, with 2 valves, appear that the distance between the valve seat and the bottom of the intake port is not enough. That would mean that the head is probably only breathing on the "top" half of the valve. The way that has been addressed is to "D" shape the port, with perhaps a little venturi action to pick the velocity up.

However, when it's all said and done, the biggest way to increase power on these motors is either a cam, or a pump. The cam allows more time, while the pump allows more pressure. Both can make more HP.

When we were running 2 valve Ducatis we ended up with ports that were about 3/4" higher than Ducati built them. When I was at the Isle of Man TT this year, I got to push around the Hailwood bike. My friend Steve Wynne had built it. When he ported the head, he put about 3/4" of material into the intake port, when the D shaped it, so we were probably very close to what he'd done.

Good luck on this project.

Art