Swamp_Donkey

On my 98 12v I want to get twins. Probably using my hx40 for a 40/HT3B combo. I will be getting the head o-ringed as well.

The reason for me asking if porting is right for me is because of the cost/benifits. Obviously I am going after 500+hp. I can be swayed either way. My 98 is more for fun but my main goal for it will be some 1/4 mile passes. I have run high egt's before and I figure with the twins and my water/meth I got last year for christmas egt's won't be that bad in a 1/4 mile blast. Will the "extra" air that a ported head gives me make that much of a difference. Thinking of going with a stage 2 port job.

Air + Fuel = Power. Is the extra "air" worth the money for my power situation?

Thanks.
John.

joefarmer

Well, like you said, the advantage of porting and polishing is to improve airflow (you'll actually see less boost). Improving airflow allows you to run less EGT for a given amount of fuel. The amount of boost that you see is actually a measurement of how much restriction is present between the turbo and intake valve. How much boost it can handle isn't related to how much the head is ported.

There are a few different retailers that can port your stock 12v head. Piers, Schieds, Haisley and DonM are a few that come to mind. On a direct comparison with the same turbos, fuel pump and injectors, Piers 24v head work produced ~5psi more restriction than DonM's. This indicated to me that Don's head flowed a little more than Piers. The EGT's were roughly 20F less with Don's head, but that could just be the differences in gauges.

The stock 12v head flows alot less than the stock 24v head. If I had the money, I think it's a sound investment for a 12v. You can still make 500hp easily without porting, but a ported 12v should run cooler, last longer and flow better altogether.

All in my own opinion,
bradnon.

600 Megawatts

You can do it yourself.... Got a nice air die grinder and air compressor, or better yet, an electric die grinder with speed control?

First, do some reading. David Vizard has a nice book out there on head porting a small block Chevy. Some of the specific areas and techniques he mentions will obviously not necessarily apply to your cummins port, but the majority of the flow patterns and areas of typical trouble will be the same. This book also gives you a neat way to crudely use a shop vacuum as a flow bench. And there are some articles on the internet specific to porting a cummins 5.9 head I recall seeing a couple of years ago.

Second, buy some very good long shank carbide deburring cutters. Unfortunately figure on close to $20 each for the long shank ones. I recommend one with a 6" shank, 3/8" oval head, and another 3/8" oval head one with about 4" of shank, plus your basic 2" shank 3/8" oval head. In all cases I do 99% of my porting with oval head cutters. I mention the speed control on the electric die grinder as necessary because you cant spin the long shank ones at full speed, they tend to whip and vibrate the tool right out of your hands….

Third, have at it!!!!! If all your are looking for is a nice 15% or 20% flow improvement, you wont be removing much material at all, just some material in key places, so you should not be getting into trouble breaking through the casting. Here is a hint, the port openings on the faces where the manifolds bolt to the head is the LAST place to worry about. Well over 80% of the restriction in most any engine cylinder head is the valve and valve seat area. Work to blend the seat area and bowl will pay massive dividends with very little material removal. Also, 'polishing' is a complete waste of time.


KP

TRCM

Huh...polishing the heads on my 360 gas engine netted over 20 more cfm....but yer right, it isn't worth it.

BTW, every cfm added is potentially worth 2.2 hp.

cummnz4x4pwr

And if your planning on doin it ur self then you need to go to www.piersdiesel.com they have pictures that show what needs to ground down and what not to touch. its in the techinical menu

FWIW
Jake

RCW

Definitely do the porting. The #1 exhaust has a serious shrouding problem in the 12 valve, and once you open one up you will not believe the difference it will make. Better yet, talk to Piers and try for one of the ported and o-ringed first gen HD style heads that fit the later 12 valve engine.

600 Megawatts

TRCM, polishing to a smooth finish IS total nonsense. You found your 20 cfm from something else or flowbench error, you can take that to the bank for sure. Perhaps you are getting porting and polishing confused. Unfortunately the phrase 'ported and polished' goes back years and people dont realize they are two different things. And the ONLY thing that should be polished is the combustion chamber of a gaseer and the beams of connecting rods. Polishing intake and exhaust runners yields absoultely zero cfm increase due to the fact that you have boundary layer flow in ports.

And your 2.2 HP per cfm number does not hold any water at all either. There are hundreds of other factors that play in, not the least of which is the amount the engine was restricted in the first place. Sorry, to argue with you, but this is an area with which I am extremely familiar.


KP

Swamp_Donkey

I may do the head porting myself. I have done some porting on some 440 heads with a kit I bought from mopar performance. I actually enjoyed it and I think I did a good job.

I did talk to Mark @ PDR, that is why I am asking if I need the porting. It seemed like alot of money for the porting. But I guess it can only be done by hand and having someone sit and port a head for 10 or 15 hours or whatever it takes along with the expertise does not come cheap. It is not that I don't want to pay for the port job, I am still on the fence as to if it is something I need.

What got me making the first call was the 12v heads on sale at PDR. So I want twins so this new head on sale will get o-ringed and then maybe a stage 2 port job and all the other bells and whistles. With all the bells and whistles it will cost around 4 times more than the head that is on sale! That makes a cheap Scotsman like me bunch up in some funny places!

600 Megawatts

Well, I would say that some amount porting is ALLWAYS good. Buy that head on sale, and work the bowl area yourself. If you should ever be in the Pittsburgh, PA area you are welcome to bring the head over my place for before and after flowbench tests too. It would be a crying shame to build a setup like that and not have the head ported. If the head is ever off my cummins, it WILL be ported thats for sure.


KP

TRCM

Well, I guess the pros and powers that be who have tested and proven the 2.2 hp/cfm rule numerous times don't know what they are doing. I have seen it bear true 90% of the time on engines that were dynoed before and after the heads were worked. The ratio is not as high for an all out race engine tho, more like 1.3 - 1, but for a normal street driven N/A engines, it is very close (which involves the amount of restriction intially).

I also guess that the people I have helped port heads/build engines for, and whom I have discussed engine building at length with, who are making anywhere from 500 to 1100 + HP (W/O drugs) think I have no clue either (these do include a very famous monster truck, and some overseas offroad racing champions, as well as numerous local champions - straight line and roundy-round).

And yes, porting and polishing are 2 different things.

And no, the increase I obtained was from merely polishing the walls some - not mirror polished - but smoothed out more than a normal port job would see. No metal was really removed. It was tried as an experiment because of the flow depressions found from probing the port on the flow bench.

You try all kind of things to see what will work when the port shape restricts you to normal methodology (pushrod holes, water jackets, head bolts, port shape itself, etc, etc).

No error in the flow bench either.

Polishing the combustion chambers is generally a waste of time on anything but a race engine. Street driven engines won't benefit enough to make it worth the effort or cost. Normally, polishing the runners does very little to help, but sometimes, it helps a lot. It all depends on what the port wants/needs to move the air.

I HAVE found that people who say something is absolute, like polishing is a waste of time, are usually the ones who are unwilling to experiment. The polishing was tried because nothing else was working well, so we figured what the heck...and it worked.

I never said the cfm/hp thumbrule was 100 % true all the time, but that it does apply more often than not.

I know I, and the others I know who port heads try all kind of things to see what works. We don't assume we know exactly what it will take to make the head flow until we flow it and see what the port wants/needs.

600 Megawatts

TRCM, lets just agree to disagree, BIGTIME. But don't try to suggest that I don’t experiment. I have spent more time porting, testing, welding and flowing than I care to recall. I went through over 20 sets of 441 casting SBC heads plus tons of 041 and 461 heads and have tried anything you can imagine in terms of port shape, style, bias, valve seats, guide boss shape you name it..... Trust me polishing does nothing, and the fluid dynamic theory is there to explain why; its a result of boundary layer flow, period.

My 355 in^3 NHRA Super Stock drag engine makes 575 HP with 9:1 compression flat tops, 1969 Chevy 76cc chamber iron 441-casting heads with 1.94" intake valves and 1.5" exhaust valves, stock intake and exhaust runner volumes (ie: every cc you remove somewhere needs welded back elsewhere in the port) and a 730 cfm quadrajet on gasoline and no drugs. And it aint just peaky HP either, is enough to push my 3,320 # Camaro to 10.teens at 130+ and carry the front wheels high in the air for 50 to 70 feet of track using a powerglide two speed transmission. And I am not bragging, because the fastest car with this combo has 590 HP, and he has gone 9.98 so I'm a bit behind..... But please do not suggest that I don’t know what I am doing and that I don’t experiment on the flowbench, dyno and track.

In closing, I must question the 'pros and powers to be' that you have been associated with who claim that polishing the walls of an intake port gave you 20 cfm.... I respectfully suggest that it sounds like you have been snookered..

All of this, with no disrespect intended, and in the spirit of technical discussions on the forum.

KP

HOHN

Not to egg this one, but KP is right on.

A coarse finish (say 60 grit or so) is what you want in the intake tract and chambers. By making the boundary layer more turbulent (like the dimples on a golf ball) you reduce the boundary layer's thickness, recuding friction drag from the surface acting on the flowstream. Also, the combustion chamber and such will soon have a coating of carbon, so the point of the polishing is defeated.

Polishing is bad any place you have a wet flowstream, as it makes the flow more prone to "wet out", which is a HUGE impediment to power production and efficiency.

Remember smokey's "hot vapor" engine?

A turbulized boundary layer is old, proven technology, used not only on golf *****, but F-105 and F-15 intakes.

Don't put to much stock in pressure depression readings taken on a flowbench. The act of inserting the probe into the port sufficiently disturbs flow to where, imo, the data from such measurements is of questionable value.

jmo

TRCM

600 Megawatts:
I didn't say the 'pros & powers that be' are people I have associated with. I did say some of the people I have been associated with have agreed that is is a fairly accurate thumbrule. But again, a thumbrule is just a guide, and is rarely dead nuts on all the time.

I also agreed with you that normally, polishing doesn't help. It did on my engine's heads for some reason. And no snookering..I operated the dang flow bench myself (yes, I know what I am doing also).

'They' didn't claim the polishing work added 20 cfm, but it did. 'They' said they didn't think it would help, but it did. Every one of them said it shouldn't have worked, but it did (it was on the exhaust ports BTW). All I said is that on my heads, it added that amount (well actually, it was an average 19.7 cfm gain across 8 cylinders), not that it would on all heads.

I also said that 'every cfm is POTENTIALLY worth 2.2 hp, not that every cfm is. Just like a 100 hp nitrous jet is worth potentially 100 hp....but sometimes it is only worth 75, and sometimes it is worth 125 hp.

Are we talking about turbulent boundary layer flow, or laminar ?? They both have the goods & bads, and every runer wal has both. The difference is in how thick each is with respect to each other.

I know what physics and all them fancy laws say.....I also know that according to physics, putting bb's in the tires of my 4x4 shouldn't balance the tires, but it does...very well indeed it does.

And despite your knowledge, if anyone - and I mean anyone - says something is absolute and never works, it makes me doubt their knowledge or willingness to test & try things that are different.

We can agree to disagree....it won't hurt my feelings one little bit. I just took offense to the "it never works" part of your statement.

And HOHN:
The probe can and does do as you say, but that is why you have to probe all areas of the port, not just certain spots. That way you see how much of a depression it causes everywhere......if it drops 1" at the middle of the port, but 3" at the wall, then it's a good bet that there is a 2" difference between the wall and the middle if the probe ain't there.

And yes, on the intake side, you don't want a polished surface if there is wet flow. Mine weren't polished (see above), but may well soon be, as I am in the process of switching from a carb (carbs don't do well at 45 deg + angles), to a custom port FI setup or propane once I make up my mind which way I am gonna go.

HOHN

That FI or pro-pain (hehe) setup sounds fun.

Correct me if I'm wrong, but won't the pressure drop vary with CFM? What flowrate are you using to test the head? I'd expect a higher CFM to have greater pressure differences as you probe the head.

Also, as velocity changes, it changes the part of the port that most affects flow. Like on the F-16 intakes. They are designed so that it's an efficient intake at 200mph and at 1500mph. That's because different parts of the intake become more important at different speeds.

Same is true of supersonic boom cones. As you know, a supersonic aircraft generates a sonic boom in a cone-shaped pattern that spreads out behind the aircraft. But the ANGLE of this cone changes as you go faster. IOW-- the shape of the boom cone is quite different at mach 5 than at Mach 1.5. (narrower, actually).

It's like a boat wake. Your boat goes "supersonic" when it travels faster than the waves it makes travelling to the front of the boat (about 3-5mph). After that speed, you'll see a cone shaped wake behind tyhe boat, and it's interesting to see how it's different at 20mph compared to 50mph.

TRCM

Yes, the pressure drop varies with cfm. That is why you adjust the machine to obtain 28" depression. As you do, the flow will go up, but since you arre always adjusting to 28" depression, the readings are consistent.

You don't really test the head at different flowrates, but at different valve lifts. As the lift goes up, the flow passed will go up (hopefully), and you must change the range of flowbench to keep the readings within band.

IE: on my heads, we used 3 different flow ranges, and measured the flow at .100, .200, .300, .400, .500, and .550 inches of valve lift.

And as for diff parts being more important at diff speeds...yep !! Valve seat angle and any back cuts are pretty important at low lift, but have a miniscule effect at high lifts.

A properly designed/ported head will flow basically the same air with the valve in it as without too.


Still not sure on the FI vs propane yet. The propane setup is cheaper, but yields less HP unless the engine is built specifically for it. But if you have the shiny side down, with propane, you don't have to worry about getting wet with stuff that burns very well. It is also harder to find a propane filling station where I wheel, as compared to a gas station.