Inliners International Forums General Discussion Engines Lump Ports in a Work Truck

Because of the low RPMs' in a truck motor (idle-3000) is there any advantage to installing lump ports?

Here is what I think I have learned about this.
#1. A 292 at 3,000 rpm @ 100% effencicy would pump 255cfm and 204 cfm @ 80% VE. A 250 at 3,000rpm @100% VE would pump 217 cfm and @80% VE 217 cfm.

#2. From what I've read and been told both heads flow in the 170 cfm range stock and both can handle 1.84" intakes with minor un-shrouding. Another source said a stock 194 head will flow 178 cfm.
The numbers on Tom's site I believe are for "open"port heads but we can be conservative and use them anyway. When he went to 1.84" intakes and removed the bosses flow at .500" was 195.6 cfm a 25.6 cfm gain and with lumps 215.6 cfm . A 20 cfm from adding the lump to a head with the bosses already removed. In the second test how much was valve size and how much boss removal? We may never know. Based on what I've read in the past I would say that at least 1/2 of that gain was from removing the bosses. Tom says there is no gain adding lumps to stock valves but he didn't say there was no gain by removing the bosses with stock valves. So my guess would be there might be a gain of up to 32.8 cfm gain with boss removal and lumps with stock valves as opposed to 45.6 cfm gain with big valves.
That would put us at 202.8 to 210.8 cfm with stock valves, no bosses, and lumps

So I think removing the bosses and adding lumps (or not) to either head would work for you. A 194 head will give you a little compression bump. Lumps? If you've got'em use'em. I'm still looking into valve shrouding.

Yes, But only with larger intake valves also.
Look at the dyno info at bottom of this page
https://www.12bolt.com/65279inline-cylinder-head-flow65279.html

Here's where I'm at now, I just got my 250 back from the machine shop and it's bored .030 over and decked .005, now the head is going in next, I'm planning on using some 1.94 intake valves if I can make them fit and seeing if I can use 1.6 exhaust. The cam I'm planning on using is 12Bolts HyTork kit and feeding it all with my 2bbl. Sniper fuel injection on either a Offenhauser or Clifford intake but definitely not the PES intake and using Cast Fenton headers. I'm not seeking performance per se but towing and not needing to exceed the suggested retail speed, The rear ratio is 3.08 and the transmission is a TH350 with a Gearvendors overdrive for an effective final ratio of 2.73:1.
Which is why I'm questioning if the Lump ports are going to be cost effective as the majority of engine use will be in the 2000-3000 range.

So I'm seeing 168 cfm in stock condition, add 25 cfm without the lumps or add 50 CFM more airflow with the lumps at .500 lift. The difference between the lump port and just the open chamber looks to be 10 lb/ft. of torque and 13 Hp.at 5000 rpm. Now at 3000 rpm the power and torque is negligible between lump port and open head, but both improve over the stock.

That TQ increase will be across the entire RPM range.
I might suggest using a 1.84 intake if you are more concerned with TQ.

I found this on page 90 in Leo's book describing a "Econoflow" head that Sissle marketed using stock size valves.

"The head bolt boss in the middle of the intake ports should be shaped like a wing, but left in place. Removing the boss will gain about 5 CFM on a stock valve size head, but the subsequent loss of velocity in the port will more than offset the gain."

This supports the the idea that removing the boss and adding lumps doesn't help without an increase in valve size. It may even hurt because of loss in velocity.

What we are trying to do with our truck engines seems to be kind of unique here. We are trying to make them a little better at what they were designed to do while others are trying to turn them into higher RPM hot street and race car engines. In some ways our job may be harder because they were very good at what they were designed to do.

What we want is over by the time data shows on Tom's dyno tests. By looking at the graphs it is clear that serious torque gains were made by the big valve head with the big cam both with and without lumps, good torque was produced across the RPM range tested, and the torque was already there at the beginning of the graphs 2.500 RPM.

What we don't see is what a cam designed to build torque and fuel economy would do from idle to 2,000 RPM with a stock valve head prepared like the Sissle "Econoflow" described above. For me any improvements here are the goal and it is cheap, basically stock valve train.

Rereading Leo's book and California Bills book again and Tom's dyno sheets with the idea of maximizing a low RPM high torque engine. I forgot about porting the dividers, dug out my Desk Top Dyno program but not sure it will help.

When I get into this kind of stuff I'm reminded of the description of the main character in the old Cowboy song "Yavapai Pete"...Not much of a thinker but more of a drinker...

I have read what I can find about the re-shaping of the boss because I think that is where low flow, Low RPM Torque will come from. The only descriptions I have found say "wing shape". Wings are rounded in the front, leading edge, and taper to the back edge. Not getting into how wings work by using difference in air pressure to create lift part of their job is the use the round front to push air above and below the wing and close it back together creating as little turbulence as possible. I have a book on aerodynamics that says the most aero shape in nature is a raindrop.

So to me it seems that the boss should be as raindrop shaped as possible, smooth and rounded in the front and tapered as thin as possible in the back. The object in to allow the air to flow as easily and evenly around the boss and curate as little turbulence in the back of the port as possible.

Rockets and bullets (especially boat tails) are pointy in the front and taper to the rear but have a blunt back. That is because that in where the moving force in applied and they can't be pointy in the back.

The footings on the Golden Gate bridge are pointy on both ends to split the flow and put it back together smoothly. This seems ideal if there is enough material and space but I'm afraid we could wind up with more of a port divider than we want if we add material.

One thing for sure is that these heads work pretty well at low RPM just the way they are and we don't want to make it worse. "Not much of a thinker....."

I for one am willing to give it a try and will go dig out my die grinders, if I was to think I believe this should increase the velocity thusly increasing the volume sent to the combustion chamber. Those pictures posted on the other post give me an idea where to start, maybe I need to dig out my cast rods to do some boss build up on the outside edge.

Gary, pm sent!

In wings, propellers. and wind turbine blades the leading edge is thicker and more rounded than the trailing edge. This may be because in all of these cases some sort of energy is being extracted from the air as it passes.

We are trying to allow the air to pass as easily as possible without removing any energy from it. The energy is being applied from the back side by the drastic drop in air pressure caused by the downward movement of the piston. In our case maybe a thin leading edge is more important since the flow is of a short duration and ends in the cylinder when the intake valve closes.

Maybe it is better to allow the flow to start easily against the sharp front edge and not worry about the turbulence between the back of the boss to the valve because there is going to be turbulence there caused by a lot of other things going on there that is much more serious than air flowing past the round back of the boss. ????????

We are also dealing with a head/port/valve combo that very nearly fits our need stock.

jalopy45

You can do something I did was I made them out of alum and bolted them in . It can be done one of two ways a small #8 allen thread locker to seal threads. Bolted to the face of the Boss (small flat spot milled flat) Or from the top of the head.