Most of the post I have read in the past imply that porting the heads is a waste of money. I was wondering if anyone has done this recently with any track or Dyno numbers to show their results??

Thanks
Rob

 

A few have done it and reported good results. JL sells them, I know JDM has someone who does it, not sure about Sal but I'm sure he offers that service to.

IMO it's definately something to look into and next on my list of mods.

 

hmm i gotta a nhra motor builder and machinest buddy that would do it for free for me, so im seriously looking into porting, but i dont want to put him through having to go through all that trouble if its not going to do me any good. so let me know if anyone has any good results.

thanks
gaven

 

The results aren't huge but never the less the engine does respond to it. I had mine done by a guy who knows what he is doing. He probably spent close to 2 months in his spare time on and off the flow bench. Found out it is not an easy cylinder head to find flow gains on. The intake ports are the toughest. After all the work, we only found gains from .400 lift on up.

The exhaust ports were different.....the gains there were huge.
On Johns bench the exhaust flowed roughly 138 to 142 cfm at 28" h20 stock....after the work they came in at 180 cfm all at .500 lift and 28" h20.

If you get a really good port job on the exhaust side, you will notice that the engine doesnt hold heat like it did when it was stock.
Its a lot less sensitive to octane and it won't require super cold plugs anymore. Also the engine will be noticeably louder with the same mufflers. The exhaust restriction on a Lightning engine starts right at the exhaust valve.

My intake ports pretty much flow like stock up until the curve hits .400 lift then theytake off. At .500 lift the ports are almost 25cfm better than stock. But with stock cams that doesn't offer much improvement.

A rule of thumb I read a long time ago went somthing like this.
Flow gains that are made on the intake side of a cylinder head will have 25 times more of an effect on HP that flow gains made on the exhaust side. This was out of a book written by David Vizard.

I would have to summarize by saying that a well ported PI cylinder head will give a descent HP increase but most of all "IF" the exhaust ports are right, the engine wont hold near as much heat as it did when it was stock and will make tuning much much easier.

Disclaimer:.......I dont race flow benches and I know there are guys out there claiming 250 + cfm on the intake and well over 200cfm on the exhaust. So be it. I'm more than happy with what I got. And I believe the numbers that I got.

You have to remember that the intake valve is only 1 3/4" dia. and the exhaust valve isn't even 1 1/2" So please dont quote numbers that a small block race head couldn't match.
Dale

 

Interesting information Dale. Did you go with oversize valves? Makes me wonder if the stock heads are part of the reason you see less than average gains with headers (relative to other forced induction motors)? Also may explain why the relatively small primary tube of 1 5/8" tube seems to be the most effective on our motors. I would think motors of our displacement putting out 400+ rwhp would have needed a 1 3/4" or even 1 7/8" primary.

There are rumors that Edelbrock will be coming out with an aftermarket head early next year. I am holding out for an aftermarket head. Just think of all the new tuning that will take place if a new head comes out that flows like a high performance head should. The heads may also be the key to finally allowing aftermarket cams to do their thing. I wold like a little more lump in my idle .

 

I need to type up a standard reply to any of these questions to save some typing

The reason you don't see much is becuase with the type of supercharger you have, the blower is supplying some amount of air independent of downstream changes. Its physics and you'll just have to believe me. There's posts in the past going through the math that you can find on a search. So porting the heads, changing cams, headers, exhausts, etc. don't do hardly anything for overall engine airflow. With such small changes in airflow, there are small changes in power.

Now if you were turbo'd or had a centrifugal blower, there would probably be huge results from those same changes.

It is interesting to hear about this. When you decrease the exhaust restriction, you're not really holding in less heat. What you doing is allowing more of the burned gases to make it out of the cylinder. The mass left in the cylinder is called residual mass or internal EGR. The blower doesn't care how much is left in, it will just add its own on top of it. But if you can get more out, then you are starting with a cooler, lower pressure charge, which in turn lowers the detonation risk (and gives you the benifit of being able to run more timing, hotter plugs, and such).

But in the end, for all that work, the power gains are probably minimal, especially considering how much $$, work, and time you have to invest.

 

'99 White Lite -

So it would stand to reason that the more boost and forced air you tried to shove through the cylinder heads the more benefit you will see from better flow (less static pressure to overcome) and longer duration/higher lift cams that will allow the extra charge more time to enter the cylinder.

The old GMC 4-71 and 6-71 blower were a roots style blower and the motors they were mounted on responded to porting, cams, exhaust, etc.

The trick is to make this whole air pump package work together starting with the intake to the blower to the lower manifold into the head and out the exhaust ports. I do think some of the more effecient aftermarket blowers will respond even better at the higher boost levels. Time will tell.

 

I haven't seen it discussed in the L community, but what about some thermal barrier coatings in the combustion chamber, intake/exhaust ports and valves. I use them on another engine and the results are awesome.

 

OK
I will bite!!. If you reduce the restriction on the intake valve, why will it not flow more to the cylinder and give you a larger mass of air to give you more torque when the gases expand. I know this blower is a postive dispalcement blower that pumps a certain amount for each rotation. Let's say you have 10psig boost on stock heads vs. ported heads. The ported head should flow a little more than the stock head with the 10psig applied to it. You will probaly loose some boost with the higher volumetric flow rates to the cylinders but you can change a pulley to compensate for that, and yes I know the stock blowers efficency drops with the overspinning and is probably undersized for this.

 

Cut - n - paste

https://www.f150online.com/forums/sh...threadid=80396

 

First things first. Really you are starting with some mass flow. I think that is the big thing people don't understand. Boost isn't what you care about, you care about mass flow. Boost is just a byproduct of what you have downstream.

So, the math says (and you just have to take my word for it or go look it up in blower specifications and books) that a certain size blower, with some inlet density, and some speed, moves some amount of air. We'll call that mass flow. For the sake of argument, nothing downstream changes that mass flow. In reality, the mass flow does change in small amounts, and that's why you see some change in power (among other reasons), but understand it is pretty small.

Now you take this mass flow, and shove it into some engine with some size and some speed, and some inlet restrictions. Now keep in mind, none of this stuff affects the original mass flow. The boost then becomes the pressure that the air in the manifold is compressed to. Its easy to measure and easy to talk about, but isn't what really matters. Also, the pressure in the cylinder will be at some value less than the boost because of the pressure drop gettting into the cylinder (ignoring exhaust stuff here).

Now you ports the heads, increase valve sizes, change the cams and so forth, so you have made it easier to get the air in the cylinder. The starting pressure in the cylinder is the same (because the mass flow is the same), but the pressure drop across those orifices is lower, so the measured boost will be lower. There is no power gain due to getting more air (and fuel) into the cylinder. There is a power gain from the blower since it is now pumping air into a lower pressure it requires less power to turn. But that is also a small gain.

When you decrease the exhaust restriction, you're allowing more of the burned gases to make it out of the cylinder. The mass left in the cylinder is called residual mass or internal EGR. The blower doesn't care how much is left in, it will just add its own on top of it. But if you can get more out, then you are starting with a cooler, lower pressure charge, which in turn lowers the detonation risk. Since the starting pressure in the cylinder is lower with exhaust mods, and the delta pressure on the inlet is the same, the boost will again be lower, but just like before its a small gain in power.

People assume that an engine that came from the factory just can't have good parts on it. They absolutely must spend money on their vehicles. It seems unfathomable that what's already there might just 99% as good as it can get. If your gonna spend money, just realize what it is your doing, and whether it can really do anything. If you want to spend $1000 and 2 weeks for 5 hp, more power to you. My truck may not be the fastest, but it will be the fastest for the $$.

 

Overcoming static pressure will cause an effect on the mass flow.
TP = VP + SP. Restriction causes a negative static pressure number so the more of that you eliminate the more Total Pressure you will ultimately have in the combustion chamber during the compression stroke. Furthermore combustion chamber design which can be changed when "porting" heads can lead to more effecient combustion which means more HP.

I think we may just have a difference in what we call "meaningful." $2000 for 30-40 HP is not worth it to some while others want to squeeze everything out of an engine they can. One thing is certain, it gets more and more expensive to add horsepower as you keep increasing your output.

 

NeedFourSpeed
Yes, I am running the Farrea (Mod Max) valves. And they are modified quite a bit. My cylinder head guy has an idea on what he wants the valves to look like and they would be a mostly a larger version of a stock valve. I would also like to try a tulip shaped exhaust valve with a 30 degree back side shape.
Also please dont get me wrong about the stock PI heads, for what they are they flow well. Its just that my cylinder head guy had a hard time finding gains at the low lift range and that is upsetting. I had plans on jumping into these heads and finding about 30% at .100 to about .400 lift, just what a heavy truck would need, but it didn't happen. The flow gains didn't start to happen until .400 lift and by then it almost to late (with a stock cam).
I hope your right about Edelbrock, I have always liked there stuff.
There heads come a little raw, but always have all the good stuff engineered into them. A good cylinder head guy can make them scream.

And 99' White Lite

Thanks again for the hydraulics lesson J/K

Just remember one thing....I'm a hot rodder, not a financial genious. I understand that I could buy one of Johnny or Sals blower's for 3000.00 and be ahead by probably 100hp. or more.
But I chose to spend 2500.00 on a set of cylinder heads and further more I'm not finished with this little project yet, WHY ?
Simply because I'm curious ..... that's all....just curious.

And when I'm done learnin what I want to know then I will buy the damn blower.

Dale

 

... and there's nothing wrong with learning!! I try and do it every day.

From where I'm coming from, though, I just don't see any meaningful gains from the head. Someone mentioned 30-40 hp, and i really see no chance of acheiving anywhere close to that. Not even "combustion chamber efficiency" will get you there. I'm definately interested in the outcome of your project. I don't think you will like the results, even when totally replacing your head with edel's when available. But I will have no problem admitting I was wrong if that's not the case.

Naturally aspirated engines can see big changes with what your doing. The mustang guys would probably be very interested.

Now with a new blower that is supposedly more efficient, and has a larger displacement, there's no way not to make more HP.

 

Dale, is that how much you spent to port the heads or just a number you through out?

I know JL offers ported heads w/ larger valves that cost over $2k, and he claimed a 40hp increase. But I can't remember if got that with or without the KB blower on it.