Ed Curtis

... Only if that's the goal of the shop...

To provide MASS PRODUCTION....

Ed

02Reaper

iTrader: (2)

Where are all of the head porters to explain this? It seems like whenever a good discussion like this comes up, most of them remain silent. Im still waiting on a decent answer on your first question too the head porters about trying to sell the guys with 5.3's and 4.8's the same heads as they sell for the 5.7 and 6.0. Maybe they really dont know wtf is going on.

Sport Side

iTrader: (6)

All 3 of these quotes deal with different buyers, different vendors.

I've never seen a truck guy yet break the .600 lift mark. More than 3/4ths with aftermarket cams I bet have below .550 valve lift. Why would a 4.8/5.3 need 2.02/1.57 valves?

These would have worked chambers to fit the LS1 bore right, why offer it to the 4.8/5.3 crowd.

This is a quote from a buyer of a set of State 2 ___ heads:Can 2.04 intake valves even fit on a stock 5.3 chamber? A point and a half in compression?

Seems no one yet has listed vendor names, so I didn't either. These are from some of the top selling companys on this site which is what worries me the most. Maybe some of my assumptions are wrong, but the vendors doing the selling never stated how or why these heads would work the best that I saw.

All of these quotes are related to guys with a 4.8/5.3L w/ 3.78 bore size.

02Reaper

iTrader: (2)

The point is, that if some of the top vendors will tell us that this will run bad *** with a small bore like ours, then do they really know what they are talking about with anyone?

FASTONE

I believe there are certain brands of heads proving there worth in terms of either track times or less important on the dyno.With the AFR head some vendors are posting their own flow numbers and thats a good thing for the consumer.You also have to realize that the AFR head is a threat to their profit of porting stock castings even if they are a AFR dealer.Where does this leave the consumer??? If they are not a AFR dealer what are they going to say about this head as they have nothing to gain either way.At least the AFR dealer has a chance to profit from the sale of the AFR head.I"m not picking on AFR just using them as an example.I"m also not blaming any vendors or bashing in any way.For a porter to stay on the top of this head game is to produce a head that puts out or produces good results.This is no secret as most guys are happy to post their good numbers from their well chosen parts.

Now you are not going to sell heads to everybody,some can pay more for the BEST HEADS and some will shop for the cheapest ported heads they can buy.If you are the best headporter then you CAN charge more and get it!

Also on heads flow numbers are just a small way to compare heads,what about chamber shape,Chamber size,flame travel,valve drop,port volume,port velocity,how about swirl or turbulance?

The top porters on here are not going to give away all their secrets,and they are not going to answer all questions asked either.

I think the best way to compare heads is by the independant test from the buyers themselves.We all know there are certain vendors heads that are out doing others.I have some other thoughts but I can"t type as good as J-rod.

Hysteria

It seems to me that Sportside 5.3 already knows what kind of heads he wants, it just seems that he wants some one at some of these places to tell him what he wants to hear when he already knows the information that is important to him. I do not mean this in any way but in a helpful way to you. You sound like you know what you are talking about, just tell a company of your choice what you want so they will build them for you. The main reason all of these heads are set up for a 3.9 or larger bore is because of the main stream buyer has that bore. I also agree with you about the 2.04 valve being to big for the bore.

Sport Side

iTrader: (6)

hot damn! you figured me out
much? gimme a break

?seriously, lets keep this about the heads. not your feelings especially when you have no idea what your talking about. thats fine if thats what you think,

but focus more on us getting bad products/ripped off/or sold the wrong thing. isn't this where were at about now guys?

Sport Side

iTrader: (6)

I'll actually go ahead and break up some of your comments, since all but your opinions of me can be related.


Which company? I am well aware of this and it is more than likely the reason they try and sell us these heads, wouldn't you agree? Wouldn't it be nice if they actually were selling us the right product? Have you ever talked to the majority of the truck guys? Alot are more unexperienced than me and I'm 16. Thats alot of money to waste on a "wrong application product" ya know. I mow grass for money. If I am gonna spend it on my vehicle, I would like to know I'm gonna get what I payed for.

This would not only be my point. A valve that size on a 5.3 is more than likely not the way to make power. would you agree? Well if so, then why are these vendors selling us this? Do some not know what the heck there talking about? Seems that way. This isn't a good thing, especially the way this site praises the vendors. If they are the ones were suppost to depend and go to, I would atleast like to be assured they have an idea on what they are talking about.

02Reaper

iTrader: (2)

Well, not everyone knows exactly what they need compared to what they want. If I have to call a vender up and tell him how to do his job, then maybe he shouldnt charge me so much, since I did all of the thinking. The point is, that if they really know what they are doing, then they should be able to set you up with the right heads for a variety of engines. Not just the 5.7.

Hysteria

I do agree. The thing about what the companies are offering is what they hear most of. Big valves, big flow numbers, and a cheap price. So to do that they stick a big valve in there carbon copy ported heads with a chamber set up for the most common bore to keep overhead low and pricing down. There is a such of thing as a customer knowing what he wants based on his/her research and requesting a custom head package. It is like custom cams over shelf grinds. Another reason they are sugesting a 2.02 valve is because of the size of engine, not the bore size exactly. Look at the older 327s back in the 60's. Same size engine, 327-325, same performance expectation but different bore and stroke. The bore diameter still is an issue but with the 15 degree valve angle its not as much of a big deal on valve shrouding as the older 23 degree on a simular bore diameter.

critter

iTrader: (9)

Hmmm ... is the glass half full or half empty?

Suppose I don't want to pop for a sheet metal intake, or Hilborns or whatever. Seems to me I would want heads that work with the intake I can afford or am forced to use or simply choose to use.

Sport Side

iTrader: (6)

Very True.
I'm hoping this thread is used to wise people up (like Cam Discussion 4, started by Denzss) so they know what to look for, and possibly learn something from it, which I'm hoping to also.

I was using bore size as a factor mainly because its one way of of understand were not dealing with the same motors as the ls1 crowd. Also, you can see by stock valve sizes, going up .11 of an inch on the intake valve could easily be overkill for a 325ci motor not demanding as much air. Plus, most people are running street vehicles which concerns lower rpm torque.
Stock valve diameter 1.89/1.55ex (325ci)
Stock valve diameter 2.00/1.55ex (346ci)

Another matter I'm curious about and hope to be discussed is the exhaust to intake ratio.
-how it varies at certain lift
-how to figure
-what % head porters are shooting for
exc.

Greg Good

critter, I'm not following your line of thinking. Are you speculating that an engine with a suckee intake won't benefit from good flowing heads?

I disagree. I don't really care what intake goes on an LS1, a stock one, an LS-6, a FAST, or a custom sheet metal one. The better the heads are, the better all those manifolds will run. One thing that most people don't seem to know is that steady state flow numbers are not an absolute indication of how fast the manifold will run when working with long runners. Why? Because flow through the intake is NOT steady.

On a long runner manifold that contains a lot of volume, such as is the case with an LS1 manifold, the better the head flows, the more completely the air in the intake runner will be emptied into the cylinder. That the manifold drops the head a lot on the flow bench only means to me that it will take longer to refill, but there is plenty of time for that to happen before the next intake stroke begins.

It's a different program on a short runner single four barrel manifold. If you pick up steady state flow on one of them, you will almost always see a gain in power, unless the manifold already flowed enough, or in opening it up you made it too big and lost velocity. On one of those engines, the head empties what is in the runner of the manifold and then starts drawing from the plenum. That's why steady state flow tests work in porting one of those manifolds.

Steve - Race Eng

iTrader: (1)

The maximum obtainable horsepower is related to the intake flow. By intake flow I mean the flow through the intake manifold, throttle body, inlet hose, whatever. You do not want to put a poor flowing intake manifold on a good flowing set of heads. That's like trying to breath with a rag stuck in your mouth. True, the power will be better than putting that poor flowing intake on a poor flowing set of heads but for max performance you want a good flowing intake manifold on a good flowing set of heads.

If you look at the flow charts J Rod posted of my flow test you will note that the LS6 intake manifold flowed substantially better than the LS1 manifold at all but low lifts. SuperFlow gives us an aproximate horsepower output per cylinder based on air flow measurements. With radius plate this figure is 66.8 HP per cylinder, with LS 6 manifold 60.4 HP per cylinder, and with LS1 manifold 55.6 HP per cylinder. So according to SuperFlow's extrapolation the LS6 equipped engine should be able to produce 483.2 HP whilst the same engine with LS1 intake manifold will produce 444.8 HP or a drop of 38.4 HP. Note that these are theoretical numbers but the results of a better flowing manifold should be obvious to all.

If you look at the flow numbers per cylinder for the LS1 intake manifold you will note that the intake runner for cylinder #7 is not up to the other runners in flow. GM apparently fixed this deficiency on the LS6 intake manifold which showed much more even flow.

It has been shown time and again that steady state flow testing very closely approximates the results obtained by pulsating flow testing. SAE has several articles on the subject if you are interested in reading them.

One thing I would recommend some of you try is reducing the length of the runners in these stock type manifolds. The Ford guys do this with their very similar looking intake manifolds with very good results. You need to cut the bottom off the LS6 manifold to get inside but I think it would be worth the effort.

Regarding the flow numbers. If the numbers look too good to be true they probably are. When I first took a look at the heads I knew there was no possible way they could flow much better than a stock set. No work done in the valve bowl area at all. Valves weren't even cut back. They were CNC "ported" but I bet almost nothing was removed from the runners.

The number to look at which is not shown in any of the sheets J-Rod posted is the valve discharge coefficient. If this number is ridiculously high one knows right away there is something not right with the stated flow numbers. In essence a 2.02 valve is going to pass x amount of air per lift regardless of the port that is feeding it. Don't expect to see 320 - 330 cfm out of a 2.02 valve, it is not going to happen.

Another number you need to look at is the minimum port cross sectional area. Everyone likes to use port volume but that is not sufficient. Note that if we attach the intake manifold to the head the port volume now would be the volume from the intake runner opening to the valve. The longer the runner the greater that volume number is going to be. Not telling us anything about the area of the runner where it is smallest. That minimum cross sectional area in proportion to flow determines just how good the heads actually are and how much torque one can expect to get.

I have my opinions on intake to exhaust ratio related to power output as I am sure many others have that are in this business. I consider that proprietary information but I will say that a great deal depends on the camshaft timing and lift on the intake vs. exhaust valve. I have expensive simulation software to work this out but this is only applicable to high dollar engines where I can absorb the cost of running the simulations for hours on end.

Same is true of horsepower numbers as is true of flow numbers. I have access to five different engine dynos. The one that gives the lowest numbers is the one that gives the most accurate numbers by far. When one sees very low brake fuel specific numbers, those approaching diesel engine numbers, one should see right away the horsepower numbers are too high. But horsepower numbers sell engines just like flow numbers sell heads.

Let the buyer beware!

I'm going out of town for a couple of weeks. I will try and follow up a bit more when I return.

Greg Good

A steady state flow increase does not absolutely guarantee more power when you're dealing with an LS1 type manifold. Some things concerning engines that we "think" are self evident truths, are not.

Once upon a time I instructed the cylinder head class at SAM. We were performing tests on Judson's SS Camaro. A student did a new set of heads, we put them on the car, it picked up 45 horsepower at the wheels, and ran a correspondingly better time at the dragstrip. Ok, so far, so good. Stock black plastic LS1 manifold on the car, which was the only thing available at the time. After we saw how much the heads increased the power, we focused on improving the manifold. First thing we did was flow a stock head with a stock manifold bolted to it. It went 210 cfm @ 28" of water. Took a spare LS1 head, ported one intake port to match the heads on the car, 300 cfm, bolted the stock manifold to it and the pair flowed 215 cfm. We were all of a sudden wondering how a 5 cfm flow increase, measuring it in a steady state manner, could result in 45 more horsepower. Wow, what an awesome 5 cfm. It just didn't add up though using our preconceived notions.

So, to work we went on the manifold. We cut the bottom of it out to gain access to the runners. The runners themselves looked nice. Smooth gradual turn from the head into the plenum with no abrupt changes in direction. Entrances to the runners weren't radiused well, so we epoxied and ported to get a good radius on the entrance. We got the manifold improved to the point that it flowed 255 cfm on the 300 cfm test head, an approximate 40 cfm improvement. All of it from work on the runner where it met the plenum. Nothing internal on the runners themselves.

We "thought" we were about to set the world on fire. How much more power did it make? None. How much faster did it run at the track. It ran exactly the same as before. Theory can never beat results Steve. Results are the greater evidence when there is a conflict between the two.

We stood back, moped around, sulked, kicked some tools around on the shop floor, and thought about it all. Was the world really flat after all? Does the Sun and all the other planets revolve around Earth? The total lack of any gain shook the foundations all of our beliefs concerning intake flow had been founded on. The only rational conclusion we could come to was that the combined volume of the intake runner and cylinder head was enough to fill a cylinder. We evidently did not need to draw air in from the plenum during the intake stroke in great quantities in order to satisfy the requirements of the engine.

Another student that came to the school later did a set of LS6 heads when they became available. They flowed 346 cfm, and with a stock black manifold the car went into the nines for the first time. I never flowed that set of heads with a stock manifold. I didn't even want to know.

So, as far as I'm concerned, gaining flow on an LS1 intake is never a bad thing, but it's not always worth something.





Regards.

Lostpatrolman

iTrader: (3)

Im confused, so in those same reguards.. why does a ls6 intake improve hp on a stock engine? And are you saying that if you got heads that flowed even better then the previous that there would be no better hp improvements? Or if you put that ported intake on and put some worse flowing heads on then those current ones that there probably wouldnt have been any hp increase either?

Greg Good

As for exhaust flow, I have some pretty definite ideas about it, and I'm always willing to talk about them freely.

First off, I think we are taught the "cycles" of a four cycle engine in the wrong order. The first cycle discussed is always the intake stroke, and the nice pictures in the books always show the engine starting off with a clean and thoroughly exhausted cylinder. That is the ideal situation, but it is not how it always happens in real life. The "cycles", in reality, should be taught with the exhaust cycle first. Now, the intake valve opens in the latter stage of the exhaust phase, against residual pressure that's left over from the exhaust phase prior to the intake opening point. The amount of this residual pressure is directly determined by how well the combination of exhaust port, header, and camshaft did their jobs. If they did not do their job, and a high residual pressure is present when the intake valve opens, exhaust gases flow into the intake port. This is the worst thing you could ever have happen. The higher the rpm, the worse it gets. Exhaust gases that enter the intake port displace and contaminate fresh air and fuel, and also counter the velocity in the intake port. You will never have a good intake stroke unless the exhaust stroke before it was a good one. Heads with larger intake valves are more sensitive to exhaust reversion because they flow more air "backwards" at low lift. Any good head porter, when R&D'ing for a better valve job, always takes low lift reverse intake flow into consideration because it determines the rate at which exhaust reversion can get into the intake port during the initial phase of overlap.


The most important part of the exhaust stroke is the blowdown period. From the first point of exhaust opening to BDC I want all the valve lift the cam grinder can give me, and all the flow I can get out of the port at the lifts seen during this time. The blowdown period is the best time to get exhaust flow out because it is leaving the cylinder under its own pressure and the piston is not having to push it out. The valve has not reached full lift by BDC so that means that you need really good mid-lift flow to help the blowdown period. I like for my exhaust ports to "come on" at as low a lift as possible. The valve job, venturi size, and chamber shrouding control this. I've changed valve jobs to increase mid-lift flow. I've run intake lobes with their faster ramps on the exhaust to gain more lift at BDC. It works for me.

Beyond blowdown on the rest of the exhaust stroke, where the piston is pushing the exhaust out, high lift exhaust flow determines how easily the remainder of exhaust gets pumped out. So, the better the high lift cfm number, the less work the engine has to do to get the piston to TDC. When everything is working right, and the port flows enough, and the valve opens just soon enough, the less residual pressure the intake valve sees, and the less exhaust gas enters the intake port.

How much exhaust flow does a guy need? Depends on the application. You guys running street engines on pump gas (low compression) need a pretty high percentage in my opinion to get the job done. Low compression engines do not like an early exhaust opening. The exhaust valve opens during the latter stage of the power stroke. An exhaust valve that opens too early shortens the power stroke and hurts power. That's why the cams you see that are running good on low compression street engines typically have exhaust lobes that are close in duration to the intake lobes.

An engine with high compression, such as 15:1 or 16:1, is not very sensitive at all to exhaust opening point, and we can run 25-30 degrees more duration on the exhaust than the intake. In that case we'll set up the heads to favor the intake ports by cutting down the exhaust valve and increasing the intake valve size. When you are able to run 25 degrees more duration on the exhaust you can get by with 65% of the intake port for exhaust flow. The extra cam duration makes up for the weaker exhaust flow.

How much exhaust flow you should realistically expect also depends on how good your intake port flows. If you have a 300 cfm port, it's easy to get 75% on the exhaust. If the intake flows 350, well it's obviously a lot tougher to hit that 75% number. Basically, with a super good intake port, you try to get as much exhaust as you can and call it good enough.

I consider 70% at the peak with all the mid-lift flow possible to be on the lower end of acceptable for a low compression street car. Anything above that is gravy.

Greg Good

What I'm saying is that:

1. when a flow increase on an intake port is realized, I have an expectation of seeing a measurable power increase, provided that the port cross section was not made too large and port velocity remains good.

2. flow increases on LS1 type manifolds can be very disappointing.

Hysteria

Speaking of overlap, anyone that has ever syphoned any kind of liquid out of a container understands how this works. When the exhaust valve starts to close the intake valve cracks open to take advantage of the gas current that is heading toward the exhaust valve. This way a syphoning effect begins and new air fuel comes into the chamber with out the engine having to draw it in. The problem about this is designing a camshaft to do this effectively on a particular engine. The phases of the camshaft come into play big time to optimize the syphoning effect an engine can create.

CHRISPY

Nope the goal is repeatability, precision and to make money.

If you can make 100 CNC and handfinished heads a month with the greater precision/repeatability than a hand porter that can make 6 sets a month then you can provide the consumer a better product with less lead time and also make more money in the process.

Plus it works out to be less expensive labor/Time wise for the vendor. Digitize the port once, CNC the heads and hand finish. It is a no brainer.

This actually allows a good porter to concentrate on R&D instead of killing themselves porting 10 hours a day to fill orders.

There is a reason why CNC is SO prevelant in all forms of automotive industry.