can someone explain runner volume plz

HankyGT · Feb 27, 2010

With a turbo like you have; it's just going to shove air down it's throat anyhow...so you can eclipse your 550hp goal anyhow. Although the size of the runner is directly related to how much cfm the head will flow; along with being proportionate to the valve size (important and limiting for stock pistons), a large volume head on a small displacement or non f/i engine of small displacement is going to hurt torque and only really breathe at high RPM. This is because a large runner in a small cube engine is going to kill runner velocity. When it is smaller and the amount of air the engine can suck is shoved into a smaller hole, it forces it to move faster, so picks up tq, although it can be limiting at high RPM if you maximize the runners ability to flow. However most off the shelf intakes won't allow you to match that # anyhow so it can be hard to eclipse.

With boost you fill that runner immediately and emptying it fast enough is determined by the valve size and the cam choice. What is also nice is that they will make up for a large runner head to an extent, but they can still act a little lazy until whatever you have gets spooled. I would personally run like a 205cc had on that setup since your block can take it and twist it to the moon. But then you'd make like 600+rwhp lol.

Anyhow, those gt40x's are those the new Z 304 heads that are supposed to be matched with that combo? Make sure they accept a 1/2" headstud/bolt.

Tanus · Feb 27, 2010

your better off looking at flow #s, cause a head with 160cc intake runner could flow better than a 180cc head.

its best to study the flow #s, where they peak and where they start, to help selecting your cam

HankyGT · Feb 28, 2010

^^ This is true, but it also depends on the heads you are buying and if you plan to get further port work done. For instance you're never going to outflow a 205 with a 160 etc.

rj95svt · Feb 28, 2010

volume is 3 dimensional. Some heads have longer and others have shorter intake runners. Example 170cc tfs twisted wedge heads have 1/4" shorter intake ports than say afr 165's or any stock valve placement head. Which means the intake ports cross section is bigger than on a standard valve placement head with the same 170cc volume. It is not all about size vs flow there are many other concerns as well. Valve placement, runner shape, combustion, and othera. It's all in the total design of the heads.

If it was me looking to buy heads for a turbo engine like yours. I would run the new Trickflow fast as cast 190cc TW heads. I believe they have 62cc chambers which is close to what you are looking for. If your block has not been decked to 0 and your pistons are still in the hole a bit you should be ok on compression. I think your biggest concern will be whether or not your pistons have valve relieves for the TW heads although if your cam is not huge you probably won't have any issues.

Boosted engines seem to really take advantage of the revised valve angles in the TW heads.

95cobra50 · Feb 28, 2010

alright well after looking around more i think ive decided on these

Racing Head Service 35017-01 - RHS Pro Action Small Block Ford Cylinder Heads - Overview - SummitRacing.com

now should i get new r/r's for these or use my 1.7rr's?

also here if the flow chart, scroll down for the 215's.

RHS - Cylinder Head Flowcharts

Next question is the with valve lift. Does that have to do with the cam when it says the peak lift is at 0.700? Also how would rr's effect this number?

also im guessing the springs that come with the heads would be able to handle that amount of lift?

sorry for all the questions, i just want to be sure i do this right once not wrong and twice.

revhead347 · Feb 28, 2010

If you turned the head on it's side, with the exhaust valve, the runner volume, it how much water it would take to fill that port. Well, water, oil, whatever. I wouldn't worry too much about flow numbers. With the exception of the Trick Flow twisted wedges, all the other heads are basically the same casting. There are a few different casting designs. The AFR 165/Edelbrock/otherwise entry level head are about a 20 degree valve angle, and a stock exhaust port location. All the heads with those parameters are bascially the same. The new AFR 185 has a raised exhaust port for better flow, and I think it has a slightly shallower valve angle. If you find a head that advertising raised exhaust port, then it's going to flow about the same as an AFR 185 with similiar runner volume. Generally speaking, a larger volume runner flows better. However, in practice you might lose a little low end torque, which may not be worth the increase in power up high. With a turbo, you want a pretty large intake runner. That gives you good flow on the intake, allowing you too make more power with less boost. Low end torque is generally not a consideration on a turbo engine. You also want a slightly disproportanally smaller exhaust port to keep your exhaust velocity high. That being said, those heads should be fine. I have never used RHS heads, but I've heard good things.

Kurt

Tanus · Feb 28, 2010

those rhs heads are badass, the rhs iron 180cc is gonna be the next heads I get

those 215's flow some serious air, the 180s or 200s would probably be a better choice unless your planning to make like +800 hp. IMO

rj95svt · Feb 28, 2010

95cobra50 said:
alright well after looking around more i think ive decided on these

Racing Head Service 35017-01 - RHS Pro Action Small Block Ford Cylinder Heads - Overview - SummitRacing.com

now should i get new r/r's for these or use my 1.7rr's?

also here if the flow chart, scroll down for the 215's.

RHS - Cylinder Head Flowcharts

Next question is the with valve lift. Does that have to do with the cam when it says the peak lift is at 0.700? Also how would rr's effect this number?

also im guessing the springs that come with the heads would be able to handle that amount of lift?

sorry for all the questions, i just want to be sure i do this right once not wrong and twice.

We really need to know your plans and goals for this setup. Are you building a stroker? I see it's a boss block but how big? 302,331, or 347? Are the 1.7 roller rockers you got pedestal mount or stud mount? If you have pedestal mount rockers now and I was buying these heads I would buy the comp rockers that are recommended by RHS from the link provided.

The valve springs that come on the heads are only good for .560 lift according to the link to summit. The peak lift for flow testing was .700 but the heads do not have the valve springs to support that much lift.

The questions you are asking tell me you need to talk to a professional engine builder instead of piecing this stuff together yourself. It will save you lots of headache and money.

Black95GTS · Mar 1, 2010

Tanus said:
your better off looking at flow #s, cause a head with 160cc intake runner could flow better than a 180cc head.

its best to study the flow #s, where they peak and where they start, to help selecting your cam

Why does flow matter with a turbo engine? He's going to max out the flow on basically any head he uses. No matter how much boost you are making, you still can only flow the static maximum value of the heads.

Say you have a naturally aspirated engine that maxes out the heads at 250cfm. Then you put a turbo on there, and run 8 pounds of boost, basically using 1.5 times more air. Do the heads now flow 1.5 times more? NO! If you think about it, especially on forced induction engines, air flow in cfm is far from the most important factor.

And whoever says using big heads with a small cam will kill your low end torque, I refer you to the LSx engine.

Adam

BlackVert · Mar 1, 2010

didn't pokageek get RHS heads initially and he was not satisfied them?

maybe i'm nor remembering correctly ...

in any case, even though flow numbers are less crucial when boost is involved, heads that flow well will allow boosted air to move through them better too.

BlackVert · Mar 1, 2010

do you already have the boss block?

word of warning ... the bore length on the boss 302 block is shorter than stock and that makes boosted applications more difficult. read this for more details ..

Boss b-be Aware!!! - Hardcore 5.0 - The Hardcore Ford Drag Racers Forum

and read post #17 ... since you have a power adder ...

good luck

rj95svt · Mar 1, 2010

Black95GTS said:
And whoever says using big heads with a small cam will kill your low end torque, I refer you to the LSx engine.

Adam

I agree 100%

Tanus · Mar 1, 2010

Black95GTS said:
Why does flow matter with a turbo engine? He's going to max out the flow on basically any head he uses. No matter how much boost you are making, you still can only flow the static maximum value of the heads.

Say you have a naturally aspirated engine that maxes out the heads at 250cfm. Then you put a turbo on there, and run 8 pounds of boost, basically using 1.5 times more air. Do the heads now flow 1.5 times more? NO! If you think about it, especially on forced induction engines, air flow in cfm is far from the most important factor.

oh so he sould just use stock heads since flow doesnt matter?
and yes the heads flow more with boost, heads are flowed (usually) at 28 pounds of pressure, if you flow tested them at 100 pounds they would produce higher #s

Black95GTS · Mar 1, 2010

Tanus said:
oh so he sould just use stock heads since flow doesnt matter?
and yes the heads flow more with boost, heads are flowed (usually) at 28 pounds of pressure, if you flow tested them at 100 pounds they would produce higher #s

Your confused between inches of depression and pounds of boost. Heads are flowed at 28" of water like Kurt mentioned.

And they don't increase flow on a real engine, like I discussed in my post. You can artificially flow heads at 100" and have crazy flow but that doesn't do jack crap on an engine. Here's something for you to Google, why do you use 28" as the standard?

Read my post. I said nothing about it being useless to switch heads, I said that he shouldn't get caught up in flow numbers when there are more important things to consider.

The flow through the heads DOES NOT change, the density of the intake charge changes. So when the piston starts back towards bottom dead center, you have an increased amount of pressure in the intake tract, which is boost. The vacuum caused by the piston's descent is still the same, so now you have the vacuum from the piston pulling air, and you have the turbo from the engine pushing air. The cylinder is filled more efficiently, through the entirety of the intake stroke. When the compression cycle occurs, there is more air and fuel to compress, making more horsepower.

The engine is an air pump, and it is limited by the volume of the cylinders as to how much air it can flow. The density of that air is variable.

Adam

95cobra50 · Mar 1, 2010

Tanus said:
those rhs heads are badass, the rhs iron 180cc is gonna be the next heads I get

those 215's flow some serious air, the 180s or 200s would probably be a better choice unless your planning to make like +800 hp. IMO

well maybe one day haha

We really need to know your plans and goals for this setup. Are you building a stroker? I see it's a boss block but how big? 302,331, or 347? Are the 1.7 roller rockers you got pedestal mount or stud mount? If you have pedestal mount rockers now and I was buying these heads I would buy the comp rockers that are recommended by RHS from the link provided.

The valve springs that come on the heads are only good for .560 lift according to the link to summit. The peak lift for flow testing was .700 but the heads do not have the valve springs to support that much lift.

The questions you are asking tell me you need to talk to a professional engine builder instead of piecing this stuff together yourself. It will save you lots of headache and money.

for this set up just 302 with a goal around 550hp. If the 500hp zone ends up not being enough i may stroke it to a 331. the 1.7 are just the stock cobra ones so whatever they are. I think i may just buy these heads bare then and get the 1.6's RHS has on there and proper springs/valves for upto .600 lift.

do you already have the boss block?

word of warning ... the bore length on the boss 302 block is shorter than stock and that makes boosted applications more difficult. read this for more details ..

Boss b-be Aware!!! - Hardcore 5.0 - The Hardcore Ford Drag Racers Forum

and read post #17 ... since you have a power adder ...

good luck

yeah i do, man i've never seen this. If i remember correct it have a 3.0 stroke so it would be 4x3. I will def get it checked though!

Tanus · Mar 1, 2010

heads flow more with boost than they flow NA, case closed

revhead347 · Mar 1, 2010

Another thing to look at is how much they flow at a certain lift. Most of the head manufacturers advertise flow at .700" lift, which is an unrealistic value. If the heads only flow 260cfm, they wouldn't be going on an engine with a .700" lift cam, yet they advertise that number anyway. Use a comprehensive chart, and compare lift at .500" lift.

Kurt

Black95GTS · Mar 2, 2010

Tanus said:
heads flow more with boost than they flow NA, case closed

Prove me wrong, flow bench racer.

Did you figure out why they use 28" of water yet?

Adam

95cobra50 · Mar 2, 2010

the head doesnt flow more its just that the air inside there is compressed to its "more air" when boosted

can someone explain runner volume plz

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