We got our hemi heads back from Modern Cylinder Head.

Posted By: Dodgeman67

We got our hemi heads back from Modern Cylinder Head. - 11/22/09 12:53 AM

I just want to thank Jeff for taking care of us on these heads.

As you can see they look really really good, and should make some good power.

Here is the intake side with the flash light shining in it.

Another one without the light.

Here is the exhaust side.

I do have a question for everyone, the machine marks the CNC machine marks left in the ports, would you remove them or not? Jeff said they have removed them and found no HP gain?

What would you do?

Posted By: Anonymous

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 01:00 AM

Modern Cylinder Head always does beautiful work, i have no complaints at all, he did a great job on my hemi heads and would use him again.

Posted By: 452RT

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 01:49 AM

Quote:

Jeff said they have removed them and found no HP gain?

What would you do?

Seems you already have your answer and yes the heads look great.

Posted By: Dodgeman67

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 01:56 AM

I agree, and the only reason I asked was I have a friend that builds several SB2 off brand engines, and the heads are Nascar stuff and both the intake and exhaust are smooth as a baby's butt?

Posted By: sam64

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 02:17 AM

i've heard smoother isn't always better on intake side,but i'm only runnin 10.70s with stock eddys.

Posted By: moderncylinder

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 02:24 AM

you want the smoothest surface which enables you to create the thinnest boundary layer

most nascar/prostock stuff has a nc'd int port, polished chamber and exh port,,, we never seen anything in polishing

Posted By: Gearbox

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 04:04 AM

Hate to Highjack the post, but quick question for Jeff, Stage V CNC with qaulity valvetrain compared to B-1 CNC qaulity valvetrain, which set-up seems to produce more HP and Torque on comparable bottom ends, and cost difference in the end, my thought is they would most likely end up with similiar cost and performance numbers, or am I out in left field.

Posted By: Bob_Coomer

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 05:39 AM

what castings are those? Lets see some flow data

Posted By: mr_340

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 06:48 AM

From my fluid mechanics classes in college many years ago, the air velocity right at the wall is zero (infinite shear stress would be required to have some velocity there), so I would think there is so little flow that close to the wall (within .010") that it wouldn't make much if any difference. Maybe they polish them to make them easier to clean and rebuild after each race?

Posted By: 440Jim

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 02:03 PM

Quote:

most nascar/prostock stuff has a nc'd int port, polished chamber and exh port,,, we never seen anything in polishing

The pro levels have money to throw at things.
Polishing the exhaust should help minimize carbon build up and make it easier to clean what does build up.

Posted By: Anonymous

Post deleted by Defbob - 11/22/09 02:45 PM

Posted By: rowin4

Re: We got our hemi heads back from Modern Cylinder Hea - 11/22/09 03:45 PM

Lets look at the surface of a golf ball, and under stand why it travels so far with so little resistance.

Posted By: Dodgeman67

Re: We got our hemi heads back from Modern Cylinder Hea - 11/22/09 04:09 PM

Very interesting topic guys.

Fred that does sound very logical.

And I assume that's for the exhaust as well, leave them both alone, right.

Bob here is my flow sheet, not as good as yours, but should make go power. I will be posting up more of our combo later to see what yall suggest for a cam for this little engine.

Posted By: HemiGreg

Re: We got our hemi heads back from Modern Cylinder Hea - 11/22/09 05:34 PM

you dont want a polished surface at all for a car engine.
the surface roughness should be such that it slightly disrupts the boundry layer of material(gas/air)flowing over it.
the viscosity of said mixture needs some turblance to properly swirl down the ports and around the turns at an equal velocity. cause air mixture passing a bend creats a differential pressure at bends and would reak havoc exiting the turn if the boundry layer was too smooth.
think skidding on a turn when driving too fast especially when smooth surface-well kinda.
fluid dynamics is a simple principal propetry of all things that flow.
the golf ball and even your hood scoop height above the boundry layer and examples.
also too smooth and condensation may form and submilate out liquid gas too rich and drip.
its all about press/temp/delta press/viscosity/surface finish(Ra.)

Posted By: Anonymous

Post deleted by Defbob - 11/22/09 05:50 PM

Posted By: moeflo

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 06:51 PM

You trusted Jeff with your valuable heads. Why second-guess his advice?

Posted By: Dodgeman67

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 08:21 PM

Ain't touching them Fred.

I agree moeflo, he said they had done it just didn't see any gains on the ones they did.

Just thought it was good discussion.

I have learned a lot and hope others have as well.

Posted By: VanishPt

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 09:32 PM

Jeff, what can i do to get my hemi heads to look like this?

Posted By: Dodgeman67

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 09:49 PM

My name is Jeff also, but just call Jeff at Modern and he will fix you up.

Posted By: Bob_Coomer

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 10:46 PM

What casting are those? As of now I plan to run a flat tappet cam, so those big numbers dont matter much...

Looks nice Jeff..keep us informed on your progress please

What have you decided to go about motor wise? Cubic Inch? Compression? Cam etc?

Posted By: Leigh

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 11:00 PM

Why don't they have the "cathedral" shaped intake? Is that tech passe', or is it a legal deal?

Posted By: Dodgeman67

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 11:15 PM

Bob I will try to post another topic to get some feed back.

But I have two siamese blocks that both would go back standard 4.25 if I wanted to do that, and I have a stock hemi crank and one 4.15 stroke crank, these are Mopar Performance heads about 4 or 5 years old, will have to check the casting number.

I also have a set of 13.5-1 Venolia pistons and they are standard bore, and I have a set of aluminum rods for them, so my plan is to build a 426 with one of the blocks. I need some cam recommendations for it if anyone has any suggestions.

Back to the plan, we want to build this 426, put these heads on it, get our headers build and get everything worked out and then get the other block on the stand and we will probably sell the 4.15 crank and find a 4.5 or bigger stroke crank and build a 572 or something in that range and pull the 426 out, pull the heads off of it and put them on the big motor. I will keep the 426 short block complete for a back up engine, just in case.

This is out plan anyways.

I still need a cam, lifters, push rods, head studs, head gaskets, and a timing chain set, also will have to have a flywheel for an 8 bolt crank, for the power glide, and new slicks.

Does it ever end.

Posted By: Bob_Coomer

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 11:25 PM

If you are interested in very large solid flat tappet cam and lifter set new in box from Barton (Bullet Cams)...Let me know..
Lifters are the Howards EDM AMC that will also oil through the push rod if you want it too.
I was going to do this and add restricters in the pushrods to fight some of the oiling issues people have had from Hemi from time to time.

Posted By: Dodgeman67

Re: We got our hemi heads back from Modern Cylinder Head. - 11/22/09 11:30 PM

Thanks Bob, but I want a full roller and get all the power I can get out of it.

Our car is 2,600 pounds full chassis and we want to go fast. We run 1/8 mile and would like to run mid 5's with the 426 and low 5's with the other engine if that is possible.

Posted By: ro23car

Re: We got our hemi heads back from Modern Cylinder Head. - 11/23/09 02:48 AM

why dont you ask jeff about a cam?

Posted By: Dodgeman67

Re: We got our hemi heads back from Modern Cylinder Head. - 11/23/09 02:59 AM

I did, I sent him all of my information today and I'm sure he will have an idea.

I have a couple months or so to get the rest of the parts gathered up, and hope to start the assembly process sometime in January and put it in sometime in Feb. get the headers built and the transmission rebuilt and get it to the track sometime in March or April if the weather is good.

Posted By: sshemi

Re: We got our hemi heads back from Modern Cylinder Hea - 11/23/09 06:06 PM

Quote:

Very interesting topic guys.

Fred that does sound very logical.

And I assume that's for the exhaust as well, leave them both alone, right.

Bob here is my flow sheet, not as good as yours, but should make go power. I will be posting up more of our combo later to see what yall suggest for a cam for this little engine.

Whats the dimensions and volumes?

Posted By: an8sec70cuda

Re: We got our hemi heads back from Modern Cylinder Head. - 11/23/09 06:13 PM

Those look nice! Familiar too.

I have the same heads (MP CNC'd by MCH) on my hemi. I didn't touch the ports or valve job when I got em back from Jeff. I just assembled them and bolted them on. They definitely make power.

CHIP

Posted By: knyech1

Re: We got our hemi heads back from Modern Cylinder Head. - 11/25/09 02:09 AM

Quote:

From my fluid mechanics classes in college many years ago, the air velocity right at the wall is zero (infinite shear stress would be required to have some velocity there), so I would think there is so little flow that close to the wall (within .010") that it wouldn't make much if any difference. Maybe they polish them to make them easier to clean and rebuild after each race?

ME grad and

Posted By: knyech1

Re: We got our hemi heads back from Modern Cylinder Head. - 11/25/09 02:13 AM

Quote:

what I always believed

Quote:

Port and polish Often mis-used term. Back in the early days, aport was ground as large as you could get it and then polished to a mirror like finish with the thinking that smooth was better for air flow. It also looked pretty. When flow benches came on the scene, it was discovered that the polishing part was actually hurting the port. The greater the air speed, the more it hurt.

How can that be? There is this thing called a boundry layer which is actually caused by the friction of the air as it makes contact with the port wall. This friction causes the air to tumble at the point of contact. Compare this to a wave reaching the beach. The closer it gets to the sand, the higher the wave gets until it collapses. Now, with a polished surface, the air does the same thing but because of the drag caused by the polishing (yes, drag), the wave height becomes so high that it effectively reduces the size of the port. Eventually, the wave can no longer support it's self and collapses, only to start over again. Now you have turbulence.

Air needs a lubricant to eliminate this drag. The best lube for air is a cushion of "air". Fine scratches perpendicular to the direction of flow act as a tripping point for the air that contacts it. The air tumbles at every scratch forming what is called a "boundry layer" that about the same size high as the scratch is deep. The air flowing in the port uses this boundry layer as it's cushion or lube and therefor is more resistant to turbulence. You can demonstrate this to yourself by pushing your finger over a mildly abraded surface and then a piece of glass.

So after all that, the "term ported and polished" has stuck with us even though "polishing" hasn't been done for over 20 years.

It's like I am reading my Fluid Mechanics book! Great explanation HEMIFRED I love these topics!!