All kidding aside, I have to call the engine builder Monday and find out which Dart Iron Eagle heads I have and check out to what degree they already have been ported. I checked all of my paperwork from initial build and there was no description of the size of the heads, flow numbers or part number. There are three options with these heads. (all flow numbers are intake) 180 cc that flows 262 cfm at .700 lift; 200 cc that flow 285 cfm at .700 lift; and 215 cc that flow 306 cfm at .700 lift.

My cam has a maximum lift of .606 on the intake valve, so that will cut those flow numbers down as they are based on .700 lift. At 50 degrees the intake is .256. Running the eight stack Webers and 11:1 compression ratio.

Any thoughts? My guess is that I have the 180 cc heads, as the current builder stated that the heads will be the limiting factor on power and the choice becomes port them, or at about a cost of $650 per head new, buy the next size up.

Jim

You don't want to buy the next size up if they are 180cc.

A 180cc port is plenty big enough for a 289. My 347's make almost 550 hp with 185cc heads.

The goal in porting is to increase the velocity and flow, not make things bigger per se.

We can essentially make a port "huge" and it may not do anything but make the engine sluggish.

With that Dart head, there's not any reason why you shouldn't be making up over 475 hp. Camshafts have a lot to do with that and most guys tend to pick stuff out of the catalog, which is a big no-no. You end up with a Chevy cam. If you mean that your cam has 256° duration at .050" lift, then your engine should be making a ton of horsepower. My 289's with ported factory heads (200-210 cfm) make 440-450 hp with about 10° less duration than you and only .500" net lift at the valve.

Thanks Brent,

That's what i needed to hear. Thanks, for correctly restating what I meant to type this morning, 256 degrees duration at 0.050" lift. I do want some more power to offset the added weight of the Dart Block. I also have read in my research what you stated regarding increased port size potentially having the effect of bogging the engine down. I just want to make sure that there is enough velocity and flow to provide the power at the upper end. Investing in a lightweight crank, rods and pistons so that the engine easily spins to 8,000 rpms is worthless if there is not enough air/fuel mixture to support it.

Hope that your family had a nice Christmas.

Now get back to work, you have engines to build :LOL:

Jim

The block may be a bit heavier, but it will result in more horsepower due to thicker walls and better ring seal.

Remember that with a new block comes different challenges to flat tappet camshaft situations. The lifter bores won't be in the same place as your factory block.

Era
 

Sounds like a great second career.

Fred

Thanks Brent. I have roller lifters so hopefully that will make it easier. This guy has been working on Ford engines primarily since the late 70's and has used some Dart blocks previously. He actually had one sitting in the shop for me to look at. He has already discussed some improvements to strengthen the valve train. Always appreciate all of your input.

Jim

Jim If your heads are the small ones and they really flow those numbers and are not ported yet. They flow more than you need in the HP level that you are at. Just a thought the higher you spin an engine the fast it will need to be rebuilt. At one time I could not spin an engine high enough or put a low enough gear in the car. I was a RPM freak! Nothing like the sound of an engine at 8000+. But they dont last long. Now days you can build plenty of power and there is no need to spin them over 6500. Less RPM's same power = less gear same speed = less engine wear. Now days I dont spin them as high but go faster than I used to spinning them real high. My engines last much longer

Jim what is the top speed that you have run at any of the tracks your at?

I probably will still limit my top rpms to around 7,000, but will set the rev limiter to closer to 8,000 just in case I am running out of rpms a little before a corner and do not want to throw another shift in before braking.

Top speed that I have done is about 135-140 mph. Not suer exactly as in prior years my camera did not have the ability to show speed. With the new camera with GPS I can get a more accurate speed. We will see this year. Mid Ohio has a nice long back straight so I should be approaching my top speed there. One of these days I will make it out to Road America and that will really allow for the opportunity to open the car up in 4th gear.

Jim

Brent I was checking out you internet site. But i did not get any of the answers to what i was looking for. I was wondering how well equipped your shop was. Do you do all your own machine work , crank grinding, boring, honing, balancing. ect. If so do you have all new state of the art machines?

Well, I think everything is up to date. Last year I upgraded from a yard stick to a tape measure and I bought one of those fancy pullin wrenches that have the little beams on the top.

Jim it has been a long time since i have run my mustang at Road America. I dont have much experience road racing. I have run in some open track events there. I ran in an full track autocross and got a 3 place. I was in a class with r model type shelbys and clones. Asked some of the other guys how fast they were going down the long downhill straight. Was told they were running 150-160. They were running 3.89 to 4.11 gears and turning 8000+. My car was limited to about 135 because of Rev limiter set at 6500 and 350 gear. Not sure i topped it out ever on the track because I am a chicken. My car i run a non overdrive 5 speed and I never got lower than third gear on that track.

Brent It was a legit question. I am getting the feeling that you just assemble? Do you do your own port work or send it out?

I have two head porters that I work with. I don't port here, nor do I do much machine work here.

Jim,

Here is something to ponder for a bit over this idle holiday week.The heads and the cam you are looking for will better serve you if you are not driven by peak lift and max flow numbers. For the remainder of this post the image below might be helpful;

http://www.clubcobra.com/photopost/d...ift_Curves.gif
The chart is comparing a flat tappet to a roller tappet profile and visually illustrates why race engine builders have a bias for roller tappet profiles. With Hydraulic roller tappets we can have access to the same breathing enhancements without the danger of premature tappet failure that plagues solid roller tappets when they are placed into day to day service as opposed to weekend race duty.

The most important range in the lift curve is between 0.100" and nearly but not max lift. The intuitive explanation for this is that the valve passes each of those points twice. It only reaches max lift once! The engine's ability to injest air is substantially enhanced by increasing area under the lift curve in that range that the valve passes through twice.

Look at the area on the graph defined by the two horizontal red lines and the corresponding red and blue lift curves. Imagine how much more lift would be required by the flat tappet cam (blue curve) to replicate the same area under the red curve — stunning is the word that comes to mind. Along with the increased lift you would also need much higher spring rate valve springs to control the valvetrain and more robust everything to take the mechanical abuse as engine speed increases.

The cam chart also tells a significant story about heads that plays out similarly to the cam story. The most important lift range for good airflow on a cylinder head is the range from 0.100" to, in this case, 0.300" (or so). Let's say your heads and cam have a safe operating valve lift of say -.550" perhaps even higher.

Get the heads flowed to find out their true airflow capacity. Lets say their peak airflow occurs at 0.550 lift. My bet is you will find 85% or so of the same flow at say 0.450" lift. This means you should be picking cams that complement your heads and heads with port profiles that provide stunning airflow from 0.100" through 0.450" lift.

If you do this you will have explosive low speed torque and power, a stunning midrange pull and a car with an overall very enjoyable driving experience that brings an electric motor like precision feel to slight movements of the gas pedal as you drive the car.

BTW the story on the 0.100" lift flow numbers is that from 0.050" and down most ports act as if the valve is closed. The begin to "wake up" shortly after 0.050" lift and are capable of (if properly ported) stunning low lift flows that substantially improve cylinder fill.

BTW the proper porting is not sewer sizing as Brent has already pointed out. The proper porting is a clean bowl behind the valve and a smooth natural rolling form from the bowl, across the seat and into the chamber. If you just port match the upper port to the intake gaskets you have achieved probably 90% maybe even more of the casting design's ultimate port flow — which is way more than you need for the kind of stuff we do,


Ed

The cam is where most guys mess up.

Big +1^


Ed

I was referencing an AFR 185cc head on a 347.

www.customfordcams.com

That's me as well. Of all the parts in an engine, my favorite is the cam, and I do a lot of dyno testing to gain data.