stroked small blocks in the race cars?

[1795]

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

Jim

[blykins]

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.

[1795]

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

[PDUB]

Originally Posted by blykins

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.

For clarity Brent, did you change head companies in your comparison, does Dart make both 180cc and 185cc, or was it just an errant finger on the number 5 key?


Either way, that is a nice, impressive number!

[MAStuart]

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

[MAStuart]

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?

[blykins]

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

[eschaider]

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;


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

[PDUB]

Originally Posted by eschaider

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.

Ed

Does a solid roller have a lower life span due to some inherent design issue in the lifter itself, or is this due to other factors like higher spring pressures for running at increased rpm levels? I would not think that the solid roller would fail any quicker given an identical set up. What am I missing?

[blykins]

The cam is where most guys mess up.

[eschaider]

Big +1^


Ed

[1795]

Ed,

Thanks for the chart. The cam I have is from the prior build and is still in good condition. It was designed for the Webers. I probably will need to only do some minor porting to smooth out air flow. According to my cam card, with the 112 degrees of lobe separation, the intake valve opens at 20 BTDC and closes at 56 ABDC. So, taking that into account and looking at the graph you supplied, given that I have rollers lifters, there will be a lot of time for air/fuel flow into the combustion chamber.

Well, now I have to wait until Monday to find out which head I have and if it was ported at all.

Keep the education coming.

Jim

[blykins]

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

[PDUB]

Originally Posted by blykins

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

OK, thanks!

[blykins]

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.

[blykins]

A 112 LSA is a big no-no for Webers in a road race car. That would be more suitable for a street car, where you need to watch overlap, but in a road race car when you're on the gas hard all the time, it will cost you power and throttle response coming out of the turns.

[1795]

Brent,

What lobe separation would you suggest? You have my email address, send me a quote for a roller cam, 11:1-11.3:1 compression ratio, 110-112 octane fuel depending on what's available at the track (some only have 110), the Iron Eagle heads, close ratio top loader, 3:54 gears, the Webers, engine will be bored .030 over, light weight pistons, rods and light weight forged steel crank.

Let me know if there is anything else you need. Planning on running in the 3500-7,000 rpm range.

Jim

[MAStuart]

Ok with all this head and stroker talk I thought you all would enjoy watching some of these


vids by Richard Holderer. It is about head flow and dnyo testing about 30 or more heads . Some of the testing is old and some of the heads are not on the market anymore. A lot of the heads are aluminum so may not be of use to some of the guys here. It is a 4 part series but only 3 parts have been released. Hope some will learn from them. Wanted to add the there is no testing of early 289 heads .

https://www.youtube.com/watch?v=EWSlYvstFIU

[blykins]

I'd need to know what the heads flow, their port volume, etc.

LSA is based on what overlap the engine needs. Most guys want to go 112-114-116 because there's a lot of people on the internet that say the Webers need that.....and I wouldn't necessarily disagree on a street car.....but a road race car is completely different. Depending on the duration, you could end up on a 106, like a lot of the Shelby cars ran.

If you're wanting to save money by keeping the same valve springs, then I'd need to know how they're set up as well.

[1795]

Originally Posted by blykins

I'd need to know what the heads flow, their port volume, etc.

LSA is based on what overlap the engine needs. Most guys want to go 112-114-116 because there's a lot of people on the internet that say the Webers need that.....and I wouldn't necessarily disagree on a street car.....but a road race car is completely different. Depending on the duration, you could end up on a 106, like a lot of the Shelby cars ran.

If you're wanting to save money by keeping the same valve springs, then I'd need to know how they're set up as well.

I will let you know about the heads when I verify which ones that I have on Monday. I will need new springs, as the ones that I have need to be replaced.

If the heads have not been ported, the flows will be what Dart Iron Eagle heads show on the website, as I have no way to measure. The engine builder has a full machine shop, but he does not do head porting from what I recall and he would send them out.

Jim