stroked small blocks in the race cars?

[eschaider]

Ahhh, a sad story indeed. Yet another missed opportunity falls by the side of the road ...


Ed

[1795]

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

[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.

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.

[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

[MAStuart]

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

[1795]

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

[MAStuart]

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?

[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!