Pop Hot Rodding has an article on the winning 509" BBC that makes 851hp on pump gas. I've always thought that heads were the key to building great power, but this guy seems to have focused on reducing friction and oil control. I was surprised to find that he used heads with 300cc ports that flow 380 cfm peak and a 4150 carb.

My questions are:

Does limiting oil drain back over cam decrease life of roller lifters in a street car?

Should I consider 335cc heads (as opposed to 355cc or 360cc) for my own 580" build-up?

A 260 degree, 0.800" lift cam seams big, but the power peak was 6,400. So should I assume a 14% larger motor wants 14% bigger cam, like something with 0.900" lift and 300 degrees? Yikes!

Thanks

 

By the time you put that engine in a car with a street legal exhaust system, it's going to be at least 200 HP lower SAE net than what you can measure on a dyno SAE gross.

With that much overlap any backpressure is going to KILL the torque curve.

Reducing internal friction is a laudable goal, but there are limits to what you can do an not affect durability.

A long stroke engine can use "more cam" than a short stroke engine, but as I always advise for a street engines, the most useful measure of engine output is the 80 percent torque bandwidth, NOT peak power, but the mean piston speed at peak power is useful since it can be compared to other designs. The current "limit" is about 5200 FPM on F1 and NASCAR unlimited engines, and the LS7 at 4200 FPM is excellent for an emission controlled OEM engine.

Friction power increases with the cube of mean piston speed and VE falls off with the square beyond the torque peak. This is why their is a "limit" on achieveable mean piston speed. The engine gasps for air, and rapidly increasing friction power begins to comsume what the engine can produce.

Duke

 

That contest is very fun to watch..but you have to take it with a grain of salt. Those are "Dyno race" engines designed to make 3 back to back pulls to win a race of average HP/TQ from 2500-6500 rpm. You can get lots of good ideas from them, but all of it won't work on the street OR the track.

He used a crank of a little over 50lbs..about a 20 lb weight saving over an average stroker crank. He used a very high $$ one so that he could trim the counterweights and remove weight and keep it strong enough. He used lots of Mallory metal to balance it. He used 1.88 Honda rod bearings which would likely be OK..NASCAR has been doing it for a long time. He trimmed the main bearings significantly thinner to cut friction..not sure about long term reliability.

Anytime you reduce oil flow over the cam you will cut life. Great in a race car under short run conditions..not great for long life. He did do some good work to direct oil to end away from crank. A couple of years ago Kaase and others fabricated a tube to let cam run in a bath of oil to help it live, plus they directed oil away from crank with baffles.

Lots of coatings in there and that's good stuff.

Ring drag IS a big deal...again..long term life will be questionable though. You can do some work there to help a lot...but notice he used gas ports. Lateral ports may help over long term to keep them from plugging up. Looks like he did a LOT of work to seal it tight though.

Cam is .850 lift with only 250* or so? Can you imagine the rate of lift on that dude? Not going to live too long..but it will make some killer cylinder pressure.

Heads and Intake were very impressive. He got 380 cfm out of a 300 cc or so port..thats great in BBC world. Looks like it took a LOT of work and some epoxy. He even mentioned testing several sets of heads that did better on flowbench, yet didn't give results needed. Flowbench racing ain't everything either! Again, he was looking for at least 600 ft lbs at 2500 rpm! He definitely created a good TQ bandwidth! Not too sure how useable it would be..but it wins a dyno race!

In the end, this guy spent LOTS of time sciencing out the combo, just like Kaase said he pretty much worked on nothing else for the prior year when he was doing his.

Great stuff..but look closely at what you intend to apply to your own project.

I'd love to see one of these motors in a well set up car to see how it actually runs!

JIM

 

Listen to Jim. He has real world experience with big cubic inch motors and knows what he is talking about. He puts serious miles on his 540" 825+ HP BBC including driving it from Houston to Bowling Green (and back) a few times! Right now he is knocking on the 9 second door.

Steve

 

i love the build-ups

 

I had a 509BBC in my endurance racing boat. We determined that running sub .800 lift numbers was the answer to longivety. We had friends and fellow competitors running mid 800 lifts and spring breakage was a common thing. I'd rather be down on power and wax the hull every day than break motors

Our cams were mid 260's We bought the boat with a collection of spare Howard SR cams like 264/272 with .760/.780 net lifts after lash.

I've always been a big fan of getting the max CFM with the lowest lift.

 

I enjoy reading the Engine Master’s Challenge, sadly I think it is the closest thing any hot-rod magazine gets to head-to-head testing. In this case you read through the lines at what the some of the country’s top engine builders use for parts. (Lots of Brodix heads in these big blocks and lots of coatings.)

Unfortunately, the hot-rod magazines won’t do head-to-head testing. There are thousands of 383, 10:1 motors being built out there, how about testing three or four 195cc heads on the same mule to see which work better. Manufacturers could even chime in with why their head did or did not work better and their suggestions could be tried in a follow up article. How about using various coatings in a motor and doing before and after testing?

Is it fear of losing advertisers? How come “Road and Track” and “Car and Driver” can run head-to head tests? They are unflinching in some of their reviews.

Sorry for the rant, getting off topic, but it’s difficult to separate the hype from the stuff that works in this industry.