tinymikey (1/4/2009)

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Any idea what these new castings might be worth in power gains, say single four barrel versus a 6-71 blown drag engine? 

This is a new topic so I've taken this opportunity to make a new post with it.

John hasn't thrown any numbers or expectations out there yet.  Testing will determine this but with improved out of the box flow numbers over the stock heads then an increase in performance is also to be expected.  But raw air flow numbers are never the whole story as improved valve locations, combustion chamber design, and port configurations also play a large part in overall performance.  With the combustion chamber cc’s being downsized to compensate for the inefficiency of aluminum in regards to heat retention, then at least the gains from the other improvements will not be offset or taken away by the use of aluminum.  It will also make sense that for the anticipated increase in air flow for the new heads to be fully taken advantage of, the camshaft, intake manifold, ignition, and exhaust all must be upgraded to match.  Just putting the new aluminum heads on a dead stock engine may or may not see any significant gains in performance but testing will help to quantify this.

I would expect to achieve in excess of 300 HP on a very mild street engine very possible. The use of good soft ware to build an engine, tailor header dimensions, camshafts is very viable. Intake tracts, and exhausts have a bunch of horse power in them.  

TO teds point about head design AFR heads may not flow as much as some others but they produce on the dyno. (Not talking nascar here).

This is air into the engine, and as you have pointed out the total engine package needs to be optimized. The restrictions of the air filter, carb, intake manifold, etc must be dealt with. Increasing the airflow through one area makes the other restrictions more important. A 200 SCFM air filter will not allow a change from 150 SCFM port to a 300 SCFM port to realize any where near its full potential.  All of these restrictions are additive.

Pursuing the optimum carb, runner, port sizes, header (tube sizes and length) exaust system configureation, for power and driveability is a real challenge.

The 2.2 HP potential is reached only by the best engines at high RPM. My paper mild street engines see less than 500 CFM total (250 per port) flow  for a 370 HP engine. Nascar engines flow around 400 SCFM per port and produce well in excess of 800 hp.

Ted's dyno mule 312 is now well documented.  The peak power of the mule at 290 +- a couple HP was right in the area of what I've heard from other people who have dyno'ed stock head engines. I was a little surprised at the peak torque of a little over 340. Even with ported heads, most 9.5:1 street engines only make 350-360 ft lbs.

With that in mind, what we are really hoping to see is an increase in peak torque and the ability to hold a good number to higher rpm. This is what horse power really is.

Anyone care to speculate?

I agree entirely that a broad spread of power is more important than just peak Horsepower.  An engine that makes plenty of power down low is a joy to drive.

Today when I look at either buying a vehicle or building an engine driveability is one of the first things I look at and stays paramount in any decisions made.

I recently had a set of heads (motorcycle) done where flow wasn't the major objective. The heads flowed reasonably well anyway but there was a design flaw which meant much of the incoming charge went straight out the exhaust. The intake valve was recessed in effect shrouding the valve and the port was modified to direct the intake charge at a steeper angle.  The result, less intake charge out the exhaust, the spent charge was cleared more effectively, greater turbulence with the intake charge mean better combustion. About 15% increase in performance but all the way through from idle to top end.    

Now from porting you would know how to improve the ports but you've also changed combustion chamber and spark plug location. These are the things that will make a difference across the whole power band. As long as you've got them right

I find it exciting that someone has taken on redesigning heads for the Y block. And we're getting updates and details as you progress. Happy days.  

Eddie.  For rear wheel horsepower numbers being converted to flywheel horsepower numbers, I’ll typically add 15% for standard transmissions and 20% for automatic transmissions.  But all automatics are not the same and that 20% value could be higher depending upon the drag being generated within the tranny.   These are just estimates though and will vary depending upon the exact application and the particular chassis dyno being used.

Regardless of the conversion math being used, you have before and after chassis dyno numbers and that’s a healthy increase.  Definitely something that can be felt when you drive the car.

Greg.  Those are pretty phenomenal times for stock unported heads.  As Royce mentions, just laying a grinder on top of the heads should be just enough to get that Pinto in the tens.

With the air temperatures finally dropping into the eighties and nineties here in Texas, my roadster with the revamped EMC engine is likewise picking up.  Made a series of easy passes at the local track a couple of weeks ago and was rewarded with three 8.85’s in the elimination rounds with plenty left if I can get the car to leave hard.  Traction was marginal to say the least.