Hi Joe, what heads are you using, are they Johns?

Yes, I reworked them quite a bit, changed the valve job, changed the stem heights, milled them, added a 1/2" spacer to the exhaust ports, etc.  Should be a good pair of heads for the competition.  First dyno session was promising, just trying to get the carburetors figured out.  Not happy with the QF carbs right now, but that is a whole different story.  Just trying to not finish last!  LOL  Joe-JDC

JDC

The pistons showed up so I was able to get this years’ EMC engine together.  The engine assembled without any problems and there's plenty of room around the offending items with the new connecting rods in place.  Torque numbers are good but horsepower numbers are lacking or at least below what was anticipated.  Looks like the heads may be a bit small for 403 cubic inches.  Still have some different things to try but only see minor improvements.
 

Lorena, Texas (South of Waco)

Nice work

Ted not to get caught up in flow numbers but are they where you need them to be at least roughly relative to the horsepower you need to see?

If so is there any way around it like a “faster” intake profile? Etc.

Not to confuse the issue, but for the Y block, the Mummert head is the only thing being cast that has the potential to make 600 hp normally aspirated.  The old tried and true formulas for airflow needed in making x amount of horsepower would show us that to make 600 hp, the intake and heads need to flow at least 292cfm.  To make 640 hp, the heads and intake need to flow 312cfm by the formula.  Not trying to be cute with those cfm numbers, but if you plug in cfm x .257 x 8(number of cylinders), you will see what I mean.  292 x .257 x 8 = 600.352 possible hp, and 312 x .257 x 8 = 641.472 possible hp.  Many factors need to come together to make this happen.   It is all in the details, and removing parasitic loss every place possible, compression ratio, exhaust tuning, intake manifold efficiency, carb tuning, etc..  A Mummert head as cast flows in the 240 cfm range without porting.  With their CNC porting program, the street CNC heads flow ~270/280 cfm, and the race heads with their angle mill, 10mm spark plugs, 1.970/1.510" valves flow slightly better, but not much.  There is just so much aluminum you can remove before making holes in the heads.  I have seen just over 300 cfm on a couple of sets of heads that were hand massaged above and beyond the CNC programs.  To reach 312 cfm, a larger valve is needed, and that would require moving the guides and seats, and changing the ports to the new valve sizes, or a completely new head casting.  Lots of work, for not much return.  Smaller stemmed valves only increase the flow at most 2-3 cfm.  Joe-JDC   

JDC

Thanks Joe. I’d like to know if the upper and lower ports flow an equal amount or is one better than the other?

How do these numbers compare to a contemporary SBF or SBC aluminum head with standard valve configuration?

Upper 280, the lower 270ish on the CNC heads.   Every head I have flowed, and I have flowed probably 20 sets of the Mummert aluminum heads, have a slight problem with the lower port backing up airflow around .570" valve lift in the lower ports.  Not bashing, for the backup airflow can be worked out, but it takes some skill, a flow bench to find it, and sometimes it gets worse before it is worked out.  For a street engine that has a camshaft with less than .550" valve lift, you would never know there was a backup in the flow on the lower ports.  We are using a camshaft with .639" lift, so it is important to get as much flow as possible out of the heads.  I would love to have a camshaft capable of .700" lift to try in my engine. (Jon Kaase's heads for the 2015 EMC engine that he modified to upright ports supposedly flowed >330cfm) Joe-JDC

JDC

The Kaase Y was 709hp in a different configuration, after the competition.  http://jonkaaseracingengines.com/wp-content/uploads/2016/06/MM_July2016_HMMGarage.pdf
Plugging that into the formula works out to 344cfm.


Lawrenceville, GA

That is why I said >330 cfm.  If I remember correctly, the intake valve was 2.100" or so.  I have ported dozens of sets of SBF heads that flow over 330-340 cfm with 2.050, 2.080, 2.100, 2.135 intake valve sizes.  Many of the C302B style heads will flow in the 370+ cfm range with a 2.100" intake valve if they are ported right.  Joe-JDC

JDC