Don Terrill’s Speed-Talk

These are some original hi perf 409 heads that I ported. The intake flowed 323 cfm at .700 and were pretty quiet. Valve size is 2.275. Anyway, now that they have been run, there is a white residue in certain areas of the ports. All 8 ports have the residue in the same spots. I’m thinking these are areas of lower flow. Is that correct? What could be done to help even the flow more through the bowl area? Is the guide boss acting like a dam?

Nice to see a set of production heads with the valve guides done right

If I ever get time I want to try some experiments on my 340hp 409 heads I have laying around. I have one more 409 I can build now that i welded one block. I always love messing with 348/409 engines. Great job on the heads.

Thanks. I’ve run a best of 10.13 in a 3850 pound ‘63. Not bad for a antique!

I'd guess the white stuff is ash from reversion. Exhaust gases are going into the area just below the intake seat and burning any residual oil deposits in the area.

Nice port work btw.

Yeah, reversion.
You need to look at cam events.

Your intake valves should not have a angle on there chamber side face, they should be a chisel.

A angle on the face is the start of low lift low velocity reversion.

What is the current ID of the valve bowl and what is the port area on the crown of the short turn, and what is the minimum port area ?

Id be interested to know cam specs and valve seat angles.

I would like to know also what the average Exh to Intake flow ratio is within his range of valve lift from his Cam?

Well! After some more of investigation, it is exhaust but not reversion. The valve seat is slightly sunk where it is next to the exhaust valve on each cylinder. So basically exhaust was blowing past the closed valve at that spot. I posted a picture. The port area at the short turn is 3.135. The smallest port area is at the pushrod pinch and is 2.7. The highest point of the short turn is .600 above the valve seat. The throat is 2.04. The valve job is a standar 60/45/30. The intake valves have a 30 back cut. Exhaust valve is 1.75. I lost the flow numbers for the exhaust side. Anything I can do to improve these things or just leave well enough alone? These are my first full port job. I tried to follow basic rules and do no harm. Thes best numbers I’ve heard from these heads is around 330-335 @ .700 so I don’t think I did too bad. Just trying to get in the 9’s!

What MPH do you run?

My best is 132.2 mph when I ran the 10.13.

Well if your running enough lift to access atleast 310 cfm from your Intake ports and in that same lift range your Exh flow ratio is averaging 68% you should beable to make 700 hp, which should get you into the 9s if the intake manifold your running can pass that much cfm! ?

Those are real good numbers, especially since it looks like there is NO short turn height whatsoever.
Would love to velocity probe that port.

Always surprised at the number these kind of engines put out and in factory trim- what killed them in the day?

- just a stop gap engine on the way to something better?
- cost of engine?
- dead end due to rotating assembly weight?