Don Terrill’s Speed-Talk

This is a set of 601 casting 305 heads I've been dragging around with me forever. Stock 1.84/1.50 valves, 56cc chambers, amateur hour light bowl blend and general port cleanup, single angle 45* valve job. I've got about 2 hours in one head...time mostly spent cleaning out dirt dauber nests and spiders and a lot of dirt/crud.

Intake @ 28"

.025...15
.050...31
.100...58
.150...83
.200...100
.300...142
.400...177
.500...201
.550...210
.600...217
.630 (coil bind on the test spring)...217

Exhaust @ 28", no pipe

.025...13
.050...23
.100...46
.200...81
.300...106
.400...130
.500...143
.600...155

Exhaust @ 28", no pipe, switched to undercut stem 1.50" valve

.025...14
.050...26
.100...49
.200...88
.300...118
.400...141
.500...153
.600...164
.600 w/pipe...178
.650...172
.650 w/pipe...191

The ports were smooth and quiet at all lift points, and port speeds wasn't too crazy either. No port matching, or pinch opening, etc. I mostly just worked on the short turns and cleaning all the casting crud out of the ports, and blending everything in. It was also interesting to see the difference the undercut stem made on the exhaust side.

It was also sickening to see what a quick and dirty amateur job on these 305 heads did compared to several sets of ford heads that I have spent a LOT more time hacking on

travis,
have you cc'd the ports??
interesting with undercut stem as i have 2 x sets of Dart heads here that dont like the undercut valve.

steve cowan wrote: ↑Mon Dec 02, 2019 12:04 am travis,
have you cc'd the ports??
interesting with undercut stem as i have 2 x sets of Dart heads here that dont like the undercut valve.

I haven't cc'd them yet, although you can easily see that they are much bigger everywhere than any of the ford smogger stuff. I've read they typically run in the 165-170 cc range.

I have also read that some heads don't like the undercut stems (can cause turbulence), but these clearly did. Now I want to try a set on the intake side

my Dart 165cc cast irons flowed 138cfm @ 0.0500'' @ 28'' out of the box. 65cc, throat was 84%
with a bit of trial and error i got 177cfm @ 0.550'' @ 28'' using a undercut stem 7* manley valve,had turbulence up tp .400'' lift but ran it at the time cause thats all i had.
motor came apart couple of months ago and i am throwing my junker 327 together with the little Dart heads.
seats and guides are in good condition,leaving intake side alone just playing with exhaust side.
out to 73cc,throat to 86.5%,still 1.5'' valve but tested a few valves and found the Manley 10* solid stem tested nice.
went -
200''-115cfm
250''-149cfm
300''-170cfm
350''-182cfm
400''-192cfm
450''-198cfm
500''-202cfm
550'-'203cfm
600'-'206.5cfm
650''-208.5cfm
@28''with pipe
pitot on roof with pipe
370ft/sec on cylinder side of roof
350ft/sec centre and other side of roof of port.
tested up to 40'' smooth no disturbance,
just redone throat to 88%
thin guide boss more
have not retested yet.

You need more angles. Clean up the bowl with 60 and 75 deg cutters/stones and a 37 deg top cut. Check the contact point on the valve face. Back cut the intake valve at 30 deg to within about 0.020" of the contact point, then recheck the flow.

I'm sure that others can add more to that, but that worked good on the restricted intake claimer engines that we used to run in the lower division cars.

The arc, or lack of on the long side of the Exh valve bowl around the valve guide as a big influence only a undercut stem pays off across a good range of valve lifts.
Many times even bullet nosing over the valve guide will drop off low lift flow numbers .

Try doing some flow test using .025" step points up to .100" lift.