I’ll try to summarize where it looks like we’re headed.
Think of this as an essay exam, proctored by Professor Fordboy.
I had the head flow benched last week. Here’s a quick rundown – intake, cylinder 1.
Lift cfm
.100 44.0
.200 87.6
.300 111.7
.4500 124.1
.500 125.6
Mel C&S tested it all the way to .600 (127.9 cfm), but it’s pretty clear that the party is winding down at ~.450, which I believe is well beyond the demands of the cylinder at that point.
Compared to one of David Vizard’s heads in “the Bible”, this one is flowing a bit better at lower lift, although his has more overall flow at higher lift. That’s okay – the head he built was for a 1300 - we’re talking about a 61 CI engine, which is less capacity than 3 cans of Schlitz.
After great discussions with Fordboy, what I’m thinking is that the curse and the advantage of this configuration with a 2.45 Rod/Stroke ratio is this – While we need to spread the LCA’s to clear the piston and valves at TDC (due to the enhanced relative dwell = less overlap), the relatively fast movement of the piston mid-stroke combined with the longer relative dwell toward BDC should enhance cylinder filling. Key, as FB noted, will be throwing the valve open as quickly as possible.
Right now, the lift acceleration rate is about as fast as can be built into an engine with lifters this small. But seeing as the head starts to get limited at ~.450, there’s no real need to open it much further, which hopefully will let us adjust the lobe nose and backside of the lobe in a way that will allow a less radical deceleration rate. The less movement, the less movement one must control.
Also, it turns out that the 1.5:1 rocker ratio is a bit steeper than advertised, so we’ve got a bit more room to play with than calculations indicate.
Mel is checking the head face thickness, so we should know what we can realistically shave off of this thing in short order.
Topic: Milwaukee Midget (Read 3284818 times)