Don Terrill’s Speed-Talk

In the old days when I used to run Comp cam stuff all the time, I would retard the cam timing 4° to get the cam closer to straight up when I would degree it in the engine. Did it work better? most of the time not on N/A engines but when running nitrous those cams retarded made way better top end po...

20240118_193812.jpg When engine dynoed pinch was 2.10" There is only 40 - 50 thou thickness on SSR, if I could lay it down more it might pick up some CFM. What it shows is you do not need a head that flows 300 cfm plus to make 570 ish hp. Smooth, quiet flowing port with appropriately sized cro...

When I was at dyno recently, Russ asked me if I was going to test MS109,I intentionally did not take any fuel with me. We talked about dart block dyno session with cast iron heads and he showed me a fair amount of data where the better fuel picked up anywhere between 10 - 25 hp . The strip dominator...

When engine dynoed pinch was 2.10"
There is only 40 - 50 thou thickness on SSR, if I could lay it down more it might pick up some CFM.
What it shows is you do not need a head that flows 300 cfm plus to make 570 ish hp.

A few port moulds between the 2 heads

With the Vic Jr it was down to 275 cfm @ 0.800"
This is earlier numbers, I changed the 60 deg cut to a 65 deg under the seat ,I am using no back cuts on these intake valves.
They are Manley Pro - Flow valves and not Race - Flow .

The alloy head had very average mid lift numbers and I used 2 x top cuts as the transition is very average, from the factory they have dug out around the seat ring. The fix I suspect is a bigger valve but I am not a fan of having a big valve in a small port,I think speed at the seat ring is pretty i...

The port architecture between the two heads are very different even though they are both Dart heads. Cast heads are a Wissota spec head that I originally bought to learn on,$300 AU each head bare delivered from Summit. The cast iron head has a better top cut to chamber transition and taller SSR so t...

You don’t think there is a possible advantage to a more controlled release of the combustion pressure through the exhaust throat? Maybe there is a thread you could start. Out of my league, but my thoughts are no, yes there's a balance to be had on overlap. But on Exhaust opening, late as possible, ...

SlowMalibu wrote: ↑Sat Jan 13, 2024 12:18 am What is an acceptable cam to rod clearance on a 383 SBC stroker ?

I have run 30 thou with no issue.
I like using a thin piece of solder and turning engine over by hand.

Having a short block, degree wheel, dial indicator set up on a engine stand is a good place to start,compare piston position to lift and duration, opening, closing etc.build some engines and dyno and track test and see how your car performs by rocking the curve up or down. My opinion is time is bett...

X 3 ,
Chris organised a couple of cams for me via google machine, very good to deal with,I hope he is still there.

Tom68 wrote: ↑Tue Jan 09, 2024 5:41 pm Pumping losses, open that exhaust valve as high as you can.

From what I have seen in these types of combinations are less exhaust lift more duration, smoother exhaust valve motion nets more power over the curve, again its application specific.

There is one other change on the exhaust side nobody has picked up yet, Hint - it's at 92%.???? I was going to say intake to exhaust flow ratio but without reading thrifty the thread again I don't see flow numbers for these heads. What was the difference in peaks between engine dynoed in first post...

1.5 on the exhaust... That raises a question I've had since the first I read about someone using less ratio on the exhaust as opposed to the intake. What's the logic there? Is it compensating for a cam spec or working with the specifics of a particular port? Ratio speeds up valve,depending on appli...