Don Terrill’s Speed-Talk

One of the many used equations for sizing a cylinder head based on the available cfm deals with how much air flow is needed at 76 degrees ATDC to meet piston demand. CI X RPM X .000978474, Divided by the number of cylinders. Video from inside a combustion chamber shows flow rushing in at TDC. https...

If we have any members close to Columbia, MO, I might be able to find his address. I’ve got it written down somewhere. I’ve been to his house quite a few times, even helped work on his Camaro quite a bit. I had kind of lost touch with him when I left Missouri about 10-12 years ago

I’ve got a Jones 264/268@.006, 218/222@.050, .544/.544 lift, 112+3 HR cam. Figuring mid 9’s on compression, dual plane and 670 Holley, 2000-2200 converter, 3.55 gears, in a 4500-ish pound F150

Am I reading that right? 159cc?? Stock they are like 124cc iirc.

The speeds was pretty even everywhere except for the floor...there was a little variation from side to side but from what I remember it was the center of the floor that was the fastest. I guess as long as I keep it under a .650” lift cam it should be ok :lol: The conversion formula converts the mano...

It was reading 14”, so using the conversion formula provided with Gary’s bench, it calculated to 415fps.

What little I know on this subject, the numbers seem reasonable. There is still a pretty significant taper on the floor (the roof was straightened out which helped quite a bit).

I was pondering this on the way to work tonight... If your testing a head at 10” depression, that goes turbulent somewhere between .650 and .700” lift...what happens if you test on a bigger bench at 28”? Would it go turbulent sooner (lower lift point)? It seems to me that it would, considering your ...

215 cfm @ .5" is a good number. I think you should finish them and run them. That is the plan. Now just to duplicate this work 14 more times lol Uh..... 7 more times? 7 more intake ports, 7 more exhaust ports :wink: Or 7 more pairs. However you want to look at it. Thanks for your help as well ...

Carnut1 wrote: ↑Sun Jul 07, 2019 6:51 am 215 cfm @ .5" is a good number. I think you should finish them and run them.

That is the plan. Now just to duplicate this work 14 more times lol

mag2555 wrote: ↑Sun Jul 07, 2019 5:52 am Nice work!
Looks like the intake ports will be good for .550" lift

Thanks! It’s been a very interesting learning experience

Intake port, Round 2... .100” 66 .200” 129 .300” 178 .400” 212 .500” 218 .550” 223 .600” 226 .650” 229 .700” port went turbulent and wouldn’t hold a steady reading. Doesn’t seem too bad for a 152cc port. Port speed at the fastest point was getting it on though...415fps :shock: Many thanks to Gary C....

I was inquiring about valvetrain pieces with an unnamed valvetrain specialist company, and they were adamant about not using 10* locks on street motors, swearing that 7* locks “lock tighter” at street level spring pressures. I’ve used 10* stuff many, many times and have never had any issues. Is this...

Is there anybody out there that will make a one off set of spring locators for a reasonable price? The heads I am working on have a 1.46” spring seat, and a 0.625” guide OD. Everything I find that fits the guide is 1.550” or bigger and that won’t fit without seriously cutting the heads screw in core...

I keep seeing this pop up from time to time, especially in regards to chamber deshrouding work and bowl porting. What is it, what does it do, how do you measure it, etc?

I know of a few situations with similar running characteristics. Basically ran fine to a fairly low rpm, then it just kinda lays down as you open the throttle more. Both BB mopars. In these instances it was the cam installed 2.5 teeth advanced. Dot on top gear straight down.......keyway in crank st...