Don Terrill’s Speed-Talk

Are you sure those headers aren't too small?

PackardV8 wrote: ↑Mon Oct 11, 2021 3:05 pm

mn77spl wrote: ↑Mon Oct 11, 2021 1:20 pm Carbureted only.

One could accomplish the same IR tuning with a pair of the old 3-bbl Webers, but they're hen's teeth and learning to get them right is a too-long process.

How long would the runners have to be to effectively have the same isolation and ram tuning on a plenum as an IR setup? With a 5500 RPM limit, that wants 16" or longer runners, doesn't it? (84,000 / tuned rpm = runner length measured from the back of the intake valve to the start of the radiused entry of the runner with the port cross section area 83% of the valve area in the intake port and taper out at a 3.5 degree angle as it goes toward the entry of the runner.)

Couldn't he try the 3 x 2 bbl carbs he plans to use on the tunnel ram, on an IR manifold, instead of trying to find the Webers? Fabbing the IR manifold would be about like making 3 sets of 2-cylinder headers (he says naively ). Could even try that setup with gas and then methanol before making any other changes, to get some experience with tuning.

Individual runner carbs are much more sensitive to cam timing and the exhaust than carbs with a plenum between them and the cylinder.

2 things I like about your changes.
1. Alky.
2. 3 X2's
Alky will make more TQ Long stroke should like the Alky burn rate
3 X 2's = better distribution and the area of the N/S can be optimized for the area/flow of the jets. Keeping float level at optimum in the long pulls. Should result in a much better fuel curve on track.
The Alky may like a little more intake port/valve and more taper in the manifold runner.
You are dealing with 3.2 times the fuel volume with the same air when using the Alky.

I want to thank everyone with there feedback so far, in particular 'maxracesoftware' for all the time spent modeling. (BLSTIC I hope to see your analysis also.)

A couple of comments on what has been provided to date:

- Original valve size was 1.625 Int & 1.516 exhaust. Getting the port sizes up to where I would like them is a big challenge! I do however have ideas. . .

- A crank scraper is something I have thought about however I haven't come up with an approach. Perhaps a screen or louvered cover below exposed crank would be an improvement?
- If am am successful in fitting a 2.100 int (10% more area) with appropriate port sizes, I expect to be able to achieve a 10%+ improvement in flow. Can I then reasonably hope for a 10% improvement in torque? or am I dreaming

mn77spl wrote: ↑Tue Oct 12, 2021 5:47 pm I want to thank everyone with there feedback so far, in particular 'maxracesoftware' for all the time spent modeling. (BLSTIC I hope to see your analysis also.)

A couple of comments on what has been provided to date:

- Original valve size was 1.625 Int & 1.516 exhaust. Getting the port sizes up to where I would like them is a big challenge! I do however have ideas. . .

- A crank scraper is something I have thought about however I haven't come up with an approach. Perhaps a screen or louvered cover below exposed crank would be an improvement?
IMG_1425.JPG


- If am am successful in fitting a 2.100 int (10% more area) with appropriate port sizes, I expect to be able to achieve a 10%+ improvement in flow. Can I then reasonably hope for a 10% improvement in torque? or am I dreaming

Well, I'll preface by saying Engine Analyzer Plus (the one I have) is not a *true* simulation. It's a much simplified program built to be fast and easy, but not insanely accurate. I'm also not an engine builder, just a very analytical hobbyist that bought the program for funsies. That said, here's what I got as specified and then with it auto-optimizing simple stuff for average power across 3500-5500rpm.



That was just letting it auto-dictate cam duration, timing, exhaust and intake length and diameter. I won't say what they were because without wave modelling this program tends to lead you up the garden path especially with exhaust specs, which tend to affect the ideal cam, and so on. But it's accurate enough to tell that you need more head flow and trying to get more power without it will result in you having a bad time below 3500rpm if that ever happens. It also tells me that your engine was very well matched. Any fiddling with the easy stuff almost always resulted in going backwards.

Also the program specifically noted the high port velocity.

I'll see what happens later with increasing valve size and head flow by 10% in all areas, but for now I have some of my own study to get on with.

Since your banging on the sonic brick wall now at 5500 rpm with your valve size and port area, my guess is that stepping up to a 2.100" valve and it's added curtain area will only serve to pick up mainly low to low mid lift flow.
With no increase in the size of your minimum port area this extra flow may be counter productive in terms of port air speed and hp numbers, or you may just get some added torque down low where it does not matter.

Original valve size was 1.625 Int

Original valve size was 1.625 Int .... and you were able to install a 2.000" inch Intake Valve
and not hit water .... that's amazing !

and now you are thinking about installing a 2.100" Intake Valve ,
i don't see how a Cylinder Head could have so much metal + have enough Valve Guide CenterLine spacing
to install a 2.100 side-by-side with a 1.650" Exhaust Valve

your Cylinder Head seems like it has not much of a waterjacket , if thats possible to use those larger Valve diameters .

No known Cylinder Head i've ever seen would this be possible to do !
.... likewise above , same thoughts i have for the Intake Port itself !

maxracesoftware wrote: ↑Wed Oct 13, 2021 3:58 pm

Original valve size was 1.625 Int

Original valve size was 1.625 Int .... and you were able to install a 2.000" inch Intake Valve
and not hit water .... that's amazing !

and now you are thinking about installing a 2.100" Intake Valve ,
i don't see how a Cylinder Head could have so much metal + have enough Valve Guide CenterLine spacing
to install a 2.100 side-by-side with a 1.650" Exhaust Valve

your Cylinder Head seems like it has not much of a waterjacket , if thats possible to use those larger Valve diameters .

No known Cylinder Head i've ever seen would this be possible to do !
.... likewise above , same thoughts i have for the Intake Port itself !

It's a tractor engine, usually lot's of meat

I sprung for PipeMax 4.70 in order to help me look at some of the ideas suggested. I have some questions:

- What valve or cam lift are the timing recommendations referenced to?

- What engine configuration is assumed for the estimated power & torque outputs, "Race Engine • Mid-Range Peak TQ • Hi RPM Peak HP" ? or ?

- I would think the "Diesel Flat Chamber . . ." would be a better match for my engine as opposed to a "Large Open Chamber Wedge". Substituting the Diesel chamber reduced the recommended overlap. Any thoughts on this? Thanks in advance!

Can't comment on Pipemax. But I am familiar with that head and you are on the right track with valve size. That port in a filled water jacket configuration can flow easily 370cfm. My only comment is it needs more stroke...just under 5". Oil galleys may need to be relocated

- What valve or cam lift are the timing recommendations referenced to?
- What engine configuration is assumed for the estimated power & torque outputs, "Race Engine • Mid-Range Peak TQ • Hi RPM Peak HP" ? or ?
- I would think the "Diesel Flat Chamber . . ." would be a better match for my engine as opposed to a "Large Open Chamber Wedge".
Substituting the Diesel chamber reduced the recommended overlap. Any thoughts on this

i had originally "Diesel Flat Chamber" choice but i changed it to "Large Open Chamber Wedge"
thinking you might have found a regular "Spark Ignition" cast-iron Cyl Head custom replacement .

Substituting the Diesel chamber reduced the recommended overlap. Any thoughts on this

for the "Flat Chamber" or "Diesel Flat Chamber" , this was setup for Diesel Fuel with Turbos with hi Compression Ratios like 18:1 to 25:1
so the recommended Overlap Period is much less, and the LSA is greater .
....... i'd leave that Chamber choice setup to either "Small" or "Large" Chamber Wedge
as its correct for your application

What engine configuration is assumed for the estimated power & torque outputs,
"Race Engine • Mid-Range Peak TQ • Hi RPM Peak HP" ? or ?

that Choice seems to me best fits your Engine application,
and calculated PipeMax Data .

- What valve or cam lift are the timing recommendations referenced to?

referenced to most of your PipeMax inputs and choices .

.... more Info on how you can use PipeMax v4.70 more accurately :
1]= input actual Weather conditions into PipeMax for each individual Dyno test
......this is very critical !!! , a lot of PipeMax Users don't seem to bother inputting Dyno Test Weather conditions
if you want higher accuracy .. you must input actual Weather conditions for each individual Dyno test the time and date it occured !

2]= if your Dyno measured Fuel Consumed in Lbs/Hour , then "after" PipeMax calculates your current Weather specs you previously entered ,
then adjust PipeMax's Air/Fuel Ratio a little amount at a time until you force PipeMax to exactly matchup
to "both" your Fuel Consuumed Lbs/Hour and your BSFC numbers .... this should then be the real Air/Fuel Ratio your Engine is seeing
and it should matchup to other accurate Air/Fuel Ratios Meters

3]= install a Plenum Vacuum fitting to measure Plenum Vacuum during your Dyno tests
be sure to only measure Plenum Vacuum itself , and never measure individual Runner Vacuum with a Plenum

if you are unsure how to do all this ,
send me your Dyno Sheets with Weather conditions ,
and i can make everything calculated come out more accurate than i've Posted .
Likewise , i would need complete Flow Sheet Data too .

TMP Carbs wrote: ↑Wed Oct 26, 2022 5:07 pm

Correction: ... over 300 cfm per hole.

@28" ?