Don Terrill’s Speed-Talk

CGT wrote: ↑Thu Jan 18, 2018 10:06 am

MadBill wrote: ↑Thu Jan 18, 2018 9:04 am Big Joe reported up to a 50 HP gain with pan vacuum on an big BBC with rings optimized for it. I've several times seen +12-15 on ~ 450 HP 6500 RPM SBCs with typical circle track ring packages.

It's always fun to me to try vacuum on the dyno. The results are sometimes really inconsistent. There is one particular motor (Randy knows about) that has an allergy to vacuum. . It should really respond to it in theory, but is hard headed and doesn't. It tends to pick up the same amount of power that it takes to spin the vacuum pump

Yea, I'd like to know what's going on with that engine for sure.
It's been tried 3, maybe 4 times on it, belt on nothing, belt off nothing, and one time with small oil pan, still nothing.
Tommy Boy picked up 15 HP with the same pump on it and similar vacuum. (15"-16")
Be interesting to raise oil pressure on it and see if vacuum still had the same results.

Guess if I figure it out I can repeat it on others and save money on vacuum pumps.

Randy

Short stroke motor?

gmrocket wrote: ↑Thu Jan 18, 2018 7:24 pm Short stroke motor?

4.031 x 3.75" stroke

Randy

For shits and grins, did you guys throw an open spacer on the dual plane? I'm wondering how much that may have helped your 40 hp deficit.

RevTheory wrote: ↑Sun Mar 11, 2018 12:49 pm For shits and grins, did you guys throw an open spacer on the dual plane? I'm wondering how much that may have helped your 40 hp deficit.

No spacer plates were allowed in competition...so no.

Yeah, I saw where they weren't allowed, just wondering if you threw one on out of curiosity.

RevTheory wrote: ↑Sun Mar 11, 2018 2:13 pm Yeah, I saw where they weren't allowed, just wondering if you threw one on out of curiosity.

Wasting dyno time trying things that aren't allowed is a good way to lose. Even trying the 2-plane was a waste of time. We all pretty much knew it wouldn't be better, but it was even worse than we thought.

Rick

Great engine and great job!

That said, can anybody tell me how the results would change if a 4.155" b x 3.25" s = 352.5" engine was made using a 400 SBC block and a 327 crank.

I think that "T" might be down due to the shorter stroke, but that Hp should hold up well. Jmho is all though, no data..

pdq67

CGT wrote: ↑Thu Jan 18, 2018 10:06 am

MadBill wrote: ↑Thu Jan 18, 2018 9:04 am Big Joe reported up to a 50 HP gain with pan vacuum on an big BBC with rings optimized for it. I've several times seen +12-15 on ~ 450 HP 6500 RPM SBCs with typical circle track ring packages.

It's always fun to me to try vacuum on the dyno. The results are sometimes really inconsistent. There is one particular motor (Randy knows about) that has an allergy to vacuum. . It should really respond to it in theory, but is hard headed and doesn't. It tends to pick up the same amount of power that it takes to spin the vacuum pump

On my 650 hp bracket engine, used rings with an 8 pound oil ring, comparing open breathers to turning a vacuum pump and having 12" of crankcase vacuum was a virtual perfect graph overlay to about 6200, then a cool 2 to 3 hp gain above that. Pretty damn glad it was a loaner model. When I put it back on the dyno later this year I'll be trying my personal headers with an evac u pan setup to see how it compares.

That same pump setup made 15 or so more on the 372 it came on. Vacuum pumps, like so many other parts or tuning adjustments, are a trial and error deal rather than guaranteed gain.

Rick360 wrote: ↑Sun Mar 11, 2018 2:17 pm

RevTheory wrote: ↑Sun Mar 11, 2018 2:13 pm Yeah, I saw where they weren't allowed, just wondering if you threw one on out of curiosity.

Wasting dyno time trying things that aren't allowed is a good way to lose. Even trying the 2-plane was a waste of time. We all pretty much knew it wouldn't be better, but it was even worse than we thought.

Rick

How worse was it?

pdq67 wrote: ↑Mon Mar 12, 2018 12:17 am Great engine and great job!

That said, can anybody tell me how the results would change if a 4.155" b x 3.25" s = 352.5" engine was made using a 400 SBC block and a 327 crank.

I think that "T" might be down due to the shorter stroke, but that Hp should hold up well. Jmho is all though, no data..

pdq67

My opinion is that the results and torque curve would be very, very similar.

pdq67 wrote: ↑Mon Mar 12, 2018 12:17 am Great engine and great job!

That said, can anybody tell me how the results would change if a 4.155" b x 3.25" s = 352.5" engine was made using a 400 SBC block and a 327 crank.

I think that "T" might be down due to the shorter stroke, but that Hp should hold up well. Jmho is all though, no data..

pdq67

I find this interesting, however I would like to take this further than what dyno difference their might be. I wonder with a bigger bore and shorter stroke could you take advantage off any more head/cam than used considering the constraints and goals of the competition? Would gladly take a pm to keep from hijacking... Thanks for sharing the results and congratulations on a nice build.

tt 383 wrote: ↑Mon Mar 12, 2018 9:07 pm I find this interesting, however I would like to take this further than what dyno difference their might be. I wonder with a bigger bore and shorter stroke could you take advantage off any more head/cam than used considering the constraints and goals of the competition?

We tried heads that flowed considerably more and were bigger csa and volume with bigger valve, but it made less average power and wasn't better at any rpm tested.

The bigger bore would present some options for posible advantages but most likely off set by the negetives of the bigger bore and set deck height.

Not saying there isn't anything at all to bore/stroke combos at the emc, but it's well down the list.

Induction tract size/shape runs the show.

Randy

The bigger bore may let the head flow a little more, the bigger bore may have little more quench, the shorter stroke may have less friction, the shorter stroke may have less windage. If it all adds up to more points, who knows.

77cruiser wrote: ↑Mon Mar 12, 2018 9:39 am

Rick360 wrote: ↑Sun Mar 11, 2018 2:17 pm

RevTheory wrote: ↑Sun Mar 11, 2018 2:13 pm Yeah, I saw where they weren't allowed, just wondering if you threw one on out of curiosity.

Wasting dyno time trying things that aren't allowed is a good way to lose. Even trying the 2-plane was a waste of time. We all pretty much knew it wouldn't be better, but it was even worse than we thought.

Rick

How worse was it?

With the 2-plane average HP from 3500-6800 rpm was down 12-13hp and peak hp was down 40hp.

Rick