Don Terrill’s Speed-Talk

ok.

Against my better judgement I will suggest some extra work for Randy on teardown. I would go over the valvetrain very carefully and look for any signs of distress before adding lift, duration, load or rpm to the mix. The engine sounds great and makes excellent power as it is. I would measure all the guides with a guide dial bore gauge, measure each valve stem and look for any unusual wear. The springs need to be measured for height and compressed load against what they were installed. Locks and retainers and faces of valve springs can give clues the valvetrain is in distress. Rocker seats, lifter rollers, cam wear, pushrods may have signs of an issue starting up. I really hope it is all in great shape and you can turn it up more. Thanks, Charlie

Carnut1 wrote: ↑Fri Oct 19, 2018 2:29 pm

CGT wrote: ↑Fri Oct 19, 2018 8:38 am

randy331 wrote: ↑Thu Oct 18, 2018 9:11 pm bigger custom headers, switching the ex valves out to titanium and trying either a little faster ex lobe or higher ex rocker ratio

"The better the Exh port works overall and especially in the .050" to .300" lift range the smaller the Exh lobe you will need to make power!!!!

Compression ratio / cylinder pressure are big factors that can help a under performing Exh port to work as needed during the blow down cycle, that being getting a good size chunk of the spent gasses out of the motor even before the piston starts its way up the Bore on the Exh stroke!"

randy331 wrote: ↑Thu Oct 18, 2018 9:11 pm if 30* seats and bias ports and big low lift flowZ works better

" Use the stock exit size more efficiently. The ssr needed bias and reshaping."

IM OUT!!!!!

MOO3.jpg

I will bite, how would you improve it vs. my method?

The question isn't "if" I can increase the ex flowz , but would that turn into power ?

I've done things to ex ports that showed nothing on the flowz bench, but netted a power increase.
That's the hard part,..figuring out what flowz bench gains are power gains.

Randy

Sorry to be confusing Randy but the exhaust flows was really directed to cgt on a post I did for DV on a different thread.
As far as your exhaust on the 421 I bet you made it on the small side but it obviously has good efficiency. I am interested if you are thinking of a larger header are you rethinking the exhaust port design? Thanks, Charlie

Carnut1 wrote: ↑Fri Oct 19, 2018 8:55 pm Sorry to be confusing Randy but the exhaust flows was really directed to cgt on a post I did for DV on a different thread.

So how did your exhaust flowz equate to power in the other thread? They flowed more?

CGT wrote: ↑Fri Oct 19, 2018 9:57 pm

Carnut1 wrote: ↑Fri Oct 19, 2018 8:55 pm Sorry to be confusing Randy but the exhaust flows was really directed to cgt on a post I did for DV on a different thread.

So how did your exhaust flowz equate to power in the other thread? They flowed more?

That example has not run yet as you clearly pointed out. I can point to the early 90's and my first sbf build that had trouble sealing, and oiling. Those heads came off several times as issues were addressed. Each time the heads came off I studied the carbon patterns of the burn and did more porting work. As it progressed the torque band expanded and pulled a bit better. This was a street build but it did make it to the track a few times. We started in the 13's and had head gasket issues. Third time at the track was 11.00 at 126 on street tires. I have watched the pull videos and with the rpm band I would not be afraid of a few more cfm exhaust flow as long as the exhaust port cc doesn't grow much. Especially if you up the header size. Thanks, Charlie

So how much CFM on the ex side do I need on the 421 ?
Is more always better ?

It seems I end up with very similar ex CFM on most 23* SBC ex ports.
I've seen it support 750 HP in the case of my 421 and the same cfm make great power and power curves on lesser engines even with 20* more ex duration. So how much is enough ?

If you look at 23* ex ports there really isn't much difference. Dart puts the same ex port on the 200cc - 215cc - and 230cc heads. Why?

Randy

I will guess you have this exhaust about 230 cfm@.7" with no pipe on the bench. Will more flow equal more power? I think it may help if pumping losses are reduced and if the airspeed within the port doesn't drop too low due to increasing port csa. Problem is your heads are really working well now so getting gains are that much harder. Did you develope the ports with Pitot airspeeds? Are the ports small and fast? A close inspection could reveal areas that may like more area. Have you decided if the headers will go up in primary size? Dart 215 heads flow about 260 cfm 200 cfm stock. For average builds that is probably fine. Thanks, Charlie
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randy331 wrote: ↑Sat Oct 20, 2018 10:17 am So how much CFM on the ex side do I need on the 421 ?
Is more always better ?

It seems I end up with very similar ex CFM on most 23* SBC ex ports.
I've seen it support 750 HP in the case of my 421 and the same cfm make great power and power curves on lesser engines even with 20* more ex duration. So how much is enough ?

If you look at 23* ex ports there really isn't much difference. Dart puts the same ex port on the 200cc - 215cc - and 230cc heads. Why?

Randy

If Darin Morgan and Judson? from SAM have any merit they seem to say what modern publish info says... Ex should be small and quiet regardless of CFM. But I guess you already know that.

I think it was Darin that said the exit should be in the 105 to 108% of valve size as a reference, I hope I said that correct.

My Garytheory thinks it may be possible to better develop the ex port with a DB or Frequency meter.

If you look at 23* ex ports there really isn't much difference. Dart puts the same ex port on the 200cc - 215cc - and 230cc heads. Why?

Randy

probably because exhaust/intake % ratio does not mean as much as people think,Randy you have proved this to be true on more than one occasion especially regarding exhaust duration and % ratio
Steve c

[/quote]
If Darin Morgan and Judson? from SAM have any merit they seem to say what modern publish info says... Ex should be small and quiet regardless of CFM. But I guess you already know that.

I think it was Darin that said the exit should be in the 105 to 108% of valve size as a reference, I hope I said that correct.

My Garytheory thinks it may be possible to better develop the ex port with a DB or Frequency meter.
[/quote]

Gary,
you are correct with Darins quote,
i just retested my 165cc dart heads after back from machine shop had radius seat valve job on the exhaust,i blended the throat to seat transition.polished the exhaust SSR smooth,the throat is small at 85% of the 1.5''valve but i want room to grow if required.i destroyed a test exhaust port by grinding the exhaust guide boss out and making the port to big,the sound of the port was terrible,it had turbulence from .200''lift upwards and i was lost.
i came across Darin Morgans post on exhaust port so i wanted to apply his thoughts to my port.100-105% of the exhaust valve CSA
300-320 ft/sec at the flange
i made my port slightly wider from the guide boss out to the opening as i found the air speed to be 350 ft/sec @ 28'' in this area
the air speed there now is 310ft/sec and 300 across the top of the opening with a pipe on.
i have found the air is more stable with the pipe on and i probe through 2 x holes in the pipe with my exhaust pitot tube.
as you guys are aware i have very limited experience so i am just telling you my findings on my head on my bench.
Darin Morgan has also stated that a exhaust port in a high compression,high rpm application with no exhaust system is completely different configuration to a standard 23 deg style head.
Randy says he is bumping up compression,rpm,lift, duration and possibly a different head configuration.
Darin stated in his audio disc that in a pro stock exhaust port does not flow any air when it cracks off the seat. why ?? i have no clue
Randys 421 is not a 500 inch pro stock engine but he might be developing a exhaust port/tract using similar ideas.

The sb2.2 heads on the current engine in my car makes 882, the ex flow 260, so how much do you really need?

You mentioned your stepped headers and of possibly building a new set but you did not mention collectors.

I had just read this bit about mid-range torque increased by Venturi Collectors and thought you might benefit reading it also.

Just an idea, cheap enough to try.

http://www.headersbyed.com/hc_ventext.htm

Also https://www.google.ca/search?q=burns+ad ... H7RqvEmouM:

steve cowan wrote: ↑Sat Oct 20, 2018 5:59 pm i came across Darin Morgans post on exhaust port so i wanted to apply his thoughts to my port.100-105% of the exhaust valve CSA
300-320 ft/sec at the flange

I think he's stating that as a safe place to be, or start out, not that's the ideal place for all engines.

steve cowan wrote: ↑Sat Oct 20, 2018 5:59 pm Darin stated in his audio disc that in a pro stock exhaust port does not flow any air when it cracks off the seat. why ??

Probably the 65* ex seats.

Randy

MadBill wrote: ↑Thu Oct 25, 2018 4:57 pm Also https://www.google.ca/search?q=burns+ad ... H7RqvEmouM:

Good link Bill,thanks
there is a life time of reading just there