Don Terrill’s Speed-Talk

So how about it? Is raising the short turn 0.100" going to make a huge difference on a 600hp NA motor? 0.200"? More importantly for my application, will it allow me to run higher velocity over the short turn and stave off the separation issues seen with a denser air/fuel charge in boosted applications? Pipemax wants me to have a 2.9" average CSA to get down to 260fps average velocity. That's pretty big for these ports, but I think slowing the air over the SSR is going to be critical in staving off separation issues with this shallow valve angle. Am I all wet on that?

I can't see how this can be accomplished without Pitot mapping. If you get a Pitot baseline with the original ssr and can significantly lower the speed of the air across the apex you can expect the air to stay attached better and have a port that will flow to a higher rpm. Expect, does not mean that will happen! This will need testing, testing, testing. Thanks, Charlie

Rick Finsta wrote:So how about it? Is raising the short turn 0.100" going to make a huge difference on a 600hp NA motor? 0.200"? More importantly for my application, will it allow me to run higher velocity over the short turn and stave off the separation issues seen with a denser air/fuel charge in boosted applications? Pipemax wants me to have a 2.9" average CSA to get down to 260fps average velocity. That's pretty big for these ports, but I think slowing the air over the SSR is going to be critical in staving off separation issues with this shallow valve angle. Am I all wet on that?

This is where I would call Darin Morgan at R&M with credit card in hand for a phone consultation.
Raising the runner to get a better approach at the short turn make since but raising the short turn seems like your back where you started.

You can get his contact info here.
viewtopic.php?f=15&t=49867&start=30

Just got off the phone with Chad Speier, who has the head, and sounds like we'll use this thread to communicate on this project so hopefully we can share some good information.

In the meantime, how about this... when folks refer to "dead areas" in the port, or when it it obvious on the bench that less air is moving on the port floor relative to the rest of the port, does this change the CSA that the port "sees?" Is this a matter of the mass air flow having a gradient in the port? Is this a complete figment of the imagination?

If Your entrance can be raised .600" ( while retaining the needed area by the push rod) and you can blend into the existing crown, your runner is straighter. "If" you can contour the roof to work with that floor, you should have a better port. If area allows at the crown that extra .100" could help in shaping the turn also. If area is too tight there, I'd just butt up to the existing crown. You might consider using some epoxy to help the blend from the weld to the existing crown. When happy with the shape, some 2 part automotive clear-coat will seal it. We've got some over a decade old done that way without problems.

Looks a lot like the way the sbc Buicks were raised 30 years ago. We had a set from Nickens that were filled and raised and another set that were in stock location. Both flowed about the same. The filled set made around 30 hp more.

Old School wrote:Looks a lot like the way the sbc Buicks were raised 30 years ago. We had a set from Nickens that were filled and raised and another set that were in stock location. Both flowed about the same. The filled set made around 30 hp more.

Funny you say this. I'm working on these as I type. Old Buicks that the plastic was falling out so I get the pleasure of fixing them.

Who originally did those? The cathedral top is different than ours was. Looks, if that means anything, like it would be an improvement?

Billy

Old School wrote:Who originally did those? The cathedral top is different than ours was. Looks, if that means anything, like it would be an improvement?

Billy

Bud Harper

Hell, Chad I think I'm going to need the roofs opened up before I can get the torch in there if the floor is coming up that much! I like it!

Rick Finsta wrote:Hell, Chad I think I'm going to need the roofs opened up before I can get the torch in there if the floor is coming up that much! I like it!

Your probably right. I want the floor and roof to converge at the apex. We can make the floor flat like you have it, but this is better..

I'll go ahead and buy a few more pounds of filler wire...

Honestly, the pushrod pinch was a PITA to get around with the torch so it may be easier for me to weld the tops by the rocker pads, then run a program to open up the roofs, then I can fill the floors and get them back your way for finishing?

Dammit, now I'm reading about pressure recovery and looking at the waveguides on the JBL reference monitors here in my studio...

These chambers look like bathtub bowls; how much do I care about pressure recovery on a forced induction motor? I think the answer is "stop whining and get the torch out."

Alright, got the water cooled setup running and finally hit the thermal cutoff on this welder LOL. I really need a Helium mix for this so that is coming next. $150 for a 125CF tank! Yikes. They want like $500 for a 300CF of 25/75 He/Ar mix, though. I think I'll get a few check valves and a Y connector and call it a day. Makes me wish I had a way of pulling the last bit out of every "empty" tank of Helium I send back here at the lab.

First runner roof welded up... you can see what the cleaning action brought to the surface on the inner runner. I need to hit that with a burr and then start laying rod. After a pass or two more crap will be getting in the way and I'll need to hit it with a burr again. Not easy but I'm learning a lot.



I need to raise those spring seats - what is the best way to get those guides out of there? Then I can turn a stainless or copper bar in the lathe that will be a light slip fit and I can weld up around them.