There are only crickets in here...

[BlackBart]

Ohh, I see, that's pretty trick. What's the advantage of that? Less steep cam lobe ramps for the lifter to follow?

Here's a reference to Phil Singher engine designs, in a P1800 column....

"I have a lot of respect for the stock D grind camshaft that came in these B20s but I wanted a little more poop. 30 years of technology was sure to offer improvements in valvetrain technology over what Olaf originally put together. Unitek offers a cam with 272 degrees of (advertised) duration, .472 valve lift with stock rockers and a slightly beefier duration than the stock Dgrind or the Street Performance cam. Phil was having huge success with a similar cam with 296 duration so I took the plunge and purchased it. In addition to the cam I purchased valvesprings, retainers, lifters and steel timing gears from Unitek."

This is really interesting - I'm learning a lot....
http://www.1800philes.com/engine_article.html

[volvolugnut]

Thanks for finding all this cool stuff.
Chevrolet motors still use push rods and rocker arms to drive the valves. One of the hot rodding tricks is to change the rocker arm ratio for more valve lift. When you have more lift, you need stronger valve springs. And maybe double springs per valve. All to get more air in and out of the cylinder.
volvolugnut

[volvolugnut]

I went back and looked at all the restoration photos. I noticed at one point it said 12 years of work.
volvolugnut

[BlackBart]

I didn't know about the rocker arm trick - that's what I get for being an overhead cam guy!

We all thought the smallblock's day was over, and now look at what Chevy has done with that engine - compact, light, incredibly powerful, totally reliable, cheap. You can't poo poo that.

Yeah, I saw the long project time, but also saw he parked it for 10 years. So I'll give him a 10 year discount, which makes it very impressive! The metal work, the painting, the plumbing, the finishing - it's all top notch.

When I see these projects with all new, plated hardware - everywhere - it hits my dangerous perfectionism buttons. But you know me (maybe you don't!), I'll take them to the wire wheel, clean them all up, and put them back on! It's gonna get driven. It's gonna get dirty. And that will be painful when all those new plated bolts underneath are covered with grime.

[volvolugnut]

I have never owned or built a performance engine (except the stock T5!) but I like to read about how engines of any brand are modified to increase power. The basic concept never changes - make it flow lots of air, stuff the air with compressors or turbos, add lots of fuel and try to keep it together long enough to do something with it.
volvolugnut

[BlackBart]

Right - it’s an air pump.

What I don’t fully understand is the invisible dark science of intake charge velocity, pulses, resonance, air column mass, intake runner tuning for different rpms, turbulence, valve shrouding....all of that!

On my high school Bronco 289, most kid’s plan was to throw on an Edelbrock manifold, a Holley, and headers, without really understanding what we were trying to accomplish. On a stock engine, stock heads.

[volvolugnut]

I think you understand the subject better than you realize. You are listing many of the factors the professionals try to alter to get the most power. I do not understand them all either.
What I do understand is the basics - bigger is better than smaller, straight is better than bent, and more fuel is better. However, if you get too big on the intake or exhaust manifold, the flow may be slow and performance doggy. There are calculation formulas for the size and length, but they assume straight and uniform diameter and one RPM. The valve head and throttle plate are restrictions that can't be removed.
When some of the posts here talk of increasing the throttle plate size they are reducing a bottleneck in the flow. When the Volvo engineers selected the stock throttle plate, they likely compromised for space required, weight and cost.
When American engines have intake and exhaust manifold changed and larger carbs added, they are trying to increase flow and fuel. If you go too much larger or too much fuel, you get doggy performance, especially when the weak link is the stock heads. Unless someone else has tried the change with success, you may not have improvement. You would have, as an old boss called it (and always tried to avoid), a science project.
volvolugnut

[BlackBart]

Right!

I read about unskilled guys like me with a burr bit, hogging out all kinds of material to "port out" a head and making a complete mess of it! It's already been done many times by people who know how! I would send mine to someone sharp and then do the rebuilding / reassembly myself.

There's a guy in the BMW racing world in FL, who builds engines for the Spec E30 classes. He's built hundreds of engines. He has records of nearly every M20 head he's ever built, with compression / valves / internal spec info, and a flow test chart. So he knows exactly what works and what's a waste of time and labor. You change a shape in the intake port, you change the length of an individual throttle body runner, you change the fuel mapping at 3/4 throttle at 5000 rpm, and see what it does. So many variables. And then he posts them for everyone to learn from on the E30 forum (r3vlimited.com).

I learned the Phil Singher redblock engine recipes may be lost. Some portions of the fabrication / porting process - I don't know the details - have been lost due to those specialty shops no longer supplying that work. I would think a talented machinist could be taught those critical steps - unless A, there's no market for ancient B20 heads, or B, the info was intuitive knowledge in Phil's head (brain) and not written down / not drawn anywhere. That would be a shame.

With today's tools, I would think you could 3D scan the best examples of B20 head porting and combustion chambers, and store that info. Whether it could guide you while doing it by hand, with critical dimensions, or whether it could be a CNC kind of solution if you could calibrate exactly where you are on an old head.

One of the things I've been learning, is the E head has good flow and power - stock - but they're expensive and hard to find. An F head can be made to flow better (with some real work). One of the old threads I read talked about building up / adding material to the floors of the exhaust ports, which are too large and create slow turbulence instead of good flow. You decrease the port with the right shape and increase the exhaust velocity and scavenging. I think they were using some kind of high heat epoxy. Pretty cool stuff.

[volvolugnut]

There are CMM (Coordinate Measurement Machines) that can convert shapes to Computer files (or check complex shapes for accuracy to the design). These can be simple as FARO arm (Google it) or room size machines.
Sometimes people refuse to train anyone else because 1. they do not want to share their private knowledge or 2. they think no one else could every do what they can do.
Other times people just do not take time and effort to document the process.
volvolugnut

[BlackBart]

Fascinating stuff. I've seen photos of the tiny dot probes working, mostly in CNC machining settings. The laser measuring seems like the way to get a negative / hollow 3D shape mapped. The measuring head would have to be quite small to maneuver inside the port.