It doesn't matter at all under boost, which is the only way I like my redblocks. But ya the worst part is directly under the valves.

Wrong. It matters boosted or not. Either way you are working toward optimizing gas flow.

Hi
well this is a easy argument to sort

in standard form
940 turbo 163 horse power

940 16 valve 153 horse power
so its a no brainier
if you use the penta head you get even more because of the comp ratio

so put the same amount of boost in to the 16 valve and you get 229 horse power
I run a 2.5 penta 16 valve on carbs and am very happy with it in my Amazon

Sure we know about the efficiency and total power possible. The op question is that the power you can make with a 8v would satisfy most people. At least that's what I thought he meant.

There is a level of mechanical complexity that you are adding and you can make fun power with a big valve 8v.

I like 16v too. Just happy with the power I've made with 8v for fun on the street. I have a 16v head stashed if I decide to make the leap. There was a really nice 245 with an n/a 16v at Carlisle last year that really caught my eye.

Wonder if that was the old Conner850 wagon..... he had a thread a few years back, but I believe he has vanished back into BMW land.....

Pictures are great, here's a relevant one: a cutaway of the 530 head's exhaust port.



https://i.imgur.com/cCcfFdEl.jpg

What are we looking at here?

.

My car was faster with a heavily ported head, as well as my brothers. I did them myself. I guess others results may differ.

You cut your LS in half and think it's better?

Ok & impressive feat, that...

Haha, I have more than 1 car, I would be more likely to attempt a W16 LS. And fail miserably

Yes. For 99% of tbers that want 300 horsepowers!!!1!0” an 8 valve head is plenty. Some bigger valves and an enem cam, which all bolts on using stock hardware, is more than enough.

whatchu need bigger valves for? 300 is easy on a stock head with an ipd cam. can't be a sissy with the mbc tho.

So on the average “tuned” set up someone can run lower boost to make their 300 safer.

I'm still working out the details for my feature on True Life: I spent $4,000 on an 8v head

what's considered lower boost? we're devolving into semantics, but I'd say 20-24psi isn't really "high" boost, but it's not necessarily "low" either.

Anything under a bar I’d consider “low”.

I think you'd struggle to hit that mark below a bar unless you had something special

There's no real use in gasket matching a 8v when you're using the stock intake manifold. If you do the math for port wall taper based on the valve size, the ~40mm intake port entrance is about right... the issue is the factory taper is very severe (over a short distance) and the rest of the intake port is undersized. Once you remove ~3-4mm from the middle of the intake port , you get into the correct approximate CSA and taper.

Enlarging the exhaust side too much will cause sever issues with reversion along the port floor as well. It is better to widen the exhaust port than to remove material from the roof and floor. This is what Erland suggests, and what I've seen from heads where I ported the exhaust too much. The port walls will be really clean, but have a pocket of carbon on the floor of the port.

Pocket porting and blending in the SSR is where these heads need the most amount of work.

It was a gray late model wagon. I think he said 91. M47 with a n/a 16v. Used a lot of Volvo plastic and made it look like a stock installation.

A stock b230 skinny rod NA aw70 is better than a 16valve head for 99% of tbricks.

Change my mind.

if it aint blown.... it sucks!

bigtime!

Gotta keep the kids safe somehow.

Back when we had gas that was all benzene based. The skinny rod B230 with M47 consistently delivered 30mpg or more on the highway. Then fuel changed and those numbers dropped a good bit.