Duke

There's a lot of unfounded information about the 16v heads not being suitable for turbo. I'm reposting my last post from the "High Flow, Low Cost, 8V Cylinder Head Project" thread:
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There is absolutely nothing in factory development for a street car that is aimed at maximum power. Turbo was primarily added to engines to give more power without maximizing the rest of the engine.

This "16v head was not proven to be reliable for a turbo" is a bunch of BS and there is nothing that supports this. The same goes for the ceramic insert in the 951 exhaust ports that also have turned out to be done mostly for emissions to get the catalytic converter up to temp more quickly...

Comparing the heads the 16v IS indeed much better to use for more reasons than power as the 8v head has a steam pocket that can and will create issues on a high hp engine. The 16v head does not have this problem so yes, it is a better head to use. Sodium valves are nice but usually heavy. My new 16v head gets the Ferrea SuperAlloy exhaust valves which can be said to be an improved inconel valve and removes the need for sodium filled vales.

Besides the fact that the head flows much better and produces the same power at lower boost levels the pent roof design with location of spark plug is much more efficient. And you can run a little higher static compression. So if you're interested in the full aspect of things you will get out more power compared to an 8v for the same energy level you put in (fuel).

Trying to analyze what engine parts are the "best" to use by looking at different racing programs some 30 years ago is simply not the right thing to do. It doesn't say anything about anything. The same reason the 968 Turbo RS have a special 8v head with tiny ports (and only produces 305 hp). It doesn't say ANYTHING about what is best. It is always a combination of marketing aspects along with rules.

Voith

~20 built engines of which 90% failed in first 50.000km definitely proves all that.

Where are all those great 16Vs?

blade7

Over 30 years ago Ford UK saw a 16V twin cam head that Cosworth had developed to fit onto a 2.0 Pinto block. That head with a turbo fitted went on to dominate Touring car racing for several years. I had one of the original Sierra RS Cosworth road cars with a few modifications and I don't remember anything coming past me on the road in the 13 years I had it.

Dutch944

Seriously Voith? Are you just trying to be the best pessimist around here to not use 16V? How many 8V's have failed? when you compare the amount of 16v's to 8v's, there have been less failures on 16v's!

Voith

Im not trying to be pessimistic, just do not see a rational reasoning to swap to 16V if 8V can achieve same power albeit with more boost and has better low end response.

It is extremely obvious that 16V head is theoretically better in many ways, but there are also practical sides of this equation that are not discussed or when they are, there is a ton of hurt feelings.

Aprox at the same time, Ford UK also tried to develop F1 4 cylinder turbo engine and failed miserably at that. Although these F1 4 bangers worked they self destructed when put to a proper testing.

blade7

I looked for a 2.7 head for ages, I'd go straight to the S2 head instead now. Not because of the extra power potential just for the more efficient design.

thingo

I'm with Duke, the 16V is so much better, the 8v is a nice period piece, but the 16V is a proper modern head.

blade7

OK .

Duke

Seriously? This is your argument why a 16v head is not good for turbocharging?
This could be an interesting thread if we analyzed it from a technical point of view but ridiculous statements like that does not add anything of value.

First of all, I have been on RL for many years and I have never seen anything pointing to a higher failure rate with a 16v head so your will have to back up these radical claims with data.

Second of all, I don't want to be rude so please forgive me here, but it doesn't really seem you know what you are talking about. You made specific claims against the 16v head, and then you talk about failed engines.
So let's discuss the reasons for engine failure. Most of the failures (8v or 16v) on engine builds here are due to improver sleeves and/or piston combinations. Then we have rod bearings. And we have head gaskets. And the broken rods.
If you actually take the time to analyze things with an open mind you will quickly realize that none of these failures are due to the usage of 16v heads. In fact - the head gasket issues can in some occasions be traced to the steam pocket in the 8v head making the 16v head a better choice in this aspect. I haven't seen a single 16v turbo failure due to the head.

The 16v head is a massive improvement over the 8v head just as the 968 block is a massive improvement over the 2.5l blocks. Siamesed cylinders, raised floor, windage ports, larger waterpump, piston squirters that cool the pistons etc. It's an improved package all around. Regarding your earlier comment about knock threshold it is in fact higher on the 16v head so it is less prominent to knock.

A 8v turbo engine can be a great engine and I don't remember anysone saying that 16v is the ONLY way to do it. Both can be done and there are pros and cons with both types. A technical discussion can be interesting but it just seems you have something against the 16v head and doesn't back up your wild claims of 16v failures with any data.

refresh951

I hope Michael Mount weighs in here. I know he has built several 16V turbo motors. Duke's and JET951's success alone is enough for me. Both have proven to be reliable in race environments. In a race environment, clearly the 16V head is the better solution. That being said I think there have been some over statements about the 8V head to prove a point. In my view both have there place and it depends on the application.

Voith

I don't have anything against 16V head. However there is a hype surrounding 16V heads that I don't get.

Im all for tech discussion.

gruhsy

You didn't happen to buy the Cosworth from Polar Motors Ford did you?

Duke

I've written a lot of technical things. As you can see, from a technical point of view, there is nothing that supports that the 16v heads are not suitable.
But as I said earlier, I'm totally fine with not going the 16v route and there are several super impressive 8v engines out there. But don't go around spreading false things like 90% of all 16v turbo builds fail!

Voith

Lets take you for instance. You are experienced engine builder I take, how many of your 16V engines failed and how did you came to conclusion exhaust valves need to be Ferrea, not stock?

Duke

I've had 2 16v turbo engines fail. First one overboosted to 1.7 bar and since it used factory 951 rods they instantly failed. The second one had a rod bearing failure during shake down in the race car before I got the dry sump kit in place. So nothing related to the 16v. In my 3rd (current) engine I'm still running the same old stock 968 head I bought from Markus in Estonia many years ago. He ran it on the strip, 1 mile etc with 1.4 bar of boost. I used the same head on the street/occasional track for 1-2 seasons with 514 rwhp and in my race car during 3 seasons with more power than that.
All that using stock valves. Never a failure and they still look great. Now I'm building another head with larger valves and naturally uses the best possible valves available today, just as I would choose another valve over the stock one on a 8v head. As you can see above the stock valves have held up perfectly fine and I would without hesitation use them on a street / track day car.

An important factor about my last engine is that I've used it for 2 seasons and winning races and taking track records without changing head gasket once. Not sure this would have been possible on a 8v head.