I don't read much about the 198 on this site. Does anyone know the potential for the 198 for quench chambers? Maybe in the Three Bears scenario the 198 might work out best, as quench in the zero deck 170 can make for 13:1 CR, unless dished pistons are used, and quench is probably not practical for a 225. I have not seen a 198 in years.

It's going to be difficult to have any truly defined quench with a completely open chamber like the Slant has unless you do this....

Here's a chamber sample i'm working on for the new cast Slant head.


Here's the machined left and right prototype of the same 3D model above:

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There's no such thing as too much cam....only not enough engine!

That is interesting design for the head.

With only the bottom of the chamber on a 170 welded and ground flat, the compression ratio might be high enough to merit a dished piston. I believe the zero deck 170 with a welded head can make some quench, but the compression might be too great for pump gas. I was wondering about the 198, I suppose it is similar to the 225 in this regard.

The heart-shaped combustion chamber design has been the industry standard for quite a while in performance cylinder heads. Since your talking about filling in the chamber to create a quench area, then yes, it will be helpful. What is your target chamber size?

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There's no such thing as too much cam....only not enough engine!

The compression can be too high with a classic heart shaped closed chambers, designers attempt to get as much of the advantage of quench, although the pent roof four valve designs are more common now. The old flathead motors can have quite a bit of quench as the head is literally flat, rather half of the chamber is flat. Some Nissan L series use a closed chamber "peanut" head, with about 9.5 CR. As per two valve chambers the GM '96 Chevy Vortec is a good modern design to emulate, the LS style better yet as there is more tumble that promotes swirl. My query is whether the 198 is a zero deck design.

A 198 has .060 to .070+ negative deck, less... but much like a 225.
(piston is way down in the cylinder and no 2 engines seem to measure the same)
DD

Thanks Doug for the info on the 198. For the effort involved quench probably isn't worth the cost. I would like about 9.8 static CR. I have a set of 198 rods. I think a dished piston would be needed with the 198 rods, maybe a little more than 10:1 would work okay with pump gas. My daily driver that gets 48 MPG in town has a small 4 cylinder and 9.8 CR. Other than TBI its simple 2-valve wedge chamber combustion technology is about as sophisticated as a slant six. I think near 30 MPG is a practical goal for a slant six '64 Valiant, which relatively speaking is probably better than the 48 MPG that my little car gets.

Since the slant never has had a quench chamber, its hard to understand what you've been missing by not having it. In other engines that do have one, it makes a huge difference when its taken away. So it's always a good idea to try and achieve it. In this case, it's a little work, but you'll be glad you did.

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There's no such thing as too much cam....only not enough engine!

If you build a quench head, I might copy your work. I think the best 225 quench chamber might need a dished (reverse dome) piston that resembles diesel pistons - but not so deep a dish as those, but with the recession toward the center of the piston. The custom piston means $$$$. Otherwise the flat of the piston won't face the flat of the quench surface of the chamber. I admire the experimenters and respect the theory but I'd like to get it right the first time.

Some Datsun L-series had a closed chamber "peanut" wedge chamber head, but most of those were sold in Japan - supposed to make better torque on pump gas. The L-series are a good case study as Nissan evaluated several design theories, although examples of some heads are limited to photos. The big valve/big port motors could make power, but had poor street drivability. Nissan eventually focused its performance L-series on turbos, which is probably where the slant six needs to go.

My emphasis is on economy via torque, if there is a horsepower increase that's a bonus.

Harry Ricardo's work impressed Walter Chrysler and his lead engineers. Ricardo's ideas on quench and combustion engineering won him the title of Sir. Fuel quality wasn't consistent so as to push the edge back then, but his conceptual work is still practical. The compression ratio on OEM motors without sophisticated engine management was kept low to export the engines without so much regard for fuel quality in other countries. His thinking was on track, but needed a few decades for technology to catch up.

http://en.wikipedia.org/wiki/Harry_Ricardo

Wouldn't it be useful also to look at the combustions chambers used in the 2.2L 4 cylinder Chrysler engines. I think the pre '86 Bathtub design and '86 swirl design could both benefit the slant.

'86 swirl design
Swirl (induced by intake port design and bowl entry) would be my favourite method of stirring to avoid detonation. (Jaquar were among the first to seriously explore this method in their old dual cam sixes)
I have always had reservations about extreme mechanical quench as experiments in engine ( 67 440 heads vrs 906 or 452 open chamber heads or BB chevy closed and open chamber heads) where one could try large quench and almost no quench did not produce any improvement from running the quench heads given the same compression ratio. That said I know it is for some the sacred cow and I would never discourage experiment.
don

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8 cylinders are for folks who cant make HP

I have done a few quench head Slants over the years and agree that there was little to no power difference, at the same compression ratio.

But... the quench engines seem a little more detonation tolerant so you could use lower grade fuels, increase ignition advance and / or increase DCR for a bit more power.

As already noted... a lot of work for small gains.

Another note: A closed chamber head with a dead flat quench area is the way to do it. Trying to stick the piston up into an open chamber head is a lot more work and the poor piston & rings take a lot more heat... and a hot piston top promotes detonation.
Just my 2 cents...
DD

What quench clearance did you have with this setup?

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There's no such thing as too much cam....only not enough engine!

In the .035 to .040 range.
DD

From what I understand, the biggest benefits of a good quench design combustion chamber are cleaner emissions,detonation tolerance, perhaps a slight improvement in fuel economy. If you can get a real fast burn speed then you don't need as much ignition advance to achieve the same power output = more efficiency. The idea is to get a nice homogenous air/fuel mix so "no HC's are left behind" . I'd imagine to get maximium benefit you'd work the design on a flow bench in tandem with your intake port shape.

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63 Valiant Wagon
225 - 4 bbl