962 Two Valve Chamber Volume

[Speedy Squirrel]

I am investigating a 95mm bore turbo motor with improved or-ignition characteristics. One option is the 962 combustion chamber. I mocked on up using the photo in Bruce Anderson’s book.



I measured the chamber volume to be 84.8. The normal chamber volume was 92.7.



With a flat top piston and a clearance volume of 3.2, that gives a 7:1 compression ratio. I was shooting for 8, so I will have to tinker some more.

[Daugaard]

It seems that you can insert material on both sides of the valves

Bathtube combustion chambers

Daugaard

[stownsen914]

I believe this was done for a very specific use case - improving combustion characteristics on a racing turbo motor that was at the time limited by the rules to single ignition. I'd think dual ignition would be a much better solution in most cases.

Scott

[Speedy Squirrel]

Interesting! Thanks for the link. I am going to tinker some more this week with it.

Going with a turbo motor compression ratio of around 8 makes this an achievable goal. If you add too much material it shrouds the valves and effects the port flow.

Originally Posted by Daugaard

It seems that you can insert material on both sides of the valves

Bathtube combustion chambers

Daugaard

[Speedy Squirrel]

Well, they had their reasons, and I have mine!

Seriously though, the corporate “we” looked at a lot of variations like this when designing the modern Hemi. In the end they wound up with both! They needed the dual plugs for a smooth idle and low emissions, and the squish area for knock resistance.

Originally Posted by stownsen914

I believe this was done for a very specific use case - improving combustion characteristics on a racing turbo motor that was at the time limited by the rules to single ignition. I'd think dual ignition would be a much better solution in most cases.

Scott

[stownsen914]

Interesting. Can you fit the shrouding and a second plug? Or somehow shroud both sides of the combustion chamber? Sounds like some interesting experimentation.

[Edit] Read the posts linked above, and see that it has been done before. I wonder what the performance advantages are. I'd think there are easier ways to raise compression with custom pistons, but the reduced combustion chamber might yield some power that high compression pistons cannot?

[MBruns]

I have a set of those single plug, single turbo heads from a 934, It was the engine that Wayne Baker won Sebring overall in the school bus car. we have most everything to put that engine back together.
Mike Bruns

[Speedy Squirrel]

I think I need those!

Originally Posted by MBruns

I have a set of those single plug, single turbo heads from a 934, It was the engine that Wayne Baker won Sebring overall in the school bus car. we have most everything to put that engine back together.
Mike Bruns

[Speedy Squirrel]

I have filled in some more on the spark plug side. This arrangement yields around 7.5 compression ratio.



Here is photo of the current Dodge Hellcat chamber for comparison.



Does anyone have a damaged head I could buy to practice the welding and heat treating procedure?

[Henry Schmidt]

We built/welded a set of "peanut" heads for a 2.5 engine that made 11:1 compression using 2.7 (8.5:1) RS pistons. Short stroke and all.
Bill at Extreme Cylinder Head flow tested the heads and felt "shrouding" was not an issue.
Our thought was to have him replicate this design in a billet head but never pulled the trigger.





I probably have a damaged head you can have.

[Speedy Squirrel]

Outstanding! That’s the way to do it, or even 10:1 with a flat top piston. I bet that thing had a nice torque curve.

Apparently, the effect on valve shrouding is overrated. The current Hemi Head (Apache) is pretty similar:



Thanks so much. I will take you up on your generous head offer. I will message you to work out the details.

Originally Posted by Henry Schmidt

We built/welded a set of "peanut" heads for a 2.5 engine that made 11:1 compression using 2.7 (8.5:1) RS pistons. Short stroke and all.
Bill at Extreme Cylinder Head flow tested the heads and felt "shrouding" was not an issue.
Our thought was to have him replicate this design in a billet head but never pulled the trigger.





I probably have a damaged head you can have.