JMO but there is no replacement for displacement, unless you go to some sor tof forced induction, and since we all love naturally aspirated'

4 liter, Motec, resonance intake, limit revs to ~8000, designed for street use in a pre 90 9111 chassis w/ a 5 speed trans, it's ok to design for a g50

Thanks Jim and Bill.
This is what I was hoping for, a conversation about what a cool build might look like.
It looks like two different camps.
Jim wants a short stroke, high revving buzz bomb. (66 x 100mm)
Bill seems to be talking about a tractor with ungodly pull. (81.5 x 102mm)

Great start, thanks again.

Now my fellers are hurt

Peanut chambered heads please Henry.

https://forums.pelicanparts.com/11786804-post19.html

I'm not sure what to make of this.....maybe try silk panties SmileWavy

I was thinking the same thing. That might be a longer project. I'll investigate the time-frame to make a set.
This would point the project towards a high RPM build. The peanut head has two main benefits. Reduce propensity to detonate allowing for higher compression on low octane fuel and lightweight pistons because of reduced dome material.

The peanut head. These heads were machined to create an even smaller chamber which brought about the need for a spacer between the head and cam tower. Of course this created a minor issue with rocker geometry.

http://forums.pelicanparts.com/uploa...1749825486.JPG
http://forums.pelicanparts.com/uploa...1749825486.JPG

Since you guys brought it up, and since a new casting or cnc program would be way faster for a production run than welding up then machining original heads to make the peanut ports, you might as well improve the chamber to bring it into the next millennia.

Here's what the Gen 3 Hemi chambers look like. Notice the spark plug boss is extended to help start the fire closer to the center of combustion chamber? Notice how the chamber looks very similar to Henry's peanut chamber? Chrysler didn't just arrive at those improvements by accident or pure dumb luck.

http://forums.pelicanparts.com/uploa...1749826465.jpg

And of course, lighter pistons are the result of obviating the need for large domes, which also hinder flame propagation.

If one were to take it one step further, pistons with a very slight dish (think of the inner skin of a beach ball, a "spherical cap") made the most power in the testing that we did (compression ratios equal). The combustion pressure tries to push down in the center of the piston, reducing friction from side loading.

With the reduced chamber volume the dished piston would compliment the peanut chamber.

dannobee,
So you were able to measure the change in friction as the result of the changed piston crown? Wow!

I didn't know 81.5mm stroke was a thing.. this popped up for sale here in Aus... http://forums.pelicanparts.com/uploa...1749888379.jpg


I don't know the seller, or the quality of the item, but looks like the place that made it doesn't exist anymore.

My vote is along the lines of TurboPros. Small sub-3L screamer- but… twin turbocharged. Do some cool EFI stacks with the appropriate ducting for the snails to stuff in the extra air. Have it rip to 8k with lightened internals. Two maps for straight gasoline and e85.
Nothing like the bristling look of twin turbos.

We built our first 4.0 911 engine in 2008 (17 years ago). 76.4 X 105 mm
A true tractor motor. GT3 crank, 993 case, GT3 titanium rods and an enhance version a 3,2 Carrera intake w/Motec engine management . It used Venti-port heads w/Del West titanium valves to improve low RPM port velocity. Max hp was generated at 6500 rpm.
It was installed in a sand rail with a Mindiola transmission which proved to be the weak link in the power train. The torque generated by the 4.0 maxed the limits of the incredibly stout transmission.

http://forums.pelicanparts.com/uploa...1749907766.JPG
http://forums.pelicanparts.com/uploa...1749907766.JPG
http://forums.pelicanparts.com/uploa...1749907766.JPG

Small bore, high RPM, twin turbo sounds like a cool project but isn't that what Porsche puts in their modern street car?
I would be happy to build that sweet little engine for a designated customer but as a spec engine for resale I'm thinking it would have very limited market.
Keep the ideas coming.

Small displacement highly efficient turbocharged multi-valve petrol engine / Electric hybrid ?

Humm, that seems reasonable. When I build this using a Mezger case base engine, who is going to pay the $200K bill?
The purpose of this thread was to do a little poll to check which way the wind was blowing in the early 911 community. I have a plethora of parts on the shelf and an empty engine stand (for now). My thinking is, what would you guys want to watch me build not how can I reinvent the wheel.
Please try to avoid new tricks for this old dog.

How about small 11k rpm engine with those 4 valve heads
Could be carb or fi for simple install into early chassis
Regards probably easy sale for you if it’s proven on the dyno

I believe the 4 valve heads floating around the community are relatively unproven.
There are some rare examples of these engines in limited numbers but no one has produced data on how well they cool. Head temps are critical in air cooled engines and getting oil to flow through a 4 valve head has to be a monumental challenge. I look forward to seeing just how they addressed that issue.

They've been doing this since way before I was alive. Now the measurements are far more accurate. One common way is to compare BMEP to IMEP. The leftover is friction.

Henry,

Not sure what 4V heads you may be referencing.

The ones we are involved with have shown no issues to date and those engines were pushed hard in testing.

I went to the UK to personally inspect them and discuss our projects. So far we are pleased with the results and have upcoming projects we will be including them in.

Our Project 24 has morphed into a second in house project, Project 27, using these heads and a 993 engine case.

Good luck with what you are about to start. There are many here who will benefit from what you are doing.

My concerns about head temperature on 4 valve heads is generic not specific. Porsche couldn't figure out how to air-cool 4 valve heads hence the hybrid (air/water) engines of the 80s.
I'm glad to hear you've done the testing. Perhaps you can share the head temp vs horse power numbers you've discovered in your testing.
Maybe you have those numbers from previous test done by the manufacturer.
Surely, testing during product development would have produced those fundamental and crucial numbers.