911 aircooled developments

[Lukesportsman]

Always a good read, Neil.

[stephen1070]

Good afternoon Neil - do you have any updates or experiences to tell on the various initiatives discussed in this thread. Thank you!

Regards,
Steve

[Neil Harvey]

We have been extremely busy with the air cooled developments and now back on the later water engines.

We have the last of the 997 GT3 engine (our R version) apart and will show some photos of those parts this week if I get time. Heavily into the new 991 Gen2 GT3 engine development. New crank, Rods, Pistons etc all been developed. New cranks arrive this week so I will show those too.

The air cooled parts are still getting rubbed on too. New valve train for the 4.1L engines, cranks are done, the lightweight steel rods have been shown here, have the finished articles now so I'll show those as well. Pistons and cylinders are all done and in house. New Titanium through bolts and hardware are in production along with some of the other fasteners. Trying to lower the engine weight as much as possible.

We have pretty much redone all of our cam designs covering most air cooled engines from 2.7 up to 4.1L. All are new A symmetrical designs , trying to modernize the old staples. I think our smallest cam design would work well on the smaller engines as well. Jeff in Australia has given some good feed back on the cam design we did for him.

Along with the builds we have in progress, the machine work we do for some, the new design work keeps us busy. I know these parts and our services are not for all. Cost often disqualifies us, but in some cases the customer is not requiring our level of work and parts. We offer our services and parts for those that want something other than an off the shelf part and work that is not typically offered. Having spoken to many, they all have been surprised that this level is available.

[stephen1070]

Thank you Neil - looking forward to reading about these new component parts and fitting them into a rebuild.

Regards,
Steve

[Neil Harvey]

I said I would post some photos of the new cranks we have just had made. 2 Gen 2 991.2, 2 997 Gt3 and the others are modified stock cranks for various builds we are doing. More are in production both for water and the air engines.

The two cranks on their own are the new 991 Gen2 GT3. This is a huge project that is taken a lot of my time at present. Lots of re engineering required on that block to keep it from cracking. Trying to keep on top of all of the air cooled parts, too. I'll take some better photos of the new air cooled parts as soon as I can. Unfortunately, it is taking a lot longer to get parts now but we have to deal with it like everyone else does.

[Pesch]

As always, thank you Neil for sharing to the hobbyists of this forum your approach on Porsche engine building.
This is very helpul to put in perspective what to expect from a build pointing out so many often overlooked aspects.
I particularly enjoy reading about springs, ramps and harmonics, an area that to me seem to have been untouched for years in the aircooled Porsche world.

[Neil Harvey]

Originally Posted by Pesch

As always, thank you Neil for sharing to the hobbyists of this forum your approach on Porsche engine building.
This is very helpul to put in perspective what to expect from a build pointing out so many often overlooked aspects.
I particularly enjoy reading about springs, ramps and harmonics, an area that to me seem to have been untouched for years in the aircooled Porsche world.

Yes, for years the air cooled engines have been left behind in development. I guess its easier to buy "off the shelf" than to develop something.

I think the difference between production repair shops and the shops that take a professional approach is the actual work done. And why.

My opinion of production shops is, get it in and get it out as quickly as possible. Quality is not #1. Quantity is. If your business model is this and its known, there is nothing wrong with this business model. If this level of quality and workmanship is all you need, then you are shopping in the right place. But, in many cases, its believed by the customer that this model gives the best work. Its not.

For example, when we get cylinder heads to repair, its very common in the disassembly to find 5 shims under the Exhaust springs and 3 under the Intakes. Also, some heads that we see that have an after market spring fitted show seat pressures far too high for the application. Poorly designed cam profiles and in many cases very poor copies of good designs require heavy pressures to be use. Harmonics are present in these low RPM engines, much can attributed to the valve train.

I read how the cam timing is difficult to set, or where should the valve timing be, only to know that once the engine is run the timing all goes out the window. The only saving grace for the valve train components from breaking is the heavy nature of the parts and the low valve train RPM.

My love for these older more simple engines has given me a new desire to develop parts. I hope others will follow and more choices become available.

I know for the DIY owner cost is very important. Much of our stuff would disqualify us due to its cost. That's ok too. But knowing what you are getting for your money is as important. Knowing the differences and having a choice makes decision making and the end result far better for all.

[Neil Harvey]

With many magnesium cases needing main housing bore repairs and some of the higher powered aluminum cases needing attention as well, we are producing a new case through bolt that incorporates a dowel section at the case split line.

I know these cases are often dowelled with a solid dowel but I am not a fan of that application and the way its done. It makes disassembly hard and I think I'm right in thinking that a line bore is required after fitting the solid dowels. Every time we did this it did require the housing to be cut.

This way the housing bore does not require any attention. There is some case machining required to fit the bolts mostly on one side. These are been made from Titanium with Titanium stepped washers and 12pt nuts.

As the power in these engines increases more attention is required in the basic parts always taken from granted.

This may not be for many as it does require all new bolts, a higher investment, but these follow along in the same vain as our other parts developed for the air-cooled engines. The first ones in production are for the later air-cooled and water-cooled cases as we have orders for these engines. The earlier cases that have a slightly shorter bolt are next.

[cgarr]

What problem do these eliminate? How much surface contact at the case halves where I see a relief for the oil passage?

[faapgar]

The RSR engines had this design and helped to keep the line bore true.I looked at having some made in the mid 80,s but could not justify the cost at that time.I bought a few sets from Frau Behr at Porsche but do not remember the cost.I bought titanium rod bolts for 2.4-2.7 engines as they were the same as 917.Also titanium head bolts that had a fiberglass around them to protect them from being scratched.Fred

[cgarr]

So they must be a press fit to eliminate any fretting?

[gled49]

935 thru bolts, I still use today. 11mm so case hole ends need to be enlarged. Bolt center at parting line does not fit tight in bolt bore.

[Walt Fricke]

Interesting that the 935 part isn't tight at the parting line, which suggests it doesn't serve the function of bushing the parting line through holes or pinning.

I've admired those two piece aligning washers. I always thought they were used on both sides? But maybe one is enough? As I recall, they are used because the bolt holes on each side are not exactly directly across from each other, and these washers allow the bolts to tighten square, with no bending moment? If this is so, does making the wider center section of the bolt problematic with regard to alignment? Or does my memory of what I have only read skip a beat or two here? If the through bolt holes are the same distance apart, you'd think the opposite side holes would line up directly, so why the fancy washers?

[gled49]

The self aligning washers are on both sides. When I view the parting bolt holes in the case 1/2’s, they are rough. I would guess a machining process would be necessary to guarantee a snug fit with the bolt centers at the parting line. Of corse the bolt centers need flats cut for oil passage. Could the large center be there for a harmonic reason.

[reclino]

DIN 6319 metric spherical washers are available at McMaster-Carr

[Neil Harvey]

Unless we have just been unlucky, every engine, late or early has shown the case halves shift. The back side of the main shells and the case parting lines both show the results of the case shifting.

Holding down the clearances and controlling the oil film between the crank and the bearings is job #1. Inspection of the bearing faces always shows the inconsistent oil film across the length of the shell.

I think this is often overlooked or not taken seriously by many. The reason to remake the through bolts and to change their application over the old "935/962 race" way is to bring modern technology into an old issue that has never been solved.

As the strokes get bigger in these engines, the issue does get worse. If I was in the business of selling parts, I may take the attitude of, we'll just sell more new parts and let the problem stay and not spent the time and money fixing it. This seems to be the consistent theme of Porsche and many other OE's today.

But as an engine person my job is to see a problem and solve it.

I have a saying I tell people every day. "There are only two types of people in this business. Those that see it wrong and fix it or those that don't see it at all".

[lvporschepilot]

Those bolts are a great development Neil. Very glad someone is doing this. Eliminates the need to have the entire 7r case dowel pinned, which I have seen cases a huge amount of stress on 7r cases. Cracking after a while is not uncommon so I have been seeing some building opt to only dowel pin 3 of the main journal web areas (total of 6 pins) rather than all of them.

[gled49]

I’m just using old parts because that’s all there was. Will u have to bore the thru bolts holes to guarantee hole alignment at the parting line. Keep up the good work. G

[Neil Harvey]

More parts are in design or now in production. It's amazing just how long it takes to design a simple bolt and it's application. The air cooled development is parallel with the water cooled developments we are doing.

The air cooled is a lot more fun and easier as we are not really having to fix a broken engine. The current 991.2 GT3 engine has a serious block issue we are trying to understand and fix.

Steve Becker has joined Performance Developments and will focus on the air cooled machining and engine building. This will allow PD to offer more customer machining services along with more rebuilding services.

Steve's credentials in the Porsche engine world are hard to match. He spent 18+ years at Andial in the race engine shop as the lead engine builder. He built many race winning engines including Daytona, Le Mans, and even some Paris Dakar engines. Along with being an excellent engine builder, he is a well trained and accomplished automotive machinist with both manual and CNC skills.

We are looking forward to giving the air cooled community another choice in machining and rebuilding services. We will limit the work we take in so the turnaround is days and not months.

nh

[Dpmulvan]

I would like to figure out a viable build for a 3.0 where you can get 250hp To 275hp without spending 6 grand on cylinders.