Short Stroke 2.8

[PFM]

Henry,

Care to share the proper adjustment? I am leaning this way after much thought, it is just simple. I tend to like simple, the motor is for a 914 so not a simple adjustment but not impossible either.

Thanks for the input.

PFM

[Walt Fricke]

Henry

What chain do you recommend? When I have purchased them from standard sources, they have all been one brand.

Walt

[Mr Beau]

Using solid tensioners is like driving a car with a solid suspension (as in no springs/shocks). Because a solid tensioner doesn't 'give', the chain experiences very high forces causing it to wear out much quicker.

A chain gets long because of the wear between the pins and the holes in the links--there is no 'stretching' going on. The reason why chains appear slack on engines with solid tensioners is due to the high wear that has taken place.

Now a solid tensioner may be a better solution than one that fails, but you should be aware of the extra wear the chain is experiencing.

Happy racing!

[Henry Schmidt]

Originally Posted by Mr Beau

Using solid tensioners is like driving a car with a solid suspension (as in no springs/shocks). Because a solid tensioner doesn't 'give', the chain experiences very high forces causing it to wear out much quicker.

A chain gets long because of the wear between the pins and the holes in the links--there is no 'stretching' going on. The reason why chains appear slack on engines with solid tensioners is due to the high wear that has taken place.

Now a solid tensioner may be a better solution than one that fails, but you should be aware of the extra wear the chain is experiencing.

Happy racing!

Although in theory there may be more wear but in application I have never noticed excess wear in properly adjusted chains with solid tensioners. I have however noticed major intermediate bearing wear in mag case engine using late style Carrera tensioners.
I have always noticed excess wear in all parts associated with racing stresses but never chain wear causing failure.
I have noticed over and over again race weekends ruined by collapsed tensioners and even catastrophic failure leading to a season ending explosion.

As for type: Iwis Racing is the brand we use.

As for adjusting, it is a judgment call because different engine cases and cylinders expand differently.
As a general rule, the chain should lift off the outer chain rail (closest to the cam) about a 1/2 an inch when lifted with a thumb nail. Mag cases with Nikasil cylinders set slightly looser.
Looser is better than tighter.
A loose chain may rattle slightly when cold but that rattle is of no consequence.

[Porscheman912]

Wow, this has covered many years, and is a great thread, so after a year of being dormant, I am posting now. Ok, one, Henry, how did those cranks come out, and what is the cost? I have a 3.0 liter that I want to put into my 69 912, which has steel flares from an 87 930S and still have not grafted in the front ones. I would like to built a fun revving street engine, and the 2.8SS sounds great. I drive my cars like I stoled them, and this car will be no different. Since I have the 3.0 SC case, it would be nice to use it, because I am not racing the car, just beating on it. Ok, two, who makes a MFI setup, or is it better to just try a find a used one and have it modified, or would carbs be the way to go?

[Henry Schmidt]

Originally Posted by Porscheman912

Wow, this has covered many years, and is a great thread, so after a year of being dormant, I am posting now. Ok, one, Henry, how did those cranks come out, and what is the cost? I have a 3.0 liter that I want to put into my 69 912, which has steel flares from an 87 930S and still have not grafted in the front ones. I would like to built a fun revving street engine, and the 2.8SS sounds great. I drive my cars like I stoled them, and this car will be no different. Since I have the 3.0 SC case, it would be nice to use it, because I am not racing the car, just beating on it. Ok, two, who makes a MFI setup, or is it better to just try a find a used one and have it modified, or would carbs be the way to go?

Cranks are a work of art. They were designed to use the Pankl GT3 titanium rod but with the new (stupid) price a few people have ordered RR rods fron Charles @ LN.






As for MFI: PMO now makes an MFI manifold set up if you don't want to modify the stock Bosch set up.

PMO


Modified Bosch

[Porscheman912]

Wow, those are nice cranks. I have wanted to do a turbo for this car, but a fun NA engine would be fine for now. The car has been sitting in my shop for a few years, and I need to get moving on it, so it is out of my shop, due to my business. Thanks fo the info.

[Tspringer]

What exactly do these cranks do for you? You mentioned before the possibility of going 66 x 102 for a 3.24L.... I assume this could be done with MFI and the twin plug setup? What case would be required, does the new crank allow use of a more available case than the 3.0 carrera/turbo?

Assuming one has no core parts at all... what kind of ballpark would I be looking at for one of these bad boys?


Terry

[svandamme]

the new cranks allow you to short stroke on a late case (SC, 3.2, ..)

The "old" 66 mm cranks only worked with the old cases , (2.0, 2.2, 2.4 , 2.7, 76-77 3.0 Turbo or Carrera.

i think somewhere in this thread there were prices mentioned for just those new cranks, 4 or 6 K, can't remember which.

[Porscheman912]

Here's a silly question. Would it be cheaper to have a newer case welded up, and line bored, or have a crank welded ground, and rehardend? Just had to ask.

[svandamme]

i think neither are scenario's that are typically done on 911's..

Why welding/machine case when you can just buy a turbo or 3.0 carrera case that already has the right specs?

[Porscheman912]

Like I said, silly question, but I thought I would ask. Those cases are not so easy to find. I would love to build one of these, but since I have an 81 case, or complete engine, I am just going to leave it that way, but wow, this 2.8SS would be a blast.

[svandamme]

They can be found, might take a while, but they are out there.
Got one right here, though it has minor external damage. (missing a strenghtening rib and an eye for a case bolt, must have hit a rock or something in a previous life, but still perfectly usable).

[Porscheman912]

I was just asking the question about welding the case or crank. After seeing the cost of the new cranks for the large journal cases. The smaller journals would be the way to go, for the simple fact of the crank being lighter, plus a smaller friction surfaces lets the crank spin up faster.
I would really love to build one of these, but it has to wait until my CNC starts making some money after dumping all of it into it.

[Walt Fricke]

Henry's cranks aren't cheap - as if any race parts are!

But stock 66mm cranks are all over 30 years old. Some may be newer replacements, but hard to tell. Think about a crank which is older than some of you are.

And Henry has put in all the bells and whistles: crossdrilled and grooved (that's really groovy, because you don't have to have bearings grooved). And it is lightened. And the 9 bolt flywheel attachment seems not to have the issues that the 6 bolters had at 8,000 rpm and above.

Where would things pencil out if you added the cost of all these modifications to an aged stock crank, and offset the lower cost of the much much more common (and thus less expensive) 9 bolt 3.0/3.2 case?

I already had the special case and older crank when I embarked on the SS2.8 adventure, so I've not done that math.

As to 912 guy's question, I suspect he will find that adding the cost of welding and machining, even if that doesn't have other issues (messing with the heat treat of the case, or part of it, and not just a small bead of weld either) means making the #1 journal of a regular 930 case smaller isn't cost effective. Now if you can do the welding and machining yourself and don't allocate a cost to that, your figures will be skewed.

Walt

[Kemo]

i just re-read this whole thread. What a wealth of information. thank you Henry, and others, for sharing this kinda info.

[Henry Schmidt]

Originally Posted by Tspringer

What exactly do these cranks do for you? You mentioned before the possibility of going 66 x 102 for a 3.24L.... I assume this could be done with MFI and the twin plug setup? What case would be required, does the new crank allow use of a more available case than the 3.0 carrera/turbo?

Assuming one has no core parts at all... what kind of ballpark would I be looking at for one of these bad boys?


Terry

The crank can be fitted into any case from 78 to 97.
The cranks use a more modern oiling design and are considerably lighter than conventional Porsche cranks. To build a 66x102 you need a 964 or 993 case unless LN makes a Nickie that is a 102 with a 105 spigot.
What you get from one of these cranks is a rod length to stroke ratio that allows for very high RPM. With the titanium rods and the big valve capability of the 964/993 heads you get the ability to turn RPM numbers close to 9000. This is practical unheard of with the two valve 911 engine.

Cost? Depending on the intake/ fuel management system, exhaust and core chosen you could build one of these for a little as $30K or as much as $50K+.

[GrantG]

It was a little difficult to tell from the photos, but have you made provisions to squirt fuel into the base of the Mag stacks (like the Plastic Stacks have) for cold start, in addition to the manual enrichment (that replaces the original thermal stack)?

Thanks!

[Henry Schmidt]

There are no provisions for cold start injection. Squirting raw, unmetered fuel into an engine is in most cases just a bad idea.
In deference to spraying raw fuel into the engine we have developed a starting procedure that works pretty well.

[GrantG]

Originally Posted by Henry Schmidt

There are no provisions for cold start injection. Squirting raw, unmetered fuel into an engine is in most cases just a bad idea.
In deference to spraying raw fuel into the engine we have developed a starting procedure that works pretty well.

Thanks, Henry!