special tool

yes
yes
no

toddk911

Oh ok. I thought he was around 430+.

BC

The 16V heads have a ton of material and are very robust. Are you saying that the 16V head is weak?

special tool

No dude - they breathe toooooo well - this means that they will let EVEN MORE good air into the combustion chamber, thereby exacerbating the condition.

Also - common knowledge that the 2.5 liter 's' head is not up to the task of high boost. Those are weaker. Girdles have been made.
Please don't come back with a 928 that make 400 RWHP - because the combustion pressure per cylinder is a laughable joke compared to my engine's.

OZ951

Sorry to hear you didn't manage to achieve your goal on this occasion ST. But thanks for sharing the knowledge your discovering as you push the boundaries. As well as generally raising awareness of where the limitations are I figure this also makes opportunities for enterprising individuals or fabricators to come up with marketable solutions to the problems you have discovered.

BC

That’s good news - the combustion chamber for the 4V heads are perfect for boost. Very similar to the 959 heads. A Stock block except for a bit chewed out of the stock pistons is at about 650bhp in Wisconsin, and now that the fueling has been worked out for a few years, Tim has stopped pushing coolant. My Current engine build is a stock block through and through, but with MLS and some ARP studs. I will run that with some good boost. Limitation for Pre-S4 is still EFI. They are playing with Autronic. I don't know if that’s the best option. A 7.0L is almost done, but that will be run by a motec I think. I think that will see low boost for track work.

No- I understand that 400rwhp is nothing on a 5.0L V-8. People think it moves these cars really quickly, but they have no idea what a highly boosted 951 or any other highly boosted car feels like. The 951 does have a thicker cylinder wall then the 928 unfortunately (or fortunately), we do have to be a bit more careful. The fuel system is only good to about 500bhp, and there it is straining, and the issues that I mentioned above with fueling were more like the last injector on the batch fire was shooting a lean stream because it was at the end of the "pipe". Running fuel into the middle of each of the rails solved that.

The stock cylinders are not being used in the bigger HP engines though. The people in the Midwest doing this went straight to sleeves and custom pistons. Stock crank and rods though. Heads lightly massaged.

Bri Bro

Get the TIG welder out.

special tool

I will weld it on if I have to (seriously).
But I will exhaust all rational means first.

Porsche-O-Phile

Clamps? Bracing of some sort?

Just out of curiousity, are you doing anything to brace the tops of the cylinders from rocking or moving, "locking" them to the block such as was done on the 3.0L 968 blocks (where the cylinders are all connected)? If it's a trade secret or whatever you don't have to share, I'm just curious. Always wondered if there was a way to grout those voids solid and keep everything rigid, although you'd have to work out a cooling solution somehow too.

Porschefile

Sorry to hear ST. HMR larger diameter headstuds will help. Worst case, a welded in deck plate should cure the problem. I think I want to go that route myself as it seems like it would structurally reinforce the block by a significant amount. MLS headgaskets just don't put up with the slightest imperfections or uneven spots unfortunately, and in my experience they can be a pain with open block designs as they are typically more prone to flex. Were you using a widefire before on the last attempt?
How are the S heads not up to the task? Is it because of the internal structure around the valvetrain components?

porshhhh951

sorry to hear you couldn't reach you're goal.

goodluck in 07'. I'm sure you will get there soon.

and for gods sake get VIDEO!

TRP951

well you didnt get your goal this time but you do still have a couple of days in 06 left

special tool

Well - I have decided to try the ARP's after talking to their tech.
He was semi busting my stones about running (trying) 700 HP on Porch stretch armstrong studs.

I will change NOTHING else.
So some of you guys who really want to know if these are worth a damn, or just BS, stay tuned.
I will be posting facts (as usual) with regaurd to cylinder head clamping a high HP 951.

By the way, I am sure you all know that the head is off and 100% cleaned and checked already, right?

kasturbo

Not surprised at all! Good work Tool. So I take it the head is still true then? Are you going to take another stab at it this year?

xsboost90

you go BOYEEEEE!!!