924Board.org

Rick MacLaren · Guest

John that tactic you employ, using an indirect empirical measure of the air/fuel mixture is what I intend to do to my car. I've got the digital gauge, but laziness and procrastination are gettting in the way. I've got the gauge, and I've been putting off installing it to the O2 sensor. But that's definitely a good way to get a start on the answer to the question "Can I run more boost?"

Dave951M · Guest

An air/fuel meter is on the agenda for both the 951 and the 931. I've looked at several ways of doing it, including a diy electronic one. With the meter and an in-cockpit adjustable fuel pressure regulator, higher boost should be entirely safe within the mechanical limits of the bottom end of the engine. I'm shooting for 15psi street, with occasional peaks to 18-20psi. Now for fun stuff- is there a widefire headgasket for this car or do I have to get crazy and o-ring?

Dave

Rick MacLaren · Guest

Mine is just an LCD meter with two green LED lights I'm hooking up to light it up at night. Just have to solder on a couple of resistors and it'll read the voltages I need.

I asked about widefire headgaskets around my local community and didn't turn up anything for the 931. After a while I wondered if I really needed one anyway.

What's the rationale behind 'O ringing' the block? Is it necessary with this kind of installation you're planning?

[ This Message was edited by: Rick MacLaren on 2002-07-05 23:27 ]

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

Rick, O-Ringing effectively makes your block and head one piece. You weld a ring of metal to the block around each cylinder and grind out a corresponding ring in the head.

Up-side - no more blown head gaskets.

Down-side - more blown engines.

Basically, as the head gasket can't act as an over-compression fuse that job gets passed on to the pistons or rods or crank.

Ya gotta ask yaself, what would you rather loose, a $20 head gasket or an entire motor.

924_fan · Guest

I believe that to o-ring an engine a groove is cut into the block around each cylinder bore. These grooves are then filled with a metal wire o-ring made of either stainless steel or copper.

Isky Racing sells a tool to cut the grooves on V8 engines.

_________________
Skip Denton
'79 924 Sebring

[ This Message was edited by: 924_fan on 2002-07-06 09:38 ]

Paul · Guest

Don't ring the engine, just install Raceware head studs, washers, and nuts . This setup provides alot more clamping force, plus I haven't re-torqued it since I rebuilt the engine 5 or 6 years ago.

_________________
1980 931 M471 my daily driver
1988 924S my son always has it...
2001 986 for weekend grins
ML-320 for snow and towing whatever's broke...

I'm not a professional mechanic anymore, but I've been playing one at home for 30 years.

[ This Message was edited by: Paul on 2002-07-06 11:26 ]

Dave951M · Guest

The reason I'm even contemplating the possible boost levels are-

1) the turbo will have to be rebuilt anyway
2) the bottom end is a truck motor
3) stock compression is 8:1

O ringing the head can help with sealing, a bit of insurance when working at 15+ psi levels. The size of the crank and rod journals is massive for an engine of this displacement, I see no reason it can't hold up to a steady diet of 15+psi. The problem as I see it is the fuel system, arguing for higher pressure initially, switching to a larger injector next. The A/C knob will be removed, along with all their related components and replaced by a manual boost controller and an air/fuel meter. I can also lay my hands on a 951 intercooler as well. My nose panel is toast and will have to be replaced anyway, why not with a large intercooler under it? Has anyone on this board tried the 951 intercooler, what were the results?

Dave

Joes924 · Guest

Dave do the msd youll get a boost alright..
I use a msd6 with a separate soft touch rev control I like the boost.

_________________
JoeD. 1979 924NA
MSD6 rev control/big bore TB/P&P.head
Bursche header/Schneider cam/dialcam

[ This Message was edited by: Joes924 on 2002-08-28 15:20 ]

Rick MacLaren · Guest

The 951 intercooler has been done with success by guys here...

larso · Guest

Rick MacLaren · Guest

Lars, I guess I'm one of them there assholes that doesn't realize the engine is loose.

What's 'loose'? Can that be simply defined?

Or are you using some kind of argot that only engine builders understand? If so, what's it mean?

Dave951M · Guest

Long winter Lars or just get hammered in the markets???

I sincerely hope that you meant that some 931 owners are a$$es in that they flog the car with no regard for proper maintenance. Flog anything without care and it WILL fall apart, I don't care if it speaks english, japanese or german. This is a very simple equation in any language-

NO Maint + Flogging + Stupid Owner = DEAD CAR

I drive my 951 hard often, but keep up with the maintenance. It's a great car, but it isn't a car for Joe Average, too much expensive upkeep if Joe Average doesn't know a combo from a box end wrench (spanner for some of you guys.) That said, I'll get back to my engine building planning for this winter. Had a turbo setback, but that is being handled. Car will be mounted on a frame next week and the suspension removed for cleaning, r&r, and upgrading. While I have the control arms off, I'll take them to work, box them, put on new ball joints, and set them up to recieve a bigger sway from probably a 951.

Cbass · Guest

I am likewise in the planning stages of a 931 build. I have a couple of questions too.

Digital ignition, what are the differences between North American and ROW? Also, is there any reason why a late digital system couldn't be put on a series 1 car?

Turbo upgrades, has anyone actually done this yet? From what I am told, the 931 K26 doesn't last very long, and is expensive to replace. I know lots of 951/930 people, and even rice burners have upgraded to Garrett turbos, for better reliability, and lower cost.

Also, thanks for all the info guys

Dave951M · Guest

By "loose" we used to mean that the engine tolerances were on the + side. By tight, we meant the opposite. This can be controlled by careful matching of bearing size to the grind on the crank journals. Same holds for the pistons, rings, and wrist pins. Not sure what Lars is referring to, if all 924/931 cars were that bad, Porsche would have gone out of business from the sheer volume of warranty and liability claims long ago. There may also have been a problem with the owners using the wrong grade of oil. I use strictly 20W50 Valvoline Racing in my 951 with no problems. There is a raging controversy about synthetic vs. dino. What is generally agreed to is that the synthetic will find and flow from every nook and cranny to leak from that dino wouldn't even show so much as a wet spot. Each has its supporters.

John H · Guest

[quote]
On 2002-07-24 11:09, Cbass wrote:
I am likewise in the planning stages of a 931 build. I have a couple of questions too.

Digital ignition, what are the differences between North American and ROW? Also, is there any reason why a late digital system couldn't be put on a series 1 car?
[/unquote]
You can retro fit the digital ignition but you need all the components, control box, flywheel, flywheel sensor, distributor, throttle sensor etc etc. probably easier to pick up a series II, or at least the engien complete with flywheel and bell housing (with mounting point for sensor)