Firewall Access Port

[Alan Lindquist]

Caution - some of you aren't going to like this.

After dropping the motor two times in a week to chase the holy trinity of oil leaks at the front of the motor (firewall side) and still experiencing leaks, it was decided to cut an access port in the firewall. I've attached photos below. At 18 inches by six inches, it allows access to the entire front of the motor as well as the vacuum manifold and the fuel distributor.

I realize that a partial drop or fuel system partial removal is the preferred method for people who don't want to drop the motor. I actually don't mind dropping the motor. but after replacing the thermostat gasket, air box gasket, oil pressure switch, and internal oil cooler gaskets. I was more interested in watching while the motor ran (after cleaning) to be sure where to apply the next fix.

The demon turned out to be the breather hose. I should have suspected it or at least read threads before dropping the motor the first time, but that's how this went down. The hose was hard as a rock and wouldn't seal with a tight clamp.

After replacing the hose with water hose (correct hose ordered) the leaking in that area stopped. It's now easy to lift the upholstery and get to the back of the motor and see what is going on.

We've welded a flange on 1/3 of the remnant plug. The other 2/3 is being worked up. We decided for a slip fit instead of one long piece for a tighter fit since we were dealing with an uneven surface.

We used an air saw. It took 25 minutes from start to finish to make the port. You have to be careful, as the main engine harness is right there. And you have to pull away the sound liner so you don't mess it up with the blade.

Thoughts?

[fanaudical]

Interesting solution.

Doesn't that firewall contribute significantly to the torsional rigidity of the back of the car? Have you noticed any difference in handling/roll or see any stress-cracking in those corners yet?

[Alan Lindquist]

I'll check periodically to see if it is stressing. I can always weld in a clean plug from a junkyard Porsche if it begins to show stress.

It's a street car. I won't be racing it so it doesn't see hard cornering, just spirited driving and I don't notice a difference so far.

[steely]

The purist in me isn't ready, but it sure looks practical, from a maintenance / accessibility point of view. I wonder if you could weld a rib or flange around the cutout to add strength if req'd?

I removed the intake to get to my triangle - this would've helped.

[DRACO A5OG]

Whoa, I sure like to know how it holds up. Would a bead of weld on the rim help or maybe a fabricated "X" cross member??? At a minimum a smuggler's box type hinged panel???

Hmmmmmmmmmmmmmmmm.

SUB'd

[wildcat077]

Interesting solution,although i had the same issue with the breather hose which was split at the clamp ... i ended up removing the air filter box and AFM to get access and after cutting 4 inches off the bottom of the hose all was well again !

Access holes sure would be convenient though !

Cheers !
Phil

[Josh D]

I think that is genius! An aftermarket solution that would include a hinged door, seal, and some Dzus fasteners would be very marketable I would think! Hmmmmm......

[steely]

Originally Posted by DRACO A5OG

Whoa, I sure like to know how it holds up. Would a bead of weld on the rim help or maybe a fabricated "X" cross member??? At a minimum a smuggler's box type hinged panel???

Hmmmmmmmmmmmmmmmm.

SUB'd

jebus we think alike - honest, the smugglers box squarish tubular edge was what I was thinking about. pretty stout.

[andyt11]

I don't think the car's handling will suffer for it to be honest.

I don't think I could take a saw to my car, but it sure would be handy sometimes to have access like that! I wouldn't be in too much of a rush to close that up. Might be good to fab a hinged access panel instead for now!

[NOLAsc]

Looks much like raymondporsche's option D for getting to that side of the engine:



Apparently the hole is straight, but the insulation is crooked. This was on a thread I started (but am only now getting close to making progress on or even finishing): SC oil breather leak -- drop engine or remove CIS

Alan, I'm glad to hear the hose fixed it. I need to replace mine. It's stiff. Do you have a part number for that piece? The exploded view diagrams don't really show what I expect to see. Is it 930 107 394 10?

[fred cook]

The Sunbeam Tiger from the mid 60s had a removable (rubber) port on the right (passenger) side to access the rear spark plug. If the V8 in the Sunbeam chassis worked ok, then the "port" in the Porsche rear firewall should be ok. I agree that a reinforcement around the edges would be a good idea! Maybe there is nothing new under the sun!

[McLovin]

Ferrari does that on a lot of their cars. Really helps, too.

I don't think the part you took out is structural.

If the CIS engine were the original engine first put in the car in '65, my guess is Porsche would have put in an opening like that.

But the early 911 engine compartments were so bare and open, a port like that wasn't necessary. All of the engine was easy to reach. Those earlier engineers would have never imagined all the "stuff" that would eventually be piled on top of the engine block.

[Alan Lindquist]

The partial covering on the left has a flange but we only machine screwed it in. We were going to do that for the rest of the panel and slip fit it. But based on your suggestions I think we'll try to fab weld some support (flat bar rim) around it and make a swinging door with a tight seal.

If I see stress issues or when I come up with a final solution I'll post again.

The guy that's helping me with this was an Airframe mechanic in the Air Force. ALL planes have access panels. It's not a question of whether or not it makes sense, it's a question of whether or not the area is engineered to withstand the missing metal. This is RIGHT behind the shock towers. So an X-Brace may be necessary. Racing really loads a chassis. I've seen firewall mods to accommodate full cages reaching through to brace the shock towers. I'm not racing this car.

The other concern is the purist. I WOULDN'T do this to a long nose. It just screams shadetree mechanic. I'm not denigrating the SC. I love it. But it's a long ways from a collector car when you can pick up a roller for $5,000.

[Porchcar guy]

My daily driver is a 2000 Camaro. Fuel pump went out. Chevy sez...$600 for the pump...$900 labor..Gotta drop most of the rear end to take the tank out for access to fuel pump on top of tank. From the rear hatch area, it has a hump between the axles for the tank. Cut a 7"x12" access panel ..!/2 hr max...Removed and installed new pump ($325)...1 hr.. 20gauge steel plate painted to match, seam sealed and pop rivets later ...stronger than ever but easily accessed if need be...I would cut this panel in my SC in a heartbeat if I thought it was needed..YMMV as I am not a purist , guess that's why my SC is a mongrel :=)

[Dr J]

Congratulations! I've thought about doing this many times. I would say the structural effect is minimal.

[Alan Lindquist]

Just a follow-up. I was chasing vacuum leaks this weekend and decided to pull the firewall access plate and work the firewall side of the motor with some soapy water (after running the shop-vac on "push" up the tailpipe). Fortunately, I didn't find any vacuum leaks on the firewall side of the motor, but it sure was satisfying to be able to spend some time back there with great vision and access to everything. I can see that my oil leaks (holy trinity) remain solved.

I spent some time looking for signs of stress on the firewall and found none. I didn't reinforce the area several years ago, but I did weld up a full cover plate that has an overlapping lip and is secured with 10 self-tapping screws. Then sealed with duct tape.

I'll keep an eye out for any signs of weakness or stress and post again if I ever notice anything.

[Alan Lindquist]

See post directly above for explanation. Here is a photo taken from yesterday, two years after the "mod." Cover plate off.