1979 SC Chewed a Valve - Total Rebuild

[OsoMoore]

Originally Posted by PeteKz

Last time I had the CIS off my engine, I oriented the hose clamps on the manifold/airbox seals so that I could reach them with a long screwdriver with the CIS on the engine and the engine in the car to make it easier for my future me.

That was my goal too!
But the right-side buttom ones I couldn't find an angle that allowed that. Those ones I couldn't even line up for access with the engine out - I tightened them down before lowering the CIS onto the engine.

The top and front ones weren't an issue at all. The left-side bottom I aligned to access from the back, conceivably you could get to them although not really see when in the car.

But I'm not surprised you found an angle. Just hoping I won't have to have this out again for a while. I'm supposed to torque the head studs again later as part of the break-in (per the book), hopefully I can do that without an engine drop.

[PeteKz]

I don't remember whether I was able to get all of them oriented to be easy to reach. I do know that I made an effort to do so. I'll have to go look at my engine and see if I get the ones on the right side that way.

[ammonman]

Originally Posted by Flat6pac

911 110 394 02 Is the product for sealing the airflow sensor to the air box.
Bruce

When attaching the airflow meter to the airflow housing be sure to run the screws down until the compression springs are fully compressed, then back the screws off 1-2 turns. This is the factory "pop-off" valve that is intended to mitigate damage from backfire instead of the aftermarket "toilet seat" that usually becomes an air leak.

[Henry Schmidt]

Originally Posted by ammonman

When attaching the airflow meter to the airflow housing be sure to run the screws down until the compression springs are fully compressed, then back the screws off 1-2 turns. This is the factory "pop-off" valve that is intended to mitigate damage from backfire instead of the aftermarket "toilet seat" that usually becomes an air leak.

Sorry but that's just silly. The air box explosion is created when cold start fuel puddles in the distribution chamber beneath the throttle valve, There is no way for pressure to be created beyond the air flow meter into the air filter housing.
What happens is that cold start raw gas is sprayed into the distribution chamber, it puddles and as the cold engine cranks, it runs lean and back fires. If the throttle valve is closed when the back fire hits the standing fuel the pressure is created below the throttle valve and that pressure breaks the air box. The springs holding the air flow meter in place will never see an appreciable amount of pressure.
The flapper valve vents that distribution chamber into the air filter housing to prevent explosive damage.

[OsoMoore]

Originally Posted by PeteKz

I don't remember whether I was able to get all of them oriented to be easy to reach. I do know that I made an effort to do so. I'll have to go look at my engine and see if I get the ones on the right side that way.

Somehow I thought this was a good idea. Just not enough clearance to get a screw driver down and engaged. I eventually gave up, pulled off that header, flipped the clamps, and did it from the back instead.




Also regarding the airbox - I've definitely heard the pop-off slapping back on a few occasions, and have a friend who's un-pop-offed box blew and left him in a real pickle.

Yay for pop-off valves!

[OsoMoore]

I am still looking at this plugged-off hole on the left side of the left chain cover. It has the big hex-headed plug.
My original configuration had a sensor installed there. Although the wire to it kept failing and hadn't been repaired the most recent time.

Should I attempt to remove the plug and put the sensor back in? Maybe I can worry about it later?

[rwest]

Originally Posted by OsoMoore

I am still looking at this plugged-off hole on the left side of the left chain cover. It has the big hex-headed plug.
My original configuration had a sensor installed there. Although the wire to it kept failing and hadn't been repaired the most recent time.

Should I attempt to remove the plug and put the sensor back in? Maybe I can worry about it later?

My memory might be foggy, but I seem to remember that sensor being the thermo time valve that does something for the CIS?

[Flat6pac]

That’s a temperature probe that activates the cold start injector.
Bruce

[OsoMoore]

Originally Posted by Flat6pac

That’s a temperature probe that activates the cold start injector.
Bruce

Ok, might be good to get that hooked up before these new starts in 40 degree weather.
Hopefully the plug screws out easy.

[Henry Schmidt]

Not that it makes a difference on your build, I never understood why that cover continued to be cast with the air pump boss, so we just machine it off. We also like using an Allen plug on the sensor hole.
Serves no purpose what so ever, except aesthetics. Fun stuff.

[PeteKz]

That hole is where the thermo-time switch goes. It controls the cold start injector. Unless you want hard cold starting, reinstall and hook it back up. Although I simplified my CIS by removing the AAR, AAV, deceleration valve, and related plumbing, I left the TTS and thermo valve (under the left #3 intake runner) connected for ease of cold starting.

[OsoMoore]

Sounds good. I put it in this morning, although I'm going to need to splice the wire going to it. Fortunately its tiny wire-hookup screws aren't missing.

Getting quite close here!

[Henry Schmidt]

Originally Posted by OsoMoore

Somehow I thought this was a good idea. Just not enough clearance to get a screw driver down and engaged. I eventually gave up, pulled off that header, flipped the clamps, and did it from the back instead.




Also regarding the airbox - I've definitely heard the pop-off slapping back on a few occasions, and have a friend who's un-pop-offed box blew and left him in a real pickle.

Yay for pop-off valves!

As you are learning, replacing the rubber intake sleeves is impossible (without removing the entire intake) if you find the need. That alone should dictate the rationale behind replacing those sleeves when you have the intake off. Rubber deteriorates with heat and time. Doubt what I'm saying? Every tyre comes with a production date....why? Rubber dies with time and heat.

The only issues I've seen with the pop valve are installation failures. Poor quality epoxy or the valve installed facing the wrong way. The hinge should be on the outer edge so when the valve opens the leading edge of the lid doesn't hit the air filter.

[OsoMoore]

I'm also looking at a new wiring harness. Does it ever stop costing more? I feel like my last 13 years have been blissfully cheap.

[OsoMoore]

Looks like there are two possible part numbers for the harness:
91161201603 - Made for externally regulated alternators
91161201604 - Made for internally (alternator-mounted) systems

My car is a 79 but has the newer in-the-alternator regulator. So I'm pretty sure I need the 91161201604 version. Does that sound right?

[mikedsilva]

Originally Posted by Henry Schmidt

As you are learning, replacing the rubber intake sleeves is impossible (without removing the entire intake) if you find the need. That alone should dictate the rationale behind replacing those sleeves when you have the intake off. Rubber deteriorates with heat and time. Doubt what I'm saying? Every tyre comes with a production date....why? Rubber dies with time and heat.

The only issues I've seen with the pop valve are installation failures. Poor quality epoxy or the valve installed facing the wrong way. The hinge should be on the outer edge so when the valve opens the leading edge of the lid doesn't hit the air filter.

Henry is right.

My opinion... if you are considering spending bazillions on a new engine harness, then "treat yourself" to new intake boots, gaskets, injector sleeve, o-rings etc..

[Henry Schmidt]

Originally Posted by OsoMoore

Looks like there are two possible part numbers for the harness:
91161201603 - Made for externally regulated alternators
91161201604 - Made for internally (alternator-mounted) systems

My car is a 79 but has the newer in-the-alternator regulator. So I'm pretty sure I need the 91161201604 version. Does that sound right?

Here is an American made product that is top shelf and avoids import tariffs.
I've used the product and it is stellar. We make our own harnesses for our custom engines but for stock replacement you won't be disappointment.

DP Engine Harness
Dennis Powell
Ph. 360-878-6276
powellgillam@hotmail.com
https://powell3080.wixsite.com/911-harnesses/original-style-harnesses

[OsoMoore]

Originally Posted by Henry Schmidt

Here is an American made product that is top shelf and avoids import tariffs.
I've used the product and it is stellar. We make our own harnesses for our custom engines but for stock replacement you won't be disappointment.

DP Engine Harness
Dennis Powell
Ph. 360-878-6276
powellgillam@hotmail.com
https://powell3080.wixsite.com/911-harnesses/original-style-harnesses

Thanks for the link, I'm also checking with another Pelican who makes harnesses.

[911 Rod]

Why a new wiring harness? You can do a lot with adhesive shrink tubing.

[OsoMoore]

Originally Posted by 911 Rod

Why a new wiring harness? You can do a lot with adhesive shrink tubing.

Good question. Four related factors building towards a conclusion.

1) When hooking up the fan/alternator, the insulation on the ground wire snapped when I had to bend it to fit. It is a ground, so it touching things isn't technically an issue. I was hoping to cover it for now with heat-shrink, but other parts wanted to crumble too. Its also a major current path, so a reliable conductor is important.

2) When adjusting the through-the-shroud bundle, the covering on the bundle was brittle and cracked. It stayed on, but wasn't properly protecting the bundle from abrasion. I was going to wrap it with electrical tape to extend its life.

3) The wire up the back to the air metering switch was worn through, possible pinched on something. Exposed copper. Still seemed to have solid wire underneath and no short, so I was going to wrap it up as-is and address later.

4) The wire down to the thermotime switch had broken off its spade connector and the wire was too short. I was going to splice a longer wire and repair it. But then the second wire also cracked and was crumbling where it comes out of its sleeve further up. I was going to need to split the sleeve a bit to get solid wire. But the sleeve was cracking when I tried to flex it.

It became apparent that the harness was falling apart at many points that I could see, and thus likely at additional points that I cannot see. I could spend money to rebuild parts on my own, or I could break down and replace the whole thing.

Shorts or breaks in the harness can lead to gremlins and misbehavior at best, and a fire at worst. Right now the engine is out, and the CIS is easily accessed. As much as I hate to spend another bunch of cash, I think this needs to happen now.

And as Henry strongly suggested, I'm getting new intake sleeves while I wait. Those, at least, are cheap. Better to do it correct right now, than to spend time and money on a short-term half-fix.