LT1 Opti drive seal

**JD1964** · 09-19-2021

I’ve been messing a lot of stuff up lately and I don’t want to mess this up. The OPTi Driveshaft is what’s in the picture. I can just pull this out right? Then replace the seal, then I put the OPTi Driveshaft back in before reinstalling the OPTi is this correct?

**NomakeWan** · 09-19-2021

Yep, that's correct. Just make sure you install all those seals correctly (the one on the water pump is especially critical to get correct and there are plenty of ways to do it wrong), and that when you reinsert the opti drive, it seats in properly with no resistance. You should not have to force anything into place. If you do, it's because the shaft is not correctly lined up. Take it back out and try again. Same when you go to put the opti itself back on.

Good luck.

**JD1964** · 09-19-2021

Great thanks. Yes I’m aware of the water pump drive seal inner lip and how it needs to remain facing inward during the install. I’ll probably try the 1/4” drive 1/2” socket method as an install guide tool. The Felpro TCS 45953 kit has 2 small orings as well. I see one goes on the water pump drive shaft. Where does the other one go?

Btw, the 94 Opti has already been converted to vented using a 96 cap and drilled one of the drain holes for a vacuum fitting and plugged the other two. I run the factory Opti vacuum hoses with check valves too and the line to the bellows. Bellows from a 94 fleetwood. Sealed the cap with RTV. It works great and I can feel the slight vacuum on the bellows end of the vacuum line when running. All else is good with the setup and running good. But when I saw oil gathering under the Opti and saturating the plug wire boots, I’m having none of that. That’s why it’s apart

**NomakeWan** · 09-19-2021

Ouch. Yep, that's why if the opti comes off, the seals get done. Doing one or the other just means doing it again.

As for the other o-ring, it could be a spare. I don't see any other spot it could go other than the water pump drive.

EDIT: Looks like there's two O-rings on the water pump shaft, so there ya go.

water_pump.jpg

**JD1964** · 09-20-2021

Seal install went well. Opti is on and all sensors are connected with bellows installed. Crank hub is on but not the balancer portion. Water pump is not on yet.

Test start and it fired right up and calmed down to the set idle in about 10 seconds. Shut it off. No leaks but that's only 10 seconds run time.

Question: How long can I safely run dry cylinder heads (no coolant) from an ambient temp startup? 30 seconds, 1 minute, any idea?

Thanks

**LeMarky Dissod** · 09-20-2021

Originally Posted by JD1964

Question: How long can I safely run dry cylinder heads (no coolant) from an ambient temp startup?
30 seconds? 1 minute? Any idea?

Depends on ambient temp?
Long ago, equipped with an Meziere HD H2Opump (>48GpM if you ask Meziere), parked atop a long steep hill, I tried something stupid on a 23°F / -5°C winter's day.

I started the wagon's LT1 with the electric H2Opump disconnected.
When the dash temp gauge needle hit 230°F / 110°C, I repowered the H2Opump and rolled downhill, both fans staying on til the H2Opump temp sensor was under 203°F / 95°C.

From 23°F / -5°C to 230°F / 110°C took a wee lil bit over 7min. (Despite the stupidity, engine lasted another 125K miles, 255K miles total.)
On a record hot desert day, I'd guess 3min or less?

Important note: I'd previously familiarized myself with the correlation between the H2Opump temp sensor & the dash temp gauge needle when the engine was equipped with an OE-type mech H2Opump, a 525RpM idle, and fans set to turn on @ 235.4°F / 113.00°C?
IMEO, if the dash temp gauge needle hits 'the red', it may already be too late. Get to know your dash temp gauge needle personally before trying this stuff.

**JD1964** · 09-20-2021

Originally Posted by LeMarky Dissod

Depends on ambient temp?
Long ago, equipped with an Meziere HD H2Opump (>48GpM if you ask Meziere), parked atop a long steep hill, I tried something stupid on a 23°F / -5°C winter's day.

I started the wagon's LT1 with the electric H2Opump disconnected.
When the dash temp gauge needle hit 230°F / 110°C, I repowered the H2Opump and rolled downhill, both fans staying on til the H2Opump temp sensor was under 203°F / 95°C.

From 23°F / -5°C to 230°F / 110°C took a wee lil bit over 7min. (Despite the stupidity, engine lasted another 125K miles, 255K miles total.)
On a record hot desert day, I'd guess 3min or less?

Important note: I'd previously familiarized myself with the correlation between the H2Opump temp sensor & the dash temp gauge needle when the engine was equipped with an OE-type mech H2Opump, a 525RpM idle, and fans set to turn on @ 235.4°F / 113.00°C?
IMEO, if the dash temp gauge needle hits 'the red', it may already be too late. Get to know your dash temp gauge needle personally before trying this stuff.

I don’t think I could compare your description here with my question because in your case the water (coolant) was present in the water jacket, even though you had no pump function. So even without a pump, the fluid in the head would absorb some heat. My question assumes there’s no water or coolant in the head.

It’s not a big deal really. I can put it back together without running it any longer than the 10 seconds I already did.

I was just wondering what a safe run time might be for an LT1 aluminum headed engine with “no coolant” might be.

**LeMarky Dissod** · 09-20-2021

Originally Posted by JD1964

I don’t think I could compare your description here with my question because in your case the water (coolant) was present in the water jacket, even though you had no pump function.
So even without a pump, the fluid in the head would absorb some heat. My question assumes there’s no water or coolant in the head.

I see your point - also, my heads were iron, not aluminum.

Originally Posted by JD1964

I was just wondering what a safe run time might be for an LT1 aluminum headed engine with “no coolant” might be.

Assuming the engine is truly cold, I'd not idle-run any engine with no coolant for longer than 120secs, regardless of block and / or head composition.

**JD1964** · 09-20-2021

10-4, I'll limit it to 60 seconds

**JD1964** · 09-22-2021

Only one of the water pump mounting holes in the block passes in to the water jacket. It's the lower one on the drivers side. I'm putting PTFE sealer on the bolt threads for that hole. The way I see it, the other bolt holes don't go into the water jacket so they don't need sealer. I'll use a skim coat of RTV on the flange gaskets.

Sound about right?

**NomakeWan** · 09-22-2021

Originally Posted by JD1964

Only one of the water pump mounting holes in the block passes in to the water jacket. It's the lower one on the drivers side. I'm putting PTFE sealer on the bolt threads for that hole. The way I see it, the other bolt holes don't go into the water jacket so they don't need sealer. I'll use a skim coat of RTV on the flange gaskets.

Sound about right?

Yeppers, sounds correct.