70 LT1 plugs pics .How the hell did it run!

[Dennis D.]

New 45's came today. Spend half the day changing the lefts and 10 minutes changing the rights. It was a battle but I won. I think....
20190626_154217.jpg
20190626_154234.jpg

Here's the plugs that were in there
20190626_121136.jpg #7
20190626_125448.jpg #5
20190626_134436.jpg #3
20190626_135534.jpg #1
20190626_141203.jpg #8
20190626_141231.jpg #6
20190626_141759.jpg #4
20190626_142226.jpg #2
Opinions?


Lastly... the b28 vacuum can came today. How much dissassembly is needed to swap it out?

[Joe L.]

Re: 70 LT1 plugs pics .How the hell did it run!

New 45's came today. Spend half the day changing the lefts and 10 minutes changing the rights. It was a battle but I won. I think....



Here's the plugs that were in there
#7
#5
#3
#1
#8
#6
#4
#2
Opinions?


Lastly... the b28 vacuum can came today. How much dissassembly is needed to swap it out?

Dennis------


The badly oil-fouled plugs probably indicate a condition that's not going to be solved by simple plug replacement. More than likely, you're going to need valve seal replacement and, possibly, valve guide replacement. Even the plugs that are not oil-fouled show a lot of build-up that's rooted in oil getting into the combustion chambers. If only valve seal replacement is necessary, you can do that with the heads still on the engine. If valve guides are worn, you'll need to remove the heads for machine shop work.

[Dennis D.]

Re: 70 LT1 plugs pics .How the hell did it run!

Thanks for the resize Joe, and analysis. Plugs look really old to me. Engine was supposedly rebuit not long ago. Had the oil fouling issue with my L46, not to this extent, a set of umbrella type seals did the trick. I had bronze guides done when I had the 186 heads rebuilt years ago. Lt1 has the same heads. Hope its the seals.

[James G.]

Re: 70 LT1 plugs pics .How the hell did it run!

You can replace the vacuum can with the distributor in the car...
IT is Easiest if you have a screwdriver that locks the flathead screws into itself for reinsertion.

As Joe stated unless the oil flow in the combustion chamber is halted there is going to be nothing to stop the same situation from occurring again.
Umbrella seals are easy enough to replace. IT's minimal in cost and may as well be done now with the plugs removed.
If you pull the heads you may as well have bronze guides and teflon seals installed

[Dennis D.]

Re: 70 LT1 plugs pics .How the hell did it run!

Thanks James. The outboard screw in visable. I can barely see the inner screw. How do I go about exposing it?

[Leif A.]

Re: 70 LT1 plugs pics .How the hell did it run!

Thanks James. The outboard screw in visable. I can barely see the inner screw. How do I go about exposing it?

Pump up the vacuum canister with a MityVac, that will allow you to access the rear screw.

[Dennis D.]

Re: 70 LT1 plugs pics .How the hell did it run!

Perfect. Thanks

[Gene M.]

Re: 70 LT1 plugs pics .How the hell did it run!

Oil in the cylinder that bad...... guides are shot. Better off with iron guides as original.

[Duke W.]

Re: 70 LT1 plugs pics .How the hell did it run!

Pump down the installed VAC to the limit of pin travel. Then remove the screws and carefully wiggle the pin out of the breaker plate/stationary pole piece. Pump down the new VAC and install in the reverse procedure.Those plugs have either been in there forever or you have a significant oil consumption problem or the engine never had much load. Install the hotter plugs and check them after 500-1000 miles of driving. Watch for blue smoke and check the oil level frequently to determine the rate of oil consumption.Duke

[Dennis D.]

Re: 70 LT1 plugs pics .How the hell did it run!

The plugs look old to me. Previous owner didnt drive it much. Going to find out if he ever changed the plugs. The left bank in a real bear to get out around the AIR tubes. Particularly 5 and 7. Car doesnt smoke.

I'll put the vac can in later. Thanks

[Dennis D.]

Re: 70 LT1 plugs pics .How the hell did it run!

Pump down the installed VAC to the limit of pin travel. Then remove the screws and carefully wiggle the pin out of the breaker plate/stationary pole piece. Pump down the new VAC and install in the reverse procedure.Those plugs have either been in there forever or you have a significant oil consumption problem or the engine never had much load. Install the hotter plugs and check them after 500-1000 miles of driving. Watch for blue smoke and check the oil level frequently to determine the rate of oil consumption.Duke

Got the new advance in. Checked it first, seemed to start at 5" and max around 8".
new plugs installed. went for a short ride and pulled #2 when I got back. Thoughts?

Also checked my manifold vacuum. Between 8" and 10". set 12* initial, hooked up vacuum. Dial back TL said 28* at 900 idle.
Noticed some slight smoke out the back and fuel odor. Ran well, stumble was gone it seemed. Idled like crap.

[Duke W.]

Re: 70 LT1 plugs pics .How the hell did it run!

Typical LT-1 idle behavior is 900 @ 12". You say you measured between 8 and 10 inches? That's low and there should not be that much variation... could be a vacuum leak or a leaky valve if your data is correct.

It's time to do a compression/leakdown test.

Duke

[James G.]

Re: 70 LT1 plugs pics .How the hell did it run!

Idled like crap... just a thought here...
if you are at 8-10" at idle you may be dithering in and out on the Power Valve (probably 8.5's in it) which would explain your rich idle.
Has the engine been rebuilt/cam changed causing less vacuum due to more overlap or more lift...

[Dennis D.]

Re: 70 LT1 plugs pics .How the hell did it run!

Idled like crap... just a thought here...
if you are at 8-10" at idle you may be dithering in and out on the Power Valve (probably 8.5's in it) which would explain your rich idle.
Has the engine been rebuilt/cam changed causing less vacuum due to more overlap or more lift...

Great point James. Rebuilt to stock I'm told. Going to check with another vacuum gauge. Also will check for vacuum leak. Then leakdown. Previous owner adjusted the valves as per Dukes method. Judging from what else I'm finding, that may be questionable too.