2.0 plenum issue, Can it be removed while in the car? Options

[robkammer]

Hello brain trust! The engine saga continues on our BB. What started in February as an engine reseal, head refresh, and engine compartment repair is still ongoing. The heads needed a full refresh, and close inspection found cracks, that the head expert 'fixed' with Timeserts. Lifter wear pointed to a cam lobe that was half gone. So off the short block went to a very well know Type I and IV engine builder. Wife and I went to Florida and wandered around for a month while this was all taking place. Back to Ohio in March and I started gathering the parts needed for the re-install.
The heads came back looking great, and the short block looked even better, now with fresh bearings, a stock cam and bearings, and a new oil pump.Oh, and we dicovered that I had a 2056, Cool, right?
Got the heads on, all of the tin, wiring and hoses. Put the beast in the car and started the break in process. First 30 miles, then oil change and valve adjust, then 100 more, rinse and repeat. Noticed a pretty significant oil leak coming from the front of the engine. it was the new oil pump, totally unacceptable. The builder came to my shop in hope that the oil cover gasket was the problem. Uh, no.
So out came the motor, back to the builder who is 100 miles away. At the 130 mile mark I also pulled the plugs to see how they were firing. All good, except that three of the Timeserts came out with the plugs, crap.
So while the engine was at the builder I ordered a new set of AMC heads, shipped directly to the builder. Why not, eh?
Get the engine back in with the new heads, start the process again. Got through about 65 miles and the engine is running like crap.
All of the FI bits are working as they should, and all with engine wires are Jeff b's harnesses. The only non functioning bit is the thermo sensor on the side of the plenum.
Plugs looked ok but maybe a bit on the lean side.

Time for a Smoke test! Cool tool for sure, brings back memories of my Lionel trains.

At first glance it looked like the throttle body shaft was leaking, although I had Rocky in Walla Walla rebuild it while the engine was out the second time. Nope, turns out that one of the two unused tubes through the plenum had somehow come loose and is allowing atmosphere into the plenum. I've attached a video.

So after that long intro about my sorrows, the question is: Can I remove the plenum while the engine is in the car? I struggled getting the intake runners onto the plenum the second time while the engine was on the cart, I used the 100 mile old rubber tubes and they may have shrunk. I'll buy new rubbers again, and of course the intake gaskets. But am I delusional that I may be able to get the plenum off in order to repair or replace it without dropping the engine, Again!!??

Any helpful advice will truly be appreciated.

Robbo
 smokin.MOV ( 3.06mb ) Number of downloads: 51

[robkammer]

Hi Fellas: I do not have a CHT gauge, nor an AFR gauge. Or a fuel pressure gauge either.
This engine has been a 2056 since way before I bought it in 21. Ran fine, not lean for the thousands of miles I've driven it. At full temp yesterday it settled into a nice idle once I adjusted the idle screw on the TB. I want to check the timing again just to be sure,
Does the CHT control anything other than the AAR? And what would an AFR tell me?

[emerygt350]

Hi Fellas: I do not have a CHT gauge, nor an AFR gauge. Or a fuel pressure gauge either.
This engine has been a 2056 since way before I bought it in 21. Ran fine, not lean for the thousands of miles I've driven it. At full temp yesterday it settled into a nice idle once I adjusted the idle screw on the TB. I want to check the timing again just to be sure,
Does the CHT control anything other than the AAR? And what would an AFR tell me?

The factory CHT in the car for the fuel injection is of course controlling the 'extra richness' needed for cool engine temps. The AAR is entirely its own thing and is just a 'idle up' adjustment that should close very rapidly. It is literally equivalent to the step idle on an old choke system on a regular car. Does nothing but open the throttle (without actually opening the butterfly, instead it is a vacuum leak elsewhere).

The CHT and gauge that we are asking about is normally a ring placed under the #3 cylinder spark plug and run to the cabin for a gauge like a Dakota Digital CHT. This tells you how hot the heads are getting by monitoring the hottest cylinder (3 is hot due to the cooling design on the passenger side bank).

The afr gauge tells you how lean the car is running. You want it lean at cruise and rich at WOT. The values people tend to shoot for is 12 - 12.5 at WOT and 16 or so at cruise (some people like being richer at cruise, some don't). All of this affects performance and more importantly heat.

Prolonged head temps above 400 can result in dropped valve seats, burnt valves, and pinging from lean mixtures destroy your engine.

Without the CHT you don't know how hot the heads are getting (the oil does not respond very quickly to increased head temps so your heads can be over 420F in a minute or two and your oil can still be 140F).

Built motors with higher compression (even a 2056) can result in excessive head temps pretty quickly.

Some people prefer the stress free no gauge approach. I like to get in front of things before they go south.
This is right after start up so the AFR in the lower right is still waiting for a signal it likes from the O2 sensor.