Plenum pull scope creep

[evl_twn]

I've got a 94 with just over 40k miles on it, had a no start happen for the first time last week so I ordered a new (I'm guessing reman) AC Delco starter. It showed up today, waiting on Jerry to get back to the shop before ordering the plenum gaskets.


Here's the question/dilemma: I haven't had the plenum off this engine since I bought the car back in 2006, and that was mostly just to tidy up a few things and remove the "power plates". Not sure if those really add any performance or not, but they were installed with no gaskets so off they came and gaskets went back in place. I still have them but I doubt I'll put them back on.



What else would be prudent to take care of while the plenum is off? I've been scouring the forum and I think it's time for new plugs/wires anyway, probably get the IT20TT plugs and a new set of wires as well since they're now over 28 years old. Looks like AC Delco wires are still available, but I've also seen a set from NGK that look decent. Blue in color, but that's not a big turnoff for me (car is yellow so it's not like the plug wires match anything anyway :) ) Should I plan on replacing the coils as well? I'll probably keep the original wires since they still work and still have the Corvette/LT-5 markings.



I've seen a lot of posts recommending injector replacement but that's mostly for the early years? The car seems to run fine.



I found Roadster's thread that started with throttle body removal and expanded from there, saw his post about the 90 degree 1/4" rubber fittings so I'll get a set of those before the plenum pull too "just in case". Would it be a good idea to replace the throttle body and air horn gaskets, or just leave them alone? Roadster's thread has me convinced to NOT clean the throttle body and risk issues with the DAG.


Planning on replacing coolant anyway, so that's one more job to do at the same time. Would you recommend the throttle body bypass line from Marc? I already have the metal hoops from Marc for the intake boot.



Thanks for any advice, I'm still in planning stage now so there's a bit of time if I need to get other parts coming. Anything else I'm missing?


Thanks!

[XfireZ51]

Welcome to Wonderland Alice. Get ready to jump down the rabbit hole. :cheers::cheers:

[Paul Workman]

I've done 'bout everything 'cept port the TB and sleeve the cylinders and camming to my 5.7L LT5 including removing the secondaries, but have never heard of anything referred to as "power plates". What is/are they?

Bypassing the TB coolant path is a legit trick: Coolant by-pass does reduce intake heat a teeny bit. As Dom said, welcome to the "rabbit hole" of the quest for eking out performance tricks. (I plugged my TB coolant (as well) over a decade ago and never had a moment's regret - tho I can't point to an isolated 'before n after' result to justify it specifically. But, combined with a number of tricks (porting by far having the most significant effect), they all add up! :thumbsup:

[evl_twn]

From what I remember, the Power Plates were made by AO Engineering. I might still have the original instructions somewhere with all the paperwork I got with the car when I bought it. These were installed some time between 1995 and 1998.



I'm attaching a couple of pics, but they look like some sort of phenolic resin type insulator that was intended to mitigate the heat soak into the plenum. I read a long time ago some people had hood clearance issues with these and I do see some marks on the underside of my hood from the ribs of the intake boot. It doesn't look like there were any other clearance problems.They're just under 5mm thick.

[evl_twn]

If the Power Plates actually make a difference and aren't just snake oil, I might be tempted to put them back on (but probably WITH gaskets this time :) ) but since I already have some scuffs on the hood I wonder if the silicone intake boot Jerry's sells would clear better than the stock one?

[tokuzumi]

Probably just need to have the injectors cleaned and flow tested. If they are good to go, put the existing ones back in.

[JG95ZR1]

Go with the AC delco wires, I bough a set of the NGK for the color but the top of the boot has clear silicone on them and they look home made. Check the pcv tubes and make sure your getting a tight fit at all the rubber fittings. I really like the replacement silicone pcv tubes for our cars.


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[tokuzumi]

Go with the AC delco wires, I bough a set of the NGK for the color but the top of the boot has clear silicone on them and they look home made. Check the pcv tubes and make sure your getting a tight fit at all the rubber fittings. I really like the replacement silicone pcv tubes for our cars.


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)Maybe your NGK wires were a return?

[JG95ZR1]

Nope I bought two sets, both the same. They worked fine I used one set so far.18190


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[evl_twn]

Sorry for the lack of updates, but I ended up with no issues during the plenum pull. There was a lot of cleanup under the plenum that was necessary. Cleaned up all of the coils, put the new starter, plugs and wires on then started checking all of the vacuum lines for leaks/deterioration. The only issue I saw was a split in the line that goes from the rear of the plenum to the MAP sensor, replaced it.

[evl_twn]

I tested all of the individual lines and fittings with a hand pump brake bleeder with vacuum gauge. Everything under the plenum checked out, so I buttoned up the plenum and put the power plates back in with gaskets above and below. Turns out I didn't need the TB coolant bypass line, the power plates aren't drilled for the coolant passage so it completely eliminates coolant from the plenum and throttle body.

I wanted to check the vacuum pump operation before putting the coolant back in "just in case" :) . It occurred to me I've never heard the thing run since I've owned the car. I checked voltage at the plug, no issues there. Pulled the pump and found it was locked up. I bought the car from family in FL, it had sat for years in an unconditioned garage so I'm guessing the humidity and lack of use is what did it in. Got a replacement and checked the time between pump runs and it's now holding for 40 seconds between pump cycles.

[evl_twn]

I figured replacing the coolant was going to be a pain without the air bleed path through the plenum/TB. I read Marc's article about lifting up the passenger side of the car, and the revision using air to pressurize the system. Then I saw a few posts and watched a few videos on using a vacuum test/fill kit and bought one. Seems like the best option to me, works exactly like drawing down an AC system before adding refrigerant. Leak checks work the same way.

I purged the system and let it sit for a while, held a solid 25" of hg the whole time. The hoses even collapsed a bit. It was so much easier to add coolant back to the engine, it has a fill line that draws it in using the vacuum created. I think I actually added more coolant than what I drained so it might have been low to begin with, and that's with the lines through the TB still connected so the capacity might be a bit less now.

I was worried a bit about air pockets and bleeding the system but apparently this completely eliminates that issue. When the vacuum came back to "0" and it stopped drawing coolant I removed the tool and found the level was just below the cap. I added maybe half a cup of coolant to bring it up to the top, hooked up the expansion tank line and started it up. Temps seemed perfectly normal, both coolant pipes from the right and left injector housings were equal in temp.

I just got back from the first drive after buttoning everything up and all temps seemed normal. I'll double check the level after everything cools back down and also make sure it draws coolant back up from the expansion tank.

[ZR-1nce removed]

If the Power Plates actually make a difference and aren't just snake oil, I might be tempted to put them back on (but probably WITH gaskets this time :) ) but since I already have some scuffs on the hood I wonder if the silicone intake boot Jerry's sells would clear better than the stock one?







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