hihok9

Those of you that have done it, what method did you use to plug the shaft holes? Can you PM me or post here if you used drill and tap size, anything to watch out for, etc. Thanks in advance.

Hiho

VetteMed

I just pulled the secondaries last week, there's a freeze plug size that fits the hole very nicely, after the shaft and bearing is removed. The part I used is Dorman 555-108.

hihok9

That sounds great! Where did you order those plugs from?

hihok9

Disregard my last.... Just found them at Summit.... $5.99 per bag of 10

tpepmeie

You'll be waiting a loooong time for these from Summit. They've been out of stock/backordered since Feb. I finally gave up and cancelled.

wdo-mkr

Guys,

Give your local napa auto parts store a try. I think its still under the dana part numbers. Dana 219-3052.

billybaloneey

O'Riley also carries them.

VetteMed

Got mine from RockAuto.

Paul Workman

Just to add...

I had trouble getting the 555-108s to fit because I was using a socket (to drive the plugs in) that just fit inside the edge of the plugs: wouldn't allow the plugs to swag. A 10mm socket worked fine tho.

You'll need to remove the air box, if you're doing it with the just the plenum pulled.

I got my (no secondaries) chip from Marc Haibeck. I'll never put the secondaries back in. The improvement in drivability and throttle response is astounding, IMO.

If you're like me, you're gonna like not having that headache under the plenum anymore!

P.

VetteMed

I've got a chip from Marc Haibeck on the way as well... still have a lot of work to do before the car is driveable again, but I can't wait to test it all out! With 188k miles on the car, I just didn't want to risk reliability issues with all of the ancient gadgetry under the plenum!

Mr. Gizmo

i had a 91 zr1. I bought this car in 1996 with 392 miles on it for 30k. That secondary set up with the 16 injectors, butterflies, actuators, vacuum motor up in the front by the antifreeze overflow tank was a very complicated set up prone to problems. I might even say A gimmicky set up with the key on the console to activate the secondary injectors and 2 fuel pumps. - a design as technically advanced as the electric fork

I was never sure it ever worked properly on my 91 zr1.

Back in the day there was huge discrepancy in the performace of the cars. some cars tested by the car mags would run 12's others would run high 13's within the same year .I think this was because of the secondary setup in some cars was functioning properly in others it was messed up on different cars as sent to the car mags for testing.

The information from back in the day per gordon kilebrew was that there was a woman on the engine intake assembly from time to time at mercury marine that installed the actuators backwards. I pulled the plennum on mine and on the drivers side bank of the secondary butterflies were bound shut because the actuator was on backwards. - factory f-up. I guess this LT5 was one of the unlucky ones that this woman worked on. Until i figured out the problem after calling gordon kilebrew's c4 action line and fixed it myself, The car would fall flat on its face at 5500 rpm.

That secondary set up is the one thing i do not miss about that car. - a very silly design. but i guess back in the day to get the low end torque along with high rpm velocity that was the way it had to be done.

Other then this, I did love that car. the stance, the clam shell hood and that LT5 engine was a beautiful looking masterpiece. - My Ls7 does not look any different then the 5.3 litre v8 in a chevy avalanche under its hood. - but my C6 z06 does go like all hell and rattles and creeks a little less then the old c4.

65ZR1

Head on over to the zr1 net. There is a lot more info over there on this subject.

FU

There is at least one person that is eliminating the secondaries right now over there.When done right the removal of the secondaries can prove to be a smart move.

Rkreigh

helps throttle response and eliminates a bunch of complexity

parts left out don't break

don't expect gobs of power though, even on a stroker ZR-1 unless you port the secondaries on the heads, it doesn't do a whole lot

sure eliminates alot of headaches if you have problems/vacuum leaks

I asked dave mc. why they used vacuum cans

it allowed the system to use familiar GM technology and it's cheap and it works. but I always thought since the ecm commands opening/closing anyway, why not do it with electric actuators

cost I guess. but the vacuum cans and plumbing can be a pain

Paul Workman

I'm w/ you on this one! It seemed to me too that instead of triggering a vacuum switch, the ECM could just as easily have triggered a solid state (relay) and electric solenoid type actuators. After all, the secondaries are either on or they're off. Throttle is still controlled by the TB, whether the secondaries are on or not. Gone the need for the vacuum pump, the reservoir, check valves, and all those tubes and rubber seals, etc, etc, etc...

Was the issue heat or something we're not considering? Or, just that some vacuum systems design engineer was assigned the secondary actuation as his part of the LT5 contribution. Maybe the vacuum contractor just needed work? (Stranger things have happened.)

Cost savings?? Well, the next generation LT5 prototype did away with the secondaries, and the dual runners and dual injectors. So, relative to our discussion, one has to wonder if others didn't see the secondary complexity as you and I do...just an "electric fork"! (I gotta remember that one!)

P.

Rkreigh

probably cost and gm familiarity with vacuum cans

the electric acutators could have used actuator cables so they weren't under the plenum

I fly RC planes and the "cable inside a tube" for the servo actuators to the control surfaces work great and would allow the acutuators to be mounted anywhere. wouldn't take much of a deal to convert it.

since the ecm commands the vacuum switch, you could rig up the actuators to pop the secondaries open and elminate all the "plumbing"

I took the ez way out and got rid of them. the secondaries do help with emissions though, and increase the port velocity for part throttle operation. I don't think there is all that much advantage to getting rid of them unless you drive like I do (going WOT in every gear all the time)

Paul Workman

Marc Haibeck might agree with you. He says there is no practical improvement in performance by removing them. However, I'm not sure if he was referring to an otherwise stock motor or to any LT5, regarless of other mod.

However, just not having the headache may be grounds enough to remove them. And, I would argue that throttle response is better. After all, all 16 injectors are already running above idle, and there is no delay for the secondaries to open, nor the situation where one side is not opening completely, for some reason. (I like the "electric fork" analogy...a lot! to much "stuff" for what it does.)

P.

Rkreigh

yes, I'm sure Mark would agree. when I did mine, car only gained a handful of HP, and he retouched the injector housing and obviously retuned the car to run without secondaries. he showed me that even though it would add a few CFM (3-6) that the secondaries on my 390 were not the bottle neck (heads are)

you only flow as much as the engine demands, and gains from head porting is more than the small improvement from eliminating the secondaries.

as far as complexity reduction, definitely worth it. and throttle response is RIGHT NOW!!!

but not worth it from a cost/performance benefit equation

the secondaries although they don't open all that fast, they snap open in time to get into the upper rpms where the flow is needed and honestly the ecm "commands" them open fast than most folks think!!

would I do it again, yes, but I did it for elimination of the headache, Marc "prepped me" by letting me know I wouldn't see much of a gain

maybe down the road when I can pull the heads and open up the ports a bit more

Paul Workman

The stock runners in the heads on my 90 were 32.5mm at the valve guide. Truly, un-ported, the secondary hardware would not be the choke point.

However, like draining the swamp, as the heads are ported, then I would not be surprised to find the secondary hardware suddenly looms up to be a "bit" more significant, far as impeding the improved flow goes.

Well, whatever...I wasn't looking for HP by removing the secondaries anyway. I was looking for removing what appeared to be a bit of over-engineering to a solution, and the problems they cause. Removing them does that.

But, in my case, I was also wanting Marc's solution to the fans, AND the idle issue, AND backfiring with headers, and optimizing the timing for 93 octane. Wow! It doesn't drive like the same car after installing Marc's chip. He's done a really nice job with that calibration.

Put the chip and the no secondaries together makes for a very happy combo, IMO.

P.

95ZR1#418

Oh, how I've thought about eliminating those secondaries, just to rid the perpetual vacume leak problems, my living nightmare.