zrc3john

My 91 has the following mods...OBX Headers, exhaust,ported plenum, air horn, injector housings, Haibeck chip....K&N filter,hurst shifter...

I hear and have read that if you relieve the secondaries you will feel " seat of the pants performance "..

Anybody have my set up than have relieved secondaries?

Does it need a retune if this is done ?

Scrrem

You look like you have all the basic LT5 performance modes that give you bang for the buck. I'm not sure you will get the WOW factor by just pulling the secondaries. Having ported heads and no secodaries, that's where you will see some bang. People pull the secondaries more for elimination of a problematic vacuum system. Now folks either pin their secondaries open or pull them out all together, but either way you will need a retune on your chip.
Rich

jaymitchell01

What Scrrem said. I eliminated my secondaries back in 2003 because I got sick and tired of chasing vacuum leaks. I recall the ZR1 Net Registry did an article on making brass hoses for the vacuum system. For someone who isn't going to do a chip tune, it would be a good idea to look into. For tuners, easier to eliminate them.

Paul Workman

One of the best mods I ever did on my LT5. Throttle response is instantaneous, the intake valves both stay clean, NO more secondary vacuum issues, NO downside. What's not to like?

I pulled the entire mechanism and Marc provided a chip modified for "secondaries deleted"; a canned tune that sufficed until I later ported the heads and Marc finished the project off with a dyno tuning. That was 5 seasons ago - no issues at all.

billy mild

Do you need to remove the secondaries from the heads at that point? Can you just ZIPTIE the solenoids open?

ZR1Bob

I also did what Paul did--had Marc remove the secondaries when he did his 510 HP package on my '95, and I am very glad I did the mod. No vacuum headaches anymore and fine performance. A note of caution, however. What Marc does is he sets the primary and secondary injectors to each operate at 50% flow when the secondaries would not otherwise be operating, as opposed to the stock set up with the primaries at 100% and the secondary injectors off. So together they provide 100% of the fuel needed for lower rpm operation. As a result, you should never run the car in "Normal" mode, only in "Full" mode, as you would be running too lean at lower rpms. I simply set my car in "Full" mode and removed the Power key. I also attached a key chain tag to the Power Key noting the car has modified injectors and should never be run in "Normal" mode. Hopefully the new owner will pay attention--Bob