Rkreigh

here's the rub On a big displacement engine you need all the cyl head flow you can get and removing secondaries allows you to port more aggressively

on a smaller engine with a closer to stock secondary port size, I've heard they cost about 6 cfm from the blade in the airstream

on my 390 LSV only picked up 6 ft lbs and I suspect that was from tuning. Ask Graham what he recommends, he's the man and won't steer you wrong

Now I've maxed out the port, we'll see how much it picks up. The secondary flapper are not much at all of a restriction if they open fully

RatRacer

Sounds about right, Ron. When I determined my horsepower goals, I felt like 630hp, 530rwhp, would be near the limit for drag radials on the street, and realistic with my current porting. Anything beyond that would be difficult to hook up and cost exponential $ for little return, so I've been trying to stay somewhat pragmatic about it. Time is also a consideration, and more porting delays the project.

HAWAIIZR-1

Mine still work on my 95. When I swap out the top end for ported this summer I’ll check everything and replace parts as needed. I know that little check valve has been leaking for years so I’ll finally get to it. No plans to delete.

RatRacer

I spoke to Graham and he recommends removing the secondaries on my build. A small performance gain, but will prevent problems down the road with air leaks, etc.

Iliad

My '92 still working strong.

1985 Corvette

Mine worked on the 1991, however the passenger side actuator gave up working. I was able to find a replacement thanks to Paul Workman. IF there was a reliable supply of actuators, I would’ve considered keeping them. However, when I removed my butterflies, the valves were CAKED with deposits. The primary valves were all nice and clean. I actually drive the car as intended and got into the secondaries opening for some 6 to 7K rpm runs at least once every drive. Even with that, the secondaries still cake up it seems.

I loved the dual mode aspect about the ZR-1 and always will, but after seeing the valves, I don’t miss it. It didn’t help that she already had the secondaries modified in the chip to always be on regardless of key position when I took ownership. Now if I had kept the entire vehicle all stock that would be a different matter. I chose to go after headers, 3.90 rear gear, top end porting and an aluminum flywheel.

One day I will have the engine rebuilt to a 368 and at that level, Marc or his son would probably recommend deleting the secondary throttles anyway. I think they’re great for a stock application. Once you start chasing performance, I don’t think one will miss them.

Paul Workman

Good point on the "coking" of the valves, etc. on the secondary valves. I've been running w/o the secondary valves/hardware for about 10 years now w/ no problems/no coking.

pushrod-v8

A little motivation for you. Not sure if you have read up on this build.

http://zr1.net/forum/showthread.php?t=32002

ZR-71

Mine are currently not working. Pretty sure it’s a vaccum leak as pump doesn’t turn on.

VikingTrad3r

mine would function if i had not wired them open. i left them like that in case of resell.

the racecar build, they be gone!

SAM/CH ZR-1

Mine are in and I love it.

RatRacer

Mine are gone now.

Tokuzumi

tl;dr - no secondaries for me

Just got my 94 a few weeks ago. I noticed this electrical connector not connected to anything. After reading some of the Haibeck literature, I see it's the vacuum pump for the secondaries. Plug in the connector, and the pump runs continuously. Since the car runs fine, this must mean the secondaries have been eliminated, and I have an aftermarket chip in my ECM.

Photoguy000

Mine are still in and working in my 90. #2530 32k miles.

HAWAIIZR-1

Works great on my 95 and worked great on my 90 and 91. Never had a problem with secondaries in 19 years except a broken pump when I first got my 90 in 2003.

Vette Daddy

I always have the deleted and programmed.

no more vac leaks

Vette Daddy

I always have the deleted and programmed.

no more vac leaks

Brandon's Z

Mine work as intended. I check them often!!!

blownrunner

I have a 91, the secondary's work and still installed, but I have mark's chip and safety wired them open. Even the vacuum pump still works/runs. Very easy to go back to stock.