Top speed in 1ST gear for stock Z?

[rush91]

I've seen where the top speed for stock Z should be around 58-60 MPH.....A few times this weekend I got in a few stoplight races. The highest I could get was around 50 MPH, and that was shifting at 7000 RPMS. I know I have a vacuum leak under the plenum, and I've also noticed the car missing or cutting out a tad, when getting on the throttle.... Being a novice mechanic, I'm thinking it maybe time to check the plugs and coils? Coils and wires are MSDs, plugs I have no idea about. Injectors have changed out, as well as new chip from Marc H.....Any ideas where to start?

[XfireZ51]

If u know u have a vacuum leak, that would be a good place to start.
Also, check for codes

[rush91]

I guess I have my 1st winter project....pulling the plenum for the first time. It just feels like she is sluggish, almost like it is down a cylinder at times. Is that possible?

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[Paul Workman]

PROVIDED...your tach calibration is accurate, this chart (c/o Marc Haibeck) will provide what your looking for, for a ZR-1 w/ stock wheels/tires.

Note: If your tach was at 7000 rpm and you were only doing 50, the tach may well have an error (typical of these cars as they get long in the tooth!)

.

[Roadster]

My Z is stock with the exception of Marc's chip, and I have seen 59mph out of first gear @7200rpm's

[rush91]

Thanks for the chart....that good stuff. Maybe I'm short shifting

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[Ronstar]

Originally Posted by rush91

I've seen where the top speed for stock Z should be around 58-60 MPH.....A few times this weekend I got in a few stoplight races. The highest I could get was around 50 MPH, and that was shifting at 7000 RPMS. I know I have a vacuum leak under the plenum, and I've also noticed the car missing or cutting out a tad, when getting on the throttle.... Being a novice mechanic, I'm thinking it maybe time to check the plugs and coils? Coils and wires are MSDs, plugs I have no idea about. Injectors have changed out, as well as new chip from Marc H.....Any ideas where to start?

Plugs,wires vacuum leak etc. will have no effect on your speed/rpm in any given gear. It make be slow getting there but it will not change the equation. Maybe a previous owner changed rear end?

[rush91]

As far as I know the gears are stock. It seems like as soon as I hit 5000 rpms in 1st, it's winding out and it's time to shift....


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[Paul Workman]

Originally Posted by rush91

As far as I know the gears are stock. It seems like as soon as I hit 5000 rpms in 1st, it's winding out and it's time to shift....


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Just a "SWAG", and I hate doing that as a rule, BUT those symptoms (runs out of steam at 5000 rpm) are classic "NO SECONDARIES" scenario, OR the accordion hose between the air filter box and the plenum is collapsing (which is what mine was doing when I had that exact problem).

Do you have the stock hose? If so, Marc can provide you with some hoops to insert in there to keep it from collapsing. Easy fix (if that is the issue).

And, if the hose isn't collapsing, then there's fuel pressure and Secondary Port Throttles (SPT) operation to verify.

You're in FBI country, so some of the best gurus of the ZR-1 are not far away! But, the "group" mainly resides in the Chicagoland area. But, IIRC, you're near Marion, IL, yes?

If so, and you want to drive up to Custer Park, I've got everything on hand to trouble shoot/assess the situation and either fix it or at least put you in the right direction.

PM me and we can hook up.

BTW, what year is your ZR-1?

Paul.

P.S:

If you can fashion a metal sleeve to fit inside that accordion hose, it might solve your problem and save you the trip... Just sayin.

[BigJohn]

Check fuel filter?