1991 L98 top speed

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Jan 31, 2014 | 10:13 PM

Doulop

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Intermediate

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1991 L98 top speed

Hello everyone. I have a 1991 with a 6-speed L98 in it. Completely stock with a few bolt on items. I see a lot of people on here say they have seen around the 150 MPH mark. For some reason, mine only gets to 126 and won't go any faster.. Any one have any idea what could cause that? Thanks for any help you can give me

Jan 31, 2014 | 11:21 PM

FASTAZU

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From: Compound in the Grove, Ga.

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All I can add is top speed is in 5th gear.

Feb 1, 2014 | 08:22 AM

hcbph

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From: Minneapolis Mn

Top speed

I'm assuming this test was done on a closed course and not on the highways.

Feb 1, 2014 | 09:07 AM

C4in mesa

Drifting

Joined: Dec 2011

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From: mesa az

Quote:

Originally Posted by Doulop

Be for warned you are going to get all sorts of negative feed back from members who never drive their Corvette over either 65mph or 70mph or 75mph. I bought my Corvette because it goes fast not because it looks great and certainly not because it is comfortable to get in and out of it. Then all the members who are officers of the law are gonna warn you about killing someone or someone else. This I admit is a valid reason not to speed. HOWEVER where I live I can go out in the desert and as advised from cops at Golds Gym where I train have told me, take a couple friends out with you in a few cars and set up the stretch of road you want to max it out. Have them give the green light and put the pedal to the floor. This way to you can inspect the road for debris. I would hate to run over a piece of debris going 150mph. I have read several formulas to calculate your top speed. Garbage in my opinion. Get that car out there in the desert or where ever it is you can do it safe for others. You may die if your tire blows out but that is the chance you take. My 1988 max speed was 146mph before the rebuild. That was a engine with 195,000 miles on it. Max RPM was 4400-4500 in OD. Since my rebuild I have yet to go over 140mph. My RPM's were 3500-3700. My new cam will allow me to hit 5300rpm so who knows ?

Feb 1, 2014 | 10:33 AM

c4cruiser

Team Owner

Joined: Dec 1999

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From: Lacey WA RVN 68-69

NCM Sinkhole Donor

FWIW, one reason for not posting about how fast you can go (or have gone) on the street is it's a very easy way to get a thread locked. The mods take a dim view of talking/bragging about street racing or driving on public roads at extremely high speeds.

Sure some people do it, but there is always a risk of something going wrong. Bad tires, bad suspension, bad traffic, bad driver.... If nothing else, a huge traffic fine and maybe a trip to the slammer if the cops catch you.

At the 3 road race courses in my area, my '87 will easily hit 125 in 4th gear (4+3 trans) at around 5300 RPM on the straights. With your car having a 6-speed manual, 5th gear should bring 145 to 150 with no problems, assuming there is enough distance to get to max RPM in 5th.

Feb 1, 2014 | 10:39 AM

Doulop

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Alright. Thanks everyone for your info and concern. I never let 5th gear take me to the top like I have read. I did find out through a dyno that my RPM gage is off by about 800 for some reason. It shows 5,000 when I am actually only at 4,200. Maybe going up past red line will get me there. And yes, this was on a closed course! Thanks everyone

Feb 2, 2014 | 12:41 PM

flyboyslc1

Melting Slicks

Joined: Apr 2012

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From: IOWA!!!

tachometer error

Quote:

Originally Posted by Doulop

I also have a 1991 6 speed and my tachometer also reads about 500 rpm high or so. I think the only way to get it to read right is to take the cluster out and have it repaired. I think the cost is about 3-400 for this.

steve

Feb 2, 2014 | 04:04 PM

mnstrlt1

Melting Slicks

Joined: Mar 2008

Posts: 3,022

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From: Chandler Arizona

Quote:

Originally Posted by flyboyslc1

Steve is essentially correct. This was a common problem on the 91'. You can repair it yourself if you're electronically savvy, and can soldier. Otherwise, I found that the cluster does, in fact, have to get removed and repaired. I swapped in another (properly functioning) cluster into my 91' (when I had it) and it didn't resolve the problem (I had a bouncing tach issue, which could also be a tach filter). The problem for 91' is that it doesn't have a conventional tach filter (several vendors sell a tach filter repair kit, which is intended for earlier cars). The 91' has a black box filter like the 92' and later models.

With that said, If the vehicle was in healthy mechanical order, I would think it could do 150 in 5th (prior to red line), here is a chart with the stock 3.45 gears

http://www.zr1specialist.com/HAT%20W...io%20chart.jpg

5th gear at 5,500 RPM is ~162mph.