Drove 1990 6 Speed

[1989 406]

First and foremost this post is not about which car is faster. These are some thoughts and I would like to hear some input.

I went and drove a 6 speed 1990 Corvette yesterday and felt that it had nice torque but seemed to loose it at the car got going. I have heard this was common for the L98 engine. I currently have a 1986 Mustang SVO with a good exhaust system, fuel pump and higher boost, which felt like it was a faster car. The Corvette felt great off of the line, but my 4 cylinder turbo felt like it was stronger higher up.

The only experience I have from a C4 was my father’s 89 supercharged, which was strong all the way through. I would consider making a move, but the performance has to be better then what I have and right now I do not currently have money for any kind of modifications.

How do you C4 owners’ feel about their performance? I do not know if possibly the 90 Corvette was not in great shape. Love the 6 speed.

Thanks.

 

[TedC]

I've owned two Mustang GTs (1985 and 1989) and two C4s (1988 and 1989). I still own the 1989 Vette. Also, I've driven both the 1985 and 1986 SVO Mustangs. For me, the difference is in the engine design and gearing. The 5.0 302 was good up to 5300 RPM, and had excellent manual gearing to match. Biggest issue was keeping the tires from spinning. When driving the SVOs, I found you had to keep the revs up due to the weak low end torque. SVOs had no issue out reving a stock 5.0. The L98 is not a high reving engine (less than 5.0 Ford). I have found the 6 speed with the L98 a poor match. The LT1 is a much better match to the 6 speed because a stock L98 runs out revs around 4700 RPM. The key with the L98 is leveraging all the low end torque.

 

[TWISTERUP]

I've owned two Mustang GTs (1985 and 1989) and two C4s (1988 and 1989). I still own the 1989 Vette. Also, I've driven both the 1985 and 1986 SVO Mustangs. For me, the difference is in the engine design and gearing. The 5.0 302 was good up to 5300 RPM, and had excellent manual gearing to match. Biggest issue was keeping the tires from spinning. When driving the SVOs, I found you had to keep the revs up due to the weak low end torque. SVOs had no issue out reving a stock 5.0. The L98 is not a high reving engine (less than 5.0 Ford). I have found the 6 speed with the L98 a poor match. The LT1 is a much better match to the 6 speed because a stock L98 runs out revs around 4700 RPM. The key with the L98 is leveraging all the low end torque.

I agree 100% and if that's not enough...then drive a LT4..they love turning some rpms and as was stated the gearing/performance axle makes a huge difference.

 

[G Winter]

I have a 90 convertible . I have found you want to get through the first 2 gears quick, don't over wind. Third gear
use a little more rpm same with 4th.
The low end torque is your friend, it excellerates the car
quicker than the rpm in the lower gears. Hope I worded that
so it makes sense.
I do believe a 5 speed would have been better suited for the
L98. The only thing is it might hurt the MPG with the single overdrive, unless a 3.01 gear was used in place of the 3.31.
The little larger gears spacing in a 5 speed should be better.

Glenn

 

[1989 406]

Thanks for the input. I think an LT1 would be out of my price range.

Also, the car was leaking a little bit of oil. This seems common for Vettes around that year, that I have checked out. Maybe the ones I look at, are not taken care of too well.

 

[TedC]

The rear seal on the intake manifold is a common cause of oil leaks on the L98s. If you get a chance to drive an auto L98 with the optional 3.08 axle, give it a try. This gear is a great match to the L98 automatic, and pulls very strong in 1st and 2nd gear. I'm after dead stop get-up-and-go performance to 1/8 mile which is why I like the L98. Just ask my neighboor who didn't like the simple fact that my old vette could walk his 6 speed (close ratio) 350Z. He just traded the Z in for a Porsche 911.

 

[MBDiagMan]

Yes, the L98 runs out of steam at about 4,500 RPM. This is because at the time they were designing the TPI system, GM had abandoned the 350 and were concentrating on the 305. The TPI system was designed for a 305 and then the 350 came back as they were marrying the TPI to the Corvette engine.

The TPI makes a real torque monster out of the 350, but since horsepower is a calculated value, rather than a measured value, the horsepower number is quite low.

For me, I thorughly enjoy my 4+3 L98. I'm not looking to win any races, so the torque makes it fun to drive.

My $0.02,