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Just snagged a pretty decent 1990 L98 convertible and it is a dog! It seems to run ok with no missing or weird noises but is a turtle compared to my LT1 car.
Your LT1 has more powerband and 30-40 more HP. The L98 was all done by 4500 or so, where your LT1 keeps pulling. So, yes, I would imagine a stock L98 would feel slow to you.
Just like my 1st LS1 car made my old LT1 Z28 feel like a turd.
Gradually drive the car to 3200 RPMs in first gear. Release the gas pedal and then immediately floor the pedal. It shouldn't feel slow when you do that.
Check some stuff like ignition timing & fuel pressure. It could have a 2.56 rear gear & the convertibles had quieter mufflers that cut a little (5hp) power.
2020 Corvette of the Year Finalist (appearance mods)
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Originally Posted by ex-x-fire
Check some stuff like ignition timing & fuel pressure. It could have a 2.56 rear gear & the convertibles had quieter mufflers that cut a little (5hp) power.
Gearing would make more of a difference than the engine IMO. As far as "feel", I always thought L98s and LT1 felt fairly similar in around-town get-up-and-go. Yes, the LT runs up a bit higher but the L98 has a bit better mid-range punch.
Under 50mph, you shouldn't be able to tell the difference. On the hwy, from 50-80, definitely. So, gearing and the conditions you are comparing matter.
the car in the picture looks to be a 91 or newer. the 90's had the old style black beltline, different front and rear bumpers. looks to be a pretty decent looking vert. my old 89 6-speed coupe used to run mid 12's with a pretty much stock motor, didn't even have headers. a die grinder on the intake system and exhaust manifolds and a few other mod, it would smoke a stock lt1.
The car is a 90 with newer bumpers. I'm sure it has a 2.59 as does my 92.
My 92 will try to go sideways when it hits 2nd. This car has nowhere near the oomph.
It doesn't have any knocks or misses or rich exhaust or anything obvious that would be killing power. I will tinker with it including timing etc to make sure all is right.
Stock C4’s will never be as fast or quick as a stock C5, C6, or C7. Back in the 80’s a C4 was the “top dog” for its day. Carful how you use the word “dog”, we C4 owners are fierce about our cars.
Stock C4’s will never be as fast or quick as a stock C5, C6, or C7. Back in the 80’s a C4 was the “top dog” for its day. Carful how you use the word “dog”, we C4 owners are fierce about our cars.
The car is a 90 with newer bumpers. I'm sure it has a 2.59 as does my 92.
My 92 will try to go sideways when it hits 2nd. This car has nowhere near the oomph.
It doesn't have any knocks or misses or rich exhaust or anything obvious that would be killing power. I will tinker with it including timing etc to make sure all is right.
Take it to the dragstrip and see what it runs. Post the results and we'll let you know if it's running OK.
on a high 80 degree day my stock 1991 coupe auto with 2.59 gears felt slow but ran a 8.99 at 78.8 mph(I was guessing a 9.4-9.5) in the 1/8 th mile which I think is a very high 13/14.0 in the 1/4 I was surprised.
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St. Jude '03 thru '24
Originally Posted by bassackwards
Just snagged a pretty decent 1990 L98 convertible and it is a dog! It seems to run ok with no missing or weird noises but is a turtle compared to my LT1 car.
My 1985 C4 L98 is in the "doghouse", she blew transmission no.5 last week. Bad dog!
Seriously though there is not much difference in performance between a standard well maintained L98 or LT1.
Early C4 will do low 14 quarters standard, mid C4 still L98 (90-91) high 13 sec quarters late C4's mid to high 13 sec quarters.
Half a second difference over a quarter mile over the generations of C4, is not noticable in the drivers seat unless its timed.
With so little quarter mile time difference both engine types, there has to be a reason your 90 doesn't feel as quick as a LT1.
Give your 90 a tune up, remember the harmonic balancer can slip so the 6 degrees advance may be up to 20 degrees either way.
My 1985 C4 L98 is in the "doghouse", she blew transmission no.5 last week. Bad dog!
Seriously though there is not much difference in performance between a standard well maintained L98 or LT1.
Early C4 will do low 14 quarters standard, mid C4 still L98 (90-91) high 13 sec quarters late C4's mid to high 13 sec quarters.
Half a second difference over a quarter mile over the generations of C4, is not noticable in the drivers seat unless its timed.
With so little quarter mile time difference both engine types, there has to be a reason your 90 doesn't feel as quick as a LT1.
Give your 90 a tune up, remember the harmonic balancer can slip so the 6 degrees advance may be up to 20 degrees either way.
Here is my bad dog
Well I'll bet yours does run!
It has way too much oil in it according to the dipstick, like an inch too high. I'm starting with draining that and properly routing the plug wires.
It has way too much oil in it according to the dipstick, like an inch too high. I'm starting with draining that and properly routing the plug wires.
Hi
Another thing to look at is the catalytic converters, you should have 3x cats on your 90. 2x pre cats just after the exhaust manifolds and one main cat, they can clogg up. Or disintegrate and clog your main cat, that could explain the big power difference you are describing.
The mufflers can block up also, check the flow get someone to rev the engine and make sure you have an even exhaust flow each side.
As long as the Throttle Position Sensor is checked, set to 0.54 volts dc ignition on. Check it goes to around 4 volts dc with full accelerator travel. You should be good to go, check your timing as well.
Perhaps replace the fuel filter, check your fuel presssure it should be around 38 psi. Rev the engine and make sure it does not drop below that, having a fuel pressure gauge with a long hose so you can tape it to your windsheild helps.
Good luck.
Last edited by gerardvg; Jun 14, 2015 at 10:08 PM.
Another thing to look at is the catalytic converters, you should have 3x cats on your 90. 2x pre cats just after the exhaust manifolds and one main cat, they can clogg up. Or disintegrate and clog your main cat, that could explain the big power difference you are describing.
The mufflers can block up also, check the flow get someone to rev the engine and make sure you have an even exhaust flow each side.
As long as the Throttle Position Sensor is checked, set to 0.54 volts dc ignition on. Check it goes to around 4 volts dc with full accelerator travel. You should be good to go, check your timing as well.
Perhaps replace the fuel filter, check your fuel presssure it should be around 38 psi. Rev the engine and make sure it does not drop below that, having a fuel pressure gauge with a long hose so you can tape it to your windsheild helps.
