L98 C4 Corvettes
Discussion
Quick question for you learned gentlemen...
I am hoping in a couple of years time to be in a position to get a C4 Corvette, probably an earlier one (as the LT1 engined ones seem to command a bit of a premium).
In the meantime, as part of my engineering HND, I have the honour of carrying out a research project. Happily, I have managed to be allowed to research the upgrading and tuning of the L98 as found in a C4.
So my question is very open really. Where would the best sources of information be to find this kind of thing out? Obviously UK based would be preferable. Is there anyone on here who has tuned an L98, or do most just save for an LT1 if the performance means that much to them?
Any help would be much appreciated of any form.
Also, I hope this doesn't come across as the post of a time-waster or dreamer. That isn't the intention.
Many thanks.
I am hoping in a couple of years time to be in a position to get a C4 Corvette, probably an earlier one (as the LT1 engined ones seem to command a bit of a premium).
In the meantime, as part of my engineering HND, I have the honour of carrying out a research project. Happily, I have managed to be allowed to research the upgrading and tuning of the L98 as found in a C4.
So my question is very open really. Where would the best sources of information be to find this kind of thing out? Obviously UK based would be preferable. Is there anyone on here who has tuned an L98, or do most just save for an LT1 if the performance means that much to them?
Any help would be much appreciated of any form.
Also, I hope this doesn't come across as the post of a time-waster or dreamer. That isn't the intention.
Many thanks.
Getting over to corvetteckub.org.uk is a good place to go.
I had an L98 auto for 13 years, recently upgraded to an LT1 6 speed.
Factoid for you on the L98, Chevrolet thought legislation would be passed limiting them to 5 litre V8's, so the castings for the L98 were made to suit a 305cu in displacement. Ehen this never materialised, they werent going to put the money in to retooling for the 5.7, so the engine breathes through long (22 inches) runners with a slightly smaller diameter than ideal. It results in a real stump puller of an engine, but iit's all done by 4000rpm where the asthma takes hold.
One of the most common tune up options is fitting an LT1 style "mini ram" inlet manifold. Derestricts the breathing, but loses some torque. Easily restored with the bore and stroke to the common 383 cu in upgrsde displacement.
I had an L98 auto for 13 years, recently upgraded to an LT1 6 speed.
Factoid for you on the L98, Chevrolet thought legislation would be passed limiting them to 5 litre V8's, so the castings for the L98 were made to suit a 305cu in displacement. Ehen this never materialised, they werent going to put the money in to retooling for the 5.7, so the engine breathes through long (22 inches) runners with a slightly smaller diameter than ideal. It results in a real stump puller of an engine, but iit's all done by 4000rpm where the asthma takes hold.
One of the most common tune up options is fitting an LT1 style "mini ram" inlet manifold. Derestricts the breathing, but loses some torque. Easily restored with the bore and stroke to the common 383 cu in upgrsde displacement.
Gains, well I guess it depends on how far you want to go. Effectively it's a first generation small block, so most of the tuning routes for that are valid. There are limits on the TPI system that pose some ceiling to power available, although some (sadly now obsolete) solutions exist. One is the Accel Superam. Another is the TPIS MiniRam - rumoured to have actually been copied by GM for the LT1. Both allowed better breathing of the engine, I think probably ideally coupled with the capacity increase to the ubiquitous 383ci (new pistons and the 400ci small block crank). Headers are good too (long tube, tuned length tubular exhaust manifolds) and of course a camshaft. Years ago I priced up a 400hp build which I think came up at around 4k.
Other options are of course forced induction, which I think is a valid and straightforward way with a few engines that struggle with top end breathing in top form (I had a 2.8 Turbo Technics Capri, the 2.8 never seemed to respond well to NA tuning, but certainly woke up with a turbo). Callaway did their twin turbo conversion (375-400 hp depending on year) but at the cost of the purchase price again (yes, nearly twice the price of just the standard Corvette), but Procharger is another good one. These are centrifugal superchargers, typcially achieving similar HP levels, I think today a kit is $3800, so just change to punds by the time it is shipped/imported here.
Beyond that it starts getting worth thinking about an engine swap, an LS gives a starting point of 350hp, and a loss of a lot of weight too.
Other options are of course forced induction, which I think is a valid and straightforward way with a few engines that struggle with top end breathing in top form (I had a 2.8 Turbo Technics Capri, the 2.8 never seemed to respond well to NA tuning, but certainly woke up with a turbo). Callaway did their twin turbo conversion (375-400 hp depending on year) but at the cost of the purchase price again (yes, nearly twice the price of just the standard Corvette), but Procharger is another good one. These are centrifugal superchargers, typcially achieving similar HP levels, I think today a kit is $3800, so just change to punds by the time it is shipped/imported here.
Beyond that it starts getting worth thinking about an engine swap, an LS gives a starting point of 350hp, and a loss of a lot of weight too.
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