C4, just a few questions.
Discussion
Hi guys,
Just popped over from the wedge forum. I,m currently trying to sell my 400se with a view to possibly purchasing a C4. Hope you can help me out with a little information.
(1) Are there any issues I should look out for on this model (ie chassis rot etc)
(2) I,m guessing that service history is important as with TVR's.
(3) What sort of fuel economy should be expected from a C4 (not a huge issue as only a weekend toy, but worth knowing in advance).
(4) Are there any particular options that I should look for on a car ?
Just popped over from the wedge forum. I,m currently trying to sell my 400se with a view to possibly purchasing a C4. Hope you can help me out with a little information.
(1) Are there any issues I should look out for on this model (ie chassis rot etc)
(2) I,m guessing that service history is important as with TVR's.
(3) What sort of fuel economy should be expected from a C4 (not a huge issue as only a weekend toy, but worth knowing in advance).
(4) Are there any particular options that I should look for on a car ?
Ian V said:
Hi guys,
Just popped over from the wedge forum. I,m currently trying to sell my 400se with a view to possibly purchasing a C4. Hope you can help me out with a little information.
(1) Are there any issues I should look out for on this model (ie chassis rot etc)
(2) I,m guessing that service history is important as with TVR's.
(3) What sort of fuel economy should be expected from a C4 (not a huge issue as only a weekend toy, but worth knowing in advance).
(4) Are there any particular options that I should look for on a car ?
1. Not specifically. You should look mainly for repair damage on the main bodywork as the fibreglass sometimes gets porous and the air starts to cause the paint to bubble. This is expensive to correct as are any paint defects. The chassis is a backbone steel affair and there are no real issue. The interiors on earlier cars are brittle and the carpets fade and so check it's all screwed together properly and nothing's broken. The digital instrument pack is prone to failing on earlier models too. Basically the 1985 C4 puts out 235bhp, this increased to 250bhp up to 1991. The first year of the facelift was 1991 which retained the 250bhp L98 and the 1992 got the 300bhp LT1.
2. Service history is important to the extent that you neeed to see a sheaf of bills or proof of regular oil and fluid changes. Bear in mind it's a pushrod V8 and fluid changes are about it on maintenance. Upkeep is obviously important but there are no Chevy dealers to stamp any books. Check the disc rotors and pad changes and that everything works including the a/c.
3. Not a C4 strong point but when I had my 1985, a fast blast down from North wales would yield about 19 USmpg which is about 22-23mpg. Around town, there's an instant readout which can fall to not much at all but the TPi is pretty good for it's time.
4. Z51 suspension although it can be hard. Try to avoid 84 C4's as they had a 205bhp Crossfire engine and very hard suspension.
I'll add a couple of things to look for:
Weather-stripping - the seals are moulded foam which when worn look crap and leak. They are very expensive to replace.
The wheel bearings are in sealed for life hubs (about £200 each IIRC).
Early cars had a digital dash (which I rather like) this is easily damaged and difficult to get parts for.
Popping or squealing from the optional Bose stereo means rebuilt amplifiers are required.
Auto's give the least trouble but hurt performance. The 88'-on 6-speed manual is better than the more troublesome 4+3 OD trans. Many owners regularly change the engine oil but neglect the trans fluid, which is a shame.
When trying to judge the condition of the interior look at the inside bolster on the passenger seat - it takes 5 minutes to swap the seat backs to hide wear.
Try removing and replacing the roof panel. This is difficult on a bent car.
I averaged 24UKmpg on my daily 10 mile commute to work (91' Vette). I drove my C4's every day for 2 years and needed a breakdown truck twice - both Delco alternator failures. Under rated for the job or just pants, don't know which.
Options: The selective ride option is nice, but obviously more to go wrong. I like the optional glass roof, makes the interior feel bigger.
Weather-stripping - the seals are moulded foam which when worn look crap and leak. They are very expensive to replace.
The wheel bearings are in sealed for life hubs (about £200 each IIRC).
Early cars had a digital dash (which I rather like) this is easily damaged and difficult to get parts for.
Popping or squealing from the optional Bose stereo means rebuilt amplifiers are required.
Auto's give the least trouble but hurt performance. The 88'-on 6-speed manual is better than the more troublesome 4+3 OD trans. Many owners regularly change the engine oil but neglect the trans fluid, which is a shame.
When trying to judge the condition of the interior look at the inside bolster on the passenger seat - it takes 5 minutes to swap the seat backs to hide wear.
Try removing and replacing the roof panel. This is difficult on a bent car.
I averaged 24UKmpg on my daily 10 mile commute to work (91' Vette). I drove my C4's every day for 2 years and needed a breakdown truck twice - both Delco alternator failures. Under rated for the job or just pants, don't know which.
Options: The selective ride option is nice, but obviously more to go wrong. I like the optional glass roof, makes the interior feel bigger.
The Classic Corvette Club UK website may help you - there is also a technical section which may give an impression of the sort of problems to expect and how to fix them.
Try this link for starters:
www.corvetteclub.org.uk/viewforum.php?f=79
For C4s if you have the budget go for a 1992 or later. They had the more powerful LT1 engine and updated front and rear ends..
Try this link for starters:
www.corvetteclub.org.uk/viewforum.php?f=79
For C4s if you have the budget go for a 1992 or later. They had the more powerful LT1 engine and updated front and rear ends..
IMO i think the C4 chassis was over engineered and although the bodywork is light this is one tough unit,made from galvanised steel its only problem if you can call it that is it blackens,a good wire brush will shine that up,if thats what your in to.
The interiors on all vettes are simple,there is some flare depending on the era you buy but the C4's were really nothing to write home about,the materials they use are not always the best and if you are one of these interior cabin snobs then the vette wont satisfy your taste,ive heard loads of detrimental remarks concerning the interiors but in my mind they do the job and wont age in design as much as some of these radical interiors that you see in some perfomance cars these days,ok they might use better materials and grab your attention with their bright colours but those of us that remember the Rover SDI's a few decades back with their radical design and light leathers know how quickly these can decline and look shabby,on the other hand the vette interior will do its job for more years to come.
Steering,brakes and suspension maintenance is easy enough with new and second hand parts in abundance and a home mechanic shouldnt have too much difficulty coming to grips with replacing parts,there are pages of corvette aftermarket dealers lining up to sell you their goods and the exchange rate as it is at the moment makes buying from the states an attractive proposition,ive ordered parts on a friday only for them to turn up on the following monday.
As has been mentioned the 350 chevy came in various states of tune and if you are adventurous then its worth considering the ZR-1 rated up to 405 hp standard,these are at their lowest price and would be a worth while investment if thats in one of your criteria,which ever one you chose the engines are straight forward and reletively simple to maitain and with the amount of keen enthusiasts in the UK you are never short of back up and advice,reliability on a well maitained chevy motor shouldnt be an issue and only a couple of weeks back i witnessed a near twenty year old C4 on the dyno with 155,00 miles on its clock,it didnt miss a beat all the time it was on there and still produced a near factory power rating without the slightest hint of blue smoke.
I understand on some years they run an "optispark" which is situated under the water pump and have heard this to be an achilles heel,ive heard several owners have problems here.
Good Luck in your search.
The interiors on all vettes are simple,there is some flare depending on the era you buy but the C4's were really nothing to write home about,the materials they use are not always the best and if you are one of these interior cabin snobs then the vette wont satisfy your taste,ive heard loads of detrimental remarks concerning the interiors but in my mind they do the job and wont age in design as much as some of these radical interiors that you see in some perfomance cars these days,ok they might use better materials and grab your attention with their bright colours but those of us that remember the Rover SDI's a few decades back with their radical design and light leathers know how quickly these can decline and look shabby,on the other hand the vette interior will do its job for more years to come.
Steering,brakes and suspension maintenance is easy enough with new and second hand parts in abundance and a home mechanic shouldnt have too much difficulty coming to grips with replacing parts,there are pages of corvette aftermarket dealers lining up to sell you their goods and the exchange rate as it is at the moment makes buying from the states an attractive proposition,ive ordered parts on a friday only for them to turn up on the following monday.
As has been mentioned the 350 chevy came in various states of tune and if you are adventurous then its worth considering the ZR-1 rated up to 405 hp standard,these are at their lowest price and would be a worth while investment if thats in one of your criteria,which ever one you chose the engines are straight forward and reletively simple to maitain and with the amount of keen enthusiasts in the UK you are never short of back up and advice,reliability on a well maitained chevy motor shouldnt be an issue and only a couple of weeks back i witnessed a near twenty year old C4 on the dyno with 155,00 miles on its clock,it didnt miss a beat all the time it was on there and still produced a near factory power rating without the slightest hint of blue smoke.
I understand on some years they run an "optispark" which is situated under the water pump and have heard this to be an achilles heel,ive heard several owners have problems here.
Good Luck in your search.
Thanks for all the replies guys. Certainly food for thought ! 
I wasn't aware that the 350 lump had so many states of tune. Coming from a wedge TVR I would expect I ought to look for a more powerful lump. Just out of interest does anyone have the performance figures for the various engine tune options? 
Anyone want to buy a wedge !!!
Oh, I,ve just joined the CCCUK forum as well.
>> Edited by Ian V on Tuesday 4th April 08:15
I wasn't aware that the 350 lump had so many states of tune. Coming from a wedge TVR I would expect I ought to look for a more powerful lump. Just out of interest does anyone have the performance figures for the various engine tune options? Anyone want to buy a wedge !!!
Oh, I,ve just joined the CCCUK forum as well.
>> Edited by Ian V on Tuesday 4th April 08:15
There was a local guy in Cardiff who had a TVR 350SE when I had my '85 Corvette. After I blew his doors off, he sold his 350 and bought a Camaro Z28, failing to appreciate that the V8 only produced 205bhp in a heavier car. He eventually returnmed to the TVR fold via a troublesome Griffith without ever trying the Vette.
My 2p's worth:
C4 alternator failures - standard alternators, certainly for the 80's cars, were, I understand a little weak (few people have told me this...) - reason I don't know is mine's never failed but believe that's because a common swap was to put one of the Caddillac ones on!
The chassis is not a backbone unit - it is actually a 'perimeter frame' - that is in part demonstrated by the relatively high sills, which house the relatively large box section. It doesn't really rust, but they can be susceptible to crash damage. As Cliff said, it's a galvanised unit. There is also an aluminium 'C Beam' that links the back of the transmission to the front of the diff.
Options - Z51 - makes the car a very lively oversize go-kart. I enjoy it, although it does make the car rattle more, and also it does really let you know about poor road surfaces! Z52 and stock suspension options are more refined, and make the car a little mor enormal, in truth without losing any speed (contemporary road tests produced very similar times for each option, and often favoured the non Z-51 options) Being a yank you could have the Vette in many different combinations of colours, leather, electrics and so on! Whilst all are reasonably equipped, you may want to consider whether things such as a leather interior (or cloth for longevity) are important to oyu, and climate control or standard AC, as for the other major option -
Auto vs manual - 700R4 auto box in the earlier cars (pre-1990 ish!) was a good box, and relatively durable, and should not be looked at as a low performance option, in fact, it was quicker everywhere than the 4+3 manual offered, for an 85 car times were 0-60 in 5.7 s for the auto and 6.0 for the manual, both top speed quoted as 150mph and quarter mile times for the two still saw the auto quicker, the manual just kept losing time through the gear changes. Horsepower, quoted as 205hp for the 84, 230 for the 85 (it got tuneed port injection) went up 5hp for the ally headed 86's eventually hitting 245 bhp by the end of the eighties on the older L98 engines. As someone said, the later LT1 cars had 300 hp, rising to 330hp (Nige - is that right?) for the LT4 (Grand Sport) engined cars. These ones took top speed to over 160 I believe. Alternatively of course there is the LT5, Lotus designed 32 valve V8 available from 1990, starting with 375 hp up to 405 in 94 (think). Obviously considerably more performance, manual only and 180mph ability.
The six speed manual is much improved over the 4+3, adn I believe shifts the balance back to the manual being quicker than the auto. I don't think electronic control of the auto box helped in later life though, the earlier boxes seem a bit more instantaneous in their activity and a little more brutal.
Most of this is applicable to the pre-90's versions of the C4.
Hope this helps - suggest you try a few before you make a decision, performance between different C4's, even with the same year and spec can be quite different, when boxes don't work as they should or cats are blocked etc...
C4 alternator failures - standard alternators, certainly for the 80's cars, were, I understand a little weak (few people have told me this...) - reason I don't know is mine's never failed but believe that's because a common swap was to put one of the Caddillac ones on!
The chassis is not a backbone unit - it is actually a 'perimeter frame' - that is in part demonstrated by the relatively high sills, which house the relatively large box section. It doesn't really rust, but they can be susceptible to crash damage. As Cliff said, it's a galvanised unit. There is also an aluminium 'C Beam' that links the back of the transmission to the front of the diff.
Options - Z51 - makes the car a very lively oversize go-kart. I enjoy it, although it does make the car rattle more, and also it does really let you know about poor road surfaces! Z52 and stock suspension options are more refined, and make the car a little mor enormal, in truth without losing any speed (contemporary road tests produced very similar times for each option, and often favoured the non Z-51 options) Being a yank you could have the Vette in many different combinations of colours, leather, electrics and so on! Whilst all are reasonably equipped, you may want to consider whether things such as a leather interior (or cloth for longevity) are important to oyu, and climate control or standard AC, as for the other major option -
Auto vs manual - 700R4 auto box in the earlier cars (pre-1990 ish!) was a good box, and relatively durable, and should not be looked at as a low performance option, in fact, it was quicker everywhere than the 4+3 manual offered, for an 85 car times were 0-60 in 5.7 s for the auto and 6.0 for the manual, both top speed quoted as 150mph and quarter mile times for the two still saw the auto quicker, the manual just kept losing time through the gear changes. Horsepower, quoted as 205hp for the 84, 230 for the 85 (it got tuneed port injection) went up 5hp for the ally headed 86's eventually hitting 245 bhp by the end of the eighties on the older L98 engines. As someone said, the later LT1 cars had 300 hp, rising to 330hp (Nige - is that right?) for the LT4 (Grand Sport) engined cars. These ones took top speed to over 160 I believe. Alternatively of course there is the LT5, Lotus designed 32 valve V8 available from 1990, starting with 375 hp up to 405 in 94 (think). Obviously considerably more performance, manual only and 180mph ability.
The six speed manual is much improved over the 4+3, adn I believe shifts the balance back to the manual being quicker than the auto. I don't think electronic control of the auto box helped in later life though, the earlier boxes seem a bit more instantaneous in their activity and a little more brutal.
Most of this is applicable to the pre-90's versions of the C4.
Hope this helps - suggest you try a few before you make a decision, performance between different C4's, even with the same year and spec can be quite different, when boxes don't work as they should or cats are blocked etc...
Technically the C4 had a fully welded galvanised birdcage uniframe but used a Lotus-style steel backbone drivetrain. A bolt-on aluminium extansion held the rear bumper in place. The Gran Sport had a standard 330bhp in the LT4 engine although the LT4 was available as a $1450 option but as it came only with the 6 speed manual, the take-up wasn't as great as you'd imagine with the automatic-loving American buyers. You can tell an LT4 equiped car as it has an 8000rpm tacho instead of the stock 6000rpm item and the throttle body bears the Gran Sport plate regardless of what car it was in.
Now I must stop as I'm getting the urge for a purple metallic 1996 C4 myself. They really had character these cars. Not the most capable cars in the world but immense fun.
Now I must stop as I'm getting the urge for a purple metallic 1996 C4 myself. They really had character these cars. Not the most capable cars in the world but immense fun.
(Anorak mode on - apologies)
Uniframe construction is where the body forms part of the chassis, this is not technically correct for a Corvette, as most of the bodywork (well, pretty much all) is not load bearing.
As for Lotus style, the lotus backbone is totally different. It is a chassis, onto which the the rest of the car is built. The aluminium (it is not steel) C-beam on the C4 is there to tie the powertrain together, and does not from it have mounted the suspension, engine and bodywork as the Lotus backbone does. Also the construction is totally different, the Lotus is a sheet steel welded afair, about the length of the wheelbase, whereas the Corvette beam is merely the distance between the box and the diff.
I'm sure other cars use this similar method of tying diffs to transmission, the Mazda MX5 is one.
NB C5 and 6 replace the C-beam arrangement with a torque tube, obviously this now ties the engine to the now rear mounted gearbox.
Uniframe construction is where the body forms part of the chassis, this is not technically correct for a Corvette, as most of the bodywork (well, pretty much all) is not load bearing.
As for Lotus style, the lotus backbone is totally different. It is a chassis, onto which the the rest of the car is built. The aluminium (it is not steel) C-beam on the C4 is there to tie the powertrain together, and does not from it have mounted the suspension, engine and bodywork as the Lotus backbone does. Also the construction is totally different, the Lotus is a sheet steel welded afair, about the length of the wheelbase, whereas the Corvette beam is merely the distance between the box and the diff.
I'm sure other cars use this similar method of tying diffs to transmission, the Mazda MX5 is one.
NB C5 and 6 replace the C-beam arrangement with a torque tube, obviously this now ties the engine to the now rear mounted gearbox.
franv8 said:OK trivia fans, I'm no expert on the C4 chassis but who said this?
Anorak mode - The aluminium C-beam on the C4 is there to tie the powertrain together.....
"I've seen things you people wouldn't believe...Attack ships on fire off the shores of Orion...I watched C-beams glitter in the dark near the Tanhauser Gate. All those moments will be lost...like tears in rain."
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