Modified c6

Dear all .. i am pondering buying this modified c6 zo6 . Does anyone know the car and honest constructive thoughts please …


The car has a forged pistons , modified induction , heads , valves guides redone / stronger , LG motorsport GSX5 cam/ full exhaust ,FAST lax intake , nick Williams throttle body , TR 6060 low ratio box , ARE dry sump , updated rad, centre force clutch , lg motorsport blistering coilovers , giro disc brakes .

would really appreciate comments both on price and whether it’s just an unuseable monster . If you know the car comments on condition welcome

many thanks

Yes, I saw the Autotrader ad for that car (Y7 LTR). And if I remember correctly, it was at one time owned by club members (father and son?) and they did an article on it in the club magazine. Think they modified it to be a track day weapon? If that's what you are looking for, looks like "fun" and a pretty unique car in the UK?

I believe it was owned by a chap called Greg then part exed with a dealer who traded it to another . I don’t necessarily want a track day weapon … the dealer is saying that the bilstein coilovers give a better ride than stock ? But I am struggling with that logic ..

Article on car in August 2015 Vette News by 1st/Original owner:

If that specific car and its respective modifications is really 'your thing' (and you are happy to pay the asking price) and understand/deal with the implication of maintenance etc of the modifications..... then yes proceed. But be beware C6Z06's (even stock) can (and will) 'bite' unwary and perhaps inexperienced drivers.
However there are a few things to condsider. A vehicle such as a C6 Z06 is considered by most Corvette enthusiasts (and generally) to be the very peak of 'excellence' of the C6 range. Despite later higher powered (and more expensive) supercharged options/C7 versions emerging 'bone stock' C6Z06's seem to have held values really well over the last 20 years. Unfortunately (as I have realised with my own C3) the chances of recouping much of the money spent modifying the car is minimal.....in fact it can severly limit the numbers of potential buyers.
I would suggest the price equivalent of that car would get you the very best Z06, with £10 to 15K less perhaps being the going rate for a stock vehicle depending on mileage/condition. Of course, actually finding a C6Z06 is a totally different matter.

Roscobbc said:

If that specific car and its respective modifications is really 'your thing' (and you are happy to pay the asking price) and understand/deal with the implication of maintenance etc of the modifications..... then yes proceed. But be beware C6Z06's (even stock) can (and will) 'bite' unwary and perhaps inexperienced drivers.
However there are a few things to condsider. A vehicle such as a C6 Z06 is considered by most Corvette enthusiasts (and generally) to be the very peak of 'excellence' of the C6 range. Despite later higher powered (and more expensive) supercharged options/C7 versions emerging 'bone stock' C6Z06's seem to have held values really well over the last 20 years. Unfortunately (as I have realised with my own C3) the chances of recouping much of the money spent modifying the car is minimal.....in fact it can severly limit the numbers of potential buyers.
I would suggest the price equivalent of that car would get you the very best Z06, with £10 to 15K less perhaps being the going rate for a stock vehicle depending on mileage/condition. Of course, actually finding a C6Z06 is a totally different matter.

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Roscobbc if it makes you feel better in what you spent

My 1999 C5 sticker was $44,000
Sent right to Chuck Mallett converted to a Mallett 435 cost, added $33,000 !
And a lot of that cost was for engine mods
Then I spent maybe another $5,000 for other mods

Clearly for selling it is a auto money loss of the mods and buyers wanting to pay as a base C5 and its age
and the car can no longer be treated as stock for maintenance and 3rd party repair parts

Then consider if where you live, and it requires SMOG testing if the car would pass those tests can be a real issue
I bought this in Ohio and shipped to Ca
Being new but from another state the aholes require out of state vehicles to even get title transferred it had to go through the I/M and I/M 240 SMOG tests
The long tube headers alone would cause failed, as that moves the location of from O2 sensors and CATs which in Ca is illegal
So my friend who owns a GM dealer in Ohio allowed me to license as a Ohio car where no SMOG test required
Had to do that yearly until I moved out of Ca.

A C6 Z06 biased for racing makes a total different thought on how to drive, maintain and any required testing

My concern is that the car is the asking price I am told the motor was refreshed with the addition of forged pistons 4k miles ago .. so should be ok but it does puff black smoke when revved on cold .. over fuelling or something else ?! The mods in the article sound sensible but having spoken to someone who has driven in the described it as having a very hard ride and a beast that will break traction in 3rd and 4th … yet the dealer had a letter from the previous owner describing it as useable with its mild cam and the bilsteins giving it a better ride than a stock car ! Comments please !

teamzr1 said:

Roscobbc if it makes you feel better in what you spent

My 1999 C5 sticker was $44,000
Sent right to Chuck Mallett converted to a Mallett 435 cost, added $33,000 !
And a lot of that cost was for engine mods
Then I spent maybe another $5,000 for other mods

Clearly for selling it is a auto money loss of the mods and buyers wanting to pay as a base C5 and its age
and the car can no longer be treated as stock for maintenance and 3rd party repair parts

Then consider if where you live, and it requires SMOG testing if the car would pass those tests can be a real issue
I bought this in Ohio and shipped to Ca
Being new but from another state the aholes require out of state vehicles to even get title transferred it had to go through the I/M and I/M 240 SMOG tests
The long tube headers alone would cause failed, as that moves the location of from O2 sensors and CATs which in Ca is illegal
So my friend who owns a GM dealer in Ohio allowed me to license as a Ohio car where no SMOG test required
Had to do that yearly until I moved out of Ca.

A C6 Z06 biased for racing makes a total different thought on how to drive, maintain and any required testing

View attachment 31894

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Jon, the American car market here in the UK has been (and to a degree still is) overheated for a number of years - Covid seened to put a stop to that and the prices being paid for American muscle 'tanked'.
Obviously people who had spent bundles on their cars ('if' forced to sell) lost money, or advertised the car at higher prices and didn't manage to sell.
And here in the UK (perhaps unlike the USA) the market hasn't really improved. Yes , really squeaky clean, rare and original matching number cars will always be snapped-up by experienced, knowledgeable afficionados looking at the longer term values. But here in UK C3, C4 and C5 Corvette prices (but not C1's and C2's) didn't really escalate in price at the same pace as many other classic marques and were (and still are to a degree) available at comparitive bargain prices.
Even stranger perhaps is that a 1967 Vette and 1968 Vette whilst totally different in style and apperance share much the same chassis and running gear with the same engine options........yet differ in values by up to 50% or more.

I’ve owned a c6 Zo6 for 4 years. It was stock and or road use you really do not need any more power. I thought I had a problem when on a charity day ride as the engine was backing off in third at 120. It turned out it was the tyres spinning up losing traction and backing off the power to stop me killing myself. They are great cars and so glad I owned one. I sold it when it was not for sale and was written off by the new owner not respecting its power and when to use it. I mo stick to stock as more saleable and once you enter modifications territory your limited to who can maintain it and who then wants to buy it.

David123 said:

My concern is that the car is the asking price I am told the motor was refreshed with the addition of forged pistons 4k miles ago .. so should be ok but it does puff black smoke when revved on cold .. over fuelling or something else ?! The mods in the article sound sensible but having spoken to someone who has driven in the described it as having a very hard ride and a beast that will break traction in 3rd and 4th … yet the dealer had a letter from the previous owner describing it as useable with its mild cam and the bilsteins giving it a better ride than a stock car ! Comments please !

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David, you're unlikely to get anywhere untill someone gives you full information on specific engine changes and operating parameters like comprehensive timing info, compression ratio, cam specification (and much more) to fully understand what has been done to the engine. Jon at Teamzr1 can 'burn' a new chip to perhaps sort that potential overfueling issue you have but it will be an uphill struggle.......

I see no content by the seller as they're giving any type of their warranty and for a car built for track, you need to think about that
No one here floating around cyberspace can give you a safe answer in buying it, you be the judge, and your hard-earned money

Being there is a yellow tow hook added to the front gives an idea what its purpose is
Going with coilovers with shocks, did they do this just on the front and also the rears
The spring rates may have been liked by the owner and good for track but crap of crummy public roads
If wrong springs for your drivestyle can mean too much over or understeer

Are the shock themselves adjustable, if not could be too harsh for street driving
That also means the suspension may have been changed and car sits real low, again not great for street curbs and potholes

This Z06 as to the above club write-up back in 2015, what was the reason they had to change pistons again not long ago ?
Again, would the car pass any required SMOG tests ?

Keep in mind the LS7 starts as a short block and GM bored the cylinder walls, so there were very thin cylinder walls that really
are brittle sleeves. Any internal issues and I have seen those crack and put rods through the block

For racing, I would bet they had to install larger flowing fuel injectors, great for track but too big for street and worse at idle and low speeds.
Add what CAM they used, again good for track but causes low vacuum for startup, idle and low speeds
This all means the guy doing the tuning has to be a master and if they F up than problems happen like you see rich exhaust on startup and requires you find a tuner that does quality custom tuning that can fix mods that do not work well together

FAST intake manifold, I have been doing custom tuning since 1995 and have seen countless C6 Z06s really screwed up and mostly from bad tuning, some so bad LS7 got blown to hell
FAST was designed really for an engine with boost and when crap went wrong, instead of blowing the engine that intake is 2 pieces and when pressure blows that intake instead blows apart, saving the engine
BUT due to crappy design over time and I have seen many the intake starts to warp and get air leaks causing odd and hard to find why engine runs like crap

Clutch, if a race clutch also might have a lighter flywheel
Where good for track, they can be a bitch getting the mass of the car moving from a stop and require higher RPMs to do that

LS7 engine runs hotter causing high coolant temps, question is did they go with a good higher flowing radiator and also a good engine oil cooler.
If not, can see issues in hot summer weather and engine running way too lean of AFR causing engine knock and do not forget a racer design can require you use the highest octane of gas

Of course, you know more HP and Tq means much shorter life on rear tires, costing about $400 plus US each

If this does not scare you, then go for it

I think im well placed to offer some advice.
I have a modified C6 Z06, had the car about 14 years and had the major mods done to cover for the valve drop issue.
Initially I just wanted the heads done for peace of mind, then when they came off it all changed, long story.
Anyway it has forged Wiseco pistons, overbored 0.005", an AHP 116 "California legal" cam, AHP stage 4 heads, milled 0.30", street ported with new solid exhaust valves and PSI springs. Also a new high flow air filter, stage 2 Monster clutch, new slave and a Tick master cylinder, a -10% ATI underdrive pulley , Hurst short shifter and a Borla over axle exhaust.
All this was put together and road tuned by Paul from Wortec,very well known and very good.
Paul calculated it was pushing around 625hp+.
Looking at the one above, compared to mine, that is a pure track car and will not be a very good road car. The cam alone will have it bucking at low speeds, i can feel mine at 30 mph, so i run in 3rd gear now instead of 4th at a steady 30, which doesnt last long .
The suspension will be hard, but could be softened on the coilovers im assuming. Mine is stock underneath but i think the torque is starting to test it on acceleration. Possibly new shocks would reduce it.
Dont know how bad that would be but mine is fkin scary, dont think ive been over 5500 rpm since the mods. Have had a tank slapper on racing an EVO X, and an Audi R8 V10 was handed his a**e 3 times in a row.
That might be too much for the road, and that spoiler looks crap to me, proper eyesore.

Also you need to know what that cam really is, as per the attached.

I am told the cam is an LG motorsports GSX5 cam but I am guessing they have that wrong and mean a G7x5 from your table . The previous owner described it as ‘not the most extreme cam that will happily pull from 1500 rpm. The valve gear has been replaced to match the cam with high quality springs . Cooler running plugs and nascar spec leads . Forged pistons were installed at recent refresh . Full lg motorsport headers and full exhaust . A Nick Williams 102mm throttle body , fast LSX manifold and uprated timing chains. The dry sump system has bern replaced with a full ARE race system . The car was mapped by TDI tuning in Essex I believe.Original gearbox replaced with a low ratio TR6060 which has transformed it on road and track. Updated Dewts rad with integrated oil cooler . The suspension is now Bilstein items made for LG motorsport front and rear . The ride is now better than the standard car. Rose jointed adjustable drop links and SKF racing hubs. Girodisc brakes and Centerforce pads’

Thats what the previous owner wrote when he sold the car to the dealer . Can of implies it’s ‘soft’ upgrades and not an out and out track monster ?! I would be very interested to know if that suspension is adjustable in height and as compliant as he makes out … thanks so much for your helped

LG's website does not give the full specs for those coilovers
Does not say what the spring rate is and some of their shocks are adjustable and some are not
Best if you find out which Bilstein/LG model used.


G7x5 looks like the power does not come on until about 3,000 RPMs
Best is to know what the LSA (Lobe Separation) is to know how much vacuum loss, which affects all high-end engine conditions

Be best to know if also when tranny type changed what rear end gear ratio if stock or what new ratio used

I believe the rear diff is stock .. if the TR6060 is low ratio i assume this will mean higher rpm on a motorway cruise ? 1000 rpm higher ?

If you wondered what the difference was between the OEM T56 double overdrive 6 speed T56 transmission as fitted to earlier C6Z06's - read this below.
And it will get confusing, very confusing. Bottom line is the TR6060 was used as an OEM transmission by a number of manufacturers..........and as an aftermarket item in various configurations suited for GM, Ford and other engines. Available with differing ratios for the overdrive 5th and 6th ratio's there also may have been some minor differences in intermediate ratios (I can't remember) - some of the OEM only applications had certain ratios that were specific to particular vehicles and not available to the aftermarket trade.......i.e Camaro ZL1 had an ultra low 1st gear ratio similar to the old Muncie M21/M22 as used in the 60's muscle cars. So was your transmission 'new' from the aftermarket trde.......or 'pulled' from a late model wrecked car.
The Differences Between the TREMEC T-56 and Magnum 6-Speed – TREMEC Blog: Get Connected

Thanks so much .. my eyes were glazing over towards the end of that !