Hi!

My name is Andreas and I´m 33 years old.
I`m living in Germany in a small countryside town nearby Berlin.
I hope you guys can help me with my 1970 convertible project.
My "lady" is not a best buy and I already paid many many thousand Euro. I don´t tell you the whole story, because it is hard to believe.
It´s unbelieveable bad luck and a lot of cheating...
As a beginner they really try to cheat you everywhere.
Anyway, I want to repair and improve my Vette in the next years.

The specs of my car:

1970 July production convertible
ZQ3 300HP smallblock
3.08 rear axle ratio
Muncie 4 Speed

current tuning:
Corvette Central Deluxe 2,5" exhaust system with Magnaflow mufflers
Edelbrock Performer Plus cam
Edelbrock Thunder AVS 650 e-choke carburetor
Pro Comp PC21001 intake manifold
Pertronix breakerless Ignition
Koni red shocks
PU bushings
sway bar set front and rear with PU bushings from Eckler´s

I mainly like to improve the suspension and the engine power output.
Are my Pro Comp intake manifold and Edelbrock Perfomer Plus cam any good?
I significantly want more acceleration and horsepower with the original engine block. I assume that modern flowbench optimized heads and a more aggressive cam will improve the efficiency and horsepower.
It´s an old car I know, but is there any chance to further improve the suspension without losing too much originality?

Thanks and best regards,

Andreas

 

Heads would be the first thing to try. I would do 64cc aluminum heads with about 190-200cc intake ports. They should have CNC porting throughout for maximum flow. combine these with some 1 3/4" headers and you should pickup at least 50hp. Make sure to use approp. valve springs for your performer cam, as these type heads usually come setup for hyd roller cams. Figure $1500-2000 USD. It sounds like you're probably running about 350hp now at the engine with your current combo.
When you're ready to get more serious I would go to hyd roller camshaft with about 230 degrees duration 110-114 lobe centers and .600 lift. Hopefully less than $1500 installed. That will give you another 50hp to about 450hp at engine, but you'll lose a bit of power down low. But you've got the 4spd and I assume you hit the autobahn on occasion so I think you'll like it. You'll run out of gear before you run out of engine so you may want to later consider a TKO 600 tranny or the new RS600 5sp.

 

On the suspension, just keep the stock geometry and go with a kit from Vette Brakes or one of the other venders here. I like a firm suspension, so I'd go 550-600lb springs up front (coilovers?) and a 400lb Daytona rear fiberglass spring. 1 1/4" sway bar up front and no or maybe 5/8" bar in back. new shocks and upgrade wheels to 17X9 all around" to get some good rubber.

 

Andreas - I too installed the 550 lb front and 420 lb (composite) rear springs and rear sway bar from VB&P. It really made a difference with the handling and I can't wait to get better wheels/tires to take advantage of the upgrade.

The Edelbrock Performer Plus cam (204/214 @ 50???) is likely not helping your output at all and you will need to go more aggressive with the duration to really feel it.

Before choosing a cam, you will want to research the relationship between camshaft, rear-end gearing, head ports and header size. Then you want to consider how your choice will mesh with the driving you want to do. Finally, if your engine's bottom-end is still stock, you need to consider the upper rpm limit is probably not much more than 6,500 (to be safe). Large cams, large heads, and large headers will need higher rpms to realize their full potential.

OPNWIDE gave a good starting point for the engine upgrades. Depending on your preference for the Autobahn or back country roads, you may want 1.625" headers in lieu of the 1.75". His comment about losing power down low is right on. With 3.08 gears, you may decide you need more torque down low and less top end.

It certainly is a multivariable equation to solve but the trial and error is lots of fun!
AL

 

Hi Andreas,
I can't help with your questions, (I'm too much of a 'stock' guy), but will say WELCOME!!
I hope you're soon able to get your car running and driving as you'd like, so you can begin to ENJOY it.
We all like to see pictutes of new, old, cars so it woud be great if you can post a few. There are instructions on how to do it on the FAQ tab at the top of the page.
Good Luck with your Corvette!
Regards,
Alan

 

Hi, Andreas! I can only imagine how hard things are to get done there on an American car...but a '70 convertible is very, very nice and worth the effort!

If I was looking for the most bang for the buck this would be the first thing I would address. Some deeper gears (3.70) would make a huge difference.

A heads/cam swap would be next - and the answer here really depends on your budget. First step is to do a compression and leak-down test to ensure the bottom end is solid - how many miles are on the engine?

 

Hi,

I´ll try to upload photos in the evening.
What kind of online service do you prefer for upload links?

I like to keep the 3.08 rear axle ratio, because I sometimes use the Autobahn and countryside roads with a 60mph limit.
I feel the rev is already quite high and the shorter ratio will further downgrade the cruising. What I prefer is high torque and strong acceleration between 2000-5000rpm. I like to keep the original block and pistons for the next 2-3years, if the piston rings and bearings are in good shape. I guess the car has got 100.000-150.000 miles on it. The counter does not work...

I think my Edelbrock AVS650 carb is not aligned properly. I have plenty loud backfire if I´m revving to 4000rpm and then step off the throttle. At partial load around 2000rpm I sporadically notice misfire and bucking. The car is strongly smelling gasoline like inside...
Additionally my wife told me she can see blue smoke out of the exhaust after hard acceleration...
Some people say worn piston rings, other say defect umbrellas/valve sealings or an oil sucking PCV valve...
The oil pressure gauge indicates maximum pressure above 2000rpm.
I "hope" the heads and their inside parts are worn and I can just switch to new high performance heads.
I´m wondering if there´s a proven upgrade of my engine type out there with graphs from a dyno???

Best regards,

Andreas

 

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Nice looking convertible

 

Geiler Kiste!!
Willkommen ins Corvette Welt!!
Hier konnen sie alle die hilfe du brauchst finden. "Billa" weisst 'ne menge, uber motor kombinationen, USW. Schick' ihm mal einen PM mit fragen.
F%@# for TUV!!!
MEHR BILDER!!!
-C-

 

Beautiful car!!!

Given the price of gas, I can understand keeping the gears

It sounds to me like step one is a very throrough tune, starting with setting the timing per the sticky and then moving on to the carb. I expect this tune will significantly improve power and fuel economy.

After that, I would look at a mild cam swap to move the power band down. I would look at something like the CompCams P/N 12-231-2; It's a "4x4" or "RV" type cam that produces power at lower RPM than a typical performance camshaft.

http://www.compcams.com/Company/CC/c...x?csid=94&sb=0

I'd wait on any other changes until you get the tune done, and then inspect the suspension...because on a C3, there's money to be spent there!

 

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Hi,

I´ll have better pics very soon...

OK, first step is checking the ignition and carb.
How can I find out if there´s oil leakage through the piston seals, or valves, or the PCV vent of the valve covers?

A roller cam makes sense above 5500 rpm, only?
I want to invest into good quality low wear parts, like the cam, pistons, spings, tappets and so on.
Does anyone has got experience on a tuned 300HP base engine?

Best regards,

Andreas

 

Beautiful car!

 

By the way, how do you mount the 15x7" Western Wheels centered?

I bought these at Ebay from Detroit Vintage Wheels.
Unfortunately the clearcoat or metal surface has got imperfections.
I couldn´t use the Spinner Caps here in Germany, so I sold them again...



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I can show you photos of the rotten windshield frame and A-strut...
This was expensive, about 5000 Euro...

 

This one has been my inspiration:



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No ideas?

 

Congratulations on your new Vette! I'm sure you'll enjoy it for years to come!

Those "Western Wheels" you were looking at are the best ever! The style is unique enough that you don't see them every day but they were a little to skinny for your Vette anyway.
"WW" also made 15X8.5 which is a little better.
They were rough cast so without some CNC work this is what they looked look...

I had mine powder coated and CNC'ed and this is how they came out.

 

If those are universal fit wheels with a slot for the lugs good luck. You would have to mount and balance the wheels on the car. And would have to repeat every time you take one off.