C-3 engine modifications

[Jon]

I just inherited a 1977 Corvette. it has been sitting for the past few years and will need a new motor and probably a new transmission. I have been looking into replacing the motor and transmission with an engine and transmission out of a newer (1999-2003) Corvette.

My questions are:
how difficult would the change over be?
Would the stock motor mounts work?
would it pass the overly strict smog laws in California?
And do you knpow of a company that could custom make a wiring harness with that configuration?

[Daniel S.]

Re: C-3 engine modifications

C-5 Corvettes(97-04) have rear mounted transmissions. Will not work in a C3 application.

Best bet would be to go with a GM crate engine if your looking for a newer motor.

[Joe L.]

Re: C-3 engine modifications

John and Dan-----

The Gen III small block can be used with a conventional transmission located behind the engine. Camaros and Firebirds (may they rest in piece) were so-configured. Plus, the Gen III engines used in most late model trucks have conventional transmission location. So, it's no problem to use a Gen III with a transmission attached directly to the engine. The rest of the equation gets more complicated:

1) It would be quite difficult

2) Engine mount locations are different on Gen III engines so some sort of adapter would be needed. I would expect that they're available, though, in the aftermarket;

3)It would NOT be smog-legal under California requirements (or, even under federal requirements);

4) I'm sure that harnesses are available. If you purchase an LS-1 engine under GM #25534322 an ECM is included which will allow the engine to be used with a 4L60-E (THM-700R4 with electronic control) in a pre-78 vehicle. This complete engine assembly GM lists for $8,430.

[Patrick H.]

Re: C-3 engine modifications

Just because it has been sitting for a few years does not mean it will need a new motor and/or transmission.

Of course, I have no idea under what circumstances it has been sitting. But, if in a garage or any semblance of such, I doubt it will need that level of replacement. The only time I can virtually guarantee you will need both is if it happened to be under water before or during storage. Save that, there are much easier ways to resurrect a powertrain.

Just my thoughts.

Patrick

[Duke W.]

Re: C-3 engine modifications

I agree with Patrick. A thorough inspection and testing are warranted before
you throw it away. Check all the fluids, install a fresh battery, disconnect the HEI electrical connector, remove the spark plugs, and see if it will crank.

If it does, a thorough fuel system check is in order up to and removing the fuel tank for a thorough inspection and repair as necessary, cleaning all the fuel lines out, and installing a fresh filter.

As long as the transmission has fluid, a drive will tell you if it's functioning properly.

If the engine does need major work, it would be cheaper and in the long run
probably improve the value of the car if you rebuilt the original engine. Being as how its basically a '70 300 HP 350 with a lower compression ratio, a single catalytic converter and a bunch of add on emission equipment, if you don't have to deal with emission testing it can be backdated to earlier 300 HP spec or even upgraded to near L-82 or LT-1 spec.

Once the engine is running all fluids should be changed - engine oil and filter, trans fluid and filter, axle oil, brake fluid, and antifreeze.

Duke

[John Liner]

Re: C-3 engine modifications

Duke, Patrick you are right as usual.
My 79 had been sitting for 5 years, sometimes outside, most of the time outside.
I wanted to keep the car as close to original as I could. I had to do everything that Duke mentioned, plus I had the auto trans. rebuilt by a good shop. The engine did also require some work because of the past owners abuse,
but with this said I didn,t spend more than $1,500 - $2,000. Did all the removal and instillation myself and I have a new powertrain that I can drive daily. There is no need to try something exotic or costly. I have a dependable ride that meets all Goverment regs and passes all tests for emisssions.
Just my 2 cents worth.
John

[Patrick H.]

Re: C-3 engine modifications

And, I hate to bring economics into play, but what's the top value for the car? $15000 on a good day (Top Flight car), more like $8k-12k on most days for a good driver?

You could easily spend $6k on the engine and trans just for parts alone if you purchased them new or in similar condition. So unless the car was free...

Patrick

[Dave Suesz]

C-3 engine modifications

Others have answered your questions, but: best value would be repair/modification of your existing drivetrain, stock if you are a purist, but tremendous increases in power are possible while leaving stock appearance intact. (Think passing DMV inspection). I have seen engines which sat in cars in junkyards for years start right up when spun, and I mean in rainy Pennsylvania, not some desert state.

[Jon O'Neil]

Re: C-3 engine modifications

The car has been sitting on a covered back porch(Stored sans fuel pump) for the past 10 years. the motor was rebuilt and installed, then my fathers health started to decline. as of right now I am just looking to get it back on the road to give him 1 last ride in it before the end, if you know what I mean.

the front end was torn apart when the engine was reinstalled and is quite litterally sitting on blocks (Jack stands on the frame front and back)

Any information anyone can give me on recommended shops or auto parts places it would be a great help.

Thank you

Jon

[Dave Suesz]

OK, a few...

Dr Rebuild, Paragon, and Corvette Central, in that order. For your purposes, do it stock, do it right, but don't overdo, and do it quick. If you are near Philadelphia, I could say where, but even your local Chevy dealer would probably be OK, as long as you have an understanding about parts. My Dad passed away about a year ago, and Id've given anything to give him that one last ride.

[Patrick H.]

Re: C-3 engine modifications

Jon,

Let us know where you're at, and there may be another member near you who could recommend shops to evaluate your car.

Patrick