57 FI wiring question.

[Bruce B.]

All things being the same other then switching from a 270 HP carburetted setup to Rochester FI (post 4360) what are the differences in the engine harness?

I am trying to diagnose a problem on a friends FI car and he has received conflicting opinions on the engine harness.

He has a anti siphon valve which I believe is connected to the 12 volt side of the ballast resistor.

All help is appreciated.

[John D.]

Re: 57 FI wiring question.

HI Bruce, There are many 57 wiring harnesses listed in the repro catalogs. There are 57early and 57 late. Ones for manual transmission and ones for automatic.
Ones for FI and ones for carb. An old Corvette World catalog I have lists 6 of '57 engine starting harnesses.
But forgetting the above the main difference between carb and FI harness is this.
The FI harness has a provision to plug in the electric "choke" harness.
Here is a typical phone call I get fairly often from restoration shops and owners. They don't know how to connect the FI choke harness up to the car and end up wiring it so the starting solenoid is hot all the time. Then all hell breaks loose as the car is running fat/rich and black smoke pouring out the exhaust and of course the plugs are fouled.

The fuel injection starting solenoid should only have 12V when the key is held in the starting position. Take your hand off the ignition key and the starting solenoid is dead. Now the red and black micro switch does control when you need the 12 V's.
If one has the correct repro harness in a 57 FI car and it's built correctly there should be no issues. Rumor has it that some of the early repro harnesses weren't made correctly and two terminals were crossed. Use a tester to insure you don't have such a harness.
Meanwhile Bruce I just remembered you have a 4360 FI car. So my friend take a look at the harness and see the connectors for the cold enrichment aka choke harness. But your early car would have the choke cover wire hooked up to the generator doesn't it. That's why the book list Early 57 and Later 57 harnesses for FI cars.
Now I am not that savy on 57 Corvettes so others may tear the above info apart. But at least I gave you some ideas. John

[Bruce B.]

Re: 57 FI wiring question.

John,

Thanks for the info, we are going to check out the FI car tomorrow.

I'll check the wiring on my 4360 after we get the other car running. I've got to tell you my 4360 has run like a fine swiss watch for the last 4000 miles, I love it.

Thanks again,

Bruce B

[John D.]

Re: 57 FI wiring question.

Bruce, Are you using '4520 nozzles in your '4360 FI unit?

[Bruce B.]

Re: 57 FI wiring question.

John,

I have the nozzles that come apart in my 4360, so they must be the later style, I forget what size they are.

I went over my friends Daves house today to try and find out why his 4520 would not run. He was driving the car and had to make a quick stop , he pushed in the clutch and the engine died and would not start.

We checked out the timing, ignition circuit,coil, points, the spark plugs, anti siphon selonoid and a few other things.
The fuel unit seemed to be functioning fine so we tried to start the car.

We cranked it about 5 times and then released the key back to the run position. The engine backfired through the air cleaner (lots of smoke and raw fuel in the air cleaner) and also spit some fuel out of the vent on the fuel bowl. The engine did not start.


So we stopped as we had no other ideas. Dave later talked a friend who suggested the ignition switch was the problem.

He replaced the ignition switch and that solved the problem.

A very frustrating situation but we learned a lot, I hope this information can help others resolve problems.

[William C.]

Re: 57 FI wiring question.

Typical issue, car FI car won't run. rather than looking for spark, then fuel, everyone starts with the FI and never looks at the spark side, of the timing chain side. I've seen more dead FI units due to lack of spark or empty gas tank than real FI problems on the road...

[John D.]

Re: 57 FI wiring question.

Typical issue, car FI car won't run. rather than looking for spark, then fuel, everyone starts with the FI and never looks at the spark side, of the timing chain side. I've seen more dead FI units due to lack of spark or empty gas tank than real FI problems on the road...

Ditto. I hear it all the time Bill.

[Bruce B.]

Re: 57 FI wiring question.

Bill and John,

I agree also.

The first time I started my 4360 it ran fine and was used to break in a fresh engine.
After running the car for a while and doing some minor adjusting I went back to start it and no life at all.

Aftere much head scratching, few gallons of gas in the tank solved the problem, DUH............

[Perry M.]

Re: 57 FI wiring question.

A quick stop or acceleration could crack the distributor cap or rotor if the distributor comes in contact with the firewall due to sloppy engine mounts although this should cause backfires while cranking.