Monthly Archives: January 2018

Let’s swap the intake…and then some.

Most of this work was done in the summer/fall of 2016. I started this post a long time ago and am just now getting around to posting it. – JE


In the spring of 2016 I got a good deal on a GM ZZ4 performance intake manifold and matching chip that would fit nicely with the GM 305HO engine in my Avanti, so I figured I would swap them out. One thing led to another and in addition to the intake manifold I ended up replacing:

  • Water pump
  • Convert from fan clutch back to electric
  • New fan shroud
  • New radiator, upper and lower hoses
  • New alternator
  • New carburetor
  • New brake booster
  • New fuel pump
  • Cap, rotor, impulse coil
  • Oil Sender
  • Refinish air cleaner, replace with K&N filter
  • New Coolant overflow tank
  • Transmission cooler
  • Thermal wrap exhaust pipes
  • Thermostat and housing

Like many projects, it started out simple enough. Starting from the top, with the intake removed there was easy access to the water pump – the original cast-iron unit was rusty so I figured it was a good time to replace it with an aluminum unit. Thermostat and housing were inexpensive and easily replaced. A new coolant overflow tank and hanger from Studebaker International and upper and lower hoses finished it off.

With the water pump removed, there was easy access to the radiator, so I removed it and sent it to a radiator repair shop. They quoted what I thought was an obscene $400+ to refurbish it, so a quick trawl through the AOAI forums and I discovered what others had done instead. I ordered a nice aluminum radiator from Speedway Motors. The new, thicker, radiator meant the old clutch-style fan that the original owner had installed to replace the original “not up to the task” electric fan in 1986 no longer fit. The new radiator no longer had a transmission cooler, either.

Then it was back to Speedway for a transmission cooler, and then to Summit Racing for a modern fan controller. Finally, I got a new fan shroud and cooling fan from to tie it all together.

In the course of replacing the water pump  I was right next to the alternator, which originally output 94 amps. I’d previously had good luck with the Powermaster brand so I went with a 140amp unit from them.

With all that out of the way, I figured I might as well replace the fuel pump, as i was confident it was original, as well.

The brakes had always been funny in the Avanti. When I first got it, the passenger side rear would lock up in anything remotely resembling a panic stop situation. I replaced the wheel cylinders, even though ones on the car looked like they had recently been replaced. Perhaps the previous owner had the same thought? Made no difference, though while I was in there I replaced the nasty looking brake master cylinder and flushed the fluid.

Shortly after this I was looking around underneath it again and I discovered that the metal brake line on the driver’s side rear axle was crushed. I presume someone put a tow hook around the axle at some point and crushed the brake line. Once that was replaced braking was better but still not great.

Spoke with Jon Myers at the AOAI/SDC meet and he suggested a rebuilt brake booster. A local club member had mentioned something similar so I sent it off to Jon in Ohio. A few weeks later it was returned and re-installed. Now I think it’s probably as good as it’s going to get with the original front discs and rear drums.

The original oil pressure sender was toast, and the current replacements required a 90 degree elbow fitting to clear the air cleaner/ignition distributor.

On the subject of the ignition distributor I also replaced the impulse oil, cap and rotor. Interestingly, the three wire connector on the ignition control module (ICM) can be fitted right side up or right side down. Some time chasing this one revealed I had reinstalled it incorrectly, which manifested itself in a strange running condition. The Chevrolet shop manual for the 84 Camaro came in extremely handy when diagnosing this issue.

Over the last year or so of running the car with all this work done, it would periodically quit and refuse to restart until the ICM was replaced. I had used a judicious amount of dielectric goop to insulate it, but it was still eating ICM’s like candy bars. I mentioned this to a co-worker and he encourage me to closely look at the grounds on the distributor. Sure enough, I had powder coated the hold down. With the powder coat removed, so far this seems to have cured the problem.