Graham’s Corvette Blog and Studebaker bits ‘n’ bobs

I’m having issues with radio reception even with the plastic static shield in place. So I bought a set of new wire wound plug wires from Rock Auto. They are brand name and cost a very reasonable $53 CDN or about $39 US. Hopefully they are as good as others listed for $100 or more.

Old wires pulled and marked for location.

New wires matched to old wires. Most are longer except for #7 which is about the same. The new wires don’t have the usual ends with knobs to fit the distributor cap cover.

The right side was the most difficult. I needed to drop the starter a bit to get access to the screws holding the stainless steel plug wire cover – yellow arrow pointing to the detached bracket. Fortunately I didn’t need to detach the starter leads. Once out of the bell housing it dropped down just enough. Still a pain in the butt. For those not in the know #2 and 4 and #1 and 2 wires are routed along the side of the block behind the exhaust manifold and are protected by stainless shields – just noticeable where the red arrow is pointing.

To keep the original look I wanted to use the distributor cap cover wire holding bracket. I had to modify it to completely remove a lip on the underside so it would rest on top of the new wire connectors. Also the plastic static shield attaches to the front of the cap cover.

Cap cover in place. I started the engine and happily I didn’t mix up any wires. Now for a bit of a test drive to see if they suppress some, a bit or none of the radio static without the static shield in place.

Took a test drive and as many of you will expect, the radio didn’t work so back to the static shield.

The original silver covering on the inside was quite worn so I used a roll of aluminum duct tape to redo the covering.

It is a bear to get in place. Especially the right side as the shield has to squeeze around the trans dipstick and then behind the bracket on the back of the block that holds the plug wires. The copper bracket – arrow – grounds the metal covering on the static shield to the block.

Now for another test drive.

No real joy. Once the engine is running I can only pickup one station with a strong signal – CBC. Reading up on it all I have done everything right for the setup. But, my static control on the radio’s incoming power supply is original and may no longer be working. So I’ll replace that this winter and also add a static controller to the radio’s antenna lead.

I removed the fabricated hangers from the front cross member and took the car out for a test. The exhaust was held up only by the exhaust manifolds and the rearmost muffler hangers. I’m using band clamps on the exhaust and so the pipes are quite rigid as if they were welded together. The test was successful. Now I needed to make up some standard type hangers that are only connected to the body by re-inforced rubber.

First step was to straighten out the brackets from the hanger kit. I’ve got a piece of conveyor belting or some re-inforced rubber to choose from

I opted for the re-inforced rubber and attached lengths to the cut off clamps. I bored the clamps and used large washers on the back and self locking nuts on the front as shown.

There was no way I could fit a hanger on the front cross member so I moved to the rear crossmember and was able to install the right one on the rear and the left one on the front. They are physically holding the pipes up and the whole system is quite rigid.

While I was under the car I took the opportunity to clean off the ground strap connections and cover it all with dielectric grease. I was having problems with my low amp bypass fuse blowing – I need it to keep the radio settings. Apparently bad connections can cause this to happen. So far so good, but we’ll have to wait a bit to be sure.

Meanwhile, the wife and I took the Chevy for a nice long drive and all the nasty vibrations are gone. The harmonics are still in the exhaust only now they’re not being transmitted to the frame. I understand that a flex pipe, if installed, will help eliminate these source vibrations. That will be a job for another day. For now, this is the first time I have really enjoyed driving the Chevy since I started to restore it two and a half years back in the spring of 2023!

Next: And now for some ‘Happy Motoring’ as Murray used to say on hockey night in Canada.

When I removed the exhaust hangers at the cross member the vibrations disappeared. It may look like the exhaust pipe is near the bottom of the hole in the crossmember, but it’s just the angle of the shot. There is a 1/4″ or more of space.

Since the hanger wasn’t fully insulated from the crossmember I decided to open up the bolt holes and insert rubber grommets to isolate the bolts from the metal hanger.

I then added reinforced rubber to each side of the metal hangar.

Unfortunately this didn’t work as the bolt threads cut through the grommets.

Next I went all out and enlarged the bracket holes to accept a short length of gas line hose and also added two more rubber spacers. I needed to replace the original bolts with longer units. This done and installed it didn’t seem to make a whole lot of difference in the harmonic vibrations.

Next: I need to remove the brackets and then do an actual test drive to verify that the vibrations are indeed gone and that the hangers are the problem.

A lot of references on the web talk of harmonic vibrations caused by a faulty plug or plug wires. So I pulled all the plugs and checked them. They all look good with a light tan colour and they all fell between the recommended 4-10 ohm resistance. The wires also passed muster between 3 and a bit over 7 ohms for the longer wires. A bad condenser can cause a harmonic vibration, but this ignition doesn’t utilize a condenser only an ICM which itself supposedly can’t cause vibration problems.

One more thing to check is the torque converter. I detached it from the flywheel and held it back for this test. Still no change so I assume the torque converter is OK.

Fast running out of ideas. If anyone has a comment send it along to my email address – grhm53@gmail.com

Meanwhile I’ll just have to drive the car and maybe something will break and that will reveal the problem!

Nice new fan from Summit Racing. But sadly still no change in the harmonic vibrations. However it seems now that the vibration is more constant and only increases or diminishes at different engine speeds.

Meanwhile I decided to do a poor man’s torque converter flush. Holding the converter on it’s edge and rolling it back and forth and blowing air into the unit flushed it out. I found that I had to roll it quickly from one side to the other and lots of oil came out at the end of each roll. After getting out all I could I added about a 1/2 quart of Dextron and then flushed it out. I did that a couple of times so I’m thinking I got out most of the old oil. The towel I laid down to catch the oil was totally soaked by the time I was done.

Next: I’m just going to have to drive the car until I get a new idea to try. So far the replacements needed to be done anyway so that’s good. When they say that vibrations in a C3 can be hard to find, they were right!

Removed the AC and fan belts and found that the vibration was gone.

I connected up the AC belt and ran the engine with just the fan clutch in place – no vibration.

I noticed bend on one of the blades.

Also that blade was up at least an 1/8″ compared to the others.

Is this enough to cause the vibration. According to some references, yes. So I’ve got a replacement on order from Summit Racing.

In the meantime I’m starting the clean up of the 200 4R that will eventually go into the Chevy. Lots of crud to remove. Earl D. a local trans man who will be doing the job and he appreciates not having to clean the outside before he can start the rebuild.

Pan off and I was hoping to find a paint daub or some other marking to verify what type of trans it is – the original tag on the outside is long gone. One thing noticeably missing is the governor and cover – red arrow. Contacted the seller and he will be sending me replacements from another similar trans in his stock.

Next: the new fan should be in shortly.

Another thing I noticed while under the car was that both holding brackets for the exhaust as it passes through the cross member were touching the cross member. Leaving no stone unturned I cut a couple of bigger re-inforced rubbers for the brackets.

Well insulated now, but no joy here.

In the meantime my new spark plug shields arrived. I had to install the left and right rears from the bottom. I could just get the front shield bolts in by feel. So no more burnt plug wires now!

Also while all this testing is going on I came across a couple of TH200 4R transmissions in PEI. This one I dragged home is out of a 1984 Olds Delta 88 an comes with a later GM CG6F torque converter. It has a stall speed of 1,400 to 1,600 rpm, but it will rise with a higher HP engine. They were used in the 350 engines.

Next: back to the vibration testing.

I disconnected the flexplate from the torque converter and used bright light to check as best I could (only a narrow space between the plate and converter). Couldn’t see any sign of hairline cracks around the crank mounting bolts. I would expect to see a hair line leading outwards from the bolts if there was a problem.

This is the mounting hole for the TH350 transmission that came with the car, but they can’t be used for the TH250c

There are three mounting holes on the plate that can be used for a TH250C. My research indicated that this flex plate can be used with both types of transmissions. I bolted the converter to different holes and also pushed it up before tightening the bolts as the converter sags down when it is released from the flexplate. Not sure if that will help, but I need to correct every possibility for vibration.

Using my engine stethoscope I seemed to hear a noise in the water pump and I noticed that the alternator bracket was vibrating.

So I swapped the alternator for one I had rebuilt and was on the shelf – but no joy here.

So next was the water pump. The pump bearing was a bit rough and had s bit of sideways movement.

New water pump, but again no joy. Still the old pump was on the way out so nothing lost there.

Next: even more testing!

The repair to the harmonic dampener – a new unit for $100CDN -changed the sound and duration of the vibration, but did not remove it. So it looks like a two part problem and something else is causing vibration also.

Time to eliminate all possibilities one at a time. First some references say that a faulty dist. cap with a hair line fracture or wires inducing a charge in an adjacent wire – especially between 5 and 7 which fire after each other – can cause vibration.

So off with the cap, but no apparent cracks. There is a smear of oil on the inside and maybe that is allowing spark to jump. Best solution – replace the cap and rotor. I made sure all the wires had 1/8″-1/4″ of spacing wherever possible.

That done I pulled all the plugs to see if any cylinder was not burning clean. #5 was not all that clean and it had a cracked boot. This was a new wire set.

I’m planning on buying a set of wire wound anti-static wires so I just used some special electrical tape that bonds to itself and wrapped up the plug. #6 plug was also damaged some so I wrapped it as well. A good argument for keeping the spark plug shields in place. The originals had rusted off and I didn’t replace them. I now have a set on order!

Next: After a short test drive there was still no improvement. I did check the flex plate, but I couldn’t see any cracks around the torque converter attaching bolts. Next I’m going to pull the inspection cover, detach the torque converter and push it back into the trans and have a good look at the bolts holding the flex plate to the end of the crank.

I got the Chevy jacked up and went under to check the dampener and flex plate. Couldn’t find anything wrong with the flexplate, but happened to notice a slight misalignment between the inner and outer rings on the dampener. The outer ring appeared to have moved

forward on one side.  So I checked on line and found that the sort of misalignment is OK if it is .010 or less. Here’s what I came up with and that was measured sideways on the dampener – the real reading should be even higher!

I think the noise source has shown itself. According to an AI search result this type of problem will cause the sound I have between 1500 and 2200 rpm.

Fan and water pump pulley off and I’m going to try and replace the harmonic dampener without and taking the hood off or the rad out. We’ll how that goes. I expect to be using lighted mirrors to see what I’m doing!

The impact wrench is perfect for removing crank bolts when you can’t hold the engine from rotating.

Pulley’s off. Had to get at the bolts by feel. Not too hard and there are only three of them. Also the crank didn’t turn when I took them off.

A three arm puller in place to pull off the old dampener.

With the pulley off it was easy to see where the outer ring had moved forward by at least 1/16″

The proper balancer installation tool was a real asset in getting it on with the engine in the car. It needs a 1-1\16″ very deep socket to use a ratchet. Not being a professional I don’t have e such a socket. I had to use a long wrench that I could only move about 1/3 of a turn each time. Took a bit but the dampener finally seated itself.

It was a bit of fun getting the pulley bolts on , but at least I was able to torque them and the engine didn’t rotate. Not so with the crank bolt so I snugged it up and then used a couple of short bursts with the impact wrench to set it firmly in place. I also used lots of blue thread lock and a shake-proof washer.

All back together and I’m happy to say the vibration appears to be gone. I’ll only be totally sure after a test drive – if the rain will only stop!

Next: Hopefully I can now enjoy the final break in trips and then on into the last of the driving season 🙂