Inliners International Forums General Discussion Engines Knockin on Devils Door

Ok here it is...'64 194cuin in my Nova. It is .030 over with a big cam, 390 holley, clifford intake & headers. Started er up today and before it was warmed up to 170 degrees while revving I got a MAJOR backfire throught the carb and it stalled. I get those occasionally when cold but this was a big one. On restart I hear a knocking noise. The knock is bearly there at idle but gets more prevelant as I feed in rpm. Oil pressure is noraml and a sample from the pan shows no metal (yet). Did not want to do further damage so I pulled the plugs and valve cover and cranked it. Rockers/valves look like they are doing their job. I am on my way to buy a compression gauge. Any ideas or suggestions to try to determine if it is top or bottom end? Darn just as the cruisin weather get's here too!

Question I have for you is the Cam Gear ALum?
If so was it Heated before it was installed??

I don't know if the cam gear is aluminum or not. I bought the car from a family member who owned it for about 3 years and drove it about 300 miles per year to shows only. I have owned it for 8 months and drove it about 2500 miles since purchase with only carb tuning problems. I just completed a compression check and all cylinders are between 135-145 psi (only one cylinder #6 is 135. All others are 140-145. I put the plugs back in and restarted. At minimum (850 rpm) idle it is normal and I do not hear the knock. As I add some throttle the knock starts..my guess is a rod knocking. Any way to further confirm this?

Pull one plug wire at a time (ground the wire si it does not arc) and find the hole thats ticken.

Twisted,

Years ago, I was working on a Chevy II 4-banger. I bought a new aluminum cam drive gear and my buddy pressed it on in his press. That sucker rattled like crazy within a few hours of running it. We thought it was a lifter problem, but changing lifters made no difference what so ever. Thought it may have been a fuel pump...we put in another one...no difference. I drove the car and it ran well...ran like a watch, in fact.......it just rattled. Finally, I could stand it no longer and tore the engine back down. I could pull the cam gear off with my hands!

That time, I heated the gear, slid it onto the cam effortlessly and when it cooled, it was locked in place. Never had any more problems after that!

Dennis, Twisted & Efi,
That's where I am going tomorrow, I will inspect the timing chain and cam gear. I pulled the pushrods and checked for "true" by rolling them on a mirrow. Replaced and set the valves (hyd-lifters). Restarted and it idles and runs fine except for the noise. Efi, I even pulled one wire at a time from the distributor and no luck using that trick. Even pulled the belt just to make sure it was not the water pump, alternator or harmonic balance wheel...alls fine. I hope to have the front of the motor off sometime tomorrow. Thanks for the ideas...keep em coming if anyone has other ideas.

Duce,

Don't know if an aluminum gear ever rattled it's way completely off a cam, but it's better not to take a chance, isn't it? Better at home than in the middle of no-where! Be sure to get back to us with the results of your search for the noise, OK?

Dennis,
You are right on the money...I pushed it out of the garage today and heard the noise on start up...last week I was 90 miles from home in Coulterville, CA an old gold rush town east of me...that would have been an expensive tow if there was even a flat bed hauler available! I will let you know what I find tomorrow or Tuesday at the latest...thanks again guys for your hints and advice.

HUm You may very well want to check Your flywheel & convertor bolts. This too will give you a Unwanted rattle.knock sound. Esp If it is the flywheel/flex Plate Bolts.
And No the cam gear would not come 100% off the cam Unless it pushed itself through the cover.

The cam gear wont come all the way off but it will quit running. It happened to me. The cam slid back far enough that the lifters started to pick up two lobes. It was due to removing and installing the cam gear too many times. I got a new gear heated it put it all back together and haven't had a problem with that at all.

Remember to check on the thrust washer behind the cam gear, the one time I had a cam gear come loose my thrust washer was broken too.
I am not sure if the busted washer caused the loose gear or vice versa, anyway good luck.

Dan

Remember to check on the thrust washer behind the cam gear, the one time I had a cam gear come loose my thrust washer was broken too.
I am not sure if the busted washer caused the loose gear or vice versa, anyway good luck.

Dan

OK...pulled the timing cover and yes the gear/cam is walking . It has a very slight score on the inside cover but no damage to the gear. The car runs OK except for the noise which was the gear hitting the inside of the cover. I have a few questions:
1. Could the cam walk far enough to damage the lobes? The lifters appear to be operating normally.
2. It is an aluminum gear...how much heat should be used on re-install?
3. Any other recommendations prior to putting her back together?
Thanks in advance...Brady

I had the same problem but I did heat the gear during original assembly. I received the same advice, to heat the gear and all problems would go away. What I did to be safe was drill and tap a 3/8" UNC hole into the middle of the cam and used a short bolt with a large washer so there is no way of it can walk off. But the bolt head will contact the inside of the cover, so what I did was turn a frost plug upside down and weld it to the cover and drill a hole where the bolt contacted the cover, and everything was fine after that.

Sent you a PM

Forgot to list one more detail. With the cam gear exposed and cranking the engine, the gear moves out approx 3/16 - 1/4 of an inch at most then retracts itself then repeats the cycle when cranking around again.

Duce,

The clearance between the thrust plate and aluminum gear should only be .001" to .005". so you've got WAY too much free-play, there.

If the cam's OK, you will still have to remove it, put the new gear on, then reinstall it. Make sure your key is in good shape. I wouldn't even attempt to install a new gear with the cam in the engine, you could dislodge the plug at the rear of the cam.

I've always put the new aluminum gear in boiling water until it was hot. 5 minutes should do it. I install the thrust plate on the cam and put a .002" feeler gauge between the thrust plate and new gear and push the gear right on. If your cam's warm to the touch, putting it in the fridge for a while may help.

Thanks Dennis...Out comes the cam tomorrow. Does the gear have to be pressed in or can it be driven home with a mallet and brass spacer with a wooden block for the base at the other end of the cam? Also your thoughts on going back to a steel gear vs aluminum?

As far as I know they dont make a steel gear. You should at least find a new aluminum gear cause the center of the gear wears and lets the cam walk easier. When my cam walked back it didn't hurt the lobes or lifters and I installed a new gear with the cam in the car. My cam was drilled and tapped in the center which allowed me to use a power steering pulley installer to press the gear on after i heated it. It worked great without putting any pressure on the rear cam plug.

If the cam has walked enough Period. I would also say Change your dist gear and Look VERY Closely to the Gear drive on the Cam to the Dist. Also Check The Lobes VERY VERY close.

One other way to mechanicly fasten The gear is to use a 1/4,3/8s screw (allen set screw/ pipe plug style even) At the mating edge of the Gear & cam
No timing cover mods are needed.