Timing gear noise after build?

[Daner]

Hello everyone I've been lurking around reading build threads and finding answers to a couple questions and now I have what seems to be a new one.

Truck is a 67 fleetside with a 250 and 4 speed tranny

This spring I brought the engine with me to college and had a machine shop bore the cylinders deck the head turn the crank and do all the valve work and new cam bearings.

I put it all together in my free time and by early June she was running.

My problem now is when I'm driving it. I get what sounds like gear noise in normal driving around 45mph + when the engine works harder. It also happens earlier if I work the gas too hard. My kit came with what it said was matched crank and cam gears. The cam gear is aluminum. When the truck is stopped and I move the throttle on the engine I can't replicate the sound. Seems like it needs to be under load.

Instructions with my comp cam said 30min break in. I got the same gear sound about 20 mins in. continued the break in for 5 min just under the rpm where the noise started and called it good.

I used lucas oil break in additive and also added a jug to the oil when i changed it after break in. I checked the filter and didn't see anything alarming. Engine has about 170 miles on it since break in.

My cam grind isn't radical I think its 255. I'd have to check for sure. I also added a HEI distributer from Langdons.

Also the sound only seems to happen when the engine is warmed up.

All questions and replies are welcome. Thanks

[68 TT]

Originally Posted by Daner

Hello everyone I've been lurking around reading build threads and finding answers to a couple questions and now I have what seems to be a new one.

Truck is a 67 fleetside with a 250 and 4 speed tranny

This spring I brought the engine with me to college and had a machine shop bore the cylinders deck the head turn the crank and do all the valve work and new cam bearings.

I put it all together in my free time and by early June she was running.

My problem now is when I'm driving it. I get what sounds like gear noise in normal driving around 45mph + when the engine works harder. It also happens earlier if I work the gas too hard. My kit came with what it said was matched crank and cam gears. The cam gear is aluminum. When the truck is stopped and I move the throttle on the engine I can't replicate the sound. Seems like it needs to be under load.

Instructions with my comp cam said 30min break in. I got the same gear sound about 20 mins in. continued the break in for 5 min just under the rpm where the noise started and called it good.

I used lucas oil break in additive and also added a jug to the oil when i changed it after break in. I checked the filter and didn't see anything alarming. Engine has about 170 miles on it since break in.

My cam grind isn't radical I think its 255. I'd have to check for sure. I also added a HEI distributer from Langdons.

Also the sound only seems to happen when the engine is warmed up.

All questions and replies are welcome. Thanks

Something has been damaged during the cam break in and is causing your noise.

I have seen distributor gears tear up cams before. Pull your new HEI and take a look at the teeth.

Have you changed the break in oil yet? If not then do so and check the oil for metal shavings. Also cut the oil filter apart and see what it has caught. The different metal colors will help tell you where the shavings came from.

[1971_402]

NEW 250 timing gears make noise. thats why they make a fiber cam gear replacement for that reason. GOOD LUCK

[beautimus]

you have an improperly installed cam gear. the correct way is to cool the camshaft in a freezer overnight, then heat the gear for 20 minutes in oil at 200 degrees, then slide the gear onto the camshaft untill it bottoms against the shoulder on the camshaft.
if you press the gear on, or drive it on, it will give you the gear noise and it will fail.
i went to several machine shops trying to get them to install my cam gear and nobody around here would touch it. i finally had to do it myself using that advise from an old mechanic at the local napa autoparts store.

[TheSeeker]

My stock Fiber cam gear blew apart on me going 75 on the highway, when I did the tear down to replace everything, I installed an aluminum cam gear (Cloyes). I removed the cam and left it in the bed of my other truck, and drove over to my uncles shop and heated the gear up with a torch. Slipped it on the end and it seated properly. My point is, I installed it correctly and it is a fair bit noisy for the first few miles. The factory went with a fiber gear BECAUSE it was quieter. Eventually it quieted down some as the new gears meshed to each other.

[trac209]

Im not sure exactly what's going on but I would pull it apart to be sure your not making a mess in there. It will only cost you the time and some gaskets to find out. Good luck,let us know what you find in there.
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[Daner]

Yes I changed the break in oil and peeled open the filter. I didn't find any metal.

I'll check my HEI as soon as I can get to it.

When I installed the cam gear I followed the instructions that came with it. They were heat up the gear in oil to 225 - 250 degrees and install on cam. It did need a little persuasion but it seemed to seat square. The gear on the cam was kinda what I was suspecting all along. I was talking to a buddy of mine and he mentioned the freezer trick and I thought to myself that would have been a good idea :P

So I'll check my dizzy asap and if thats fine do you think I should go 300 more miles and check my filter or not take any chances and drain and check oil and filter now?

btw I don't have a tach does anyone have an estimate of my rpms when I'm at 45 and 55 mph? Rear gears are 3.73

Thanks for the quick responses

[TheSeeker]

A Fair estimate for your RPM range can be found http://www.ringpinion.com/Calculators/Calc_RPM.aspx

Depending on your tire size it can change quite a bit.

[Daner]

Here is a pic of my HEI gear


I'm not sure if this is abnormal wear or just normal meshing.

[BurnoutNova]

Gear doesn't look that bad, If it was tearing up the cam gear it would look much worse and have metal shavings in the oil. Usually the reason cam gears have trouble is when you put a hardened roller cam in and do not use a bronze drive gear.

Are you sure it's timing chain noise? Get a stethoscope and listen around maybe it's something else.

[Daner]

Ok update.

A week or so ago I decided to change my tranny and diff fluid. I popped off the diff cover and about a cup of oil came out. Just enough to wet the bottom of the gear. I refilled it with synthetic and I still have no change in noise. Tranny whine is still there and engine gear noise is still there.

My gear noise only is heard when engine is under load and in 4th gear 1 to 1. Rpm doesn't matter. Noise goes away when pedal is to the floor but returns when I let off. It couldn't be an exhaust gasket leak?



I drained out a small amount of engine oil when I was changing things and couldn't see or feel any metal. I'm going to change my oil in a couple days then I will check the filter.


I didn't count the teeth of my diff but I spun the wheel twice and came up with 3.5 driveshaft revolutions. I didn't know chevy's could have 3.5 gears?
I installed a tach and am running 2500 rpm at 55mph sound right?


Thanks in advance

[68gmsee]

My 68 GMC has a 3.54 but it's a Dana rear axle. Not sure what Chevy used that's close to that. Also, best way to check for ferrous metal filings in oil is a magnet. If it's a bronze gear you should see the yellow flakes in the oil.

I think your suspicions are correct re. the cam shaft gear. Since you haven't found any problems other than the noise I would continue driving it to see if it diminishes some. If it doesn't I would try to get a new set from some reputable company that is U.S. made. I've seen too many outsourced parts that just don't make the grade these days.

[Daner]

Ok took longer than I thought it would to finally get the oil changed. I tore the filter apart and this is what I found.



You can see the little pieces of aluminum. That is everything I found on the inside case of the oil filter. Doesn't seem like an abnormal amount of material to me.

Here is a pic of the actual element.



I couldn't see any filings on the element.


When I replaced my carrier bearing I had the whole driveshaft out and noticed that the caps for the ujoint off the back of the tranny had little grooves where the needle bearings sit. I didn't replace it because I was anxious to drive it for the first time after the rebuild.

Could that be the source or contributor to my noise? It wasn't loose at all thats why i didn't wait to order a new U joint.