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WildBill79 · 09:25 AM

1972 350 with #17 heads and summit 2801 cam

At idle the motor sounds great. If I bring this rpms up to 1500 I can hear a banging noise in the bottom end of the motor. The car seems to drive fine but under load the engine sounds like it wants to come apart. The oil was filled with glitter.

I plan on having the motor on a stand by the end of the week. What should I look for when I tear it down? My hope would be that I could just replace some bearings and get back on the road. If I need to have any machining done it may make more sense to look for a 400 or 455 block and start there instead.

I should add that this motor was rebuilt about 5 years ago and has less than 50 miles on it

Rob B · 11-10-2014, 09:31 AM

Sounds like a typical rod bearing. Once one is spun, the crank will need to be ground as well as the rod replaced or resized. What does/did you oil pressure show??

WildBill79 · 11-10-2014, 09:44 AM

Oil pressure was usually 20-60 depending on rpm and temperature from what I can remember

Ed Fitzgerald · 11-10-2014, 10:08 AM

With the engine running start pulling plug wires one at a time and replace.Listen to see when the noise goes away (with plug wire off) and that will be your bad rod bearing. Ed

Rob B · 11-10-2014, 10:29 AM

I've had them before idle fine, no noise, and with a little rpm that puts a load the rod, bearing, and journal, that's when you'll hear the noise. The damage is already done.

TedRamAirII · 11-10-2014, 11:41 AM

I vote rod bearing too. If the oil was clean, I would have had you check Torque Converter bolts. But its a rod issue. Too Bad, Turkey Rod run is almost here, hurry up! Like another poster said, pull spark plug wire off and pin down which one it is, then you wont waste time pulling bearings to check the damage. Good Luck. ; )

Rob B · 11-10-2014, 12:02 PM

Quote:

Originally Posted by TedRamAirII

I vote rod bearing too. If the oil was clean, I would have had you check Torque Converter bolts. But its a rod issue. Too Bad, Turkey Rod run is almost here, hurry up! Like another poster said, pull spark plug wire off and pin down which one it is, then you wont waste time pulling bearings to check the damage. Good Luck. ; )

You'd honestly waste more time checking to see which rod/journal is spun by pulling plug wires. When you pull the pan, that pair of rods (because it will be 2 not one) will more than likely be burnt or blue from the heat. all you would have to do it just grab a rod on each journal to find the bad one. It will be obviously sloppy and loose.

WildBill79 · 11-10-2014, 01:10 PM

Quote:

Originally Posted by TedRamAirII

I vote rod bearing too. If the oil was clean, I would have had you check Torque Converter bolts. But its a rod issue. Too Bad, Turkey Rod run is almost here, hurry up! Like another poster said, pull spark plug wire off and pin down which one it is, then you wont waste time pulling bearings to check the damage. Good Luck. ; )

I'll still be at the Turkey Run in my other Ventura.

Its too late to do the spark plug test. The motor is completely disconnected and ready to be pulled out, but because of work I cannot get it pulled and put on a stand until friday.

What are the chances of just putting some new rod bearings in without resizing/machining?

TedRamAirII · 11-10-2014, 01:20 PM

Maybe If you caught it early enough, you need to measure the crank journal for size and it if its round.. Then there is a question of WHY it happened. I hope to be a Daytona at least on Friday.

Rob B · 11-10-2014, 02:11 PM

Quote:

Originally Posted by WildBill79

I'll still be at the Turkey Run in my other Ventura.

Its too late to do the spark plug test. The motor is completely disconnected and ready to be pulled out, but because of work I cannot get it pulled and put on a stand until friday.

What are the chances of just putting some new rod bearings in without resizing/machining?

Zero. Something was not right to cause it to happen in the first place.

Squidward · 11-10-2014, 02:22 PM

Quote:

Originally Posted by WildBill79

I'll still be at the Turkey Run in my other Ventura.

Its too late to do the spark plug test. The motor is completely disconnected and ready to be pulled out, but because of work I cannot get it pulled and put on a stand until friday.

What are the chances of just putting some new rod bearings in without resizing/machining?

I've been through this. By the time you hear it to get a firm diagnosis it is already too late to just stuff in a new bearing. In fact, I recently got a crank turned 10 under after chasing a noise that was most likely an exhaust leak, but found the bearings to be bad too. My last rod bearing issue before that HAD a pair of replacement bearings in it from the previous owner(s), so I can tell you that doesn't make for a long term solution.

I've known of other issues to cause noises, tho. Bad lifter, exhaust leak, loose flexplate/converter bolt, loose balancer - I've had all of these.

Squidward · 11-10-2014, 02:23 PM

BTW, how does that 350 run with the 2801? Thought of trying that combo myself, but didn't know if it would make the low end too soggy.

WildBill79 · 11-10-2014, 02:41 PM

Quote:

Originally Posted by Squidward

BTW, how does that 350 run with the 2801? Thought of trying that combo myself, but didn't know if it would make the low end too soggy.

I wish I could tell you. I haven't been able to put enough miles on it to find out and it looks like it will be a while before I get it running again.

Sirrotica · 11-10-2014, 05:07 PM

Agree, if it was loose enough to knock the crank is no longer round, replacing a bearing will not remedy anything except waste a bunch of time and money, been there done it and ended up pulling the engine.

I also thought I caught it soon enough, mine was due to a stuck needle and seat in the carb dumping a bunch of gas into the crankcase. To keep it running I was revving it up and that did in the bearing. I never even moved the vehicle, happened on a restart from shutdown.

WildBill79 · 11-15-2014, 03:56 PM

I got the engine out and on the stand. So far it looks like all the bearings are bad. Every one I've checked so far i could see copper and they felt grooved. #7 and #8 rod bearings seemed the worse. The camshaft actually seems good. What else should I inspect while it is apart? I was thinking of just putting a crankshaft kit in it and putting it back together.

TedRamAirII · 11-15-2014, 06:00 PM

Need to find out why. See your engine builder. You dont want to put in a crank just to do it again. I would verify oiling passages, oil pump, by pass, etc.

Sirrotica · 11-15-2014, 06:04 PM

If you don't flush out all of the trash in the block before putting a new crank and bearings, you'll likely be doing it again in a short period of time.

So engine disassembly will have you wondering about grinding valves, replacing gaskets, and the condition of the rings, lifters, and then your gonna have rods to replace because of spun bearings so you might as well get a set of new rods because reconditioning old rods makes no economic sense. And your going to have to pull the pistons out to replace rods, while your there would it make sense to get pistons too? Of course a new oil pump while your in there. See where I'm going with this? Rebuilding a 350,400,or a 455 is just about the same money. Restoring an engine is like restoring a car, once you start taking parts off it snowballs................

Your money, car, and your choice to make.

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