Thread: something loose?

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Damn.
Yes, that's the right way to start a thread in this case. I built a mild 350 a year ago (about 300 HP, in a G20 van), drove it for 5000 miles and a couple of days ago, suddenly, there's a wierd sort of clanking noise coming from inside the engine. I'm almost certain: something's loose What could that be? What would it sound like if a rod-cap had come loose, but not off completely? Since I noticed it for the first time I might have don 5 miles or so, it's getting worse. It sounds like a sort of loud mechanical rattle, which is pretty consistent with engine speed. Sounds horrible. No, it's not the fan, TC bolts or engine mounts. That's what I checked first of course...
Yes, I do like to step on it and spin tyres and the sort. And yes, it is a 2.5 ton truck and yes I do do 90 mph on the highway and yes, I am running stock rods, caps, and bolts

Any help or ideas to what the rattling could be woudl be really appreciated!

Madmax


For info:
350 bored +.060, 4 bolt 010 block
sealed power flat top pistons
491 heads (64cc)
roller comp cam kit for high torque
stock crank (.010 under)
stock rods
600 Edelbrock carb
performer intake
until now troublefree, excellent performance, all spark plugs clean and dry, ignition in good order (the sound's NOT a ping)

Well if you checked all those other parts for mechanical noise and they are fine. Check your oil !, if it is glittery and feels like it has metal in it, then it's time to pull the sump off and take a look. I have a feeling it will be a loose rod for sure ........... Damn and blast !!!!! But at least you can save the block heads and cam and pistons. It will be crank pull out time again, so you will then have to decide weither to regrind the old crank on the big ends or to put in one of the after market new crank and rod sets. I you are going to put the boot into it regularly the after market parts would be the way to go, they have a good safety margin. If done right.

Just thought about this: you may be real lucky and it could be a broken valve sping.

I feared as much...
But I also checked the valve springs, they're fine (brand new comp cams springs, should last a million miles or so). But I guess I'll have to shop around for aftermarket parts then, not easy to get them here in Germany
Crank was 010 under already, so I guess it's time to say goodbye...
Dammit.
But thanks nonetheless,
Max

Wonder if your flex plate cracked.........

Have you taken the belts off to rule out water pump, alternator etc?

My thought was a cracked flexplate. Some times you can't see the crack untill its out on the bench. Keep us posted

Hmm, I've though of a loose one, but not an actually cracked one... I'll check that out tomorrow. I did check the flexplate thoroughly before I reinstalled it a year ago, seemd perfectly fine, wasn't old at all yet, but one never knows...
I'll keep you posted,
Max

I'll also check the waterpump, haven't done that yet. Anything before I pull out that engine again, that's a real pain in the ***

well I dont know what the procedure is for shipping parts to that neck of the woods your in but I can get you some good after market parts if you need them. iIm quiet sure there are alot of guys here in C.H.R. that would be willing to help. I ship alot of stuff to Austrailia, so Im sure its not to different to send you some stout bowtie parts.

A cracked flex plate is about the only thing that sounds like the hammers of Hell without going Boom in a hurry. It's hard to see the crack without disconnecting the converter and sliding it back a ways. With the right wrench, you can change one without pulling the transmission. Loosen the bell bolts and pry the trans back a bit for more room. Maybe get a kid with small hands to help!

Hi,
I have had stuff shipped to me, but the heavier it is the more expensive it gets (and it gets more expensive FAST). A crank would cost me about as much in shipping as the crank itself costs
But nonetheless thanks a lot for the offer, I might come back on that some time, but right now I'm still figuring out what parts I need at all (still hoping against hope that I won't need too many...)
Any other ideas what parts of an engine can rattle?

THX, Max

Originally Posted by R Pope

A cracked flex plate is about the only thing that sounds like the hammers of Hell without going Boom in a hurry. It's hard to see the crack without disconnecting the converter and sliding it back a ways. With the right wrench, you can change one without pulling the transmission. Loosen the bell bolts and pry the trans back a bit for more room. Maybe get a kid with small hands to help!

I have done this myself and it saves a lot of lifting and lineing back up. Remove the dr shaft remove the trans to crossmember bolt (s). Put a jack under the trans pan with a block of wood or somthing so you don't dent the pan. Remove inspection cover,remove the 3 flexplate to converter bolts, remove all trans to engine bolts in the second bolt holes up place a 3/8"x 4" bolt you don't have to tighten it all the way but better if you do. Remove the linkage speedometer cable and you should be able to PRY/ SLIDE the trans back far enough R & R the flex plate. then just slide the trans back on the long bolts replace the others and finish up. It is easier than pulling the trans when working on the ground.

Well, I unbolted the TC, pushed it back and got happy: One of the flexplate bolts was loose. So I thought: Good thing, saved a lot of time and money. So I tightend it back down, started the engine and got sad: Nothing changed, the clanging is still there. The flexplate also doesn't seem to be bent or cracked, I inspeced it very carefully, as carefully as I could with it installed and with the aid of a good handlamp. Anyway, two things: The noise doesn't sound the same as if a bang on the flexplate with a small hammer, it doesn't ring like the fp, it's more of a clacking sound... Second: Only one bolt of 6 was loose, I don't think that would make a noise that loud...
I have also checked for loose headers (that's not the case) and waterpump is going to be checked soon. But I fear it's something "internal"
What rotating assy would you suggest? Go with GM parts or more like Scat or Eagle? Would I need a steel crank or would iron do the job? remember: heavy car, fun-style of driving.
Many thanks to all of you,
Max

I would remove the three torque converter bolts and then start it up.

Other than that? Maybe your cam bolts are loose, but I doubt they would make the noise you describe. Good luck.

Done that, I removed the converter and fired it up without the converter after having tightened the flexplate to the engine (one bolt had come loose there). Someone said that maybe the converter had come apart inside, but the sound is the same even without the converter. How much I wish my flexplate was broken!!

Originally Posted by MadMax

Go with GM parts or more like Scat or Eagle? Would I need a steel crank or would iron do the job? remember: heavy car, fun-style of driving.
Many thanks to all of you,
Max

I would go with the eagle cast steel crank, I have had plenty of experience with those, they are nicely prepped. But on thinking about it if your freight charges are sky high it will cost the same for a forged crank as for a cast steel crank freight wise. Another thing to think about is, to think abot the 383 kit, cost a little more but should be the same in freight. With the 383 kit I would go the whole hog, pistons, rings, bearings, rods. Just make sure that you get the internally balanced kit, so you can reuse your balancer and flexplate. Oh and the assembly has to be balanced, so make sure you have an engine balancer handy. Good luck with it

Well, undo the motor mounts and lift the engine 3-4 inches and pull the pan. If you have a broken rod bolt or one that loosened, and if you caught it in time, maybe you can do a patch up job. Just replace that one bearing if it mics out close to .002-.003. It could well be that you forgot to torque one rod bolt. Usually the bearing will take the pounding before the crank journal. If it is a main bearing, then you will have to redo the entire engine.
Something else to remember, you can get oversized bearing .0011.