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Old 10-18-2013, 09:05 PM
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sbc 350 rod knock

Hi guys, my little brother has a 1981 caprice with a 305 in it. it has a knock and i was wonder if there is anyway i could fix this.

by locating the bad piston rod and bearing and replacing the bearing. if the crank isn't to bad.

and if the crank is bad could machining fix it to where i could use a thicker bearing on it.

also if the crank is bad can i remove it from the car with out pullin the engine i no i have to lift it to take out the oil pan.

any help greatly appreciated if its possible ill start on in asap.

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Old 10-18-2013, 09:08 PM
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he just paid 850 for his rebuilt 700r4 transmission. and now the engine is knocking dew to all his oil squirting out of a front screw hole(see pix). and he didn't now until it started knocking and he drove it the rest of the way home with his transmission slipping. when i checked it out there was no knock, but after installing the transmission and changing the oil the knock was present.
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Old 10-18-2013, 09:57 PM
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Originally Posted by frost2000 View Post
he just paid 850 for his rebuilt 700r4 transmission. and now the engine is knocking dew to all his oil squirting out of a front screw hole(see pix). and he didn't now until it started knocking and he drove it the rest of the way home with his transmission slipping. when i checked it out there was no knock, but after installing the transmission and changing the oil the knock was present.
He shouldn't have lost all the oil through the hole- which should be plugged, as you found out the hard way. But in any event, there's just no practical way to dio the crank R&R w/o pulling the engine. It CAN be done, but I'd rather take a shot to the 'nads AND a sharp stick to the eye than to attempt it and I would never recommend anyone do it unless they were stranded somewhere in really dire straits.

Get yourself a place to work on it, rent or borrow an engine hoist and an engine stand and do it right. You'll be time and money ahead in the long run. Another option you might look into is to buy another running engine and just **** can the knocker. 305s are a very common engine to buy used in good shape.
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Old 10-18-2013, 10:06 PM
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yea i might just end up telling him to buy another engine he wants a 350 anyway lol. and yea on the oil loss. it sprayed everywhere. i was thinkin the higher rpm made it really squirt out do to the slipping transmission.

his car is in my drive way and i have a 81 malibu that's getting body work, so i can't put it in my garage. ill probably end up renting the hoist and stand, and swapping it with a 350 later though. thanks again.
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Old 10-19-2013, 03:59 AM
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Before you pull that 305, check out a few other potential causes of the knock.
He might be lucky; the knocking might be related to the trans swap.
Check the torque converter bolts and the flexplate.
A loose torque converter, loose bellhousing bolt or cracked flexplate could be creating the knock.
Also look for any hard contact with the exhaust system.
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Old 10-19-2013, 06:30 AM
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engine

i am in agreement with above.. try looking into "craigslist" in your area for a 350 motor.. make sure u can hear it run. if it really turns out to be an engine knock this swap will be the easies and cheapest way.
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Old 10-19-2013, 12:25 PM
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ok thanks for all the info i will run more test, also it seems to idle really high i tried to lower it but got no response. it did kick down on its own then i gave it a slight rev and it kept idling high again.

i did end up finding a sbc 350 stock engine a friend has for 300bucks out of a el camino. he was pretty happy about that. he wont be able to get it untill the 31st.

i just checked the torque converter bolts all was good didn't see any cracks on the flywheel. bell housing bolts also were good. exhaust looks good aswell. i think im just going to get it prepped for pulling and star lookin for a stand and hoist thanks again. ill post pictures of the engine when i pull it and find out what was wrong with it.
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Old 10-19-2013, 12:40 PM
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Quote:
Originally Posted by frost2000 View Post
ok thanks for all the info i will run more test, also it seems to idle really high i tried to lower it but got no response. it did kick down on its own then i gave it a slight rev and it kept idling high again.

i did end up finding a sbc 350 stock engine a friend has for 300bucks out of a el camino. he was pretty happy about that. he wont be able to get it untill the 31st.

i just checked the torque converter bolts all was good didn't see any cracks on the flywheel. bell housing bolts also were good. exhaust looks good aswell. i think im just going to get it prepped for pulling and star lookin for a stand and hoist thanks again. ill post pictures of the engine when i pull it and find out what was wrong with it.
Make sure you check your casting numbers on the el Camino 350, if its a g-body el-camino then its unlikely a 350 unless its been swapped, around here everyone with a g-body elcamino or Monte Carlo claims its a 350.
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Old 10-19-2013, 01:15 PM
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Quote:
Originally Posted by frost2000 View Post
he just paid 850 for his rebuilt 700r4 transmission. and now the engine is knocking dew to all his oil squirting out of a front screw hole(see pix). and he didn't now until it started knocking and he drove it the rest of the way home with his transmission slipping. when i checked it out there was no knock, but after installing the transmission and changing the oil the knock was present.
The hole your arrow points to is there for installing a longer bolt than the OEM uses to plug this hole. The purpose of the hole is to allow a longer bolt to be installed to clamp the fuel pump push rod to prevent it from falling out of the engine when the fuel pump is beingremoved and or replaced. That hole is normally closed from the factory with a short body bolt with thread sealer. These typically do not come out without someone wrenching them out. The fact that this is missing following transmission service would indicate someone was in there there that didn't know what they were doing, or removed the fuel pump and didn't return the sealed short shank bolt after servicing the pump for replacement or the transmisison guy needed the pump out for tranny coolant line access. At any rate this is a case of somebody screwing up.

Bogie
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Old 10-19-2013, 02:32 PM
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i am currently uploading a video of the engine running. i guess when it worms up the noise basically goes away at idle some times it comes slightly. but when revved it's loud again. should i keep lookin into this, or is it definitely the rod thanks. i watched a vid also on youtube where it was the flywheel cracked im thinking that's what it is. i asked my brother did he touch the flywheel and he said he had a rode on it for leverage to push the transmission back so maybe he cracked it. ill post my vid first then the other after mine thanks. and it does sound like the noise is coming from back there.

and when it was idling higher the knock was louder

http://www.youtube.com/watch?v=1yguA...ature=youtu.be
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Old 10-19-2013, 02:33 PM
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here is the other vid with a confirmed cracked flywheel

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Old 10-19-2013, 03:10 PM
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the flywheel fills pretty stiff.
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Old 10-19-2013, 05:50 PM
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Quote:
Originally Posted by frost2000 View Post
i am currently uploading a video of the engine running. i guess when it worms up the noise basically goes away at idle some times it comes slightly. but when revved it's loud again. should i keep lookin into this, or is it definitely the rod thanks. i watched a vid also on youtube where it was the flywheel cracked im thinking that's what it is. i asked my brother did he touch the flywheel and he said he had a rode on it for leverage to push the transmission back so maybe he cracked it. ill post my vid first then the other after mine thanks. and it does sound like the noise is coming from back there.

and when it was idling higher the knock was louder

1981 caprice 305 knock - YouTube
Hard to tell there's so many noises, there is a heavy background knock and lighter forground that is louder but tinnier. When you advanced and held the trottle in the earlier part there was a heavy knock that stayed up with the steady RPM, more of that steady throttle position would be useful.

Getting to heavy knocks the bad guys can be wrist pins, rod bearings, piston skirt, these group in a double knock to the RPMs sounding quite similar. A general test is to run the engine at a steady RPM where the knock is loudest then short out each cylinder's spark plug in turn one at a time, the offending cylinder will quiet down with the firing load taken off it. Mains have a heavy knock with each revolution, they get quieter with load (acceleration) and louder when the throttle is backed off and the vehicle pushes the crankshaft.

The torque converter area is quite loud and sheetmetal sounding, the era of this vehicle does have a problem with cracking the flexplate in the area where it attaches to either the converter or the crank. This usually cannot be felt by prying on the flexplate, it takes disassembly and visual inspection.

Bogie
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Old 10-19-2013, 08:14 PM
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ok thanks for all the info. i will make another video tomorrow i made one with my phone but it was really blurry so i didn't upload it.

after i make the vid ill do the spark plug test. and later take down the flex plate.
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Old 10-20-2013, 11:44 AM
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ok did the spark plug test and cylinder number 8 was the one that made the knocking go away when the plug wire was pulled.
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