what can be done about rod knock

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birdacre
Posts: 380
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

what can be done about rod knock

Post by birdacre » July 20th, 2018, 1:41 pm

i think my "noise is coming from cylinder number one. when i turn engine over i can hear a knock when turning over by hand with fan. funny i don't hear it at idle but under a load it makes a noise. should i drive it, it runs great. rod journals and caps don't have shims like the main journals on crank correct? can the rod caps be sanded down a bit? any advice appreciated. timing gear looks good, i took off side cover.

Bob C
Posts: 1181
Joined: April 24th, 2003, 11:50 am
Body Type: Mail truck, Stake tr
Model Year: 1931
Location: SO CAL

Re: what can be done about rod knock

Post by Bob C » July 20th, 2018, 3:01 pm

The rods should have shims unless the bearings are so worn that all the shims have been removed.

Bob

birdacre
Posts: 380
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: what can be done about rod knock

Post by birdacre » July 20th, 2018, 3:33 pm

thank you, the one model a engine i have taken apart had no shims. it must have been on it's last leg. thank you, kevin

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1crosscut
Posts: 737
Joined: December 25th, 2010, 7:22 pm
Body Type: 82-A
Model Year: 1929
Location: Lincoln, NE

Re: what can be done about rod knock

Post by 1crosscut » July 20th, 2018, 4:34 pm

Have you used a mechanics stethoscope or long screw driver pressed against your ear to narrow down where the sound is coming from?
Does the engine only make the noise under load and not while at idle or does the noise occur when the engine is revved while in neutral?
If you can make the noise while the truck is stationary does pulling the spark plug wire off one of the spark plugs make the noise go away?
When turning over by hand using the fan do you have the spark plugs out? Usually very difficult to turn an engine over by hand using the fan. Not healthy for a fan doing that. Better to use a hand crank.
Has this noise always been there or is it a new noise?
Rod caps start out when the engine is fresh with shim packs. Shims are removed as needed to maintain clearances. If you find all the shims missing the engine is due for a rebuild. Yes folks have sanded the caps but it is a stop gap measure and has to be done very carefully to have a "good" result.
------------
Dave

birdacre
Posts: 380
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: what can be done about rod knock

Post by birdacre » July 21st, 2018, 7:06 am

it only makes it when you give it the gas. once it levels off it is a bit quieter. sitting at an idle under not under a load it does not do it. i had the plugs in when i turned the engine back and forth. i know using the fan is ideal but i wanted to have my ear near the cylinder head. i will try the neutral on the road test. i will keep you posted. thank you, kevin

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1crosscut
Posts: 737
Joined: December 25th, 2010, 7:22 pm
Body Type: 82-A
Model Year: 1929
Location: Lincoln, NE

Re: what can be done about rod knock

Post by 1crosscut » July 22nd, 2018, 8:39 pm

Okay. Let us know what you find out. Still not clear if you can make the noise while the car is stationary. While parked and in neutral does it make the noise when engine speed is increased? If so pull one spark plug wire at a time and see if the noise can be made to stop. Doing so may narrow it down to one particular cylinder.
Since you are able to make the engine turn over with the plugs in using the fan it makes me think that your engine most likely is quite worn and probably has pretty low compression. Have you done a compression check?
------------
Dave

birdacre
Posts: 380
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: what can be done about rod knock

Post by birdacre » July 23rd, 2018, 6:29 am

it was not easy to turn over. when truck is in neutral parked, and given gas no noise, only under a load going down the road. at first i thought maybe my cam gear was missing a tooth. it looks fine, i took off side cover. the truck runs great. starts hot, never stalls. maybe a wrist pin? it does make the noise when giving it the gas, after it levels off it is quieter. maybe exhaust noise? i know an engine sure makes a bark with no muffler. it just seems to have a metallic tone to it and i just can't convince myself that it is nothing to worry about. any ideas.

birdacre
Posts: 380
Joined: October 8th, 2013, 2:37 pm
Body Type: AA express
Model Year: 1928

Re: what can be done about rod knock

Post by birdacre » July 24th, 2018, 9:46 am

i think i have narrowed down the noise to wrist pin. i put a garden hose in the cylinder to listen and turned engine over. right at TDC i hear a metallic ping ping, 2x in a row. one up one down. an old timer listened with me and said a rod knock would be dull and deep. he seemed to think drive it like it is. maybe run a straight 40 w oil non detergent. i currently use 30w non detergent. any thoughts. ideas?

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Chris Haynes
Posts: 1982
Joined: September 7th, 2003, 5:18 pm
Body Type: 82A
Model Year: 1930
Location: North Hills, CA/ Pine Grove, CA

Re: what can be done about rod knock

Post by Chris Haynes » July 24th, 2018, 10:31 am

The knock is a warning that something is about to leave its normal place and go elsewhere. This is always disastrous. Fix it.

Bob C
Posts: 1181
Joined: April 24th, 2003, 11:50 am
Body Type: Mail truck, Stake tr
Model Year: 1931
Location: SO CAL

Re: what can be done about rod knock

Post by Bob C » July 24th, 2018, 5:44 pm

I have to agree with Chris, it would be better to drop the pan now and see what is wrong rather
than look through the hole in the block to see what WAS wrong.

Bob

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1crosscut
Posts: 737
Joined: December 25th, 2010, 7:22 pm
Body Type: 82-A
Model Year: 1929
Location: Lincoln, NE

Re: what can be done about rod knock

Post by 1crosscut » July 24th, 2018, 6:31 pm

Yep pulling the pan would be something to consider.
------------
Dave

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