Engine knock - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dubie · 06-29-2004, 11:20 PM

what kinda things would cause my engine to knock? it sounds almost like an exhaust leak but I just got the truck back from the exhaust shop, and it's all new exhaust, so I know it's not that. I had the valve covers off and adjusted the valves while it was running and it sounded like it was coming from in there. would over tightened valves make it knock?

70ChevyLongbed · 06-29-2004, 11:41 PM

You prolly know by now I'm no engine expert, but when we put my motor back together my mechanic friend adjusted the valves because my brother-in-law over tightened them. So yes they can be too tight, and they do cause a noise.

I hope someone else will give a more detailed answer soon.

jlmtrout · 06-29-2004, 11:46 PM

Could be carbon buildup on the valves/combustion chamber. Good luck and keep on truckin'......Jerry

72C203503ONTHETREE · 06-29-2004, 11:54 PM

If you have the valves too tight you may be causing the valves to bind and mnaking a noise. Was the noise there before you put exhaust on it? If not, I doubt it was anything else but a leak. I had dual exhaust put on a truck at a muffler shop and it leaked bad so I had to take it back. Usually noisy valves are from them being set too loose. You shouldnt adjust valves while the engine is running, set the number 1 cylinder to TDC and adjust the valves on number one. Just tighten the valves until the pushrod has no slack and turn the nut a half turn more. Turn the engine 90 degrees and check the next cylinder and so on. It may also be a bent pushrod or perhaps a broken or cracked rocker arm.

dubie · 06-30-2004, 12:09 AM

i couldn't tell if it was there before because the engine was so damn noisy. I'll have to adjust them again tomorrow. maybe they're to tight

*1972C10* · 06-30-2004, 02:50 AM

Isnt this a new engine?

dubie · 06-30-2004, 07:47 AM

it's a rebuilt 350

68C15 · 06-30-2004, 08:41 AM

a loose adjustment could sound like a ping. take an old set of covers & cut out center rectangle so you can adj. without leaking oil all over
loosen nuts one at a time untli you hear a rattle them tighten slowly until clatter goes away. them go additional 1/2 to 1 turn. I also highly recommend using the posi-lock nuts. (like you would use for roller rockers) they DO NOT loosen like the originals do. set it & forget it

if they are too tight you would notice a light missfire or running rough.

dubie · 06-30-2004, 05:17 PM

I had the valve covers off and adjusted the valves and there is now no clattering coming out of there, but the knock is still there. It's a constant ticking noise at all rpms. I am starting to get a weee bit worried here now

**BOSS** · 06-30-2004, 05:43 PM

Tim it doesnt sound good,can you tell if it is comeing from the lower or upper part of the engine?

dubie · 06-30-2004, 06:01 PM

the noise is coming from the rear of the engine. I layed underneath the truck while it was in nuetral and running and the noise sounds like it's coming from the rear of the engine where the engine and tranny meet

stllookn · 06-30-2004, 06:22 PM

I had a cracked bell housing that drove me nuts until it finally broke all the way. It was a loud knock that I could trace to the rear of the engine with a stethascope.

**BOSS** · 06-30-2004, 07:13 PM

could be a cracked flywheel also,I have had some do that

jcueckert13 · 06-30-2004, 07:37 PM

is this the motor that was leaking anti freeze under the intake? it could be that a lifter is sticking.

jostrans68 · 06-30-2004, 07:48 PM

check flexplate to converter bolts, if tight remove them and pry a little back and forth on flex plate if its cracked you will hear it Good Luck Jack

crazy longhorn · 06-30-2004, 08:54 PM

Dubie, you have a stick in that truck ....right? does the noise stop with the clutch down, or more noticable with the clutch up/down?

68C15 · 06-30-2004, 10:00 PM

sounds like a good lead crazy longhorn. I forgot about him having a clutch. if it goes away with slight pressure on pedal (throw-out brg. just touching pressure plate) it could be that brg. if it stops with pedal all the way down it could be in the clutch itself or input of trans. I have seen more than my share of clutch disc damping springs loose & causing that kind of noise. generally the TO brg makes a constant squeal noise when against pressure plate. how much pedal free-play do you have?

dubie · 06-30-2004, 10:27 PM

i got it all figured out and you'll never guess what was causing it. the small plate that your starter bolts thru was rubbing against the back end of the crank causing a tick tick tick. I bent it back with a screw driver and it's sounding sweet now

Russell · 06-30-2004, 10:41 PM

Glad you got it figured out, and that it was something so harmless!

dubie · 06-30-2004, 10:49 PM

I gotta give all the credit to TODDS_72, he's the one that suggested it to me, so many thanks go out to my little buddy for all his help. I owe your a beer in INDY Todd!!

ChevLoRay · 07-01-2004, 07:10 AM

Ain't this a wunnerfull web site????

Also, don't our minds go nuts when we hear a little noise and we can't figger it out? Yet, this one had a simple solution and the suggestion came from another board member. Now, THAT'S what I say makes this a wonderful website!!

06-29-2004, 11:20 PM	#1
dubie Registered User Join Date: May 2000 Location: Flin Flon, Manitoba, Canada Posts: 8,853	Engine knock what kinda things would cause my engine to knock? it sounds almost like an exhaust leak but I just got the truck back from the exhaust shop, and it's all new exhaust, so I know it's not that. I had the valve covers off and adjusted the valves while it was running and it sounded like it was coming from in there. would over tightened valves make it knock? __________________ My name's Tim and I'm a truckaholic My 56 Chevy shop truck build http://67-72chevytrucks.com/vboard/s...d.php?t=562795

06-29-2004, 11:41 PM	#2
70ChevyLongbed Howzit?!? Join Date: Jan 2003 Location: Maryville, TN Posts: 1,265	You prolly know by now I'm no engine expert, but when we put my motor back together my mechanic friend adjusted the valves because my brother-in-law over tightened them. So yes they can be too tight, and they do cause a noise. I hope someone else will give a more detailed answer soon. __________________ Jason Hawaiian-J 70 Longbed, 307, Edelbrock Carb 1404, Edelbrock Intake 2101, Dual Roller Timing chain and gears, 214/214 cam, Comp Roller Rockers, dual Flowmasters. 1999 Chevy Tahoe 2004 Mini Cooper S 71 BMW 2002 - Sold

06-29-2004, 11:46 PM	#3
jlmtrout Registered User Join Date: Jul 2002 Location: Memphis, Tn Posts: 194	Could be carbon buildup on the valves/combustion chamber. Good luck and keep on truckin'......Jerry __________________ '68 c-10 long wheelbase fleetside, been in family since new, originally 250 3 speed Now (389) 350 .060 over 3.75 stroke,Edelbrock Performer RPM 70cc heads and Intake 600 cfm Edelbrock,Small Comp Cams retro-roller cam and roller rockers,9:1 cr, headers, HEI,Old Air a/c, 72 power disc brakes w/stainless lines, 3.42 gear,T-56 6-speed, original paint(what's left of it). Dakota Digital Dash

06-29-2004, 11:54 PM	#4
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	If you have the valves too tight you may be causing the valves to bind and mnaking a noise. Was the noise there before you put exhaust on it? If not, I doubt it was anything else but a leak. I had dual exhaust put on a truck at a muffler shop and it leaked bad so I had to take it back. Usually noisy valves are from them being set too loose. You shouldnt adjust valves while the engine is running, set the number 1 cylinder to TDC and adjust the valves on number one. Just tighten the valves until the pushrod has no slack and turn the nut a half turn more. Turn the engine 90 degrees and check the next cylinder and so on. It may also be a bent pushrod or perhaps a broken or cracked rocker arm. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

06-30-2004, 12:09 AM	#5
dubie Registered User Join Date: May 2000 Location: Flin Flon, Manitoba, Canada Posts: 8,853	i couldn't tell if it was there before because the engine was so damn noisy. I'll have to adjust them again tomorrow. maybe they're to tight __________________ My name's Tim and I'm a truckaholic My 56 Chevy shop truck build http://67-72chevytrucks.com/vboard/s...d.php?t=562795

06-30-2004, 02:50 AM	#6
1972C10 Account Suspended Join Date: Dec 2003 Location: Texas Posts: 2,686	Isnt this a new engine?

06-30-2004, 07:47 AM	#7
dubie Registered User Join Date: May 2000 Location: Flin Flon, Manitoba, Canada Posts: 8,853	it's a rebuilt 350 __________________ My name's Tim and I'm a truckaholic My 56 Chevy shop truck build http://67-72chevytrucks.com/vboard/s...d.php?t=562795

06-30-2004, 08:41 AM	#8
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	a loose adjustment could sound like a ping. take an old set of covers & cut out center rectangle so you can adj. without leaking oil all over loosen nuts one at a time untli you hear a rattle them tighten slowly until clatter goes away. them go additional 1/2 to 1 turn. I also highly recommend using the posi-lock nuts. (like you would use for roller rockers) they DO NOT loosen like the originals do. set it & forget it if they are too tight you would notice a light missfire or running rough. __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

06-30-2004, 05:17 PM	#9
dubie Registered User Join Date: May 2000 Location: Flin Flon, Manitoba, Canada Posts: 8,853	I had the valve covers off and adjusted the valves and there is now no clattering coming out of there, but the knock is still there. It's a constant ticking noise at all rpms. I am starting to get a weee bit worried here now __________________ My name's Tim and I'm a truckaholic My 56 Chevy shop truck build http://67-72chevytrucks.com/vboard/s...d.php?t=562795

06-30-2004, 05:43 PM	#10
BOSS Just here to help Join Date: Jan 2002 Location: Norwood,Mo Posts: 3,890	Tim it doesnt sound good,can you tell if it is comeing from the lower or upper part of the engine? __________________ Support our site Norwood Survivor

06-30-2004, 06:01 PM	#11
dubie Registered User Join Date: May 2000 Location: Flin Flon, Manitoba, Canada Posts: 8,853	the noise is coming from the rear of the engine. I layed underneath the truck while it was in nuetral and running and the noise sounds like it's coming from the rear of the engine where the engine and tranny meet __________________ My name's Tim and I'm a truckaholic My 56 Chevy shop truck build http://67-72chevytrucks.com/vboard/s...d.php?t=562795

06-30-2004, 06:22 PM	#12
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	I had a cracked bell housing that drove me nuts until it finally broke all the way. It was a loud knock that I could trace to the rear of the engine with a stethascope. __________________ '68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary)

06-30-2004, 07:13 PM	#13
BOSS Just here to help Join Date: Jan 2002 Location: Norwood,Mo Posts: 3,890	could be a cracked flywheel also,I have had some do that __________________ Support our site Norwood Survivor

06-30-2004, 07:37 PM	#14
jcueckert13 Registered User Join Date: Apr 2003 Location: Edgewood New Mexico Posts: 2,088	is this the motor that was leaking anti freeze under the intake? it could be that a lifter is sticking. __________________ 1990 subaru legcy (daily driver) 1987 Toyota 4runner (weekend toy) 1968 C30 flatbed dually 1970 C10 longbed stepside (in pieces) 1976 Dodge Dart 1963 Dodge Dart

06-30-2004, 07:48 PM	#15
jostrans68 Jostrans68 Join Date: Mar 2001 Location: Bloomington indiana Posts: 1,182	check flexplate to converter bolts, if tight remove them and pry a little back and forth on flex plate if its cracked you will hear it Good Luck Jack __________________ [CGTW Member former 67-72 now with a 96 silverado



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06-30-2004, 08:54 PM	#16
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Dubie, you have a stick in that truck ....right? does the noise stop with the clutch down, or more noticable with the clutch up/down? __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

06-30-2004, 10:00 PM	#17
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	sounds like a good lead crazy longhorn. I forgot about him having a clutch. if it goes away with slight pressure on pedal (throw-out brg. just touching pressure plate) it could be that brg. if it stops with pedal all the way down it could be in the clutch itself or input of trans. I have seen more than my share of clutch disc damping springs loose & causing that kind of noise. generally the TO brg makes a constant squeal noise when against pressure plate. how much pedal free-play do you have? __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

06-30-2004, 10:27 PM	#18
dubie Registered User Join Date: May 2000 Location: Flin Flon, Manitoba, Canada Posts: 8,853	i got it all figured out and you'll never guess what was causing it. the small plate that your starter bolts thru was rubbing against the back end of the crank causing a tick tick tick. I bent it back with a screw driver and it's sounding sweet now __________________ My name's Tim and I'm a truckaholic My 56 Chevy shop truck build http://67-72chevytrucks.com/vboard/s...d.php?t=562795

06-30-2004, 10:41 PM	#19
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Glad you got it figured out, and that it was something so harmless! __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

06-30-2004, 10:49 PM	#20
dubie Registered User Join Date: May 2000 Location: Flin Flon, Manitoba, Canada Posts: 8,853	I gotta give all the credit to TODDS_72, he's the one that suggested it to me, so many thanks go out to my little buddy for all his help. I owe your a beer in INDY Todd!! __________________ My name's Tim and I'm a truckaholic My 56 Chevy shop truck build http://67-72chevytrucks.com/vboard/s...d.php?t=562795

07-01-2004, 07:10 AM	#21
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	Ain't this a wunnerfull web site???? Also, don't our minds go nuts when we hear a little noise and we can't figger it out? Yet, this one had a simple solution and the suggestion came from another board member. Now, THAT'S what I say makes this a wonderful website!! __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

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