Engine Tapping
Thread Starter
Racer
Joined: Jun 2003
Posts: 433
Likes: 0
From: Aspenden Hertfordshire U.K.
Engine Tapping
I am running a basic 350 ci motor in a 61 , the engine is a bit of a "bitza" but has been running fine recently .
It has developed a distinct intermitant tapping / knocking sound during idle , quite loud I thought it was ends or mains initially but have traced it to the top of the motor , it sounds as if there is something loose in the valve covers or inlet manifold and often the sound goes completely but then returns as if something is being thrown around and then lodging for a few seconds . Increasing revs does not seem to make it worse but it is hard to tell with the increased noise of the motor .
I have lifted the valve covers but found no bits , all the rockers seem tight , no sign of broken valve springs , I also took a quick look inside the dizzy , the weights under the rotor are ok , are there larger weights lower down in the dizzy that could be loose / broken ?
The motor also seems to have a slight misfire again intermitant on idle but it is difficult to tie it to the tapping noise .
Your thoughts would be most welcome before I start stripping down to check cam followers or broken cam lobes etc , I am hoping it may be something simple .
TIA
Mike
It has developed a distinct intermitant tapping / knocking sound during idle , quite loud I thought it was ends or mains initially but have traced it to the top of the motor , it sounds as if there is something loose in the valve covers or inlet manifold and often the sound goes completely but then returns as if something is being thrown around and then lodging for a few seconds . Increasing revs does not seem to make it worse but it is hard to tell with the increased noise of the motor .
I have lifted the valve covers but found no bits , all the rockers seem tight , no sign of broken valve springs , I also took a quick look inside the dizzy , the weights under the rotor are ok , are there larger weights lower down in the dizzy that could be loose / broken ?
The motor also seems to have a slight misfire again intermitant on idle but it is difficult to tie it to the tapping noise .
Your thoughts would be most welcome before I start stripping down to check cam followers or broken cam lobes etc , I am hoping it may be something simple .
TIA
Mike
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
I am running a basic 350 ci motor in a 61 , the engine is a bit of a "bitza" but has been running fine recently .
It has developed a distinct intermitant tapping / knocking sound during idle , quite loud I thought it was ends or mains initially but have traced it to the top of the motor , it sounds as if there is something loose in the valve covers or inlet manifold and often the sound goes completely but then returns as if something is being thrown around and then lodging for a few seconds . Increasing revs does not seem to make it worse but it is hard to tell with the increased noise of the motor .
I have lifted the valve covers but found no bits , all the rockers seem tight , no sign of broken valve springs , I also took a quick look inside the dizzy , the weights under the rotor are ok , are there larger weights lower down in the dizzy that could be loose / broken ?
The motor also seems to have a slight misfire again intermitant on idle but it is difficult to tie it to the tapping noise .
Your thoughts would be most welcome before I start stripping down to check cam followers or broken cam lobes etc , I am hoping it may be something simple .
TIA
Mike
It has developed a distinct intermitant tapping / knocking sound during idle , quite loud I thought it was ends or mains initially but have traced it to the top of the motor , it sounds as if there is something loose in the valve covers or inlet manifold and often the sound goes completely but then returns as if something is being thrown around and then lodging for a few seconds . Increasing revs does not seem to make it worse but it is hard to tell with the increased noise of the motor .
I have lifted the valve covers but found no bits , all the rockers seem tight , no sign of broken valve springs , I also took a quick look inside the dizzy , the weights under the rotor are ok , are there larger weights lower down in the dizzy that could be loose / broken ?
The motor also seems to have a slight misfire again intermitant on idle but it is difficult to tie it to the tapping noise .
Your thoughts would be most welcome before I start stripping down to check cam followers or broken cam lobes etc , I am hoping it may be something simple .
TIA
Mike
I'm having a little trouble translating here:
Bitza
Bits
Weights under the rotor
Larger weights down in the dizzy
That aside, I do understand intermittent tapping. I'd say you have a hydraulic valve lifter(s) sticking, worn rocker arms at the valve stem and possibly cut rocker studs. One or all three.
Other possibilities are a sticking fuel pump push rod, broken valve spring and cracked piston skirt.
I'm assuming you have good oil pressure at idle. At least 25 pounds.
I'd look under the valve covers again with the engine running. If it won't tap when you get the cover off, use heel of the hand pressure on the pushrod end of the rocker and see if you get the noise. You can also grasp the end of the rocker and twist it back and forth and see if that sets off the tapping noise.
A rubber heater hose or broom stick from your ear to the engine is also helpful to locate or isolate noises.
If it's a sticky lifter, run some crankcase cleaner through the engine and then drain the oil and refill with the correct type. If you can't find crankcase cleaner, use a quart of Automatic transmission fluid instead.
Melting Slicks
Joined: Nov 2006
Posts: 2,617
Likes: 149
From: Anaheim California
Try doing a "hot" running adjustment on the rockers/lifters. I have had this happen many times and it was an improperly adjusted rocker. A misadjusted rocker/lifter will also cause a engine miss. Try this first, then divulge into the more difficult diagnosis. 
Burning Brakes
Joined: Mar 2004
Posts: 1,108
Likes: 4
From: Plano Texas
Mike M is pointed in the right direction, I believe. Sounds like a sticking hydraulic lifter to me. I would buy a quart of Marvel Mystery Oil from your friendly local auto parts store, drain a quart from the engine and add the Mystery Oil. Leave it in for a couple of weeks and see if the noise goes away. If it does, drain the oil, change the filter and put in some good detergent multi-weight oil.
Thread Starter
Racer
Joined: Jun 2003
Posts: 433
Likes: 0
From: Aspenden Hertfordshire U.K.
Thanks guys , I have had problems with lazy lifters before but this noise is far too harsh for that , it is very loud and sharp ( just like a bad big end noise ) but this is definitely at the top of the motor and is very intermitant , it is not a constant rattle so it is something individual , it taps once every second or two , then goes away completely , there is no definate pattern to it . The best way I can describe it is it sounds like a large nut is being tossed around inside the manifold .
Mike :- Regarding the questions I must appologise for my UK phrasing , "Bitza" refers to something made up from many parts not all neccasarily originally matching , "Bits" replace with debris ,weights under the rotor refers to the centrifugal set up directly under the rotor in the distributor and "dizzy" just short for distributor .
Mike :- Regarding the questions I must appologise for my UK phrasing , "Bitza" refers to something made up from many parts not all neccasarily originally matching , "Bits" replace with debris ,weights under the rotor refers to the centrifugal set up directly under the rotor in the distributor and "dizzy" just short for distributor .
Thread Starter
Racer
Joined: Jun 2003
Posts: 433
Likes: 0
From: Aspenden Hertfordshire U.K.
Have not had time to get to the engine yet for further investigation but hope to spend the day tommorrow , I have been thinking it may be a sticking valve , perhaps too much unleaded fuel and not enough additive ? what do you think ? is there anything inside the distributor that could be loose ?
Race Director
Joined: Oct 2005
Posts: 12,468
Likes: 1,548
From: Camp Verde AZ
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
I would look a for a broken valve spring.
the little inner spring is making the engine run , but the intermittant noise sounds like the big valve spring to me.That noise you are hearing is the piston hitting the valve.
If it is the spring, change the head gasket and have the valve checked for straightness.
Doug
the little inner spring is making the engine run , but the intermittant noise sounds like the big valve spring to me.That noise you are hearing is the piston hitting the valve.
If it is the spring, change the head gasket and have the valve checked for straightness.
Doug
Last edited by AZDoug; Apr 8, 2007 at 04:56 PM.
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Thread Starter
Racer
Joined: Jun 2003
Posts: 433
Likes: 0
From: Aspenden Hertfordshire U.K.
Oh well , spent the morning stripping out the top of the motor and found ( you guessed it ) absolutely nothing . Apart from the usual carbon deposits I can see no faults , all the valve springs removed and in good order , no marks on valves or pistons to suggest any contact , nothing sticking all the valves slid out nicely as did the lifters , no marks on those either . I guess I will have to pull the camshaft to check that as well unless anyone has any other ideas .
Mike .
Mike .
Thread Starter
Racer
Joined: Jun 2003
Posts: 433
Likes: 0
From: Aspenden Hertfordshire U.K.
looks like you may be right Brian , I have just come in from removing the timing chain cover and the chain is pretty loose , certainly enough to slap the caseing . Next job is to remove the cam just as a precaution while I am this far in . It slides out about six inches and then jams I presume as the rear bearings hit the other bearing houses , should it slide completely out without forcing ? or is there something inside the block I should be removing ?I am working with the block in the car , crank case is off but I have not touched the pistons or crankshaft , do I need access from underneath to remove the cam ?
Cheers
Mike .
Melting Slicks
Joined: Nov 2002
Posts: 2,460
Likes: 5
From: Wheaton IL
Pulling the cam out with the block in the car is a pain. THey make handles that bolt onto the snout of the cam to make this easier. The cam gear on the back can really chew up cam bearings so try your best to keep the cam parallel to the centerline of the cam bearing bores.
I didn't buy the handle but I used an old cam gear and some locking pliers to aid in keeping it parallel.
Good luck
Brian
I didn't buy the handle but I used an old cam gear and some locking pliers to aid in keeping it parallel.
Good luck
Brian
Race Director
Joined: Oct 2005
Posts: 12,468
Likes: 1,548
From: Camp Verde AZ
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
an 8" long 5/16"-18 bolt makes a wonderful cam handle.
The cam should slide right out if all the lifters are removed.
Unless you dinged a bearing read bad with a lobe and raised a burr on it.
Fuel pump pushrod? Didn't think about that, I haven't had a mech pump in 25 years, It may need to be dropped.
Doug
The cam should slide right out if all the lifters are removed.
Unless you dinged a bearing read bad with a lobe and raised a burr on it.
Fuel pump pushrod? Didn't think about that, I haven't had a mech pump in 25 years, It may need to be dropped.
Doug
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,923
From: Washington Michigan
The fuel pump pushrod MUST be out in order to pull the cam; there was a hilarious 3-page thread on the C3 forum about a year ago where a guy used prybars and everything but a bulldozer to pull his cam (he had only worked on Fords before, and they drive the fuel pump with an eccentric bolted to the front of the cam sprocket); got it out, but destroyed everything else in the process. 
Le Mans Master
Joined: Aug 2005
Posts: 6,521
Likes: 1,956
From: Temple Terrace Florida
Engine noise
Just a thought, you mentioned that you had carbon on the valves. If there is a lot of carbon on the valves or pistons, that can cause a knocking sound. My 327/350 was loaded with carbon, I suspected the worst and was happy the engine did not sustain any damage. Jerry
Thread Starter
Racer
Joined: Jun 2003
Posts: 433
Likes: 0
From: Aspenden Hertfordshire U.K.
thanks for all the advice , I had foggotton about the fuel pump push rod but now removed the cam slid out with no problem , it looks pretty rough and some quick measurements showed quite a difference between the lobes so a new cam will be installed , I just have to chose what set up to go for as the motor is made up of various parts .
The block has a code of V0109TJT which I believe relates to a truck engine either 69 or 79 , with the sump off this weekend I can confirm it has four bolt mains . Pistons look pretty flat and are +040
The heads have codes of GM18 / F10-71 1971 , 74cc chambers 1.72 intake and 1.5 exhaust , pretty standard I guess ?
Edlebrock Performer C3B inlet manifold and a Holly 600 cfm 4150
Any thoughts on a cam that would suit this mixture .
Cheers
Mike .
The block has a code of V0109TJT which I believe relates to a truck engine either 69 or 79 , with the sump off this weekend I can confirm it has four bolt mains . Pistons look pretty flat and are +040
The heads have codes of GM18 / F10-71 1971 , 74cc chambers 1.72 intake and 1.5 exhaust , pretty standard I guess ?
Edlebrock Performer C3B inlet manifold and a Holly 600 cfm 4150
Any thoughts on a cam that would suit this mixture .
Cheers
Mike .