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Old 09-11-2017, 05:24 PM   #1
dephelps12
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Default Newbie knocking paranoia/ignorance

I recently became the 3rd generation owner of 1930 Tudor rebuilt in the 70ís by my uncle and grandfather. I learned a little bit from my uncle about it before he passed, but not enough of course. First I want to thank all you guys on the Ford Barn for all the great advice and how- toís I have been slowly soaking up over the past year. Iíve managed not to ask any questions yet, since most every answer can be found buried away in these forums, but Iíve grown curious/paranoid about some of the noises the engine makes when I am driving. The Tudor has a newly rebuilt engine (2015) and new distributor that I have timed properly (I think). It starts fine and idles great. When I drive it, I notice a sort of throaty, knock- like sound when it is pulling, primarily when I get into third gear. By this point I have the spark lever all the way down, but if I move it back up the knocking gets more pronounced. Itís not constant, only when I am accelerating/increasing engine RPM. It doesnít sound mechanical (metal-metal), but I just havenít driven the car enough to know if this is something to be expected with the A. Iíve retimed a few times, checked all the points/ rotor gap, tried various carb mixtures, checked the exhaust. Am I trying to fix a problem that isnít there or should I find a REAL mechanic? Iím know I can expect some well deserved scolding if I just donít know what a model A should sound like, but Iíll risk it. -Doug
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Old 09-11-2017, 05:38 PM   #2
Brentwood Bob
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Default Re: Newbie knocking paranoia/ignorance

The distributor should not, IMHO, be firmly tightened at the head, but the retaining set screw on the side of the head that keeps the distributor in place should be tight enough to hold the distributor. There is a notch on the bottom of the distributor casting that the set screw captures. Too much down pressure on the oil pump driver can bind the cam and cause a rapid knock that you might be having. I suspect this since you may have removed the distributor recently and disturbed it.
Bob
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Old 09-11-2017, 06:00 PM   #3
Y-Blockhead
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Default Re: Newbie knocking paranoia/ignorance

Hey Doug. welcome to the barn. It is real hard to diagnose (for me anyway) a sound thru the written word...

Are there any Model A clubs around you that a knowledgable member could listen to your engine? Or maybe a youtube vid?
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Old 09-11-2017, 06:15 PM   #4
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Default Re: Newbie knocking paranoia/ignorance

Possibly an exhaust leak at one of the ports. A leak at one port can sound like a knock, plus exhaust pressure is higher when the engine is pulling or when the spark is retarded, so will sound louder. Open the hood and snap the throttle open while listening. An exhaust leak sounds more like a 'spit' than a 'knock' but some experience is needed to identify. If you suspect an exhaust leak, pull the manifold and look for a burned gasket or trace of black soot. If it is a leak, remember that sound!
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Old 09-11-2017, 07:13 PM   #5
dephelps12
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Default Re: Newbie knocking paranoia/ignorance

Thanks for your speedy relies guys. I checked the bolt for the distributor, seems ok. Exhaust leak make some sense, it is probably better described a growly popping/ spitting sound. It sounds similar to the leak this gentleman was havng at idle, but only occurs at higher, loaded RPMs, so with a higher frequency.
https://www.youtube.com/watch?v=44gUJGynnw0
There is no visible soot around any of the ports with the manifold on, but it stands to reason it could be a very small leak since it only shows the symptoms under conditions of maximum pressure, or perhaps between the muffler and manifold?
I could get a little popping by opening the throttle at idle but it doesn't sound very pronounced in the video, I will try and make one driving. https://www.youtube.com/watch?v=taIsMF3UlCA
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Old 09-11-2017, 07:25 PM   #6
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Default Re: Newbie knocking paranoia/ignorance

You list New Orleans and Fredericksburg as your home. There is a real good engine guy in Fredericksburg. Where is the car located?
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Old 09-11-2017, 07:56 PM   #7
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Default Re: Newbie knocking paranoia/ignorance

Just for kicks, retorque your head if you have not done it for a while.
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Old 09-11-2017, 08:34 PM   #8
1930artdeco
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Default Re: Newbie knocking paranoia/ignorance

Welcome to the club! Here are two things you can try:

Exhaust leak-spray some wd-40 around the manifold and if the engine sound changes there you go. Easy peezy to change the gasket.

knock-short out each plug if you can hear the knock sound at an idle. If the sound goes away then you have a bad rod bearing.

Mike
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Old 09-11-2017, 09:01 PM   #9
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Default Re: Newbie knocking paranoia/ignorance

Don't drive it with the spark lever all the way down. Bad for your rear main.
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Old 09-12-2017, 09:50 AM   #10
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Default Re: Newbie knocking paranoia/ignorance

welcome to the hobby! You should visit mafca.com and find a local chapter to visit. There will be friendly folks that more than likely will give you advice on where to get things done and probably offer to help you get it dialed in.
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Old 10-12-2017, 02:37 PM   #11
dephelps12
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Default Re: Newbie knocking paranoia/ignorance

took me a while to get to it but I did track down an exhaust leak...Thanks for the pointers fellas! Will try gasket first and then manifold if it is warped, I hear they have a tendency to do that...
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Old 10-12-2017, 07:47 PM   #12
glenn in camino
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Default Re: Newbie knocking paranoia/ignorance

Most model As make strange sounds. If you belong to a local Model A club, Have a club member listen to your engine, and ask his opinion of the noise. I could be normal.
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Old 10-13-2017, 01:46 PM   #13
Will N
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Default Re: Newbie knocking paranoia/ignorance

Quote:
Originally Posted by Brentwood Bob View Post
The distributor should not, IMHO, be firmly tightened at the head, but the retaining set screw on the side of the head that keeps the distributor in place should be tight enough to hold the distributor. There is a notch on the bottom of the distributor casting that the set screw captures. Too much down pressure on the oil pump driver can bind the cam and cause a rapid knock that you might be having. I suspect this since you may have removed the distributor recently and disturbed it.
Bob

This is very interesting to me. I've been having what I describe as a rattle coming from my engine. I've not checked if perhaps the distributor shaft is too long, causing the binding you mentioned. I will check that for sure!
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Old 10-13-2017, 08:59 PM   #14
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Default Re: Newbie knocking paranoia/ignorance

Quote:
Originally Posted by Y-Blockhead View Post
Hey Doug. welcome to the barn. It is real hard to diagnose (for me anyway) a sound thru the written word...

Are there any Model A clubs around you that a knowledgable member could listen to your engine? Or maybe a youtube vid?
X2

My imagination will run wild with the symphony of noises my A can make. Luckily a member of my club (read the thread "Have wrench, will travel") is an expert model A mechanic. Before this summer season I took him on a 5 mile ride and asked him to just listen, and let me know if he heard anything that indicates a problem. He said it all sounded normal to him, "But what kind of gas was I running?" His nose told him that I was not running "normal" gas. I had filled the tank with racing fuel (the only non ethanol gas available around here) for the winter. I was impressed!

After his "all is well" diagnosis, I relaxed and enjoyed my summer driving much more.
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Old 10-14-2017, 08:05 AM   #15
mike657894
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Default Re: Newbie knocking paranoia/ignorance

I thought I had a knock at idle. It happened to be the passenger door opening stop that enters the cab bouncing off the lower cowl panel.
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