Engine knock ---driving me crazy

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration
Model T Ford Forum: Forum 2011: Engine knock ---driving me crazy
Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom VanMeeteren on Wednesday, November 30, 2011 - 07:14 pm:

I admit that most of the time I don't have far to go to be crazy but this engine knock is getting me a lot closer!

This is a complete overhaul job with .040 pistons, chevy valves, new springs and oversize lifters, rebabbited mains and rods, crank turned, all the right stuff. We have had the engine out 3 times trying to identify a knock. It is defintely crank or camshaft related.

This is additionally I have done in one of the three times it has been out. New nylon timing gear and front bearing, plastic gauge rods and mains. .002 on mains and .0015 on rods. I have taken a facing cut across the flange on the crankshaft of .007 to clean up the runout. Also did the same to the trans shaft and took off .005. Replaced the 4th main with standard bore as there was only .001 wear on the tail shaft. I have checked the clearance between the rod bolts and the camshaft. Checked clearance on the oil funnel pipe. Replaced the front pulley with an aluminum one because there was some rattle there.

The cam is the original as are the middle bearing and the third brass bushing/bearing. I have noticed that two of the lifters do not rotate when the engine is running. Pulled the head late this afternoon and checked to see if anything was hitting the head, I have about .200 clearance there. Number 3 piston is like brand new and shiney while 1, 2 and 4 have a lot of oil/carbon starting to buildup.

I have had two older retired mechanics listening to this engine and neither one of them has any more ideas. One brought along his stetescope and microphone and couldn't really pinpoint where the knock was coming from.

I plan to pull the engine again in the morning and probably replace the cam and the two rear bearings.

Please give me some more ideas so I won't go the nut house


Top of pagePrevious messageNext messageBottom of page Link to this message  By joe bell on Wednesday, November 30, 2011 - 07:33 pm:

I had one that the piston was hitting the head gasket, there was some head gaskets that where from India and the holes where all over. Take a look at the gasket to see if you see a shiny spot.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Gould on Wednesday, November 30, 2011 - 07:34 pm:

Just a couple things to look at
1. Side to side clearances of the rods to the crank pins.
2. Center main cap clearance. I heard about one case where the fellow used a front cap on the center main and the horizonal clearance was so close the crank banged against it when it got warm.
3. Cam front main. If you have the early style front bearing, the lobe may be banging against the notch. Pretty common, actually.
4. Steering shaft banging where it goes thru the column on the firewall. Often the holes are buggered out and there is banging that sounds like a knock when the car is running down the road.
5. No or weak crank spring allowing the crank ratchet to make contact with the pin in the crankshaft while trundling down the lane.
6. Exhaust pipe loose in the muffler or a loose exhaust nut at the manifold.
I am sure others will chime in with some additional suggestions.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom VanMeeteren on Wednesday, November 30, 2011 - 07:35 pm:

This knock is defintely a hard metal knock like a rod bearing knock.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rick Goelz-Knoxville,TN on Wednesday, November 30, 2011 - 07:35 pm:

Try retarding the spark until the knock goes away,high compression heads are bad about doing this.
Rick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom VanMeeteren on Wednesday, November 30, 2011 - 07:40 pm:

Richard, no side to side movement on the rods, I will check the center main idea, #3 new front cam bearing reamed with a set of Ford reamers and turned in the lathe so I have .005 end clearance, definetly not the steering column, had it running this afternoon without the crank and claw in the car, exhaust nut, pipe and manifold all new and tightened TIGHT with the correct wrench.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom VanMeeteren on Wednesday, November 30, 2011 - 07:43 pm:

Also noticed a small burn mark or hole about 3/8" in diameter in number 2 combustion chamber on the head. This "hole" is about .050 deep. I have had the car running for a total of about 2 hours with people listening to it and giving ideas. Retarding the spark does not make it go away.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Bender Tulsa Oklahoma on Wednesday, November 30, 2011 - 08:02 pm:

If you ground out the plugs one at a time, is the knock still there?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren. (Australia) on Wednesday, November 30, 2011 - 08:39 pm:

maybe the timer? off centre, or 1 post not true, firing that number 2 to far advanced!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting on Wednesday, November 30, 2011 - 09:25 pm:

Check your rod alignment, twist, bend, and off set, and crank centering in the block. Pictures of the crank, and rods still in the block, to see spacing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting on Wednesday, November 30, 2011 - 09:32 pm:

Check your rod alignment, twist, bend, and off set, and crank centering in the block. Pictures of the crank, and rods still in the block, to see spacing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Neil Kaminar on Wednesday, November 30, 2011 - 10:08 pm:

Tom,

Was the "burn mark" there before you ran the engine for 2 hours?

Neil


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom VanMeeteren on Wednesday, November 30, 2011 - 10:14 pm:

Grounding out the plugs makes no difference, I centered the front cover for the timer. The engine is back out of the car. Will take a look at the cam and the rear two bearings in the morning. We had the rods poured by a guy that has a shop that poured babbitt since 1906. He's done a lot of engines for me over the years and would surely have caught a bent or twisted rod.

I will take a few pictures of the bottom end in the morning and post them.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom VanMeeteren on Wednesday, November 30, 2011 - 10:14 pm:

Neil, don't know about the burn mark. It is a brand new Z head.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George - Cherry Hill New Jersey on Wednesday, November 30, 2011 - 10:45 pm:

Sounds to me like #3 isn't firing right so grounding it out wouldn't make any difference anyway! Within reason, they all should soot up or carbon stain alike....

New engine rebuild, could be piston slap and thats why it defies stethoscope, but piston slap should go away at hot and higher RPM...

Before I'd go to a teardown, I'd really look to see whether #3 is firing at all, and firing in the right order at the right intensity! I had one recently where it had brand new 25's and it would need to run richer more than I liked to run, but would run. Yet pounded to beat the band when labored at higher speed. Turned out that new plug in #3 did not have the top electrode mounting stud tight to the electrode itself, and there was some St. Elmo's fire taking place. Eventually dropped in another plug after pulling my hair out on everything else, and started to purr like a kitten :-( The quirks of playing with a T


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting on Wednesday, November 30, 2011 - 10:53 pm:

Tom, don't expect anything, check it your self, There isn't a rod machine made that will machine a rod straight enough to put in an engine, that is why rod aligners are a must. I have only found one Model A rod that had checked aligned, and that was by accident only.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett on Thursday, December 01, 2011 - 12:01 am:

Tom,

You mentioned fitting a new front cam bearing, reaming it etc. Is it a good fit in the block? I have traced a couple of persistent knocks to loose cam bearings in the block tunnels. The problem was cured with a shim fitted around the bearing to make it a good fit.

Maybee this will help.

Allan from down under


Top of pagePrevious messageNext messageBottom of page Link to this message  By BOB TREVAN on Thursday, December 01, 2011 - 01:06 am:

Sounds like the transmission planetary gear bearing face being worn which allows the gear to move back and forth and slap the flywheel .[ check for gear marks on the flywheel].

BOB T


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis, In. on Thursday, December 01, 2011 - 06:30 am:

Tom, I posted the similar problem a few months ago. I traced my issue to the Z head. Had the same knock on 2 different engines with the same head. Both engines were tight on all tolerances. The one engine was new. Pulled the head off and put an iron head on and the problem went away. Having the timing backed off when running on mag would lessen the knock, but on accelleration the knock was still there. I thinking most people running Z heads are probably using distributors and can adjust the timing to where there is no knock. With me running on mag and coils I've only got 22.5 deg timing intervals to adjust by. Contact me off line if you want to compare more knocking details.

The other over looked posssibility is having the mag ring too close to the magnets at the bottom of the flywheel. The mag ring osolates quite a bit while the engine is running and can contact the magnets.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom VanMeeteren on Thursday, December 01, 2011 - 08:01 am:

Allan, I plan to check the cam bearings and the fit of the bearings in the cam tunnel this morning.

Bob, the transmission was rebuilt and bearings were replaced and ream fitted to recommended tolerances.

Kenny, I am begining to think the Z head might be the problem what with the burn depression hole on number 2. When it goes back in, I plan to put a cast iron head back on it. One of the retired mechanics said it sounds like a diesel running with the knocking.

George, when we ground out #3, there is a definite drop in rpms and the engine starts to labor a bit and run rough so I am sure it is hitting on #3 but why is the piston all shiney clean? I will change the plug on #3 and see if that does the trick when it goes back in. Piston slap is not a problem, I have had this shop bore engines for me for about 20 years and they are always spot on with their bore jobs. When I wiggle the piston at the top of the stroke, there is no wiggle, nor at the bottom either. The knock is there when we start the car right away, and makes no difference what the rpms are.

To all, prayers would be greatly appreciated, not for the car but for my mental sanity.

Tom


Top of pagePrevious messageNext messageBottom of page Link to this message  By paul griesse--Granville,Ohio on Thursday, December 01, 2011 - 10:17 am:

I think you are "on target" with the Z head--Like Kenney (above) I`ve also had knock issues with aluminum pistons hitting the aluminum head--its an easy "fix" to mill out the head. If installing a std head ends the knock problem, a little work on the Z head should put you back in business (and keep your mental health intact....) Paul


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris on Thursday, December 01, 2011 - 10:46 am:

As Kohnke says above, we had an awful rod knock in our 1913 T Touring and it wound up being twisted rods which were causing a piston slap. It's worth a try to take a look at it and the engine doesn't need to come out of the car to check it and fix it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Doolittle USA!!! on Thursday, December 01, 2011 - 09:58 pm:

Why not...remove the z head and replace with the std head...see if the knock goes away. It will cost you a couple of head gaskets, but they are cheap & easy.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Friday, December 02, 2011 - 03:58 am:

If the head gasket haven't been used for more than startup tests to diagnose knocks, then I wouldn't hesitate to try reusing it. First I'd try the Z head on without a gasket to check if the pistons really goes free..? There have been many reports on the forum about z-heads needing grinding for clearence in the area above the pistons in cyl 1 & 4.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis, In. on Friday, December 02, 2011 - 06:26 am:

Mine didn't have any clearance issues. I bolted the head down with out a gasket to check clearances. The copper head gaskets can usually be reused if your careful and use the copper gasket spray. On the new engine the knock sounded like it was a rod, main or wrist pin. After tearing the engine down, all of that stuff was still perfect. I had put the original motor back in the the car after freashening it up and drove it for awhile. After a few weeks I decided to put the Z head on that engine to see how much diffference the Z head would make. This engine developed the same identical knock. I put the iron head back on and the noise was gone.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Harold Schwendeman on Friday, December 02, 2011 - 11:35 am:

Tom - You mentioned that the knock is at all rpm's; I had a crankshaft pulley come loose due to the pin working it's way partially out. The pin only came out part way due to hitting the little cup shaped portion of the oil pan at the front of the engine and under the pulley with every revolution. Sure sounded like a rod knock,.....very steady and regular at all rpm's of course. Something I'm sure you would have seen right away, but otherwise, worth checking.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting on Friday, December 02, 2011 - 05:36 pm:

In my opinion, if you have a set of Rods out of alignment, they will make sound. If they are not out an extreme amount, the may not make a large amount of sound to where you don't consider the sound a threat to you, but you will be getting wear. Now, with the stock low compression head, you may not notice the sound that should not be there, and when a High compression head is added, it compounds the pressure on the rods and pistons, making a sound that was not there before, so what ever you changed catches the blame, and yes, if there is some thing wrong with head or gasket, it should be fixed. But there is one thing for sure, if you put your engine together, and didn't have the alignment checked for Twist, Bend, and Off set, your rods are Bent to some degree, and that is fact!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John T. Tannehill on Sunday, December 04, 2011 - 07:29 pm:

It could be as simple as the boring of the cylinder holes not being straight. If that is the case you will have an immediate knock that will not stop until a piston seizes or something worse


Posting is currently disabled in this topic. Contact your discussion moderator for more information.
Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration