Odd Ping - Power Loss -

[James_Douglas]

Hi Guys,

 

Dead tired and heading to the bath tub with some Scotch! 

 

I pulled the thing apart in place.  I have #5 slug out on the bench.  Here is the quick version:

 

1. Piston looks fine.  Very fine in fact for 40K miles.

2. Rings look ok.

3. Intake valve looks ok.

4. Exhaust valve has some odd things on the face.  At three places it looks like someone hit it with a small blunt chisel point. Perhaps the sparkplug tungsten exiting?  Also, across about 30 degree of the circumference the parting face looks a little scaly.  The is at the same point on the deck where there is carbon build up next to and up against the valve.   

5. I pilled the freeze plug above the oil filter boss and went fishing.  The #4 and $5 cylinders are clear to the base in the water jacket.  I ran my brushes down all the cooling holes in the block and everything looks good cooling wise.   

 

Preliminary conclusions:

 

The exhaust valves may have been a little too tight allowing some carbon to build up on the face and allowing pressure to bleed off.  The rings may have just warn quit a bit with my heavy duty use in San Francisco traffic.  With the Suburban at 4500-5000 pounds I have to use full throttle a lot in city traffic to get that hulk moving.  Perhaps the gasoline wash down of #5 when the plug died caused it to eat the rings because of the gas. Number 5 hole "looks" a little more glassy than the rest.

 

What caused the lean condition in the first place?  Who knows.  I will check the carburetor in the AM.  I am running 306 plugs.  Hot.  I am wondering if the high compression I am running about 8 to 1, with light carbon build up thus increasing the CR, coupled with winter blend and hot plugs all conspired to cause a problem in maximum load full throttle conditions.

 

I am going to run 303 plugs, colder and I am going to see if I can find a 15% richer main metering jet that will fit my carburetor.  I am going to put new rings in and grind and lap the valves. 

 

As an aside on the subject of cam lobe wear.  I never use any of the zinc or other additives other than break-in grease when new.  I run regular oil and change it a couple of times a year.  When on my back looking up with a light, I can see almost no wear on the NOS camshaft lobes.  Just some gloss on them.  No ridges and no scuffing.

 

Check back in tomorrow night.

 

James

 

 

 

 

[Don Coatney]

You can check the cam lift/lobe condition with a dial indicator. I did so to insure I had ample head clearance when I installed my re-ground lumpy cam. Where there any indentations in your head indicating something bouncing around in cylinder #5? What is your valve lash set at? Always better to favor a loose setting as opposed a tight setting as a tight setting will burn valves over time. Pictured is what my Graveley  tractor piston and head looked like after a bit of metal found its way into the combustion chamber.

 

 

 

[greg g]

As long as the exhaust valve sealing areas are in good shape, I would tend to not worry about pitting on the top face of the valve caused by the plug piece. If your exhaust valve was adjusted to tightly, your valve was probably not closing all the way at top operating temp. The valve gets cooled by it time against the seat. If it was not fully seating it may have been getting hot enough to light off the ignition charge way early, The lean condition may have resulted from a portion of the charge blowing by the exhaust valve on compression. I wouldn't mess with the carb till you get the valve issues sorted. Your Number 5 cylinder could probably use a light honing especially if you are considering new rings. The cross hatch is need to help seat the valves.

[Ulu]

I found little x-shaped dents in a piston top once. A choke plate screw had cracked or something when I overtightened  & staked it. Anyhow the head had gone through a cylinder.

 

Any chance maybe there was some valve float on that cylinder?

 

I doubt these engines turn fast enough normally, but if there's one weak valve spring then perhaps.

Edited April 29, 2014 by Ulu

[James_Douglas]

You can check the cam lift/lobe condition with a dial indicator. I did so to insure I had ample head clearance when I installed my re-ground lumpy cam. Where there any indentations in your head indicating something bouncing around in cylinder #5? What is your valve lash set at? Always better to favor a loose setting as opposed a tight setting as a tight setting will burn valves over time. Pictured is what my Graveley  tractor piston and head looked like after a bit of metal found its way into the combustion chamber.

 

 

 

 

 

Hi Don,

 

No indication that the anything hit the head.  I did note however that an Auto-lite 86 power tip plug does stick more into the cylinder than a 306 plug.  A lot more. 

 

The underside of the Stainless Steel exhaust valves are showing a lot of micro pitting on the sealing face of the valve.  No indication of burning out, just an "crocodile" pit-scaling look.  This may be the reason for the loss of cylinder pressure.  Also #5 hole "feels" a little more smooth than the others.  Perhaps the gas washed the cylinder and the rings did not have proper lube and glazed the walls of #5 a bit.

 

I took the pistons and rings and stopped by a shop here in SF run by a 75 year old who has run the shop for decades.  He is a member of the Model A club and he works on all kinds of old cars and was originally an A&P mechanic. He, his son, and now his grandson are the only people within 100 miles I trust to work on my cars if need be. He things the pistons and rod bearing look great for 40K miles.  The exhaust valves he things need grinding.

 

His son a great mechanic also, stopped my on the way out and said hold on.  He went into a back room and came out with an original box of 30 over Sealed Power Rings.  They have a bunch of old stock and he just gave them to me!

 

I then took the stuff to my machine shop and had Bruno and 80 year old machinist, that does all the fancy engines for Roy Brizio Street Rods, and Bruno said that the exhaust valves need grinding.  He also said the rod bearing are ok, a few scores, but fine.

 

I am on the fence as to if I should put in new rod bearings, with all the associated pain of checking each one under the car with plastic gauge or just use what I have.  There is some light scoring on a few of the bearing at the oil feed oil.  My guess is something in the oil gallery that did not get cleaned out or more likely something in the crankshaft part as I acid dipped and cleaned the block myself.  The crank however was done at and installed at the machine shop.

 

I am cleaning the all the parts and will but a new rear main bearing seal in.  In the next couple of days, I will get the valves back and start putting the thing back together.

 

The one thing I did note was a shinny spot on the bottom front and back of the cylinder bores.  The thrust of the pistons at BDC as it comes around must put a lot of pressure on the those locations.

 

When I put the valves in, I will check and see what the actual lift is for fun.  With everything out, I ran my hand over all the cam lobes and cannot feel a thing wear wise.  The lobes have a shinny spot on them where the lifter is riding over the lobe, but no pitting and no grooves.  At 45K miles, so much for the zinc arguments.

 

Best, James

[Don Coatney]

Remember the actual valve lift will be minus the lash adjustment. In other words my cam was ground to a .410 lift. My indicator reading was .396. .410 minus the lash of .014 (cold) for an indicator reading of .396

[Dodgeb4ya]

Proper valve spring tension is critical. New valve springs 40,000 miles ago?

Bob

Edited April 30, 2014 by Dodgeb4ya

[James_Douglas]

Proper valve spring tension is critical. New valve springs 40,000 miles ago?

Bob

Brand New 40K ago.

[James_Douglas]

Saturday.

 

Well, I got the cylinder bores honed.  Only pulled three muscles in the process.

 

I started to put the free decades old Seal Power piston rings on the pistons.  Guess that, the send lower oil rings cast part snapped in the wrench!

 

They were 0.030 and looked good, however they had the 4 part lower oil ring.  A real pain in the ass.

 

So, I am stuck until I can order some new ones on Monday.

 

Anyone have an suggestions on rings?  Egge has them as does NAPA all are no doubt Federal-Mogal E-107x30.

 

The folks from Total Seal said they can make up a set for me.  I am wondering if it is worth it.

 

The valves and seat are all set to go.  A nifty little tool I bought of ebay years ago worked great cleaning up the seats.  It uses little round sandpapers of three different grits.  It has screw in shafts that fit the valve guide and you just drop it in and spin it.  After that, I used some fine lapping paste and checked the re-ground valves and they all have a nice line all the way around.  Good to go on that.

 

Tomorrow, I will clean up the block real well and change the rear main seal.

 

James

[James_Douglas]

As I wait on rings and things...

 

I took the Carter Carb apart.  I found the smoking gun.  The Step-Up Piston was stuck most of the way down. 

 

At full throttle under a full uphill load the Carburetor was not supplying sufficient fuel.

 

See: http://www.imperialclub.com/Repair/Lit/Master/010/Page17Big.jpg

 

It looks like some slight aluminum corrosion caused the little piston to hang up.  It has done this once before some years back but at the open position causing the car to run a little rich.

 

I suspect that either this alone caused the problem and/or this problem coupled with the Winter Fuel on a hot day did it.

 

The upshot of all this is that a $1 part can lead to a very big problem that you will only find out about on the outer edge of the power/load envelope.  I suggest that everyone check this piston one a year.  I will be.

 

The carb in question is a NOS carb with about 5 or 6 years on it.  It never saw any lead so the passages are not enlarged do to the lead passing through it.  However, the alcohol in the gas is evidently slowly causing issues in places were the water H2O has separated and allowed to stand away from the fuel flow.  Like the little piston hole at the top of the carb.  Makes sense as there is a little air draw through that hole in the top of the piston down to the first "ring land".  The water vapor then hits the aluminum and causes issues. 

 

I may take the carb and have my machinist take out 5 or 10 thou out of the bore and sleeve it with a bronze-oil-lite bushing.

 

The alcohol in the fuel is going to be an ongoing overtime maintenance issue.

 

James

Edited May 7, 2014 by James_Douglas

[Don Coatney]

James;

Glad you found a problem and I hope that is THE problem. Keep us posted on the outcome once you are back on the road.

[greg g]

James. I mentioned the intermediate jet/vacuum circuit in post three. Sticky ones can cause mixture problems whether stuck open or closed. With your hill climbing demands itsprobably even more critical than us flatlanders. Did you get rings yet? Terrel inTx has em more than likely.

[Jeff Balazs]

As I wait on rings and things...

 

I took the Carter Carb apart.  I found the smoking gun.  The Step-Up Piston was stuck most of the way down. 

 

At full throttle under a full uphill load the Carburetor was not supplying sufficient fuel.

 

See: http://www.imperialclub.com/Repair/Lit/Master/010/Page17Big.jpg

 

It looks like some slight aluminum corrosion caused the little piston to hang up.  It has done this once before some years back but at the open position causing the car to run a little rich.

 

I suspect that either this alone caused the problem and/or this problem coupled with the Winter Fuel on a hot day did it.

 

The upshot of all this is that a $1 part can lead to a very big problem that you will only find out about on the outer edge of the power/load envelope.  I suggest that everyone check this piston one a year.  I will be.

 

The carb in question is a NOS carb with about 5 or 6 years on it.  It never saw any lead so the passages are not enlarged do to the lead passing through it.  However, the alcohol in the gas is evidently slowly causing issues in places were the water H2O has separated and allowed to stand away from the fuel flow.  Like the little piston hole at the top of the carb.  Makes sense as there is a little air draw through that hole in the top of the piston down to the first "ring land".  The water vapor then hits the aluminum and causes issues. 

 

I may take the carb and have my machinist take out 5 or 10 thou out of the bore and sleeve it with a bronze-oil-lite bushing.

 

The alcohol in the fuel is going to be an ongoing overtime maintenance issue.

 

James

Hi James;

This has been an interesting thread. I wonder how common this problem is with the step up piston bore? When I had my carb apart recently I noticed this piston seemed to be binding a bit. I wonder if the bore could just be lightly honed? or if it should really be sleeved?

 

Jeff

[James_Douglas]

Hi Greg,

 

I remember your post.  I just did not bother to check it until I had some down time in the action while awaiting gaskets and rings. Once #5 hole was 70 PSI, I knew I had to take it apart to check the ring lands on # 5. Especially with most of the plug tip gone.

 

I am also running Autolite 306's which are almost as hot a plug as you can get.  Mainly for the city stop and go driving.  I think the sticking piston, the 306's, and possible the fuel all combined to cause the problem.

 

The piston is now free.  I am going to run 303's which are colder.  I am also going to rebuild one of my other carbs and I am going to bore and sleeve the little piston hole with a bronze-oil-lite bushing. 

 

A few of us had lunch today and talked about the issue.  The very top of the little piston has a hole in it that exits inside the large upper "ring land".  The vacuum pulling from below will suck air from the top of the float chamber.  Any moisture, from the alcohol, will sit up there and get sucked down into the piston hole.  As it passes the brass piston some of it will condense at the brass piston/aluminum wall interface.  This is no doubt what caused the slight corrosion I saw and what caused the piston to hang up. 

 

I had this carb apart about 2 years ago and it was hanging up a bit.  I had cleaned the bore and polished the brass piston.  I suspect that the cool temperatures here in SF with city driving may also be adding to the condensation issues. The salt air may also be playing a role.

 

Even though taking it this far down in a pain, at least I know that the piston is not cracked.  The thought of taking a gamble and having a piston seize and tossing the rod through the block was never far from my mind.

 

James.

[Jeff Balazs]

James;

I have been struggling with an intermittent situation with my carb for a while now. I believe this step up piston may be sticking sometimes in the up position on my DTG1. Thanks for sharing your experience with this here. After several attempts to get this resolved I finally feel like I know what to focus on.

 

Jeff

[greg g]

If your step up is stcking open you will be running rich. Symtoms may vary for low fuel milage, to black smoke exhaust , to fuel fouled plugs. Cause can be as simple as improper or incorrectly installed carb to manifold gasket as that is the vacuum signal source for the circuit. Or as James has noted corrosion from our good friens ethanol.

[James_Douglas]

Hi Guys, Got the valves back in and adjusted.  Much more easy when the pistons are out and you can turn the crank by hand as you go through the valves.

 

While under the car, I took a photo of a cam lobe.  The wear pattern is correct to one side. (http://www.imperialclub.com/Repair/Lit/Master/027/Page12.htm)

 

The big thing to note is that the cam looks just fine after 40 or so thousand miles in city and highway traffic. I have never used any additive in the oil.  I do change the oil once in the spring and once in the fall.

 

So much, as I said in a previous post, for the zinc myth. 

 

James

 

 

[Lumpy]

I don't really see a wear pattern...other than on the peak of the lobe. ?? maybe someone sneaks zinc into engine when you are asleep at night.

 

ken.

[James_Douglas]

I don't really see a wear pattern...other than on the peak of the lobe. ?? maybe someone sneaks zinc into engine when you are asleep at night.

 

ken.

 

 

Hey Ken,

 

I never thought about that! 

 

:-)  James

[Adam H P15 D30]

There isn't enough valve spring pressure in our flatheads to warrant zinc. It is really for OHV engines with high spring pressures. I only use oil with zinc in my OHV engines with FT cams. Waste of money in our flatheads.

[James_Douglas]

Hi All,

 

I wanted to swing back to this post to let you all know I got the car back together this weekend. Took it for a long ride down south to a car show and it ran fine.

 

Spent a good part of the day talking with Tod Fitch.

 

I am going to pull a plug and see what she reads today.  By the way.  There were several different high load - high speed jets on the BB.  I got one of the larger ones and I am using that.  If you have added a hot cam or are in need of a more rich mixture under higher loads, look into it. This is the jet that the rod goes into, not the main metering jet.

 

*************

 

QUESTION.  Are both the "nuts" 9/16" on the tappets?  I know one of the are as I just set them last week.  I want to buy a set of tappet wrenches, but I just don't remember if I grabbed two 9/16" open ends or one 9/16" and something else.

 

Thanks, James

Edited May 19, 2014 by James_Douglas

[Niel Hoback]

  I just measured a tappet, use 1/2" on the body and 7/16" on the nut.  You don't really need tappet wrenches, just so they aren't real fat cheap wrenches.

[Joe Flanagan]

I ran one of my open end wrenches over a grinding wheel for a bit to flatten it out so it can be used to adjust the vales. I seem to recall I only had to do it for the 7/16 wrench and the 1/2" I just used as it was.