Cracked babbitt

[SAJ]

I Pulled apart my Touring engine, bought from Snyders 17000 miles ago. The engine is babbitted and was built by Schwalms 5 years ago. I thought it was developing piston slap and suspected no 3 piston, which nipped up without damage at 4000 miles. But No 3 will take a 0.002 inch feeler up the skirt but not a .004. So probably .003 to .0035 clearance and OK.
Rods all plastigauge at .0015 inch and mains the same. But on removing the rods the Babbitt in the rod tops is badly cracked in two and has minor cracks in the other 2. See photos attached. Rod caps look OK to me, and mains have unusual marks but seem OK. The photo plays tricks with the light, and the centre main has dull and shiny patches but is not flaking as it appears in the pic.
Car has a 26% Mitchell O/D and I am paranoid about not lugging it or over advancing it on long steep hills. I change down at 35 mph into 2nd overdrive and max advance is fixed (by a stop on the quadrant) at 29 engine degrees. It never detonates or pings and I retard a notch or two on hard pulls.
So I am very surprised to see the babbitt fatigued and cracked as it is.
Ora Landis advised to retard the timing a bit more but made no other comment via Tom Jordan at Snyders.
I am going to fit Snyders new rods with .020 shells-the type with side thrusts built in.
The shaft is 1.4774, .001 under the 20 thou regrind and using Snyders figures I should get .0025 clearance, but in a trial fit with another club member’s new rods from Snyders I got .0015 with plastigauge. When mine arrive I may have to do a little hand fitting to lose that extra “thou” I guess.
Purpose of this post is to ask opinions on what happened, since I use the car to its max potential but keep revs below 2500 (low gears on hills) and run at 55 mph, with an occasional max of 60.
I have rev counter, temp gauge, thermostat, oil pressure gauge, exhaust gas temp gauge and keep an eye on it all. Engine runs at 140 Deg max despite the 160 deg thermostat. I don’t know why, since the stat tests out at 160 deg on the bench, but my wife’s Tudor with a similar engine that I built up myself runs the same – just below the green on her gauge
I follow other members up hills where they stay in top to 25 mph, where I have changed down and am running light way before them.
My car is 120 thou over bore, Stipe 330 cam, Model B carb, 95 psi Compressions and 10% leakdowns. No sounds or signs of detonation on plugs etc, and just a “slapping” noise on light running on a cold engine, which goes away as it warms. Oil is Mobil 10W-50 V-Twin (higher ZDDP etc) and I did run Mobil1 4t 10W 40 for a short while. Filter is Z9 full-flow.
I hope the thin-wall shells are tougher in the babbitt film than the cast bearings!
This is the same engine whereI posted about a cam train knock. I see nothing wrong here but will replace both timing gears whilst down

Thanks for any advice and hopefully some encouragement for the next 20000 miles.
SAJ in NZ

 

[H. L. Chauvin]

Always difficult to recognize a problem from far away and furthermore, these comments may not be the cause of your particular problem; however, FWIW:

A few years back Mr. Ron Kelley was telling me he has noticed that a lot of the cracked connecting rod "top-half" Babbitt problems that he saw brought into his shop was caused by Model A Owners beating up their "top" connecting rod Babbitt on their crankshaft journals because their Model A distributor manual timing stayed too far advanced for different engine's RPM's.

He described it to hitting the top of the piston with a big maul while holding the crank arm fixed at 90 degrees to the horizontal, where the crank cannot move and cannot rotate; hence, the "top" Babbitt in the connecting rod takes this forceful beating, but, the bottom half remains unharmed.

You will get other comments & opinions that may or may not help to resolve this problem ..... if more details are given, more comments will follow.

 

[SAJ]

Thanks H.L. I guess my question is how do you know how much is too much ignition advance?. I have always followed the method that max. achievable timing is set to just before detonation or pinging occurs and this has worked in many tuned engines I have worked with. My car cannot go beyond 29 deg BTDC and will not ping at this setting. I back it off from here for big hills. In contrast I see many club members who proclaim "I just pull the lever right down and leave it there". Allowing for slop and friction, they are still probably up above 30 or 32 deg, though on lower compression engines (the "full slot" is 40 deg but most A's I work on cannot achieve "full slot")
So, given my engine never detonated, how much is enough advance, bearing in mind that my lever is calibrated against a timing scale on the front and I set it up with a timing light, so I know roughly how many degrees I am running at any time. Should I limit it to 28 deg max, 26 deg or what?
I would like to know so I don't wreck the rod bearings again. It does seem thick babbitt is more prone to stress cracking than thin shell babbitt, from what I was taught and now experience.
But do Bonneville racers like Jim Brierly, and circuit racers have to stay back from max power to watch their babbitt in Model A engines? If so I was not aware of it.
I have to assume here that the bearing job was good and the alloy used a good non lead one - the assembler has a great reputation.
So I guess I killed it myself!
SAJ in NZ

 

[Rex_A_Lott]

I'm no engine expert, but I read a lot, and try to learn...I remember Smokey Yunick describing detonation and the damage it causes. I cant quote it exactly, but it something along the lines of, " By the time you hear it, the damage is done"...So I dont really think you can say your engine never detonated.
I'm pretty sure the experts are going to want to see pics of the tops of the pistons and the head, so they can look at the flame travel.
Smokey also talked about going to Indianapolis, and it being a once-a-year event, and on race day he taped over the gauges and said " Run her til she pukes". I imagine the same mentality prevails at Bonneville on a record attempt....I dont believe they back off for anything.
Hopefully this drivel will at least get you a bump to the top and James or Herm will give you a good answer.
Good Luck!

 

[SAJ]

Vince,
I have a Snyder 5.5 to 1 head. The overbore gives it about 6:1, I think from memory. I mistakenly said I have +0.100 bores. It is actually 4 inch and 0.125 inch overbore. A bit more than 3.5 litre or plus 6.6% upping the compression pressures.
What is a reasonable max advance? I have read several others use 28 deg.
I am running 28 deg on my wife's Tudor too with a similar engine I built, using babbitt.
I don't want to wreck this one too.
SAJ in NZ
I appreciate your advice

 

[Bob Bidonde]

The cracks in the rod bearings appear to be from fatigue. For fatigue to occur, there must be an alternating tension field in the bearing. Causes for the tension field may be:
> Failure of the Babbitt to adhere to the rod allowing its movement under load;
> Understrength Babbitt material allowing it to repeatedly yield;
> Pocket within the Babbitt;
> Excessively high pressure loading in the cylinder (power stroke), but this is not likely as not all of the rods have cracked bearings;
> Rod bearing not normal to the wrist pin perhaps due to a bent rod or out of alignment boring of the rod bearing.

It is wise to replace the rods with cracked bearings.

 

[H. L. Chauvin]

Hi SAJ,

In trying to get this over with, with heartfelt compassion, here is what I would try to do:

1. Something tells me that there are gentlemen on this Forum who trust the expert opinions of those few today who pour Babbitt often who could perform a "hands-on" inspection for the possible "root(s)" of this particular problem.

2. Rather than waste valuable time guessing, I would try to ship the connection rods to this Babbitt expert for peace of mind and be done.

3. In my humble opinion, from thousands of miles away, not being able to "see", "hear" and "touch" this sort of problem, not being able to quickly communicate by phone, most vehicle Forums opinions are just mere guesses for unresolved problems almost like playing BINGO ...... nobody knows whose response will win.

4. It is almost like writing a letter to a Doctor in Iceland thousands of miles away trying to ask what kind of surgery one needs for his back pain.

5. Show me a perfectionist laying bricks and after laying bricks for a week, 1 or 2 will be a little out of level ..... Babbitt is not much different ..... professional liability insurance companies are fully aware of this human event and their policies get exercised often today.

6. An individual's peace of mind to an unknown cause is a great thing that no money can buy.

Just sincerely hopes this helps.

 

[Kohnke Rebabbitting]

Mr. SAJ, Take a knife and take out the fractured pieces in the tops of the rods, and take pictures of the rod, and the back of the babbitt pieces.

Use your flash if you can.

You have Aluminum impregnated in your main babbitt.

The mains may, or may not be tin base, but the rods look like lead babbitt?

Your, .001-50 clearance is where you want to be on the rods.

Are these rods the ones that came with your rebuild?

Herm.

 

[Kevin in NJ]

Lead babbitt scraps much different then the harder tin babbitt.

Try some light scraping on the rod and the mains in an out of the way place.

Also try pressing the edges of the mains in the block. If any oil is squeezing out then the babbitt was not peened right. Hard to be sure in the pictures, but one looks like it could have a bit of separation between the block and the babbitt.

 

[H. L. Chauvin]

Mr. Herm's response no. 9 appears to be as effective as a quick response to a solemn prayer calling for Babbitt Help.

 

[Tom Wesenberg]

I also think you had too much advance. That's the advance I use with my totally stock engine with only 50 lbs. compression. I would stop advancing the spark as soon as the engine no longer picks up speed or power, and not go until just before you hear detonation.

 

[SAJ]

Wow, this is like waking up on Christmas morning to a bed covered in presents!
Answering as the advice came:
Rex A Lott. Thanks. Jim Brierly says he used the same old babbitt over and over in his racer for many years, and as you say did not back off to preserve it.
Herm has replied as you suggest and I will be addressing his suggestions today.
HERM. Once again eagle eyes! I will do as you say and remove the loose piece. I will pull the pistons out too and see if No3 is galled up near the lands. It locked up once at 4000 miles and seemed fine when cooled but i only used a bore scope and never took it out. That is the only Ally in the engine. I will put the babbitt under my metallurgists microscope and peer at it too and try a Barcol hardness test etc. The rods are as supplied by Schwalms and I have not had this engine apart since rebuilt by them, except to fix a burnt valve in no3
BoB Bidonde. As always good advice from you. I will analyse the babbitt for lead and have a poke at it under the microscope too. I think the rods are straight. When I pull them out I will clock them up as best I can in my mill. I believe .001 across the small end for parallelism ans twist is specified. I should see this easily. The rods are being replaced too with new ones and shells fro Snyders.
H.L. thanks again. I had to show my wife your amusing similes and metaphors. Good advice hidden amongst it too! Shipping the rods is a good idea, since I will not be re-using them. But it seems a bit much to ask someone to comment on another's work - unless I sent them to Ora Landis.
Kevin. All babbit is tight enough not to show oil squish. But it looks like one piece on a cracked rod may flick off with a knife. I will try this and examine the tinning. As stated I will examine the hardness too. I have a Barcol hardness tester (impressor type) which may give meaningful readings.
Tom W. I will certainly consider reducing max timing in future. But as noted, max power on several dyno sites with engines similar to mine all use 28 deg. That is the max I go to and retard on hills from there. But with engine slowing due to the gradient, it is hard to retard until power drops off, because how do you tell? On uphills I retard anyway, and like MikeK said once, I have worn the notches off my quadrant by constant adjusting. I sit at 28 deg only on the flat and minor gradients where there is still acceleration in hand in O/D top. I do not run at 28 deg all the time.
I am nervous too about burning another valve and monitor my EGT. It can get to 800 deg C (1470F) up long hills when retarded too much, and this happens quickly. I also open the GAV on long pulls a tiny bit, but see no change in exhaut gas temp with mixture, despite what learned books say.
Thanks again to all
SAJ in NZ

 

[SAJ]

I have now removed the head, measured the bore, peeled off some rod babbitt and measured the hardness against some #3 babbitt in a puddling stick, and put it under a microscope.
Herm, under the scope middle main does not look like imbedment (pic attached). At 50 and 100 magnification I see tiny craters and polished high spots all looking like babbit. No dirt except in one deep scratch that looks like it was there from the beginning. But I do see light shiny particles on the inlet valve tops, that look like ally and suggest transient detonation. Pics attached. Main cap too big to go under my metallurgical microscope, so put it under a biological one and took a pic down the lense with my phone!
Two pistons have lost carbon against the bore remote from the valves. Maybe due to water ingestion from my low-slung air filter. RHD cars have little room for a good sized filter, unless hung down or extended way up the front past the oil filter spin-on. I "won" the wooden spoon on our recent rally for drowning the car in a creek so it would not restart and may have got water into the carb., since one plug was very clean when I dried them out. But there was no suggestion of a hydraulic-ed motor.
Piston 3 has light scuffing most of the way down the skirt (this one locked up at 4000 miles as mentioned) and the others have minor traces too, I imagine from the overheating episode when an "expert" reset my timing very retarded and I drove it home down the motorway.
Bores are unmarked except some very faint, unmeasurable lines where #3 scuffed. Piston skirt clearances are 0.003 at the skirts (Bores .004 under 4 inches 1.e 3.9960, pistons 0.006 to 0.007 under 4 inches. the smaller piston is in the tighter bore). Checked the mike with its test bar and another mike. Sure these are correct. Used a DTI bore Gauge, zeroed on the mike's 4 inch standard test bar. Measured 10 times because I didn't believe under 4 inch bores at first.
Barcol hardness of removed babbitt 15 units falling to zero as the needle penetrated. Barcol of the grade 3 babbitt 20 falling to about 10 as it penetrated. Unknown Babbitt in an old X section rod read zero - to soft to measure.
Will analyse babbit for lead later.
Pics attached. With flash on cracked babbitt as Herm asked.
I think new harder rod shells and less spark advance will be the answer on this engine.
And less spark and more gentle babying will prevent the same thing on our Tudor.
I recall several people who wanted to try my car lugging it to my horror, causing me tofix the max possible advance at 28 deg. Some drove my car while I tested theirs, so I don't know what they did in my car.
Thanks again for all the help and opinions.
More advice very welcome
SAJ in NZ

 

[Tom Wesenberg]

It looks like it was running rich and number one looks like it's wet, as though it's using oil or wasn't firing.

 

[SAJ]

Good observations Tom. I was trying to run it richer due to an earlier burnt exhaust valve. It got 22 mpg and used 500 ml of oil in a recent 3000 mile run.
And I may have idled it for a long period right before pulling it down while diagnosing the engine. The plugs were a light tan during plug chops at speed, but ran a bit too rich at idle, for easier cold starting in the cold South Island where we were.
Thanks for the reply. I will investigate further.
What did you think about the shiny particles on the exhaust valve. They are not globules but I can only think they are aluminium, yet there seems to be nothing missing from the pistons- no erosion I can see anyway. Thinking about detonation here.
SAJ in NZ

 

[Rex_A_Lott]

I like your approach and I'd like to say Thanks for posting the pics. I think you are lucky you took it apart before any big damage was done.
I'm curious where you normally run your GAV? I'm with Tom, its looks rich. If you normally run with it shut, maybe the air filter is causing it to run rich.
Also curious what type fuel you normally run, and if you add anything to it?
Hopefully you will get some good comments from Herm.
Good Luck!

 

[SAJ]

Rex A Lott, I really enjoy the technical aspects of these old cars . Your comment about my air filter reminded me we did thousands of miles along dirt roads and my large paper air cleaner got really dirty. I washed it with soap and hot water in a motel at one point - not a good thing but the best I could do at the time.
Carb is a B model, idle jet passe 50 cc water per minute and GAV at 1/4 turn open gives white plugs and 1/2 turn light tan. I was running a hair over 1/2 turn open on this run. Fuel is just 96 RON unleaded, no additives. I used to manufacture RedEx upper cylonder lube, so I suppose I should be using this!
I caught the burnt valve at 4000 miled without other damage and got lucky this time as well. But My training has all been in observation of cause and effect and I have been doing this a long time!
SAJ in NZ

 

[Tom Wesenberg]

If you get a paper filter wet it can close up the pores, especially if you start the engine with the wet filter. I'd buy a new filter, or buy one that is made to be washed and reused.

 

[SAJ]

Tom. You are dead right. I used to manufacture GUD brand air and oil filters so I should know better! But it does explain the black valves
SAJ in NZ

 

[James Rogers]

I believe the rod with the broken babitt was never tinned properly. This is why the babbitt fractured and fell out. If the tinning is done correctly, it will not just fall away from the rod. Once tinned the babbitt is bonded to the steel of the rod and must be melted out to remove it. These rods were doomed from the start. If you ran too much timing, you just accelerated the failure. #3 was fitted too close to begin with.