#4 Piston Engine Mystery - Help Please

[cw]

My Son and I own a 1929 82A pickup. We replaced the worn out 30A block with a 32B block, winfield head, brinley 3/4 cam, balanced crank, ansen down draft, demon carb and mallory centrifugal advance distributor, mallory coil - professionally built.

Now the mystery - at about 500 miles, driving from a car show the #4 piston fails (rod stripped of babbit, damage to piston skirt). Sounds like a cement mixer.

This has happened now 4 times!

The engine builder has been a real champ, standing behind his work, but the beautiful days with my Son end up in disappointment. (not to mention tow fees, pulling the engine, waiting for parts and the spector of engine failure each outing),

I really need some help.
Any ideas welcome.

[1931 flamingo]

Crank bent,brgs offset, bent rod,piston pin offset, ????????
Paul in CT

[BRENT in 10-uh-C]

Paul offers some good things to check but based on the package of parts, ...and the fact that you say this is the 4th time, I think the problem may be with the combination.

Generally speaking, with a high compression head and a centrifugal distributor, the possibility of detonation is VERY likely. Adding to the fact of a heavy C/W crankshaft and plenty of cam & fuel to be able to smoothly turn up the RPMs, I think it is very possible you are 'hammering out' the babbitt of the rods from detonation. (...this would also explain the piston skirt damage as the piston is trying to rock.) Once the rod-to-journal clearance opens from the excessively high pressure caused by detonation, this allows the rod to 'hammer' on the crankshaft some which as it does just allows it to hammer harder as the clearances grow until the babbit is gone.

[Rowdy]

My thought is the #4 rod throw is offset. Most likely cause in my opinion. Rod

[cw]

thanks you guys are awesome.

We have replaced the block (twice), all 4 pistons/rods/rings (3 times) and oil pump. The only things in common across all occurances are the head, intake, distributor, pan, tray, crank and cam.

If it were detonation, would we see evidence on the piston head?
Since it is always #4 could it be the crank/journal on #4?
Could it always be #4 because oil starvation on the last cylinder?

I appreciate guidance on a course of action (short of having my head examined - again ;-)... Chris

[1931 flamingo]

Sponsored Links (Register now to hide all advertisements)

CW, yor last msg and what Bert says, CRANK and/or head seem to be common if you used up 3 blocks. JMO
Paul in CT

[Old182]

Strange that the engine would detonate to the extent of catastrophic damage only on #4 every time. Brent has a good point regarding hammering out the babbitt, and I agree with checking all the mechanical dimensions, but you may want to check oil supply to that cylinder and flywheel/clutch balance as well. I'm not an engine expert, but if the flywheel/clutch assembly is out of balance, wouldn't that ~70 lb. wobbling mass tend to tear up the back end of the engine? Just a thought. Regarding the detonation issue, Model As ran on 60-70 octane gasoline when new; 87 (R+M)/2 should allow for a lot of compression ratio over the stock 4.2:1 before detonation (assuming timing is not severely advanced). I've attached a pic of a piston from a NYS Trooper engine that suffered severe detonation. Note the "pock" marks from the pressure spikes during detonation - look for these on what's left of your piston(s). It's not uncommon to find these marks on pistons from engines that have been flogged, but the big hole is what happens when you keep your foot in it. The second piston is from a hot rod boat engine that experienced detonation in the first (and last!) few seconds of its life. It got very hot and melted the forging; I assume your engine didn't go quite that far.

[Frank Miller]

Just out of curiosity did you check your piston to head clearance? I do not think this is it but the more stuff you have measured the easier it is to track it down.

[Jim Brierley]

I always allow more than recommended piston clearance, .0035" minimum. It is common for #4 to run hotter than the others, check the water passages for blockage. Also you might try retarding the spark some, 26 max degrees and see how that works.

[82ndscotty]

timing gear covers are not the same. the pin on the a is top dead center. the pin on the b is 19 degrees b/4 top dead center. the advance curves were different for the two engines a shot in the dark, but should be checked. lol Scotty

[Chris in CT]

Hi CW, I'm inclined to go along with some of the suggestions that #4 is oil-starved. Is there any evidence that the splash pan at #4 is not getting enough oil or that the oil is not being contained in the #4 depression? Good Luck with this one!!

[skip]

Go back to a well assembled bone stock engine. Four times? Your kidding me. You running a NASCAR, 'rebuild after each two hour race', engine? Sorry. I have no good ideas. Go with BRENT in 10-uh-C

skip.

[Richard in Anaheim CA]

Referring to Brent's detonation diagnosis.

I broke off the top of #4 piston for no apparent reason. I had encountered severe detonation only occasionally and immediately cut back on the throttle and the advance. This was over a period of years.


When I was timing the engine with a timing light and for no reason clipped the light on #4 since it should be the same as #1. The distributor cam #4 lobe was 10* more advanced than the other 3 cylinders.

I didn't know I cound throw anything that far.

Richard
Anaheim CA

[AL in NY]

CW, with all the performance mods you did, are you still using the dipper oiling system, or have you upgraded to full pressure. I would go along with Chris and the others who have stated that it's oil starvation on #4 cylinder. If you have full pressure, I would check the oil pump.

[James Rogers]

Originally Posted by cw

thanks you guys are awesome.

We have replaced the block (twice), all 4 pistons/rods/rings (3 times) and oil pump. The only things in common across all occurances are the head, intake, distributor, pan, tray, crank and cam.

If it were detonation, would we see evidence on the piston head?
Since it is always #4 could it be the crank/journal on #4?
Could it always be #4 because oil starvation on the last cylinder?

I appreciate guidance on a course of action (short of having my head examined - again ;-)... Chris

You need to have the crank checked on the #4 journal. Sounds like it is ground wrong or the crank is bent at that journal. The only other suggestion I would have is to check the distributor and the point cam for any problems. Your problem is not in the block, pistons or, rods since you have changed these so many times. If the problem is not the crank, my next suspect would be driver/operator error of some type.

Just an opinion.

[BRENT in 10-uh-C]

Originally Posted by Chris in CT

Hi CW, I'm inclined to go along with some of the suggestions that #4 is oil-starved. Is there any evidence that the splash pan at #4 is not getting enough oil or that the oil is not being contained in the #4 depression? Good Luck with this one!!

Hey Chris, if none of the other 3 rods are experiencing this phenominon one can only assume there is adequate oil in those tray dippers. Thus if those 3 continue to get plenty of oil, then wouldn't the excessive amount of oil automatically overflow/drain into the 4th rod dipper area just due to the inclination of the engine? I would think so.

I think Al poses a good question as to whether someone has blocked off the rod scoop however a Model T did not use a scoop or have any holes for the oil to be scooped into and they ran for many thousands of miles getting their oil from the edge of the rod.

I have written more thoughts on #10 of the other post asking this same question.

.

[Rowdy]

Might be a small detail, but has the dipper tray been thuroughly checked for holes. Still putting my money on the crank as the problem. Rod

[BRENT in 10-uh-C]

Originally Posted by Rowdy

Might be a small detail, but has the dipper tray been thuroughly checked for holes. Still putting my money on the crank as the problem. Rod

Again, I realize that "assumptions cause problems" but assuming the oil pump is even marginally operable, the Model A/B pump moves a tremendous amount of oil. Even when the rod slams into the oil in the dipper tray and displaces it, there is so much oil that is flowing that it is replenished almost instantaniously. I have known of engines that had holes in the dipper tray that you could seemingly stick your finger through and the engines have lived for years that way. I honestly hope the Wiggins' do not follow-up to all of our armchair advice and say "What's a dipper tray and where does it go?"

Exactly what are you suspecting is wrong about the crankshaft?

.

[Rowdy]

I am suspecting it was ground off center. I realize that .015 is all it could be off using .030 as the max which they should be turned, but if it is on the right part of the the throw it could be raising the compression in that cyl. contributing to the predetonation problem. Especially if it has a higher compession ratio head, which sounds like it likely has. Could be several other factors also. Hard to make many assumptions from hundreds of miles away. Rod

[d.j. moordigian]

OK....leaking needle an seat in the carb, peculation of the fuel after shutting the
engine down, hydrostatic locking of the #4 cyl. Electric fuel pump? Really not
much info on the rod and piston, what does it look like, photos?

Dudley