i bent a connecting rod lol

[datzenmike]

46 minutes ago, nathan.is.an.idiot12312 said:

i wont know if i spun a bearing until i drop the pan but a blown ring would explain the knocking with piston slap 

 

Rings, broken or not, don't knock. If broken they may score the cylinder wall and the may break the piston ring lands. As for rod bearings, lack of lubrication can increase the usual clearance of between 0.001" to 0.002" to the point that the oil film can't be maintained. When the cylinder fires it drives the rod into the bearing and pounds it flatter and thinner, even squashing bearing material out to the sides and increasing the gap even more. When thin enough (I've cut myself on a rod bearing as thin as a razor) one bearing shell rides up onto the other and blocks the oil from the crankshaft. Very soon the bearing welds to the crankshaft and spins with it or welds to the rod and spins with it. With no oil to cool it and more than enough HP to turn it, it's a matter of seconds till something breaks. 

 

If yours is just knocking it probably hasn't spun yet. The crankshaft is likely toast but can be turned down and an over size bearing used. The rod might be blue from the heat and garbage too. Bent? I doubt it.

 

I don't think the A series engines used sleeves. The cylinder must have been terribly damaged to mill it out and fit a sleeve into it. Most would just throw away and get another block.

[Stoffregen Motorsports]

It is not uncommon for a rod knock to be simply loose/worn out bearings with no damage to the crank.

 

A motors were not sleeved from the factory, and even most shops wouldn't go through the trouble of sleeving one.

 

Given what we know (or at least what we've been told) - it's been run low on oil multiple times. It has overheated to the point that it doesn't run. Both of these are a death sentence for any motor.

 

FWIW, the oil light is not there to tell you when to add oil.

[datzenmike]

34 minutes ago, Stoffregen Motorsports said:

FWIW, the oil light is not there to tell you when to add oil.

 

[nathan.is.an.idiot12312]

UPDATE this past week i was at my grandparents house in utah, so the datsun sat. 

 

i got home and decided to run her again, there was absolutely no knock, which is funny cause it was knocking when the problem first arose.

but she sounded healthy but she was definitely down a cylinder (cylinder two the most likely culprit) sounded like she had a big cam at idle and sounded like a lawn mower under load. significant loss of power(consistent not progressive) so i did an oil change and i took her out for an drive and drove 58 miles on 2 gallons of gas nonstop with no problems (never breaking 50mph)

 

by the way i did a crap load of digging and sourced cheap used/old stock crate datsun a14 engines for sub $500 some with transmissions attached  (not including shipping costs) so atp im probably just gonna run her till she blows or until i get the money for a new engine because a rebuild now costs far more than a new engine. 

 

but yeah just blew a ring (dead cylinder)

 

would be really nice to know what the knocking was when it first happened though. 

 

On 3/9/2024 at 9:49 AM, Stoffregen Motorsports said:

 

FWIW, the oil light is not there to tell you when to add oil.

lol i know dont worry😂 i have forgotten to check the stick a time or two in the past and with how fast i burn oil... lets just say my actions and habits had their consequences😂

Edited March 15 by nathan.is.an.idiot12312

[nathan.is.an.idiot12312]

and im gatekeeping my sources for those engines so please dont ask me 😀 if you want em you gotta do the searching (it took me hours)

[Stoffregen Motorsports]

On 3/15/2024 at 4:16 AM, nathan.is.an.idiot12312 said:

and im gatekeeping my sources for those engines so please dont ask me 😀 if you want em you gotta do the searching (it took me hours)

Wow! Way to reciprocate.

[datzenmike]

What's in a (user) name?

[nathan.is.an.idiot12312]

11 hours ago, Stoffregen Motorsports said:

Wow! Way to reciprocate.

 

haha  just dont want them to be bought up and sold off for parts because theres only 20 of them and with parts like the head and block alone are worth about $1000 each, these engines are being put away for crazy steals. if ya really want one then dm me and ill send you a link to the site but you gotta swear to me that you will only buy one or two and not share the info because its only fair to the people like me doing hours and hours of scrounging the internet for a reliable engine source that its kept locked up.

 

ya catch my drift?

Edited March 18 by nathan.is.an.idiot12312

[nathan.is.an.idiot12312]

ok also did a compression test  for some confirmation and the results are: 

*P1: 165psi

*P2: 45psi

*P3: 170psi

*P4: 167

 

                                                      (*P: piston)

 

compression test when i first bought the car back in september of 23' resulted in those same number but with piston 2 reading 159 psi

thus confirming my educated guess that i blew a piston ring and cylinder two is pretty much gone.

 

but so far she's ran healthy on 3 cylinders for the past 100 or so miles which is a huge testament to the reliability of these A series engines

im probably making a whopping total of 50-60 horsepower from this a15 now on 3 cylinders 

 

my mechanic told me that if i can get the engine out easily enough, i should pull the pan off and re ring piston 2 and see if i can get a little bit more out of her, and i wont have to be as precise cause shes getting a new engine no matter what, and the cylinder wall is already most likely in horrible condition. and maybe ill turbo her and blow up my already blown a15 within a day who knows lol. im just gonna have fun with this engine while i can

 

also my head (large oval ports by the way) is still in great condition minus the scoring on the top of combustion chamber two which can definitely be ground back smooth so i might part her out on here see it if can get like $650 bucks for it once i get a new engine lol.

 

okay its late and i wanna play gran turismo A spec. goodnight 

 

 

[datzenmike]

Piston ring lands may be broken also.

[nathan.is.an.idiot12312]

11 hours ago, datzenmike said:

Piston ring lands may be broken also.

hope not lol that would suck

[nathan.is.an.idiot12312]

just a little update. 

 

i have driven the car 800-900 miles without a significant problem. 

fuel economy is good.

no coolant leaks at all. 

oil consumption hasnt increased much if not at all. 

 

fires up for me just fine every morning

changed the oil filter.

 

she does get a little hot when i idle in traffic, but cools down back to normal temps almost instantly when i get moving again. i assume this is just because my cooling fan is old.

 

its funny, on 3 cylinders this car has functioned more reliably without a problem for longer than it ever has within the time i have owned it. 

 

but thats probably because i think i had finally gotten all of the major issues fixed and then it decided to break a ring.

 

car is still daily driven (i drive it a lot too)

 

again a huge testament to the persistence and reliability of the A series engines, i didnt expect this engine to go any more than 1000 miles before total failure, let alone 800-900 miles with absolutely no issues.

 

(i do plan on updating tis thread with the condition of car until get a new engine in her)

 

 

[datzenmike]

1 hour ago, nathan.is.an.idiot12312 said:

she does get a little hot when i idle in traffic, but cools down back to normal temps almost instantly when i get moving again. i assume this is just because my cooling fan is old.

 

 

 

but thats probably because i think i had finally gotten all of the major issues fixed and then it decided to break a ring.

 

 

 

Vehicle movement will push air through the radiator and increase cooling. I have an electric fan and it's not on when driving. Might come on at lights.

 

Broken ring is only a maybe till you take it apart.

 

 

What was the compression on the bad cylinder???? If near zero you might remove the two push rods so the valves don't open and deactivate the cylinder. This will stop the oil burning. If there is a marked decrease in power put them back as that cylinder is doing something.

[nathan.is.an.idiot12312]

On 4/4/2024 at 12:25 PM, datzenmike said:

 

Vehicle movement will push air through the radiator and increase cooling. I have an electric fan and it's not on when driving. Might come on at lights.

 

Broken ring is only a maybe till you take it apart.

 

 

What was the compression on the bad cylinder???? If near zero you might remove the two push rods so the valves don't open and deactivate the cylinder. This will stop the oil burning. If there is a marked decrease in power put them back as that cylinder is doing something.

compression is 30psi in cylinder 2

 

i will mention that i already tried removing the pushrods on cylinder 2 but that induced a heavy knocking while the engine was running and increaced vibration, so i immediately put them back in

 

and again i assume that shes lost the ring because it looked exactly as if a ring had broke off and got sucked into the combustion chamber then repeatedly smashed against the top of the head until exiting the exhaust valve, which would also explain the knocking i was hearing from the engine when it first happened coming from the ring particles geting thrown into the head at the top of every stroke.

 

%90 sure about this, if i had an audio clip of it running when i first blewthe ring and showed it im sure you would agree.

 

ive been watching a lot of videos on broken rings and it just all adds up

[nathan.is.an.idiot12312]

the other pistons measure in at about 165psi on average between the three not differing any more than 10psi 

 

 

 

[datzenmike]

On 4/4/2024 at 11:12 AM, nathan.is.an.idiot12312 said:

 

 

i have driven the car 800-900 miles without a significant problem. 

fuel economy is good.

no coolant leaks at all. 

oil consumption hasnt increased much if not at all. 

 

  

 

 

Which earlier you said was 3 qts. per tank full of gas. This is an insane amount of oil! A qt. every 100 miles? There would be a huge blue cloud following you down the road.

 

Pull the engine out, take the oil pan off, and look at #2 rod bearing. If damaged it will be obvious. If pounded out of shape it will throw huge amounts of oil on the cylinder walls, more than the oil ring can control and it will get up into the cylinders. The extra oil thrown around will be sucked out the block vent into the PCV valve and distributed to the other cylinders, oiling them up.

 

If the rod bearing is bad, it's almost certain the crankshaft journal is also damaged and a new rod bearing won't close up the clearances needed. Normally the clearance is 1 to 2 thousandths of an inch about half the thickness of newspaper. I've seen rod bearings pounded till they are razor thin and still run, but not quietly. 

[Stoffregen Motorsports]

A ring won't get sucked into the combustion chamber unless the piston broke too. Are there dark vertical scratches in the cylinder wall?

[datzenmike]

Also would not explain the knocking you mentioned. Excessive bearing clearance prevents rod riding on a cushion of oil like it should. Instead the oil just gets pushed out. Piston hammers rod bearing down onto crank, metal to metal accelerating the damage. 

[Stoffregen Motorsports]

More likely that something fell down the intake, or into a spark plug hole. Bounced around and crushed the ring land on the piston, causing the ring to stick, which means no compression.

[nathan.is.an.idiot12312]

well in that case i would probably have to guess something got sucked in through the intake and:

On 4/10/2024 at 12:04 PM, Stoffregen Motorsports said:

More likely that something fell down the intake, or into a spark plug hole. Bounced around and crushed the ring land on the piston, causing the ring to stick, which means no compression.

and again the engine makes almost no abnormal noises (other than mild lifter noise) now and only really puffs blue smoke when im in higher revs

 

and im not trying to seem ignorant by not removing the pan, its because withe the way this car is designed, i would have to completely pull the entire crossmember and roll bar from underneath the car or pull the engine to remove the oil pan, and i just dont have that kind of time at the moment

 

and i would totally pull the head off again and do a reevaluation of the pistons and cylinders under better lighting and take better pictures but again time is an issue

 

when i took the head off last time it was near midnight i was in a sleepy haze and couldnt think totally straight and so i ended up with terrible pictures off a half decent camera i had lying around and didnt think to grab my phone or a good light which is entirely my fault but besides the point.

[datzenmike]

Back to basics. If the piston was damaged you would have seen something when the head was off. The land above the top ring is fairly thick, so if a piece is missing the damage is much worse. Not saying the rings below are not broken but it takes a lot over over heating to do this. There will still be some compression, enough to notice a change when this cylinder was deactivated.

 

I keep asking if you checked the valve lash or clearance and can't remember your answer. When the head was off were the valves fully closed? Did you take the valves from the bad cylinder out and look at the condition of the valve faces and seats???

[Stoffregen Motorsports]

We did see some damage when the head was off. Remember all those marks in the chamber? Unless that head was on a different motor, the piston was probably damaged too.

 

Sometimes, often really, something bouncing around in the chamber can get spit out the exhaust.

[nathan.is.an.idiot12312]

On 4/16/2024 at 5:55 AM, datzenmike said:

Back to basics. If the piston was damaged you would have seen something when the head was off. The land above the top ring is fairly thick, so if a piece is missing the damage is much worse. Not saying the rings below are not broken but it takes a lot over over heating to do this. There will still be some compression, enough to notice a change when this cylinder was deactivated.

 

I keep asking if you checked the valve lash or clearance and can't remember your answer. When the head was off were the valves fully closed? Did you take the valves from the bad cylinder out and look at the condition of the valve faces and seats???

the top of the piston was visibly scratched and damaged yes 

 

and yest all the valves fully closed when i pulled the head. Re-lashing the valves was one of the first things i did to the car when i bought it.

didnt check the seats though