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think my engine blew up today


H20doctor

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so i was working on 610 today and installed some new pugs , wires , new distributor, a new weber 32/36, i changed the oil and got it all tuned up , point gap , and timing spot on.... start it up go for a ride get it up to 50 mph , turn around come home shut it of.... I go to start it 3 hrs later and there is a massive Knocking noise from the engine.. cank..cank..cank..cank..cank...cank... 

 so i shut it off.... its a L20 B with who knows how many miles .... its sat in my barn for 6 years and not driven or started... In the last year i have only driven it 2x.... there is no smoke from the tail pipe when it runs... So bad Crank ? Cracked Piston ? what say you 

 

So if i pull the head what should i look for? , Or just pull the oil pan and look for chunks of metal ..?. 

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i will pull the plugs wed and see what happens... also i have a new filter for my 620 truck , and i will put it on ... I have a back up engine its a L20 with 0nly 35,000 miles on it , But i really dont want to do a motor swap cause its such a pain in the ass 

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Diag. 

 

Pull plug wires, 1 at a time, while running. Called a power balance test. 

The condition will either change or not. The cylinder that has no change is the problem . 

 

With a bad rod/crank bearing you won't need much more testing. Just inspecting. 

 

Check the basics next. 

Condition of plugs. Rich condition is a concern. Plugs will be dark and/or wet. 

Oil in coolant/coolant in water. Oil and coolant levels. 

Oil condition. Metal in oil? Fuel in oil? Place a magnet on oil plug head after its loose and remove by hand. 

 

If the last is suspect-the pan should be removed for further diag. If you're removing the pan may as well install your KNOWN, good motor. 

 

GL. Your post is a little vague so helping is a little hard. 

 

Cracked piston? No. You'd be seized. 

Hell, you may just be hearing a set of valves that need to be adjusted. 

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start it up go for a ride get it up to 50 mph , turn around come home shut it of.... I go to start it 3 hrs later and there is a massive Knocking noise from the engine..

Rod bearings don't go bad sitting for 3 hours. You would have heard them while coming home. Check your most recent work done on it. Oil level? Distributor replaced? is it loose or broken? Broken or loose spark plug in the hole? Plug wire off, coil wire off? Points?

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Rod bearings don't go bad sitting for 3 hours. You would have heard them while coming home. Check your most recent work done on it. Oil level? Distributor replaced? is it loose or broken? Broken or loose spark plug in the hole? Plug wire off, coil wire off? Points?

oil level fine, distrib is new all good, belts are new, alternator fine , noise is coming from the engine, checked the plugs ngkbp6es all new all fine , the noise has to be a crank Issue or bearing 

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So bad Crank ? Cracked Piston ?

Bad owner!!!!!!!

 

open valve cover and ck for any obvious. like lash pad fell out or cam broke.

Fuel pump arm has no spacer?

 

call Framk in 41st in Everett and find another motor if you think this is bad. But 3 hr s of fine to then just Bad engine is hard to believe( guess it can happen)

But these are simple cars for simple people and a go getter like you should have it fixed in no time

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So bad Crank ? Cracked Piston ?

Bad owner!!!!!!!

 

open valve cover and ck for any obvious. like lash pad fell out or cam broke.

Fuel pump arm has no spacer?

 

call Framk in 41st in Everett and find another motor if you think this is bad. But 3 hr s of fine to then just Bad engine is hard to believe( guess it can happen)

But these are simple cars for simple people and a go getter like you should have it fixed in no time

Valve cover is fine, towers and cam look fine , springs and retainer clips all there ..I dont post much here do to people being .......... , ive owned datsuns since 1984...So this isnt my first issue with a L20

 

 

why am i a Bad owner ? i cant predict a engine .... im just asking for advice , and trouble shooting my car ... you choose to opt in or opt out here ...

So i did the spark plug thing , no change in noise .... the last time i heard this noise was on my truck , the bolts came Loose on the fly wheel and the flywheel was the culprit..

I am just going to pull the engine and throw in my back up , Im taking down my head to autosport this week and have them do a port and polish with a valve job.. Im prob going to throw on a shorty header also and re do the exhaust...

anyone have a shorty for a 610 ? if not then i will order one from topend performance for 190.00

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for the record I'm not trying to be a douchebag I'm just frustrated as I'm trying to get this car ready for a car show and possibly have it sold but now I have to do a complete motor swap and I dont want to do it... putting money into a car that's 20 some years old that I'm not going to recoup financially

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All I can say maybe mount is loose and your not catching something simple

Like I said if no oil pressure might cause this but if you cked under the hood and everything looked fine.

 

pull the filter and crank the motor over if pressure it will squirt out(if not mechanical gauge). I heard of oil filters that valve relief getting stuck and stops pressure(Frams).

 

But if you think its a block issue then hell finds a cheap L20 and bolt it in and sell it.

 

 

a rust free 610 is cool and somebody might pay more money. But as for L motor stuff I have given enough away to build motors.

Terri at Auosport is good but I dont think one will recoup money from datsuns anyway as its a Love thing for the commited ones.

 

20year old has nothing to do with it

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Compression and leakdown will do nothing to diagnose bad lower end.

True.

 

If an exhaust valve seat (the hot ones)fell out it would show almost zero compression.

 

Hainz also suggested a lash pad fell out. That would make noise. Not rod noise but depends if you have ever blown a rod before and know the difference.

 

Worth pulling valve cover off and cranking the engine. Look for a valve that is not closing all the way. Seat out.

 

Worth pulling all the plugs and looking for aluminum flakes.

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