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L20b power loss/valve problems?


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#1 MapleNuts

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Posted 09 May 2016 - 01:08 PM

hello, my 75 610 goon all of a sudden lost a lot of power and sorta sound a little like its missing today, and i'm looking for some advice on what the issue could be or my next plan of action to solve this.

 

A little background on what is currently wrong with the engine, it's been backfiring out the exhaust a little on idle, and and a lot on deceleration.  And more recently it is smoking out the exhaust and smells and looks like it could be burning oil. I advanced the timing a day or two ago to try to see if i could get the car to stop back firing, it ran fine but still backfired. And on my way home from school today i parked it and when i started it back up it started running like crap. 

 

All the cylinders are firing. I've cleaned my cap and dizzy, checked leads, played around with the timing, played with the carbs fuel mixture and even checked for vacuum leaks.

 

I don't know what the heck could be wrong with it, my best guess is it needs some sort of valve adjustment which i don't even know how to do.

 

Thanks Dastun people smarter than me!



#2 datzenmike

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Posted 09 May 2016 - 01:35 PM

Always good to have proper valve clearance.... http://community.rat...lve-adjustment/

 

Then get it timed.

 

 

 

Is it running hot?

Is it using coolant? need topping up?

Is one of the plugs much more cleaner than the others?

 

 

You said carbs, unless you meant carb's. Do you have a factory carb or... what? Anything else that's been changed?


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#3 MapleNuts

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Posted 09 May 2016 - 02:13 PM

It seems to be running a little hot, I can't really tell due to no temp gauge with the single weber 32/36. Could just be my imagination.

don't know what topping up is, unless you're asking if the radiator needs to be topped off with fluid, which it does not.(no coolant in my oil)

just checked the plugs. there is only 4k on them and they all seem pretty black, but i don't have too much experience with checking plugs. However cyl 4's plug had gunk all over it.

 

Only other things that have been changed is the egr delete. The muffler fell off, and once i put it back on after it had been off for week, the car started smoking, I don't think that is related to the smoking though?



#4 datzenmike

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Posted 09 May 2016 - 02:20 PM

Clean the plugs first, this will likely clear the problem up for a while.

 

Is the choke opening once the car is warmed up?


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#5 MapleNuts

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Posted 09 May 2016 - 02:31 PM

Thanks will try that! what do you recommend i gap the spark plugs to? couldnt find a clear answer, also the engine seems to be running better at a little more advanced timing around 17 if that makes a difference.(that's without adjusting the valves yet)

 

I believe it is opening but ill double check later.



#6 datzenmike

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Posted 09 May 2016 - 02:48 PM

Set the valves and clean the plugs.


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#7 MapleNuts

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Posted 09 May 2016 - 03:01 PM

Thanks again mike, you 're awesome



#8 datzenmike

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Posted 09 May 2016 - 06:04 PM

A stuck choke (or flooding) will cut engine power and foul the plugs... which will also cut power. Over rich, will carbon up the combustion chamber and you may notice black smoke coming out the exhaust pipe..


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#9 banzai510(hainz)

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Posted 10 May 2016 - 06:17 AM

whos 510 wagon on the avatar photo? I seen this car in Covington.

 

PS sounds like you cant handle a L motor.

I would ck the valave lash as a maybe a lash pad fell out.

 

If points ignition I would ck that especially if you put a different coil in there.

Get a timming light. and time the car and redo the carb mixture adjustments. at the same time.

 

Hopefully you didn't pulg the Crankcase vent like some kids do

 

 

highly unlikely but maybe you bernt a valve since you had no exhaust.

 

 

the small could be a blow intake exhaust gasket. I get this all the time with the felpro gaskets as my bolt loosen up then they just wear thru.  When motor cold put you hand in there and as it warms before the manifold gets too hot youll fell the hot gasses. or cheak for bolts missing


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#10 MapleNuts

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Posted 26 May 2016 - 02:29 PM

Alright so i did a valve adjustment and put new spark plugs in and set the timing. Ran it around the block a few times and i could already see oil on the plug. 

 

Don't believe the choke is stuck. There is no black smoke, only white. Only getting low spark when the spark plug is fouled up with oil.

 

Haven't checked the valve lash but i'll figure out how too and do it.

 

Points are all good, coils fine.

 

Tried some carb adjustment but didn't seem to do anything (idk if this is normal but it takes several full turns on the mixture screw to have any noticeable difference, it's a pretty new weber 32/36)

 

Definitely have the crank case vent unplugged 

 

Only had exhaust off it for a week or 2 so i hope it didn't bend a valve in that time.

 

Does Not seem like a intake/exhaust gasket problem, still makes power fine until the spark plugs gunk up.

 

And its my 610 in the avatar and i'm all over kent/renton.

 

What should i do now to figure out what the heck is going on.

 

Thanks again for your time guys.



#11 datzenmike

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Posted 26 May 2016 - 04:49 PM

Valve lash is critical. Valve must seal in the explosion when the plug fires. Intake valve must seal the intake manifold off from the combustion chamber or there will be a loss of vacuum. The exhaust valve must seal the explosion in the cylinder so that it can push the piston down and do work. 

 

White smoke? Or steam??? Do you need to top up the rad regularly? Are you loosing coolant???

 

 

If oil burning is excessive (I mean really excessive) it appears white. Do you need to add oil regularly??? How many miles before adding a quart???


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#12 MapleNuts

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Posted 26 May 2016 - 07:51 PM

Radiator is fine, don't have to top it off, no coolant in my oil as well.  I add oil every once in awhile probably more so due to the old oil pan gasket. I don't know how many miles until i add a quart, it's just here and there. Guess is adjust the valve lashes. Could it be putting oil into the cylinder though old piston rings or in from the top of the head somehow?



#13 datzenmike

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Posted 27 May 2016 - 05:19 AM

You mention white smoke.... has to be oil or water. If not coolant then it has to be oil. If you can see smoke while driving it's a problem. Points of entry are the rings and the valve seals. Valve seals can be easily replaced without removing the head. Rings require a major tear down. Valve seals are only 2 bucks? each.

 

Place some cardboard under the engine and check in the morning to gauge how much is dripping. It can be worse while driving.


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#14 racerx

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Posted 29 May 2016 - 06:02 PM

Has a compression check been done? Do when car is operating temp., use screw in type of compression tester not plug in type, more accurate and throttle should be wide open.

#15 MapleNuts

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Posted 03 June 2016 - 02:29 PM

So i did a compression test (I forgot to do it at temp) but it came back with 120 across all cylinders.

Next I did a ghetto leak down test. (because harbor freight was out of leakdown testers) 

Set cyl 4 at TDC and ran air straight from my compressor into the cylinder and it air shot out the intake.( its not a slight leak either)

Also checked radiator, exhaust, and dipstick  and no air come from there

How can I have good compression yet air is leaking from the intake at the same time? Was it really not at TDC due to the amount of air coming out?

Then I removed spark plug from cyl 3 and shot air into cyl 4 again, and air shot out from cyl 3 plug hole and the intake.

Does this mean my head gasket is broken between cylinders 4&3?



#16 Draker

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Posted 03 June 2016 - 03:35 PM

So i did a compression test (I forgot to do it at temp) but it came back with 120 across all cylinders.

Next I did a ghetto leak down test. (because harbor freight was out of leakdown testers) 

Set cyl 4 at TDC and ran air straight from my compressor into the cylinder and it air shot out the intake.( its not a slight leak either)

Also checked radiator, exhaust, and dipstick  and no air come from there

How can I have good compression yet air is leaking from the intake at the same time? Was it really not at TDC due to the amount of air coming out?

Then I removed spark plug from cyl 3 and shot air into cyl 4 again, and air shot out from cyl 3 plug hole and the intake.

Does this mean my head gasket is broken between cylinders 4&3?

 

I'd first make sure you were at TDC. If you had a bad head gasket between 3 and 4.. you probably wouldn't have good compression. Well.. not that 120 is that great to begin with.


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#17 datzenmike

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Posted 03 June 2016 - 04:15 PM

Take valve cover off and turn engine until both cam lobes on #4 are pointing upward. TDC would have the exhaust at about 2 o'clock and the intake at about 10 o'clock... as viewed from the front.

 

Now make sure that both rocker arms are very slightly loose and can be wiggled. This should be the valve lash or clearance between the rocker and the cam lobe. If one or both are too tight to be moved either valve may not be closed.

 

If the above is correct and air is coming out the intake then the gasket may be blown into the #3 cylinder.  At TDC on #4, the #3 piston is at BDC and the intake is open for another 52 degrees of crank turn. Air is just blowing through the gasket and out the #3 intake valve.


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#18 MapleNuts

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Posted 03 June 2016 - 05:33 PM

Thanks guys, i'll double check everything and proceed from there. hopefully i won't have to mill the block



#19 datzenmike

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Posted 03 June 2016 - 07:52 PM

The block is least likely to warp. Aluminum heads are a different story. Avoid over heating an aluminum head.


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#20 MapleNuts

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Posted 08 June 2016 - 11:34 AM

So i pulled the head and the gasket doesn't seemed to be broken or warped between cylinders 3&4. But the gasket does look pretty grimey and the valves look like they have a lot of build up. I have no idea if it's too much build up, or if the gasket it obviously failing. Could you guys help me assess weather i need to redo my valves and what the general condition of the head is because i still have no idea why so much oil was coming into my cylinders and fouling the plugs. Heres some picture, thanks.

http://imgur.com/a/bQW9L