help

[510_boyz]

has a L20b smokes so i desided to take it apart & found these numbers on pistons 1,2&4 - u34 & on piston 3- u23 the 4's & the 3 are small i want to know what it means

 

 

[MicroMachinery]

I imagine that it has something to do with the casting. Possibly at some point one of the pistons went bad, so it was replaced. If they all are the same diameter, I wouldn't be concerned about it. I've pulled apart plenty of engines that had mismatched pistons. Not ideal, but it works.

[510_boyz]

ok thanks

[510_boyz]

L20B turns over but wont start what can it be?? did a compression check its low very low

 

 

[datzenmike]

If the rings and/or cylinder walls are trashed the compression will leak past them.

 

 

Other causes:

 

Valve lash is too tight or none. This will prevent the valve from closing fully and compression will leak out.

Valve face is worn, pitted or cracked and compression will leak out

Head gasket is blown allowing compression to leak out. If two adjacent cylinders are very low the gasket may be blown between them. If the gasket is blown into the water jacket you may notice some or all: steam in the exhaust pipe while driving, rad level dropping, over pressurized cooling system when the motor is first started and run that pushes coolant out the over flow tube, with rad cap off you may see bubbles/foam while idling or smell gas in the coolant

[510_boyz]

can it be i used a used head gasket i pulled off a l16 i had just torqued to fix a blown 1 on ths l16 but i upgraded to a l20 it smoked pulled it out & rebuilt it now it dont wanna start

[datzenmike]

A used 83mm bore gasket is going to overhang an 85mm bore L20B cylinder. It may not seal against the metal 'fire ring'. Besides the metal ring will be exposed to the high cylinder temps and erode away. It needs a proper L20B gasket that is just back from the bore edge and safely sandwiched between head and block surfaces.

[metalmonkey47]

Valve seals also cause a lack of compression, if I'm correct.

 

What exactly was the compression?

[MikeRL411]

has a L20b smokes so i desided to take it apart & found these numbers on pistons 1,2&4 - u34 & on piston 3- u23 the 4's & the 3 are small i want to know what it means

Production line tooling gets worn with time. The assembly line checks the actual bore diameter of each cylinder and assigns a number grade. The corresponding diameter piston [they also are not machined by angels so have varying diameters] which is also marked with a number grade is then assigned to each cylinder. Consider it a cheapo "blueprinting" on assembly. It works out very well.

[datzenmike]

Valve seals also cause a lack of compression, if I'm correct.

 

What exactly was the compression?

 

The seals are up on the valve stem in the ports, and seal it and the head from leaking exhaust or vacuum in the intake side. The combustion chamber is sealed by the tight fitting valve face on the valve seat by the valve spring.

[510_boyz]

Valve seals also cause a lack of compression, if I'm correct.

 

What exactly was the compression?

 

 

i put new rings....befor we took it apert the compression was 165 - 175 now its 62 - 74

[sssr20det510]

Is your timing chain on right

[510_boyz]

how can you tell what side is what?

 

 

[metalmonkey47]

Is your timing chain on right

 

Didn't think about that.

 

Check your cam timing. If your valves are opening during the compression stroke, you won't have the compression you need, nor will it fire.

[banzai510(hainz)]

see if this link works. I cant watch my own video cuase it gets blocked

 

ck the valve lash

 

http://www.guba.com/watch/3000024223/Hainz-Datsun-L-Series-Engine-01-Timing-Tare-down-and-Rebuild

[510_boyz]

anyone around long beach willing to come help me make this engine run

[510_boyz]

checked everthing i can sill no compression....on the old piston some have on 1 side RI] [s on othere side .... some have on 1 side r] [s on othere side some have nothing on bothe sides ..... dont know how to mic the cylinder walls

[zerow]

Run a teaspoon of oil down the spark plug holes, and check the compression again. If it goes up then its the ring contact against the cylinder walls. If it does not go up, then its valves or valvetrain related components (timing off, valve seals, etc. etc.)

[datzenmike]

can it be i used a used head gasket i pulled off a l16 i had just torqued to fix a blown 1 on ths l16 but i upgraded to a l20 it smoked pulled it out & rebuilt it now it dont wanna start

 

 

i put new rings....befor we took it apert the compression was 165 - 175 now its 62 - 74

 

With great compression numbers like that I would be looking elsewhere for the oil smoke like bad valve seals.

 

Did you hone the cylinders before putting the new rings in?

 

Did you stagger the ring end gaps so they aren't one above the other?

 

 

To quickly check the valve timing take the valve cover off and crank motor over until the intake cam lobe is (roughly) at the 10 o'clock position as viewed from the front with the exhaust cam lobe at the 1 o'clock position.

 

Now look for the timing notch on the crank pulley and turn crank by hand to position it at the ZERO point on the timing scale bolted to the timing cover just behind it. It should be close nearby....

 

With crank at TDC look through the top hole on the cam sprocket. Look down at the back of the sprocket and you will see a V notch. Just behind that on the cam thrust plate will be a smalll horizontal etch mark. If properly timed the V notch will be just below the etch mark or just slightly to the right.

 

While at TDC, take the distributor cap off and check that the rotor is directly (or very near) the #1 plug wire above it on the cap.

[510_boyz]

Did you hone the cylinders before putting the new rings in?

 

Did you stagger the ring end gaps so they aren't one above the other?

 

 

 

 

 

yes & yes

[datzenmike]

Well check the cam timing and valve lash. If they are close then maybe that used L16 head gasket is the cause.

[510_boyz]

just got a new eng well new to me donno anything about it but this "troy Ermish biult racing L20B long block,w/L16 oil pan, polish valve cover, dizzy distributor, new race clutch,new starter,new alt,240zx water pump, exhaust manifold fresh 32/36dg webber w/elec/chok w/throttle linkage chrome air filter only 30miles on it" ..... low compression on 1 & 2 what head gasket should i get i know a l20 but what brand?

[datzenmike]

can it be i used a used head gasket i pulled off a l16 i had just torqued to fix a blown 1 on ths l16 but i upgraded to a l20 it smoked pulled it out & rebuilt it now it dont wanna start

 

 

i put new rings....befor we took it apert the compression was 165 - 175 now its 62 - 74

 

 

just got a new eng well new to me donno anything about it but this "troy Ermish biult racing L20B long block,w/L16 oil pan, polish valve cover, dizzy distributor, new race clutch,new starter,new alt,240zx water pump, exhaust manifold fresh 32/36dg webber w/elec/chok w/throttle linkage chrome air filter only 30miles on it" ..... low compression on 1 & 2 what head gasket should i get i know a l20 but what brand?

 

I think it's time to get a Nissan manual that covers the L series engine or buy something that is running properly. Using a used L16 h/g on an L20B, rebuilding a 165 compression engine down to 62, and now an 'alleged' Ermish race engine that someone paid thousands for that they drove 30 miles and sold to you because of 'low compression in 1 and 2'?

[510_boyz]

got head redone starts & runs but now it knocks think the tenchiner popped off how can i get it back in with out taking the front cover off?? found out what was knocking

[510_boyz]

and yes i put something to hold the timming chain was not the chain #4 valves need to ajusted