Need help asap with L20B

[Alan Baleto]

Can anyone help me figure out what else I can do to troubleshoot this engine of mine. It idles but does not accelerate. Rebuilt head and block, tried 32/36 Weber and newly rebuilt 38/38 Weber carb, replaced manifold twice with OEM, new shorty headers with piping. Tried 2 new distributors, plugs & wire, cap & rotor, new msd blaster coil, and new battery. New fuel pump, new alternator, new timing cover, chain, and gearing. Tested the compression and it’s avg around 145 psi. Tried the gas cab method as well. Does anyone know what else I can do to get my baby back on the road?

[datzenmike]

First thing is STOP replacing stuff.  It's expensive, it's not working and all the stuff you replaced now likely has poorer quality parts in it or a bad part which adds to the complexity of the fix.

 

What year is this engine? because there were several different L20Bs with different distributors, carbs, ignition systems, heads, intakes.

 

Define.... 'does not accelerate' more clearly. What DOES it do when you drive it?????

 

 

 

Are you plug wires correct? The firing order is 1,3,4,2 in a counter clockwise direction on the distributor.

Timing should be 12⁰ BTDC. Is it?

Valve lash set on a hot engine should be 0.010" intake and 0.012" exhaust. Is it??

 

[Alan Baleto]

Truck is on stands. Engine year should 78. Using another 78 as test vehicle. All parts work on test truck. Truck will idle but when throttling up, it’ll back fire and sputter. Won’t accelerate. Plugged all open unnecessary vacuum ports. Set valve lash to 10 and 12. After market timing chain and gears installed. Truck ran really well for one day!?

[banzai510(hainz)]

Your distributor is most likely off.

what is the timing at idle?

get a timing light.

now if the distributor is crank all to one side then that it . So when you speed up it’s going out of time.

I assume you have a EI coil with this electric ignition.do not use a point coil use a 78/79 coil.

 

ok I reread your post you said it ran really well for one day .check if the coil gets hot then you have a point coil in there with no ballast resistor.

A EI ignition requires a EI coil  that’s it.

only other thing maybe the distributor is loose and went out of time .or distributor bushing worn giving distributor shaft wiggle

 

i would have not put the header on till running top notch as some headers are warped matching washers need to apply pressure the same on intake and exhaust.

if idles then I say the gaskets are tight and that’s ok.

Edited May 17, 2020 by banzai510(hainz)

[datzenmike]

 It backfires with both carburetors???

 

Did you check the plug wire firing order 1,3,4,2 counter clockwise of the distributor cap????

 

 

[Alan Baleto]

1 minute ago, datzenmike said:

 It backfires with both carburetors???

 

Did you check the plug wire firing order 1,3,4,2 counter clockwise of the distributor cap????

 

 

Yes it’s in sequence.

[Alan Baleto]

@banzai510(hainz)she was running before and after headers was installed. Didn’t test with a timing light yet. I have air gap system. Gonna set the timing to 12 degrees btdc and I’ll get back to you all. @datzenmike Thank you both! 

[banzai510(hainz)]

Set to 12 and you should still have plenty of movement on the dist to move more adv like to 20/25btdc and down to almost zero . Then I say your distributor is in timmimg spec.

 

unless you washed this motor and water under cap will do the same thing

[banzai510(hainz)]

update??????????

[Alan Baleto]

We set the timing to 12btdc, got good idle but backfired at higher rpm. Took it on the road and no back pressure as rpm rises.

[datzenmike]

Just how are you measuring the 'back pressure'?

 

On 5/17/2020 at 4:45 PM, Alan Baleto said:

Yes it’s in sequence.

 

But is it counter clockwise?

 

 

[banzai510(hainz)]

Like I said when it set to 12 deg

Is the distributor crank one side to get the 12 deg?????

[Alan Baleto]

Just by taking her for a ride. Once I push on the pedal it’ll start maxing out. Yup, counter clockwise 1,3,4,2.

[Alan Baleto]

Yup set the 12 and crank on one side. I’m dismantling the engine to try my spare head.

[Alan Baleto]

I’ll keep you guys posted🤙🏾

[Alan Baleto]

We didn't measure back pressure but, I know the exhaust is large 21/2" maybe 3" and direct flow muffler. Hardly any back pressure.

[banzai510(hainz)]

2 inch is about perfect 

 

if you had to turn the distributor all the way over and you ran out of slot to get 12 then I say your off a tooth.bur you said it ran perfect for a day.so that means it was good.

 

is valve lash adjusted good?

 

your dismantle engine now?

 

this was a simple fix w/o tearing motor apart

 

i quit

[Alan Baleto]

Yup, gonna make adjustments. There is also a oil leak so might as well start over and carefully and precisely do the do’s. Thanks again!

[datzenmike]

1 hour ago, Alan Baleto said:

Yup set the 12 and crank on one side. I’m dismantling the engine to try my spare head.

 

WOAH. Already said to stop replacing stuff. Figure out the problem first. Don't go changing shit. Find the problem fix the problem. Changing parts can add problems that were not there. As mentioned the valve lash may be off.

 

1 hour ago, Alan Baleto said:

We didn't measure back pressure but, I know the exhaust is large 21/2" maybe 3" and direct flow muffler. Hardly any back pressure.

 

Forget back pressure. Back pressure can only be a problem if you have too much of it.

 

 

 

 

 

 

[Alan Baleto]

I wanted to thank you guys for all your help and communication. After all the fix was just a stupid mistake. The problem was in the transistor ignition box. I mistakenly connected the green wire to the red slot and the red to the green. So this whole time I had my Uncle going crazy and second guessing his knowledge about Datsun's. Lesson learned!

[datzenmike]

Cheap fix though....

[banzai510(hainz)]

5th line of my May 18th post