Jump to content

Need help asap with L20B


Alan Baleto

Recommended Posts

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?

Link to comment
  • Replies 21
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

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??

 

Link to comment

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!?

Link to comment

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 by banzai510(hainz)
  • Like 1
Link to comment
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.

 

 

 

 

 

 

Link to comment

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!

  • Like 2
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.