151 replies to this topic

[MapleNuts]

seems all four sparks are the same off the coil. the shaft doesn't wiggle either

[datzenmike]

Then assume the spark isn't the problem. Are the valves set to the right clearance??

[MapleNuts]

Just did another valve lash, there is less afterfire, but there is still a problematic amount of afterfire. And wouldn't my points sparking inconsistently in the video be an issue too?

[datzenmike]

seems all four sparks are the same off the coil. the shaft doesn't wiggle either

 

Though we laid that to rest....

[MapleNuts]

alright so what could be the next thing causing the afterfire?

[datzenmike]

A compression test might show a low cylinder but not why.. Even better a leak down test which are just two gauges separated by a small orifice. The input gauge valve can be adjusted to 100PSI and on the other side of the restriction the other gauge reads a percentage showing the loss. (because there will always be some leakage) 10% would be very good and also not that likely. 15% to 20% would be average to fair. Above 20% bears looking into. A leak down test puts compressed air into the closed cylinder. A leaking intake will hiss out the carb, leaking exhaust valve out the tail pipe. I'm leaning towards a bad exhaust valve or seat or both. Hissing sound out the valve cover breather can be broken piston and/or rings. Air bubbles in the rad can be a blown head gasket.

[racerx]

Did u say that u tried adjusting ur carb and no change? When u turn the idle mixtute screw, ur rpm should either go up or down. Did it? Do this while the car is not on. Turn the idle mixture all the way in, cw, but dont force it. Then turn out ccw sttart the car, it should run. Drive around for a bit and check ur spark plugs. It should be tan in color, if its black and sooty then your running rich. Your rpm should be around 800. Btw where are u located

[MapleNuts]

Haven't tried that method of tuning yet. But i did turn it in untill it started stalling, and then backed it out about a full turn. It still after fired then and it felt like it was running lean. I'll mess around with it a little more and see what i can do.

I'm in washington, king county area

[banzai510(hainz)]

IM hoping the timming is correct.

a swap in dist that set wrong.

 

 

gas smell in oil can be fuel pump.

 

always ck the spark at output of the coil!!!!!!!!! not the points. Belive it or not you don't want spark at the points if perfect. Spark cause the pitting that why the capicator(condenser)

[racerx]

After adjusting the carb, what color was your spark plugs?  Also for more specific and detail on how to adjust your 32/36 go search on this forum for weber tuning.

[racerx]

to check your distributor if properly set, turn crank by hand and watch for #1 cylinder at compression stroke, either have an assistant stick their finger on spark plug hole of number 1 or you (you will feel compressed air coming), and see if it lines up at TDC or Zero degrees of pulley.  Your two front cam lobes (take off valve cover)  should be at 10 and 2 oclock, my L18 dist rotor will point towards the front and rotor point will also towards the number one cylinder.  You can see this when you put the cap on and rotor is pointing at number 1 of spark plug wire.  Always start with base setting,  1) distributor is set properly, 2) points within range of gap/dwell, 3) carb is set base level and go from there.

[datzenmike]

This 'afterfire'.... is it extremely loud explosion? or POPs or just rumbly uneven exhaust sounds because there is an anti backfire valve on L20Bs. If not there or inoperative there will be some exhaust noise on deceleration.

[MapleNuts]

at TDC the rotor is on 1st cyl but a little to the left of it, idk if it needs to be dead on it or not. And my timing mark is at +12. 

The plugs were black but i was like 2-2 1/2 turns out so it was rich but seemed to have more power. however cyl 1 plug was closer to tan.

the color progressively got worse from cyl 1 to cyl 4.

 

The after fire is mostly on deceleration, it pops, and if i was on the gas hard enough before hand there is an extremely loud explosion. followed by some smaller pops.

 

also i can turn my mixture screw in all the way and the car doesn't die at idle, but is obviously running extremely lean, idk if this means i have the right jets or not.

[MapleNuts]

just did a leak down test as well. came back with ~%15

[datzenmike]

15% is not bad, but what cylinder? or all?

 

Do you have a straight through fart can or 'glass pack' or anything that can't really be called a muffler?

 

Has the 'pollution crap' been removed from your engine? Particularly the anti backfire valve?

[racerx]

Turn your idle mixture 1/2 cw and drive car around at least 5 minutes and pull over and check you plugs, careful of exhaust manifold, very hot.  If your spark plugs are still black, then turn the idle mixture CW another 1/2 turn and do the same and check your plugs.  Your RPM may go down a bit so you may have to adjust your idle RPM, around 800 or so. You should not run your plugs too black, it should be brownish/tan looking color.  If you keep on adjusting your idle mixture CW and then your plugs are whitish color then that's too lean.

[MapleNuts]

%15 on all cylinders. I have the muffler side off so its just the downpipe with cat at the moment because i plan on straight piping it.

There is no anti backfire valve, my dumbass probably thought it was emissions junk and removed it when i first put the weber on.

also removed the EGR valve. 

I couldn't exactly tell where the A.B. valve hooks up when looking in the service manual. 

does it go to a fitting right by the PCV valve and then to the T in the smog pump hose?

[MapleNuts]

And i'll try that out soon racerx

[datzenmike]

On deceleration the fuel mix goes extra rich and tends to burn in the exhaust manifold and pipes. The AB valve senses high vacuum and opens to let air into the intake to lean it out.

 

Hey, if this is the cause of the noise, guess what? There is no problem. Put a muffler on it. Or put an AB valve back on.

[MapleNuts]

Well it was fouling out my plugs with all the gas. cyl4 plug reeked of gas. 

I'm going to try to tune the carb the best i can and put the AB valve back on and see how it goes.

Is there 2 hoses coming from the intake to the AB valve?

a smaller vacuum one and larger one

then one to the carb