TBI rebuild

[Schurkey]

I was in fact off a tooth... ...Got it all back together and fired up and ran the same.

That's what I was trying to tell you. IF the timing is right, the timing is right no matter what the position of the distributor.

Manually adjusted dizzy by ear and it sounded best at 12 deg adv. When I reved it it smelled almost like burnt oil so I put it to 2-1deg adv. I will take it to oreileys and use their gun to confirm mine.

Timing by ear generally results in way-advanced timing. It's probably good that you set it back closer to OEM spec.

Also, the cough is still present at the passenger side tail pipe... ...and the passenger side still has a cough/miss. Is this pretty much indication of a burnt valve?

Anyway to confirm burnt valve without tearing engine apart?

Cylinder leakdown test.

Pump air into the cylinder, with the piston at TDC. See (hear) where it leaks out. If you hear it at the intake/throttle body, it's leaking out the intake valve. If you hear it at the tailpipe, it's leaking out the exhaust valve. You WILL hear it at the oil fill cap, becasue there's ALWAYS leakage past the rings--but you need to determine if the leakage is EXCESSIVE. And if there's any bubbling or pressure at the radiator cap, you've got a popped head gasket or cracked casting.

Use an actual leakdown tester so you can put numbers to the leakdown quantity. (But be aware that leakdown testers don't all generate the same numbers, due to construction differences in the testers.)

 

[tsr2185]

That's what I was trying to tell you. IF the timing is right, the timing is right no matter what the position of the distributor.


Timing by ear generally results in way-advanced timing. It's probably good that you set it back closer to OEM spec.


Cylinder leakdown test.

Pump air into the cylinder, see where it leaks out. If you hear it at the intake/throttle body, it's leaking out the intake valve. If you hear it at the tailpipe, it's leaking out the exhaust valve. You WILL hear it at the oil fill cap, becasue there's ALWAYS leakage past the rings--but you need to determine if the leakage is EXCESSIVE. And if there's any bubbling or pressure at the radiator cap, you've got a popped head gasket or cracked casting.

Use an actual leakdown tester so you can put numbers to the leakdown quantity. (But be aware that leakdown testers don't all generate the same numbers, due to construction differences in the testers.)

Next step is a leakdown test kit then. Thanks!

 

[Schurkey]

Next step is a leakdown test kit then. Thanks!

Get one that's approved by Continental/Teledyne.

I said that leakdown testers aren't all constructed the same. The way around that is to "calibrate" your tester based on a Master Orifice. Far as I know, Continental/Teledyne invented this. At least, they specify a Master Orifice when testing their aircraft engines.

I bought my second leakdown tester from Aircraft Tool Supply, with a Master Orifice built-in. You want the one with a .040 regular orifice, for bore sizes smaller than 5 inches.

Tell them you want the 14mm cylinder adapter instead of the 18mm adapter it normally ships with.

ATS PRO DIFFERENTIAL PRESSURE TESTER WITH MASTER ORIFICE from Aircraft Tool Supply

ATS PRO DIFFERENTIAL PRESSURE TESTER WITH MASTER ORIFICE - Our own ATS brand Differential Cylinder Pressure Tester combines the features of our popular 2E tester and a Master Orifice into one tool.

www.aircraft-tool.com

 

[tsr2185]

Get one that's approved by Continental/Teledyne.

I said that leakdown testers aren't all constructed the same. The way around that is to "calibrate" your tester based on a Master Orifice. Far as I know, Continental/Teledyne invented this. At least, they specify a Master Orifice when testing their aircraft engines.

I bought my second leakdown tester from Aircraft Tool Supply, with a Master Orifice built-in. You want the one with a .040 regular orifice, for bore sizes smaller than 5 inches.

Tell them you want the 14mm cylinder adapter instead of the 18mm adapter it normally ships with.

ATS PRO DIFFERENTIAL PRESSURE TESTER WITH MASTER ORIFICE from Aircraft Tool Supply

ATS PRO DIFFERENTIAL PRESSURE TESTER WITH MASTER ORIFICE - Our own ATS brand Differential Cylinder Pressure Tester combines the features of our popular 2E tester and a Master Orifice into one tool.

www.aircraft-tool.com

Any budget friendly ones like from amazon round 40-50$

 

[thinger2]

Could be a valve. Or a stuck lifter or a bent pushrod or a flat cam lobe or a bad rocker arm or a pulled rocker stud or a weak valve spring etc...
Could also be a bad plug or wire or even a bad dist cap.
A leakdown test will tell you which cylinder is the problem if it is a mechanical issue and not ignition related.
Set the timing back to zero and do the proper reset procedure.
Pull all of the plugs. Dont mix them up keep them in order of which plug came from which hole.
Look for any differences between the plugs. If its been running rich you might not see anything but its worth a look.
Check the gap on all of the plugs.
Since they are a bit of a pain to get at it isnt unheard of to accidently bang the gap shut while putting them in.
With it at operating temp, pull the wire of each plug one at a time and see if that stumble changes.
If not, put it back on and try the next one.
Do all 8 of them.
Be carefull doing this. I recommend getting a plug boot tool. pull them from the plug. not from the cap
If you pull a plug, and the stumble goes away or changes. That is the cylinder.
If you narrow it down. You have a couple of options.
Stick a brand new properly gapped plug in and see if it still stumbles.
If it does, put a different good plug wire on it.
You can also move that plug to a different hole and see if the misfire follows it.
You can do the same thing with the wire.
See if you can make it misfire on a different cylinder.
I get it, not everyone has a scanner though you should.
But that takes waiting on Ebay and a learning curve and sime time to figure it out.
Not everyone has the equipment to do a leakdown test.
This is old school side of the road broke ass tricks.
And they work too!

 

[tsr2185]

That's what I was trying to tell you. IF the timing is right, the timing is right no matter what the position of the distributor.


Timing by ear generally results in way-advanced timing. It's probably good that you set it back closer to OEM spec.


Cylinder leakdown test.

Pump air into the cylinder, with the piston at TDC. See (hear) where it leaks out. If you hear it at the intake/throttle body, it's leaking out the intake valve. If you hear it at the tailpipe, it's leaking out the exhaust valve. You WILL hear it at the oil fill cap, becasue there's ALWAYS leakage past the rings--but you need to determine if the leakage is EXCESSIVE. And if there's any bubbling or pressure at the radiator cap, you've got a popped head gasket or cracked casting.

Use an actual leakdown tester so you can put numbers to the leakdown quantity. (But be aware that leakdown testers don't all generate the same numbers, due to construction differences in the testers.)

Also forgot to mention...

When using my timing gun, I hooked to a few different wires going into the plugs and I found that the light/pulse was very erratic and not a steady frequency on ALL the wires. Is this common?

 

[Schurkey]

When using my timing gun, I hooked to a few different wires going into the plugs and I found that the light/pulse was very erratic and not a steady frequency on ALL the wires. Is this common?

It's common when the plug wires are crappy.

 

[tsr2185]

It's common when the plug wires are crappy.

They are 8 month old ac delco. Changing them and plugs didnt do a thing

 

[Schurkey]

pull the wire of each plug one at a time and see if that stumble changes.
If not, put it back on and try the next one.
Do all 8 of them.

Ideally, you wouldn't pull the wire off, making an open circuit. This drives the voltage sky-high, and potentially leads to insulation break-down.

Better method is to selectively GROUND the spark. Leads to a near-zero voltage on that firing impulse; no insulation breakdown.

See post 15 of this thread.

 

[tsr2185]

Ideally, you wouldn't pull the wire off, making an open circuit. This drives the voltage sky-high, and potentially leads to insulation break-down.

Better method is to selectively GROUND the spark. Leads to a near-zero voltage on that firing impulse; no insulation breakdown.

See post 15 of this thread.

Before I buy a leakdown kot I will try this on my passenger side cylinders. Thanks.

I got some free nails, hopefully I dont damage anything.