Hey fellas, I had a lifter go bad on my 78 351M. I replaced it today and have several issues, the worst being a loud ticking noise...which Im pretty sure is just an exhaust leak. Goes up in RPM and everything and is also filling the engine bay with fumes so its making it hard for me to tune my carb.

Speaking of the carb, whats the base setting for the idle screws? 2 turns out? Then tune for max vacuum? Ive done this many times before on my LTD...its just been awhile.

 

I want to say 3 turns, but I could be mistaken.

 

I always start at 1 1/2 turns out, I have had to turn them in from there sometimes and turn them out sometimes but they are usually pretty close if all is well with everything else..

 

That's where I was taught to base line them! Get max speed out of the idle adjustments, lower the idle, fine tune. Or in till the stumble, out to the stumble and split the difference whether you want it rich or lean.

Same theory applies for using a vacuum gauge. Highest vac reading at the correct idle speed for your application.

 

Well than i guess I have some kind of wicked vacuum leak. Also cleaning and fixing my carb since the idle speed screw decided to break off when I went to turn it.

IF it would Idle, Id be pulling about 10" of vacuum. But it doesnt want to idle.

Also, what can cause it to backfire out of the carb? not like a poof...but a big fireball? WAY overly rich? Cause when I try to rev it...the fireball happens. Last time I had this happen it meant i was runnign way too lean...but I have the screws like 5 turns out....so yeah I think its a vac leak.

 

ok i got it to idle somewhat. Its pulling 5" of vacuum. No more. Its consistently idling though around 800rpm. Turning the screws in and out have no effect on the vacuum but the motor does stumble when they are adjusted too far in either direction. So....vacuum leak.

Still have no carb cleaner....

But for the exhaust leak Im going to try something. im gonna let it all cool down and then put baby powder around where I think its leaking. When I start it up it should blow the powder away leaving a visual clue to where its leaking.

 

Your radiator fan may blow most of the powder away before you get a chance to see where the exhaust leak is. Would make for an entertaining spectacle

 

sounds like your pulling it together... your timming may need to be tweeked along with carb work.... 1 1/2 turns is your starting point.. if you have a vacuam leak try spraying starting fluid along your intake mounting surfaces and around the carb base... if the leak is there the engine rpms will climb... also recheck your vacuam hoses and plus a simple cracked cap can cause the odd idle rpm...

 

I know theres a vacuum leak... jsut cant find it till I get some carb cleaner.

Bigger issue now...theres a rythmic tonk tonk tonk tonk and its not an exhaust leak. took a metal rod and sounded it out...i can hear a tonk coming from the #5 cylinder area... i guess Ill take a video for yall

 

good luck with the vacuam leak but it may sound like you may have a loose rod or wrist pin..

 

Its not a rod or wrist pin...its coming from the valvetrain area.

As for the vacuum leak. Its the intake Manifold. Does anyone know what those bolts are supposed to be tightened to? In my book it said 25ft pounds.

That would explain the 5" of vacuum.

 

If the EGR plate is aluminum it is possible to be the vacuum and exhaust leak. Try squirting ATF down the carbureator , that usually will show the exhaust leak and make the neighbors happy.

 

Here's a vid on whats going on.

What im dealing with right now - YouTube

It sounds like its running overly rich.

Also the 5" of vacuum doesnt make sense.

 

FIXED IT! Vacuum lines were literally backwards. lol. Shes now pulling a strong 13" of vacuum. Engines worn so Im cool with that.

 

right on,, does it still rattle or tick???