Know I know what you guys Are talking about when you describe roasting the tires. I plugged the egr plug plate leak and the elbow connection to the transmission leak and MY GOD what a difference. Like a different car!

 

Welcome to the jungle. Now, change out your fouled spark plugs for even mo' powaaaaah!

 

Don't forget to set your timing, idle and idle mixture screws.

 

that was the first thing I did.

 

I had to increase the idle. Haven't changed the mixture. My timing is currently set to 14* with 20* of mechanical advance and about 11* backed off the vacuum advance with a Crane restrictor. At WOT there's a tiny bit of knock at max rpm just before shifting, but I really don't push it that hard.

 

I second re-establishing your A/F mixture screws to highest achievable vacuum.

 

Id limit the mechanical timing a little more if possible or back down the base timing for no knock. You could try premium gas first if you are not using it already.

 

That's assuming it's detonation and not floating valves.... "max rpm" is a relative and low vacuum/less advance situation.

 

yes its relative for sure, but at max shift rpms he should be all in on the mechanical advance and base timing will only subtract from the total advance as well

Im not going to lie i never take my mild BBO over 5k rpms...

 

max shift rpms with my 455 and auto transmission is under 5k. I would guess it's more like 4500 at most. The knocking is not consistent. It really does not happen often at all or with any regularity. Usually more on hotter days. Not sure how vacuum advance would come into play at WOT.

 

It's probably just crap gas. Run it out, and try a different station/brand.

 

Yeah likefleming said better gas may help, vacuum advance should be nil at WOT.

i was suggesting back off the base timing or the mechanical advance timing like 2* if running premium doesnt help. Mine was similar if i nailed it at hiway speeds when it was hot out i would get some knock. I backed my timing down a little and its good.

i need to get a wideband and dial in the carb a little better i think mines a little lean too.

 

I adjusted the A/F mixture but don't know how to use vacuum as a guide. I rotated the driver's side screw clockwise until rpms dropped then rotated counterclockwise until it started running rough and rotated half-count back. Did the same for the passenger side screw. The engine runs smooth as glass at idle. Never run so smooth. Probably not much of a cam based on lack of lope.

 

Essentially, you performed the adjustment correctly - achieving the highest RPM (without bogging or running rough) equates to roughly the same as using a vacuum gauge to achieve highest vacuum.

 

good advice.

There are some good videos YouTube describing setting idle mixture. Basically, with the engine fully warmed up, choke fully open, and idling, slowly fine tune each mixture screw until you have the highest manifold vacuum, and the highest idle speed. Reset the idle speed and enjoy.

Take the car for a long drive, make a few “spirited” acceleration runs. The idea is to clean the carbon and crud out of the combustion chamber. If it still rattles at WOT, either go up a grade of gas, try a different brand of gas, or back off the timing a little.

 

aka: the Italian Tune-up 🤪

 

ahh yes the I-talian tune up with Berrymans B12 and a long drive. Haven't noticed anymore knocking. The car definitely has more off the line and top end performance.