When you say you get 35 degrees total without the vacuum advance connected, what RPM is it that you get 35 degrees ? That'll tell you whether or not you have weak springs.

It sounds more like the vacuum advance is doing TOO much. Are you sure it's not adjustable?

 

I got 35* W/O the advance connected on both a snap throttle and a controlled throttle. On the snap throttle I didn't check the RPM and on the controlled I took it up to about 3500RPM. The engine did both of those with no knocks or backfires.

I'll go check to see if the advance is adjustable.


OK so I just checked and yes it does have an adjustment screw in the advance. But it was already screwed all the way in clockwise, isn't that the way I would want it to go in this situation? Going counter-clockwise would bring the full advance on sooner right?

 

Depends on if it's left or right-handed threads (just kidding, but who knows)

I think clockwise is going to weaken the spring. Counter-clockwise will strengthen it. Which means the way it's adjusted right now, it's going to come in like gangbusters.

Which makes sense, based on what you've observed.

 

OK so I had a little time to play with the advance. I adjusted it out a bit, looked to be 7.75 turns stop-to-stop. I started at the half way point and turned it 3 turns CC. So I'm about out of turns now. I've got it running up in the 42* full advance area. But the knock is still there, it has lessened though and doesn't stay around as long. It shows up at around 1600RPM which is about 35* and stays until around 2k or I crack 40*. Well it may not be going away completely, but it definitely lessens in intensity.

Also I was checking intake vacuum today and noticed it looks a little odd. I only have around 13" at idle which seems low. But at a slow throttle increase I gain vacuum. On a snap throttle it seems to be normal. I'd say this is too much timing advance or incorrect valve timing. I've checked #1 TDC to both valves being closed like half a dozen times at this point and am pretty well sure that all the mechanicals are right. So could this be effecting or causing my knock problem?

 

What cam is in it?

Have you tried pulling off the initial timing and seeing if the knock goes away?

 

I have a Clevite RV cam. Here's all the specs I could find on it:

Ford FE RV Torque Camshaft
Part Number: 229-1776
Manufacturer: Clevite 77

Clevite RV Torque camshaft for Ford FE 332-352-390-410-427-428. Operating range 1500-4000 RPM with a smooth idle. Use stock valve springs and hydraulic lifters. Cam specs as follows:<table bgcolor="#ffffff" cellpadding="2" cellspacing="0" width="100%"><tbody><tr><td valign="top">
</td><td valign="top">Lift 484/510
Adv. duration 270/280
Duration @.050" 204/214
Lobe sep. 107/117
</td></tr></tbody></table>I have thought about just pulling the vacuum advance and living with whatever the full mechanical advance is plus initial. It seems to me that the motor is only looking for around 32-35* total advance. More than that and it knocks.

 

Well thanks again for all the input guys. It really helped. I got the advance adjusted to that I have no more knock. I'm gonna take it on a cruse tonight to see how she does. Thanks again.