Guys with pushrods

[scottiec]

I have been noticing on my longer drives that when I am just cruising and accelerate lightly, I hear a lot of valvetrian noise.

Does everyone else get that?

[CraigS]

Sure it's not knocking? Or possibly an exhaust leak at one cylinder? Use a small mirror to look under the header at each port for black soot tell tail.

[stack]

what kind of cam? some are louder than others

stack

[JIMOCO]

I have the same issue. Tried a couple of different header gaskets with limited results. I went to a couple of engine shops and they, as well as the engine builder think the sound is normal for a street/performance cam. I agree with the other guys, if there are no leaks, it could be normal valve noise.

[scottiec]

Hi guys

It’s a Ford b cam. I am starting to think I am getting a little bit of knocking. I notice it in 5th gear at 2000 rpms. My initial timing is at 13 or 14 degrees. All in I’m at 33 or 34. Could my vacuum advance be adding too much? Not sure if it’s adjustable.

I guess I can unhook the vacuum advance and see is that is causing it.

[Itchief]

You may want to look at the air fuel mixture the noise may be engine knock predetonation

Just a thought

Rick

[scottiec]

Will a lean mixture cause predetonation?

[Itchief]

When I was working with my efi I was trying to lean out the cruise mixture so that I would not smell like a gas can every time I came back from a ride and if I had the mixture too lean I would get a noise that sounded like valve train rattle

Once I set the cruise mixture back to around 13.2/1 the noise stopped

Good luck

Rick

[scottiec]

Thanks Rick

[Itchief]

One last thought using too low octane fuel could also be the cause of the noise

[Norm B]

Is your vacuum advance connected to metered or manifold vacuum? Metered vacuum will cause advance in timing when the throttle is opened. This could cause pinging as could poor quality gasoline.

HTH
Norm

[scottiec]

Norm,

My vacuum advance is connected to the timed spark port located on the side of the metering block above the throttle blades.

I recall reading about connecting it to full manifold. I will check this out today. Also, I don’t think the vacuum canister is adjustable on my pertronix dizzy.

[scottiec]

I put it to manifold, and now my idle is 1300. I recall doing this once and couldn’t get my idle down.

[cv2065]

Start with the easy stuff. Get a stethescope and find out where the noise is coming from. Might just need a valve adjustment on one or multiple rockers. Vacuum canister is not adjustable on a Pertronix....

[Itchief]

Recheck your low rpm timing you now have vacuum advance working

Rick

[Norm B]

Somebody correct me if I am wrong but, I believe vacuum advance is intended to smooth engine performance and increase fuel economy at high vacuum conditions. Highway cruising and idle are the areas that get the most benefit from its use. During these types of operation the throttle plates are barely open and only a small amount of air/fuel mixture is entering the cylinders. Increasing advance at these times allows for more complete combustion during the power stroke. This is what caused your idle speed to increase.

All timing operations during high power demands should be handled by the mechanical advance. The air/fuel mixture should be perfect for combustion and engine RPM should be the only determining factor for the timing advance needed.

I originally had mine connected the same way as you but someone on the forum said to try it the other way and I did some research. I'll see if I can find the article and post a link.

HTH

Norm

[Norm B]

Here is a link to an article
http://www.onallcylinders.com/2015/03/27/ask-away-with-jeff-smith-understanding-vacuum-advance-and-why-you-need-it/

Norm

[CraigS]

I never had any luck running manifold vacuum for the advance. If you start w/ 10-14 deg timing and then add whatever the vac advances it by (my Mallory added 20 deg vac advance until I found out about the adjustment) you end up w/ a ton of advance at idle, 20-30 deg, and a real high idle. My carb could not be closed enough to get the idle anywhere close to 900 w/ all that advance at idle.

[scottiec]

I never had any luck running manifold vacuum for the advance. If you start w/ 10-14 deg timing and then add whatever the vac advances it by (my Mallory added 20 deg vac advance until I found out about the adjustment) you end up w/ a ton of advance at idle, 20-30 deg, and a real high idle. My carb could not be closed enough to get the idle anywhere close to 900 w/ all that advance at idle.

Right. Even if I can get mine closed enough via the primary or secondary adjustment, I am then completely screwing up the transfer slot coverage. The seems like a "damned if you do, damned if you dont" scenario.

I am going to put my air/fuel in the exhaust and see what my AFR is. I had it dialed in pretty well before I had to pull the heads. The resurfacing of the heads removed .008 of material. By my calculations that increases my compression by .20. I would be shocked if that was enough to change my AFR. But, I will check it.

[donshapansky]

Plug off the vacuum advance and try it, I don't think you can have vacuum advance with that much initial spark lead. You are likely over 30 degrees at idle. The original engines with vacuum advance were set at 6 BTDC. With 13 degrees initial I don't think you need vacuum advance, back in the 60's I ran dual point Ford distributors without any vacuum advance, I set initial at 16 on my 428 Cobra Jets and 10 in the distributor for a total of 36 all in at 2,500 rpm, it was a little hard on the starter but the bottom end torque jumped a bunch over the stock distributor arrangement.

[scottiec]

Plug off the vacuum advance and try it, I don't think you can have vacuum advance with that much initial spark lead. You are likely over 30 degrees at idle. The original engines with vacuum advance were set at 6 BTDC. With 13 degrees initial I don't think you need vacuum advance, back in the 60's I ran dual point Ford distributors without any vacuum advance, I set initial at 16 on my 428 Cobra Jets and 10 in the distributor for a total of 36 all in at 2,500 rpm, it was a little hard on the starter but the bottom end torque jumped a bunch over the stock distributor arrangement.

This is interesting to hear. Quick question... Does the timed spark port (the one above the throttle blades located on the metering block) have to be capped? Also, does the canister on the distributor need to be capped as well?

[CraigS]

Cap the port on the carb. Won't hurt to cap the vac unit on the dist but nor needed.

[scottiec]

Cap the port on the carb. Won't hurt to cap the vac unit on the dist but nor needed.

Yeah ive been driving around with it uncapped. Whoops!