Technical SBC 350 Timing Mark Question

I don't know my ears may just not be experienced enough.

Here is a video of it set at 10 deg BTDC with the canister and line plugged. I moved the vac line to the manifold port on the carb and I feel the vacuum. It also raises the idle when I plug it back in.





Here is a video after I plugged the vac line and adjust the idle screw slightly to go a little lower.



Here is a video after driving it for a 10 minutes.




I could swear I hear a little buzzing sound from the driver side with the vac advance plugged in and when it idles a little higher. It could also be my imagination but maybe someone can hear it in the second video. I didn't hear any pinging noise when driving it.

Does it sound like it's running right? Especially in the last video? My ears can't determine if its got a miss or not or if the cam sounds like that. It's got an RV cam (supposedly) and most of the time I've driven this thing its sounded very lopey probably for a lot of reasons (running on 7 cylinder until I had the head worked on, the vac line on the port instead of manifold, etc etc). Can anyone tell from the vids if there is something wrong? I also noticed it starts right up when cold and when warm where as before it took a bit of effort to get it running.

Lastly my brakes were randomly dragging... I'm going to have to open another thread after I re-examine.. they worked fine last time I drove this thing.. ugh.

 

Also for reference here is what it sounded like last week when I had it at 4deg BTDC with the vac line on the ported outlet on the carb.

 

the timing at 10 sounds pretty good. again if the distributor has 24 degrees in it with the the 10 initial you are close to where you need to be with a mild sbc.

hooking to manifold vacuum will make it idle faster as the manifold vacuum is pulling the diaphragm of the vacuum unit making it advance, and according to some that is what you want.

the whole manifold vs. ported thing can take a day to read on google and will come down to what your engine wants. try running with both to see if there is a difference and what the engine seems to like and which ever one it is stick with it....good luck

 

With Manifold you get more advance at light loads and less under heavy loads. Ported get you more at high RPM, more air flow. With todays fuel manifold makes more sense if there is enough mechanical at high RPM.

 

Thanks it feels better at idle with manifold port. It drove good and didn't ping. In the last clip you can hear the exhaust after it was driven and warmed up. It sounds way less Lopey than it used to.

If it was misfiring would it sound more obvious? Prior to getting the head worked on it was running on 7 cylinders and with the Lopey idle my ears could not tell it was misfiring. Someone had to point it out to me.

Is it possible to tell from my 3rd video? I can't tell what it should sound like with the rv cam and the glasspacks

 

When I changed mine over to manifold vac, I noticed that it was running cooler too.

 

Sounds good to me. What is your idle set at before and after it warms up?

 

Thanks. I'm not sure yet I just adjusted the idle screw by ear to where it sounded good but not too high when switched to manifold port. I'm going to get a vacuum gauge so I can quantify the setting, etc.

I'm still not able to detect a misfiring engine with my ears and I'm not sure if it's a signature you pick up over the years. Here is a video from last year when the vac line was running on ported. In this video I know for sure it was running on 7 cylinders because this was prior to me taking the head out and having the stuck #1 exhaust valve fixed. Does it sound obvious to anyone that it was misfiring? I'm just curious if it's obvious in this video to anyone and whether it seems gone in the video I shot last night. My ears can't tell much difference between either videos except for the lopey sound reducing after switching to manifold port on the carb.

 

It is sounding a thousand percent better. Starting to sound like a small block Chevy. Keep on working at it. It's only going to get better.

 

Thanks.

I have read that an RV cam is pretty mild and should sound pretty smooth but have a little lopey sound. I'm not sure mine really has an RV cam (that is based on what the previous owner told me). I notice it doesn't sound very even (even with the lopey sound) over a few seconds time. Is this perhaps the cam and combination of having 22" glasspacks or should I be concerned and diagnosing it some more?

Here is the video again with the sound after it was driven