Need timing help

[RemCharger]

Another unrelated and cryptic response......?????.....
BOB RENTON

If you want cryptic and unrelated , go back and read post 4 and 6.

 

[66 Sat]

I'm confused while the focus is on the vacuum advance. I realize you say it runs good when it's not hooked up but
the hesitation when whacking the throttle open is not related to vacuum advance - it won't be operating under that condition.
Same with coming off the throttle and backfiring/stalling - I don't see how the vac advance is involved here.

Just out of curiosity - is the car manual or auto?

 

[blue 66 charger]

I run those Firecore distibutors and like them a lot. If you have the 2 weak springs in there, that would be allowing the advance to come in too quickly. I would also bump your total timing down to 32 or so for now. Saying that, it does sound like you have carb issues as well. All the Holley and Quick Fuel mechanical secondary carbs that I have are coming set up way to rich for street driving.

My goal is a street strip setup so I wanted the best of both worlds

 

[blue 66 charger]

I'm confused while the focus is on the vacuum advance. I realize you say it runs good when it's not hooked up but
the hesitation when whacking the throttle open is not related to vacuum advance - it won't be operating under that condition.
Same with coming off the throttle and backfiring/stalling - I don't see how the vac advance is involved here.

Just out of curiosity - is the car manual or auto?

Auto

 

[hunt2elk]

My goal is a street strip setup so I wanted the best of both worlds

Agree, I run them as well. Just saying that they need some leaning out all around to run ideal.

 

[blue 66 charger]

Will do that thank you

 

[Geoff 2]

What are the cam specs?
Idle rpm in gear?
Idle quality: smooth or rough?

With VA hooked up... whacking the throttle & getting a hesitation...can certainly be caused by the VA unit dropping out & reducing timing.

 

[68-500]

The easiest way to set your timing on a mild build IMO. First disconnect the vacuum advance and plug port.
Second set final advance to 34-36 *
Third reinstall vacuum advance on manifold port. That should work fine 99% of the time.

 

[blue 66 charger]

What are the cam specs?
Idle rpm in gear?
Idle quality: smooth or rough?

With VA hooked up... whacking the throttle & getting a hesitation...can certainly be caused by the VA unit dropping out & reducing timing.

Was never able to figure out the cam specs, just assuming its stock by how it runs, it idles just fine in park and in gear.

 

[blue 66 charger]

The easiest way to set your timing on a mild build IMO. First disconnect the vacuum advance and plug port.
Second set final advance to 34-36 *
Third reinstall vacuum advance on manifold port. That should work fine 99% of the time.

I have my total timing already set to 36*, I will definately try manifold vacuum if I can't get ported to smooth out for me

 

[Geoff 2]

Post #30 is exactly the wrong way to hook up Man Vac Adv [ MVA ]. It is also the reason for comments such as ' MVA didn't work for me'. Etc.

MVA operates at IDLE. You FIRST have to determine how much timing THIS engine wants for best idle. This is INCREDIBLY easy to do....

Simply set initial timing to factory spec. Engine idling, in gear if auto, loosen dist clamp & SLOWLY turn dist to advance the timing. Idle rpm & vacuum will increase, & idle will smooth out, even if it is already pretty smooth. Keep advancing the dist until you get the highest rpm. Now check what the timing is...could be anywhere from low 20s to 50*.
Say it is 32*. That can be initial [ whatever ] + the remainder is made up of vac adv. Often, the amount of VA added may need to be limited via a stop on the VA arm. Always use an adj VA unit & turn the screw fully CW as a starting point.

 

[451Mopar]

With the vacuum advance, the arm is usually stamped with how much it advances at the distributor (double it for crank degrees). That is based on the notch where the arm stops moving. That is the total vacuum advance, in the cannister, there should be a screw to adjust the diaphragm spring pressure to control how much vacuum it takes to move the advance arm. A mighty-vac type vacuum source with gauge is handy for adjusting the spring tension.

 

[RJRENTON]

Post #30 is exactly the wrong way to hook up Man Vac Adv [ MVA ]. It is also the reason for comments such as ' MVA didn't work for me'. Etc.

MVA operates at IDLE. You FIRST have to determine how much timing THIS engine wants for best idle. This is INCREDIBLY easy to do....

Simply set initial timing to factory spec. Engine idling, in gear if auto, loosen dist clamp & SLOWLY turn dist to advance the timing. Idle rpm & vacuum will increase, & idle will smooth out, even if it is already pretty smooth. Keep advancing the dist until you get the highest rpm. Now check what the timing is...could be anywhere from low 20s to 50*.
Say it is 32*. That can be initial [ whatever ] + the remainder is made up of vac adv. Often, the amount of VA added may need to be limited via a stop on the VA arm. Always use an adj VA unit & turn the screw fully CW as a starting point.

View attachment 1839247

Once again, posting information from an unknown copyrighted publication, without reference as to who produced the article or reference....name the publication, date, author.....or are you just "cherry picking" words without any reference to imply that the information is by you.....give credit for work done by others...since all you seem to do is plagiarize someone else.......
BOB RENTON

 

[mopar 3 B]

My goal is a street strip setup so I wanted the best of both worlds

Best of both worlds will be a compromise.
Go back and install a good EFI system and ditch the forever changing carb setup.
Just to many variables in a street strip setup. You will be spending more time tuning than driving. Especially if this isn't a daily driver.
Also not sure why no one mentioned it but single plane intakes can be trouble some on street engines. I would learn to read spark plugs if the Holley carb is a necessity.

 

[AR67GTX]

I'm confused while the focus is on the vacuum advance. I realize you say it runs good when it's not hooked up but
the hesitation when whacking the throttle open is not related to vacuum advance - it won't be operating under that condition.
Same with coming off the throttle and backfiring/stalling - I don't see how the vac advance is involved here.

Just out of curiosity - is the car manual or auto?

I agree. The backfiring sounds like a lean condition. I would try opening the idle screws up 1/2 turn and if that seems to help any in the least, then I would try increasing the primary jets 2 sizes, like 70 to 72 for example.

 

[Geoff 2]

So Bob,
If the publication is unknown, how do you know it is copyrighted??????????????????????????????????????????????????????????????????????????????????????????????????????????????
I supply information from various sources that back up/support my statements; sometimes I do mention names. The comments are from very smart people, which would exclude you. idiot.

 

[Geoff 2]

Blue 66 [ & others interested in learning ].
In the last few days, Nicks Garage You Tube, dyno tested a 455 Buick. At around the 18 min 30 sec mark, engine idling, he connects the vac adv to manifold vacuum. You can hear the engine run smoother & rpm increases by about 200 rpm. He spends the next minute or two explaining how to hook up MVA. The rpm increased because the engine is making more hp...

 

[Don Frelier]

Thanks for the information.......IMO....too big for street use, especially the double pump design. I would set your distributor to yield: 35 degree total advance, 15 degree static (@ idle), 20 degrees mechanical advance all in by 2600 RPM.....no vacuum advance both ported and manifold connections capped. Just my opinion of course.....others will disagree..........
BOB RENTON

here's a suggestion with no references.
The service manual certainly doesn't suggest capping the vacuum advance.
Why would you do that on a stock cam?

 

[RJRENTON]

So Bob,
If the publication is unknown, how do you know it is copyrighted??????????????????????????????????????????????????????????????????????????????????????????????????????????????
I supply information from various sources that back up/support my statements; sometimes I do mention names. The comments are from very smart people, which would exclude you. idiot.

SHOW US YOUR SOURCES......or did you just pull them out of your ***......WHERE IS YOUR INFORMATION COMING FROM??? MADE UP OR ???......WHAT ARE YOUR "VARIOUS SOURCES"......JUST WHO ARE THESE "SMART PEOPLE".......YOU REFER TO??? Sarter than I ??? I think not...let's have a thinking contest......or perhaps you just like pounding sand in rat holes without any substantation? Your turn.....
BOB RENTON

 

[Gary Gaz]

Out of interest, have you checked the Vaccunm can actulaay holds vaccunm , recently had a fircore one fail, was doing a tune up and was a slight miss at crusing speed, can had failed.