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Discussion Starter #1
Posting here as not very many folks over in the ignition forum right now.
I have been using a mallory unilite with no vacuum advance canister for decades.

I am putting in a points distributor today hoping I can get a lower idle and better top end and better gas mileage...and so my car does not go into gear so hard. Have always had a bit of trouble with the unilite when playing with the timing but always set it where I thought it felt best.

My engine
71 CE-BB 402 With 063 Heads
Quadrajet and headers
No big thumping cam
Probably 350 to 370 HP just guessing.

Vacuum reading is pretty steady around 15 if my old gauge is close.

So what can should I purchase?
Is there a basic can I should get to start with?

A napa or autozone part# would be very helpfull if anyone has suggestions
 

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There is no way anyone can tell you what you need until you measure manifold vacuum at idle
 

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Page #17:
Regarding vacuum advance - The "2 inch rule".
I've never heard that.

Thanks for posting
Most people including engine builders never have either and the engines build suffers from it. My engine was off after a rebuild and after years of guessing how to fix it. The author of that article helped me dial in my engine. In short after replacing the vacuum advance can and following the two inch rule my engine never ran any better.
 
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"There is no way anyone can tell you what you need until you measure manifold vacuum at idle"

Answered: "Vacuum reading is pretty steady around 15 if my old gauge is close.
 

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Discussion Starter #9
The vacuum has stayed between 14 and 14 1/2 the couple times I checked it.
A bit low from what i have read about it?
Pretty much the same checked on the manifold where tranny mod fitting is
and the front bottom of carb where the pvc plugs in the bottom plate of carb.

I decided to just use the 201-15 can being it was not dead, that was already on it after
going to napa with only one choice available and autozone did not have
anything available in stock.

I was shocked that the initial timing had to bumped up to 21ish btc
for me to get the idle down enough to slow the idle to where it feels
lower than before and goes into gear smoother.
Hope I am going down the right path?

I always set the unilite at about 8 btc thought it was ok...i have not had this
car on the road in 20yrs since before I had the internet...WOW time flies!

Going to drive it later today...should be interesting to see the difference between the
no vacuum adv unilite and an old points setup on a BB...dog or no dog?

Hope I am not disappointed...
 

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If you read that article I posted and followed it your engine should be fine.
 

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Dan,
Give it some more initial timing - 8 degrees is not that much.
Usually when you give more initial, it allows you to lower the idle - which closes the primary carb butterflies and ensures you are only on the idle circuit.
 

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Discussion Starter #12
Dan,
Give it some more initial timing - 8 degrees is not that much.
Usually when you give more initial, it allows you to lower the idle - which closes the primary carb butterflies and ensures you are only on the idle circuit.
I'm sorry... that 8 degrees was on my unilite without vacuum adv can...
that I just tookout.
I put a points distributor back in it for now.
 

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Sorry Dan, I mis-read your post.
I'm looking forward to hearing how it runs for you.

Years ago I had a fairly hot SBC 350 in a 69 Camaro. I wasn't using the VA, mainly because I just didn't get the concept, and I heard horror stories of too much timing.
A buddy of mine set the total at 36, which put my initial at 14. Hooked up the VA and that gave me an initial of 24 - it started and turned off no problem, which blew me away. We then set up the total all in at 2600 rpm, re-adjusted the carb and bingo! A whole different car, clean burning spark plugs and throttle response up the whazoo.

I still didn't completely get the concept of VA until I started to frequent this forum.
Good luck
 

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"Years ago I had a fairly hot SBC 350 in a 69 Camaro. I wasn't using the VA, mainly because I just didn't get the concept, and I heard horror stories of too much timing.
A buddy of mine set the total at 36, which put my initial at 14. Hooked up the VA and that gave me an initial of 24 - it started and turned off no problem, which blew me away. We then set up the total all in at 2600 rpm, re-adjusted the carb and bingo! A whole different car, clean burning spark plugs and throttle response up the whazoo.

In your explanation, you have 14 deg/BTDC INITIAL, and 10 deg/Added by full manifold vacuum to the vacuum advance, for a total IDLE timing of 24 deg/BTDC.

Yup, that's exactly what I have been saying for over 45 years, but nobody listens, they all know more than anyone else.
 

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"Years ago I had a fairly hot SBC 350 in a 69 Camaro. I wasn't using the VA, mainly because I just didn't get the concept, and I heard horror stories of too much timing.
A buddy of mine set the total at 36, which put my initial at 14. Hooked up the VA and that gave me an initial of 24 - it started and turned off no problem, which blew me away. We then set up the total all in at 2600 rpm, re-adjusted the carb and bingo! A whole different car, clean burning spark plugs and throttle response up the whazoo.

In your explanation, you have 14 deg/BTDC INITIAL, and 10 deg/Added by full manifold vacuum to the vacuum advance, for a total IDLE timing of 24 deg/BTDC.

Yup, that's exactly what I have been saying for over 45 years, but nobody listens, they all know more than anyone else.
Yep Dave,
I've read your posts over the years and it had made me realize that this friend of mine, who helped me tune my car in early 90's, really understood ignition timing.
BTW about 5 years ago, on my request, you emailed me your write up on VA.
Regards
 

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There are updates to the package, still totally free, and I am going to revise it in a few minutes as well. We have to keep up with the Smith's and Jones's, and not confuse people.
 

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The vacuum has stayed between 14 and 14 1/2 the couple times I checked it.
A bit low from what i have read about it?
Pretty much the same checked on the manifold where tranny mod fitting is
and the front bottom of carb where the pvc plugs in the bottom plate of carb.

I decided to just use the 201-15 can being it was not dead, that was already on it after
going to napa with only one choice available and autozone did not have
anything available in stock.

I was shocked that the initial timing had to bumped up to 21ish btc
for me to get the idle down enough to slow the idle to where it feels
lower than before and goes into gear smoother.
Hope I am going down the right path?

I always set the unilite at about 8 btc thought it was ok...i have not had this
car on the road in 20yrs since before I had the internet...WOW time flies!

Going to drive it later today...should be interesting to see the difference between the
no vacuum adv unilite and an old points setup on a BB...dog or no dog?

Hope I am not disappointed...
Sounds like that vacuum can may have been a vac leak more than it was a vacuum powered ignition control,perhaps that's why it runs better even though it is the same type of part ?
It sounds like you nailed it and I hope it continues to run good for you.
 
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Once you know the specs of the vacuum can you are ordering,
bring along a hand pump vacuum canister with a read out with you.
See the green highlighted mityvac.


I haven't found a canister that met specs from Wells or Standard.

Don't use the dial back timing light, even though it was
presented at tools of the trade. There were hanging
at a Vette site, not Chevelles.com.



Hopefully you'll have more luck than I did.

--Spike
 

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Premium Member
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Once you know the specs of the vacuum can you are ordering,
bring along a hand pump vacuum canister with a read out with you.
See the green highlighted mityvac.


I haven't found a canister that met specs from Wells or Standard.

Don't use the dial back timing light, even though it was
presented at tools of the trade. There were hanging
at a Vette site, not Chevelles.com.




Hopefully you'll have more luck than I did.

--Spike
The only time a dial back timing light will give an incorrect timing flash is when the ignition control is a MSD or a CD type ignition control.These types of ignitions can cause the timing light to flash at the wrong time.
But a normal point or HEI type ignition is not affected by the use of a dial back timing light.
The reason I say "timing flash" is that is all we are doing.The plug gets its spark and as it travels through the wire it causes the timing light to flash.Nothing more.We can then adjust the time when this flash happens by turning the distributors base which alters the timing.
It is a little more complex than that but that is the basics.
Spike make sure you don't lose that adapter I sent you,I don't think I could find another one. :wink2:
 
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I would use the money on a CD box and use the points to trigger it. Set the initial around 20 and see what that does.. I never liked having my idle rpm and coasting resistance dictated by vacuum.. I like having the engines base rpm rock solid, not fluctuating...
 
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