DEBrahms

Guys, I need your opinion on whether or not I should hook up the vacuum advance on my 4-speed '58 2x4 270 283. As it stands now, there is no connection between the vacuum can and the vacuum port on the front carb. They're both capped. I'm a dunce when it comes to things like this, but several guys pointed out the missing connection at a shine and show gathering last night, telling me that I should definitely make the connection.

The vacuum can on my distributor has these numbers on it: MS 148_15. According to ST-12, this looks like a fuelie distributor, since it has the can on it. The car was originally a fuelie, but was converted to 2x4. My questions:

- What's involved in connecting the vacuum advance? Is it as simple as running a rubber hose from the distributor vacuum can to the front carb port? I imagine that the timing may have to be changed, too. (This is where I would get nervous.) There's no vacuum port on the rear carb, right?

- Should I leave well enough alone? (This is my gut instinct.) It starts right up, idles fine (no stalling), doesn't overheat, and has plenty of power. I get 14 mpg around town with plenty stop and go. Since it ain't broke, should I fix it?

Thanks, guys. I always appreciate your help.

Ron Miller

Get a vacuum hose, put a plug in it, and connect both ends to the carb and the vacuum pot on the dizzy. If you're not having any problems, why create some if somebody already has everything lined out for the setup you're running.

PS: Don't tell your buddies what you've done, that way both you and them will be happy, and they'll be sure to notice how much better your car runs now that you've got the vacuum connected as it should have been.

stingrayl76

Set your initial timing to spec, hook up a vacuum line from manifold vacuum to the vacuum advance and reset the idle RPM.

KC John

I don't think GM would have put vacuum advance in their distributors if it wasn't needed. If you do hook it back up, make sure you hook it to full manifold vacuum and not ported vacuum. The ported vac connection is above the throttle plates and the full vac is below the plates. You can also access full vac directly from the manifold if you have a plug there.

Mark Lovejoy

'58 290hp FI did not have a vacuum can on the distributor. I'm not sure about the 250hp version.

If the distributor you have has a vacuum can on it, use it.

Dave Tracy

You will find that the engine rpm will increase. You may find that the car will perform better also.

knockbill

i may be wrong, but, i thought teh 270 hp engines used a dual point distributor,,,,

Dan Hampton

They did.

JohnZ

All you need is Paragon's #755 2-piece vacuum fitting; it threads into the rear of the baseplate on the rear carburetor, replacing the hex plug that's there now.

Pilot Dan

They did use an 0891 dual point distributor which as I recall does NOT have a vacuum can on it at all. OP, what distributor are you using??

B/T/W, I recognize the MS 148-15 can you refer to as the factory stock can for a single 4BBL distributor. Maybe that is why yours was plugged. Pilot Dan

DEBrahms

Guys, thank you for all your insights. I'm going to try to post a pic of my distributor and front carb vac port, which might help you all to understand my situation better. I'll do that at the end of my comments here. Responding to your comments and questions:

- Lee (leadking): Yes, my two fours have progressive linkage. The two Carters aren't the correct carbs, though. The front one is a 6-1271, which I understand is from a '57. The rear carb is a 6-1672, which is from a '63 or later. The car is a cobble of various years' components.

- Ron (Ron_Miller): LOL! Trust me; I've considered that approach. If it ain't broke . . . I have to wonder, though, why whoever restored this car set it up this way.

- Dave (stingrayl76): Where is the manifold vacuum port? I looked for one but couldn't find it. My manifold is a 3739653.

- John (KC_John): As I mentioned to Dave, I see only one other non-distributor vac port, and that is on my front carb. I'll try to post a pic of that below.

- Mark (Mark_Lovejoy): On page 6Y-2 of ST-12, you can see a pic of my distributor. It's clearly the FI, dual-point unit (as mentioned by knockbill and Dan Hampton) on the right. It shows the exact vac can that mine has, including the access plate in the front.

- John (JohnZ): Thank you! That's a very clever solution.

- Dan (Pilot_Dan): I couldn't find the part number tag on my distributor but will try to post a pic below. As I mentioned above, ST-12 shows the dual-point, FI distributor with a vac can.

Here are those two pics. I always have trouble posting pics here, even though I follow the forum tutorials exactly. If they don't appear, please click the URLs. Other times, kind souls have posted and sized my pics for me. I really appreciate that.

First, my distributor:



URL: http://i1212.photobucket.com/albums/...s/IMG00039.jpg

Next, my front carb's vac port:



URL: http://i1212.photobucket.com/albums/...s/IMG00040.jpg

Thanks, guys, as always.

Pilot Dan

That distributor is NOT correct for dual four barrels. If it were for a Fuelly, it would have a hookup for the fuel injection pump drive cable which I don't see in your picture. Nothing wrong with keeping what you have in there now as long as it is working for you.

As a related question, does anyone know why the dual point distibutors lacked a Vacuum advance??? Might be a question for Lars, or John Z. The answer might be the reason why your advance is plugged. Pilot Dan

DZAUTO

Up through 62, ALL the solid lifter engines (which were either FI or 2x4/one AFB in 62) had mechanical adv distributors ONLY. Only the hyd cammed engines got a vacuum adv dist.
The mech adv dist engines had a more aggressive ign curve built into their mech dist-------------------which I have never really understood!
In 63, ALLLLLLLLL engines got a vacuum adv dist, including the FI engines. For daily/street driving, a vac adv dist is much more compatable than a straight mech adv dist. For many years I ran a mech adv dist (62 dist) with the FI unit in my 56, and always thought a vac adv dist would work better for street driving. Finally, I swapped the 62 mech adv FI dist for a 65 vac adv FI dist. WOW, what an improvement!

Tom Parsons

midyearvette

i am doing my best to stay out of this thread and all the responses....man o' man!.....i will just sit on the sidelines and simply

good luck to all......

DEBrahms

Dan, here is a pic of my distributor taken from page 198 (6Y-2) of ST-12. It's the one on the right. Is that a vac can on it or is that the FI pump drive you mention?



URL: http://i1212.photobucket.com/albums/...s/gijfbhjb.png

Ironcross

I figured you would straighten them out, and you did........

Ironcross

High performance engines are successfully run without a VC can including the L88`s and A990`s....The aftermarket high performance ignition companies such as Mallory was one of the leaders in dual point distributors and did not incorporate VC cans with them....

JohnZ

If it looks like the one on the right, it's a fuel injection distributor. Does it have a tach drive connection on the back side in addition to the fuel pump drive connection on the front? What's the part number on the square plate attached with four screws?

Ron Miller

That's one of the reasons I suggested, only partially "tongue in cheek" to put a plugged hose on yours, satisfy the part-time onlookers, and run it just as you have been if it's been doing fine all these years. In most cases, the way parts get swapped and changed over the years, many folks wind up with distributors, carburetors, cams, heads, pistons, and other components that weren't originally specified to be assembled together. This being the case, there's no way to go back to an "original spec", there isn't any for that particular assembly of parts!!

Should you wish, it'd be simple enough to connect the vacuum advance and see what kind of differences it may make, could be positive or could even be negative! In any event, before I made any I'd certainly see where the timing, etc., is set at present JUST IN CASE you want to go back to what you had . . . . . . (or, put in a "plugged" vacuum line!!!)

JohnZ

That's because Mallory was focused on "race" applications, which don't need vacuum advance. Normal street operation is a different ball game, and needs vacuum advance. See my "Timing 101" paper.