Mechanical advance only? Mallory Dual Point? Oh, and a cool pic of my engine!!!

[crazycasey]

Hey Folks,

So after many hours of tinkering, the 230 in my Dodge is finally starting to run like it should, but I have a problem. The Holley 94's that I bought don't have ported vacuum on the base like the stock Carter. Long story short, I don't have the vacuum advance hooked up, and the car isn't running as good up high as I think it should. Is there any way to re-curve the stock distributor to gain more mechanical advance, thus making up for the lost vacuum advance? If not, will swapping to a mechanical advance only distributor from another Mopar flathead gain me anything, and if so which ones will work? Anybody got one of those really trick Mallory distributors for sale. I think one of those would look pretty good in my engine compartment. Oh, and I should also mention that I want to keep the car 6 volt.

Thanks,

Casey

Edited July 13, 2009 by crazycasey

[Dennis Hemingway]

It sure looks nice.

Dennis:cool:

[Rumble1960]

WOW looks great, did you polish your Offy manifold? Were the carbs gold to begin with?

[Bill Ford]

I like that, you done good

[John Mulders]

sure looks nice !

[wills 51]

Sweeeet, Looks good sure would like to hear how it sounds!!!

[Frank Blackstone]

I am inspired to detail my engine and compartment even before I start adding speed equipment. Thanks, Frank

[Plymouthy Adams]

the mechanical curve can be changed but you will suffer from lots of light throttle ping if you were to advance it into the realms of the higher advance timing that the vacuum advance reaches. The sheer fact that its vacuum operated ensures this condition will not exist during WOT/accelerator as the loss of vacuum retards the timing back to the mechanical preset.

I am not familar per say with the 94 carb..have you thought about rigging a switchable vacuum source to the distributor for when you are crusin..that is when you need the full timing advance..

[crazycasey]

I don't mean to argue with you Tim, but I thought that since the Mopar vacuum advance's vacuum source comes from above the throttle blades that it will only give you full advance at WOT. Having advance at cruise, but none at WOT would make sense if you hooked your vacuum advance to manifold vacuum, but I don't think the car would run right. Will somebody please correct me if I am wrong? I've read so much about all this recently that it makes my head spin.

Oh, and to Rumble1960, yeah I did polish the Offy manifold...it took forever, as they are pretty crappy castings. Also, the carbs I had plated, but that was supposed to be an OEM style finish. I imagine they will fade quite a bit with some heat-cycling.

Thanks for all the compliments though...I'm pretty stoked from the response.

[Plymouthy Adams]

now you are confusing me comparing the source for a Mopar carb when you state above you are running 94 series carbs without a vacuum port on the flathead that does in fact have the vacuum advance distributor..is this correct...if so..then your advance will be taken off the maifold vacuum..I believe this is typical of GM and the original application of this carb.....thus the loss of vacuum during acceleration will retard the timing to prevent the ping..the mechanical curve now does it thing yet again to regain speed and power and as you return to even speed the vacuum will stat to again rise and increase the total advance

I threw in the part on switchable as I gathered you wanted a bit of control...we are not talking ported vacuum in the case of the 94 carb..

maybe I read your first statement wrong..this is what I gather from the GM sites and the 94 carb...I do't like the total vacuum idea at idle myself..thus the switch..??

Edited July 14, 2009 by Tim Adams

[crazycasey]

Tim,

I am running two Holley 94's with the stock Mopar vacuum advance distributor. I made the comparison to the Mopar carb, because I was trying to understand how the stock system worked, before I stuck the two Holley's on it. My distributor was designed to work with the Mopar carb, which pulled vacuum from above the throttle blades, not below, right? If I use manifold vacuum with the new carbs, won't I be sending the distributor a reverse signal? I am actually basing all of this on something that you wrote in another thread back in '07:

The engine timing needs to advance in relationship to speed and therefore the vacuum should be venturi ported..as the throttle valve opens the increase in air over the small port increases the amount of vacuum. To port ones advance off the manifold works in reverse to your needs...at steady idle you have steady pull hopefully in the 17-21 range, and on decel your vacuum is at its max..23-25 inches...thus you are max on your advance...if you accelerate, you lose your vacuum and you advance is lost (retarted)..be sure that you are venturi ported and that you base line timing is set with no vacuum.

Finally, if I hook the vacuum advance to manifold vacuum, which pulls 16-19" at idle, that means that I will have my base timing plus 10 degrees vacuum advance timing at idle. I think a lot of GM distributors work that way, but I thought the mopar distributor was set up different.

[Plymouthy Adams]

that is correct and the manner in which I wrote my reply for your situation , the previous thread I wrote was in view of the original ported mopar carb..yes this can be confusing when utilizing mix and match components...with manifold vacuum the timing at idle will be increased thus the possibility to control this with a switch similar to say OD where it will kill the vacuum at idle by linkage/throttle lever activation...that would be one solution to your porblem of running carbs without ported vacuum and still benefit from the max vacuum at sustained speeds and yet have zero vacuum at idle..the area in between will change porportionally with the manifold vacuum as it varies under load and acceleration...

[crazycasey]

:confused: :confused: :confused:

Actually...I get what you are saying. I was just hoping there was an easier way. I know a couple of guys over on The HAMB say the Mallory Dual Point is the way to go because it does away with the vacuum side of things altogether. They're really hard to find though. Is there another distributor I could use that is mechanical advance only, that won't have the part throttle pinging issues I would get recurving the stock distributor?

[Plymouthy Adams]

I know your disappointment..but I am not aware of a cure all distributor for this application..of course I have not really investigated ...the purely mechanical distribuor will be x-degree at x rpm..so if your cruise is at 2400 now and later on the big road 3700 you will not have the max advane your engine needs to burn the leaner mixture you get at higher sustained speeds..you get only what is programmed (spring curve) tuned by the builder..most of the after market performance minded items advertised is just that..performance where you gun it and go and max performance is your acceleration from zero through top end..the cruise and economy that is afforded by the vacuum is pretty much out the window..howver..performance you should be okay across the spectrum with the mechanical..you will not captalize on effieciency is all

[n1gzd_plymouth]

wow, your engine looks awesome!!

Rebecca

[Don Coatney]

If dual points is your objective there are other options besides the Mallory distributor. I have converted my stock distributor to dual points and I have a vacuum advance. I am not sure why the HAMB guys say the Mallory distributor without vacuum advance is the way to go.

[Plymouthy Adams]

the distributor is not the issue..it is the lack of ported vacuum in his intended setup..he is hoping to find a mechanical distributor with a curve that will suit his requirements...performance wise it will..economicaly effecient..not so I am thinking..could result in 3-4 MPG less...possible pinging on light throtle say overpasses and bridges etc

[crazycasey]

Yeah, what Tim said. So Tim, I was rolling around the idea of your manifold vacuum with a switch source for the vacuum advance. So I wouldn't have any vacuum until a preset throttle position when my switch would activate, but then wouldn't the vacuum signal still be backwards of what I wanted? The switch would activate at say, 1/4 thottle opening, but manifold vacuum would still be pretty high, and the distributor would go to near full advance, and then it would gradually fall of as I accelerated, leaving me with 0 advance at WOT, which is where I would want full advance right? I'm just trying to wrap my head around the idea, before I accept/dismiss it.

[Plymouthy Adams]

well..the vacuum will be present but if under acceleration the vacuum will be less..it is this load varying vacuum that is going to somewhat substitute for the ported vacuum and keep the timing under acceleration that of the preset curve and then when constant speed..revert to further vacuum advance for economy

[dezeldoc]

why not find some stiffer springs or heaver fly weights for the mech advnce, that will bring the rpm up that it will start to come in at.

[crazycasey]

dezeldoc,

That is exactly what I was thinking, but I've never torn apart a distributor before. I couldn't find any tech posts on recurving the distributor. I was hoping that somebody here could give me some more info. Is it just trial and error? Play with spring tension, and fly weight, and check your advance? Can you modify the distributor to give more TOTAL advance, or can you just alter where it comes in? Total vacuum and centrifugal advance at 2500 rpm is supposed to be between 29-37 degrees, but only 12-16 of that is centrifugal, and 2 is supposed to be initial. I'd need to at least double the amount of total centifugal advance at peak to make up for not having vacuum advance, which is why I was thinking that a simple swap to a non-vacuum advance distributor would be a good starting point. I just don't know which ones I could swap between.

[dezeldoc]

We used to recurve the chebby ones years ago and could pretty much make it do anything we wanted. of course my dumb butt went and sold the dist machine:mad: i have not been into one of these, maybe i will go disect one and see what would be involved with it.

[crazycasey]

Well, if nothing else it would make for a great tech posting.

[Plymouthy Adams]

the curve of the distributor is to be set by bending the tabs the springs connect to or replacing stiffer/lighter springs..the use of the dist machine is necessary to create the timing curve with any percision..the dist data is provided in the manual for the time of engagement to how much per RPM and then at the end the total advacne by vacuum which takes the timing further into the advancement realm..special ground cams will have a different curve and usually the only need for altering the stock distributor..

[crazycasey]

Does anybody know if a distributor from a 1938 Dodge 230 will fit the 1953 motor? I found one of these and am assuming that it would have a more aggressive mechanical advance curve since it doesn't have vacuum advance at all, but would love it if somebody can offer their opinion here. I'm thinking that this might be a good fix, at least temporarily, until I can find, sort out, and rebuild another pair of Holley's that have the proper ported vacuum connection.