ArdWrknTrk Posted February 22 Share Posted February 22 Immediate thoughts/solutions are to find a NOS vacuum restrictor or create a restriction in vacuum by using a smaller diameter hose, something like the one that runs to the HVAC controls, see if that provides sufficient restriction to keep the idle where it needs to be until warm. The other option is to use a vacuum delay valve between the VCV manifold port and distributor when hot so the change is not abrupt. Looks like I will need a vacuum delay valve to run EGR anyway so I need to find a source for it. The thermal valve is a wax pellet that expands inside the threaded in portion I don't think 'abrupt' is a problem... What would be good is to determine what each colour means in terms of orifice. Then you could just use carburetor jets or something else analogous in their stead. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 22 Share Posted February 22 The thermal valve is a wax pellet that expands inside the threaded in portion I don't think 'abrupt' is a problem... What would be good is to determine what each colour means in terms of orifice. Then you could just use carburetor jets or something else analogous in their stead. Maybe "abrupt" is the wrong word. But the thermostats in our trucks also use a wax pellet and they open up pretty quickly according to my temp gauge. So far I'm not finding anything that shows what the orifice sizes are. But this guy said the one on his 'ard wrkn truck is blue. I'll keep looking. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 22 Share Posted February 22 Maybe "abrupt" is the wrong word. But the thermostats in our trucks also use a wax pellet and they open up pretty quickly according to my temp gauge. So far I'm not finding anything that shows what the orifice sizes are. But this guy said the one on his 'ard wrkn truck is blue. I'll keep looking. 12A225 Restrictor assy, (distributor vacuum) Here are the part numbers so they can be found in a search: D7AZ 12A225-B Blue D9ZZ 12A225-A Yellow D6DZ 12A225-A Red E1TZ 12A225-A Orange And here is the table from the master parts catalog. Note that this doesn't show the 460, but all of the applications I saw used the blue one for it. And still no indication of the orifice size. Link to comment Share on other sites More sharing options...
Ifitaintbroke Posted February 22 Share Posted February 22 It's possible to tune for ported if you're going to recurve the distributor and install a new vacuum advance, but at that point one of Scotties custom curved distributors is only a few bucks away. But not back in the day when the advance was $15 and the springs 2. A Reman distributor was $35 and you only needed a welder or some brass tube from the hobby shop to tighten up the slot. I ended up having Scotty curve one for me. I've never curved a dizzy and didn't want to mess it up. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 22 Share Posted February 22 Maybe "abrupt" is the wrong word. But the thermostats in our trucks also use a wax pellet and they open up pretty quickly according to my temp gauge. So far I'm not finding anything that shows what the orifice sizes are. But this guy said the one on his 'ard wrkn truck is blue. I'll keep looking. Yep, mine is blue. I think I even have a picture of it... Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 22 Share Posted February 22 Yep, mine is blue. I think I even have a picture of it... I think the only way to figure out what jet to use instead of an actual restrictor is to do it empirically. But I don't fully understand how the restriction works, so don't know how to go about it. I would think that restricting the vacuum would just slow the onset of advance, not reduce it. I say that because in my Parallel Systems class we were taught that you can model a mechanical system with electrical components. And I would think that a restriction pretty closely aligns with a resistor. And the voltage on each side of a resistor will be the same unless there is some flow of current. But in my memory a good vacuum advance doesn't have any leakage, so there shouldn't be any flow. What am I missing? There has to be something I'm missing 'cause the restrictors work... Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 22 Share Posted February 22 I think the only way to figure out what jet to use instead of an actual restrictor is to do it empirically. But I don't fully understand how the restriction works, so don't know how to go about it. I would think that restricting the vacuum would just slow the onset of advance, not reduce it. I say that because in my Parallel Systems class we were taught that you can model a mechanical system with electrical components. And I would think that a restriction pretty closely aligns with a resistor. And the voltage on each side of a resistor will be the same unless there is some flow of current. But in my memory a good vacuum advance doesn't have any leakage, so there shouldn't be any flow. What am I missing? There has to be something I'm missing 'cause the restrictors work... Empirically, I can take my set of number drills and come close to a size for my blue restrictor. Whether that's best, for a 300, I can't say. 🧐 Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 22 Share Posted February 22 Empirically, I can take my set of number drills and come close to a size for my blue restrictor. Whether that's best, for a 300, I can't say. 🧐 That would be a start. What I was thinking was to put a dizzy on the bench and connect my Mity Vac to it via a VREST. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 22 Share Posted February 22 That would be a start. What I was thinking was to put a dizzy on the bench and connect my Mity Vac to it via a VREST. Is that going to prove that you can pump fast enough to keep up with the restriction? Jets are jets. It's pretty much all about how much it can flow at a given depression. And that's dependent on the size of the hole. (and how smooth it is) Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 22 Share Posted February 22 Maybe The plate on there, I do hope thats the case. But I couldn't find anything!! I'll scrub everything well tomorrow and send more pics. (The pics above show the original timing set...) Cloyes own catalog shows C3079X as the recommended chain for BBF. The other with only 1 keyway that we discussed doesn't show up on their catalog, probably discontinued. Rockauto shows to have it, but its probably old stock or possibly returned. I am paying about $40 for the set with 3 keyways. It has 2 extra key ways that I will ignore. I will install it with the key way with the timing mark straight over it. Have a look at this guy (Mike's) video where I start at about 15:26 Can you see where the water pump was? Does it look all ribbed with voids behind the impeller? Link to comment Share on other sites More sharing options...
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