Drilling holes in throttle plates = more air. More air = close butterflies more. Close butterflies more = response to turning the idle mixture screws.
I'm about at the same point you are with mine. I need to drill mine more I think, but it is much better than before. Let me (us) know how it goes.
I believe 0.060", and I would start and adjust the mixture screws and idle speed screw accordingly, pull the carb off and drill the holes larger until the throttle plates were not open as far. Remember your engine wants 14-15 parts air for 1 part fuel, so you'll have to make somewhat drastic changes with your hole drilling. BUT also remember that we're talking about VOLUMES here. So volume of air through a hole can be approximated by just using the formula for AREA. For example, if the 0.060" holes don't do much, you might try increasing by 50% (random figure here). You would think that 50% larger would be 0.090", but because we're dealing with volume here (through an insignificant length of a cylinder, i.e. a hole), 50% greater area ends up being 0.073". Let me know if any of that makes sense or if I confused you. I kinda just confused myself lol.
I think it makes sense. I'll start small and go up. I'm hoping this helps the rich idle, non-adjustability issue when all the carbs are on!!
huh, i had the same experience with a tri-power set up on eBay. it was a mess, i fought it for a couple weeks. after i got it sorted out, the only other thing worth mentioning was it would only run on 3lbs. of pressure.
It took me a while to get mine worked out. I sent them to a "pro" and they were no better. I agree on the end carbs not sealing and getting it to run perfectly on the center carb first. The ends are just dumpers. My Olds end carb base plates would not seal so I bought a set of the new ones off eBay and it has been great! Best of luck!
The size of the engine, the compression ratio, cam size, etc. all play a factor in this. The smaller the engine, compression, and cam, the less likely the plates will need drilled. I have these carbs on a 350 that's 0.060 over @ 10.5:1 with a pretty healthy cam (230*/236* w/ 0.523" lift). So an engine more along these lines is gonna need to take deep breaths, even at idle
One thing I still don't entirely understand, and you can tell me I'm an idiot, but there are 3 carbs, the center has the idle mixture screws, thats the only one that has fuel going into the engine at idle. Let's say the end carbs have a little air going by, basically leaning out the mixture because they're not letting in fuel to go with the air. So I should be able to richen up the center carb with the mixture screws? Or jets? To even out the air/fuel ratio? If I drill holes in the butterflies to let in more air, isn't that leaning it out more? Is the center carb letting in so much fuel at an idle even with the leaking end carbs that it needs more air? What am I missing?
Your butterflies on the primary carb are open so far that the carb is idling off the transition circuit. That's why you can see all those little holes ABOVE the idle mixture screws inside the base. Those should not be showing, so your center carb is unnecessarily rich. Which is why your idle mixture screws are turned all the way in - you were trying to fix that.
When the secondaries are noticeably sucking air, my thoughts are that the engine is pulling fuel out of the boosters as well.
If drilling the throttle plates screws it up, let me know and I'll send you a pair of undrilled ones. Nothing to lose but some time!
I can always solder the hole back up.... Put it back together after drilling holes, small holes. Wouldn't stay running at all. Turned the mixture screws way out, it started to run better. The ends are sucking a little air, but it really doesn't seem to me that its enough to effect much. Covering them doesn't do much. I'm going with that!! Anyway, got it running better then I realized that I was really hot and hadn't eaten anything so I stopped. I'll start again later. Not sure if this link works. STILL messing with carbs:
I can always solder the hole back up.... Put it back together after drilling holes, small holes. Wouldn't stay running at all. Turned the mixture screws way out, it started to run better. The ends are sucking a little air, but it really doesn't seem to me that its enough to effect much. Covering them doesn't do much. I'm going with that!! Anyway, got it running better then I realized that I was really hot and hadn't eaten anything so I stopped. I'll start again later. Not sure if this link works. STILL messing with carbs:
I can always solder the hole back up.... Put it back together after drilling holes, small holes. Wouldn't stay running at all. Turned the mixture screws way out, it started to run better. The ends are sucking a little air, but it really doesn't seem to me that its enough to effect much. Covering them doesn't do much. I'm going with that!! Anyway, got it running better then I realized that I was really hot and hadn't eaten anything so I stopped. I'll start again later. Not sure if this link works. STILL messing with carbs:
Sorry I misled you. PM me your address if you want me to send you some undrilled plates. Soldering will work, too. Can you take a photo of the throttle plates in the base when you pull it off? I want to see how far they are open.
I don't think you misled me at all. Thats part of hot rods, trying different things you know. Sometimes things that work for one guy might or might not work for the next guy. And I'm still not sure the haven't helped. Ive definitely got an issue when the end carbs are on. With even one end on it doesn't run as smooth as it does with just the center on. Tonite I messed with it some more. Took the ends back off, got it running good again on just the center. Keep in mind I still don't know what it will do when I'm driving. This is all being done in the garage/basement. With just the center it runs a lot smoother, seems to have more adjustability in the mixture screws. I'm thinking about making the holes bigger, but I might just need to concentrate on doing something with the end carbs. Here's a pic of the center after I had it on by itself and got it running as good as I could. It was idling around 900 or so.
You have progressive linkage on this. You set the center carb using old time adjusting methods. Turn in your idle adjusting sews until they touch very lightly. Then back them out 3 full turns. Start you rig then adjust each one until it idles smothly. However you need to fix your carbs by rebuilding each one, as you have some problems going on. I ran trip powers for many years on everything from stock to pushing 260lbs of compression and by reading the posts you never do anything to the front and rear carbs except to adjust linkage. They work just like the secondaries on a 4 barrel carb. They have nothing to do with idling, they only work when you open the throttle.
I think the throttle opening looks good like you have it. If it is idling at 900, that is maybe a touch too high, indicating your holes are a bit too big. How many turns from seated are your mixture screws?
The end carb bases have to seal correctly as they seem to be allowing an unçontrolled amount of air into the motor. You have to correctly repair or replace the secondary carb bases, confirm the primary throttle shaft isn't leaking air and be sure all throttle blades properly seat in their bores before adjusting the carbs. Trying to adjust your way out of worn/damaged carbs isn't worth it. Adding more air to the motor via holes in the throttle blades may be premature at this point. Keep on those ends carbs until they have zero effect on idle quality.
You're right. I thought I could make it work by adjusting, adding fuel, air, whatever... I got it running good on just the center then added the ends without the fuel hooked up to them,,just to rule out any fuel issues. Definitely effected the idle. Even though its not a lot of air going by, and a lot better than when I first started this whole thing. So now I can try lapping the butterflies and/or getting some dag213. OR spending 300 bucks or whatever on new baseplates.
Were the ones you got like the ones that vintage speed sells? Speedway sells a kit too, that comes with jets and center carb shaft and butterflies. I guess it would be good to get the kit with the extra stuff that I'll probably need anyway. Just trying to avoid spending more money!!
You know it's been a few years but as I recall I just bought the two bases only? And I would swear they were only $180 or so for the pair? I bought jets from a third party. I will try to dig around and see if I can find the info though it may be a while.
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