racerx Posted November 17, 2017 Report Share Posted November 17, 2017 I feel u been there many times. At times its best to take a break from our project 1 Quote Link to comment
mainer311 Posted November 17, 2017 Report Share Posted November 17, 2017 You could be in my shoes: gearing up to rebush a worn throttle shaft in my Hitachi. 1 Quote Link to comment
racerx Posted November 17, 2017 Report Share Posted November 17, 2017 Btw. D.p. did u check ur adapter plate, maybe its warp. 1 Quote Link to comment
wayno Posted November 17, 2017 Report Share Posted November 17, 2017 Btw. D.p. did u check ur adapter plate, maybe its warp. He has an adapter, it's just not a plate, it's like the one in the photo below. If you look close at mine you can see it is slightly bent, maybe his is bent also and he didn't check it before installing it, he is new to classic vehicles and the stuff we automatically do and don't even think about telling him to do isn't getting done, to use this adapter above I will have to seal it real good. 1 Quote Link to comment
mainer311 Posted November 17, 2017 Report Share Posted November 17, 2017 Why don't you just mill it flat? 1 Quote Link to comment
d.p Posted November 17, 2017 Author Report Share Posted November 17, 2017 I would have to take it off to check it. Quote Link to comment
racerx Posted November 17, 2017 Report Share Posted November 17, 2017 I know this from experience if its not flat, it can cause a vacuum leak. What's worse is the 2 adapter plates. And u can't overtigthen them, it can get warped. One way to tell is spray some carb cleaner around the carb base, if rpm goes up, there's a leak and if you tighten it and still leaks, then strong possibility its warped. I would also spray carb cleaner around intake area. I'm just saying a lot of problems we faced w these Datsuns is simple. Good to do a diagnosis first before replacing parts. 1 Quote Link to comment
wayno Posted November 17, 2017 Report Share Posted November 17, 2017 Why don't you just mill it flat? Right now it is loose and I am not using it, I do plan to use it on my L320 when I get back to that build, the Weber carb with adapters sits too low to modify and use the stock air filter on it, I believe that using that tall adapter will get it high enough to use a modified 320 air filter or something similar. 1 Quote Link to comment
datzenmike Posted November 17, 2017 Report Share Posted November 17, 2017 Pull the vacuum advance hose off the distributor and try the idle. 1 Quote Link to comment
d.p Posted November 18, 2017 Author Report Share Posted November 18, 2017 Fucked with it a little more today. Pulled vacuum advance and it didn’t make a difference. Plugged PCV with my finger didn’t mane any difference. So I pulled the plugs and they were fouled (dry black). Put new plugs in (didn’t gap them) and turned in the mixture screw and it idled much better drove it around and it didn’t die on decel. Felt like it had good power too.... fingers crossed it stays that way.Not sure how or why I keep fouling plugs but just going to buy a bunch of them. Any ideas? -Jb weld dizzy mount seems to be holding so no plans to replace timing cover. -Weber sent me a new carb but not sure I need to. -Got an el dizzy with the proper mount but no plans to install that. -Also got a tachometer that crash gave me which I will most likely install soon. Quote Link to comment
Crashtd420 Posted November 18, 2017 Report Share Posted November 18, 2017 It's possible you may need to adjust the main jetting on the carb.... This is where a wide band o2 or a dyno shop comes in handy.... 1 Quote Link to comment
wayno Posted November 19, 2017 Report Share Posted November 19, 2017 You know that short drives do not give you a good sample of how the engine is mixture wise, it's always going to be rich, what counts is when you take it on the freeway for a while, I check my plugs every 6 months or so and adjust accordingly, but I have dual SUs. I adjusted the Weber on my 320 by turning the screw way out till it was obviously to rich, then I turned it in till it started to not idle so good, then I kept going back and forth till I found the best idle in the middle of the two extremes. 1 Quote Link to comment
racerx Posted November 19, 2017 Report Share Posted November 19, 2017 If you backed off mixture screw, you are richening the fuel mixture. Are you sure u know how to adjust your carb? 1 Quote Link to comment
d.p Posted November 19, 2017 Author Report Share Posted November 19, 2017 yeah turned in, thats what I meant to say. Its about 1 full turn in from bottoming out. Quote Link to comment
racerx Posted November 19, 2017 Report Share Posted November 19, 2017 What I do and seems to work is when I adjust my mixture screw, not more than 1.5 turns out, I take the car for a test drive, not just the streets but freeway also and pull over and check my plugs. You don't need AF gauges! Back in the days, the would b mechanic would smell the exhaust, check spark plugs and pay attention to how many turns w screw driver. Plugs should be like tan color, not too white, lean, and not sooty black, rich...u want in between. Been doing adjusting on old carb cars, American and Japanese. If u r not sure how to go on line or you tube how to adjust 32.36 weber, very easy to do. 1 Quote Link to comment
d.p Posted November 19, 2017 Author Report Share Posted November 19, 2017 So drive it around, check plugs and adjust mixture screw as necessary to get white/tan plugs? Question though when I adjust the mixture do you need to adjust the idle speed screw as well? In my experience when I adjust the mixture screw it either raises or lowers the idle so then I have to adjust the idle speed screw. Quote Link to comment
racerx Posted November 19, 2017 Report Share Posted November 19, 2017 Before you do this, did u check for vacuum leaks..previously I mentioned to check your carb adapter for flatness. You can adjust your carb as many times as u want but if u have a vacuum leak, it would not matter. 1 Quote Link to comment
DanielC Posted November 19, 2017 Report Share Posted November 19, 2017 Everything works in conjunction with everything else. Valve adjustment will affect carb tuning, and so will ignition timing. When the rpm goes up, that will add ignition advance. If the throttle is open above idle, that will add vacuum advance. Adding ignition advance will increase idle speed. Because a even a very small vacuum leak is a lot of air in relation to the amount of air that goes through a carb at idle, you must get rid of all vacuum leaks. I cannot stress the importance of getting rid of vacuum leaks enough. Adjust the valves. Check them again when the engine is hot, not warm, hot. Check the compression, it must be good to get a good carb tune. Set the ignition timing. 10 degrees BTDC is a factory setting. There cannot be any mechanical advance, or vacuum advance when setting the timing. If the engine is running, it must be below 750 rpm. On old engines, you must also check the mechanical advance below the timing points plate in the distributor. Make sure the springs that retract the centrifugal advance are not broken, disconnected, or in other ways malfunctioning. Clean the old grease off the timing parts, make sure the weights move freely. If your exhaust is quiet enough, and you know what spark knock sounds like, you can set the initial timing a little more than 10 degrees BTDC. Spark knock destroys engines. If you are not sure of what detonation sounds like, I do not recommend using that to set the timing. if you can recognize spark knock, advance the timing until it barely knocks, and retard it about 2 degrees. After checking all that, then you can tune the carb. I strongly suggest you get a vacuum gauge to adjust the carb. It will show you changes in engine tune you cannot hear. You also need a low RPM tachometer, you must keep the engine RPM below about 750 RPM, or mechanical advance will start coming in on the distributor. As you tune the mixture screw in the throttle body of the carb, you need to adjust the throttle stop screw to keep the engine RPM below 750. If the throttle stop screw loses contact with the throttle, and you cannot lower the idle speed, check the throttle cable for slack. Check also that the secondary of the carb closes all the way. Check for vacuum leaks. Your engine should idle around 20 inches of vacuum, if it is a pretty normal stock engine, at sea level. If the vacuum is significantly less than that, you have a problem you need to find the root cause of. In my mind, you are fighting a vacuum leak. 1 Quote Link to comment
wayno Posted November 20, 2017 Report Share Posted November 20, 2017 I cannot get a decent idle that low Daniel, when I try to adjust my dual SUs with the idle that low it dies when I disable either of the carbs to adjust the other one, not every ones engine is going to idle that low even with a new carb. I prefer between 800 and 900rpms myself, it doesn't die all the time. 1 Quote Link to comment
mainer311 Posted November 20, 2017 Report Share Posted November 20, 2017 I can get my L16 to idle at 650. In fact, my roadster idles that low with SU’s... 1 Quote Link to comment
racerx Posted November 20, 2017 Report Share Posted November 20, 2017 Mine is happy at around 800 rpm. 1 Quote Link to comment
DanielC Posted November 20, 2017 Report Share Posted November 20, 2017 The problem with too high of an idle sped is that mechanical advance starts to come in. With advance coming in, the idle speed increases even more. That makes it very hard to get a consistent idle speed. 1 Quote Link to comment
d.p Posted November 20, 2017 Author Report Share Posted November 20, 2017 to test vacuum at idle I can just get a vacuum tester/gauge and put it on the vacuum advance off the base of the carb? normal is 20lbs at idle? And the truck will idle below 750 but super rough and lopey (sp?). Quote Link to comment
DanielC Posted November 20, 2017 Report Share Posted November 20, 2017 Hooking a vacuum gauge to any port on the carb may not give you the correct vacuum reading. There is a port in the rear runner of the stock intake manifold. It usually has a fitting with a 1/8 hose connection. Quote Link to comment
racerx Posted November 20, 2017 Report Share Posted November 20, 2017 Has to be intake. Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.