TheGeneral Posted January 10, 2022 Author Share Posted January 10, 2022 hissing like a snake! awesome. that's a good sign. do you have a vacuum gauge? hooking that to an intake vacuum port will give you intake vacuum and then you can possibly tune the carb with that info. if you have no vacuum leaks you should see 17-21in of mercury (hg) on the vacuum gauge. hissing strongly tells me that there is likely no vacuum leaks at the work you have already done. you are making positive steps. hissing strongly also tells me that it is now a little rich as there is enough fuel to make a good fire, throttle response is probably good too. if the carb had been attempted to be tuned to a previously existing vacuum leak that is what i would expect. I guess I have to buy one tomorrow. Two more things I noticed were, it ran BETTER cold (1st thing after overnight), almost calm in fact-- but got progressively worse as it heated up. Also, my temperature gauge got higher than normal--ie, rather than gauge topping off at about 1/3 above flatline and then only going a bit over that no matter how long I drive it (never reaches 1/2way line--almost, but not quite--even on a multi hour trip). It went all the way to the halfway line and then over, just while it warmed up, and did not go down until I started driving it...but even then it was a bit higher than normal. That concerns me. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 10, 2022 Share Posted January 10, 2022 1.) Because I am only about 85% certain that I am reading it correctly.... 2.) "she" lol 3.) based on Model Application code info page I believe my calibration code is F150 - - 2/W/D—M/T—Calif. 4-51S-R02 392 (1985 4.9, 2WD, Manual transmission, California) 4.) Matt in Tn, you are right, a more thorough troubleshooting diagnosis would be helpful but I am not going to make things worse for myself by unplugging everything at once. Now, it is possible that an unseen line crack developed somewhere as a result of taking it apart etc, but the reason I think it is likely a mistake on my part is that if the manifold leak(s) are now gone (they are) and nothing else has changed, then it should be running better, not worse. Ok, so you've found the right calibration code, as shown below. Tomorrow I'll scan that page in and post it, along with a close-up of the vacuum routing. CALIBRATION PARTS LIST NO. 392 (Calibration No. 4-51S-R02)-6 Cyl. 300 C.I.D. (4.9L) 1984/86 F150 - - 2/W/D-M/T-Calif Link to comment Share on other sites More sharing options...
mat in tn Posted January 10, 2022 Share Posted January 10, 2022 Ok, so you've found the right calibration code, as shown below. Tomorrow I'll scan that page in and post it, along with a close-up of the vacuum routing. CALIBRATION PARTS LIST NO. 392 (Calibration No. 4-51S-R02)-6 Cyl. 300 C.I.D. (4.9L) 1984/86 F150 - - 2/W/D-M/T-Calif that too is a positive sign. it runs better cold. being cold is when it needs more fuel! the exact reason it has a choke. as it warms up the choke must relax, be pulled off to allow it to lean out and only draw the needed amount of fuel. at idle that amount is from a slight amount of air through the throttle plate combined with an amount of fuel rich air through the idle circuit below the throttle plate. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 10, 2022 Share Posted January 10, 2022 Ok, so you've found the right calibration code, as shown below. Tomorrow I'll scan that page in and post it, along with a close-up of the vacuum routing. CALIBRATION PARTS LIST NO. 392 (Calibration No. 4-51S-R02)-6 Cyl. 300 C.I.D. (4.9L) 1984/86 F150 - - 2/W/D-M/T-Calif Well, memory would be a good thing to have. Turns out that I have the truck-related bits of the 1985 Emissions Fact Book on the site at Documentation/CALIBRATION INFO & PART #'S and then the 1985 Emissions Info tab. So you can find all of the info there. However, for the 4.9L engines I've put a link in the Index. And I put a link specifically to your calibration code. (I'll put in links to the other engines later, probably during the football game tonight.) Also, since my scans at 600 dpi and 50% contrast aren't crisp, I scanned that particular page at 1200 dpi and 80% contrast, which gives a much crisper rendering. (However, it is also much larger, file size, so I don't want to do that with every page.) Then, realizing that it is hard to read the vacuum routing turned 90 degrees, I rotated and cropped that page to give the view below. But, even cropped to just the vacuum routing that is a 2.1 meg file, and that won't post here. So the one below is downgraded to .9 meg to get under the 1 meg limit. However, if you want the high res file you can download it here. Hope that helps. Link to comment Share on other sites More sharing options...
Machspeed Posted January 10, 2022 Share Posted January 10, 2022 I guess I have to buy one tomorrow. Two more things I noticed were, it ran BETTER cold (1st thing after overnight), almost calm in fact-- but got progressively worse as it heated up. Also, my temperature gauge got higher than normal--ie, rather than gauge topping off at about 1/3 above flatline and then only going a bit over that no matter how long I drive it (never reaches 1/2way line--almost, but not quite--even on a multi hour trip). It went all the way to the halfway line and then over, just while it warmed up, and did not go down until I started driving it...but even then it was a bit higher than normal. That concerns me. Man, I feel for you. I had some issues sometime back with a bad reluctor pick up coil that gave me all kinds of grief. It would sit and idle nicely but if I gave it any kind of gas, it would bog and backfire. Incredibly frustrating! With patience, and much help on this forum from Jim, Gary and a couple of others, we figured it out. For me, the road block was a brand new faulty pick up coil. It's new, it can't be bad! Believe it or not, I went through two of those brand new faulty coils and then said screw it and went to another brand at a different auto store. Regarding the hissing, my experience with hissing is a vacuum leak. When I was doing all that work to my engine sometime back, I left the brake booster hose off and had a huge hissing noise and a rough running engine. Be advised, I'm novice at best. Others on here know far more than me. Try and be patient and realize that you're learning. When YOU get it fixed, it will be a nice accomplishment and you will feel the satisfaction of it all. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 10, 2022 Share Posted January 10, 2022 Man, I feel for you. I had some issues sometime back with a bad reluctor pick up coil that gave me all kinds of grief. It would sit and idle nicely but if I gave it any kind of gas, it would bog and backfire. Incredibly frustrating! With patience, and much help on this forum from Jim, Gary and a couple of others, we figured it out. For me, the road block was a brand new faulty pick up coil. It's new, it can't be bad! Believe it or not, I went through two of those brand new faulty coils and then said screw it and went to another brand at a different auto store. Regarding the hissing, my experience with hissing is a vacuum leak. When I was doing all that work to my engine sometime back, I left the brake booster hose off and had a huge hissing noise and a rough running engine. Be advised, I'm novice at best. Others on here know far more than me. Try and be patient and realize that you're learning. When YOU get it fixed, it will be a nice accomplishment and you will feel the satisfaction of it all. In my experience hisses are usually vacuum leaks. However, Welder Scott's 2150 hisses, and I don't know why, although we are going to work on it soon and I may find out. One way to find out if it is a vacuum leak is to spray brake or carb cleaner around the area where the noise is coming from. If it is a vacuum leak the engine will speed up. We did that with Scott's truck and proved it isn't a vacuum leak. So it must be the carb. So you might try that. Link to comment Share on other sites More sharing options...
Machspeed Posted January 10, 2022 Share Posted January 10, 2022 In my experience hisses are usually vacuum leaks. However, Welder Scott's 2150 hisses, and I don't know why, although we are going to work on it soon and I may find out. One way to find out if it is a vacuum leak is to spray brake or carb cleaner around the area where the noise is coming from. If it is a vacuum leak the engine will speed up. We did that with Scott's truck and proved it isn't a vacuum leak. So it must be the carb. So you might try that. That's good idea, Gary! Yes, spray around the base of that carb and even into the carb and see if it does not change anything. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 10, 2022 Share Posted January 10, 2022 That's good idea, Gary! Yes, spray around the base of that carb and even into the carb and see if it does not change anything. Into the carb should speed it up, but won't prove there's a leak. Another trick is to use a piece of hose as a stethoscope to listen for leaks. Link to comment Share on other sites More sharing options...
mat in tn Posted January 10, 2022 Share Posted January 10, 2022 That's good idea, Gary! Yes, spray around the base of that carb and even into the carb and see if it does not change anything. it all depends on what the listener calls a hiss and where it comes from. I understood that it was coming through the venturi. if so its tunable. if from somewhere else then it's a breach. vacuum leak. often my engines have a bit of a louder exhaust note yet the carbs have a noticeable hiss type sound through even multiple venturis. as vacuum leaks get eliminated the vacuum "break" at the throttle plate gets increased. louder. Link to comment Share on other sites More sharing options...
Gary Lewis Posted January 10, 2022 Share Posted January 10, 2022 it all depends on what the listener calls a hiss and where it comes from. I understood that it was coming through the venturi. if so its tunable. if from somewhere else then it's a breach. vacuum leak. often my engines have a bit of a louder exhaust note yet the carbs have a noticeable hiss type sound through even multiple venturis. as vacuum leaks get eliminated the vacuum "break" at the throttle plate gets increased. louder. Yes, you are right, Matt. We don't really "hear" the sound and are having to use someone else's ears and words to describe both the sound and the location. Which is why we are guessing. But with testing I'll bet we can get it right. Link to comment Share on other sites More sharing options...
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