LARIAT 85 Posted December 26, 2020 Share Posted December 26, 2020 Thank you Lariat85 for you input on the fast idle setting, I've currently have a fairly fast idle that just continues to climb, and find myself having to tap the throttle to calm the beast. In colder conditions, the fast idle speed should start lower and climb much slower. That's because the engine needs to be choked more to build up heat and run on the leaner mixture that was set at full operating temperature. When the engine is very cold, the choke shouldn't come off by depressing the throttle. If it is only a bit cold, depressing the throttle will sometimes drop the fast idle cam down to the second step, which reduces the idle speed. The trick is, you want the choke just tight enough and the fast idle speed just fast enough to keep the engine running and to allow you to be able to drive away immediately without losing the choke and stalling out. To achieve this balance, the tension on the choke cap should be set when the engine is cold, but the fast idle speed should be set when the engine is at full operating temperature. More over before I make that adjustment I need to figure out why she's got what seems to be either a miss, or really rough idle on a cold start up. I almost have to babysit her initially just before the fast idle kicks in and the rpms come up so it won't stall. After rpm's come up to and the fast idle speed she seems to runs smooth. On a cold engine, fast idle should start immediately. You should not have to "babysit" the engine to keep it running smooth. Before starting your cold engine, step on the gas to set the choke - but do not start the engine yet. Remove the air cleaner lid and verify that the choke plate is completely closed. In the cold month of December, it should close with an audible *snap." In other words, there should be a fair amount of tension holding the choke plate tight against the air horn. If there isn't - or it is only loosely closed - rotate the choke cap a bit richer by loosening the choke cap screws. Link to comment Share on other sites More sharing options...
26ftcobraBBF Posted December 27, 2020 Share Posted December 27, 2020 Thank you Lariat85 for you input on the fast idle setting, I've currently have a fairly fast idle that just continues to climb, and find myself having to tap the throttle to calm the beast. In colder conditions, the fast idle speed should start lower and climb much slower. That's because the engine needs to be choked more to build up heat and run on the leaner mixture that was set at full operating temperature. When the engine is very cold, the choke shouldn't come off by depressing the throttle. If it is only a bit cold, depressing the throttle will sometimes drop the fast idle cam down to the second step, which reduces the idle speed. The trick is, you want the choke just tight enough and the fast idle speed just fast enough to keep the engine running and to allow you to be able to drive away immediately without losing the choke and stalling out. To achieve this balance, the tension on the choke cap should be set when the engine is cold, but the fast idle speed should be set when the engine is at full operating temperature. More over before I make that adjustment I need to figure out why she's got what seems to be either a miss, or really rough idle on a cold start up. I almost have to babysit her initially just before the fast idle kicks in and the rpms come up so it won't stall. After rpm's come up to and the fast idle speed she seems to runs smooth.http://www.garysgaragemahal.com/uploads/6/5/8/7/65879365/thinking-26_orig.jpg On a cold engine, fast idle should start immediately. You should not have to "babysit" the engine to keep it running smooth. Before starting your cold engine, step on the gas to set the choke - but do not start the engine yet. Remove the air cleaner lid and verify that the choke plate is completely closed. In the cold month of December, it should close with an audible *snap." In other words, there should be a fair amount of tension holding the choke plate tight against the air horn. If there isn't - or it is only loosely closed - rotate the choke cap a bit richer by loosening the choke cap screws. I had a chance to swing by the Cobra Headquarters yesterday. I did as you instructed and did infact hear an audible snap. Pulled the air cleaner and took a look. The flap was closed tighter than a left hand thread bolt. However I felt the spring could use some more tension, so i made an adjustment. After making the adjustment I fired it up, it didn't run any better on initial cold startup but the fast idle was kept in check by having more choke. It still has a fairly rough idle or miss for about 30 second to a minute. It kind of seems like when the rough idle is present on initial start up the engine is chugging , low idle, sounds like it wants to die, and struggles to gain high idle RPM. The fan clutch is engaged the motor is idling rough and as the RPMs slowly but steadily pick up. It gets really loud from the fan turbulence, then all at once maybe 30 seconds or so the fan disengages the fast idle kicks off , RPMs come down, and then it's a nice smooth steady idle, it's very quiet at this point sometimes second guess myself that it's still running... I did find what appears to be a lever on the carb under the fast idle cam thst looks bent . Let me know what you think about that. Thanks in advance for reading and your consideration of my issues. Mike possibly Link to comment Share on other sites More sharing options...
26ftcobraBBF Posted December 27, 2020 Share Posted December 27, 2020 That's a good idea Gary!💡 Consider it done. I guess the "tune" in the title was meant to include the steps Cobra showed in his picture of the emissions sticker. He had asked if the engine had to be warm and what order to do these basics. Cory and I responded that if you adjust idle mixture, distributor advance and curb idle you have to go round and round because both the former will effect the later. I keep trying to address that because he has been asking (in the other thread) about what goes into a calibration code, what tag should be on his distributor, etc... But that all goes out the window when he says it is "desmogged" (quotes because I don't know to what extent) and shows it with the 0-80457-S, a generic distributor and some aftermarket air cleaner. Are the thermactor ports at the rear of the heads plugged? Are the air spider manifolds removed and the fittings in the exhaust manifolds plugged? What is he using for an alternator bracket if the A.I.R. pumps and their bracket are missing? We know the cam is retarded, and he's giving up 25 hp and 50# of torque right there in my ignorant opinion. I can't think of anything that needs an EFI timing set more than an RV. http://www.garysgaragemahal.com/uploads/6/5/8/7/65879365/thinking-26_orig.jpg Top of the Morning Jim , as mentioned I have some pictures for you to look at. To answer your question Next is there are no spider air tubes. This vehicle isn't equip with them, all ports are plugged EGR is still in place acting as a temp block off plate till I can change the intake. Lastly the A.I.R bypass valve/ tube..left in place, capped with high temp thread sealant. It's a work in progress. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 27, 2020 Author Share Posted December 27, 2020 Top of the Morning Jim , as mentioned I have some pictures for you to look at. To answer your question Next is there are no spider air tubes. This vehicle isn't equip with them, all ports are plugged EGR is still in place acting as a temp block off plate till I can change the intake. Lastly the A.I.R bypass valve/ tube..left in place, capped with high temp thread sealant. It's a work in progress. 'Mornin, Mike. I keep doing a double take, because your pictures are from an unfamiliar perspective. I see you don't have the coolant pipe bolted to the front of the passenger head, that I would expect (with A.I.R. pumps.) I'm using the L&L bracket in place of that big casting. If you look at the front of the heads you'll see a Welch plug .666" diameter (the mark of the devil! ) Most people with this engine in a truck can't ever get to the little Y shaped retainers that hold that thermactor crossover to the back of the engine. But you could easily -and inexpensively- eliminate it. NAPA sells those plugs in a bag of 5, I believe... What intake do you intend to go with? Edelbrock's 2166? Consider you'll need to modify your throttle cable bracket when you do. I can kinda see the tab in your first pic... on my phone. I'm going to suggest you set your choke a little open, on the vacuum pull-off. The engine won't chug if it can get some air. But,you can play with it from inside the RV! Reach over with a finger and touch the choke blade. You'll see how that initial choke setting has an effect before it starts to open up and set on the fast idle cam. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 27, 2020 Author Share Posted December 27, 2020 'Mornin, Mike. I keep doing a double take, because your pictures are from an unfamiliar perspective. I see you don't have the coolant pipe bolted to the front of the passenger head, that I would expect (with A.I.R. pumps.) I'm using the L&L bracket in place of that big casting. If you look at the front of the heads you'll see a Welch plug .666" diameter (the mark of the devil! ) Most people with this engine in a truck can't ever get to the little Y shaped retainers that hold that thermactor crossover to the back of the engine. But you could easily -and inexpensively- eliminate it. NAPA sells those plugs in a bag of 5, I believe... What intake do you intend to go with? Edelbrock's 2166? Consider you'll need to modify your throttle cable bracket when you do. I can kinda see the tab in your first pic... on my phone. I'm going to suggest you set your choke a little open, on the vacuum pull-off. The engine won't chug if it can get some air. But,you can play with it from inside the RV! Reach over with a finger and touch the choke blade. You'll see how that initial choke setting has an effect before it starts to open up and set on the fast idle cam. The plugs are NAPA #SEP 3812188 https://www.napaonline.com/en/search?text=3812188&referer=semantic&se=1 $1.49 each. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 27, 2020 Author Share Posted December 27, 2020 http://forum.garysgaragemahal.com/file/n83632/20201226_180739.jpg Can you post a picture of that sticker on your valve cover? Link to comment Share on other sites More sharing options...
26ftcobraBBF Posted December 27, 2020 Share Posted December 27, 2020 'Mornin, Mike. I keep doing a double take, because your pictures are from an unfamiliar perspective. I see you don't have the coolant pipe bolted to the front of the passenger head, that I would expect (with A.I.R. pumps.) I'm using the L&L bracket in place of that big casting. If you look at the front of the heads you'll see a Welch plug .666" diameter (the mark of the devil! ) Most people with this engine in a truck can't ever get to the little Y shaped retainers that hold that thermactor crossover to the back of the engine. But you could easily -and inexpensively- eliminate it. NAPA sells those plugs in a bag of 5, I believe... What intake do you intend to go with? Edelbrock's 2166? Consider you'll need to modify your throttle cable bracket when you do. I can kinda see the tab in your first pic... on my phone. I'm going to suggest you set your choke a little open, on the vacuum pull-off. The engine won't chug if it can get some air. But,you can play with it from inside the RV! Reach over with a finger and touch the choke blade. You'll see how that initial choke setting has an effect before it starts to open up and set on the fast idle cam. Jim, I think cracking the chole plate open a bit is going to fix the issue it makes perfect sense. You mentioned a welsh plug in the front of the head, which is not a concern for me right? But you reference it size because it's the same size I'll need for the therm. crossover? I open for recommends for an intake. My research suggest a duel plane. What are your thoughts? It was tough trying to get a snapshot of what appears to be bent linkage possibly. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 27, 2020 Author Share Posted December 27, 2020 Jim, I think cracking the chole plate open a bit is going to fix the issue it makes perfect sense. You mentioned a welsh plug in the front of the head, which is not a concern for me right? But you reference it size because it's the same size I'll need for the therm. crossover? I open for recommends for an intake. My research suggest a duel plane. What are your thoughts? It was tough trying to get a snapshot of what appears to be bent linkage possibly. I mentioned them and gave you a part number, because the thermactor crossover fits into the exact same holes on the back of the heads... If you want to get rid of that plumbing cap, and the pipe it's attached to, spend the $2.90 and buy two of those plugs. I would use the Edelbrock manifold that I mentioned ^^^ up there. Performers are ideal for a rig like yours. My opinion, of course. Link to comment Share on other sites More sharing options...
26ftcobraBBF Posted December 27, 2020 Share Posted December 27, 2020 Okay, the distributor instructions from Scotty's old Rein'car Nation' Automotive page are: http://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_index.html And http://www.reincarnation-automotive.com/Duraspark_distributor_recurve_instructions_page-2.html Here Scotty explains the relation between slot width and degrees of advance. How to limit it by bushing the stop pin or welding the slot. How different springs affect how progressive and aggressive the centrifugal advance will be. How to adjust the vacuum 'can' and why it pulls the whole backing plate around. JIm I had a chance to dive into this yesterday. I did some research. What I have is O'Riley's Spectra premium Distributor. They didn't have a spec sheet to tell me exactly what was inside so I had him pull the part number for the "74 Elite with the 460 4 valve" as recommended in the link you sent me. Come to find out the part number were the same. So I'm not sure if if what I have is optimal, but it's close I suppose. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted December 27, 2020 Author Share Posted December 27, 2020 JIm I had a chance to dive into this yesterday. I did some research. What I have is O'Riley's Spectra premium Distributor. They didn't have a spec sheet to tell me exactly what was inside so I had him pull the part number for the "74 Elite with the 460 4 valve" as recommended in the link you sent me. Come to find out the part number were the same. So I'm not sure if if what I have is optimal, but it's close I suppose. It's hard to say what slot is used, what springs are in it, or how much preload is on the vacuum advance. I've never taken a deep dive into Spectra's specs, because I've always tuned it myself. I would hope it's good for your motor home, but as I said keep an ear out for the rattle of detonation under 'cruise' Link to comment Share on other sites More sharing options...
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