absolutemoon
New member
Good god, this looks way off. What's a good starting point at around 700 rpm at idle? -9,-10?
Computer bypass 2100 changeout
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absolutemoon
New member
Ok guys, found another issue. I went to check timing again and when I removed dist. vacuum, there was no suction. That reminded me that I have a crack in my exhaust manifold. Is this the possible reason I could be off in timing?
superj
Well-known member
no, when you change carbs, you have to reset timing. the good starting point is 800-850 rpm (for an auto) at 8 degrees. you probably have your distributor on ported vacuum. hold the hose by your tongue and move the throttle slowly and you should feel the vacuum pick up. if it does you are for sure on ported vacuum. if it doesn;t, then you do have a problem.
there is conflicting stories on ported versus manifold vacuum for the distributor to run off. some of hte really serious been into engines and jeeps their whole lives guys say to run your distributor off the manifold vacuum because it pulls the advance in sooner making your engine peppier and giving you better mileage. the other camp of long time builders and jeep guys say to use the ported vacuum off the carb because it brings your advance in at certain rpms and makes your acceleration smoother so you don;t have that jumpy gas pedal. i am running ported vacuum to my distributor just because my jeep is running so good but i know on other vehicles i have run manifold vacuum and they ran great too. i might swap the vacuum tomorrow to give it a try and if i do, i will let you know how it turns out.
there is conflicting stories on ported versus manifold vacuum for the distributor to run off. some of hte really serious been into engines and jeeps their whole lives guys say to run your distributor off the manifold vacuum because it pulls the advance in sooner making your engine peppier and giving you better mileage. the other camp of long time builders and jeep guys say to use the ported vacuum off the carb because it brings your advance in at certain rpms and makes your acceleration smoother so you don;t have that jumpy gas pedal. i am running ported vacuum to my distributor just because my jeep is running so good but i know on other vehicles i have run manifold vacuum and they ran great too. i might swap the vacuum tomorrow to give it a try and if i do, i will let you know how it turns out.
absolutemoon
New member
Ok, now when I do the distrib upgrade, will I re time back to 800-850 @ -8?
superj
Well-known member
yes. that is always your base starting point. unhook vacuum and plug line, set base time to 8 and idle to 800-850.
do you have a vacuum gauge? it was very interesting using one yesterday and today to check out my engine and set my idle mixture properly. i am going to set my time using a vacuum gauge tomorrow morning and see if it works better hen just putting the time at 8 and going from there
do you have a vacuum gauge? it was very interesting using one yesterday and today to check out my engine and set my idle mixture properly. i am going to set my time using a vacuum gauge tomorrow morning and see if it works better hen just putting the time at 8 and going from there
superj
Well-known member
well, i did it by timing light and ear originally, time to 8 and adjust till idle dropped and go back 1/8 turn and it ran pretty good, too me. my dad came over and stood by and told me it was too rich and then went back to his house. i adjusted it some more and he happened to come back and said it was still to rich. i left it because it idled and started good. so i thought.
i set the mixture screws with the vacuum gauge today and the timing with the gun again, at 8. counted the turns i had the screws set at and then set the mixture to the highest vacuum with the gauge and it turns out i was 3/4 of a turn to rich. my dad was right, it was to rich. tomorrow i will set the time to the highest vacuum i can get and then reset the mixture to the highest vacuum and it should be as close to perfect as you can get. (according to the older guys on jeep forum) they say setting with the vacuum gauge is the proper way to set everything because then you know everything is at the most efficient settings.
i am supposed to have a vacuum reading of something like 20 or 22" on the gauge when i tee into the manifold vacuum port. today, i could only get a hair under 20. yesterday, when i just plugged in and didn;t set anything, i could only get 17 or 18" so using the gauge to set the mixture improved the vacuum by almost 2" which is great because the higher your vacuum reading, the healthier your engine is.
i set the mixture screws with the vacuum gauge today and the timing with the gun again, at 8. counted the turns i had the screws set at and then set the mixture to the highest vacuum with the gauge and it turns out i was 3/4 of a turn to rich. my dad was right, it was to rich. tomorrow i will set the time to the highest vacuum i can get and then reset the mixture to the highest vacuum and it should be as close to perfect as you can get. (according to the older guys on jeep forum) they say setting with the vacuum gauge is the proper way to set everything because then you know everything is at the most efficient settings.
i am supposed to have a vacuum reading of something like 20 or 22" on the gauge when i tee into the manifold vacuum port. today, i could only get a hair under 20. yesterday, when i just plugged in and didn;t set anything, i could only get 17 or 18" so using the gauge to set the mixture improved the vacuum by almost 2" which is great because the higher your vacuum reading, the healthier your engine is.
superj
Well-known member
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here is a link one of hte guys just sent me. it is really good and has pic of what different gauge swings mean
here is a link one of hte guys just sent me. it is really good and has pic of what different gauge swings mean
superj
Well-known member
here is how i was told to set the mixture
Read the topics in the center column of the third link regarding setting the carb idle. The factory settings for the mixture screws is 2.5 turns out from a gently seated bottom. Both screws are set equally, so that’s a good starting point. If you want to tune it then the Best Lean Idle method is a good way to go. Connect a vac gauge to manvac. (If you still have all the emissions equipment, disconnect the larger manifold vac line from the vac reservoir under the battery and plug the gauge in that; this will also neutralize the Pulse Air and Solvac systems while you’re tuning which is a good idea.) With the engine at operating temp and idling, turn both mixture screws in 1/8 turn, bump the throttle a little and wait 15 seconds before doing it again; continue until you reach maximum vac reading and then back each one out 1/8 turn and you’re done.
Read the topics in the center column of the third link regarding setting the carb idle. The factory settings for the mixture screws is 2.5 turns out from a gently seated bottom. Both screws are set equally, so that’s a good starting point. If you want to tune it then the Best Lean Idle method is a good way to go. Connect a vac gauge to manvac. (If you still have all the emissions equipment, disconnect the larger manifold vac line from the vac reservoir under the battery and plug the gauge in that; this will also neutralize the Pulse Air and Solvac systems while you’re tuning which is a good idea.) With the engine at operating temp and idling, turn both mixture screws in 1/8 turn, bump the throttle a little and wait 15 seconds before doing it again; continue until you reach maximum vac reading and then back each one out 1/8 turn and you’re done.
absolutemoon
New member
superj said:
Very nice link. Where on the manifold side did you tap in?
superj
Well-known member
absolutemoon
New member
Great link. Where did you tap in on the manifold side? Also, I have 10 dashes on the motor for timing marks. (258). They are as follows, +2 , 0 , -2 , -4 , -6 and so on starting with the lowest mark. Correct? I do not have a chiltons manual. Wanted to thank you for all the info. This has been a life saver.
superj
Well-known member
i used..... hmmm, i am trying to think what hte line hooked to. dang, i have two lines that are next to each other, one is ported and goes to the distributor and one is manifold and goes to the 4x4 line. i have tees in both so i can easily hook in (not that i planned that, i have no idea why i put tees in) but i cannot remember where the manifold one comes from.
one of the links says to use the pcv hose though but you can use any manifold port, even the one that the brake booster is hooked to
one of the links says to use the pcv hose though but you can use any manifold port, even the one that the brake booster is hooked to
superj
Well-known member
absolutemoon
New member
Hey 808, 5 1/2 more days!!!!!! Getting close.
superj
Well-known member
another interesting bit of information!!
Nestled up against the firewall just to the right of the engine are two vacuum switches, in the same housing. The green one is normally closed, and opens when manifold vacuum reaches 10" of mercury (Hg). The other one is natural color, and is normally open, closing when ported vacuum reaches 4". The computer watches the states of these two vacuum-operated switches to decide how far your foot is into the carburetor. These serve the same purpose as the TPS (Throttle Position Sensor) on GM and other products.
Nestled up against the firewall just to the right of the engine are two vacuum switches, in the same housing. The green one is normally closed, and opens when manifold vacuum reaches 10" of mercury (Hg). The other one is natural color, and is normally open, closing when ported vacuum reaches 4". The computer watches the states of these two vacuum-operated switches to decide how far your foot is into the carburetor. These serve the same purpose as the TPS (Throttle Position Sensor) on GM and other products.
absolutemoon
New member
I don't have those.
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