Vacuum leak through carburetor secondaries?
I'm trying to find a vacuum leak on my Carter AFB 9636S but I'm failed everything that I've tried using carburetor cleaner. I'm pretty sure that I'm dealing with a vacuum leak because the car has rough idle, hesitates on acceleration and if i put my hand over the air horn the engine revs.
So I think: Is possible to have a vacuum leak through the secondaries? |
some times the base gets warped. if you have to get the base machined be sure and tie the plates closed. in 1968 the new AVS had a lean idle circuit that cause a bog off idle. this is fixed by drilling the idle jet. this is NOT for every one to do.. I think it is Carter AFB Competition Series Carburetor . it might be stock with a lean idle circuit. but first reset the float level to 5/16. O.E.M. is 7/32.
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That is an aftermarket Mopar specific carb.. Should work great... I would check the timing, try a little more advance. Make sure the accelerator pump is working
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Originally Posted by moe7404
(Post 125082)
some times the base gets warped. if you have to get the base machined be sure and tie the plates closed. in 1968 the new AVS had a lean idle circuit that cause a bog off idle. this is fixed by drilling the idle jet. this is NOT for every one to do.. I think it is Carter AFB Competition Series Carburetor . it might be stock with a lean idle circuit. but first reset the float level to 5/16. O.E.M. is 7/32.
If the carb base is warped, when I spray carb cleaner around it, should not affect the idle? because when I did that nothing happened That is an aftermarket Mopar specific carb.. Should work great... I would check the timing, try a little more advance. Make sure the accelerator pump is working |
your test for a leak in base is the right way to test. i guess the idle jet needs drilled. from your hand over the lid test says it is lean. get a #61-#80 drill set. on mine the brand name is covered with sticker. but the pt no is HAWTJ6180. you will all so need a pin vice to hold the drill bits. this possess is done very slowly. ONLY by hand, NOT power. take the primary clusters out. the small brass tube is the idle jet. use the drill set to find the dia of the small hole at the bottom. the small dia only goes 1/16 into the tube. to drill the hole chose the drill bit only one step bigger than the stock size. hold the cluster with the tube facing down. drill going up so the the chips fall away from the tube. then test by driving.
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I spent all the sunday afternoon trying to figure out what was happening with the carb. I cleaned everything, changed the intake gasket and sand the carburetor base just to discard a bad seal between the carburetor and gasket but the test result was the same. Here's a video that I made to try to explain what is happening:
http://vid1067.photobucket.com/album...psvxiynbab.mp4 Then I remember TVLynn post about the ignition timing so I give a bit more advance to the distributor (I don't know how much more exactly because my timing light is broken) and the change was awesome, the idle is a lot smoother, the engine vibration almost stopped but when I put my hand over the air horn the engine still revs so the lean condition continues :( This video is after the advance change http://vid1067.photobucket.com/album...psyw4hpvhy.mp4 |
On that video ? It looks like the throttle shaft has lots of play ????
had a 9636 on a 360 / 284/484 cam worked just fine out of the box... |
1 Attachment(s)
Originally Posted by TVLynn
(Post 125092)
On that video ? It looks like the throttle shaft has lots of play ????
had a 9636 on a 360 / 284/484 cam worked just fine out of the box... your test for a leak in base is the right way to test. i guess the idle jet needs drilled. from your hand over the lid test says it is lean. get a #61-#80 drill set. on mine the brand name is covered with sticker. but the pt no is HAWTJ6180. you will all so need a pin vice to hold the drill bits. this possess is done very slowly. ONLY by hand, NOT power. take the primary clusters out. the small brass tube is the idle jet. use the drill set to find the dia of the small hole at the bottom. the small dia only goes 1/16 into the tube. to drill the hole chose the drill bit only one step bigger than the stock size. hold the cluster with the tube facing down. drill going up so the the chips fall away from the tube. then test by driving. https://moparforums.com/forums/attac...1&d=1417441827 |
no the small tube pointing down. is the idle jet. the bigger tube pointing down is the emulsion tube. it mixes fuel with air to go to the high speed discharge nozzle. the small tube pointing up is an air bleed that lets air into high speed discharge air fuel mix. so the fuel will drop out of high speed discharge nozzle when the engine goes to idle.
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On the 9636 YOU should not need any adapter
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Pull More timing in it until it reads at least 18"...
Pull the Mixture screws out 3-4 turns... See if that helps... |
Originally Posted by RacerHog
(Post 125107)
Pull More timing in it until it reads at least 18"...
Pull the Mixture screws out 3-4 turns... See if that helps... On the 9636 YOU should not need any adapter no the small tube pointing down. is the idle jet. the bigger tube pointing down is the emulsion tube. it mixes fuel with air to go to the high speed discharge nozzle. the small tube pointing up is an air bleed that lets air into high speed discharge air fuel mix. so the fuel will drop out of high speed discharge nozzle when the engine goes to idle. |
Ok...So you only get Idle mixture screw response from all the way in.. And Out only 1.5 turns...
Common rule of thumb:: it takes 18" of vacuum to run for the average street engine..... Read the gauge... It can help you.... Pull the timing until it's in the GREEN AREA... :) If that don't work... You got problems elsewhere... But that's the only way I know of to get there with out a timing light... When you throttle it... To me it even sounds like the timing is late.... |
get a spacer for the air cleaner ! http://www.carburetion.com/sitesearc...ner%20Adaptors
Also get a correct throttle cable brackets The metal part of the cable should be healed by the clamp on bracket.. |
Went and dug mine out Going from memory The large fitting on the front side should go to the PVC valve
the rear large hole should be plugged the large side vent goes to the air cleaner Power brakes should hook up to intake manifold I don't believe you have a 9636 carb ??? Has a Chevy ? throttle shaft |
Originally Posted by TVLynn
(Post 125129)
get a spacer for the air cleaner ! http://www.carburetion.com/sitesearc...ner%20Adaptors
Also get a correct throttle cable brackets The metal part of the cable should be healed by the clamp on bracket.. Went and dug mine out Going from memory The large fitting on the front side should go to the PVC valve the rear large hole should be plugged the large side vent goes to the air cleaner Power brakes should hook up to intake manifold I don't believe you have a 9636 carb ??? Has a Chevy ? throttle shaft I tried one more time to clean all the carburetor before drill the idle jets, this time I used other liquid carburetor cleaner. Back on the engine the results were noticeable. Now I've more vacuum, easier start, the idle mixture screws are a little more sensitive in the first 2 turns and now if I cover the air horn with my hand the engine doesn't revs. Here's a video of the results (on this video the distributor advance was already adjusted). http://vid1067.photobucket.com/album...pspgpv9k7e.mp4 The unique problem is that the idle came rough and sometimes I see black smoke on the exhaust when the engine is idling below 800 RPM. Maybe I've a spark plug that needs to be changed? |
at idle any adjusting of 1/4 / 1/2 turn on the idle mix screws should make a change in the idle speed. other wise something is wrong. are you sure you dont have a square bore carb on a spread bore intake manafold with out the the right steel plate?
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Originally Posted by moe7404
(Post 125233)
at idle any adjusting of 1/4 / 1/2 turn on the idle mix screws should make a change in the idle speed. other wise something is wrong. are you sure you dont have a square bore carb on a spread bore intake manafold with out the the right steel plate?
This is my intake: http://m.ebay.com/itm/330869715498?nav=SEARCH And is a square bore intake :( Maybe is time for a carb replacement? |
Pull that timing around till the needle is in the green !!!!!
That little red zone said late ing. timing rite !!!!!! |
Originally Posted by RacerHog
(Post 125239)
Pull that timing around till the needle is in the green !!!!!
That little red zone said late ing. timing rite !!!!!! |
No... In this case.... Question.... Have You performed a compression test at this time? if so what are the numbers again?
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Originally Posted by RacerHog
(Post 125251)
No... In this case.... Question.... Have You performed a compression test at this time? if so what are the numbers again?
Dry: Cyl #, PSI 1: 105 2: 110 3: 100 4: 105 5: 105 6: 102 7: 95 8: 108 Wet: Cyl #, PSI 1: 125 2: 115 3: 105 4: 110 5: 105 6: 105 7: 95 8: 105 |
Sounds like you are getting close to needing a valve job.. Maybe rings ? That carb is not jetted for your mopar...
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Yep.... 125 PSI Across the board is wear it should be... In my Opinion
IS the ticking clanking... Coming from that # 7 Cylinder? |
Originally Posted by TVLynn
(Post 125257)
Sounds like you are getting close to needing a valve job.. Maybe rings ? That carb is not jetted for your mopar...
Why do you think is not jetted for the 360 (too lean or too rich?)? Right now i have 0.098 on the primary jet and 0.095 on the secondaries Yep.... 125 PSI Across the board is wear it should be... In my Opinion IS the ticking clanking... Coming from that # 7 Cylinder? I need to ask: can the vacuum reading or the compression test be affected due to the altitude? Because If I'm right 125 PSI equals to a CR of 8.5:1 at the sea level but I don't live at that altitude... The engine was rebuilt on the second semester of the last year and right now it has less than 300 miles since rebuilt. But I've always suspected that the machine shop didn't made a good work with the heads because they returned them to me very quickly. Is there a way to check if the valves, valve springs or event the valve seats are worn without removing the heads? |
Might be a bad lifter???? Could be a bent push rod? Over worn Rocker maybe? Broken Valve spring? Just a few things to check and a little work too take a peek.
IF it pulled 125PSI as a high... That's what it pulled.... the rest should be within +/- 10-20% as a rule of thumb... But to answer the question, Yes Altitude can make a difference. Well That just sucks !!!!! So we really are not sure how well the internals are.. :( Just listing to it labor to run. Makes me think the Cam to Crank alignment is not set properly. This where I was going, but now I'm unsure about the whole Rebuild stability.... |
Originally Posted by RacerHog
(Post 125264)
Might be a bad lifter???? Could be a bent push rod? Over worn Rocker maybe? Broken Valve spring? Just a few things to check and a little work too take a peek.
IF it pulled 125PSI as a high... That's what it pulled.... the rest should be within +/- 10-20% as a rule of thumb... But to answer the question, Yes Altitude can make a difference. Well That just sucks !!!!! So we really are not sure how well the internals are.. :( Just listing to it labor to run. Makes me think the Cam to Crank alignment is not set properly. This where I was going, but now I'm unsure about the whole Rebuild stability.... Which checks can I do after pull the heads out and check the internals? A video with the engine running without valve covers can be useful on this situation? Now I'm nervous because it seems that my fears are becoming reality and maybe the engine will need to be pulled out the car :( |
I did forget to mention, that yes you will have to remove the heads to check them or have them checked properly... Spring Tension, installed height, valve stems, valve margins, seat in the head, installed height, and so on. But if your going in that far you might as well look at the Rings and Bore and so on....
I just am leery of the basic foundation at this point. No scents in throwing good money into something that really need attention elsewhere... If you know what I mean. |
Originally Posted by RacerHog
(Post 125266)
I did forget to mention, that yes you will have to remove the heads to check them or have them checked properly... Spring Tension, installed height, valve stems, valve margins, seat in the head, installed height, and so on. But if your going in that far you might as well look at the Rings and Bore and so on....
I just am leery of the basic foundation at this point. No scents in throwing good money into something that really need attention elsewhere... If you know what I mean. Here's the video: http://vid1067.photobucket.com/album...psxeutart8.mp4 Also I noticed that without the PCV valve the left head smokes and the right smokes too a bit, I don't know if that's normal, but I made a video too: http://vid1067.photobucket.com/album...psn5mav1rm.mp4 Must I prepare everything to remove both heads, right? :( |
Those are self adjusting rockers and shafts..... You just torq them to spec and thats that.... Not like chevy's... No 0 lash and then give it 1 turn... Not on this type....
The BlowBy might be because the rings are not seated yet.... Lack of mileage? Just a thought.... Oiling looks good..On the top end.... Still would like to know why that #7 Cylinder has such low compression? Must be rings or Valve Leaking..... Cam lift looks ok..... |
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