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Old 05-02-2004, 10:22 AM
JoeGrapes JoeGrapes is offline
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Default Past timing questions?

I was just reading all the past timing questions on ported verses manifold vacuum for the distributer. I just replaced my 750 vac. sec.Holley with a 750 mach. sec. Speed Demon. WOW! that 440 really screams when I step on it now. The Demon really woke it up. Here's the thing, when I set the timing at about 18 initial and about 38 total without the vac. hooked up and idling at about 950 I get a slight stumble at light throttle. Like when I'm starting off in 1st. gear and I have to feather the gasto keep it going. I've adjusted the idle mix screws in and out but no help. I tried the ported vac line and again no help. So I went with the maifold line which increased the idle. After I backed it down to 950 or so and checked the timing after it was all in with the vac. connected it was about 54 deg. at about 2500 rpm. I get no stumble now and the motor has crisper responce with no detonation. I have a vac gauge in the car and at idle it's about 13 (with the Holley it was about 9-10) and at cruise about 20. When I step on it, even lightly, it drops of to near nothing and then goes back up as speed evens out back to a cruise. Any thoughts?
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Old 05-02-2004, 11:07 AM
jmdrace jmdrace is offline
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well joe 98% sure you need a power valve change sometimes they come with a smaller "4.5"valve if so install a "6.5" valve and go from there.also the accelerator pump cam may need to go to the second postion or the faster one.then relook at float height make sure it dribbles out of sight hole.these are all easy tweeks.then as for the timing check the index on that dampner.54degrees is a whole lota time.this is a stock distributor? if so make sure the weights or other fandango devices inside are working and have not been alterd.if msd look at the weights and springs also.i like them locked.
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Old 05-02-2004, 11:51 AM
JoeGrapes JoeGrapes is offline
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jm, the 54 degs is total advance. Initial+machanical+vacuum. I have a MP Performance distributor and the the timing is right where the directions say it should be. I followed the "Timing for maximum performance" section in the directions. My only concer is as to which vacuum to use. When I tried the ported vacuum it didn't make any difference. I think without the vacuum hooked up, I have to raise the idle so much it uncovers the idle transfer slots and causes the stumble. When I use manifold vacuum the increase in timing at idle raises the rpm and which allows me to back off on the idle screw and the throttle blades will then cover the transfer slots. The Demon carb is right out of the box and even though I did check everything they said before I put it on, I will take another look at your suggestions. Also the 440 is not stock but mildy modified with the usual stuff. The cam is a Comp. 230/236@.05 duration Extreme Energy 274H. Thanks for the help.
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Old 05-02-2004, 12:51 PM
jmdrace jmdrace is offline
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joe when you begin to uncover the transfer slots you begin the the transfer form idle to a mid circuit or pullin from the jets.this will not give you a stumble as you are in the main circuit its hammer down.now a stumble is when the car does a nose dive like a big hole then wammo yo take off.a blurble is when she gets to much fuel and sorta stumbles blurbles and then takes off after it cleares itself.also what manifold do you have ??o and also under the carb on the secondary there may also be a small ajusting screw look close.
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Old 05-02-2004, 01:09 PM
JoeGrapes JoeGrapes is offline
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Ha jm, I guess I have a blurble. That sounds more like my problem,lol The manifold is a Edelbrock RPM Performer. I know the screw your taking about. The weather is not good here so I'm going to take the carb off and check to make sure the transfer slots are not to exposed to much. The Demon book said they should be only exposed about .02 or the slots should look square. We'll see. But you might me right, I might be too rich at idle.
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Old 05-02-2004, 01:12 PM
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MoparMarcIdaho MoparMarcIdaho is offline
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Arrow just seen pics of demon

but they are similar to holleys in some ways,mabeye you need to step up the pump shot cam or replace with more agressive lobe?Also might just need to lengthen adjustment?
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Old 05-02-2004, 01:20 PM
JoeGrapes JoeGrapes is offline
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jm, before I take the carb off to check the slots I thought I'd check a spark plug to see how it's burning. The plug is BLACK! Way to rich at idle. Ok, I need to solve this. Back to the book.
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Old 05-03-2004, 06:23 PM
jmdrace jmdrace is offline
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ok joe so shes fat,and we are sure our timing is correct as for index to dampner to #1cylinder ok .as for pulling vacume rite outa the manifoldas close to center as possiable.clean the plugs up with a clean rag with litle scrubbin and 2+2 gumcutter and reistall.next is fire power id the coil part of the install ?or do you need to reinstall old dist. and coil? back to the carb if it does have the 4.5 power valves leave them as you are only pullin 13 inchesa vacume.ok lets now look at jet size should be some place in the 50's no more than 65..now lets look at the air bleeds on top of carb the outside ones are idle they shuld be a good size bigger than the inside ones or do you have adjustable type.now the next one is fuel pressure wants be 4-5 lb for street 7 racin 9 for alky.and this timing thing this what they want???? well one remote possiablity also is a vacume leak or internal leak in carb.workin on this is a round and round double checkin all we did. this eaven means reinstallin the old carb.so try those eyeball easy checks first. somthin simple .
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