Engine Vacuum?
#1462697
07/04/13 03:14 AM
07/04/13 03:14 AM
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Damned67
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Hi All, How long is a piece of string? Or, is my vacuum reading in the appropriate range? Engine is a E-headed, 10.4:1 505", 0.587/0.593 287/294 cam, M1 intake and 1050 Dominator (8896). Carb specs: 78/88 Jets Transfer slot restrictor: 0.055" PV channel restrictor: 0.089" Idle feed restrictor: 0.040" Idle air bleed: 0.082" Main air bleed: 0.028" I can't find a record of the timing, but I set it to whatever is in the archives (18 BTC at idle, 32 total in all by 2400 rpm, or something like that). It's pulling about 8" Hg on the mity vac, with a bit of flutter in the needle. Does that seem about right to you with that cam and set up?
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Re: Engine Vacuum?
[Re: Damned67]
#1462703
07/04/13 11:11 PM
07/04/13 11:11 PM
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Joined: Mar 2008
Posts: 5,746 Ontario, Canada
Dodgem
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How big a motor and did you degree the cam??
I would think it would like 28 at idle and 38 all in?
and how low you trying to idle it?
Last edited by Dodgem; 07/04/13 11:12 PM.
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Re: Engine Vacuum?
[Re: Dodgem]
#1462704
07/04/13 11:42 PM
07/04/13 11:42 PM
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Damned67
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505" engine. I can't comment on the cam being degreed, the engine was assembled by a local (and well respected) Mopar/race engine builder. Idle is around 8-900rpm. Thanks!
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Re: Engine Vacuum?
[Re: Damned67]
#1462706
07/05/13 01:08 AM
07/05/13 01:08 AM
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MR_P_BODY
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Quote:
According to the cam card, the lobe separation is 112. Lobe centerline is 108/116. Duration at 50 is listed as 259/266.
I would have thought that I should be pulling 12-15" Hg with that cam. I just don't want to spend time chasing problems that may not exist....
Are you sure you have all the vac ports plugged.. that vac is low... it should be in the 14-15 range unless the valves arent sealing(or bouncing alot)
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Re: Engine Vacuum?
[Re: sshemi]
#1462710
07/07/13 04:14 AM
07/07/13 04:14 AM
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Posts: 2,309 Tomorrow.
Damned67
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Quote:
Up timing to 22* and idle speed to 1000 and youll see 12" vac.
Sadly not... That was yesterday's job, including checking the valve lash. Still the same crappy 7-8"Hg, with the needle bouncing around a bit.
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Re: Engine Vacuum?
[Re: Damned67]
#1462712
07/07/13 11:52 AM
07/07/13 11:52 AM
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Joined: Mar 2008
Posts: 5,746 Ontario, Canada
Dodgem
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I still think you need more timing at idle. but first I would check the power valve. Then you can do this without driving start turning the advance up even as high as 32 or more at 1000 rpm see what it really likes for idle advance. Later turn it back till you can recurve the dizzy if need be. That's a big enough cam even in a 505 and big cams like lots of idle advance. I take it you have re set the float bowels?
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Re: Engine Vacuum?
[Re: Dodgem]
#1462713
07/07/13 09:31 PM
07/07/13 09:31 PM
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Joined: Jan 2003
Posts: 2,309 Tomorrow.
Damned67
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Hi Dodgem, I reset the float bowls last year when I rebuilt the carb (or re-gasketed the carb, as it were). I thought I should double check the levels, but just ran out of time. I'm somewhat lacking in the tuning area, mostly because I don't touch the car for a year, then forget what I learnt in the past. Indeed, took me ages to lash the valves, simply because it's been so long... and I forgot all my little tricks to getting the awkward plugs out to turn the engine. And yes, I plan on tossing a different power valve in it. Anyway, I'll get back to it on the weekend, unless I'm home from work early during the week. Also, I found this in amongst my PMs from 5 years ago when this engine was first fired up, from the gentleman that spec'd the engine out: "I would expect about 10-12 inches of vacuum on that combo. what are the idle rpm and timing set at? dominators don't have any vacuum ports so hopefully you drilled in a good spot. that combo should idle around 950 rpm with timing at around 18* btdc. if those are correct i'd take a look at the valve lash. that cam is 259/266 @ .of with.587/.593 lift on a 112 lobe center. it should have plenty of vacuum if installed at 108* and the lash is correct. with the engine warm, lash should be .016 intake/.018 exhaust. aside from the vacuum issue, how does it run? throttle response should be crisp and power should be plenty to roast the tires at will. if it's not that way i'd say the tune is off considerably." If nothing else, tells me I should be looking for more vacuum than I'm getting (which we already knew).
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