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Old 10-16-2010, 10:25 PM
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idle problem and vac. question

ok well i have a sbc 383 9.7 cmp. vortec heads 224/224 465/465 lift cam holley 750 vac. sec. with a th350 trans stock stall converter 2.41 gears the question is whats a good idle for a sbc383 like this? is 1000 rpm ok and 700 in drive and i did a vac test and at idle (1000rpm)it gave me 18-19 and in drive it gave me 14(700 rpm) is that good

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Old 10-16-2010, 11:06 PM
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vacumn

Very nice vacumn for your build, sounds like it is set up pretty well and healthy.
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Old 10-16-2010, 11:35 PM
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so its ok dude i am glad to hear that thanks
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Old 10-17-2010, 06:23 AM
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Quote:
Originally Posted by sickolds
ok well i have a sbc 383 9.7 cmp. vortec heads 224/224 465/465 lift cam holley 750 vac. sec. with a th350 trans stock stall converter 2.41 gears the question is whats a good idle for a sbc383 like this? is 1000 rpm ok and 700 in drive and i did a vac test and at idle (1000rpm)it gave me 18-19 and in drive it gave me 14(700 rpm) is that good
Dude! What's that engine in? I'll bet it will do 70 mph in first gear no problem.
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Old 10-17-2010, 06:57 AM
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Quote:
Originally Posted by sqzbox
Dude! What's that engine in? I'll bet it will do 70 mph in first gear no problem.
5500rpm w/26" tire = 1st = 70mph, 2nd = 116mph, 3rd = 176mph in a perfect world
Reminds me of the Movie "Dirty Mary & Crazy Larry" where the Cop says "My topend is unlimited".
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Old 10-17-2010, 07:53 AM
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olds not trying to rain on your parade but based on your thread title using the word "problem",,,

not sure what your intent was when putting this ride together, if it was a top end speed missle then you have succeeded, its all good , however the cam is by convention too big for a stock stall and those gears, and the drop in idle rpm is most likely due to the low stall convertor causing the engine to load up some at idle thats why you see the drop in idle and vacuum as such.

i have a similar 383 with a slightly smaller cam and stock 1800 stall, same issue with the idle speed drop as mine loads up at a stop light, i am on the brakes hard to keep it still, it is really noticable with mine cause i don't have power brakes, and yeah my base idle needs to be about 950 out of gear to get a decent in gear idle speed, a higher BTDC base timing setting and full vacuum adv at idle helped me out some.
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Old 10-17-2010, 03:18 PM
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yea its all good on the freeway but on the street its a lil slow on the take off right now its my daily driver so i cant go and throw 373 gears on it but i have been thinking about a stall converter some thing small and cheap summit have some for under $120 wen i put the car in drive it does load up to the pint that it shakes the car so i am going to drop the idle to 900 prm we will see what happens i appreciate the info thanks
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Old 10-18-2010, 04:35 AM
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With the gears you have now you need to be careful on what stall speed you select as there will be slippage in third gear under highway speeds creating more heat ( fluid temp, tranny temp, and even slight coolant temp). Then you'll be looking for an external tranny fluid cooler.
You can lower the idle speed some, but if you go too low, your vacuum will drop and when you put it in gear the engine will die. In trying to fix one problem, you can create more problems if you don't think ahead.
As always, there is a trade off between street driving and performance driving with a modded engine especially with your geological location (winter temp's and summer temp's, humidity and elevation).
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Old 10-18-2010, 06:02 AM
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I`m curious do you want it to idle that high? It`s supposed to idle around 750 in gear. Cam companies recommend it to idle this low, likely due to help some of the idle creep in gear. If yours doesn`t do so it`s likely due from the high rear gears. If you stepped up to 3.42 gears and dropped it to 750 idle, it would creep awful in gear with a stock converter. It should say on your cam card what the recommended idle speed is. The high vacuum reading is likely from the high idle speed. What`s the timing set at? Is the vac advance connected to a ported or a manifold source? Shine a light in the carb at idle, see if you see any fuel coming from the boosters, if so the idle is set so high it`s past the idle circuits and into the main circuits, this would be a sign the spark timing is too low.
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Old 10-18-2010, 10:50 AM
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For some reason it won`t let me edit my previous post. Anyway, I meant shoot for a idle speed around 875 in park. It should drop to around 600 to 650 in drive. If not, set the idle in park to where in lands in the 600 - 650 range in drive.
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Old 10-18-2010, 02:01 PM
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Quote:
Originally Posted by DoubleVision
For some reason it won`t let me edit my previous post.
DV, You have forgotten that you only have 30 min. to edit your post. After that, It's "chiseled in stone".
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Old 10-18-2010, 03:22 PM
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They musta changed this not long ago as used to it could be a few hours later and I could edit it or so I remember. But my remembering isn`t so great anymore, I`m gettin` old.
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Old 10-18-2010, 04:11 PM
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my remembering isn`t so great anymore, I`m gettin` old.
LMAO! You ain't seen nothing yet.
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