why do blower engines surge at idle?
03-01-2016, 02:21 PM
#42
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they are/were.. Makes no difference on idle .. Onlychanges the way the fuel curve works when you roll into boost..There is no boost at idle..
03-01-2016, 02:42 PM
#43
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iTrader: (3)
The only way the power valve will cause an idle issue, is if the diaphragm is ruptured, and the engine vacuum is pulling raw fuel thru it.
03-01-2016, 02:46 PM
#44
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I have the reverse problem,, stock 454mag with stock cam and a B&M420 blower,,idle surges like crazy,
stock cam pulls too much vacuum and when blower surges vacuum drops,,it will swing from 18" of vacuum to 8" of vacuum,,had carbs gone thru twice by Dan DaVinci with no imprvement,,he has tried every trick in the book,,idle will not settle down unless you lean it way out and then you cant put it in gear without it dying..
I had this same setup on my last engine, 509 with custom cam and idled perfectly at 10-12" vaccum.
vid:
https://www.facebook.com/Frank.No.Pr...type=3&theater
stock cam pulls too much vacuum and when blower surges vacuum drops,,it will swing from 18" of vacuum to 8" of vacuum,,had carbs gone thru twice by Dan DaVinci with no imprvement,,he has tried every trick in the book,,idle will not settle down unless you lean it way out and then you cant put it in gear without it dying..
I had this same setup on my last engine, 509 with custom cam and idled perfectly at 10-12" vaccum.
vid:
https://www.facebook.com/Frank.No.Pr...type=3&theater
03-01-2016, 05:03 PM
#45
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iTrader: (1)
Also going to a milder cam, smaller cid, and etc his carbs need either idle air bleed and/or idle feed restriction change.
I have the reverse problem,, stock 454mag with stock cam and a B&M420 blower,,idle surges like crazy,
stock cam pulls too much vacuum and when blower surges vacuum drops,,it will swing from 18" of vacuum to 8" of vacuum,,had carbs gone thru twice by Dan DaVinci with no imprvement,,he has tried every trick in the book,,idle will not settle down unless you lean it way out and then you cant put it in gear without it dying..
I had this same setup on my last engine, 509 with custom cam and idled perfectly at 10-12" vaccum.
vid:
https://www.facebook.com/Frank.No.Pr...type=3&theater
stock cam pulls too much vacuum and when blower surges vacuum drops,,it will swing from 18" of vacuum to 8" of vacuum,,had carbs gone thru twice by Dan DaVinci with no imprvement,,he has tried every trick in the book,,idle will not settle down unless you lean it way out and then you cant put it in gear without it dying..
I had this same setup on my last engine, 509 with custom cam and idled perfectly at 10-12" vaccum.
vid:
https://www.facebook.com/Frank.No.Pr...type=3&theater
Last edited by SB; 03-01-2016 at 05:07 PM.
03-01-2016, 06:11 PM
#46
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Join Date: Feb 2016
Location: MICHIGAN
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I like a little surge . With my single its easy to shift it into gear and time it coming down . All this talk is starting to get me motivated for spring. To bad we are getting pounded with another snowstorm right now.
03-01-2016, 07:39 PM
#47
Registered
I have a 177 on my 454 that I just built. It has a dominator carb on it. I am hoping it surges. Probably wont but I can dream.
03-02-2016, 08:00 AM
#49
Geronimo36
Gold Member
Been running blowers for a long time and I've never had any surge. When I hear a big cube blower motor with carbs that has little to no surge, I smile because the person took the time to tune it.
03-02-2016, 08:19 AM
#50
Platinum Member
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iTrader: (2)
I know mine needs to be be tuned in the boat... didn't surge on the dyno. Once the blower comes back from the shop, I'll be able to work on it some. I don't really want it to surge.... makes things a pain.
