tuning help please - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 05-14-2010, 05:15 PM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
tuning help please

ok heres the lowdown
i have a sbc 350 with a weiand 177 supercharger on it
it was running really well about 3 weeks ago i dont drive it everyday
but it started to feel like it had a little miss in it so i changed out the plugs and tried a different brand plug and gapped it down a little from .035 to .030
the little miss is still there i know it sounds stupid but i changed the plugs again to another brand gapped at .035 again just to see if it was the gapped that make me keep fouling plugs
ok the car has a A/F gauge with an oxygen sensor on bank 2 so i kinda use it to tell me where to set my idle mixture screws but i tried leaning idle out a little to fix the problem but it still smells rich
here is where i am really confused i used the proper method of setting idle mixture screw... with a vacuum gauge but when i do this the best vacuum reading seems to be on the lean side and when i punch it with the carb set this way i get a backfire so i put a little more timing in it my initial is 17 but i have to keep my total under 34 p.s. i do not have vacuum adv ... same thing happened i could make it rich again but that would lower my vac readings foul my plugs and make the car smell really bad
i already smell like gas if i take the thing out for any amount of time please help

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 05-14-2010, 05:16 PM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
i forgot to mention that the main reason i started messing with it is because it seem to lack the power it had a few weeks ago
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 05-14-2010, 05:22 PM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 48
Posts: 9,890
Wiki Edits: 0

Thanks: 54
Thanked 628 Times in 558 Posts
Did you try leaning out the idle mixture screws combined with larger pump shooters to cover the leaner mixture with a bigger shot of fuel?? This will provide a leaner idle and prevent the backfire from happening, the backfire is a lean hole in the fuel curve. You need to prevent it with the correct shooter, not by overrichening the idle.

If a miss just shows up and the related parts of the spark system are ok(plugs, wires, cap/rotor), I might be taking a look at the valvetrain for problems
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 05-14-2010, 05:33 PM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
i have had the valve covers off everything is tight and the valve are adjusted so i

i also checked combustion temps with an infared thermometer it seems like cyl 4 is a little cold so if it not the plugs maybe i'll pick up an extra wire and try that
i will do what you said though... leaning out the idle and putting bigger squirters in it i have .035 now should i jump to a .037 or a .039 what do you suggest i think i may put a smaller jet in the rear bowl because i have to nearly close the idle screw all the way to get a good vac reading
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 05-14-2010, 11:06 PM
8-71 blown 461 Rat on E85
 
Last photo:
Join Date: Jan 2008
Location: Detroit michigan
Posts: 59
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
You have a heated wide band?Can you post up some a/f ratios?
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 05-15-2010, 12:19 AM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
its not heated it came in a kit its made by AEM its called a UEGO II A/F gauge kit

idle bounces between 15.7- 12.5
WOT about 13.5
cruise 12-14
it is never steady its alway bouncing around
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 05-15-2010, 12:35 AM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
if i went any bigger in the squirters i would have to convert the diaphram to a 50cc. right?
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 05-15-2010, 01:40 AM
bentwings's Avatar
bentwings
 
Last photo:
Join Date: May 2002
Location: St.Paul, Minn
Age: 72
Posts: 1,798
Wiki Edits: 0

Thanks: 0
Thanked 16 Times in 15 Posts
When you tune with an AFR gage you must have a leak free exhaust in front of the AFR or you will get erratic and generally very lean readings.

I'd check your exhaust system. I use solid copper gaskets both at the heads and collectors. Make sure the gasket surfaces are flat and clean. Use a good file and a flat plate to check flatness.

You may be knocking on the door of a flat cam. When you adjust valves be sure you check any that require a major adjustment.

Also a blown head gasket can cause a miss especially at idle.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 05-15-2010, 01:34 PM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
i dont think its a flat cam because i do have steady vacuum at all operating ranges and it does have a blower cam .488 lift with a 292 advert duration
that funny you said that about locking out the dist i have put up two post already trying to figure out how to do it but i just cant see how i would do it with my dist i got one off of ebay it is a pro comp mechanical adv dist i would like to put more timing in it intially but i know i have to keep the total down and i would like to change the advance stop so that i can limit the advancing mechanism and run a little more intial but again i just do wanna weld it just in case i dont like it and i cant see any place to zip tie it and lock the post
all in all i do believe it is just a hole in the fuel curve and needs proper tuning as someone said above
then again thats why i ask the question cuz u guys know best!!
anyway i have checked to see if any valves need dramatic adjusting and it was ok
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 05-15-2010, 01:39 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
Quote:
Originally Posted by Pupsvette76
i dont think its a flat cam because i do have steady vacuum at all operating ranges and it does have a blower cam .488 lift with a 292 advert duration
that funny you said that about locking out the dist i have put up two post already trying to figure out how to do it but i just cant see how i would do it with my dist i got one off of ebay it is a pro comp mechanical adv dist i would like to put more timing in it intially but i know i have to keep the total down and i would like to change the advance stop so that i can limit the advancing mechanism and run a little more intial but again i just do wanna weld it just in case i dont like it and i cant see any place to zip tie it and lock the post
all in all i do believe it is just a hole in the fuel curve and needs proper tuning as someone said above
then again thats why i ask the question cuz u guys know best!!
anyway i have checked to see if any valves need dramatic adjusting and it was ok
Got a photo of the dist. w/the cap and rotor off?
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 05-15-2010, 07:36 PM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
great point.
my dist is a mimic of an MSD
i have had problems with two on three of these pro comp dist the one on this car is the only one i have not had to return
i am going down to the garage to take the cap off now and look at it
yes that is my cam the one you posted up... the summit cam
locking out my dist will not effect power output.. right? it maybe hard to start with hot engine temps though or is that a myth
thanks for the advice
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 05-15-2010, 09:10 PM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
are there any negatives to locking out the advance mechanism
it sounds like its my only choice but i just wanna know what im in for otherwise
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 05-15-2010, 10:18 PM
8-71 blown 461 Rat on E85
 
Last photo:
Join Date: Jan 2008
Location: Detroit michigan
Posts: 59
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by Pupsvette76
are there any negatives to locking out the advance mechanism
it sounds like its my only choice but i just wanna know what im in for otherwise
I could rattle on for hours regarding locked out vs a spark curve with a roots blown engine.
The best I can say..if she,s a track only deal..lock her out.If you see a lot of street miles..run a spark curve.
With a non vac type distributor,you need to invest in a cd box that pulls out timing under boost with a 2 bar map sensor.
This will allow you to run the initial you require...more total at cruise/non load conditions and then pull x amount of total out based on manifold pressure.(boost).
My current setup with a 18* stop bushing..has the initial at 22* and pushing 40* at 2800 rpm with light springs.
I have my in car boost retard knob set to pull out a degree for every lb of boost.
So,here I have decent initial..plenty of advance for cruising(mpg),and no more than 32* total with 8 lbs of boost.
You can have your cake and eat it also..you just have to take advantage of modern day electronics and sensors.
I run aluminum heads and keep my coolant temp under 190*f with a 13.5/1 cruise a/f ratio and 11.8/1 wot a/f ratio.
No detonation issues on bp 93 on the street with my 11 under 8-71 blown 461 cid bbc in a 68 camaro and pulls down an honest 700+ hp and 13 mpg to boot with dual 850 double pumps.

Last edited by fatblock; 05-15-2010 at 10:37 PM.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 05-16-2010, 12:27 AM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
this is a street car and i really dont have the money for the boost retard box($329) im not so concerned with gas mileage seeing as how its a toy not a daily driver i want it to run properly and i want to tune it the best i can i am 20 years old and i go to school for automotive engineering im a motorhead this is what i will be doing with my life so i wanna learn everything i can
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 05-17-2010, 12:48 AM
Pupsvette76's Avatar
Registered User
 

Last journal entry: no spark and fuel pump issue
Join Date: May 2009
Location: smithtown
Posts: 467
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
yeah i have heard about people doing that some how i guess adding timing by using a non timed port for the signal to the vacuum can but im not sure why or how to do it is that what you are talking about
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
acceleration flat spot in carb. corvettetonybone Engine 17 04-13-2013 09:31 PM
Tuning 2 Demon Carbs on a Hemi steve392 Engine 0 03-26-2007 02:17 PM
Demon Tuning by cuda66273.... mstngjoe Engine 4 03-13-2006 07:46 AM
Tuning EFI and large cams TurboS10 Engine 0 03-12-2004 10:07 PM
what first? advance curve or carb tuning? dirtydave Engine 3 11-07-2003 05:42 PM


All times are GMT -6. The time now is 05:02 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.