flat spot in throttle - 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 04-22-2008, 11:19 PM
elcaminodragster's Avatar
70 El Camino aka FRANKENSTEIN
 
Last photo:
Join Date: Feb 2007
Location: California
Age: 26
Posts: 738
Wiki Edits: 0

Thanks: 2
Thanked 0 Times in 0 Posts
flat spot in throttle

first off the specs.

350sbc 10.25 CR
268h cam
rpm air gap intake
650 avs carb
hooker comp headers

well ive been messing with this problem for to long and i could use some help. when driven around normally i dont have a flat spot only when i punch it hard to WOT. if i slowly increase the throttle to WOT then no flat spot. only happens when i punch it. ive messed with timing, step up springs, plunger settings, and the secondary valve control. im most positive i need a calibration kit. but i have also read that a spacer could help out by adding more volume to the intake. i read in a few posts that the reason for some flat spots is that the air and fuel dont have enough time to mix properly. and in other cases make the flat spot worse. but you only know by trying it out. and they are cheep enough to try out. i realize by adding a spacer it kills low end. but it cant kill that much to worry about if it makes the car run better. i have a 2500 stall speed so that helps me get up in the rpms to get out of the low end. so would it be worth buying a spacer and then calibrating the carb??? or just calibrate it as is???

i realize this is a loaded question ive read a lot about spacers some say the work others say they hurt but thats for there setup not mine. but still a loaded question i know.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-23-2008, 01:04 AM
carsavvycook's Avatar
My 2 cents worth
 
Last photo:
Join Date: Sep 2007
Location: Lakeside, CA
Age: 57
Posts: 2,855
Wiki Edits: 3

Thanks: 2
Thanked 2 Times in 2 Posts
A calibration kit may do you no good. It would help to know which carb # you have and what jets and metering rods you have in it. You might just have to get larger squiters. AVS?
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-23-2008, 07:47 PM
elcaminodragster's Avatar
70 El Camino aka FRANKENSTEIN
 
Last photo:
Join Date: Feb 2007
Location: California
Age: 26
Posts: 738
Wiki Edits: 0

Thanks: 2
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by carsavvycook
A calibration kit may do you no good. It would help to know which carb # you have and what jets and metering rods you have in it. You might just have to get larger squiters. AVS?
edelbrock AVS (adjustable valve secondaries) thunder series 1805 Manuel choke. main jet 0.095 metering rod 0.068 x 0.047. im most positive i need more fuel because when i adjusted the plunger to squirt more fuel it got rid of some of the flat spot.

http://static.summitracing.com/globa...805_charts.pdf

what about setting the carb to #5 in the or #8 in the chart???
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 04-23-2008, 08:03 PM
carsavvycook's Avatar
My 2 cents worth
 
Last photo:
Join Date: Sep 2007
Location: Lakeside, CA
Age: 57
Posts: 2,855
Wiki Edits: 3

Thanks: 2
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by elcaminodragster
edelbrock AVS (adjustable valve secondaries) thunder series 1805 Manuel choke. main jet 0.095 metering rod 0.068 x 0.047. im most positive i need more fuel because when i adjusted the plunger to squirt more fuel it got rid of some of the flat spot.

http://static.summitracing.com/globa...805_charts.pdf

what about setting the carb to #5 in the or #8 in the chart???
I would go with #11 just changing the jets to .098 with the .068-.047 rods to richen the carb up. You can also do this; close the choke a 1/4 of the way to see if the flat spot is gone before replacing the jets. This will richen it up close to the same as the jet change.

Last edited by carsavvycook; 04-23-2008 at 08:13 PM. Reason: wrong wording
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 04-23-2008, 08:51 PM
elcaminodragster's Avatar
70 El Camino aka FRANKENSTEIN
 
Last photo:
Join Date: Feb 2007
Location: California
Age: 26
Posts: 738
Wiki Edits: 0

Thanks: 2
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by carsavvycook
close the choke a 1/4 of the way to see if the flat spot is gone before replacing the jets. This will richen it up close to the same as the jet change.

my dad had me try something like that awhile ago. he covered the carb with his hands to block off the air i believe it helped a bit. cant remember but ill try that again.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 04-23-2008, 08:59 PM
carsavvycook's Avatar
My 2 cents worth
 
Last photo:
Join Date: Sep 2007
Location: Lakeside, CA
Age: 57
Posts: 2,855
Wiki Edits: 3

Thanks: 2
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by elcaminodragster
my dad had me try something like that awhile ago. he covered the carb with his hands to block off the air i believe it helped a bit. cant remember but ill try that again.
What did he grab onto to brace himself during the test drive?
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 04-24-2008, 09:05 PM
elcaminodragster's Avatar
70 El Camino aka FRANKENSTEIN
 
Last photo:
Join Date: Feb 2007
Location: California
Age: 26
Posts: 738
Wiki Edits: 0

Thanks: 2
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by carsavvycook
What did he grab onto to brace himself during the test drive?

haha well i tied a a rope to his waist and said hold on tight . while in the driveway in park it has a slight bog at the same spot in the throttle when im driven. only while driven the engine near dies.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 04-24-2008, 09:14 PM
carsavvycook's Avatar
My 2 cents worth
 
Last photo:
Join Date: Sep 2007
Location: Lakeside, CA
Age: 57
Posts: 2,855
Wiki Edits: 3

Thanks: 2
Thanked 2 Times in 2 Posts
Just wanted to know if he had to hang on tight during the engine bog.

Try the 8" silver step-up springs along with my recommendations from my post from yesterday.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 04-24-2008, 09:15 PM
elcaminodragster's Avatar
70 El Camino aka FRANKENSTEIN
 
Last photo:
Join Date: Feb 2007
Location: California
Age: 26
Posts: 738
Wiki Edits: 0

Thanks: 2
Thanked 0 Times in 0 Posts
i think im gonna try a spacer. . . because ive read some more about them and it might might be that the air and fuel dont have enough time to fully mix when i punch it. because on the initial punch to WOT from idle or cruise speed it chokes but if i slowly bring the throttle open then it works just fine no choke or hesitation. so i figure a 20 dollar spacer cant hurt itll either help or hurt but either way itll teach me something new
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 04-24-2008, 09:27 PM
carsavvycook's Avatar
My 2 cents worth
 
Last photo:
Join Date: Sep 2007
Location: Lakeside, CA
Age: 57
Posts: 2,855
Wiki Edits: 3

Thanks: 2
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by elcaminodragster
i think im gonna try a spacer. . . because ive read some more about them and it might might be that the air and fuel dont have enough time to fully mix when i punch it. because on the initial punch to WOT from idle or cruise speed it chokes but if i slowly bring the throttle open then it works just fine no choke or hesitation. so i figure a 20 dollar spacer cant hurt itll either help or hurt but either way itll teach me something new

Makes sense to me. Who ever said "You can't teach an old dog new tricks" is wrong
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 04-24-2008, 09:37 PM
elcaminodragster's Avatar
70 El Camino aka FRANKENSTEIN
 
Last photo:
Join Date: Feb 2007
Location: California
Age: 26
Posts: 738
Wiki Edits: 0

Thanks: 2
Thanked 0 Times in 0 Posts
sorry i forgot to mention i currently have the 8hg springs in there. i dont notice any real difference. i mean there is a difference but so subtle its almost not there. it seems everything ive tried only gets rid of a tiny little bit. before i did anything to it the flat spot was really bad the engine would die and id have to put it in neutral and start the engine. now the engine nearly dies.

well i get paid tomorrow so ill buy a spacer tomorrow say 1"??? since i have a divided plenum ill have to buy the 4 hole or should i buy the open spacer??? im thinking the 4 hole so i keep the intake divided.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 04-24-2008, 09:57 PM
carsavvycook's Avatar
My 2 cents worth
 
Last photo:
Join Date: Sep 2007
Location: Lakeside, CA
Age: 57
Posts: 2,855
Wiki Edits: 3

Thanks: 2
Thanked 2 Times in 2 Posts
I have only installed 1 spacer in the last 36 years, and it was on my own car when going to a Holley 4BL on my Spread bore 351CID 4BL intake(factory Ford), and that was in 1978. It never ran right and acted like it was running out of fuel, so I parked it and put it in "mothballs" in 1985.

That's my project coming out soon!
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 04-24-2008, 10:05 PM
speedydude's Avatar
Registered Cruiser
 
Last photo:
Join Date: Apr 2007
Location: Sedona, AZ
Posts: 271
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Elky, there's a thread titled "carb spacers" that's recent. In there 1Bad80 posted a link to the wiki that's worth reading. I've been running a smaller carb spacer that's been working really well. (1" aluminum). Lot's of opinions on this subject however I like what techinspector1 had to say in the above-mentioned thread.

Alot depends on the setup. Stock, mildly modified, dual-plane, single-plane, RPM range??? rear gears??

Anyway, happy reading...............I seem to do alot of it..............
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 05-07-2008, 04:10 PM
elcaminodragster's Avatar
70 El Camino aka FRANKENSTEIN
 
Last photo:
Join Date: Feb 2007
Location: California
Age: 26
Posts: 738
Wiki Edits: 0

Thanks: 2
Thanked 0 Times in 0 Posts
well i dont need a carb spacer i tossed a set of 0.65 x 0.37 rods in compared to the stock 0.68 x 0.47 rods. that helped out quite a bit but i still have a stumble. b4 the rods it nearly died now with the rods it kinda stumbles "rump RUmp RUMP VROOM!!!" lol thats the best way i can put it. this is making me think instead of dumping more fuel just buy a bigger carb. but i can just keep trying more fuel.

so far the upgrades i have done.

1) 8hg step up springs from the stock 5hg (not much change if any)
2) crane cams adjustable vac advance (timing is dead on cant get better)
3) adjusted the plunger from the middle hole to the top hole (bigger squirt of fuel)
4) rods 0.65 x 0.37 from the stock 0.68 x 0.47

with each change or upgrade its gotten a bit better and all together its gotten much better. from stock everything no changes the engine would die. now it has a "rump RUmp RUMP VROOM!!!"

so i do not need a spacer i need more fuel. can i get bigger (idk how to properly say it because i havent found the part) jets for the plunger squirter. sorry if that doesnt make sense.

or should i think about a bigger carb??? 750cfm???
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 05-07-2008, 04:32 PM
carsavvycook's Avatar
My 2 cents worth
 
Last photo:
Join Date: Sep 2007
Location: Lakeside, CA
Age: 57
Posts: 2,855
Wiki Edits: 3

Thanks: 2
Thanked 2 Times in 2 Posts
Going to a 750 cfm is better than richening yours up any more. You still might have to tune it a little though.

Let us know how it goes.
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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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
Flat spot fred56 Engine 4 07-20-2007 04:50 PM
I'm going to make a bonfire out of my car blown69stang Engine 36 08-22-2005 03:36 PM
Comp Cams hydraulic roller vs. solid flat tappet comparison Mad Maggot Engine 23 02-13-2005 10:29 AM
Throttle body spacers Mertz Engine 2 09-22-2003 09:16 AM


All times are GMT -6. The time now is 04:05 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.