vacume advance - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board -- 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
lost password?   |   register now

LinkBack Thread Tools
  #16 (permalink)  
Old 02-09-2013, 04:27 PM
Registered User

Last journal entry: gus`s 40
Last photo:
Join Date: Jul 2012
Posts: 82
Wiki Edits: 0

Thanks: 3
Thanked 6 Times in 6 Posts
thanks f-bird'88 I just read the link jaw22w sent and was very helpful, I forgot to mention it is a auto trans with a 3000 stall, the engine starts good and from idle to wot it revs fast and smooth with no hesitation or sputtering it does seem to flatten out around 5500 some times, and if I am cruising down the hiway at 3000 rpm then mash it it does hesitate a little then take off. I am also running 3.90-1 rear gears, street tunnel ram 2 500 eldebrocks

Reply With Quote Quick reply to this message
Sponsored Links
  #17 (permalink)  
Old 02-09-2013, 05:26 PM
F-BIRD'88's Avatar
Yada Yada Yada
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,153
Wiki Edits: 0

Thanks: 5
Thanked 380 Times in 374 Posts
this motor should pull strong well past 6000rpm. flattens out at 5500 rpm and or is inconsistant
weak valve springs. lack of fuel flow volume @ WOT. excessive WOT spark advance
restricted low flow exhaust system and or poor cylinder heads//stock small valves/poor stock ports.
carbs jetted too lean.

throttle response. This motor may well run best with locked out timing. The more idle timing you give a tunnel ramed motor the better it runs and the cleaner the idle and quicker the thottle response.

start tuning with locked out timing

From this point you can fine tune the edelbrock carbs. best done with a AFR gauge and vacuum gauge
a choice of primary metering rods power step up springs and jets. as well as different accel shooters.
The manifold must be warmed up to tune it or evaluate changes. A cold manifold will be balkky.
A tunnel ram takes longer to warm up. The locked out timing really helps keep the idle clean while it
is warming up. Keep the rpm up while it is warming up too.
replace fouled spark plugs. excess cold slow engine idling ///lack of idle timing.

The edelbrock's tech dual carb baseline set up is just a start point.
start by locking out the timing. 34 to 36deg BTDC.
tunnel rams need lots and lots of idle timing.

You will need to be able to fully adjust the vaccuum advance system to get it right..
start point... end point ,,,max limit and rate of vacuum advance.

Over all I find the 750 cfm edelbrocks the best most tunable carb,,,even when two are used on a tunnel ram.
The veloclty valve controled secondarys sizes the carb(s) to the engines air flow requirement.
The opening rate of this sec valve can be adjusted by changing in the weight of the counterweights.
This is the last thing that gets tweeked after every thing else is dialed in.
The near square equal size of the 750's throttles is better for a tunnel ram.
The carb CFM size selection rules don't apply to tunnel rams. small cfm carbs need just as much or more retune work
as a larger carb. Often more tuning changes and mods. The bigger carbs make more power.'
Tunnel rams like to breath deep to make big power.

If this motor seems to be nosing over WOT at 5500rpm it isn't set up right.
and or something is really choking it.
edelbrock carbs need a consistant 5psi fuel pressure @ WOT and enough fuel system flow volume to keep the carb full of fuel @ WOT.

Last edited by F-BIRD'88; 02-09-2013 at 05:51 PM.
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 02-09-2013, 06:43 PM
F-BIRD'88's Avatar
Yada Yada Yada
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,153
Wiki Edits: 0

Thanks: 5
Thanked 380 Times in 374 Posts
As far as tuning that last little bit of secondary thottle response
(when you jump on it from 3000 rpm cruise to WOT)

I got some good new for you.... and some bad news.
The good bews is every thing about the secondaries and how they work and dialing in the secondary fuel curve and air door opening rate is fully adjustable.

The bad news is its not easy or user friendly and takes a bit of advanced tuning knowledge and
a lot of patience and time to test and tune. tuning tools and the ability to make and reverse very small changes at a time.
Everything else about the carbs tuneup has to be 100% dialed in FIRST before you get the big idea to dig into the sec systems on these carbs.

The 500cfm carb(S) take just as much work to get them right as any of the different edelbrock carbs.
if you want to get it right you need to fine tune each carb circuit starting with the idle /off idle circuit.

A AFR gauge (can be {heated}narrow band type or wide band type) and a manifold vaccuum gauge are your friends.
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 05-11-2013, 06:50 AM
Registered User

Last journal entry: gus`s 40
Last photo:
Join Date: Jul 2012
Posts: 82
Wiki Edits: 0

Thanks: 3
Thanked 6 Times in 6 Posts
thanks f-bird88 for the info, I have my total timing set at 36 the initial is 16 and I hooked the vacume advance up to manifold vacume then re set the carbs it helped allot. I was getting a stumble from cruising speed on acceleration and the plugs were pretty light colored so off the edelbrock manual I went up two stages on mid and wot put the next lighter springs in and what a difference, it really woke it up and idles much cleaner and the plugs look good also.There is no more hesitations and seems run real good, on some of the stuff I read they say to go rich then back down to a lean condition to dial it right in but I am not sure I should mess with it any more it seems happy where its at
Attached Thumbnails
Click image for larger version

Name:	IMG_20121201_161737.jpg
Views:	55
Size:	954.7 KB
ID:	73936  
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply

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:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:


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
vacume advance zoey2 Engine 14 07-26-2011 10:47 PM
Yet another vacume advance question... 350pano Engine 3 04-08-2010 05:49 PM
vacume advance or mechanical advance? BigBlockT Engine 1 06-08-2009 07:05 PM
vacume advance problems cope Engine 5 03-28-2008 06:25 PM
Vacume advance question western star Engine 14 10-19-2004 03:46 PM

All times are GMT -6. The time now is 02:55 PM.

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