Engine Run-On: 400 Tri-Power - 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
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 09-28-2012, 12:13 AM
Registered User
Join Date: Sep 2012
Posts: 1
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Engine Run-On: 400 Tri-Power

I'm working on a 66 GTO with tri-power, fresh rebuilt 400, 9.5 to 1 comp, round 490 lift roller cam. My first problem is that is runs on. I've tried multiple carbs, changed timing, colder plugs. And all with block off plates on the secondaries. Any advice?

Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 09-28-2012, 06:07 AM
Registered User
Last photo:
Join Date: Jan 2011
Location: Hopewell, Va
Age: 65
Posts: 1,684
Wiki Edits: 0

Thanks: 1
Thanked 192 Times in 179 Posts
Engine Run-On: 400 Tri-Power

Do a search on this website on tuning a 400 with tri-power. It will tell you what carburetors that you are suppose to use. The center carburetor has the idle circuit and choke. The other two do not have an idle circuit and choke. The outer 2 carbs are on a progressive linkage so they are only used during 3/4 to wide open throttle.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 09-28-2012, 08:49 AM
vinniekq2's Avatar
Registered User
Join Date: Jun 2012
Location: BC,Canada
Age: 59
Posts: 11,638
Wiki Edits: 0

Thanks: 693
Thanked 1,340 Times in 1,243 Posts
Idle stop solenoid is a good band aid
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 09-28-2012, 11:33 AM
Registered User
Join Date: Nov 2011
Location: Virginia
Posts: 877
Wiki Edits: 0

Thanks: 2
Thanked 133 Times in 116 Posts
How did you "arrive" at that 9.5:1 spec?

Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 09-29-2012, 11:32 AM
Thumpin455's Avatar
Ask me about Ethanol

Last journal entry: 65 GTO
Last photo:
Join Date: Aug 2009
Location: Michigan's U.P.
Posts: 155
Wiki Edits: 0

Thanks: 0
Thanked 4 Times in 4 Posts
Yep, need to know what heads and pistons you are running to get 9.5:1. The differences in heads that will fit a 389/400 can make it ping or run on easily. Can you tell us what the number is cast into the center exhaust ports, if there is one there? Need to start somewhere, might as well be with the combination you have.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 09-30-2012, 06:09 AM
Last photo:
Join Date: Dec 2004
Location: San Antonio, Texas
Age: 53
Posts: 4,023
Wiki Edits: 0

Thanks: 0
Thanked 26 Times in 26 Posts
Run on is caused by too much fuel in the chamber after shut down.

Big cams require lots of timing. I would use at least 20 degrees at idle.

In most cases this is what happens: Low timing brings down the idle speed, so the idle speed screw is used to increase the rpms, this will put the throttle blades past the idle circuit and into the main circuit which causes a very rich idle. Making it run on after the engine is shut down.

Advancing the timing and lowering the idle speed screw will cure run on.

If the carbs aren't letting enough air in at idle speed to keep the throttle blades in the idle circuit then you will need to drill a few small holes in the throttle blades or crack the front and rear carb open a bit.
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:
Please select your insurance company (Optional)


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
Tri-Power speedball Hotrodders' Lounge 44 10-11-2011 03:46 PM
Tri Power Help!! jgreene6611 Engine 4 04-23-2008 08:59 PM
tri-power help caplock Engine 1 07-20-2006 05:40 AM
tri-power pepi Engine 18 02-17-2006 07:23 AM
tri-power fred56 Engine 3 11-18-2002 02:25 PM

All times are GMT -6. The time now is 05:12 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.