Go Back   MustangForums.com > Ford Mustang Tech > Classic Mustangs (Tech)
Sign in using an external account
Register Forgot Password?

Classic Mustangs (Tech) Technical discussions about the Mustangs of yester-year.

Welcome to Mustang Forums!
Welcome to Mustang Forums.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

Carb and intake swap problems with 289

Thread Tools Search this Thread
Old 03-28-2014, 07:08 AM   #1
Join Date: Mar 2014
Vehicle: 1968, Ford, Mustang
Location: PA
Posts: 13
Default Carb and intake swap problems with 289


i have a 68 289 with a c4 transmission. I just swapped the old 2v stock intake and and carb and installed a Edelbrock Performer intake and a Holley 600cfm carb. When i start up the car the idle is much faster than it was originally(but still smooth not jumpy) and i have turned it down as far as the carb will allow. I sprayed carb cleaner all around the the intake seals and i did not notice any change in the engine so i dont think its a leak there. Also when i shift into reverse the car jumps a lot more than it used to(can actually hear the tires squeek) and there is also a very noticeable hiss. When i put it in drive i was doing about 25mph with my foot off the gas which is very different than how it was. Any ideas as to what happened in the swap?

This ad is not displayed to registered or logged-in members.
Register your free account today and become a member on Mustang Forums!
ding56 is offline   Reply With Quote
Old 03-28-2014, 08:26 AM   #2
2nd Gear Member
racer_dave's Avatar
Join Date: Aug 2009
Vehicle: 1967 Mustang Fastback
Location: Michigan
Posts: 346

You turned down what to change the idle? The idle mixture screw? the linkage adjustment? Are the floats set correctly?
The gas pedal fits best right up against the firewall, so I figure it should be there as much as possile
racer_dave is offline   Reply With Quote
Old 03-28-2014, 09:07 AM   #3
Join Date: Mar 2014
Vehicle: 1968, Ford, Mustang
Location: PA
Posts: 13

sorry for being unclear, what i meant was that i turned the idle mixture screws on the side of the carb all the way down. i just went out and checked the bolts on the intake and carb and my fittings and found that there was a small leak in the line for the brake booster hose and i fixed that. Then i started it up and it would not hold idle so i had to give the mixture screws a half turn out and that fixed the problem. With it running i used my hand to cover the carb and it took 15-20 seconds of sputtering but she eventually died so it does not seem there is a leak that is at least letting in enough air to keep it running. When i shift into reverse or when i drive i still hear a pretty loud hissing noise that i cant identify. Also to note i don't have the air cleaner on right now as i need a shorter screw to secure it, could that just be the issue? I don't see why going from park to reverse or drive would cause a louder hissing all cause the air cleaner isn't there.

When i am in park i can rev the engine and i don't hear the hiss, just when i shift into reverse or drive. Also when i shift into reverse or drive the car has a pretty big lurch (wheels squeak a little). I do have a shift kit installed so i dont know if this is the cause but it did not lurch after i installed the kit but before i swapped the intake and carb. The transmission fluid level is not low, actually i think i over filled it so i need to drain a little out. Is there a way to do that besides dropping the pan?
ding56 is offline   Reply With Quote
Old 03-28-2014, 12:06 PM   #4
Gun Jam
Gun Jam's Avatar
Join Date: Dec 2005
Location: Hills of California
Posts: 4,423
Send a message via ICQ to Gun Jam Send a message via AIM to Gun Jam Send a message via Yahoo to Gun Jam

ugh.....I guess ill be the one to ask.

Did you try adjusting the curb idle speed screw....you know the one you use to increase or decrease idle rpm?

Oh I see in your 2nd message it looks like you got it figured out

As for the hissing noise you'll have to check all vac lines

might not be a bad idea to replace them all anyhow


Masters of Industrial Technology intelligence thats why I own guns made to drop elephants.

Last edited by Gun Jam; 03-28-2014 at 12:11 PM.
Gun Jam is offline   Reply With Quote
Old 03-28-2014, 12:40 PM   #5
2nd Gear Member
Diputado's Avatar
Join Date: Oct 2012
Vehicle: 1965 Ford Mustang
Location: Puerto Rico
Posts: 199

Like Gun jam says...I'd replace all those old vacuum lines since you've already gone to the great expense and trouble of the new intake/carb.

Get a good vacuum gauge and use it to tune the carb to the highest vacuum you can get at idle. Just follow the instructions that come with the gauge. On that 600 Holley (I assume it's a model 1850?), you should turn the idle mix adjustment screws all the way in (clockwise) EASILY (not too tight)...and then back out 1.5 turns for the initial starting point. Once you get the best vacuum level possible via the idle mix, then readjust your curb idle speed.
1965 coupe, 289 +.040, 10.5:1 forged pistons, Boss 302 flywheel, Weiand Stealth, Holley 600, Crane cam, Hooker headers, Duraspark ignition, Toploader wide-ratio 4-speed with Hurst Competition Plus shifter, and 9" rear with 3.50 gear.
Diputado is offline   Reply With Quote
Old 03-28-2014, 05:27 PM   #6
Join Date: Mar 2014
Vehicle: 1968, Ford, Mustang
Location: PA
Posts: 13

I think i found the issue, the carb needed the idle speed turned down and the throttle linkage was getting hung upi installed an aftermarket tach and now im idling around 1000 rpm. The car still has a decent lurch when i put it in reverse through, any thoughts?
ding56 is offline   Reply With Quote
Old 03-28-2014, 05:39 PM   #7
3rd Gear Member
Join Date: Nov 2013
Vehicle: 1965 shelby
Location: arizona
Posts: 967

remove the throttle linkage.

what carb is it exactly?

is it new?

make 110% sure that the idle screw on your choke linkage is NOT touching the little metal "cam" as suggested earlier. if it is, your regular idle screw will not work.

Disconnect ALL vacuum hoses from the carb and plug the ports at the carb.

you can also do them 1 at a time to see if the hissing stops and the idle lowers.

you might have a leak at the lid for the diaphragm on the vacuum pod for the secondaries.

your secondaries may not be fully closed, make sure they operate freely and are closing. to do this look at the little stop on the passenger side and make sure the arm hits the tip of the screw stop..

if the problem still exists it is an air leak at your carb base or intake at the cylinder head.

the intake might be leaking on the bottom side. if it is you can not test for that. you need to remove it and try again.

take a can of brake cleaner that says FLAMMABLE on it. stick the long plastic nozzle on it and GENTLY and SLOWLY spray for leaks.. if you have one you WILL find it using this method.

most brake cleaner is NOT flammable these days.
barnett468 is offline   Reply With Quote
Old 03-28-2014, 05:39 PM
Ford Mustang

Paid Advertisement


289 engine, carb issues, intake manifold problem

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not 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 Off
Pingbacks are Off
Refbacks are Off

Forum Jump


Featured Sponsors
Vendor Directory
New Sponsors
All times are GMT -5. The time now is 12:04 AM.

© Internet Brands, Inc.

This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford® is a registered trademark of the Ford Motor Company
Emails Backup