All Small Six '67 Mustang stalls after Clifford headers w/ dual Magna-Flow exhaust installed

This relates to all small sixes
Finn

Finn

New member
I recently had a new set of Clifford Performance headers installed on my 1967 inline-six Mustang coupe, along with a pair of Magna-Flow mufflers. The car was running nicely before (I know, I know: so why did you fix it if it wasn't broke?....)

As per Larry at Clifford, I had the shop use 2.25" pipes. The car starts but I have to really rev it to keep it going and, if it's in PARK, as soon as I take my foot off the gas it stalls. I managed to drive the car home from the shop because I had no choice getting home otherwise but it was a pretty tense drive.

The headers are the 53-0186 6=8 Headers Ford 200 for 1964 & up.

Could this be caused by an exhaust leak somewhere? If so, how do I check? Should I take it back to the shop? What other factors should I investigate?

Really appreciate any and all help!
 
Long distance diagnosis is difficult. Lots of detail and pic help. We got neither. I am tempted to pop off (uninformed) and say "Sounds more like a blockage thana leak." but that would B foolish on my prt.
Whenever U allow some1 else to service ("fool w"/in my language) ur rig they R responsible. Do not leave a shop w/problems U did not come in w/. Walk back in immediatly on key turn and explain nicely "Something's up guys?" It may not B too late for this by phone. Do U use them often? Was this 1st visit?
How long has it been out of their shop? What else can U describe (noise, shakes, smells, sounds, etc)? Do U know what a kick dwn cable is? Has it been adjusted properly...
 
Now that you have this much freer flowing exhaust system installed you will need to take some time to retune the engine. The effecancy of your engine has gone up substantially so you will now need to rejet the carb probally about one or two jet sizes larger to start with and as well as adding some more base timing too to take advantage of the power potential that you now have. Good luck on the tuning.
 
You say you had a Shop install the headers ? My guess here is you could have a vacuum leak since the Intake has to go on with the new header. Yes, you just need to take it back to the Shop, because it should at least idle and not die from their work... And like bubba was saying, your free flowing exhaust now will most likely cause the fuel mixture to need to be adjusted... The Shop should not have let your Car leave with it wanting to stall, and they should go back over that. But a tune and re-jet on your carb. would be extra money.
 
Finn said:
I recently had a new set of Clifford Performance headers installed on my 1967 inline-six Mustang coupe, along with a pair of Magna-Flow mufflers. The car was running nicely before (I know, I know: so why did you fix it if it wasn't broke?....)

As per Larry at Clifford, I had the shop use 2.25" pipes. The car starts but I have to really rev it to keep it going and, if it's in PARK, as soon as I take my foot off the gas it stalls. I managed to drive the car home from the shop because I had no choice getting home otherwise but it was a pretty tense drive.

The headers are the 53-0186 6=8 Headers Ford 200 for 1964 & up.

Could this be caused by an exhaust leak somewhere? If so, how do I check? Should I take it back to the shop? What other factors should I investigate?

Really appreciate any and all help!
Click to expand...
It sounds like they may have knocked a vacuum line off some where. The intake manifold is on that side of the engine, which is where they'd come from. I'd suggest looking there as a start. Don't forget the one that goes down to the transmission.
 
I forgot that those had an integral Intake manifold to the Cylinder head. I have to assume it still has that... Like from above statement, a vacuum hose off somewhere. The Shop should have let your car leave like that.
 
Finn said:
I recently had a new set of Clifford Performance headers installed on my 1967 inline-six Mustang coupe, along with a pair of Magna-Flow mufflers. The car was running nicely before (I know, I know: so why did you fix it if it wasn't broke?....)

As per Larry at Clifford, I had the shop use 2.25" pipes. The car starts but I have to really rev it to keep it going and, if it's in PARK, as soon as I take my foot off the gas it stalls. I managed to drive the car home from the shop because I had no choice getting home otherwise but it was a pretty tense drive.

The headers are the 53-0186 6=8 Headers Ford 200 for 1964 & up.

Could this be caused by an exhaust leak somewhere? If so, how do I check? Should I take it back to the shop? What other factors should I investigate?

Really appreciate any and all help!
Click to expand...
I just did a ebay split header install with a 2 1/4" dual exhaust from summit on my 67 vert 200/c4. It has a holley sniper on a small log head & I have limited drive time in it with the headers.

But today while I was installing a radio in her I had to move it in & out of my car storage I noticed that the idle was stumbling around and before its always been smooth. I was fooling with the AFR on the sniper monitor & leaned her down & the idle smoothed back out.

You probaly have a fuel issue or maybe a vacumn leak.
Probably fuel since the engine can breathe some better with the new exhaust.
 
After watching the last engine masters show exhaust and mufflers really don't do much. lol.

But as everyone said check for a vacuum hose. There are diagrams if you do a google search or a shop manual is a great reference.
 
Does your carb have an electric choke, or is it supposed to use the hot air tube from the exhaust manifold ?
If the hot air system, I doubt that the sop installed a replacement heat tube from the header to the carb ?
Also check for vacuum leaks as others have stated.
DannyG
 
65coupei6 said:
After watching the last engine masters show exhaust and mufflers really don't do much. lol.

But as everyone said check for a vacuum hose. There are diagrams if you do a google search or a shop manual is a great reference.
Click to expand...
Did'nt see the show but after years of fooling with car I myself think any car benefits from a less restrictive exhaust system whether dual exhaust to stock manifolds or to headers.

Mufflers not so much mostley for sound. If the show had dyno pulla on it with before & after graphs they were probably v8's.

I would have to see some before& after pulls on a dyno of a stock 200 before I believe a header & dual exhaust did'nt do anything for the power.

Mine was better all round with the Sniper install on the stock motor then still better with the header& dual exhaust install.

You have to take those shows with a grain of salt & compare apples to apples
 
Im guessing it is choke or a vacuum leak.

Also IMO 2.25 duals is to big for a 200.

Ive got dual 2" on my 289 and am going with the same on a 250.

2" is fine unless you are putting down more than 300hp, otherwise its just more cost and weight to haul around.
 
DannyG said:
Does your carb have an electric choke, or is it supposed to use the hot air tube from the exhaust manifold ?
If the hot air system, I doubt that the sop installed a replacement heat tube from the header to the carb ?
Also check for vacuum leaks as others have stated.
DannyG
Click to expand...
No electric choke; it has/had the hot air tube from the manifold to the carb. The Clifford header does not have a port in which to insert that tube (right now the tube is on the passenger side floor.) As you and others have suggested, I will check all the vacuum lines and see if one is disconnected. Thank you for the help.
 
Really appreciate all the rapid responses to my distress signal!

As I replied to DannyG, I'm gonna go over all the vacuum lines (including that one to the transmission), as well as the fuel lines. I will also look into adjusting and re-tuning the engine (timing, fuel mixture, etc.)

I called the shop which installed the system and they told me it wouldn't stall if there was an exhaust leak and that they always check a new installation for exhaust leaks. They also said I was welcome to bring it back and they could go over the vacuum lines, but I'd rather try that first myself since driving a stalling Mustang with automatic transmission in traffic is a cause for high blood pressure.

Chad asked for any other "symptoms" but the only issue seems to be that it stalls once you let up on the gas and the RPMs drop. No smoke, no fumes, no strange sounds.

Any other insights or guesses are appreciated but it sounds like the tribe consensus is: check vacuum and fuel. Thank you and I'll update you!
 
"... tribe consensus..." aahahahaa
yeah, we gota optimal build "by committee" goin on @ nother thread. The ford6 team ! We Go Guys !

"kick down cable, auto's vac modulater, ign tune then onto carb tune, open vac loss, choke" sounds like a cmmttee !
(my prt time work is consulting them).

What color is ur stang?
 
You never know. It could be unrelated to the install. Check your fuel pump and filter. Also headers create more heat under the hood. Check your fuel lines. Are they metal? Any pictures of your engine compartment?
 
chad said:
"... tribe consensus..." aahahahaa
yeah, we gota optimal build "by committee" goin on @ nother thread. The ford6 team ! We Go Guys !

"kick down cable, auto's vac modulater, ign tune then onto carb tune, open vac loss, choke" sounds like a cmmttee !
(my prt time work is consulting them).

What color is ur stang?
Click to expand...
The Tribe hath spoken!

My Mustang is Wimbledon White -- that's me sitting on the hood (when cars were made so you could actually sit on the hood....)
 
If your carb uses a hot air choke tube you can make a new hot air tube to hook up to the carb's choke so that it works again with those new headers. Use some steel brake / fuel line or one of the aluminum choke repair kits (from the Help section of your local auto parts store) than coil the new line severial times around one of the center header tubes be sure to use the stock type insulation sock around the top part of the tube from just above the header all the way up to the carb hookup so that it retains the heat. Good luck
 
Problem solved! It was kind of a vacuum leak and a fuel issue: my carburetor was quite loose where it bolts to the top of the manifold. Once I tightened it down, the car runs and idles, though I do need to tinker with the idle speed and the mixture dial on the side of the carb. It runs a little faster then a little slower, a little faster then a little slower.

Just returned from a "victory lap" around Princeton and it really has some get-up-and-go off the line. There doesn't seem to be that lag I used to have when pressing the accelerator. And it sounds grrrreat!
 
pretty soon it'll run U out to Long Branch!
I'd trip from there dwn to Cape May summers when living in Haddonfield 8^0
 
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