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Discussion Starter · #1 ·
Before - 289/ rebuilt original heads/cap,rotor plugs,wires,filters(air,fuel,oil) changed/upgraded Performer cam/Aluminum Intake/600cfm 4v Edelbrock carb./and pos exhaust w/standard exhaust manifolds.

Ran very well. Would squeek the tires w/out using the brakes. Good pulling power.



Now - Just had someone put on a custom 2" exhaust w/Flowmaster Mufflers and Nickel plated Tri Y headers.

Runs pretty good except (1) I can't even squeek the tires now and (2) Will stall sometimes when the pedal hits the floor at a standstill.


Not that I'm out racing or beating on this 40 year old car, but was just doing some testing and comparisons. I was expecting 15-25 hp gain, but it almost feels like it has less pulling power than b/f. Doesn't make sense to me. The only thing I can think of is that the carb. and timing need some adjusting????

Thanks for any help and or advice you can provide.
 

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Headers are funny things. They are not the broad performance enhancement that most people think they are. The length and diameter of each section of pipe in a header determine the RPM range in which the header will make the most improvement...

But I paraphrase... Read the following article from the AFM Tech pages:

Engine Performance Theory

Probably not what you wanted to hear, but it may help you understand why you are not getting what you thought you would out of the headers, depending on how they're configured, of course...

I suspect, however, that your problem with stalling the engine is entirely different. You should not be able to stall that engine. Period. Carb and timing, as you note, are good places to start. Might replace the vacuum tube to the vacuum advance. Check your points, if you still have them.

Does your carb have vacuum or mechanical secondaries?
 

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Discussion Starter · #3 ·
"Does your carb have vacuum or mechanical secondaries?"

Don't know. All I now is that it is a new Edelbrock 600cfm w/electric choke.

I know what you mean about headers, but the fact is installing them along w/a new exhaust should improve not hinder performance. I found out today that the timing was adjusted, but the carb. was not touched. This along w/some input from a few other forums lead to the conclusion that the car might be running lean and needs to be re-jetted.

Hmmm....re-jetting sounds complicated. Might need someone to look at it.
 

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headers..more or less performance.

you say you lost power and it feels a bit more sluggish? Well remember that the engine needs some amount of back pressure to produce torque that is usable. Your headers may give you more top end power (higher reving) but also can decrease the torgue that the motor makes. Thats my guess.

Im not a mechanic, but thats my .02 cents!

Ive debated whether to go with headers on my 66 A-code 289. Its got the factory single exhaust, and Im going to install duals at some point. Dont plan on any internal mods, just want a better rumble sound that duals give.

Treeman
 

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According to Edelbrock's website, it has air velocity secondaries, so that's probably not your problem...

You shouldn't need to have it re-jetted. Rich / lean issues can be caused by idle mixture problems (remember that your idle jets still dump fuel into your carb even when you're not idling) and float maladjustment as well. I would suggest that you look through the owner's manual for your carb and find out how to adjust these things before you take it to a "professional"... I'd provide you the info myself if I had it, but it looks like Edelbrock is a little more stingy with that information than Holley is...

Also, if the guys who installed your exhaust system are the ones who adjusted the timing... er... check it yourself. :) It should be 6 degress BTDC.
 

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Often, adding headers will inprove the scavenging of the exhaust out of the cylinder leaving more "space" for the incoming fuel/air mix and less contamination by leftover exhaust. That often leads to the need to "richen" the carb to compensate for the greater cleanliness of the charge. There is no leftover exhaust, therefore there is more air, which needs more fuel to maintain the same mixture.

I'm not sure where Treeman got his info, but as long as the header pipes are not too large, they will aid low RPM torque and high RPM HP. They are simply a more free flowing trail for the spent exhaust to exit. Back pressure is needed for newer EFI motors, but even they will benefit from a free flowing exhaust. Visualize the engine as an air pump and you will quickly realize that in order for air to get in, it must get out, and the quicker and easier it will exit, the less power is needed to push it out.

You probably need to check your accelerator pump setting, squirter size, and timing of the pump. Then reset your initial timing to ~10*-12* BTDC, adding performance components generally means increasing the amount of timing advance(the rate) and increasing the initial setting.

JMHO :)
 

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Edelbrock carb

HI,
I have some experience with these carbs w/ larger than stock cams. I will say that from a simplicity standpoint, these carbs are wonderful. You can change the 4 jets and 2 metering rods without removing the carb from the car and the gaskets are robust enough to handle repeated disassembly without leaks. Edelbrock sells these carbs in 2 distictly different setups. One is a general purpose performance setup and the other an economy model. Either way, you need to get the rebuild kit to dial them in. I would start with changing to the big accelerator pump shooter and move it to the center hole on the pump arm. Next, drop one size on the metering rods...they come out through the top of the carb and are located under two oddly shaped plates that are held on with a torx. If it still stumbles, move the accelerator pump rod to the hole closest to the pivot point. If it doesn't stumble but seems to be starving a touch during acceleration, bump it up another rod size. Remember, the drop in manifold vacuum during acceleration is what causes the metering rods to move. During idle and while cruising, these metering rods restrict the primary jet. In closing...these carbs are extremely easy to work on. Once you get to know 'em, you'll love 'em!
Jerry
 

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To respond to Putts "I'm not sure where Treeman got his info....." I was merely saying too-big of an exhaust can hinder low end performance...He said he has lost the ability to chirp the tires, telling me he lost some low-end power. My info comes from some experience and this article that was in the June 2004 Mustang and Fords mag...

http://www.fly-ford.com/MustangFords0404-SoundsRight.html

I the article it says that pipes that are too large take away back pressure which engines need for better low- and mid- range torgue. It also goes on saying pipes too large can affect high-end horsepower..so its a balance...

Just to clarify myself.....
 

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:what: Not to take away from any sponsers, but the Zone has the kit for 75 bucks. I went the next size up on both, and reset the floats, and my car runs way better than it did before. Edelbrock carbs are a piece of cake to work on, just like Jerry said. I was also told that these carbs don't need over 5psi, so I bought a regulator too, just to make sure.:cooldude:
 

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Discussion Starter · #12 ·
Well, after some timing adjustments, it runs 100 times better. No hesitation and alot more power. I didn't realize how much timing can affect performance.
 
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