newbie: 67 mustang, 289, timing/fuel issues

[shelby_daytona]

1967 Mustang Coupe, 289 was 2bbl. A new 4 bbl carb, intake manifold, cam and headers were just installed. It is running really rough, but its timing/fuel related, the engine ran fine before. I realize that I sound like an idiot here, but I do not have very much experience with tuning carburated engines. My questions are as follows. What should the timing be? Cam specs are as follows:

COMP CAMS FS 268H-10

INT EXH
ADV DUR: 268 268
DUR @ .050: 218 218
VALVE LIFT: .456 .456

LOBE SEP: 110.0

It is also running very rich. It is an Edelbrock 650 Thunder Series, 1805 Manual Choke. When you step on the gas it hesitates a great deal and sputters like crazy, when you are just party on the gas, it is okay, but as soon as you give it more it sputters and hesitates. The exhaust smells like pure gas, but we dont see any black smoke.

It would be greatly appreciated if anyone can give me some advice on this, and again sorry for the rookie question. Just trying to get an idea of what the timing should be. Thanks alot

Jay

 

[10secgoal]

Intake, Newbie, hesitation, just installed. Those all together in a post tell me one thing. Check your intake . Not sealing right is likely. The other that could be causing it is your fuel psi. Check to make sure it isn't too high. ALSO, check down the carb when it is running to see if fuel is pouring down the motor. Sometimes new carb get packing material stuck in the needle and seat. Tap the back left and right corner of the edelbog to see if you can dislodge it.

 

[StephenMarsh]

Certainly check the seating of the manifold and carb as has been suggested - you may not be "running" rich - you may just have a carb riser cavity with fuel in it or intake related vacuum issues. That can cause that bog you're feeling when you goose it a bit from idle. Your timing may also be a bit too advanced - even 2 or 3 degrees off and it can feel like the engine dives under water for a second and the re-surfaces with power (does that make sense?) when you hit the throttle.

Also keep in mind that the 289 likes pretty much 2 kinds of cams - really mellow or really aggressive - something in the middle tends to give pretty nasty idle performance and un-even power through it's range.

 

[shelby_daytona]

It is actually my freinds car, he doesnt know too much about them so I offered to try and dig up some information. I looked at the car but was stumped. I will take your suggestions, thanks. He had some back yard mechanic install all of the parts.

 

[Edbert]

Do Edelbrocks use a power valve like Holley's?

I've seen them give too big of a squirt and cause an initial bog like that. But I'm thinking a vacuum problem too.

 

[tos]

edelbog .

Thats funny 10secgoal. You must be runnin a Hoggy 750 double stumbler.

I agree, Check intake seal. Also you need to check for vacuum leaks from your vacuum ports. Check the base of the carb also for leaks and CRACKS. I dont know how many times ive seen the ear of a carb cracked because somebody tightened it too much. You can do a quick test for leaks by spraying carb cleaner around the intake at the heads aqnd around the base of the carb while the car is idleing and listen for a change of rpm. Other possibilities are valve adjustment (last resort), accelerator pump misadjusted (edelbrock is usually good right out of the box though), Double check firing order (you should here a little popping through carb or exhaust if this is the case). SLIM possibility is timing marks missaligned (off one tooth) during cam installation. One last thing- dont assume because you have a strong smell of gas that its a fuel problem. The amount of fuel you get is in relation to the amount of air sucked through the venturies. A vacuum leak will throw that ratio off so thats where I would check first then work towards fuel probs. Good luck.

 

[shelby_daytona]

hey thanks guys, im gonna go check it out right now, ill let you know what happens.

 

[shelby_daytona]

the PCV hose was cracked, so we fixed that... then we decided to time it, and got it to run best down around 12*... it seems to run good and actually had power to break em loose, so now we have to figure out the carb tuning. What was done, was: two screws (a/f mixture), we turned the right one all the way in until it almost died then backed it off 3 turns until it gained rpms. We did the same for the left screw. Both were backed off the same amount. It seemed to run alot better.