At a loss!

stepheje · Jul 25, 2007

My son replaced Edelbrock performer intake with RPM intake on modified 289, After engine gets warm and when running in power band, engine looses vacuum and begins to run rich and dies. Checked for vacuum leak, none found. At idle draws 20 inches, at 2000 RPM draws 23 inches, when you rap it, falls to nothing and then builds back up. Under load, forget it!

scrutmonkey · Jul 25, 2007

not a pro at engine stuff, but thought I might chime in...on some cams I have read that some people need a vacuum reservoir too keep up with the vacuum needs of the engine. Just a thought, I;m sure more knowledgeable stangers will post.

Rusty67 · Jul 25, 2007

Rev the motor to like 1000 rpm or 2000 rpm and see if it starts to choke. If it does but stays alive, take some carb cleaner and spray it at the edges of the intake manifold. See if there is a spot where spraying it will kill the motor.

Sounds to me like the intake isn't on right and there is a vaccume leek.

Edit:
Also, rechech the torque sequence used on the intake.

Vinyl66 · Jul 25, 2007

It sounds like the intake is not sealed correctly. Do the carb cleaner test as Rusty suggested. Spray it in different areas around the manifold as well as where carb meets intake with engine idling to see if the engine changes rpm. If it does you have a manifold leak. Did he follow the correct torque sequence as well as torque settings?
It should be done in a criss cross pattern and torqued a little at a time until the final torque is reached.

D.Hearne · Jul 25, 2007

With that much vacuum, I doubt you've got a leak. Sounds like the carb has issues or the T-Stat is in backwards and the engine's starting to overheat when the problem occurs. When the intake warms up, it would then tend to seal any vacuum leak not open one up. Did you seal off the heat crossover passage (or does the RPM have one?)

stepheje · Jul 26, 2007

Thanks for the input,

OK, We checked all the intake bolts and did the carb cleaner trick. This was my first suspicion as well, however, still have issues. I will say I am heading toward carburation. I do not understand edelbrock carbs but they have rods and springs and jets. Is it possible the new intake has changed the step up or down and at low vacumm / high load and we are not adjusted correctly and are flooding out? I will say when the car is finally started, it does act flooded, lots of smoke and have to floorboard accelarator?

Rusty67 · Jul 26, 2007

Smoke from where and what color is it ?

stepheje · Jul 26, 2007

again, in idle no problem, when you put it on the road and run through first gear, lights it up. As tranny shifts into second and then into third, start loosing power and dies. When you try to crank it, you have to depress accelorator to floor, black smoke out the exhaust and rough as heck!

When you crank cold, no probloem! No smoke, sounds great.

oscart · Jul 26, 2007

I don't think it is a vacuum leak since you said it pulls good vacuum at idle. There really is no vacuum in the intake once the throttle plate if open on the carburetor. Don't confuse air flow with vacuum as they are not the same. Sounds more like a vacuum advance problem, meaning you aren;t getting any ignition advance when accelerating. Check you vacuum advance canister to see if it is working. You can suck on the hose to see if the diaphram works or you can buy a tester. Also, check the vacuum line for kinks. Also, where did you connect it? Double check you ignition timing as well.

stepheje · Jul 26, 2007

Thanks again,

Back to the garage this evening. We have an MSD igniton and have the vacuum line hooked up from the left port on the carburetor. Timing has not been checked. Am not sure where timing should be with cam and rollers and eletronic ignition. I have always gone by ear? Sounds good, feels good, must be right.

JES

65ShelbyClone · Jul 26, 2007

If the ignition wasn't advancing, the car would be sluggish and the headers would be glowing red.

stepheje said:
When you try to crank it, you have to depress accelorator to floor, black smoke out the exhaust and rough as heck!.

That is indicative of flooding. Is this a new carburetor, or the one that was on the car before the intake change? I don't know that much about tuning or troubleshooting Edelbrock/Carter carbs, so I'll leave that to someone who does.

Rusty67 · Jul 26, 2007

65ShelbyClone said:
If the ignition wasn't advancing, the car would be sluggish and the headers would be glowing red.

That is indicative of flooding. Is this a new carburetor, or the one that was on the car before the intake change? I don't know that much about tuning or troubleshooting Edelbrock/Carter carbs, so I'll leave that to someone who does.

You wana trouble shoot an Edelbrock ??? Put a Holly on it

mustangmike6996 · Jul 26, 2007

sounds to me like you need to check all of the vacuum lines and linkage to the carb. ... no blockages or incorrect installation.... i mean at worst remove the intake and try again.. make sure you do not put on too much RTV to seal it tho..also pull all of the plugs on at a time to see how the electrode is... black clean.. oily.. or what have you... make sure they are all uniform..

mustangman1974 · Jul 26, 2007

stepheje said:
Thanks again,

Back to the garage this evening. We have an MSD igniton and have the vacuum line hooked up from the left port on the carburetor. Timing has not been checked. Am not sure where timing should be with cam and rollers and eletronic ignition. I have always gone by ear? Sounds good, feels good, must be right.

JES

Make sure the vacuum advance for the distributer is on the passenger side vacuum port.

If its loading up after acceleration check to see if the metering rods are straight. I have bent a couple being lazy when not removing them before taking the top off the carb.

When you check the rods clean the bore and plungers.

Whats the temp when it loads up?

Might want to run a vacuum line from driver's side vacuum port to inside with gauge and watch the gauge when the car runs like crap.

Also try a propane torch for checking for vacuum leaks. Turn on torch, but don;t lite it and follow intake gaskets, vacuum hoses, and trans modulator lines. Propane is thinner then carb cleaner and will find small leaks that carb cleaner won't

ForceFed70 · Jul 27, 2007

You know it's normal for vacum to drop off when you put your foot into it right? At full throttle you should have almost 0 vacum.

Does not sound like a vacum leak to me. Maybe problems with fuel supply? Pinched hose or plugged filter?

Rusty67 · Jul 27, 2007

BottleFed70 said:
You know it's normal for vacum to drop off when you put your foot into it right? At full throttle you should have almost 0 vacum.

Does not sound like a vacum leak to me. Maybe problems with fuel supply? Pinched hose or plugged filter?

H-O-L-Y CRAP... I didn't even think of that. Maybe he put the fuel filter in backwards ?

stepheje · Jul 27, 2007

OK,

I am back. Definitley not a vacuum leak. Definitely getting gas. Definitley cranks up cold and runs for about a minute like nothing was wrong with 20" vaccum. One minute later, begins to load up steadily loosing vacuum 15, 10, 0 and then muerto!

Definitely flooding out. Temperature will be at 160/180 when this occurs. When try to crank, nothing but raw gas in pipes and have to floor pedal to get it cleared out. Once running, it continues for about a minute and loads up and dies again.

Less than one year old Edelbrock 650 with auto choke. Has MSD with electronic curve and vacuum advance assist hooked up to passenger side port of carb.

I did change to thicker rods in order to minimize flow. Little better but still no real improvement.

This little engine produced about 320 HP with prveious intake with standard distributor but now, it is crap!

mustangman1974 · Jul 27, 2007

try to run without electronic curve. It is possible its messing with everything. at 20 in it may be way to advance then settling down and retarding the vacuum. The edlebrock tries to compensate by given it gas.

69PaleHorse · Jul 27, 2007

This sounds almost exactly like what happened to me a few years back. I had a similar issue, though my carb was a holley and the float bowls had taken on fuel. There were a few other problems that required a rebuild of the carb, but it was quite frustrating to get the car started, drive about 5 miles and have it sputter out and die on the side of the road. Looking down through the carb I could see lots of fuel sloshing onto the intake.

Check the float bowls (I think Edelbrocks still have those) to see if they are alright and the fuel level is not too high. If the fuel level is too high, I would expect heat would exacerbate the issue.

stepheje · Jul 30, 2007

Gentlemen,

I thank you for your input.

Finally resolved too much gas as many of you indicated. Pulled top plate off carb, found a steel shaving under the carb pump. Would n ot let pump close. Looked like someone drilled out a .125 hole and the shaving was never cleared. Anyway, cleared shaving and then changed jets to one size smaller.

Car cranked and runs like it is supposed to again. By the way, kind of like going to the doctor. My son failed to tell me he took car to machanic and they drilled a hole in the butterfly to assist the carb in tuning? (after we found the shaving)

So, Too much gas!

At a loss!

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