1985 302 ho carbed not running smooth above 2000 rpm?

[DarinH]

Its the factory fuel pump so idk it would be too much psi? I checked the plugs there a little on the grey side. I do think its to lean there is no black smoke at all. I put accel wires on it two months ago.

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[DarinH]

Gonna throw on an edelbrock 600 this week and see if I can change the metering rods to make it richer and see if it cleans up.

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[PaceFever79]

First, that fuel pressure is way too high... 5-6 psi for Edelbrock, no more than 8 for a Holley (15 psi will flood either one)

If that doesn't fix your problem......

Take a vacuum reading. if you have a mild cam it should read 14-18" with a steady needle.

Next do a balance of power test. (I have an old Sun Tune machine to do this, but you can also do it manually)

Note your exact idle speed, then remove one plug wire, and carefully note the idle RPM drop... the RPM drop should be uniform. If you find one that is not reducing the RPM as much, that is the cylinder you need to focus on.

[PaceFever79]

Another part to check is the coil.... Sometimes a bad coil can produce good enough spark to idle, but as the RPM increases it can't cycle full saturation fast enough to keep up with the increase in firing speed.

[JACook]

Couple more comments. If the engine idles cleanly, we can be fairly certain that the fuel level in
the bowls is not rising higher than it should, but that doesn't mean the bowl level might not be low.
I've seen the bowl level be incorrect out of the box on these "non-adjustable" 4160s (an unfortunate
cost-cutting move, IMO, since you can't just remove the top to have a look).

Steady-state light-throttle is where marginal ignition components will show themselves, because it's
usually where a lean mixture combines with vacuum advance, and EGR, if present. These all tend
to increase the voltage required to jump the spark plug gaps. The factory ignition system is more
than up to the task, but only if it's in good condition, and using quality components. No fancy coils,
modules, or distributor required. What kind of distributor did you install? What kind (brand) of
ignition module?

Not sure why one would want to try yet a third carburetor. If the 600 didn't change anything, I would
go back to the original, rather than keep adding variables to the equation. Fattening up the mixture
might make things better, but that doesn't necessarily mean it was too lean.

At this point, the shotgun approach isn't working, perhaps we go back to the beginning, and think about
what was changed before this problem began?

[PaceFever79]

I agree with Jeff,

I suspect a misfire issue... but a more scientific approach is needed.

I'm on the road, so I'll let Jeff walk you through!

[DarinH]

Well the only I an trying the edelbrock is because the holley 600 was just borrowed till my buddy built his engine I got a edelbrock performer 600 with a tune kit from a friend for 60 $ so I fig I could just give it a shot since edelbrocks are easier to tune than holleys. As far as the dizzy goes it was just a premium oem replacement I got at orielys. I see no need for an Aftermarket one, since the duraspark 2 in these cars are great any ways. The icm is a BWD select also from oreilys.

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[JACook]

What about the original carb that was on there before the 4160? If the 4160 didn't make things better,
seems like the original carb is more of a known quantity.

[DarinH]

I wish I could go back but this car has done this ever sincen I've bought it so who knows what someone else did??? I must say

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[86VertMK]

Is the vacuum advance connected to the timed spark port of the carb? Or is the vacuum advance seeing manifold vacuum all the time?

[DarinH]

Its on the spark port fitting


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[brianj]

My gut feeling is more ignition than fuel, but it is hard to diagnose over the internet! I personally prefer the Edelbrocks, but be aware that a stock Ford mechanical pump will put out too much pressure for one- it says so right in Edelbrock's tuning guide. If the fuel is not the problem, you will just add the car running pig rich at idle to the problem putting that carb on without a regulator or the correct pressure pump. I really think you need to do some more digging into the problem- maybe try looking more at the ignition side.

[JACook]

Whether or not the car was doing the same thing with the original carb, changing it did not make
any difference. The odds of getting two random carburetors with the exact same failure... Not
unpossible, but also not the way I'd be betting.

Is the vacuum advance connected directly to ported vacuum? Or does it still connect through the
ported vacuum switch at the rear of the intake? Does this engine still have EGR on it?

[DarinH]

I agree that it def feels ignition wise to me I just am at a standstill with it.. every part of the ignition is new. There is no egr part on this car. The heads have plugs in the back and most emissions stuff has been removed.

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[DarinH]

I appreciate you guys being so helpful though. Theres better help on this forum than u would get from any mechanic shop!!!!!

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[grabbergreen84]

The icm is a BWD select also from oreilys.

Any of your buddies have a correct factory Ford DuraSpark module you could borrow and try out?

Learned that here!

[DarinH]

No everyone has msd boxes they think there better.... I will put my $ into other parts. Durasparks are used by many chevy guys with rods so that's gotta say something!

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[bwguardian]

Check the wires at the ignition module where the plugs are. The insulation on the wiring right around the plugs tends to deteriorate which leaves bare wiring. I see this condition on alot of cars with the stock ignition still in place.

[JACook]

Well, if you could borrow an MSD for a test, that wouldn't hurt either. The Ford distributor will
trigger an MSD just fine. Being's the MSD has a direct connection to the battery, that would
also bypass any suspect wiring or ignition switch. I would also try to borrow a Motorcraft,
Standard, or MSD Blaster 2F coil. Are you using the Accel 8140 coil? Or 8145?

Otherwise, do make sure the Duraspark module is receiving full system voltage on the red wire.
The Duraspark system uses a ballast resistor, but it should only be in line with the coil. Also
make sure the ignition system has a good ground. The system grounds through the black/light
green wire (aftermarket module may just have a black wire) to the distributor body.

[DarinH]

I have a super stock coil (the yellow one) mine is a duraspark 2 system. .. I don't think I seen a ballast resister anywhere on or near the coil or wires leading to it????

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[JACook]

There are two versions of the SuperStock coil, with different primary resistance, why I'm asking which
number is on yours.

Ford did not use a ballast resistor block like other manufacturers did, it's a 1.3Ω resistance wire in the
harness between the coil and ignition switch (unless your car was originally TFI...)

[DarinH]

I have the accel 8140 coil... and no my cars numbers cross to the 4bbl 302.

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[JACook]

Numbers being the transmission code, I hope? The engine code in the VIN is the same for both 4V and CFI.

The 8140 coil should be fine. I would have my doubts driving the 8145 with a blue-grommet Duraspark box,
as it's got the same primary resistance as the factory coil that required the California-only red-grommet box.

[DarinH]

Oh ya the code is the same I forgot.. but ya my car doesn't have the wiring for the cfi....or at least it doesnt now. I know the 5 speed was factory. I thought the cfi only came with auto trans??

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[JACook]

I thought the cfi only came with auto trans??

Correct.