67 GTX 440 - Poor Driveability Issues, Need Help

[TxDon]

(Warning - long post)
I've had my GTX for about 8 months now, its a 440 with 4-speed and 3.54 Dana. It had a stock spec restoration back in 2001 and has been well kept since then. I love the look, ride and handling of the car but I'm not happy with the way the engine runs. Somewhere between 2001 and now the engine was modified as follows:

• Very lumpy cam, no idea of the specs.
• Mopar Performance "Wedge" intake manifold
• Edelbrock 1411 750 cfm carburetor
• Electronic ignition distributor, Pertronix coil, no ignition module.
• Aluminum radiator.

Everything else appears to be stock although it is so loud I think the mufflers may just be stock appearing shells. It starts OK and sounds very wicked with that "fairground" idle but the performance just isn't there. It only pulls about 12 inches of vacuum and unlike other big cam engines I've had it doesn't smooth out much as the revs go up. It doesn't really want to rev up like it should and driving at a steady 60 mph it still seems rough. When I shut it off hot the only way it will restart is with your foot to the floor as if it's flooded. I have done the following:

• Cleaned & gapped plugs, they were a little sooty but all looked the same.
• Set initial timing at 12.5 degrees.
• Disconnected and plugged vacuum advance, this improved driveability the most.
• Verified choke was opening fully and adjusted idle mixture.
• Adjusted throttle linkage for wide open floored.

Except for disconnecting the vacuum advance none of this changed anything. Aftermarket A/C was added to the car and works great but if you turn it on it degrades the engine performance even more. I had a stock 440 GTX years ago and it was a very satisfying torque monster on the street or the highway, that is what I want this car to be. I'd appreciate your thoughts on ways to improve this problem, I would really rather not get into the engine unless I have to. Thanks in advance for your help.

 

[SlinktRR]

(Warning - long post)
I've had my GTX for about 8 months now, its a 440 with 4-speed and 3.54 Dana. It had a stock spec restoration back in 2001 and has been well kept since then. I love the look, ride and handling of the car but I'm not happy with the way the engine runs. Somewhere between 2001 and now the engine was modified as follows:

• Very lumpy cam, no idea of the specs.
• Mopar Performance "Wedge" intake manifold
• Edelbrock 1411 750 cfm carburetor
• Electronic ignition distributor, Pertronix coil, no ignition module.
• Aluminum radiator.

Everything else appears to be stock although it is so loud I think the mufflers may just be stock appearing shells. It starts OK and sounds very wicked with that "fairground" idle but the performance just isn't there. It only pulls about 12 inches of vacuum and unlike other big cam engines I've had it doesn't smooth out much as the revs go up. It doesn't really want to rev up like it should and driving at a steady 60 mph it still seems rough. When I shut it off hot the only way it will restart is with your foot to the floor as if it's flooded. I have done the following:

• Cleaned & gapped plugs, they were a little sooty but all looked the same.
• Set initial timing at 12.5 degrees.
• Disconnected and plugged vacuum advance, this improved driveability the most.
• Verified choke was opening fully and adjusted idle mixture.
• Adjusted throttle linkage for wide open floored.

Except for disconnecting the vacuum advance none of this changed anything. Aftermarket A/C was added to the car and works great but if you turn it on it degrades the engine performance even more. I had a stock 440 GTX years ago and it was a very satisfying torque monster on the street or the highway, that is what I want this car to be. I'd appreciate your thoughts on ways to improve this problem, I would really rather not get into the engine unless I have to. Thanks in advance for your help.

Do a search for edelbrock tuning on this board. I would advance the initial timing to like 18-20 and set idle mixture for max vacuum. Recurve distributor advance (shorten) if total is too high. Go for a leaner setting on metering rods. 12" is really good actually, mine maxes out at 9" and I run an 800 edelbrock. The hard hot restart is a common problem with these carbs, you can try leaning the mixture, using the edelbrock insulating gasket, other things to reduce gas percolation and flooding.

 

[miller]

Two big minuses I see are...if YOU didn't build the motor, you have no idea what you have, or how it was built. Other thing is not knowing what cam your dealing with. You say the motor runs so-so. Okay, least it's still in one piece.

Going by the way you say it runs, if it was mine, I'd at least do some basic checking on the cam setup. You need to know if it's right, or not. That just involves pulling the valve covers, and verify the crank/cam timing using a degree wheel, and noting the intake valve open/close points. While doing that, you can also get an idea on the lift you have.

If the cam wasn't degreed right, yeah, it will run like crap.

 

[747mopar]

Like mentioned the biggest problem is not knowing what you have. Assuming the motor is good to go I think #1 you need to sort out the timing (12 degrees initial makes for doggy acceleration). I've got mine set at 20 initial with vacuum advance pulling 10 more degrees in for 30 once the motor fires with the vacuum advance hooked to manifold vacuum (not the timed carb port). Next check to see where your total advance is with vacuum advance unhooked, mine is around 34. Aftermarket distributors come with a generic one size fits all advance curve and if you don't take the time to recurve it your fighting an uphill battle. Don @ FBO (4 seconds flat) is a real great guy and can be very helpful.

There's guys here more suited to help you with the Edelbrock carb but my experience has been "pitch it". I've had them and had the exact same issue as you described but insulating fuel lines and keeping them away from high heat areas will help along with a phenolic spacer to isolate the carb from the intake. Eddy's are more prone to heat related issues simply because the float bowl sits right on the intake with no real separation where all of your Holley based carbs have a base plate gasket, metering block gasket and a float bowl gasket creating blocks for the heat transfer. The other big issue is adjustability, when you start getting into big cams it's common to adjust the air bleeds to tailor the timing in which different circuits of the carb come in. A good example is a rich idle that can't be adjusted out with the mixture screws because the next circuit in the carb is already pulled in.

Patience, research and persistence is what you'll need a lot of haha. Good luck

 

[miller]

Might just need a shot of Jack!

Any idea on the compression values?

 

[Dennis H]

Caveat Emptor may be in order here. More pics? Where was the car purchased. As said, hot restart is characteristic and made worse with ethanol.

 

[TxDon]

Thanks for the response. To clarify, the engine appears to be mechanically sound, all cylinders firing, no smoke, no knocking or pinging, etc. It just seems lazy. Part of this might be my perception, I haven't owned or driven a big cammed car in over 30 years, but I still think it needs improvement. You are exactly right about not knowing the motor's history but no way around that. The comments about initial timing are interesting and easy to try. I just have the stock balancer so I'll need to get some degree tape to check total advance. I will also do a compression check when the weather gets a bit warmer.

I did search and read quite a few posts about tuning issues. Also some on the Edelbrock carbs and their problems. This kind of surprised me since I've had a number of cars with AFB's and had no issues although they were all in stock tune. I know the whole ethanol fuel thing is part of it but are there other differences between the AFB and Edelbrock that cause trouble?

 

[Jeremiah]

It sounds like somebody stuck a cam in the poor thing and didn't degree it. I have seem this way to many times on restored cars.

If it was me I'd put a dial indicator on a valve spring retainer and figure out what the net lift is. That might give you some insight to how big te cam truly is. Even the tried and true mopar .509 cam sounded nasty for .500ish retainer lift thanks to 76 degrees of overlap.

I'd also move into an 800cfm Edelbrock carb to get rid of the 750. It is well known that the internal passages of the 750 are not large enough and that can make it very challenging to get the tune up correct. From your description, if the spark plugs don't look brand new (i.e. lean condition) I'd start checking cranking compression, etc. to support the cam timing theory.

For the hot restart (VERY annoying) condition I'd use an Edelbrock wood-composite 1/2" spacer. That really helped my hot restart issues. Putting a few gallons of 110 leaded race gas in at every fill up helped tremendously.

 

[AR67GTX]

Thanks for the response. To clarify, the engine appears to be mechanically sound, all cylinders firing, no smoke, no knocking or pinging, etc. It just seems lazy. Part of this might be my perception, I haven't owned or driven a big cammed car in over 30 years, but I still think it needs improvement. You are exactly right about not knowing the motor's history but no way around that. The comments about initial timing are interesting and easy to try. I just have the stock balancer so I'll need to get some degree tape to check total advance. I will also do a compression check when the weather gets a bit warmer.

I did search and read quite a few posts about tuning issues. Also some on the Edelbrock carbs and their problems. This kind of surprised me since I've had a number of cars with AFB's and had no issues although they were all in stock tune. I know the whole ethanol fuel thing is part of it but are there other differences between the AFB and Edelbrock that cause trouble?

I ran into one issue with my 800 cfm Edelbrock carb that wouldn't have been an issue with an AFB. The AFB has a port into the bottom of the accelerator pump well that is missing on the AVS style Edelbrock carb (#1412 I think). The Edelbrock carb just has a v-notch in the top of the accelerator pump well to fill it from the float chamber. Unless you carefully set the height of the accelerator plunger so that the rubber cup is slightly above the bottom of the notch - the accelerator pump well will not fill and there won't be a good shot of fuel when the throttle is opened and a bog will occur. I don't know if Edelbrock AFB models share this same construction. IMO - the original Carter design is far superior.

BUT - I don't read anything in your description to suggest that is an issue. The fact that the engine seems a bit rough when running well above idle sounds to me like you have a cylinder that isn't firing - possibly you have a bad or intermittently bad plug wire. It's also strange that disconnecting the vacuum advance seemed to help it - that is just the reverse of what I would expect. Vacuum advance (not ported vacuum) should help calm the idle a bit and also low speed driveability. It also helps the motor run cooler.

747Mopar may have a point. My GTX had a NAPA rebuilt distributor that I couldn't run more than 10 degrees initial timing without exceeding about 38 degrees initial and mech advance total. Like any rebuilder I think they just dump all the parts in a box with a bunch of other distributor parts and there's no tell what you will end up with on a rebuilt unitl. I welded up the advance cam slots in the distributor and reconfigured it to where it provides 20 degrees mechanical advance at the crank now - and I run 16 degrees initial advance. That, and fixing my Edelbrock's accelerator pump issue made the motor much more responsive - drives very strong now. My 440 is stock.

If you don't know what that cam is and can't find out - you may want to consider changing it out for something of known quantity in the future.

 

[lewtot184]

big cams and cast iron exhaust manifolds don't mix. big cams need retainer to guide/seal clearance carefully checked. big cams need an aggressive timing curve. what i've found with edelbrocks is outrageous jetting. the 750's and 800's are too fat and the metering rod springs may need to be replaced. internal passages on the edelbrocks are basically all the same. cluster idle air bleeds and idle jets will vary. take the secondary jets out, .107's, and put them in the primaries and put .098" in the secondaries. make sure the pump arm is in the top hole. i also get rid of the big squirters. they don't need anything bigger than a .028". a fuel pressure check is a must along with checking float levels.

 

[miller]

Good points given on the vacuum advance bit. Was it advancing? The right amount, right rate?

Kinda old school, but know if there's no advance, or set wrong, or flat locked in, motor will fall on it's face much over idle.
Might be something to look at.

 

[coloradodave]

747mopar:
"There's guys here more suited to help you with the Edelbrock carb but my experience has been "pitch it"."

My friend, I wonder how many Carter and Edelbrock carburetors have been "pitched" and replaced by a Holley, only to not cure a perceived "problem". The problem that TxDon is having needs to be diagnosed first, before starting to "throw" parts at it. There's a lot of good advice here, particularly having to do with checking initial and total timing and at what RPM the total is in. A timing tape is a good start. Also:
1) Checking that the plug wires are in the correct firing order. CCW- 1-8-4-3-6-5-7-2
2) Checking the resistance and continuity of each wire. Approx. 5K ohms per foot.
3) Cranking compression and a leak down test.
4) Float level and jets/metering rods - Due to sooty plugs. Correct level and jets are critical.

These are some initial things to try and diagnose the problem, along with the good advice given about checking what cam is in the motor and whether or not it was installed correctly. It's not that hard to pull the timing cover and find out what you actually have if none of the other tests pan out... The results you want are in there somewhere...

 

[747mopar]

747mopar:
"There's guys here more suited to help you with the Edelbrock carb but my experience has been "pitch it"."

My friend, I wonder how many Carter and Edelbrock carburetors have been "pitched" and replaced by a Holley, only to not cure a perceived "problem". The problem that TxDon is having needs to be diagnosed first, before starting to "throw" parts at it. There's a lot of good advice here, particularly having to do with checking initial and total timing and at what RPM the total is in. A timing tape is a good start. Also:
1) Checking that the plug wires are in the correct firing order. CCW- 1-8-4-3-6-5-7-2
2) Checking the resistance and continuity of each wire. Approx. 5K ohms per foot.
3) Cranking compression and a leak down test.
4) Float level and jets/metering rods - Due to sooty plugs. Correct level and jets are critical.

These are some initial things to try and diagnose the problem, along with the good advice given about checking what cam is in the motor and whether or not it was installed correctly. It's not that hard to pull the timing cover and find out what you actually have if none of the other tests pan out... The results you want are in there somewhere...

I totally agree, since Miller already pointed out the need to check the cam timing etc I was only adding things to consider provided the motor is GOOD TO GO as mentioned in the thread.

I know plenty of guys like and have good luck with the AFB carbs but nothing I said is false, they are more prone to heat related issues and aren't as easily tuned. I am a bit biased because the one Eddy I bought brand new leaked like a siv and caused me nothing but trouble so that's just my 2 cents... junk! I've ran Demons, Holleys, Motorcrafts and Quadrajets all with no problems so that's just my opinion and nothing more.

 

[lewtot184]

i like my junk. they're just different than holleys. everything has a learning curve.

 

[coloradodave]

Here we go, Lew. A love fest for the Carter/Edelbrock carbs: BTW, 747mopar, I respect your opinions. I ran Holleys on all my drag cars and love them as well:

 

[miller]

Well, TxDon...got some mighty good leads on what to look for!

Turn the heat up, and jump in with both feet. Main thing is to get the basic 'must haves' out of the way, and figure out what you have, then you can go from there. Could be something somewhat simple that jumps up, that tells the story.

Feel for ya! Still say a shot of Jack can't hurt.

 

[747mopar]

Well, TxDon...got some mighty good leads on what to look for!

Turn the heat up, and jump in with both feet. Main thing is to get the basic 'must haves' out of the way, and figure out what you have, then you can go from there. Could be something somewhat simple that jumps up, that tells the story.

Feel for ya! Still say a shot of Jack can't hurt.

Kraken works well too!

 

[lewtot184]

Here we go, Lew. A love fest for the Carter/Edelbrock carbs: BTW, 747mopar, I respect your opinions. I ran Holleys on all my drag cars and love them as well:

the only problem i can see with that crossram car is that it's not in my garage!....lol.

 

[TxDon]

Well, TxDon...got some mighty good leads on what to look for!

Turn the heat up, and jump in with both feet. Main thing is to get the basic 'must haves' out of the way, and figure out what you have, then you can go from there. Could be something somewhat simple that jumps up, that tells the story.

Feel for ya! Still say a shot of Jack can't hurt.

I agree, I need to get serious about this. As for the Jack that's already covered...

 

[TxDon]

Lots of possibilities to chew on here. I drove the car yesterday, it is NOT happy starting in cold weather, seems like heavy missing until it warms up and I need to keep the revs over 1000 or it loads up bad, maybe the choke is still set too rich. Once it warms up it seems to be running on all eight and feels ok with light acceleration. There is a roughness on heavy acceleration, not missing but like half missing. I ran it up to 60-65 mph, same feeling there and felt some missing punching it from that point, also some pinging.

My first steps will be a compression test and timing check. The comments about plugs and plug wires are good, the "half missing" feeling might be explained there with high resistance or cross leakage. I have Champion RJ12YC plugs in there now but will replace them after the compression test, is there a better choice? The plug wires are 1967 date coded Mopar which I assume to be from the stock 2001 restoration. I will check resistance but if I replace them what is a good choice that will fit in the stock wire looms?

As far as the timing checking and setup in the distributor that is something I have never gotten into, does it need to be done on a distributor machine or can I do it myself? Unfortunately this will probably take awhile, whoever did the A/C addition located the heater hoses so they look good but they totally block the distributor and I can't even get the cap off. I plan to fix this with longer hoses combined with a coolant flush and replacement and that job will definitely need a warm day!