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Discussion Starter #1
Hello everyone- This is my first posting, but I’ve spent the last two years pouring over this site while rebuilding a 1968 Thunderbird. I got this car with the engine pulled and disassembled for my youngest son and I to rebuild. We live in Seattle but got real lucky to find this car on the other side of the mountains in eastern Washington, where it is very dry. The body is almost perfect and has been sitting for 20 or 30 years.

We found an incredible local machine shop and they they did all of the machining that I could not do. I’ve worked on my cars over the years, but never a full engine rebuild.

We carefully assembled the engine and got lots of info from the machine shop and this forum over the last two years.

Here is what we got: 429 engine with mostly a stock rebuild. Very mild cam, new Holley 750 carb, Pertronix III electronic ignition with matching coil, and everything else is stock.

The problem is: we can’t get it to run “good.” I can’t get it to idle less than 1000 RPM. I cleaned up the distributor really good. It was real dirty and the mechanical advance was stuck. It took lots of cleaning, and now it feels good as new. I got 12V going to the new coil too. It starts up OK, but needs lots of advance timing to keep running, and I need to set the idle on the carb to 1000 to keep it running. I can see the vacuum advance working and the mechanical advance working. The initial timing seems to be best at 14 degrees BTDC, but I must keep the vacuum going to the distributor otherwise it dies. The mechanical timing was set with the 13L slot. It seems to be running pretty rich (black spark plugs). I’ve got fresh 92 premium gas too. Could it be the carb needs to be leaned up a bit? Could that cause this issue? I’ve tried adjusting the timing for hours with no luck. Any help would be very much appreciated.
 

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Sounds like it might be a vacuum leak.Disconnect everything that requires vacuum...brake booster,trans modulator,etc. Check around the carb base for leaks. A massive vacuum loss will activate the power valve in the carb which might be creating your rich condition.
 

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Discussion Starter #3 (Edited)
Thanks for the good suggestion. I have seen enough of issues caused by vacuum leaks that I should of looked at that first. I will investigate tonight and get back with the results. Thanks, Tony
 

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Disconnect all the vacuum hoses expect the one going to the dist and plug them. Older cars like this have many vacuum hoses and you only need one to leak. Cracked at the connection or a bend cracked. Make sure at the vacuum ports on the carb are plugged as also the ones on the intake manifold and start from there.
 

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Discussion Starter #5
Thermod and Dacofa thanks for the great and fast help. This forum is really awesome. Sure enough, you guys are right on target. I’ve probably read 50 responses on this site that said to check for vacuum leaks first, but I was stuck on “fixing” the timing for the last week and trying to figure out why the carb is running so rich.

I only had a few minutes tonight to play around before getting back to the family. I only replaced a couple vacuum lines during our rebuild, and sure enough, the brake vacuum line looks cracked at one end. I plugged all of the vacuum lines and looked over the vacuum diagram.

The vacuum diagram has me taking the distributor port on the carb to the three-way connector on the top of my coolant thermostat housing, and then to the distributor. Is that normal?

Now the engine is behaving completely differently, which I bet is good. I will reset the initial timing and play around with it more this weekend.

Thanks again for your help... I’m sure I’m on the right track now.

Thanks, Tony
 

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Discussion Starter #6
92046


This is how the vacuum diagram for the car shows to hookup the vacuum advance to the distributor. The red circles show the line from the carb to the three-way connector on the thermostat housing. The red line with the arrow is the line that wraps around to the distributor.

Does this look right? Should I just connect the carb to the distributor and bypass this three-way connector?

Thanks, Tony
 

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Discussion Starter #8
Wow, I mean really WOW... that is one nice looking engine. I’ve got two miles on mine, and it is not that clean. You obviously take great pride in your work.

My distributor only has one port for advance. I did need to replace the vacuum advance canister, because the original leaked.

92053


Should I connect the distributor directly to the carb or route it through the three way connector on top of my thermostat housing (as shown in my vacuum diagram below)? I think this routing would only provide vacuum after the engine is warmed up, but I’m not sure.

I have the vacuum line for the distributor routed as shown below:
92055
 

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Get rid of the vacuum switch and hook the vacuum advance dashpot directly to ported vacuum on the metering block passenger side.


SJ
used 2b RHP


.
 

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Discussion Starter #10
You guys are awesome. Thanks again for the help. I really appreciate the specific details, because it has been 30 to 35 years since I last rebuilt parts of engines. Your patience is amazing, especially on stuff that is very basic for you guys.

I think I plugged all of the potential vacuum leaks last night, and that really changed how the engine ran for the better. I bet this change will help too.

I plan to get the initial timing reset and adjust the idle if needed. Before these changes it would not run with anything less than 12 degrees BTDC at 800 to 900 RPM. The book says 6 degrees BTDC for the initial timing and 550 curb idle, does that sound right?

Thanks, Tony
 

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You guys are awesome. Thanks again for the help. I really appreciate the specific details, because it has been 30 to 35 years since I last rebuilt parts of engines. Your patience is amazing, especially on stuff that is very basic for you guys.

I think I plugged all of the potential vacuum leaks last night, and that really changed how the engine ran for the better. I bet this change will help too.

I plan to get the initial timing reset and adjust the idle if needed. Before these changes it would not run with anything less than 12 degrees BTDC at 800 to 900 RPM. The book says 6 degrees BTDC for the initial timing and 550 curb idle, does that sound right?

Thanks, Tony
At one time many moons ago, I had one like it. Just some pics from the Torino Cobra website.
 

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Discussion Starter #12
I definitely had a few small vacuum leaks that I’ve plugged for now.

I hooked up my vacuum gauge, and the carb port that is now directly connected to the vacuum advance on the distributor has 10 in Hg at idle (still around 800 rpm) and gets 23 at 3,000 rpm. I also check the manifold vacuum that goes to the brakes, and it was not steady at idle: between 12 to 15, and 24 at 3,000 rpm. The timing needs to be at 20 degrees BTDC to idle smoothly (that is with the vacuum hooked up).

With the recent vacuum “fixes” that you helped me look for, the engine sounds better. It will not idle below 800 rpm, and still dies when I put it in gear.

I’m pretty sure there are no more leaks from the carb ports and from the intake manifold. One of the bolts on the carb is hard to get to, and was not very tight. I tightened it more. How can I check for a leak between the carb and intake manifold? Soapy water, WD40, carb cleaner. Do these work, are they safe?

One more interesting thing: the smell. This is the biggest engine I’ve ever worked on, but the smell just does not seem right. After working on the engine my shirt smells strongly like fuel, but not exactly... maybe more like exhaust (whatever that smells like??). In fact, I can’t keep my face over the engine for more than a few seconds without starting to almost cry (like cutting onions), and I always wear good covering eye protection. Is this normal?

Sorry for my posts being all over the map. Here are my next set of questions:

  1. Does it sound like I’ve got more vacuum leaks?
  2. How can I check for a leak between the intake manifold and the carb throttle body?
  3. What about the gas/exhaust smell over the top of the engine that makes me cry like cutting onions, is that normal or am I running way to rich or something else?
 

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That sounds really rich. What do your plugs look like? What heat range are you running? When it's running look down in the throat with a flashlight and see if any fuel is dripping it? Float levels?
 

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Discussion Starter #14
The plugs are black after just a couple minutes and smell like fuel. I’ve got new Autolite 45 plugs. I think that makes them medium heat range, but I’m not 100% sure.

It is a new Holley 4160, and the directions say it is already adjusted... so I have not touched the fuel/air mixture yet.

I will check the float levels and look for dripping fuel with the flash light tomorrow.

Is it possible to have the carb running rich and that causes the rough idle below 800 RPM and for the engine to die when placed in gear?
 

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Oh yeah, especially with your plugs fowled out like they are. 45 is the standard plug, 55 would be one range hotter. But work on the carb for now. Factory settings are ify at best on anything. Whatever you do, don't use any ones other then Autolite or Motorcraft plugs. Never had goodluck with Champions or even ACCEL.
 

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Discussion Starter #16
Thanks again Dacofa. Thanks for tips on the plugs.

The engine does smell better now. The screws for air/fuel mixture were turned way out from the factory. I screwed them in all the way and backed them out about two full turns to get good vacuum. Now my eyes don’t water while working on top of the engine.

The timing stills needs to be way advanced, like 20 to 25 degrees to run good at 900 RPM.

Your comments on the plugs got me thinking about my gaps. I double-checked and they were all at 0.032 where I set them (low stock). I think the idle issue got worse after upgrading to the Pertronix III ignition with the flame thrower coil. I was thinking about increasing the gap with the 4x voltage from the new coil. Sure enough an extra 0.01” made a big difference on the engine. I was able to get the car in gear at 900 RPM and it wanted to die, but actually continued to run for the first time. 900 rpm is too high for this automatic transmission and it needs to be closer to 600, but it does when it is less than 900.

Answers to your other questions: Yes I see fuel flowing down the side of the throat with a flashlight when I rev it up, at idle there is no visible flow. The primary float was a bit low and the secondary was really low. I fixed both.

New questions:

  1. Leaner idle air/fuel ratio and bigger spark plug gaps... could that be the right combo to fix the idle?
  2. Should I try 0.015” extra gap @ 0.047” (stock range is 0.032” to 0.042”) to see if I can get the advance under control? Right now they are at 0.042” and it is idling better with less advance.
 

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Hot electronic ignitions seem to work best between .042-.055 depending on how hot it is. Hotter the wider. Most idle screws I've done are in all the way and out 1-1 1/2 turns. Fowled plugs are probably still hurting you. See if you can find a set of 55 or a new set of 45s. Hotter plugs for running around town, colder for freeway long drives. Make sure the choke is opening up all the way. Don't take much to mess it up. I high float level will also bleed fuel into the carb, even at idle. What type of Fuel pump are you running? Some put out enough pressure to lift the float off the seat and cause a floating issue.
Which part of Seattle do you live in?
 

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Discussion Starter #18
Thank you for the tips on the gaps and idle screws, I was not sure about going bigger on the gaps and I will try it a bit leaner too. I will test it out and let you know the results in a couple days. I’ve been cleaning the plugs every couple of days, but you are probably right, and I will get some new 55s.

The choke is definitely all the way open. I’m using the stock mechanical fuel pump. It seems to be working ok, and has a steady 5 psi.

We live on the east side of the lake between East Renton and Issaquah.
 

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Oh crowded down there now. You're in the area the Green River Killer used for 20 years. They ever open the Horse race track up again?
 

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Discussion Starter #20 (Edited)
Yep, very crowded here. Not sure about the horse racing, but there is a greyhound track a bit farther east of Seattle now.

Interesting fact: The green river killer work at my company 20 years ago, and people say he was completely normal at work.

Can’t wait to try bigger gaps this evening and see if we can get it running good at idle and stopped in gear.

I could not find any Autolite 55 or Motorcraft AG42 at my local O’Reilly’s, Napa, or Autozone. I can’t find them on Amazon either. I have not checked Summit or Rock yet. Any idea where to get them, hopefully locally? I can find Autolite 65, would that be OK for around town?
 
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