Air fuel mixture question

[bobioknight]

Chris you called it. I am experiencing those exact symptoms. I installed the autolights 45 plugs. So I am now wondering if colder plugs cause the same symptoms, or if not, maybe I need to close up the gaps a bit.

[CSavaglio]

Try closing the gap to 40.....its free to try first.

Why would you run colder plugs? Your setup is pretty stock..... Too cold a plug will cause issues.....mostly plug foulig over time and all the issues associated with that. But I would try regapping for now and see if they foul in the nedt few hundred miles.

[bobioknight]

Well I get my quick parts from orielys auto parts. The autolight 45 and 46 was what they had available and was listed for my year engine. I opted for the 46 because I don't know what the hell I am doing... I went in wanting the champion plugs but they would have had to special order them and I needed to run to a car show so I installed them.

This is the chart I followed, the 45 is listed at hot and the 46 is listed as too hot. Take a look and please make a suggestion.

http://ford-y-block.com/tuneup.htm

In this list I see the 46's and the champion 11 RF18YC. The 46's have a heat range of a 3 and the 11's have a heat range of 18. "Thinking An 18 will surely burn a hole in my piston"

https://www.sparkplugs.com/Automotive-c134.aspx

When I look at a cross reference of the original champion 870 plugs I don't see the 45's or the 46's on the list.

Replacement spark plugs for Champion 870:
Brand Model
Autolite. 2954
Autolite. XST2954
Champion. RF18YC
Champion stk. 870
Denso. 5008

Funny how difficult buying the correct spark plug can be. This should have been so simple. I love the chart that states buying too hot of a plug will burn a hole in your piston, "thinking oh shoot I better buy a colder plug, don't want a hole in my piston, for sure"

[bobioknight]

Try closing the gap to 40.....its free to try first.

Why would you run colder plugs? Your setup is pretty stock..... Too cold a plug will cause issues.....mostly plug foulig over time and all the issues associated with that. But I would try regapping for now and see if they foul in the nedt few hundred miles.

Thanks, but the spark plugs are cheap, I would rather just install what is correct if you have a suggestion I would appreciate it. If you read my earlier comment you will see specs are kinda all over the place with heat ratings, not sure which plug to choose for my stock engine setup. And it's Saturday, it will give me a reason to go wrenching on the old girl.

[CSavaglio]

I misspoke...I was thinking the 46 was the colder plug...need to get off night shifts....

45 is a good all around plug...I run them in mine and it's a mild performance build...they are considered the stock replacement plug. I've run the inexpensive Autolites in my older cars for a long time and never had any issues. I don't worry about lifespan because they're cheap...under 20 bucks for a set.... and typically older cars don't get driven all that much.....who needs 100k mile plugs on cars that are driven a few thousand miles a year? Platinum plugs foul too easy in carb'ed cars and don't take cleanings very well...they seem to foul very quickly once it's happened once.

You're probably ok on the 46's for now, although I would check them periodically and look for indications that they got too hot....the white ceramic will get scorched or blistered and you'll see heat discoloration on the electrode...every standard plug reading diagram shows what it looks like. If you spend a lot of time going from car show to car show on the highway, they might get too hot.

The plug heat ranges are really getting into the fine tweaking....most run what's listed as a stock plug (45's in our case) and never think about it. Higher compression, performance setups need a colder plug because cylinder temps are higher..the opposite for very lightly driven stock cars....cold plugs foul because they don't get hot enough to burn off the deposits.

Just keep an eye on them...if they look wrong when you pull them, you can go to any auto store and get a set of 45's and swap them...at least it's easy and quick on these cars.

C

[CSavaglio]

If you're itching to throw just a little more money at it, get a set of the 45s, gap them at .040 and you're set.

C

[bobioknight]

If you're itching to throw just a little more money at it, get a set of the 45s, gap them at .040 and you're set.

C

Thanks for the confirmation Chris. OK, I will leave the 45's, gap them to .040 and see what happens.

Last thought, idle speeds, one book says 550rpm, another book says 475-500rpm, when I idle at the lower rpm's, The engine seems to slightly bounce around looking rough, when closer to 550 or 600rpm the engine is nearly perfectly still and smooth.

Does running a lower idle where the engine looks rough hurt anything like motor mounts, etc. excelleration from the lower idle rpms from a stop sign sometimes feel a bit studdery, but not all the time.

When you set your timing, what rpm's do you idle at when making the adjustment, I assume your timing changes when idling at 500 or 600rpm.is this normal?

[CSavaglio]

A healthy Y-block with a stock cam should idle happily and smooth at 450 rpm. Mine will actually idle below 400 smoothly. The factory T-bird manual shows (for automatics) 445-455 in neutral and 425-450 in drive (E-brake set and wheels blocked!!!! Or have a helper hold the brake!!).

Idling higher will cause some shock on the drive train when you put it in gear, although, at 550, I doubt you'd notice it. Timing prob won't change if you're idling a little high depending on how the distributor is curved, but it's easy enough to double check. Disconnect and plug the vac advance pot when you check.

I'm a bit confused.. you wrote that you had opted for 46 plugs ......45 is certainly not too cold and sit in the middle of the heat range, like the original Champion 870....it's the stock heat rating. You cant cross each manufacturer's heat range index number between....they all use different scales.

If it doesn't idle smooth, there's an issue....tuning, ignition miss, valve adjustment, internal engine issue or several minor compounding issues.

What kind of vacuum are you seeing at idle? Is it steady?

Did you already put new wires and cap/rotor in? Is the firing order correctly? Are all the plug wires snapped on....you should feel them click on. Fords are numbered differently than most.... It shows it on the Y-block tune up page you linked.

[bobioknight]

A 450 smooth idle would be sweet, I will be shooting for that.

I do unplug the vacuum hose to the carb and plug the carb when checking timing, I thought and expected that if it was idling at 450 or 600 the timing mark at let's say 10 should stay 10, but The timing mark does move around as I increase or decrease idle. Not sure if this is normal?

sorry if I made that confusing, I am running the 45, the auto parts store offered the 45 and 46, I went with the slightly colder plug. Thanks for explaining the heat range differ between manufacturers. Going from a 2 to an 18 is a huge difference.

At idle I can adjust timing to get 21 on the guage, there is a slight vibration on the needle, it's about a 1inch or less bounch on the scale. All the plugs look very similar, I will be adjusting the valves and do a compression check, oil and coolant looks new and clean.

I changed rotor and cap and plugs, but I did not change wires, kinda doing one thing at a time. I will change he wires and verify the wires are in the correct position, do you have a wires suggestion that works best with the new coil?

[CSavaglio]

Depending on how your distributor is set up (with the springs/weights internally that determine the mechanical advance), you may or may not see a change of timing at idle, so I'm sure that's fine.

I don't want to alarm you, but that's not a good vacuum reading.... 21 is fine, but the needle bouncing is an indication of trouble. It should be very steady, no vibration. There are plenty of charts on the web showing how to T/S with a vacuum gauge...just like the plug reading charts.

It can be an indication of a misfire, valve trouble, etc. Adjusting timing is only changing the vacuum reading because you're changing the speed of the motor. You should be using the vacuum gauge to adjust the idle mixture screws. With all the messing around with the carb, these need to be set again. If you have no idea of the condition of the plug wires....they can look fine, but be bad internally and cause a misfire, so I would a set. No point in doing a big ignition tune up and leaving plug wires from who knows when...... a bad wire could be causing both the rough idle and vacuum issue.

The order you should go in, now that the rest of the carb is set reasonably well is this:

Change out the plug wires.

Get the car warmed up and adjust the valves. Do not use a feeler gauge unless you know your rockers have no wear. This is a very good tutorial on it..... http://www.y-blocksforever.com/tech/html/valvelash.html and it's the method I use, and have used since my first Y-block.

Adjust the hot idle
Adjust the timing at idle
Re-adjust the idle (more timing will make the engine run faster and vice versa).
Adjust the idle mixture screws...shoot for the highest vacuum reading. Adjust the screws about 1/8 turn at a time and adjust the sides evenly.
Adjust the idle again. The idle mixture screws can affect the idle speed.
Check the vacuum gauge. A very lean or rich idle can make it fluctuate too....that's why I suggest getting the idle mixture set. It can also cause the idle to be iffy.

Doing all that is free (except the plug wires)

If the vacuum still isn't reading right, a compression leak down test is in order to check for a burnt or leaking valve. This is different than a compression test. A compression test tells you how much pressure is built while cranking. A leak down test pumps air in and tells you if it's leaking out (past the rings, valves, or head gasket). You need a special leakdown tester (not super expensive) and a decent compressor.

I don't have a specific recommendation on the wires. I use a generic performance V8 set and build my own so I can make the lengths how I want them. If you go with the 7mm, they will fit in the factory looms. The 8mm can fit, but will take a bit of work. Go for a set that lists as spiral core, heli-core, or RFI suppression. The local parts store will probably not have a set specifically for your car. Universal sets won't fit well...you'll have a few too short and handful way too long. If you've never built a set of wires, I would suggest ordering something from a T-bird supplier that's sized for the car.

[bobioknight]

Ok Not alarming at all, I have been concerned about it and have researched it via vacuum charts, either carb or valves, the engine was rebuilt a little while back so I am hoping it's just an adjustment... We will see. Thanks Chris, I will get this done and report back.

[CSavaglio]

Double post

[CSavaglio]

Do you know who rebuilt the motor and what parts were used? I assume it was done before you got the car.

I always worry about it when someone rebuilds a motor and sells the car right away....I had a 72 vette like that....never ran right....finally tore it down and it was rebuilt, but done horribly.....one cam lobe was badly worn from it not being broken in right, among several other issues. The vacuum gauge acted like you describe.

I actually bring a vacuum gauge with me when I look at cars. If there's any issue, I pass unless I was planning on a rebuilt right away.

Don't get too worried about it yet. Hopefully its something simple. BTW, if its a valve adjustment causing it, it'd have to be very badly adjusted, like to the point a valve isn't opening or is so tight it isn't closing.

[CSavaglio]

When you do the valve adjustment, it'd be a good idea to check to see if any pushrods are bent.

[bobioknight]

Bummer about the vet, smart about the vacuume, you can tell a lot about an engine pretty quickly. Yes I do have all the receipts, including the ones from the rebuild, but they aren't that detailed. I will run through the steps you provided and see what happens, I do have a y block valve adjustment tool and will test valves both ways. I do appreciate the help and guidance.

Looking forward to testing both ways to see if this little gaget worked, I was planning on using a feeler guage but now I am glad you mentioned the wear on the lifter and having a bad reading. It totally makes sense and I am glad I asked.
https://www.ctci.org/gilsgarage/ValveGa ... ctions.php