Thermoquad 1966 Metering Rods

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My thermoquad had .101 primary jets. Would .104 jets make much more difference? Just wondering.
 
Yes, it will be richer at cruise & WOT. What are you trying to do?
 
Well carb in car now has 98 jets. Sometimes pings/detonates when I mash the go pedal. Previous carb had .101 jets so it would not ping. A co worker told me the richer jets helped. Engine is a 360 with 340 X-heads, a 292 mopar cam with kb-107 pistons. Intake is a Victor 340. 3.91's out back. Also 727 trans with a 9.5" FTI 3400-3600 stall converter.
 
That combo [ the Victor ] would probably want richer jetting. Try running it without the met rods, which will richen it up.......or put the old carb back on.
 
That combo [ the Victor ] would probably want richer jetting. Try running it without the met rods, which will richen it up.......or put the old carb back on.
No metering rods?! Can motor run good without rods at all?
 
Yes, you will be fine. Just cruise at light throttle [ you are on the idle cct still ] to your test area & then mash the throttle.
I have a feeling it will still ping because it is not a mixture issue.
 
Well that’s the craziest thing I’ve heard of in a while.

If you’re going to run without metering rods, you’re going to have to find a jet small enough to do this. It’s all in the math.

98 jet with a let’s just go with a 67/52/45 rod (That’s the 1966 rod) .098 - .067 = .031 total area of the circumference of the interference of the rod inside the jet.

Now you need a jet @ .031.

Now let’s look at the medium size of the rod. Which is used in a part acceleration on a small dip in engine vacuum.
.098 - .052 = .046
And then again at WOT
.098 - .045 = .053

This is how metering rods work, by metering the fuel going in under certain conditions. One size does not fit all. If you’re going to drag race this only, you’re going g to need to find out what size jet will work under WOT conditions only and never care about how stupidly eye burning rich it is at idle. Driving around will be super limited due to extremely quick plug fouling. By stock in what ever plug company your using.

PS, you’ll never find a jet that small unless you have it done custom.
 
Well carb in car now has 98 jets. Sometimes pings/detonates when I mash the go pedal. Previous carb had .101 jets so it would not ping. A co worker told me the richer jets helped. Engine is a 360 with 340 X-heads, a 292 mopar cam with kb-107 pistons. Intake is a Victor 340. 3.91's out back. Also 727 trans with a 9.5" FTI 3400-3600 stall converter.
Try better and/or more octane fuel, the , go to your timing.
Since it ran better with .101 jets and the problems started when you installed .098 jets, seems like you solved your own problem here.

If you were a little rich to begin with, the easier move was with a rod change to begin with. After you check various sources of metering rods to see what the next thicker rod is, if it is not available, then ether have it made, check for the next jet size that will give you the area of jet being searched for or have the jet and rod custom made.

IIRC, it’s ether the carbshop or carbs unlimited will make you what you’re searching for. It is pricey having a rod and/or jet made.

What is your rod and jet combo now?
Did you change the step up spring in the carb?
What is your vacuum reading?
What’s the distributors timing curve?
 
In addition….

I hope you see the insanity of running without a metering rod.

A full .098 jet vs a .098 jet and the metering rod restricting fuel down to a comparable size jet only use of .031.

.031 jet vs a .098 jet…. Hummmmm
.031 X’s 3 = .093. Yeaaaaa. Ummmmm, OK now!
At a tripled rate, the suggested size to run.
Triple the size of what was there to start with, yea, OK, sure!
LMAO
Yes! Removing the rod for triple the fuel!
That’s always the solution!

NOT!
 
Rumble fish.
Post #8. Not crazy at all for the purpose of testing to see if a richer mixture improves/stops pinging. I have done it, many times. Just because you have not done it does not mean it doesn't work. Your post 9 & 11 are just nonsense. There is no such thing as the 'total area of the circumference'.
If you bothered to fully read what I said, it was to cruise at light throttle [ on the idle cct, not the cruise step of the met rod so as to avoid plug fouling ] to the test location.
Apparently you are unaware that when comparing fuel flow through a jet you use area, not diameter. A 045 met rod tip in a 098 jet gives an area of 0.005953 sq in. With no met rod, 098 jet only, the area is 0.007543. The increase in area by removing the 045 met rod tip is only 16%, not the nonsense you came up with.
 
Sorry, the bottom line figure above of 16% is incorrect, should be 27%.
 
So as per my post #8, less than a 1/3 increase in fuel area, not the triple increase nonsense at the end of post #11.
 
Actually the thermoquad on my car now is a different carb. This carb has .98 primary jets and 2024 rods. Secondary jets are .137. Prevoius carb had .101 primary jets and 1966 rods. Secondary jets were .147. So carb was more responsive. Reason for change is this carb started to leak fuel. Needs kit. New carb I had already rebuilt on shelf. So probably need to change rods and jets like old carb. I also want to try colder spark plugs. Now have rn12yc going to try rn9yc range like 1969 340 specs.
 
Rumble fish.
Post #8. Not crazy at all for the purpose of testing to see if a richer mixture improves/stops pinging. I have done it, many times. Just because you have not done it does not mean it doesn't work.
Running a full unrestricted jet that normally has a metering rod is n it without reducing the size accordingly is nuts and something I would never do to see if making it richer solves anything.

Your post 9 & 11 are just nonsense. There is no such thing as the 'total area of the circumference'.
Perhaps I worded it poorly.
The jet has an opening of .098, the total open area is reduced by the size of the metering rod. .067. What remains is the area that the fuel flows past. It’s shape is a circle and the area that’s left behind is what I was trying to describe.
If you bothered to fully read what I said, it was to cruise at light throttle [ on the idle cct, not the cruise step of the met rod so as to avoid plug fouling ] to the test location.
Horse ****
Apparently you are unaware that when comparing fuel flow through a jet you use area, not diameter.
This I understand. The area of what is left over when the rod is in the jet is circular.
A 045 met rod tip in a 098 jet gives an area of 0.005953 sq in. With no met rod, 098 jet only, the area is 0.007543. The increase in area by removing the 045 met rod tip is only 16%, not the nonsense you came up with.
Horse ****.

Read it again. I’ll use rounder numbers.

100 jet, 66 rod. 33.3 left over in area.
Remove the rod and you increased the area 66%. Triple of what was there. Simple.
 
Rumble,
You must be eating some of that horse **** & it is affecting your brain....I do not need to read again what you keep getting wrong....
You must have fallen asleep in the maths class at school.....

One last try before I stop wasting time with you.

Your quote: 100 jet, 66 rod. 33.3 left over in area.
Area of 100 jet= 0.007854 sq in; area of 66 rod= 0.003117. Left over is.....0.004737. It is not 33.3 in area, it is 60% of the original area.
 
Quick,
You cannot judge the carb just by jetting alone. The earlier 6000 series carbs that I have seen had smaller primary high speed air bleeds. They are easily seen with m/rod inspection covers removed; they are a brass insert, next to the side wall of the choke tower, near the inspection cover screw hole. Later carbs had larger air bleeds & used the larger 101 pri jet. A side by side comparison is easy to see. Larger air bleeds lean the mixture, so I assume the larger jets were used to compensate for this. Not sure why the change, probably emissions related.

Similarly with the sec air bleeds. I found them to be 0.039" on 6000 series carbs & reduced to 0.029" on many later 9000 series carbs, which used smaller sec jets. At least one model TQ here used a 098 sec jet & a 101 pri jet! Yes hard to believe!

It is not just fuel jet size then that affects mixture....& how the carb performs. The sec nozzle bars on TQs have holes drilled in them, different sizes, numbers & different spacing depending on the engine they fit. This alone could affect performance. Sec t/blade opening, air valve fully open position, air valve dashpot model etc will all have an affect on how the carb performs.
 
Actually the thermoquad on my car now is a different carb. This carb has .98 primary jets and 2024 rods. Secondary jets are .137. Prevoius carb had .101 primary jets and 1966 rods. Secondary jets were .147. So carb was more responsive. Reason for change is this carb started to leak fuel. Needs kit. New carb I had already rebuilt on shelf. So probably need to change rods and jets like old carb. I also want to try colder spark plugs. Now have rn12yc going to try rn9yc range like 1969 340 specs.

Be careful. Champion has NOT said to use that 9 in early 340’s since the early 1990’s. You could be stepping on your pee pee.

There is a reason catalogs get updated.

Let the plug that’s in there tell you what heat range you need and know this for a fact. Those cross reference charts are about junk.

You can take a Champion, an NGK and an Autolite that are supposed to be the same heat range and all three will read differently in the same engine with the same tune up.

So what I’m saying is don’t use an early catalog to pick your plug. Use the latest catalog and then look at the plug and it will tell you if the heat range is correct.

I may at some point post some pictures of the three above mentioned plugs so the difference can be seen.
 
Be careful. Champion has NOT said to use that 9 in early 340’s since the early 1990’s. You could be stepping on your pee pee.

There is a reason catalogs get updated.

Let the plug that’s in there tell you what heat range you need and know this for a fact. Those cross reference charts are about junk.

You can take a Champion, an NGK and an Autolite that are supposed to be the same heat range and all three will read differently in the same engine with the same tune up.

So what I’m saying is don’t use an early catalog to pick your plug. Use the latest catalog and then look at the plug and it will tell you if the heat range is correct.

I may at some point post some pictures of the three above mentioned plugs so the difference can be seen.
Champ calls for 10's in my 273-4. I switched to Autolite and somehow through the wonders of a conversion chart I got a 9 equivalent. I chased a rough rich idle for better than a year. Finally I went back to basics (and figured out that the issue started after the plug change) and changed to a warmer heat range and immediately the problem went away. Yes, let the plugs tell you what the engine wants.
 
^^^^. This. Spark plug conversion charts [ between brands ] are an approximation. For Chry V8s, a '5' in the NGK range is best, in the NGK catalog. If road racing [ continuous WOT ] or using a power adder, then a colder plug such as a 6 or 7 may be reqd.
I am in the process of building a brand X engine that will have aftermarket alum heads. The heads use 3/4" reach spark plugs & are poorly designed; about 3/16" of s/plug thread is exposed in the chamber. The owner has another, running engine, with the same heads & he reports the plugs are tight to remove; because carbon has got into the threads. This engine would normally use a NGK 5, but going to use a 6 due to the very exposed position of the plugs.
 
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