Camshafts and Compression

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Valman said:
Some updates, gotta quick test run in today. Very promising, with a few hiccups..

- 32* timing, 18*initial, using MVA for 28* at idle.
- .100 main jet, 2005 rods, 2 1/4 turns on the idle screws on the TQ.
- Got the dreaded nozzle drip at idle. :( Rich smell at idle. Had to idle it up a bit.
- Bit of a RPM drop pulling into gear, feels like it wants more timing at idle now.
- Nozzle drip maybe from needing more idle timing now, I’ll re-check the carb also.
- Turns over much easier on the starter.

Very snappy throttle response, feels good and smooth when on the main circuit / cruising. Rev’s quick. Haven’t had a vacuum gauge on it yet, might try that tomorrow.
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If it's dripping from the boosters, that sounds like a float/needle and seat issue. OR possibly high fuel pressure.
 
Bewy said:
All sounds a bit odd. If you get nozzle drip, it is uually because idle rpm is too high....increasing idle rpm should make it worse
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Yeah, seems odd. Wasn’t dripping earlier, before doing the work. I can see it coming out of the small brass outlet on the booster.
Otherwise, it’s running sweet. I’ll take the carb off this evening and double check it.
 
RustyRatRod said:
If it's dripping from the boosters, that sounds like a float/needle and seat issue. OR possibly high fuel pressure.
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It’s got 5.5psi at idle, so the pressure should be ok. I’ll definitely check the float height again, give it another clean.
 
Valman said:
It’s got 5.5psi at idle, so the pressure should be ok. I’ll definitely check the float height again, give it another clean.
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I would tend to agree, if that's 100% verified. Maybe double check the float level and closely inspect (magnifying glass) the needles and seats. Look for witness marks completely around each needle. If you see a gap, that could be a leak. I've taken and gently twisted the needles in the seats with needle nosed pliers and a lot of times that will make them seat.
 
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Is the PCV hooked up? If so, put your finger on it, engine idling. If you can feel movement or pulsing, it is not working. It will admit a LOT of air into the engine requiring pri t/blades to be open further to access the t/slots for extra fuel. Blades open too far=nozzle drip.
 
Update of sorts.. I’ve been trying a few things, first I took the carb off and noticed this green, slimy crap oozing out of various places. This is when I sprayed carb cleaner through the passages. Look at the brass acc.pump cap, you can see the green-ish colour on it.

Got it idling better, saw the base gasket was partially blocking the by-pass air passage in front of the throttle blades. No more nozzle drip. Going to try a few different MVA settings, then a comp test after a good test run. Getting closer..

IMG_0108.png
 
Valman said:
Update of sorts.. I’ve been trying a few things, first I took the carb off and noticed this green, slimy crap oozing out of various places. This is when I sprayed carb cleaner through the passages. Look at the brass acc.pump cap, you can see the green-ish colour on it.

Got it idling better, saw the base gasket was partially blocking the by-pass air passage in front of the throttle blades. No more nozzle drip. Going to try a few different MVA settings, then a comp test after a good test run. Getting closer..

View attachment 1716384183
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Have you made any adjustments to the metering rod tree? That fine tunes the mixture at idle and lower rpm.

Find the metering rod tree just behind the choke tower. Now look in the center of the tree just behind the center of the choke tower. Notice a small screw with a slot for a small regular screwdriver. Find a screwdriver that fits well.

Now, GENTLY depress the metering rod tree until it bottoms out and HOLD it there. Next, take your screwdriver and turn the center screw counter clockwise while watching the metering rod tree, ALL THE WHILE holding the tree in the full down position. When you start turning the screw, you should notice the tree going DOWN.

Continue to turn the screw until you see the tree STOP going down. Now, while still holding DOWN on the tree, turn the screw ONE FULL TURN clockwise. This will raise the tree one full turn back UP. This is your base adjustment.

Record that you left with the screw turned one full turn up from bottomed so you will have a reference. From here, you can adjust clockwise to raise the tree for rich (which you will likely need) or counter clockwise to lower the tree for lean. Now you know how to adjust the metering rods. You will have to play around with it and see what effect the adjustment has. I normally use the 2 full turn method for adjustment. So start with two full turns clockwise to raise (richen) the metering rods but only AFTER you've driven it to get a base line. Record each time you make an adjustment. That way, you will know what you did and what effect it had. Just start all over again if you have to. There's really nothin to it.
 
RustyRatRod said:
Have you made any adjustments to the metering rod tree? That fine tunes the mixture at idle and lower rpm.
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Yeah got that adjusted, I do it a similar way but usually start at 1.5 turns up then go down towards 1 turn if you need to lean it out slightly.

The trick is to really feel when the metering rod tree just starts to move up from the bottom, then count your 1-1.5 turns from there. Of course you already know all this! :)

Funny thing is, the carb was clean visually. I think I must’ve got some bad fuel. (Ethanol?) Never seen that green ooze before.
 
Valman said:
Yeah got that adjusted, I do it a similar way but usually start at 1.5 turns up then go down towards 1 turn if you need to lean it out slightly.

The trick is to really feel when the metering rod tree just starts to move up from the bottom, then count your 1-1.5 turns from there. Of course you already know all this! :)

Funny thing is, the carb was clean visually. I think I must’ve got some bad fuel. (Ethanol?) Never seen that green ooze before.
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Screw that half turn chit. My mind is batty enough as it is.
 
The met rod tree has no affect at idle IF the pri blades are properly adjusted for the correct T/slot position. You could remove the met rods & it will have no affect on the idle.
When you have nozzle drip, it means the main [ high speed ] system is operating & the met rod tree under these circumstances WILL have an affect.
 
Bewy said:
The met rod tree has no affect at idle IF the pri blades are properly adjusted for the correct T/slot position. You could remove the met rods & it will have no affect on the idle.
When you have nozzle drip, it means the main [ high speed ] system is operating & the met rod tree under these circumstances WILL have an affect.
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That's not been my experience. At all. But ok.
 
Bewy said:
The met rod tree has no affect at idle IF the pri blades are properly adjusted for the correct T/slot position
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I’ve always worked off the tr/slot not being much more than a small square revealed. Too much tr/slot > activates main circuit > nozzle drip.

This is why some big cammed, performance engines need more by-pass air. Not only to raise the idle, but they can pull enough air through the tr/slot at idle to activate the main circuit, then get nozzle drip.
Anyway, that seems to be ok for now.
 
When you open the blades to expose more t/slot, you are also letting more air get past the blades. It is this air that starts the main cct. Later TQs had the bypass air routed from the air horn to the base plate, bypassing the pri bores & reducing the chance of n/drip. The bypass air travelled down the front two holes in the black body, which were enlarged on these models.
The idle cct is separate from the main cct. When the main cct starts, the fuel from THAT cct comes out of the brass nozzle of the booster. None of the fuel in the main cct gets to the t slots. After the fuel passes through the m/jet, some of it passes into the idle jet which supplies the idle & transfer ports. The CS TQ was different. While most carbs supply the idle jet AFTER the fuel has passed through the m/jet, the idle jet in the CSTQ is supplied direct from the float bowl, not via the m/jet. A few performance carbs such as Webers have this feature. Not sure why, but at WOT the idle cct is still supplying fuel. Having the idle separated may allow for more precise jetting.
 
Bewy said:
When you open the blades to expose more t/slot, you are also letting more air get past the blades. It is this air that starts the main cct
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Yes, understand all that, and the idle fuel is only supplied by the small brass tube inside the passage for the main cct.

I found the idle passages in the air horn blocked with that green crap, esp on the RH side, which was totally blocked. In turn, I had to crank the idle up a bit, which then caused the booster drip.
 
I'm just gonna add this and I am done. I'm tired of being argued down by self professed gurus. So I'm askin this. Since metering rods don't affect idle, as our thermoquad guru claims, then why is it that when an engine has low manifold vacuum from a large camshaft and the metering rod tree bounces because of an erratic vacuum signal causing the engine to surge at idle? I'll tell you why. It's because the engine certainly DOES see some fuel from the main jets at idle, just like the Carters, Edelbrocks, and the newer Street Demons. If you could "take the metering ford out" as our friend suggested, you'd not see any of that, since the metering rods don't affect idle in his world. I've seen it first hand in all the carburetors I mentioned. Believe whatever you will. Over and OUT.
 
Val,
The t/blades were open enough to start the main system, which you see as nozzle drip. Already covered all of that.

RRR,
If you think the main jets supply some idle fuel through the boosters, then block the jets & try again. The engine will idle just the same because at idle, the idle jet supplies the only fuel at idle. Only when the pri blades are open too far will the air speed increase enough to generate the DEPRESSION at the booster to initiate the main system [ main jets ]. And you would notice this as fuel coming out of the booster nozzle. There is only two ways that fuel that has passed the m/jet can be discharged into the t/bores: through the idle cct or the main cct [ booster]. Same for all the carbs listed....
 
The 'bouncing' met rods caused by low vacuum. Correct. And with a large cam, you get a rough [ surging ] idle; idle speed needs to be higher to prevent stallng. Opening the t/blades is one way to increase idle rpm, but the increased speed can initiate the main system. The correct way to tune for a large cam is to use BYPASS AIR so that the pri blades remain in their factory designed position. I drill the SEC blades for bypass air to ensure no nozzle drip from the primaries. If you think that is odd, remember this: lots of production carbs had hot idle compensators which added below the t/blades; this was done on the sec side of the carb. The engine doesn't care where the extra air comes from..as long as it gets it.
Another cause of large cams/surging is insufficient vacuum to operate the PCV, & that plays havoc with idle vacuum.
 
I have made a mistake in post #266 by suggesting to block the pri main jets. Since they also supply the idle jets, there would be fuel for idle. You would need to measure the idle jet & main jet sizes, & calculate the difference. Then block the jets with something of that area such that the only fuel that passes the m/jet is equivalent in area to the idle jet. No fuel left for the main system.
The important thing to remember with carbs like this is that any fuel from the main system that enters the t/bores can only do so by exiting the booster nozzle. There are no other holes or passages from the main system that exit into the pri t/bore. If the main system is adding fuel at idle, you will see fuel exiting the booster. If you do not see fuel, then it is NOT adding fuel.
 
Got a decent drive in today, not a hint of ping. Ran smooth, pulls hard with the secondary’s in. Timing is at 20 initial, 34 total, 12 vac. Vac is on MVA. Tune looks a bit on the lean side

IMG_0111.png
 
Compression test is interesting. The pressure has dropped a bit, but still at 200psi. It cranks over a lot easier than it did, so the cranking seems to have more to do with the actual timing events rather than the pressure on a gauge.

IMG_0113.jpeg
 
Valman said:
Got a decent drive in today, not a hint of ping. Ran smooth, pulls hard with the secondary’s in. Timing is at 20 initial, 34 total, 12 vac. Vac is on MVA. Tune looks a bit on the lean side

View attachment 1716385826
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The plug looks cold to me.

And it’s not lean. At least at idle and cruise. No one can see from those pictures what the tune up is like at WOT.
 
Newbomb Turk said:
The plug looks cold to me.

And it’s not lean. At least at idle and cruise. No one can see from those pictures what the tune up is like at WOT.
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Yeah, I couldn’t get a great photo there. It does look slightly richer toward the bottom of the porcelain.

I do have a set of plugs one heat range hotter to try. Good news is there’s no ping or flat spot. Didn’t get over 170f in traffic, good signs.
 
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