Major tuning problems -too much vac. advance???

[Anonymous]

Doug and Doug ,

'66F.B,

I'm assuming my SCV is not working at all- but I am getting no vacuum at the carb at all when I rev the engine at low speeds, and I know the ported vacuum passage is not plugged. I know this is the wrong carb for me to be running- that's what started this whole mess! I am going to hook up to manifold vacuum for the time being since my real goal is to get the YF to function correctly. My mileage is reall crummy right now even though the misfire is gone since I pulled off the YF- probably due to the lack of vacuum advance, I hope.

Mustang_Geezer,

Thanks for the directions on adjusting the jetting mixture. How do I check the float level? I'm assuming it is not too far off, as the car does not start hard when warm like all my 1100's have, and does not hesitate in turns. I'm hoping the gasket will be okay- it's a new carb and I've only run it for 2-3 days.

Nobody has answered the key question yet- does running lean cause excessive vacuum? If not, I'll have to try another carb.

I had a new head pipe and gasket put on at Midas today- $145 plus tax I should have gone and got a header as I'll have to do this again when I install one. My whole system was about the same price 4 years ago. To add insult to injury, I have a manifold leak at the head as well- I just couldn't tell with the pipe making so much noise. Being it's a low mileage engine and the gasket should be good, I expect something will need to be machined smooth- hopefully not the head. I'm ready for some good luck to start happening.....

 

[Lazy JW]

Nobody has answered the key question yet- does running lean cause excessive vacuum? If not, I'll have to try another carb.

I really don't see how running lean can cause excessive vacuum. The amount of vacuum is a function of various factors, but the single biggest factor is how far the throttle is open at any given moment, the next factor is probably the amount of "pull" the cylinders exhibit. This will be detirmined by how large the cylinders are, how many cylinders, cam timing, port/valve efficiency, rpm, etc. Altitude has an effect also. If running lean somehow caused the throttle to be more closed then I reckon the vacuum signal would go up, but it just seems like it wouldn't be significant. Have any of you dyno jockeys seen this happen?
Joe

 

[Falcon62]

I thought the heat choke actually used a tiny vacuum line (connection/tunnel) within the carb to draw the hot air into the choke area and then down into the carb. Isn't that what one of the tiny ports on the bottom of an 1100 is for?

By golly, you're right Steve (and Chaz). There is, in fact, a small vacuum port in the carb body that pulls heated air from the choke tube into the choke housing where it warms the bi-metallic spring. However, there should not be an opening in the exhaust manifold allowing exhaust gases into the choke tube.

All these years I've been under the misconception that heated air rising into the housing was sufficient to heat the spring. Guess it needs a little help getting there.

 

[Anonymous]

Nobody has answered the key question yet- does running lean cause excessive vacuum? If not, I'll have to try another carb.

the single biggest factor is how far the throttle is open at any given moment, the next factor is probably the amount of "pull" the cylinders exhibit. This will be detirmined by how large the cylinders are, how many cylinders, cam timing, port/valve efficiency

This is kind of what I'm getting at- regarding the comment about cam timing, could a mistake have been made in regards to the timing chain/gear installation that would cause this?


Phil,

So does this mean I should plug that choke hot air port? I did not notice a differance in the way the car ran when I did, but the rubber plug I had was not the right size and fell out.... Where is the air coming from that flows through hole in the exhaust manifold into the choke tube if it is not exhaust gasses?

 

[Anonymous]

Thor,

On a very few of the YF's there is not a screw to richen it....there is just a tab that you have to bend.
Later,

Doug

Crap. Naturally, I have the one without the screw, and was not thinking and bent it down instead of up, thereby leaning it out more :roll: The car runs worse now, not better.

While running the autolite yesterday, I connected the vac. advance to the manifold instead of the carb. This gave me 40 deg. of advance at idle (with initial set at 14 deg. ) With this carb it's either way too much or none at all. I checked, and my distributor does not have adjustable vacuum feature.

Back to the YF; I can richen it up and will try to do so tomorrow, but it sounds as though this will not solve the vacuum problem. What's next? I need to resolve this soon (this is getting tiring and taking all of my free time- my friends are getting tired of "sorry, I have to work on my car"...) so I may just return the YF if things do not work out tomorrow. When spending $105 on a new carb, I expect it to work better than this.

Thor

 

[Lazy JW]

Thor,
I really doubt that improper cam timing will cause too much vacuum, it usually results in LESS vacuum. It is not all that hard to check the cam timing though, just need a degree wheel or mark the crank pulley and a dial indicator.

Methinks that 26 degrees of vacuum advance is WAY too much. About half that much ought to do the job, your distributor needs a bit of attention also. I really recommend leaving the vacuum advance unhooked until the carb is dialed in. It just adds to the confusion.
Joe

 

[Anonymous]

I've just returned the POS YF with hopes of getting another one that's better. Regarding the distributor, does the small block ford distributor use the same vacuum advance as the 200? I know they make aftermarket adjustable ones, which obviously I need, but I'm not sure if it will work on my distributor.

 

[Anonymous]

I've decided to buy a rebuilt carb. My carb has 2 stripped screw holes, so i have a vacuum leak....i used non hardening gasket sealer, and that sorta works....but i gone and broke it ahh well...gas mileage was very fluxuating with it. so should i go with another YF? looking for cheap yet effective.

 

[Anonymous]

Dave,

I think it comes down to personal experience. I've never had good luck with the autolites on any of the 3 or 4 falcons/comets I've had, so that's the main reason I went to the YF. I asked a local rebuilder recently which was the better carb- the carter or the holley 1bbl used on the late 70's fairmonts, and he said the carter was the best way to go. His second choice was the aftermarket holley (no longer made) that was made to replace the autolite 1100. I've seen those on ebay, but they are made for the earlier small bore 170/200 so would not be the best choice for your later engine.

Thor

 

[goinbroke2]

I doubt it's your problem, but for an answer, yes cam timing will change manifold vacuum. If the cam is advanced your vac will be higher, and if it's retarded it will be lower. Also a cam with more overlap or closer centreline will have lower vac...and if...

If the cam was put in a tooth out, and that only equaled 4-6 deg advanced, then in theory, it would give higher vac and increased cyl pressure which could cause detonation. I think there's too many other variables that are being changed at the same time and wrong conclusions are being made.

It doesn't have to be so complex. Change one thing at a time after getting a baseline.

Ensure your damper # are correct and zero'd, then set your initial timing and with the vac unhooked rev it and check your mech advance. If it's too much(more than 20deg) fix that problem before you move on!

You should end up with (for example) 15 initial and 20 mechanical totaling 35 deg total advance. If you have 40 total you can't just "crutch it" and back total off 5 deg because the engine will have lower vac/crappy start/bottom end/etc with only 10 initial.

So, you now have 15 initial, a total of 35. Now check your vac canister, you already said it works when you apply vacuum, so, when do you want it? At tip in when your idling down the road right? So you need a vac source that will give zero vac at idle, and vac when you step on it. Find a port on the carb that does this by testing any port you see with a vac guage.

Next problem, how much vac advance does it produce? An earlier post you stated it gave 26 deg of advance. Add that to your 15 initial and you get 40-41 total. This is too much and WILL cause detonation at lower rpm or high load.
So now the next problem to solve is limiting your vac advance 6 deg for a total of 20. If your canister on the dist doesn't have an allen key adjuster, you'l have to be creative. Anything from bending the vac advance arm inside the dist housing, to redrilling and rerivetting the point where the arm connects to the advance plate.
All done? Great! NOW you have proper timing control and it's out of the way.

Next is to diagnose the carb.....but finish the dist first.

Or..you can change this carb and that vac line and this alternator and that tailight assy and this wiper arm and And never know the REAL reason if/when it starts running good.

 

[goinbroke2]

haha, never answer your question Lazy! Yes I've seen a lean engine produce more vac, but it was due to increased rpm. You've seen it too if you've ever played with a chainsaw/lawnmower/etc. When an engine is rich, the rpm drops and it "stumbles" along at idle until it is so rich it idles down and dies. But if you lean an engine (from correct starting point) then the rpm (and vac) goes up until the engine peaks and shuts off.
If rpm was adjusted to be the same lean or rich, I don't think the vac would be different. But I've never personally tried to do this. Never had a reason to.

 

[Anonymous]

Dave,

I think it comes down to personal experience. I've never had good luck with the autolites on any of the 3 or 4 falcons/comets I've had, so that's the main reason I went to the YF. I asked a local rebuilder recently which was the better carb- the carter or the holley 1bbl used on the late 70's fairmonts, and he said the carter was the best way to go. His second choice was the aftermarket holley (no longer made) that was made to replace the autolite 1100. I've seen those on ebay, but they are made for the earlier small bore 170/200 so would not be the best choice for your later engine.

Thor

thanks for the input Thor. I'm gonna give one finall go on the current carb and try to get it to seal properly (i have 2 stripped screws) so i'm thinkin of JB weld or something, lol...but i'm gonna keep it running rich though cause i'm gonna be adding a turbo, althouh i might also use a 2bbl and make a direct mount..i figgure if i use one from a 350 or something it should be rich enough to keep from detonation when under boost....

 

[goinbroke2]

Double checking, I reread your first post again. I noticed you said your points are at .025. Back "in the day" the factory called for 18 or 20 or something like that and I always set them at 15 because of a idle or low load miss. Of course that was on 351c's and 302's and other performance stuff that rolled through my door, but you get the point. Too much point gap will decrease much needed dwell and coil saturation time.
Just something else to consider.

 

[Lazy JW]

haha, never answer your question Lazy! Yes I've seen a lean engine produce more vac, but it was due to increased rpm. You've seen it too if you've ever played with a chainsaw/lawnmower/etc. When an engine is rich, the rpm drops and it "stumbles" along at idle until it is so rich it idles down and dies. But if you lean an engine (from correct starting point) then the rpm (and vac) goes up until the engine peaks and shuts off.
If rpm was adjusted to be the same lean or rich, I don't think the vac would be different. But I've never personally tried to do this. Never had a reason to.

That has been my observation also about the lean condition in chain saws. When the rpm is at specs, the vacuum will depend heavily on the throttle position. I am aware that cam timing has an effect also, but there is truly a limit to how much vacuum will be developed. With engines that use a timing chain, even one tooth off will be a lot. I don't know how many teeth are on the sprockets, but I'll bet it would be noticeable. But, even with Mega-Vacuum, the canister shouldn't deliver that much advance. I still say leave it unplugged until last. Plenty of other things to worry about first.
Joe

 

[goinbroke2]

Lazy wrote "I still say leave it unplugged until last. Plenty of other things to worry about first.
Joe"
Exactly!

I remember one time figuring out how many deg each tooth would be, but I forget what engine it was....crap now that's going to bug me....I've got 4 or 5 sets of double roller small block ford out in the shop, back in a bit.

 

[Anonymous]

You should end up with (for example) 15 initial and 20 mechanical totaling 35 deg total advance. If you have 40 total you can't just "crutch it" and back total off 5 deg because the engine will have lower vac/crappy start/bottom end/etc with only 10 initial.

Total advance at about 32 deg, is indeed what I have with the vacuum unplugged. When I hook up the vacuum advance (with the new carter YF carb) is when it goes up to 50 deg. Again, this carb only has one vacuum port so I know I'm using the correct one. I really can't go the route of adjusting the distributor before the carb as I have a worn out 1100 on there right now that does not give any advance at all.

See my other thread "Vacuum advance tuning" where Mustang Six made an interesting comment "You may well have 50 degrees of total advance at no-load, high rpm operation (initial+mechanical+vacuum) such as coasting, but the vacuum advance will retard under load" this confuses me a bit as a recent article I saw on checking total advance said that it should be no more than about 35 deg total, but with all advance including vacuum (or I thought so). I have to go back and check that again....

Thor

 

[goinbroke2]

It took a bit longer cause I walked by the bronco project and seen the new fuel line just sitting there begging to be put on. Couple bends and a half inch wrench and I have a factory looking steel line from the pump to the carb.
Anyway, Cloyes true roller, ford motorsport and factory 5.0 double roller chains all have 21 on the crank and 42 on the cam.
That equals to; 4.28 degrees if you move one tooth on the cam gear, and 17.14 if you moved the crank.
I know your thinking, that doesn't sound right.
360/42=8.57 BUT, it's the cam gear which only turns half the speed of the crank. So, 8.57/2=4.28
The crank on the other hand is what everything is based on so 360/21=17.14.

In theory then, if you had a crank/cam gear count of 50-100, then you'd have 7.2 or 1.8 per teeth respectively.
In theory! :roll:

If anybody has a timing set for a 6 sitting around go count it and post the # please.

 

[Anonymous]

This is my daily driver, so I'm hoping to avoid anything relatively major like pulling the timing cover, until spring when I plan to pull the engine for detailing before the falcon nationals. I'm a little hesitant to start bending and drilling inside the distributor- my experience is once you modify something in that manner you can't get it back to the way it was if you end up doing the wrong thing! If I had a puller, I'd pull apart the front of my 170 I just took out and look at the chain, but I don't

 

[addo]

I get 19/38 for the JP chainset. And just checked my 221(

) to find the same numbers, stock.

720°÷38 = 18.9°

That's what one tooth will do for ya! Not likely, eh?

 

[Anonymous]

just checked my 221(

)

You need to get out more...