SOLVED: Still running poorly, still having vacuum issues

[cfmustang]

I won' t rehash all I have been going through the last year, I'm sure that everyone is familar with my problem.

It has been too hot to work on the car lately (till my new 3-row shows up), but I decided to pull a couple of plugs after last weekend long drive to see how they looked. Not too bad. They looked close to normal - maybe a touch sooty.

I figured since I was under the hood I may as well start it up. Well, it was back to its old tricks. Idle swinging up and down and still too low with the idle screw pegged as far down as it will go.

So, I got my new vac pump out and hooked it up to the ported source off of the carb...5-6 Hg. Low.

Then I tried checking off of the pvc valve for full manifold. While trying to get the nipple off the pvc valve, the whole valve came off. While I got a lot of noise from the open crankcase, the idle quality did not change. Once I pulled the nipple of, the idle sped up and smoothed out. I put the pump on there and read about 7-8 Hg
.
How in the world can a vacuum leak make the car run better? This is driving me bannanas!!!!

Should pulling out the pvc valve stall the car? Shouldn't that vac leak cause it to run rough?

 

[CobraSix]

If you induce a vacuum leak and your car idle smooths out, you have a carb running too rich.

As far as the PCV, my understanding is that isn't really only to vent positive crankcase pressure, which isn't supposed to be happening in the first place. It's a check valve that only opens when you get positive pressure. At least thats the way it works on large marine diesel engines that I work on on a daily basis. If its the same (I'm not 100% sure on gasoline engines), this by pulling it and getting a smoother idle, you PCV is probably leaking and needs to be replaced. I've never had my idle change when I've pulled my PCV out of the valve cover while the engine is running.

So, I think you have a bad PCV valve and causing a vacuum leak when you pulled it fixing an otherwise rich condition...or, if the valve was leaking, it was causing the rich condition by syphoning crankcase fumes into the carb and you end up with unmetered combustables in the manifold causing a seemingly rich condition.

Button line, for starters, replace teh PCV, it's like $2 and will take 5 minutes max. See how that does for you.

Slade

 

[pedal2themetal45]

Just a quick shot isn't 5-6 hg. alfull low Hows your valve adjustment??
Tim

 

[WhitePony]

Just a quick shot isn't 5-6 hg. alfull low??
Tim

Depends on the lobe seperation on the cam. If that 272 Clifford has a 109* or lower, the vacuum will suffer greatly.

 

[cfmustang]

Slade,

Actually, the idle didn't change really when I pulled out the whole pvc value. I just heard a sucking (or actually the opposite of sucking) noise.

My pvc value has two nipples off of it. One runs to my direct manifold vacuum, the other was capped. I was trying to get a direct manifold vacuum reading so I was trying to pull the cap off of the unused nipple. It was when I pulled off that cap that the idle speed picked up and smoothed out.

I may replace the pvc valve just to be sure though.

Looking back though, this jives with when my the vacuum line disconnected from my c-4 vacuum modulator. The car shifted horribly, but ran better (because of the vacuum leak).

I guess what I am getting at is I am stuck. I can't get this carb tuned no matter what. I had it rebuilt and that made a little difference. I have rejetted the idle jets to what everyone recommended (I had to richen them up quite a bit) and that seemed to help a little bit, but now what you are saying is I am running way too rich.

All I know is that I can not get my idle fast enough using the idle screw to get the car running decent. It is pegged as far as it will go and the car is barely running fast enough to keep it running in gear with the breaks engaged. I have tested and retested everywhere I can think of for vacuum leaks and nothing (except that it runs better WITH a vacuum leak).

I really regret the day I started modifing this engine. It has been nothing but a problem ever since.

 

[CobraSix]

Okay, forget the PCV for now. Minimal issue IMHO.

Focused on the carb. Remember one think about jetting of carbs, everyone has their own recommendations, but unless you see the car running in your driveway with the exact same set up (tranny, cam, valves, exhaust, etc) as yours, it is still just a best guess and really up to trouble shooting for you.

Sounds like you are running rich, but a few things to trouble shoot (sorry if some of it is a repeat). Take a step back and we are going to reset everything.

1) Double check TDC on #1 and make sure your timing mark is on. Timing has lot to do with your carb, especially at idle.

2) Reset the carb to base idle mix setting. In other words, turn the idle mix screw all the way in (not sure if the weber has one or 2, autolire 2Vs have 2 and Holley 4vs have 2) and then 2 full turns out. This is a good start point.

3) Get the car started and check your RPM and timing. If you're RPM is above what you want to idle at, check your timing. If you are running above 15*BTDC, try dialing back some to around 12* BTDC. This should lower your RPM some. Then try dialing your idle mix in.

3) If you still can't get the RPMs up or down, try looking for your butterfly adjustment. Again, someone with more weber experience can chime in here. But there should be a screw that can adjust your idle position of your butterfly valve. On Holley 4v and autolite 1100, it's on the bottom of the choke assembly. It's seperate from the choke itself, but right at the bottom (may be touching in the case of the 1100). Try opening that up some. That will open the butterfly up and thus help the rich condition. You'll probably find your RPMS go way up. Do this adjustment in concert with the timing and idle fuel mix. Only open it like 1/8 of a turn at a time and readjust the fuel and timing. Eventually you'll find a point where the idle mix screw ill have more effect. My guess is this is the problem, your butterfly is too closed off. This is a very underused carb adjustment in my opinion. I never knew about it until I started fiddling with carbs a lot and when I couldn't adjust my idle speed no matter what I did to the idle mix screw.

See where that gets you.

Keep with it. modifying a car takes some patience, especially if you haven't worked with those items before. Much like me and messing with my rear end right now. If you knew how many times I've had to pull my axles back apart because of forgetting something, you'd feel better. Once you figure it out, you'll gain more insight into the car.

Slade

 

[Anonymous]

I'd try tossing the POS holley/weber in the trash and install a different carb in its place!

Either try a Carter YF or a Holley 350 cfm and see how that runs.

I think youre old carb must have a internal vacuum leak or somthing similar....youve tried everything else the past several months except switching to a different carb!

Later,

Doug

 

[cfmustang]

Hazzah!

I was driving home from working thinking on all that was said and decided to look at the carb adapter. I remembered seeing a threaded hole in the base and wondered if that was wide open sucking vacuum. Well, i checked it and it is not open all the way through (not sure what it is for then...) but noticed the other vacuum line that does go into the carb adapter that attaches to the pvc valve. The theaded fitting that goes into that that the hose is on was real loose.

I tightened that and started the car and it ran even worse. I pull the vac line off there and the idle shot WAY UP!

With the car limping at idle, I grabbed my timing light and decided to check the initial setting. Assuming that the mark is still correct (something I will try and figure out how to check later this week), it was at 6 degrees. So, I bumped it up to about 10 - 12 degrees. I can't do it any more or the dizzy diaphram is right over the dipstick. Anyway, the idle went up and it smoothed out. Now it idles around 900 rpm pretty smooth. I can even put it in gear with out it stalling. Although it is still a little rough. Before it used to have to be at 1100 to even put it in gear without stalling.

I had to come in and grab some dinner, but I am going back out after to take it for a drive.

I have a couple of questions though;

1) When I was bumping up the timing last weekend, any higher and it was pinging like mad on acceleration. I have already capped off the vac advance so it should have been just mechanical. Why was it pinging? Was it because the vacuum leak causing it to run rich or lean or something?

2) How can you advance your dizzy past 12 degrees initial without it hitting the dipstick? I have heard a reference to a dizzy being a tooth off. Is that what is happening here?

 

[Lazy JW]

You may well be a tooth off. I would try using manifold vacuum for the vacuum advance. This may allow you to get decent idle without having to over-advance your basic timing.
Joe

 

[cfmustang]

Okay...

I went back out side and took it for a drive. Not too shabby. It actually had some pickup and wasn't threatening to stall at idle.

I bumped the timeing a bit more and then it started pinging pretty bad. I ended up taking it back down to about 11 deg.

I took it for an extended drive and it is still pinging a tiny bit, so I need to bring it down a bit more I guess. What i did notice is that as I started to overheat, it ran rougher and pinged more. My new 3-row should get delivered tomorrow so that should take care of that.

Here are my concerns though. Every time I retard the timing, the idle drops. So, if I have to still retard it a bit more the idle will just drop more putting me back where I started. As it is, the carbs idle adjustment (there is only one on a Weber 32/36) is still almost all the way in.

Why is that?

So, when I try and set the carb to baseline I can't keep it running. The idle is too low...

Also, why can my timing only go to 10 or 11 deg without pinging while others here run around 14 degrees?

Also, I think I am hearing a miss in there. And, what causes the engine to shake badly at idle with the break is engaged (like a stoplight)?

 

[Lazy JW]

I suspect that when you get it running right you may not need the new three-row. The first step to curing overheating is to not generate excess heat. We do that by getting the timing and mixture correct.

1) Have you verified that the timing marks are indeed correct?

2) After verifying the timing marks, test for how much mechanical advance you are getting, and at what rpm. You may need to limit (re-curve) how much mechanical advance you get in order to allow enough basic timing and yet not have too much at higher speeds.

3) Before going to all that trouble, just try hooking the vacuum advance to manifold vacuum and see what happens. It should speed up the idle, yet when you accelerate it will drop off. Your driveability can be a lot better just by doing this and it won't cost much to try.

Joe

 

[cfmustang]

Well, I spent about 4 hours putting the new radiator in and while it takes a lot longer to get there, it is still overheating if I let it sit and idle for a while. Now it takes about 15 minutes and it used to take about 10 minutes.

You are proably right Joe. The excess heat is comming from the yet to be correctly tuned engine.

Unfortunately, it took way longer to replace the radiator than I expected so i will have to try and verify the timing this weekend. However, I am still not sure how to do it. I have read that you pull the #1 plug and watch to see when it is TDC but isnt that not very percise?

Also, pulling the radiator let me get a good look at parts of my engine compartment that I had never seen before. Yuck! My passenger side front frame where it attaches to the radiator support is rotted out completely. So, now I will have to have that replaced with the inner and outer shock towers... sigh.

 

[Lazy JW]

It takes a bit of effort to properly verify your timing marks but it is vital to the long term health of your engine so it is worth all the trouble.

1) You need a physical stop to install in the spark plug hole. I have made them out of old spark plugs by breaking the ceramic out, then using a tap to make threads inside the plug to install a bolt. An easier method is to get a bolt that has the same threads as your spark plug, then simply screw it into the plug hole.

2) For safety and ease of turning the engine by hand, remove ALL of the spark plugs.

3) Install the physical stop bolt in the #1 spark plug hole, turn it in so that it can contact the piston about 1/4" from Top Dead Center (TDC)

4) With the tranny in neutral, key OFF, and wheels blocked for safety, CAREFULLY rotate the engine by hand until the piston just touches the physical stop bolt. GENTLY now, we want a physical stop, not a hole in the piston.

5) Make a pencil mark on the harmonic balancer at the timing pointer. This mark should be some distance away from your existing TDC mark.

6) Now, rotate the engine the other direction (it doesn't matter which direction you start from) until it just touches the physical stop bolt again.

7) Make another pencil mark at the timing ponter

8) Now, measure EXACTLY halfway between the two marks. This is true TDC. If your damper pulley hasn't slipped, the original TDC mark should be right there, halfway between the pencil marks. If not, then the pulley has slipped and you need to make a new TDC mark

9) Next, you can make a set of timing marks on a piece of white tape in five degree increments up to 40 degrees. Do this by measuring the pulley, multiplying by Pi, dividing that by 360, then mark the tape and install on your pulley.

10) Now you can check the timing curve with your timing light

When you get this far, we can walk you through the next steps.
Good luck and have fun.
Joe

 

[MustangSix]

I can't imagine that a 200 with a new 3-row radiator, no matter how badly it's tuned, could possibly overheat at idle if the fan, pump, and thermostat are working.

Are you sure you don't have other issues like a bad gasket or a crack? That could also cause many of the other symptoms, including not being able to get it to run right. Compression is even? Cooling system pressure checked OK? Not all overheating problems are in the carb or ignition.

 

[Lazy JW]

Good point Jack,
If you have a blown head gasket there is no amount of tuning that can cure it. There is something fundamentally wrong in his engine, just need to eliminate things step by step. A compression check is always a good place to start, because with bad compression there isn't much point in continuing.
Joe

 

[addo]

It's odd. This motor has the guts of a good build, yet it's been problematic from day one. It almost seems as though there's been something overlooked in the original build. Current compression figures would be good to compare against any older ones, also cam timing, plus true TDC are of interest.

Regards, Adam.

 

[cfmustang]

When the engine was rebuilt, the block and head were magnafluxed for cracks and came up good.

I have not checked compression since I the car came back from the mechanic last year and I don't have any old numbers to compare to, but I think I have a compression tester somewhere in the box of tools I grabbed from my dad's garage. Does it look like a gauge with a rubber hose coming off of it with a threaded end like a spark plug? I think I remember seeing one. I assume you just pull a plug, attach the gauge and crank the engine. Then move down the line. I could probably do that tonight if I find the gauge. Will that be able to help me determine if it is a bad head gasket or a bad ring? The engine has less than 500 miles since the rebuild.

As for the work yesterday, I replaced the radiator, cap, upper hose and thermostat. I could not get to the lower hose because the power steering pump in the way and the top bolt for the pump to the braket is stuck and rounding off. I also did not replace the pump or heater core. I suppose it could be one of those things. However, I moved my old flexfan back from the radiator to prevent the engine torqueing the fan into the nice new radiator.

 

[Anonymous]

Insufficient timing at idle could easily overload the three row radiator. Retarded timing shoots the temperatures way up. However, since the engine rpm's are low at idle, the water pump is not circulating much cooland transporting the heat away from the engine at sufficient circulation rates. And the fan is not moving much air. Cooling and heat transfer are very much circulation rate dependent. I would inclined to believe there is a timing issue going on. Check for the slipped timing mark. Chris, I forget what distributor you are running.
Doug

 

[cfmustang]

I am running a 1968 dual advance (I chucked the Load-a-matic last Summer). However, I have been running it with the vac advance disengaged due to a bunch of suggestions prior.

Now, the idle is around 900 rpms because any lower and that lopey cam of mine causes the engine to shake more than Charro on a Love Boat rerun.

I suppose it could also be related to the fan too. It is a flexfan, but it is about 10 years old. Do those things lose their ability to draw air (by flattening out too much) as they get older?

 

[Anonymous]

With a lopey cam and more valve overlap, you should be able to run more initial advance since the dynamic compression ratio would be lower at idle and there would be more combustion gas remaining in the cylinder diluting the incoming fuel charge. That all assumes that your compression ratio is not too high in the first place. Assuming that the timing mark does prove to be correct, could it be that the recent engine work has created a motor that requires premium fuel?
Doug