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Rock steady 9 inch vacuum at idle....

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Ranger_gone_straight
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Rock steady 9 inch vacuum at idle....

Post #1 by Ranger_gone_straight » Thu Apr 02, 2009 3:13 pm

I installed cheap vacuum gauge this morning on Ranger after hunting up fitting to directly connect to manifold. Got above odd reading. Ok new one on me so looked it up:

Image

Thats bit of screen shot of one of the vacuum gauge scenerios from: http://www.secondchancegarage.com/public/186.cfm which has nice collection of animated vacuum gauge scenerios.

Anyway sprayed starting fluid around carb base and intake manifold flanges to absolutely no effect. Figured that! since I have low smooth idle, very unlikely to have an air leak.

The other condition they suggest for this reading is "late valve timing"????? That would mean timing gear off a tooth or two. Unless a previous owner installed new gears incorrectly this seems highly unlikely.

Opinions? Other explanation? Worth the hassle to remove timing cover to have a look?

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Post #2 by mutt » Thu Apr 02, 2009 3:36 pm

timing retarded.......the needle is hold steady? theres no physical problem w/ the vac gauge? a ding in the case, bent needle?
its not t'd into the PCV vacuum?
the timing mark on the balancer can be off- the outter part w/ the timing mark is actually held in place by a rubber layer. These are reported to sometimes slip, making the mark arbitrary....

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Post #3 by AbandonedBronco » Thu Apr 02, 2009 3:44 pm

Hey Ranger,
From your previous post about the popping when you let off the gas, you still may have a vacuum leak in the manifold. I had an intake leak and practically hosed down the intake with fluid to see if it changed the symptoms and it never did anything or showed any symptoms. Of course, the popping could be from the timing. I know that's what everyone kept telling me to check.

Also, check to see that the vacuum gauge is good. It would suck to put work into your engine because of a crummy tool. I had that once, I checked the voltage on my car with a voltmeter I bought from Harbor Freight. Told me that the battery was putting out 3x the amount of juice it should, which indicated I had all sorts of problems. Turned out to be just a defective voltmeter. And definitely check to be sure it's on a full vacuum port, preferably one that's coming right out of the manifold.

Lastly, it very well could be the timing. Does the vacuum go way up with you turn the distributor?
1985 Ford Bronco Eddie Bauer. 300 I6. 9.1:1 CR, roller rockers, EFI manifolds and 2.5" exhaust. DUI ignition. 3.55 final drive, 5 speed ZF5. Holley Sniper EFI w/Offenhauser C Intake. 32" BFG KO2 A/Ts.

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Post #4 by Ranger_gone_straight » Thu Apr 02, 2009 3:53 pm

Brand spankin new gauge, no visible damage. It is a cheapie though.

Absolute rock solid 9 inch, no fluctuation.

Distributor is set with as much advance as lets me easily start it. Once running you can give it more advance without it pinging, but that makes it very hard to restart once you turn it off.

I have a timing light buried in storage someplace, havent used it for 20 years. When car companies started giving faulty settings to meet govt pollution standards instead of to make the engine run best it can, I just started timing by ear, make it ping then back off to where it has nice manners when starting and stopping the engine and no overheating.

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Post #5 by Ranger_gone_straight » Thu Apr 02, 2009 4:03 pm

AbandonedBronco wrote:Hey Ranger,
From your previous post about the popping when you let off the gas, you still may have a vacuum leak in the manifold. I had an intake leak and practically hosed down the intake with fluid to see if it changed the symptoms and it never did anything or showed any symptoms. Of course, the popping could be from the timing. I know that's what everyone kept telling me to check.

Also, check to see that the vacuum gauge is good. It would suck to put work into your engine because of a crummy tool. I had that once, I checked the voltage on my car with a voltmeter I bought from Harbor Freight. Told me that the battery was putting out 3x the amount of juice it should, which indicated I had all sorts of problems. Turned out to be just a defective voltmeter. And definitely check to be sure it's on a full vacuum port, preferably one that's coming right out of the manifold.

Lastly, it very well could be the timing. Does the vacuum go way up with you turn the distributor?


A low smooth idle like I have would indicate no vacuum leak. I simply cant give it more advace with distributor without making it a royal pain to start. I tried this morning and starter really complained like when you have a low battery. Put timing back where it was and started quickly and easily.

Its a cheapie gauge so that is in my thoughts that its faulty or miscalibrated. I have an old high quality gauge, probably buried with my timing light and tachometer. I'd almost rather buy it over than dig through all that to try and find it.

As the link I gave says late VALVE TIMING not ignition timing. Moving the distributor wont change when the valves open and close. Just changes when the plugs fire.

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Post #6 by Ranger_gone_straight » Thu Apr 02, 2009 4:13 pm

And as I pointed out in first post, vacuum gauge connection is directly to fitting screwed into manifold.

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Post #7 by American Thunder » Thu Apr 02, 2009 5:43 pm

That's pretty damn low idle vac, and steady? hmm. What is the idle rpm anyway?

Did you test the vac at 2000 rpm, too? It should be 19-21" at that speed.
1977 530hp 302 Mustang II videos:
Smokeshow at 8000 rpm
0-90 mph speedometer view

1983 4x4 Bronco - '95 300 converted to carb, 5-speed, 3.55 gears and 9" rear.

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Post #8 by Ranger_gone_straight » Thu Apr 02, 2009 7:12 pm

American Thunder wrote:That's pretty damn low idle vac, and steady? hmm. What is the idle rpm anyway?

Did you test the vac at 2000 rpm, too? It should be 19-21" at that speed.


Absolutely steady, no twitching or fluttering. No tach available but rev engine and hold at higher rpm and it first drops due to opening of throttle plate, then rises and settles little over 10 inches. If these readings were double, it would be indication of a healthy engine.

Yep strange. Been while since I've used vacuum gauge, but they are darn handy if you can figure out the results. There is an important clue here, just not sure what it is as I've not seen this before. I am still tempted to pull timing gear cover, just on off chance somebody did something stupid in the past. If this had been a timing chain engine I would have replaced it on general principles before installing engine, but gears rarely give trouble and there were enough other bits and pieces to buy.

Idles around 500 to 600 I would guess. If I dont give it bit gas the alternator light doesnt go off.

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Post #9 by rhetor » Thu Apr 02, 2009 7:35 pm

What UNITS does the gauge read out?

Can you test the vacuum of another vehicle?
300- mild head porting - 204/214 cam - 1.73 rollers - 2.5" exhaust DEAD AND GONE!

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Post #10 by Ranger_gone_straight » Thu Apr 02, 2009 8:27 pm

Reads in inches of mercury or inHg.

And yes been thinking of putting this on the 300 in my 3/4 ton as a test of the gauge. Its a proven good engine. Just been raining all afternoon and now getting dark and rather chilly. As they say, tomorrow is another day.

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Post #11 by 80broncoman » Thu Apr 02, 2009 10:07 pm

does the engine smoke any?
does the engine have a stock cam?
Have you unhooked the vac hose going to the brake booster and plugged it off to see if it makes a difference?
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Post #12 by sasktrini » Thu Apr 02, 2009 10:09 pm

Late valve timing is a stretched timing chain.
sasktrini, Saskatoon, SK, Canada

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Post #13 by AbandonedBronco » Thu Apr 02, 2009 10:30 pm

sasktrini wrote:Late valve timing is a stretched timing chain.


The 300 doesn't have a timing chain though.
1985 Ford Bronco Eddie Bauer. 300 I6. 9.1:1 CR, roller rockers, EFI manifolds and 2.5" exhaust. DUI ignition. 3.55 final drive, 5 speed ZF5. Holley Sniper EFI w/Offenhauser C Intake. 32" BFG KO2 A/Ts.

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Post #14 by Ranger_gone_straight » Fri Apr 03, 2009 5:37 am

80broncoman wrote:does the engine smoke any?
does the engine have a stock cam?
Have you unhooked the vac hose going to the brake booster and plugged it off to see if it makes a difference?


No smoke, no noticable blowby.

Stock cam as far as I know. I bought this engine, it still had feedback carb and bunch junk attatched. I cant imagine somebody putting a special cam in such an engine and leaving all other stuff stock. It apparently has been overhauled in its life. When I had head off cleaning up head, noticed it had .040 oversize pistons.

No, havent plugged brake booster hose but brakes are fine, be surprised if booster leaking, but definitely something to check though if it were significantly leaking, then it would be like any other manifold leak and you wouldnt get low smooth idle.

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Post #15 by Ranger_gone_straight » Fri Apr 03, 2009 5:44 am

AbandonedBronco wrote:
sasktrini wrote:Late valve timing is a stretched timing chain.


The 300 doesn't have a timing chain though.


Yep, would have to have a skipped tooth or really careless install of timing gears. I doubt this but suppose if nothing else will have to check.

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Post #16 by Ronbo » Fri Apr 03, 2009 7:54 am

Like you were planning on doing, throw the gauge on another vehicle and see what it does. There could be a leak in the tube from a bad solder job or crack. The stuff you get nowadays.....makes you want to cry!


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Post #17 by Ranger_gone_straight » Fri Apr 03, 2009 9:37 am

Ronbo wrote:Like you were planning on doing, throw the gauge on another vehicle and see what it does. There could be a leak in the tube from a bad solder job or crack. The stuff you get nowadays.....makes you want to cry!


Ron


Bingo, it is faulty gauge. After installing a porcupine fitting on the 3/4 ton and plugging all but one port, installed gauge and 7 inches.... Happened to see old Miteyvac hanging in tool shed and it has a vacuum gauge. Hooked it up and 18 inch on the 3/4 ton and 17 inch on the Ranger.

Well been kinda neat if I had found unique situation, but just more gauge problems. Kinda wish I still had the vac gauge that came in 1956 Ford school bus converted to camper I used to have. That was one elaborate top end gauge.

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Post #18 by Ronbo » Fri Apr 03, 2009 9:41 am

I work in a calibration lab and we see "pieces of work" if you will. Thats why I was going with the bad gauge theory. Glad its fixed without a major issue. Bet that thing hauls butt!

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Post #19 by American Thunder » Fri Apr 03, 2009 9:42 am

The items made in 1956 put modern stuff to shame.
1977 530hp 302 Mustang II videos:

Smokeshow at 8000 rpm

0-90 mph speedometer view



1983 4x4 Bronco - '95 300 converted to carb, 5-speed, 3.55 gears and 9" rear.

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Post #20 by AbandonedBronco » Fri Apr 03, 2009 9:58 am

American Thunder wrote:The items made in 1956 put modern stuff to shame.


That's back when people were proud of their work instead of seeing how many they could punch out to make a profit.


Glad that it was the gauge. That makes it a simple fix. :D
1985 Ford Bronco Eddie Bauer. 300 I6. 9.1:1 CR, roller rockers, EFI manifolds and 2.5" exhaust. DUI ignition. 3.55 final drive, 5 speed ZF5. Holley Sniper EFI w/Offenhauser C Intake. 32" BFG KO2 A/Ts.

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Post #21 by mutt » Fri Apr 03, 2009 11:29 am

I pulled a vacuum gauge out of a '50's Ford dumptruck some 30 years ago. Big old beast.
It sits in the corner of The Senators dash, with the tach taped to it.
aHEM, you will note I suspected a duff gauge........

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Post #22 by Ranger_gone_straight » Fri Apr 03, 2009 12:14 pm

I think the Senator's vac gauge was brother to one I had in the schoolbus.

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Post #23 by Ranger_gone_straight » Fri Apr 03, 2009 12:34 pm

Oops hit post button early.

Anyway the gauge is side issue now. Still odd behavior with 300 in the Ranger with the rumbling over 2000 rpm. So I have a spare duraspark distributor and just now installed it. Same idle rpm, but now I have 18 inch vacuum on the miteyvac. Woohoo!!!! And I have to leave the vacuum advance disconnected or it has too much advance. Different sounding engine. I'm curious how it drives.

So suspect mechanical advance wasnt working properly on original distributor with too little advance. On this spare, obvious the mechanical advance is bit too gung ho. I had a '71 Volvo like that, just drove it with vacuum advance disconnected and worked fine.

So first duraspark is too retarded. The second duraspark is too advanced. And the duraspark in my 3/4 ton is just right. Feel like a greasemonkey Goldylocks..... Dont much want to disassemble 3 distributors, but am very curious what the difference is.

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Post #24 by shortbox07 » Fri Apr 03, 2009 1:19 pm

they probably all have different mech. advance plates in them. its an easy change if you dont mind tearing the dizzys apart. i like to put a very light coat of wd-40 on mine to keep it all moving freely and avoid corrosion.
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Post #25 by Ranger_gone_straight » Fri Apr 03, 2009 4:24 pm

Ok, wont even ask the obvious question of why there would be mechanical advance plates in existance that would advance too slow or too quick for the engine. Just assume to meet some esoteric govt regulation but thats still no good reason.

Do they sell these plates as replacement spares or is it just luck of the draw when you buy a used or rebuilt distributor? I did notice a little aluminum tag with numbers on it much like tag on carburetor. Seems like this would greatly influence gas mileage and drivability. Maybe part of reason why some on this board seem locked into 9mpg yet others can get 20+mpg.

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Post #26 by Craigwell » Fri Apr 03, 2009 4:37 pm

This is where i swoop in with two of my favorite links to post here.

You can get different plates for your distributor, or you can modify them yourself with a little fillet weld, and a small bastard file.

Also, you can adjust both the rate of your centrifugal advance, by bending little spring tabs. This requires nothing more than a little screwdriver and you removing the cap and rotor button.

Finally, the vacuum advance rate can be adjusted also with an allen wrench.

Here's all the info, a great read.

http://www.carbdford.com/viewtopic.php?t=5543
http://www.carbdford.com/viewtopic.php?t=5392
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Post #27 by AbandonedBronco » Fri Apr 03, 2009 4:49 pm



Wow, I've been looking for that kind of information forever. Thank you so much.
1985 Ford Bronco Eddie Bauer. 300 I6. 9.1:1 CR, roller rockers, EFI manifolds and 2.5" exhaust. DUI ignition. 3.55 final drive, 5 speed ZF5. Holley Sniper EFI w/Offenhauser C Intake. 32" BFG KO2 A/Ts.

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Post #28 by Craigwell » Fri Apr 03, 2009 5:10 pm

someone posted those links in the small six forum months or even years ago. I dug them up when I was searching the the threads for dizzy info.

..and yes, I was chasing ghosts at the time regarding poor fuel mileage in my F250 :oops:
1995 F150 4x4 4.9L E4OD Mule / Plow Truck
Gone but not forgotten: 1976 F250 4x4 300 six, NP435. Dana60/44HD 4.10 Traction Lok, EFI Exhaust, 240 Head

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Post #29 by tj300 » Fri Apr 03, 2009 6:26 pm

Here's a real good vacum gauge visual mutt posted on another thread.
http://www.users.bigpond.com/ergoff/vac1.htm

I never realized what an important diagnostic and tuning tool the vacum gauge was until I saw this link mutt posted. I heard everyone talk about them but I didn't grasp it until just very recently. I'm buying a vacum fitting this weekend to put in my intake and a gauge.
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Post #30 by Ranger_gone_straight » Fri Apr 03, 2009 8:28 pm

Thanks for article on the advance plates. Going to have to take distributor out of my 3/4 ton and see what plate its using. Engine is heavy duty 1977 version with no pollution stuff from factory. Whatever they did, they got it right. One of best stock 300s I've run across. Now Ranger lot lighter so probably could take more advance, but I'd not object to it having same personality as the F250 engine.

No problem welding and trimming to size with dremel, whatever is needed.

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