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Vacuum leak in the Valvetrain? (First post)

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Tyro77
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Vacuum leak in the Valvetrain? (First post)

Post #1 by Tyro77 » Wed Aug 16, 2017 9:20 am

Hello everyone this is my first post here so I apologize if this isn't the correct section!

I have owned a 64 1/2 Mustang I6 170 for about a year now and have still yet to have it on the road. When first got the car it ran but wouldn't idle low (Below 1000 rpm). It had the wrong distributor, wrong carburetor and a few other issues that I thought would cause the problem. I replaced the carburetor with the correct automatic Autolite 1100 and the distributor with the correct vacuum advance distributor. I set the timing, adjusted the valves (hydraulic in this case) and put new fuel in it. So I took care of the obvious and was still having a problem! From there I started the real diagnosis process. I ran a compression test and all the cylinders had good compression. From there I put a vacuum gauge to the intake, the vacuum was rapidly going from 15-20 back and forth. So I thought there it is I have a sticking valve! I took the head off and took it to my local machine shop and had them go through it and put new valve seals and re-seat the valves. I replaced the head gasket and exhaust gasket then put the head back on. I then readjusted the valves and put it all back together. It would not run unless I was constantly giving it gas. From there I readjusted the carburetor checked the valves over again and got it running without my foot on the pedal while still at a high rpm just like before. I put the vacuum gauge on and I am still having the same problem! If anyone has any experiences with a problem similar to this I would love the advice I just want to get my car on the road and to be able to enjoy it! This is my first vintage project and this is all pretty new to me so I am sure I have missed things that would be obvious to someone familiar with these vehicles.

TL;DR Vacuum gauge going from 15-20 rapidly and it doesn't appear to be a sticking valve.

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Re: Vacuum leak in the Valvetrain? (First post)

Post #2 by ags290 » Wed Aug 16, 2017 3:04 pm

Have you done a cylinder leak down test? Did the machine shop check the valve guides for wear? Those would be the two places that I would start.

Kevin
Kevin
Early 1965 Mustang with a 170

Tyro77
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Re: Vacuum leak in the Valvetrain? (First post)

Post #3 by Tyro77 » Wed Aug 16, 2017 5:56 pm

The machine shop told me everything was good with the valves. I didn't ask specifics which I probably should have but this has been about 10 months or so ago but I would hope they checked everything since that is what they charged me for. I will see if I can get a leakdown tester and perform it. But what would a leakdown test tell me that a compression test does not?

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chad
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manafold v port vacuum

Post #4 by chad » Wed Aug 16, 2017 10:39 pm

W E L C O M E !!
to the site and the best forum onhere! Yes, I'd say ur in the right place (but plez, check the others out too).

It seems you can do some work on this vehicle yourself. I maintained a mid/late 60s vehicle for several decades. Unfortunatly I really knew nothing about it (fooled myself) and just got into trouble when going beyond the basics (still little to no theory here). What really helped get me up to speed was "the Handbook" (on line from Matt at vintageinlines.com) and while waiting for delivery - the use of this site's "Tech Archive" (click onit above). Not sure you have this info but it sure helped some 1 like me~

C Seth below: "...non lom dist and carb..."
Last edited by chad on Wed Aug 16, 2017 11:06 pm, edited 1 time in total.
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), 250, NV 3550 & DSII to B transplanted, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", tool boxes, etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com (413) 259-1749

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Econoline
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Re: Vacuum leak in the Valvetrain? (First post)

Post #5 by Econoline » Wed Aug 16, 2017 11:02 pm

How's the fuel system, tank lines filters pump? It sounds like you've gone through it pretty well. There's no adjusting hydraulic valves unless there's a solid lifter rocker assembly. Are you wanting to keep it era correct? The po might have put a non lom dist and carb on there, which is an upgrade and improvement with a DS2.

You say you set the timing, what is it set to? What transmission do you have? Where's the idle mixture screw turns or what's it doing?

Sometimes it's helpful to advance or set the timing by ear so it runs well. Make sure the mixture screw isn't turned in to far. It will probably like something between 6 and 15 BTDC. Then check/set the timing and set the idle speed and mixture. My Econoline's 170 had a parts store "rebuilt" carb, ages old, 1100, that was misassembled. The previous owner drove it years with the carb. But it wouldn't run without gas and some choke. I rebuilt it and found it was missing it's weight and a check ball in another hole. It idled fine and ran OK after the rebuild, but loved to hesitate off the line if the weather wasn't right.
It ain't gonna fix itself

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Re: Vacuum leak in the Valvetrain? (First post)

Post #6 by ags290 » Thu Aug 17, 2017 10:45 am

A leak down test is kind of like a compression test in reverse. The big thing that it will tell you is if you have a valve issue or head gasket issue with an individual cylinder or pair of cylinders. Additionally if you have a single cylinder with a higher percentage of leakage than the others you can listen for the escaping air to see where your issue lies (Rings, Intake Valve, Exhaust Valve or Head Gasket). Look at your paperwork from the machine shop to see exactly what they did. Most budget valve jobs are seals, lapping the valves, and maybe knurling the guides. If the guides have too much clearance the valve will wobble when it is opened and closed and can allow unmetered air and oil to enter the cylinder.

I am not saying that there is an issue with the head or the head gasket, just that I would perform a leak down test before I started taking a bunch of stuff apart.
Kevin
Early 1965 Mustang with a 170

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Econoline
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Re: Vacuum leak in the Valvetrain? (First post)

Post #7 by Econoline » Thu Aug 17, 2017 11:21 am

X2, youre vacuum readings are indicative of a valve problem. You might as well do the leak down to see for sure whether or not it's an issue.
It ain't gonna fix itself

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Re: Vacuum leak in the Valvetrain? (First post)

Post #8 by Tyro77 » Thu Aug 17, 2017 11:24 am

The fuel tank could probably stand to be replaced It sat for a few years before I got it. I put new gas in it but I'm sure there is rust floating around in it. I did put a new fuel filter when I put new gas in there though. It does actually have the rocker assembly with lash adjusters which I believe should have solid lifters but it has hydraulic lifters according to what I read on classicinlines. I am not really worried about keeping it era correct at the moment at least, it will be quite some time before I actually get into restoring it I just want it to be a driver at the moment. I set the timing to 10 btdc with a timing light. I have a C4 trans, it came with a manual 3 speed which is why the carburetor was incorrect. It still had the manual trans autolite 1100. I don't know what the reason was the for distributor swap but it was not a vacuum advance distributor. It also wasn't a DUI like you see so many people swap in. I set the idle mixture 2 turns to the left from it being bottomed out. I ordered the carburetor from Carburetor specialist in Alpharetta GA and have dealt with them previously so the carburetor should be built correctly. Either way it was doing the same thing with the previous carb vacuum wise.

Tyro77
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Re: Vacuum leak in the Valvetrain? (First post)

Post #9 by Tyro77 » Thu Aug 17, 2017 11:33 am

ags290 wrote:A leak down test is kind of like a compression test in reverse. The big thing that it will tell you is if you have a valve issue or head gasket issue with an individual cylinder or pair of cylinders. Additionally if you have a single cylinder with a higher percentage of leakage than the others you can listen for the escaping air to see where your issue lies (Rings, Intake Valve, Exhaust Valve or Head Gasket). Look at your paperwork from the machine shop to see exactly what they did. Most budget valve jobs are seals, lapping the valves, and maybe knurling the guides. If the guides have too much clearance the valve will wobble when it is opened and closed and can allow unmetered air and oil to enter the cylinder.

I am not saying that there is an issue with the head or the head gasket, just that I would perform a leak down test before I started taking a bunch of stuff apart.


I will perform a leakdown test asap and get back with you all with the results. Would I be able to feel the valve wobble by moving the valve and spring if it is bad?

I replaced the spark plugs when I got the car and noticed last time I took them out they are fairly black . That could mean that oil and air are getting in through the valve right? It also could be carbon fouled though this engine probably has a lot of carbon running though it.

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Re: Vacuum leak in the Valvetrain? (First post)

Post #10 by Econoline » Thu Aug 17, 2017 3:26 pm

You might go over those valve adjusters again. If a lifter wasn't pumped up you could have one over adjusted and hanging open when it's running.
It ain't gonna fix itself

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Re: Vacuum leak in the Valvetrain? (First post)

Post #11 by ags290 » Thu Aug 17, 2017 3:48 pm

X2 on the lash adjusters. My early 65 Mustang also has hydraulic lifters and the adjustable rockers. As far as being able to feel the excessive clearance from the valve guides you would have to be a lot more sensitive than I am. You are talking about thousandth's of an inch. Also make sure that you have the vacuum line connected at the transmission. That could be part of your high idle. Ask me how I know...
Kevin
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Re: Vacuum leak in the Valvetrain? (First post)

Post #12 by B RON CO » Thu Aug 17, 2017 8:20 pm

Hi, hook up the vacuum gauge and hold the rpm steady at 2000. If the needle bounces more, it is probably valve train related. If the needle steadies, it I could be a distributor advance issues. If your test points to valve train, I would loosen each rocker arm with the engine running, one at a time, until it clatters, and then snug it down s little at a time until it quiets down. You will probably find a couple of rockers s little too tight.
Dark black plugs indicates a rich mixture. Make sure the choke is opening all the way. Good luck
B RON CO. Still workin' on it!

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