Y Block Help Needed

OK, the issue on 5& 6 is solved. I seemed to swap those two plug wires when i reassembled it this morning. I meant to do a continuity test then, but got sidetracked and forgot. Vacuum is back in the 11 range, but it has a bunch of initial advance. When I crawled underneath to investigate an exhaust leak, I did notice that the rear main seal is leaking badly and there's a good bit of smoke vapor coming from the road draft tube, which makes me think it must be seeing a lot of crankcase pressure. Not good.
 
Makes perfect sense if your rocker arms are worn. If there is any groove the feeler gauge is worthless.

Being that we have no idea about the condition, cam, etc. it would get you in the ballpark.
 
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Thanks for the suggestions and continued support.


  • I have been checking the vacuum by disconnecting the line that runs from the intake manifold to the fuel pump and attaching my gauge to that line.
  • I have blocked off the brake booster, no change.
  • I have disconnected the vacuum line to the distributor and didn't see a change. When connected, the timing does advance with RPMs.
  • The mushroom shaped diaphragm on the side of the carb seems to move in about 1/16" or so when revved.
  • Vacuum is idle speed and ignition advance dependent. Initial advance is somewhere around 25 degrees. With the idle at ~750 RPMs, vacuum is ~7"hg. At 1000 RPMs vacuum is between 10 & 11"hg.
  • Placing the car in gear will drop the idle from 1000 to about 450, barely enough to keep running.
  • All the valves look to be opening the amount, but I have not measured yet to see if they are within spec.
  • The car seems to run best at ~25 degrees initial advance. Move it much further and it detonates under a load, retard it and it's really sluggish.
  • When the car is idling, there's a steady stream of fumes coming from the road draft tube. Is this normal?

I haven't checked compression since I have adjusted the valves, but plan on doing that this evening. Also, I will do a dry and wet compression check to see if it's a piston ring issue. The first test I did was dry and the cylinders were all in the 110-128 range.

At this point, I think that the problem is either the camshaft orientation or an issue with the rings.

The motor looks like it's been rebuilt (I know that the heads have been), but that doesn't mean anything. Maybe the engine assembler installed the rings wrong, or maybe they are all stuck because the car has done a lot of sitting after its restoration. Or maybe it was only painted and not rebuilt.

The fact that it needs so much advance makes me think that the timing set may have been installed wrong. A previous shop had pulled the timing cover to inspect this, but it's a foreign car shop, so their Y block experience is probably very limited. It could be they were looking to find the dots on the gears lined up at 6 & 12 o'clock like every other V8 that I've ever worked on. If I understand correctly, the dots on the gears should both be around 3:00 with 12 links between them.

Sorry for the long post, but I wanted to keep those of you who have been helping me up to date.

Thanks again,
Bobby
 
sure the distributor vacuum diaphragm isn't cracked and/or not functioning? I would think you would see some spark advance response with the vacuum line on, and then disconnected. I had a Yblock in here a couple years ago where it ran like crap, and several shops tried to sell him a carb. It was a failed vacuum diaphragm in the distributor, and a well stretched timing chain.
 
I haven't watched the timing advance with the advance disconnected, but will try that. Vacuum readings did not change with the distributor line disconnected. I don't like the poor fit of the rotor on top of the distributor shaft, but would assume that centrifugal force would keep it in the same position while the engine is running.
 
Some vapor is normal at idle from your road draft tube. The reason you don't see it on newer engines is because they eat it. Its fed into the intake through the PCV. A modern PCV is easy to put on your engine after you are satisfied with its running.
Pertronix adjustment; the instructions on mine said the pickup coil should be set at .020 with a non magnetic feeler. I messed around the shop looking at stuff and settled on a double thickness of the clear plastic from a bubble wrapped part. Check NAPA to see about a new rotor and clip. New spark plugs are called for with your problems. I have the best luck with NGK brand, gapped about .030 to .035.
To free up stuck rings, add a quart of ATF and go for a fifty mile ride and back at highway speeds. Change oil and filter to anything with 40 or higher as part of the number.
 
Nice looking car and it sounds great. What are you running as far as mufflers?

Here is a vacuum gauge chart for you.

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Thanks. I haven't gotten as far as investigating what kind of mufflers are on it, but I do know that at least one of them is leaking...lol.
 
I think that Mac's ford parts in Lockport NY. has that small dist. shaft clip. I just replaced my rotor and couldn't find one with the little button on the top contact tab like the original rotor had. My flat spot on my rotor was worn where it fits on the dist. shaft. A new rotor helped. Maybe you could borrow another good carb to see if the carb is your problem.
 
Two things pop out of that movie, it idles like it has a fairly wild cam, that may be its best idle. Two; if you have adjusted the rockers, you may have worn rockers and will never get them quiet. Some machine shops may not know about refacing the rockers. There are movies on youtube showing how its done. One Y blocker I know made his own fixture to do his at home.
Another thought, the rocker clearance is written in the book as .019. My after market cam company says they can be looser, to mellow out the engine, or tighter, to add dwell duration and lift. It can go all the way from .012 on the tight side to .028 on the loose side.
 
I agree with Sal, in that you probably have a carb issue. Apparently these carbs are fine if they are set up by someone that knows what they are doing, and I believe that Sal does. You also my want to check for a manifold to head leak, or carb to intake leak to explain the low vacuum reading. Bruce.
 
Ole Don said:
Two things pop out of that movie, it idles like it has a fairly wild cam, that may be its best idle. Two; if you have adjusted the rockers, you may have worn rockers and will never get them quiet. Some machine shops may not know about refacing the rockers. There are movies on youtube showing how its done. One Y blocker I know made his own fixture to do his at home.
Another thought, the rocker clearance is written in the book as .019. My after market cam company says they can be looser, to mellow out the engine, or tighter, to add dwell duration and lift. It can go all the way from .012 on the tight side to .028 on the loose side.
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I agree with Ole Don in that the exhaust sounds like it has a fairly stiff camshaft in it. That doesn't sound like a rough idle from not running good. It sounds like it's from cam overlap. If that is the case, it would explain the lower vacuum. More overlap will reduce manifold vacuum. However, if the engine actually runs rough or performs poorly, it could be other issues like the carb.
 
Well, tore off the front end and didn't find what i was hoping to find. The timing is oriented as it should be, so I guess that means it's the rings. I had been contemplating pulling the engine anyway to repair leaks and freshen up the restoration, so why it's out why not freshen up the engine so that I know what I have.

2b9c1073-63d2-432b-b248-388a.jpg
 
Rings in relationship to compression?

My thoughts are: Fix the carb, adjust the valves or have your heads rebuild ( fluttering vacuum reading suggest valve guides or valves) i would do this before going for the rings. And if it turns out to need a full rebuild you will have a good carb and heads ready to bolt on.

Just a thought.
 
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