I hope I'm posting this in the right forum, please move it if I have it in the wrong place. I just picked up a '55 Thunderbird that was restored a few years back, but has been sitting for the last year or so. Once I got it started, there was a pretty healthy gasoline leak from the pump, no doubt caused by the upstream electric pump. With the electric fuel pump disconnected and a new stock pump in place, it's running again, but it doesn't idle well. New plugs to replace the fouled ones didn't help a lot. I connected a vacuum gauge and it is between 10 and 11 inches hg, which seems awfully low. The timing seems to be advanced well beyond the 6 or 8 degrees that it should be, but retarding it makes it worse. When you rev it, it seems smooth and as powerful as you would expect, with vacuum in the 22-24 range. The previous owner kept receipts of all the work that had been done, and it looks like a couple shops have tried to resolve similar issues with it. There has been a valve job with the heads resurfaced, new intake gaskets, carb overhaul, Pertronix ignition, etc. Compression is a little low, but consistent at 105 psi or so. The valves were set a little loose, so I reset them at .020 but that seemed to make the vacuum drop an inch or so. There is zero blow-by and no evidence of oil on the plugs, so I think that the rings are good. Finally, sometimes it will idle as long as you like at 7-800 RPMs and is almost acceptable. Other times, one of the secondary barrels fills with fuel, eventually killing it by flooding. It has the original Holley 4000 teapot carb, which I have no experience with. Anyway, it strikes me as having a vacuum problem that no one has been able to find as well as a carburetor issue. This is my first Y block, but I wouldn't think that it would be much different than diagnosing any other engine. That said, it's kicking my **** and I'm having to reach out to the experts. Any help is appreciated. Thanks, Bobby
The teapot Hollys have the float bowl on top of the carb and are notorious for leaking fuel into the secondary throats. You'll find a large br*** screw right above the secondary opening, make sure this isn't leaking. Use a new gasket, and get this as tight as possible. I've had to use a large, square-shanked screwdriver and use a wrench on the shank to get these tight enough to not leak. Also check your vacuum advance; make sure both diaphragms are good and connected correctly. These as built don't have mechanical advance, instead use the dual diaphragms to advance/retard timing. The carb/ignition design on these left a lot to be desired... If originality isn't important, swap to a '57-up Y-block distributor and intake with a later small Holley. Much less troublesome which is why Ford abandoned the early version. The later distributor design also uses the 'standard' '57-74 Ford points/rotor/cap which are easier to find.
When the gasoline leaks into the secondary bore, it's actually coming out of the nozzle at the top of the bore. Is that a vent?
It's been a long time, but no, that's not a vent if I recall right; that's where fuel goes into the secondaries. I'd really suspect that screw, as the fuel can 'wick' down and be hard to tell just exactly where it's coming from. I chased this on the one I had for months before finally figuring out it was that screw. Sometimes it would leak, sometimes not, but once I got that screw sealed my problems went away...
Thanks for the Steve. I'm experimenting with things, and it looks like when the secondary ****erflies open that's when it fills with fuel and kills the car. I don't know if this is because of the vacuum issue or not. I just took it for a four mile ride at about 50 mph and it's missing at all RPMs. Placing it in 'Drive' knocks the RPMs from about 800 to 450 or so, barely enough to keep it running. I pulled the valve covers back off to make sure that all the rockers were moving as they should, and that looks good, but I haven't gone as far as doing any measuring. Also, there's a receipt for pulling the timing cover to check the timing chain, so I ****ume* that is good. Still checking and looking and appreciate the help.
No, fuel spray comes out of there when the secondaries open. If fuel is coming out of these ports during idle, the bowl is over filling. Check the needle and seat for contamination. The rubber tipped needles seem to be a magnet for debris! If you're running rich at idle, the power valve stem diaphragm may not be holding vacuum and letting the power valve stay open. The primary and secondary shaft bearings do wear out and cause vacuum leaks. But, they are replaceable. Here's a pdf of the Holley 4000 manual: https://app.box.com/s/s2a5ak0r9f2en6auvnvc You may want to just rebuild the thing and not chase little problems. Doing it yourself isn't difficult.
Cam timing may be incorrect. Y blocks are strange in that you time them with the marks out to the right side, not straight up. If I recall correctly, there are 12 pins between the marks. Most chains have different coloured plates where the gear marks go. Also, as stated above, the original advance and carb should be chucked and a '57 or newer setup installed.
Thanks Chris. The fuel only comes out of the br*** nozzle is the secondary ****erflies open. Then gas will continue to run out, with the ignition off, until the carb is empty. Since the last post, I have reran the valves to make sure that they are at .020 and done a compression test. All the cylinders were between 112 and 128. Not high, but I would like to think it's enough to pull more than 9 inches of vacuum. What I keep thinking about is the timing. The marks on the balancer run from TDC to 10 degrees (I think). However, it wants t run at about 2.5 inches past that, which I would estimate about 25-30 degrees. Advancing it from there makes it ping, retarding it to the specified 8 degrees makes it feel very sluggish. When it's at TDC per the balancer, the rotor is pointed right at #1. One of the shops that worked on it pulled the timing cover to verify that timing hadn't jumped. Still, it sure makes me think that the cam is not synced up with the crank like it should be.
I know this sounds funny, but check the plug wires in the cap and make sure they are in the right direction (opposite of SBC). It will run even with the dist cap wired backwards.
The wiring order is correct, per the intake, and they are on the cap counterclockwise. Is that correct?
Sounds like the secondary check balls (under the slotted br*** screws) are not seating correctly or are missing. If these are not working correctly, fuel will continue to flow (siphon) out of the bowl. The br*** screws can be difficult to get out and the slot is easily damaged. Be careful!
I would say the anti siphon vent holes are stopped up. They are located on the top of the carb, just in front of where the two long br*** tubes go into the carb top plate. Easiest way to unplug them is to strip the insulation from a piece of s**** wire and use a single strand. Do NOT use a small drill bit, ice pick or any other hard tool that could enlarge the hole.
Yeah, I forgot about those! Sounds like a thorough scrubbing and rebuild is in order. Would probably solve some of the performance issues.
Clean out your PM box, Bruce! I was going to send you a "what's going on with the scooter" explanation.
I'm still puzzled why the the timing has to be so far advanced for it to run. I had mentioned before that when the previous owner had it in a shop (foreign car shop, don't know how much they know about Y blocks) that they pulled the timing cover to check it. It could be that they were expecting to see the two dots on the gears lined up, which I understand is not correct for a Y block. So it may or may not be right. That said, with the balancer at the TDC mark, both of the rockers on the number 1 are loose, so the lifters must be pretty close to the bottom of the cam lobe. Also, when at the TDC mark, the rotor is pointing to number 1 on the distributor, but I guess that you can stab the distributor in any orientation. I'm going to pull the rocker shafts this morning to make sure that none of the pushrods are bent. They spin freely when relaxed and all the valves look to travel as far as you would expect when the cam turns.
I'm still puzzled why the the timing has to be so far advanced for it to run. I had mentioned before that when the previous owner had it in a shop (foreign car shop, don't know how much they know about Y blocks) that they pulled the timing cover to check it. It could be that they were expecting to see the two dots on the gears lined up, which I understand is not correct for a Y block. So it may or may not be right. That said, with the balancer at the TDC mark, both of the rockers on the number 1 are loose, so the lifters must be pretty close to the bottom of the cam lobe. Also, when at the TDC mark, the rotor is pointing to number 1 on the distributor, but I guess that you can stab the distributor in any orientation. I'm going to pull the rocker shafts this morning to make sure that none of the pushrods are bent. They spin freely when relaxed and all the valves look to travel as far as you would expect when the cam turns.
<HR style="COLOR: #e5e5e5; BACKGROUND-COLOR: #e5e5e5" SIZE=1> <!-- / icon and ***le --><!-- message --> 'Cam timing may be incorrect. Y blocks are strange in that you time them with the marks out to the right side, not straight up. If I recall correctly, there are 12 pins between the marks. Most chains have different coloured plates where the gear marks go'. One of the first engines I rebuilt when I was a kid (15 years old) was a Y block. I read up on the timing marks but unfortunately when I ***embled the engine I had it upside down on a workbench...Yup I installed the chain on the 'wrong side of the engine'. Amazingly it started and ran (kind of) and when I took it apart I hadn't bent any valves or damaged anything other than my ego...sorry I can't offer any advice other than to check those links between the marks on the gears.
If you decide to do something with the carb (they are actually a very good carb when set up properly), go to the Yblocksforever site :http://www.y-blocksforever.com/. There is a gentleman named Mike Sutar that works on these and posts on that site. He can fix that thing. Hope this helps you
Update: Pulled the rocker shafts and ensured that all of the pushrods are straight. Reset valve lash at .019" with everything cold. Started back up and valves were quieter, but vacuum now in the 7-8 range. The previous shop had it set at .035", maybe in an effort to increase the vacuum, not sure. Anyway, it still has the same miss. I did notice that the rotor had a ton of play (the shaft itself seemed fine), so I will see if I can find another rotor that fits better. I did make a discovery that will hopefully lead to a solution. I scanned all of the inlet ports on the exhaust manifolds and realized that there's a problem with #5 & 6 cylinders. The other six cylinders were between 400 & 425 degrees, while #5 was about 190 and #6 was 285. Both cylinders were getting good spark and the plugs were not fouled when I pulled them yesterday. Compression of both cylinders were in the same range as all the others, so I think the issue is that that corner of the engine is not getting enough fuel for combustion to occur. That has to point to either a carb or intake issue, I would think, but would sure like some other opinions. Thanks again for all of the advice.
Did a test for vacuum leaks this afternoon with a homemade smoke machine, but didn't see anything leaking. I'm going to pull that valve cover again and watch the rocker movement on #5 closely.
OK, the issue on 5& 6 is solved. I seemed to swap those two plug wires when i re***embled 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.
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 ***embler 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
Might be a good idea to pull the timing cover yourself. It's possible the wrong gear got installed , or the locator is damaged somehow. I had an AMC engine that had an issue with the distributor timing having to be advanced , and the final fix was the dowel pin in the camshaft was sheared , allowing the camshaft gear to be off. It does seem like you have two problems , but your fuel in the secondary's may be caused by the vacuum problem , or having to turn the idle screw up so high to keep it running. It doesn't seem like you have a compression problem. If you have over a 100 in each cylinder and they are within 15 lbs , you should have a smooth running engine. Vapors from the road draft tube are normal , that's it's purpose. Vapors out of the oil fill breather , while it's running , indicates some blow by. One other possibility is the distributor may have a problem with the gear being installed wrong. Very unlikely. A vacuum reading on the engine should be 18 inches or 22 ideal. I ran into many 144 and 170 cu in Ford engines that would only run with the timing way advanced. A fresh timing chain always fixed the problem. Good luck.
Thanks Lostmind. I have zero blow-by visible at the breather cap when I pull it. I don't see any signs of oil dripping from the road draft tube, just a lot of vapor. While I think the carb has some issues, I don't think that it is THE issue. After the wet and dry compression tests, I will be moving to the front cover and see what I can learn.
If you can't figure it out PM me and we can chat about what's going on. You seem to have a timing issue maybe both ignition and valve.
Timing gear installation. Some people try to align the timing marks on the gears toward each other as is common on newer engines. This is bound to happen more often now as the replacement timing chains no longer have the pins marked for correct alignment with the gears. The marks on the Y-Block timing gears aim toward the oil filter side with 12 pins between them.
Thanks, that's exactly what I'm thinking (and hoping) is the problem. As I mentioned before, another shop had checked the chain to see if it was the culprit for the low vacuum and compression. They likely expected to see the marks lined up at 6 & 12, as would have I. My only experience building engines is Windsor and FE engines, and have seen enough SBCs put together to know that is how they are aligned. The rotor is pointed towards #1 when the crank is at TDC, but I guess that's how anyone would stab it no matter where the cam was. Hopefully I will have enough energy when I get home to go as far as getting the front cover off. One of the lessons for me is to look at the manual for more than torque values when I ***emble my 8BA!
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