For those of you that didn't see my last thread. I got my truck running this weekend. Saturday it idled great most of the afternoon as I kept an eye on the vitals. Sunday as I went to fill the tranny to get it to move, it suddenly died and didn't want to restart without spewing loads of gas from the top of the carb. I suspected a stuck float and swapped out the carb tonight. Well, it still doesn't want to idle very well. I can hear air sucking like a vacuum leak, but it isn't a whistle; it's sucking a lot of air. I tried using propane to determine if it was leaking around the carb or intake and saw no change in idle. I used a length of tubing up to my ear and hear it strongest when I put the other end down inside the front two barrels of the carb, where the choke is. If I completely cover the front of the carb with my hand, it will smooth out and idle great. As soon as I uncover my hand, it starts loping really bad and eventually will die if I don't goose it a little. So my thinking would lean towards a partially plugged filter, but the lines are all new, the filter is new, and the plastic can I am running the engine from is new as well. I also, havn't noticed anything in the filter. Would a partially plugged filter do this?
I doubt that a fuel filter would cause those symptoms. It sounds like an air/fuel mixture problem to me. Covering the front half of the carb makes up for a lean mixture like choking the engine. It sounds kind of like the old carb may have had internal problems. It sounds like this carb could have problems as well. A "known good" carb would really help in this situation. The carb could have vacuum leaks especially at the base gasket or even around the throttle shaft(s). IF you could find a "known good" carb you could determine whether the problem were in the carburetor or a vacuum leak (or other problem) somewhere else with your engine. Can you adjust the idle mixture of this carb to richen it up some and get it to run??? Jay
Those are not set to run out of the box. I dont care if it says it is. Turn in the mixture screws all the way then start at 1 full turn, and adjust out at 1/4 turn intervals from one to the other. Usually 1 1/2 - 2 1/4 turns on each side is good.
Occasionally, you may experience a vacuum leak into the intake ports from the crankcase of the motor due to the intake manifold / cylinder head interface not being machined parallel. Here, I'm talking about looking at the manifold from an end view, from the front or rear of the car for instance. Unless you're using all brand new parts, you have no way of knowing if the heads or manifold have been machined by the previous owner, so the interface at the manifold/head could be out of parallel. In other words, the gasket might be pinched tightly at the top of the port and sealing fine, but might be wide open to the crankcase at the bottom of the port, allowing oily vapors to be drawn into the intake manifold runner on the intake stroke. The manifold may also be warped a little. No amount of propane or carburetor cleaner will find such a leak. The best way is to insure the elimination of such a problem while building the motor. Here's how I set up the intake manifold/cylinder head interface to prevent vacuum leaks from the crankcase to the head ports....Begin with the heads properly torqued to the block for the final time and ready to go. Measure the thickness of your new intake manifold gaskets. Get flat washers or shims that will measure that thickness. With the manifold off and the mating surface on the cylinder heads de-greased, put a dab of RTV on the washers/shims and stick them on each corner bolt hole on the cylinder heads. Let the RTV set up. Stuff paper towels into the ports to keep debris out. Make up 16 pea-sized balls of modeling clay. (Use oil-based modeling clay from a craft store, not Play-Doh). De-grease the intake manifold at the ports. Place the balls of clay on the top and bottom of each port of the manifold, squishing them down well so they stay in place. You want them to be thicker than the shims/washers that are RTV'd to the heads. With your fingers, coat a little oil on the heads where the clay will meet the heads to keep it from sticking to the heads. Now carefully place the manifold into place on the heads and use bolts on the four corners to just snug the manifold down until you feel resistance against the shims/washers. Remove the manifold carefully. Cut half the clay away at each position with your pocket knife. Measure the thickness of the remaining clay at all 16 positions with the depth function end of your 6" dial caliper. You'll know pretty quickly if the manifold/head interface is square. Record the measurements on the manifold with a permanent marker like a Sharpie. The widest measurement will be the standard to which you will want your machinist to cut the other positions on the manifold to make it square with the heads, thusly sealing up the motor. Pay particular attention to interference at the bottom of the manifold at the block rails front and rear. If you cut the manifold, you'll be dropping it down a little into the valley, so PAY ATTENTION. Also, with the manifold down a little in relation to the head ports, the ports may not line up exactly. On a street motor, I wouldn't be overly concerned about it because the laws of fluid flow dictate that the majority of the flow is right down the middle of the port and the surfaces of the port wall will be relatively slow moving. If you want to be dead-nuts on your build though, you should port match to the gasket. Also, using two gaskets on each side may line things up better without any need to grind on the ports. If the motor has been in operation and you suspect that the ports are being fed from the crankcase, remove the intake manifold and very closely inspect the gaskets for being "pinched" all the way around the ports. You may find that either the heads or the manifold has been cut by someone else before you got them and now one or the other is out of square to the other. I have seen this before, where the top of the gasket is pinched but the bottom of it is not pinched at all.
The engine was in a different truck that I drove for a year before swapping into the 58. I didn't take it apart, just checked the compression, leak down, new oil pan gasket, valve covers and gaskets, and into my truck. It was running great with a 600 Holley and then started acting up, so I put this Edelbrock on that I had bought last summer for a chevy that I wound up selling. I'll try the mixture adjustment tip.
I did this once with an old Yamaha I had. But not with a truck. Do I just turn them in and then back out until it is idling smooth? Or, is there some kind of vacuum gauge that I should use?
What kind of engine? How did you set up the timing for the initial start? If you shot the timing after the initial startup was the vacuum advance line disconnected? Get a vacuum gauge on the engine and see what it reads at idle and 1200-1500 rpm. Along with this, what altitude do you live at? Was the first carb a Carter/ Edelbrock or Holley? What kind of intake gaskets are you running? Shim stock steel or paper/fiber? I've had more than a few probs with the steel intake gaskets on my 455 series Buick engine. Gave up and I make my own now - it ain't difficult. Could you be experiencing signs of a high float - smelling gas or seeing gas leaking from the carb? It does look like an overly lean condition to an extent, but my bet is too much fuel pressure. We just went through virtually the same thing on my pal's 46 Ford with 302 SBF that runs a 600 cfm Edelbrock. It got stuck about 10 miles out of town during last weekends three day Fun Run. He went home and got his trailer - I found his car after he'd left in another guys roadster. Helped him load up, he took off for his house, I went to mine and got a virtually new 750 Edelbrock carb that is a known good carb and properly set up. We had the carbs swapped in about 20 minutes, cleaned up and took off for the car show segment of the run. The car ran great, but my thinking is he has high fuel pressure - Carter/Edelbrocks run their best at 4 1/2 - 5# pressure. I suggested we stick a regulator in the fuel line, but he doesn't want to. His reasoning is, the fuel pump is stock mechanical so there shouldn't be a high pressure problem. If I remember right the little Fords put out 5-7# fuel pressure. So that's where we're at now. And I'm waiting for the phone to ring and having him tell me my carb is leaking fuel out the top....
Ford 351W mildy built I haven't gotten that far yet. When I first fired it Saturday, it was running great. Throttle response was quick while in park with no load, and idle was very smooth. Just like when in the other truck. I live in Rockford, Illinois. Elevation 715 ft Holley Paper The Holley suddenly started flowing out of the top of the carb on Sunday after idling fine for ten minutes. I rapped on the float bowl with a screwdriver and the stopped coming out of the top of the carb. After that, it would barely idle, if I goosed it, it would sound great. Exactly like the Edelbrock is doing now. I will look into it. Thanks I am a little curious as to why the Holley would suddenly develop problems that seem to have crossed over to the Edelbrock in regards to idle. I am going to swap out the filter tonight. It can't hurt.
You're getting excess fuel which indicates the filter is flowing ok. Holley's seem to handle a slightly high pressure better than Edelbrocks, but not always. In my opinion, high pressure is the culprit here. Get a Holley dead-head style regulator and install that. One quick test is to set up a gravity fed fuel supply. If the flooding problem stops with the very minimal pressure you'll know where you're at. Be careful with gas, helluva fire hazard as you know so don't just Mickey Mouse the temporary supply setup. A simple test you can do is, pull the fuel line off a full float bowls carb, block the line so it's not pumping gas, fire the engine and see how the idle goes. It will idle quite a while on the fuel in the float bowls. If no probs, you have high fuel pressure. You can accomplish the same if you have an electric fuel pump by just shutting it off. My pal, noted above, took off a Holley 600 cfm double pumper a few months back and installed the Edelbrock 600. Things were great until the rod run. His wife did comment she'd been smelling gas the last couple of times they were out. Reason I asked about altitude is, vacuum levels on a good running mildly cammed engine will show 15-16" at 3300' and the same engine shows 18-18.5" at sea level. Got a pal with a pressure gauge? They don't cost too much, you need to check your fuel pump pressure. If you do a search for Edelbrock carbs and fuel pressure you'll find quite a few posts pertaining to high pressure.
That may be the case, I do really appreciate your help. I will look into it, but it really seems like I'm getting excess air at idle not fuel. There is a very loud whooshing of air that sounds like a huge vacuum leak. When I completely choke the carb it runs a lot better. I might be wrong, but if it was getting too much gas, wouldn't choking the carb make it run worse? I drove with this engine in the other truck with the same pump and Holley carb for over a year. It was running great on Saturday. It was running great at first on Sunday. It suddenly started getting too much fuel which I attribute to a stuck float. I rapped on the float bowl and it stopped flooding through the carb, but then all of a sudden had this poor idle problem for the rest of the evening. Tuesday night, I swapped carbs and have a very similar poor idle. The carb changed, but the condition didn't. I'm not trying to argue, I will check it out per your instructions, I'm just curious if there might be something else causing the problem. I don't want to be chasing my tail on this anymore than I have already. Is it possible that some crap might have been in the pump and got into the filter? Maybe a little of it got through the filter and lodged in the needle in the Holley. After I cleared the gunk from the needle by rapping on the bown, the remaining gunk was still partially plugging the filter causing the poor idle. I swapped carbs, but the filter is still partially plugged so the new carb exhibits similar poor idle. The new carb is sucking the correct amount of air, but not getting enough fuel at idle, when I rev the engine the volume of fuel increases, the pressure buils and is able to get around the obstruction and it evens out. This is all an uneducated guess. It may not even work like that, and I may sound like a complete idiot. That's why I suggested changing out the filter. I don't want to seem ungrateful for the advise. I see it frequently on here where someone already has an idea of what's wrong and argues with everyone that has a different idea. I'm not doing that. Thanks again, John
Not a problem. The loud 'whoosh' of air you're hearing may be nothing more than air flowing through the carb venturi's at idle. Accentuated a bit with the air cleaner off. Should be a fairly steady sound as well. If you're overflowing fuel somewhere it's either a stuck or drowned (leaks) float, high fuel pressure or grit between needle and seat which will let fuel at any pressure through. When you held your hand over the carb was the engine cold or warm? Make sure to post what you find, that way we all learn.
Edelbrocks only like 4-5 lbs fuel pressure, any more than that and she'll blow by the float. Whooshing sound could be from a leaking carb gasket. I found that one out on my kids s-10 the other day... 2-2.5 turns out on the carb screws, use vacume gauge to get highest reading.. I'da kept the Holley....
It's not the gasket. I want to keep the Holley too and probably will once I can figure out whats going on.
Well, I tried changing the filter and it didn't work, just like you all told me. I tried the gravity feed into the Edelbrock, and it was still idling like crap. I turned the mixture screws in, and they were only a turn and a half out to begin with. It made no difference in performance. I finally pulled it off and put the Holley back on, which kinda sucks, cause I bought the Edelbrock last summer and plans changed, so I never even ran it. With the Holley on, it will now idle really well for a minute or so, then start dropping, run like crap for a minute or so, while blowing black smoke, and then die. I'm no longer getting fuel out of the top of the carb. I am going to get a kit for it and see if a rebuild won't take care of this.
I don't think a rebuild kit will do much for you right now. Two carbs with the same basic problem indicate a non-carb problem. My pal, who was having the same symptoms in his 600 cfm Edelbrock - noted above - turned out to have right at 5# fuel pressure so that was ok. (Shot my high pressure theory all to heck and gone.) And, my 750 Edelbrock is still running fine on his engine - 302 Ford. What he did find was that one of the floats had sunk. When he - and the guy who rebuilt it - opened up the carb, one of the floats was heavy and fuel was sloshing around inside he float. I think he could have drained the fuel out and re-soldered the seam, but he elected to buy some new floats at NAPA. About $16. for everything. First thing they noticed about the problem was that the car smelled like gas when running. When they took off for the first day in the rod run, it started running bad and when he slowed down to turn back, the engine died. While the car sat, the gas apparently evaporated and the engine started and ran good enough to get it up on the trailer. Pulling the carb top on the Carter/Edelbrocks is easy, but as noted, the same problem with two carbs notes an external problem in most cases. Do you have a fuel pressure test gauge? You can make one up easily if you have an air gauge or old welding low pressure gauge. Something with about a zero to 30 psi scale so you can tell the difference between 5# and 7# or so. You can also find fuel pressure gauges for not much $$ at NAPA and the like. Dumb as it sounds, do you have a third carb you could try? Some Holleys run nitrocellulouse floats - looks like a hard black foam - and with today's gasoline they will eventually sink. I hear that today's Edelbrock's are coming through with mis-adjusted floats. Even so, I have four of them and the floats were right on. So it's possible you have the same basic problem in both carbs. Goes against what I said above about it being uncommon to have the same problem with two components, but it's entirely within the realm of possibility.
They are similar conditions, but not exactly the same. The Edelbrock only runs choked I haven't noticed any black smoke and haven't smelled and gas, the Holley runs really well, and then acts like you were right about the pressure. After a short while of idling fine, it slowly starts running poorer and poorer until it finally dies. As the idle deteriorates, it starts blowing black smoke from the exhaust, but I haven't noticed a gas smell with the Holley either. I don't have a pressure gage, or a regulator, and right now money's too tight to buy them and have it not be the problem. If I knew that would fix it, I could justify spending the cash. I may look and see if Autozone or onr of the other parts stores rents a pressure gage and go from there. The problem with the Edelbrock is I bought it last summer and ran it once on a small block chevy. I ran really well, then I sold the engine for, but kept the carb to use on this engine. I'm afraid that I might have left some gas in the bowl and it has fouled things up.
The idle getting worse and then black smoke tells me one thing. A needle/seat issue ,either a bad float or more likely some dirt of some kind on the needle's seat area keeping it from shutting off compleatly.
Cool thanks, I do have one question that comes from inexperience. Which gasket goes between the carb and the spacer? The carb is a Holley 80457-2. I believe it is called a square bore. It has four equal sized ports on the bottom that arre positioned in a square. There are reliefs connecting some of these ports, and something right in the center of the four ports. I'm not sure what it is, maybe something to do with idle? I have two different gaskets, one has one big square hole in the middle that kind of matches the square hole in the intake, but the hole in the intake is split right down the center, I assume this is a dual plenum intake. The other gasket, has four holes that kinda match the Holley, but the Holley has the small relief in the middle that seems like it would be restricted by the gasket with the four holes in it. Man, I really need to get a Holley book and bruch up on the terminology. Hopefully those of you with experience understand what I'm saying.
Ok. When points ignition rubbing blocks wear down quite a ways - or are adjusted barely open - the engine will exhibit symptoms similar to what you're having. They can fool you . . . it did me. I ended up buying a new carb for my 61 Ford quite a few years back, the car ran the same (bad) and all it took to get it squared away was to adjust the points properly.
I've got a similar problem to this post and looking for more ideas. SBC, brand new Holley 4 barrel. Mechanical fuel pump For the first 500 miles this car cruised just perfectly. Suddenly it has intermittent problems and won't hold an idle. I tweaked the air fuel mixtures last night, adjusted the floats on the secondaries since they seemed to be leaking gas into the throat even at idle. Took her out for 20 miles and it ran fine. Idled at stop lights with no problem. Plenty of response. Nice and smooth while cruising. Idle in park was set at 800 Idle in gear was set at 600 It was all good. Tonight, no changes to the car and went for a ride and she won't idle at all. As long as I'm in the gas peddle it'll run, but even cruising at 35 mph or so if I come off the gas it dies. She's acting like it's starving for gas. Won't even idle in park now. One symptom I wanted to ask in that vein is in the fuel filter. I put a brand new, clear glass one on it. While running the filter is almost full, but not quite full. After sitting for 30 minutes, the glass filter is almost empty. Could this be a sign of something in going on in the fuel lines that might be causing an intermittent starving situation? Any other ideas, tests?
The problem is only in the idle circuit, that's why it runs great when you give it gas. Take out the two idle screws, spray some carb cleaner in the holes, use the tube, don't be stingy. Screw the screws back to where they're 2 turns out and enjoy the rest of your day
The Jalopy Journal
