New rebuild leaking fuel

[Stitch]

Sorry this is kind of long.

This was my first time ever rebuilding a carb.  Got Cliff's book to get me started in getting the right knowledge.  I learned a lot, but I still made some rookie mistakes.  I used Cliffs kit so I knew I had the best parts, therefore all errors are on me.

The quad is a 4MV, I think.  It's a 1970 CA model, that's about all I know off top of my head.  It's sitting on a 350.  I finished the rebuild, which wasn't as bad as people make it out to be, but maybe it wasn't so bad because I didn't do so good a job.  I put idle mixture screws out 4 turns, and tried it.  I didn't expect it to work, but it fired right up.  However, I noticed after a short time, the gasket between the bowl and the throttle body was leaking fuel.  It wasn't dripping, but it was wet right at the rear passenger side corner under the secondary bore.  All I had done was start the engine, adjusted the fast idle a bit, revved it a little, got it warm enough for the choke to pull off and then revved a little bit more to look for leaks, which I was hoping not to see.  At this point, I was thinking maybe I didn't get the throttle body screwed onto the bowl tight enough.  I thought maybe it was leaky well plugs somehow getting fuel back there, but looking at it now, that doesn't seem like where the fuel would go if the plugs were leaking that badly.  And I did do the soap test twice to be sure they were good.  Then, I saw the gasket between the air horn and bowl was also getting wet front driver side, right in front of the accelerator pump.

Called in to Cliff's yesterday when this happened, left a message.  Impatiently, called again today but got voicemail.  Okay, I'm on my own until I hear back.  Not complaining, Ray was really patient and helpful with me when I called in yesterday morning. I'm sure they are busy over there, so I thought I'd post here while I wait.  So I just pulled the carb off and started taking it apart. 

Throttle body screws were snug enough, I think.  The diagram shows 3 screws, my model only has 2.  I read around that people use loctite on these, maybe I'll do that next time around if anyone here recommends it.  Throttle body appears very flat, as does the bottom of the bowl.  Although, when I put them together, I do see the side have a little light showing, like the bowl can sort of rock on the throttle body side to side a little, making that gap where fuel was coming out.  But a straight edge shows nothing out of flat and I think when it was together, everything looked really snug.

Moving on to the leak between air horn and bowl.  Major rookie mistake I made was to not check the parts before assembling them.  Just looking at the air horn, I can see its warped with my eyes.  A straight edge shows it even more clearly.  The front corners of the air horn where the long manifold bolts go are clearly bent downward from overtightening.  Now, I got it pretty tight, but I just checked a spare air horn I got from the previous owner of my truck, and the spare is bent the same way.  So I am assuming this one was already bent, but maybe I made it worse, because I don't recall a leak there before the rebuild.  However, the little ridges seemed to make a good impression on the gasket.  Just looking at the gasket, it looks like there was a good seal.

[Stitch]

It's so long I had to split it....

Finally, just right now while I was typing this, I flipped the throttle body over and out fell a little stud.  It was the stud that locks it into place on the bowl.  It only had one to begin with, didn't even realize there was supposed to be two because the other one was already broken off cleanly.  Seeing as I had one stud in the right place and everything assembled well, I don't think there was any way the parts were out of alignment.  But could that missing stud have caused that leak?  Now that the other one is broken off, can I still use the bowl?  I've got spares, but they're not the same models.

So now I am wondering what to do.  Should I try heating and gently bending the air horn back to straight?  Could the front drivers side air horn bolt have been tight enough that it made a gap on the opposite, rear right corner of the bowl/throttle body?  Or is it something else entirely?  I tried calling in to Cliff's one more time this afternoon to see about maybe just sending it in to have them fix it, but I really don't want to wait that long, and I really don't want to be defeated after I got this far doing it myself.  Last question, if I just rebuilt the carb yesterday and only had it together for about 24 hours, can I reuse my gaskets if I figure this out?

Again, sorry for the long post, but I wanted to provide as much information as possible.

[Stitch]

Just wanted to add:
float height is 5/16".  My untrained eye thought there was more fuel in there than what I expected to see.  I have not checked fuel pressure, maybe I'll try and do that next while I wait for a response.

[429bbf]

if you use your hold down bolts for alinement you can get it straight without the tabs . if the air horn is not bent to bad you can use a thicker gasket which i believe comes in the kit ,or you can file down the high spots and give her a try . don't over torque the bolts the hold it to the manifold thats what causes most of the problems in the first place .appox 20 lbs max.check fuel press and make sure you didn't hook the needle in one of the holes on the float.you may also try lowering your float a tad .i know 5/16 is not much ,and a lot are set apox.1/4 . patience is the name of the game and fuel pressure is the key. hth

[Stitch]

Thanks so much for the reply, it's nice to have some advice!

Ok, good to hear the alignment isn't that big of a deal.  I wasn't sure if there was anything critical that needs to be just right. I was considering drilling the old spots and trying to fit new studs in there, but I'll leave that be for now.

I probably put more than 20 lbs on the bolts, but I don't think I went too crazy.  Maybe, I'll grab a torque wrench to be sure I don't go too tight.

On the air horn, I hadn't considered removing metal as an option, I was thinking only about moving metal.  But I can see how it could go bad in a hurry trying to bend this stuff.  I'd hate to mess it up either way, so I will consider both options.  I did not get any more gaskets in my kit, just the one. 

This carb has been on this truck for who knows how long, maybe 30 years.  Before the previous owner got old and sick, he knew what he was doing.  He neglected the truck when he got older, but I think he maintained it very well prior to that.  I'm pretty sure the last time he opened the carb to adjust anything or installed a fuel pump, he knew what he was doing.  So I trust the fuel pump is probably right, but I'll check it.  I don't have the tools to do it and the fuel line is all metal with a compression fitting, so I'm not sure how to test it yet. 

The only leak I knew about on this quad was from the primary shaft, which is why I installed the bushings.  But now that I look at the photos of it before I cleaned it, it looks like these areas probably were leaking and maybe just got gummed up and sealed themselves from filth.  I don't even know if that's possible, but you can see what I mean in these pics. 

[Cliff Ruggles]

I see a few problems in the pics, hopefully they were corrected when you rebuilt it.

The vacuum source to the distributor in the front of the carb is plugged.  I'm assuming someone moved it to the side of the carb or the wrong source elsewhere.

The link from the pull-off to the secondary air flap shaft is backwards.

About all that needs to happen here is the airhorn very gently flattened so it can re-conform to the main casting.

If you bought an SR kit it comes with the .015" thicker MB to AH gaskets.  If it leaks with that gasket in place then the parts have a very poor fit to each other, or your fuel level is way too high in the bowl.......Cliff

[Stitch]

Cliff,
Thanks for the response here.  You sent me an SR kit, my AH gasket is 0.050".  The bowl to throttle body gasket is 0.115".  I see gaps in some areas of the bowl to air horn in the neighborhood of 1-1.5mm at the most.  I'm guessing I need to heat it up, any tips on that so I don't either crack it or melt it?  If I can straighten it a bit, can I reuse the gaskets, or should I order a new set?

The distributor is plugged right behind the choke.  You can see the hose in the second picture I posted in the last post.  This is how it was when I got the truck, so I assumed it was right.  Now that you brought this up, I'm looking at that hole, it's not even a vacuum port, is it?  It's supposed to have a post there, but I have a hole.  I'm posting a picture below.  So do I need to plug this hole now?  There is nothing coming through the bracket there, it is a hollow post cut off right behind that bracket. 

Thanks for pointing out the backward linkage.  I didn't catch that, so I probably did put it back on backward again.  I'll be sure to put it on right this time.

Since you're here, I have two more questions.  The choke pull off I got has a slight bend in it where my old broken one didn't.  I'm not sure which is correct, can you look at the photo below and let me know if this is ok?  If I need to bend it straight, I can try.  If I need a new one, I'll buy one from you because I cracked the plastic flange installing it anyway and I probably should replace it. 

The other thing is my meters and jets.  This thing seems to be set up pretty rich and I'm not sure it's right.  It looks like my secondary bores were wet, not sure if that's why I was getting gas on the gasket.  Never having ran a carb before, I don't know how wet it is supposed to get inside the secondaries.  But my secondary rods measure 0.055".  Primary jets aren't stamped, but I think they are about 77 and the meters are 24.  Not sure if that is ideal or not.  Seems rich if I had to guess, but I really don't know what I'm talking about.  The vehicle is a 60's land cruiser, 4-spd, 350 swap, geared low for off-road. 

[Cliff Ruggles]

The correct vacuum source to the distributor for that engine is from the ported source in front of the carbs main casting not the manifold source on the choke side.  That port was typically used to provide the air cleaner with vacuum instead.

The arm on the pull-off is adjustable to unload the choke angle at start up.  So no worries bending it if/as needed.

I would replace the jets and metering rods with the correct items.  The factory parts were well marked, so not sure what might be in there if you can't find letters/numbers on them.

A successful job starts with getting a good fit between the parts so you aren't leaking air and spilling out fuel where it isn't supposed to be.........Cliff

[Stitch]

Cliff,

Just to update for any others reading this.  I'm sending it in to Cliff to have the airhorn checked out and repaired however he thinks necessary.

I think I did a pretty good job on everything else given that this was my first time rebuilding a carb.  Now that my work will be in the master's hands, I'm anxious to see if he finds any problems with my rebuild. 

I also wanted to add that I was skimming through the book and just happened to see that there was a tip about the dowel pins breaking off on the main body like mine did.  I didn't remember this tip until I read back through and saw it applied to me now.  But for anyone else reading this, page 81 tells you how to line up the body properly without the dowel pins.  Thanks to Cliff for that one!