The kits only come with the thin ones.
You can get a 2nd thin gasket and use 1 top & bottom.
You can also get that thick gasket from a parts store, may have to order it.
Dave ----

 

You will have to buy the thick gasket separately from the store. They can order it for you, make sure you get one if your old one is in bad shape, do not try to use the thin one.

On the idle screw settings, you can start them at the same position, but after you get it running, how the engine runs determines their final setting. They should be close, but not necessarily the same. If the engine runs it's best with one screw way off from the other, then be suspicous that there is a vacuum hose that was accidentally left off, they are easy to miss when they are located way underneath the carb body.

 

thanks Daves! the kit gaskets were thicker and had plastic grommets at the bolt holes, I was overly concerned about the difference; everything fit just fine, maybe be a quarter of an inch higher at most, one hose was at maximum reach but fit. So I put some fuel down the vent pipe and double checked all the hoses, attached a fresh battery and fired it up! 1st time vroom! ack! 2nd time totally normal running nice... but wouldn't idle until it warmed up, it was running so well I drove to the gas station, then the grocery store, 25-30mph and hoping to stop at all the lights to listen to it idle! hehe Tomorrow I can check the fuel level in the bowls and see about cold idle... can't wait to get some round tires and new shocks on it!

 

I would not leave those idle screws were they are at and not try to adjust them. With it completely warmed up (go to the store again) bring it back home and then make sure it's idling slow were it's supposed to, and then slowly back out one of the screws. If it speeds up great. If it doesn't speed up backing it out, then turn it in and see if it speeds up. If it doesn't, keep turning it in till it slows down, then back it up till it speeds up and run's it's highest rpm. Then go to the other side and do the same, getting the highest rpm. If these screws were way off, then you might need to re-adjust the idle stop screw to slow it down.

Once you go through both screws, go back to the first screw and do it once again, turn it in till it slows, turn it out till it's the fastest, then do the 2nd screw again. You should be good after this.

 

Welcome to the world of carburetors!
I would say you will need to adjust the choke for that cold idle issue.
Might need to be turned on more so it will idle when cold?

Yes adjust the float level before the idle mix screws.
I would do this as soon as the motor is started. If it does not idle because cold do a quick adjust of the choke so it will idle. May need to turn up the idle speed for float adjustment.
Dave ----

 

Once I got access to the idle mixture screws I started with all screws in all the way and then backed out 1 1/2 turns... when I got home after first test it had just a hint of wanting to stall maybe 500-600 rpm (if my other tachs are close to correct my 3.8l v6 and 5.4l v8 say 700 at idle and this is noticeably slower but not barely turning over). Interesting, the factory setting for the secondary idle mixture screws was maybe 1/4 turn from all the way in, with grit/buildup I'ld say one of them was 'all the way in'...

 

This carb has 4 corner idle adjustment? I have heard of some carbs having that but did not know these Ford/Holley carbs did.

 

You had a "two stage" power valve installed. For tuning purposes though, you probably want to start from scratch, with a new baseline. The idea behind a two stage in theory was to provide at least the possibility of slightly better economy when towing. There's a cut and try method to carb tuning, no way around it, you may go through a few of them.

The rebuild kits usually include a single stage 6.5" power valve (economizer); this is a general good choice for a stock motor at Sea level All that means is that the power valve opens (and closes) at 6.5" of vacuum.

Selecting the correct power valve is important, dependent on your particular altitude, engine tune, gearing, camshaft etc. Or more specifically, the manifold vacuum of your particular engine. Do you live over 5000 feet? Or do you travel to high country there regularly? The higher you go in altitude, the average engine manifold vacuum will go down. So the correct power valve number has to go down as well, or it will stay open constantly.

The Shop Manual Specifications for your engine has the listing for the correct power valve #, usually a range of three different sizes depending - 0-5000 feet, 5-10000 feet, and 10000+

The best way I've found is to use the factory stock #, but measure the average manifold vacuum when cruising on level highway with a gauge. For example my old stock Y block pulls 20" at idle. According to Holley, "divide idle vacuum by 2" gives a 10.5" power valve.

But it cruises around 15" manifold vacuum on the highway at 60 iirc, dividing by two here, gives a more accurate choice a 7.5" power valve. And surprise, that just happens to be the factory stock power valve listed in the manual for below 5,000 feet, not a 10.5. If I want to visit the high country for a few weeks - say above 10,000 feet - a 5.5" power valve is spec'd, and will pay for itself in fuel savings real quick. Everybody always asks about jetting for altitude, but the power valve is probably more important.

The idea generally is to have the power valve open whenever extra power is needed of course, but it's just as important that it stay closed when it ain't - the wrong number (too high) will open too early and REALLY waste fuel. A steady headwind for example on the highway will expose the wrong size power valve, and you'll need a fuel truck to follow you around.

If your engine is stock, pulls good manifold vacuum i.e. 18" to 22" at idle, and you live at Sea Level, a 6.5" should be close enough, assuming acceleration is acceptable. I'd still want to use or at least start with whatever # the manual specifies, that will be closer to your final, assuming your engine is stock. The power valve has to be selected properly, or it will make jetting impossible among other things, because it will run pig rich, foul plugs etc.

Also keep in mind ignition timing plays a big role in the average amount of vacuum. Get your ignition timing and distributor curve straight before ever getting down to serious carb tuning. Provide all the info to the guys here helping you out and they'll get you set up for the right power valve.

 

Franklin, it had 4 plugs in the base that needed to be drilled out and under them are 4 valves that can be adjusted in & out of the 2 primary and 2 secondary valves.

Thanks for the detailed comment Tedster, I will have to see how far I can get with this, the truck has 50k and doesn't seem to have had anything done to it other than fluids and a brake job. I have never done timing or carburetors before, owned a Jeep with a carb once but never worked on it... Can I do the vacuum reading with a rental gauge set from the auto parts store?

 

I thought I said how to pick the PV in one of my posts?
Driving and checking the vacuum is the best way and cut that in half, pretty sure that's what I said?

You can use a rental vacuum / pressure gauge from the store but they are cheap enough and can be used for many other things like checking fuel PSI, adjusting the carb and some use it to adjusting timing.
I have had one for ever (late 70's). Last time I used it, 3 years ago, was to check fuel psi on my John Deere garden tractor that has fuel injection.
I had to strap it to the hood wile cutting the grass as the motor would surge then cut off after about an hour or so of cutting.
Come to find out the in tank fuel pump would get hot and start to fail, then psi would drop and cause the surge.
I would have never found this if not for the vacuum / pressure gauge.

Besides we all like more tools in our tool box LOL.
Dave ----

 

No, I didn't mean to step on anybody, this thread has 7 pages on my smartphone, it's just that I didn't read every single post in detail.

I would agree, buy a mechanic's vacuum gauge. There isn't a bigger bang for the buck, in terms of usefulness in engine diagnostics and tuning. Takes the guessing out.

 

Any good brands or especially good kits (have all the fittings I might need for various tests)?

Also, my PV is a 4.5 if it means anything to you guys... I know 'it will when you give us your vacuum readings!' hehe

Plus, the heat shield is in the way of adjusting the secondary idle mixture screws, 'curse you heat shield!!!' I have them set 1 1/2 turns out should I adjust these before I get my PV sorted? I think it means pulling the carb to adjust them.

AND, the cold idle isn't consistent, 1 day wouldn't idle : 1 day idled fine, 1 day idled a little rough, choke or idle mixture screws or ?

 

I personally would not mess with the power valve and all that testing unless you have a driveability problem when it's on the road pulling a hill.

On the 4 corner idle system, I think you should leave the rear screws at the even 1 1/2 turns on each side in the rear, and then just mess with the front ones if they are easy to get to. You may find they are ok where they are at now, but there is always a chance. And also, if the rear ones are a little off, the front ones can compensate a little bit. I would get it good and warmed up and then tweak these front idle screws to see if your iffy idle problem goes away. I have seen idle mixture screws that are adjusted a little too lean act the way you are describing.

 

I adjusted the primary float bowl needle and seat so no steady drip from sight plug, would this effect idle at all? seems to be running a little rougher, no too bad but different and sounds like it might stumble... maybe just dial it back an 1/8th of a turn to test? been enjoying the test drives in this truck even with the tired shocks (had new tires put on this weekend).

 

Yes, absolutely it can. The fuel height in the bowl is fairly critical. This is adjusted or setup by float height. Think of a bucket full of water. A hole at the bottom would send water streaming out farther than a hole at the top would, due to column pressure.

If the fuel level in the bowl is too low it may cause fuel starvation at high speed, if it's too high it may flood. So if the fuel height is raised or lowered it will tend to cause a slightly richer or leaner air fuel ratio at idle, all things being equal. A carburetor has very little airflow through venturi at idle. So an idle circuit utilizes engine manifold vacuum to get the velocity high and atomize the fuel finely. Re-adjust mixture screws anytime something is changed like that, and reset the float height or at least check it, if a fuel line or fuel pump is replaced. If you could only make one carburetor adjustment, fuel height would probably be it.

You can see how precision the idle mixture screws are with a wideband O2 sensor, just a slight turn of the idle mixture screws moves the AFR a whole point. In really hot weather the fuel will boil in the carb and run very rich, too. Some say float height or fuel height changes jetting slightly as well. Not much, but some.