Hello everyone,

I have a 1970 F100 with the 360 engine and the manual 3 speed with granny gear tranny.

I installed a new Holley 2 barrel carb, previous carb, I believe, was the original carb but it was on its last leg.

8 years ago my brother and I did an off frame restoration, truck was completely taken apart to the bare frame and restored. Engine was rebuild to almost stock condition, the only upgrade was the cam. I do not remember the specifics of the new cam, but the idea of the new cam was to give the truck a little more power. Rest of truck is stock, and as far as we know the truck was 100% original when we started the restoration. Unfortunately we could not save the hood and bed so we replaced them with a bed and hood from a 69'.

Don't drive the truck that much only on weekends, so it has less than 5000 miles since the engine was rebuild.

I need some guidance with setting the timing and idle, I got the truck to run, you have to keep giving it gas otherwise it will turn off.

Which do you do first, or is there a procedure somewhere out there that I can follow. Or maybe there is a thread that covers this already.

Any help is appreciated. Thank you.

 

Set timing first because idle will change with timing variation. If it is points distributor, then set the point gap first because the timing will change with the difference in gap (dwell). Set idle to spec after that, I'm guessing around 700 rpm, then set the idle air fuel mixture then reset the idle if it changes with the carb adjustment.

KOT390

 

KOT390 Thanks for the response and sorry for not getting back to the web site sooner to give an update.

I forgot to mention that I installed the Ignitor Electronic Ignition kit from LMC, to get rid of the points.

I just tried to adjust the timing last week and it helped but I think it needs more adjusting.

My question now is, "Do I adjust the timing with the air filter on or off"?

Same question when I adjust the Idle?

Thanks again for any help.

 

1st you mentioned not driven much. How old is the gas you are burning? Old gas doesn't fire in the cylinders well and plugs up carbs.

 

I keep only a few gallons in the tank, enough for about 100 miles before needing to add some more. I also add some fuel stabilizer/treatment.

I drive it enough to need to add gas about once a month.

 

Makes no difference when setting the timing. You are interested in the "total" timing, that is the initial timing + mechanical (weights and springs), inside the distributor.

This is always checked and set with vacuum advance disconnected and plugged. Run it up with a light and see where it stops advancing on the damper. Somewhere around 34° to 38° BTDC is typical for V8, the initial timing is not too critical, let it fall where it may so as to get the right total mechanical advance. Check for ping or engine knock on hard acceleration. Advance or retard slightly as required, maybe 2° at a time, till it's just short of engine knock. Then re-connect vacuum advance.

The idle mixture adjustment is ideally set with the air cleaner installed, this can be difficult on some motors. It's not super critical to do it this way, but it helps. The engine should be thoroughly warmed up when making this adjustment. Both screws should be turned the same amount. A vacuum gauge isn't really necessary for adjustment but using one seems to help people understand what is trying to be accomplished. Getting this reasonably close makes for a lot better driveability and reducing off-idle hesitation. The idea is to lean the idle out as much as possible consistent with a smooth idle, and keep the transition slot mostly covered. A good motor will idle slow and smooth.

 

In that case the carb could still be plugged up internally. Instead of from old gas it could be from crud being picked up off the bottom of the tank.
1st set the timing with a timing light. Careful of the fan! Factory spec is 6* advanced I believe. Unless you tow or haul real heavy you can prolly get away with setting it at 10* to get it a bit more peppy. Reset the idle speed to be normal then adjust the idle mixture screws. Holley 2V? Gently screw both mixtures screws in all the way. Then back both out to 1 1/2 turns. Start the engine back up and adjust BOTH screws out THE SAME 1/4 turn at a time until the idle smoothes out. Once the idle smooths out adjust the screws 1/8 turn at a time to dial in the mixture. Hooking up a mechanics vacuum gauge to a nipple on the intake is the best way to dial in the idle mixture. You would want to adjust the mixture screws until the vacuum gauge is the smoothest and highest reading. If you don't have one then both listen to the engine and feel it by your stomach touching the body of the truck. Not only can you see an engine not running smooth, but you can also hear and feel it.

 

Well now wait a second here, keep in mind this "1.5 turns out" business is just a starting point of course, as it will be pig rich, ensuring it will start and idle. Then it will be set to the optimum idle mixture.

The mixture screws should be turned in observing when the engine reaches highest steady idle RPM or highest manifold vacuum. There's a little interaction back and forth with the RPM screw while this is going on, and a bit of a lag while the fuel already in the carb burns off.

It helps to set the idle down low, maybe 500 or so. The idle RPM will usually have to be turned down anyway as the idle screws are turned in and the mixture leans out. Just short of the point where the engine starts to stumble should be the "best lean drop" setting.

 

Now wait a minute first test that your vacuum advance diaphragm is not leaking air pass it
that will cause it to run lean an may be a faster rough idle..

Once you know it good then do your tuning.

The red neck testing of the vac. advance can be done by removing it's hose at the carb end an suck on it. You should not be able to suck air once the diaphragm compresses
in all the way.

You can remove dizzy cap to see what is happening an how it works.

Orich

 

This might be a dumb question, but did you change the real fuel filter under the fuel pump before you start changing things?

 

No. I'll stand pat on 1 1/2 turns for the starting point for the OP. Actually 1 1/2 turns out will be lean for a Holley. I've never seen a Holley with the mixture screws farther in than 1 1/2 turns out.

 

Well 1.5 turns out is overly rich, or should be, that's the idea. Turning the mixture screws further out would only make the mixture even more rich. The carb instructions, shop manual, all describe the procedure as leaning out the idle, by turning the mixture screws in... Everything with a carburetor that I've owned seems to work this way in the maintenance instructions. Even the lawnmower.

 

I was up Real late last night working on my Harley F150. Not a whole lot of sleep. You thinking 1 1/2 turns out is RICH got me thinking backwards. 1 1/2 turns out is actually lean on a Holley. Every one I remember adjusting came out somewhere around 2 - 2 1/4 if memory serves me correctly. Edited above post.

 

Lot of info to digest, I think I'm biting more than I can chew. But I'm still gonna keep on trying and learn as I go.

RichS2659 I did not replace any fuel filters, I did check them and all looked good.

The truck ran fine before the carb swap, the main reason for the swap was that no matter how many times the carb was rebuilt is will start leaking fuel on the outside from a couple of places.

I will take all this info down and give it a try this weekend.

Will give an update next week.

Thanks again.