Have you looked into vacuum problems? Timing? I would first plug(as close to engine as possible) all your vacuum lines (even the one to the brake booster and dist) and reset the timing with a timing light and see if it runs better. I would also check to see if you are getting vacuum leaks around the intake manifold or carb adapters by spraying starting fluid lightly along the gasket surfaces. If you have a vacuum leak your engine will rev up when you spray the leaky spot. I was having the same poor idle problems on my truck and went through all the simple fixes to no avail and finally fixed it by pouring water in the carb while reving it to about 2500 RPM! The water will clean out the carbon buildup from the valves and piston top causing much better idle. I know it sounds crazy but I poured about two 2 liters (slowly) into it and watched chunks of carbon blow out the exhaust. After I did this I was able to turn the idle down and it would actually idle!

 

I would try this too!

 

Question on the water Issue. Would It Be Wise to Give it a Oil Change AfterWords ? I know the Vaccum Lines are fine they are in the same exact spot as before the issues started. And Thanks for the advise it Helps ty will try tommorrow and see if does the job.

 

The lines may still be in the same spots but you could have hairline leaks or a bad vacuum diaphram(brake booster, vacuum advance on dist) and plugging them all off at the motor is the only way to eliminate that possibility. You should not have to change the oil after giving it the water treatment due to the fact it is going into the combustion chamber and not the crankcase. On your '78 you should only need one big vacuum line to the PCV valve, one big line to the booster and one little line to the distributer. Any other lines could be removed and plugged to clean up the compartment and eliminate later problems. I am not saying tear all the emissions hardware out but most likely with the age of your truck it is not up to emissions standards any more and would be more "air friendly" if it was properly tuned and running good. Do you have a way to add some pics to your user gallery? It always is cool to see other peoples trucks.

 

Not Yet Planning on it. Vacum Lines Are perfect and others are alredy blocked from previous owner of truck. Still having idle issues. Now it is idleing for about a Min then Dies. Do you think if the Manual Fuel Pump is bad would it cause this issue or anything else. Update: Full Tune up went in. New spark plugs and distrib cap and roter. also New wireset. Old cap was shot but issues with idle still remain. Any idea's?

Sincerly Rich

 

Sounds like it could be running too rich? Does it restart hard after it dies? Were the old plugs sooty or glossy looking? When it restarts after it dies does it smoke a little? Before I put the 4 barrel on my truck I had tried 3 other 1 barrels all from older (late 70's) and had tried to rebuild the stocker but still had the same idle problems. I had collected the parts to put in a 460 and was ready to junk the 300 but I tried the water trick and it cured the idle problem within minutes (I don't think I would have been brave enough to try pouring water in my motor if I wasn't ready to scrap it out). I think from driving many many miles with the original '86 electronic carb misfunctioning the piston tops and valves were so carboned up that when I would switch to a different carb it would make no noticeable instant change. I would install one of those cool glass see thru fuel filters right before the carb to verify that you are getting a healthy supply of fuel to the carb but generally you would experience fuel starvation when the motor is running under load and not at idle. Have you tried running the new 2 barrel with the choke partially closed? This will cause the air going through the carb to move faster causing a better vacuum pull on the gas and allowing the idle circuit in the carb to do its job by effectively changing the cfm rating of the carb to a more reasonable size. Unfortunately I don't think your answer on a stock motor was to up the carb cfm without changing other things. According to the figures you need on a street engine of 300 CI running a maximum of 3500 RPM a 258 cfm carb! A stock 302 V8 2 barrel is rated at 500 cfm due to the fact they are rated to run a lot higher RPM than the big block six was ever intended. If you put a carb from any 302 or 351 (W,M,C) you would at least have to rejet the carb to match your six to get it to run good. I have added this cool link for performance calculators for everyone to check out. http://www.tciauto.com/tech_info/calculators.htm#13

 

Nope Starts very easily, Just standard Carbon buildup. No Smoking either. Yes i have tried adjusting the choke and see if that was the issue and it wasn't same issue was present. And the I have the Holly 2300, 500 cfm. And Checked stats on it to see if it would work without changing the Motor and was said to be fine and with the New manual fuel pump same issue applies.
Just running out of Idea's. And i have tested the RPM's And Max is Between 5500 and 6500. Just to let ya know

Sincerly Rich
78 F100 Custom 1/2 ton 300 I6 3 on the tree Holley 2300
CFM 500.

 

hopefully you never run it to 6500 rpms! You should be happy with the little Holley. I noticed that on my old truck (had a 351W with the 2300 Holley) that the accelerator nozzle would trickle at idle sometimes causing it to lightly flood. It wouldn't cause it to die but it would stumble. My Holley book suggests that you can drill holes in the main throttle plates to allow you to turn the idle down yet still get enough air into the carb to keep it running. Do you have any Holley carb tuning books? The old one I have deals with some odd problems and the ways that they can be fixed.

 

Well, I dont have any books on it, they are hard to find here, not to mention they cost a fortune!! I am trying to figure out what throtttling plate you are talking about. I am not having any problems with the Accelerator Nozzle. I can barely put my foot on the gas and it reves up just fine. I have also tested the pressure and it said it was 7Lbs. PSI. Thats why I am a little stumped on what is causeing it not to idle.

Sincerly Rich
78 F100 Custom 300 4.9L I6 w/2300 Holley 500CFM.

 

The THROTTLE PLATES are the circles that move when you give the carb gas. The position of those during idle condition controls how lean or rich the carb runs at idle. The factory has little holes in these but you can drill them out to allow more air to flow past them when the carb is set at idle. This allows more air and less gas making it leaner at idle and curing a richness problem that can cause the engine to "load" up while idling. I would look on eBay to find a used Holley tuning book. I learned alot from reading it and now the inner workings of the carb are less of a mystery!

 

Paid 60.00 to find out what the issue was and now i wish i would have Not done that cause just made me felt stupid for not Knowing the issue. when you get the adapter from Summit it has 4 holes to set up the Holley 2300. I had to drill out two of the holes and Forgot to block the other two. LOL Pluged the two Holes and runs Like a Fine tune Machine. Sounds Great.

Sincerly Rich
78 F100 Custom 300 I6 w/Holley 2300 2bbl 500 CFM With Three on the Tree.

 

Sorry to bring up an old post but I found this while surfing and thought I would pass it on...
http://www.stoveboltengineco.com/aca...p?productid=91

 

i'll be rebuilding a motor with some machine work on both block and head and some performance mods, including cam, 390 holley 4bbl/matching intake, EFI exhaust manifolds and custom exhaust...this will all go into an 84 F-150 4x4 w/ either a T-18 or a ZF 5 spd behind it...i may swap to a 3.73 gearing, tho i don't mind my 3.55's that i currently have...slightly larger tires will be somewhere in the mix, as well...prob. 31's or 32's...just something to waste money on...prob. take me a while to get it where i want it, but that's fine...

MontanaFord

 

After reading these posts I'm not sure which combo to use now. My 77 w/ a 300 drives just fine untill I have to go up a mountain. 3rd gear runs the engine too hard and 4th is too high. Maybe the the 2bbl. might be the way to go since fund$ don't allocate replacing the manifolds and a 390cfm. holley.

 

I am looking for a Holley model 2280 which was made to replace the OE Carter-Webers. Any Idea where I can find one. Holley does not have any in reman, cores are hard to find.
Thanks Jeff