345 runs only at half choke
- Thread starter ScoutII22
- Start date
Scoutboy74
Moderator
More background info needed. Did you just get this thing this way? Was it recently rebuilt? Has it ever run properly in your experience? The list 4412 version of the Holley 2300 you have is generally considered to be too much carb for a stock IH v8 engine from idle to wide open throttle and all points in between. I have heard of a few folks who claim that they were able to make them run decently enough, but I remain skeptical. That said, the symptom you've described is more commonly associated with a lean condition. My top suspicion in your case is that you have a significant manifold vacuum leak. One common problem often encountered when the stock carb is swapped in favor of something else is what to do with the myriad of vacuum hoses...knowing which ones need to stay, which ones can go bye-bye, and knowing where to now route the ones that remain. Mix ups there can lead to air leaks and poor engine performance. So come back with some more detail and post some well lit and focused pics of your engine bay from both sides so we can see what you've got going on there.
What scoutboy said.
The biggest problem, especially if you are new to old 'binders, is most people's experience has been with the big 3.
Almost everything you May have learned about tuning a big 3 v-8 will not directly apply to an ihc sv v-8. Starting with you tune off of #8 and not #1 cylinder.
The big 3 v-8's just start getting into their power curves about the time the sv engines hit their redline. As a consequence the carbs need to be relatively small. 350 cfm is more than adequate for the sv266/304/345. The sv392, especially with the 4-bbl, can use a little bit bigger. But even the sv392 will be using a considerably smaller total cfm rating than a bowtie 396 or mopar 383.
In looking for a vacuum leak, if you are getting deaf like I am, using wd40 or starting fluid to spray around the engine works well. If you shoot into a space and the engine speeds up you know you have found at least one of the leaks.
Good luck and keep us posted.
The biggest problem, especially if you are new to old 'binders, is most people's experience has been with the big 3.
Almost everything you May have learned about tuning a big 3 v-8 will not directly apply to an ihc sv v-8. Starting with you tune off of #8 and not #1 cylinder.
The big 3 v-8's just start getting into their power curves about the time the sv engines hit their redline. As a consequence the carbs need to be relatively small. 350 cfm is more than adequate for the sv266/304/345. The sv392, especially with the 4-bbl, can use a little bit bigger. But even the sv392 will be using a considerably smaller total cfm rating than a bowtie 396 or mopar 383.
In looking for a vacuum leak, if you are getting deaf like I am, using wd40 or starting fluid to spray around the engine works well. If you shoot into a space and the engine speeds up you know you have found at least one of the leaks.
Good luck and keep us posted.
I bought it after 16 years of not running. Previous owner says the engine was freshly rebuilt... 16 years ago when they parked it. When I first had it, it ran fine, no problem with the choke, it then sat for about 4 months, with pretty nasty sticky gas in it (maybe it gummed something up?) and ever since then has just ran like crap. I've always thought it could be a vacuum leak, but I just cant find anything. I'll post pictures up tomorrow as it is currently at a shop.
Scoutboy74
Moderator
Sucking ancient varnish into your carb is just begging for trouble. Not only will it gum up the carb, it can actually do worse damage inside the engine if a valve or valves happen to get stuck while the engine is running. It ain't worth trying to save and should be totally purged from the entire fuel system. The carb will need to removed, popped apart for thorough cleaning and a rebuild kit installed. I now doubt that you have a vacuum leak...well actually the constipated carb is the vacuum leak.
If you are still sucking the same old gunk out of the tank you just wasted the effort of working on your carbs.
You need to remember that the ethanol blended bad excuse for gas we have to use acts as a cleaner of everything bad and yucky in the tank. What used to stay stuck in the tank is let loose to foul up everything up the line.
I think you need to start over and start this time with cleaning the fuel tank.
You May also have some of the soft lines collapsing due to the ethanol which will cause your engine to run lean.
The ethanol can also attack the fuel pump which will also cause your engine to run lean. Btdt with my t-all--worked just fine solo but would not pull the trailer well at all. Replaced the pump and everything is fine now.
Running lean is caused by a lack of gas, which can be helped by pulling out the choke as you have discovered.
Or it can be caused by too much air, which can also be helped by pulling out the choke.
You need to remember that the ethanol blended bad excuse for gas we have to use acts as a cleaner of everything bad and yucky in the tank. What used to stay stuck in the tank is let loose to foul up everything up the line.
I think you need to start over and start this time with cleaning the fuel tank.
You May also have some of the soft lines collapsing due to the ethanol which will cause your engine to run lean.
The ethanol can also attack the fuel pump which will also cause your engine to run lean. Btdt with my t-all--worked just fine solo but would not pull the trailer well at all. Replaced the pump and everything is fine now.
Running lean is caused by a lack of gas, which can be helped by pulling out the choke as you have discovered.
Or it can be caused by too much air, which can also be helped by pulling out the choke.
Scoutboy74
Moderator
Can you elaborate a little on the timeline of these events? No offense meant, but it kind of seems like we're pulling teeth to get info out of you. When it comes to cyber-diagnostics, too much detail is far better then not enough. We're not there to see, hear and smell what you are, unfortunately. The vast technology at our disposal can really help bridge that gap, when used properly.
Erik VanRenselaar
Member
Not that it has anything to do with your current issue, but I always chuckle when I read/hear a story like that. Who spends the time and money on an engine rebuild just to park it for years? Makes me wonder how good that *rebuild* is...
Bill Bennett
Member
Just for curiosity, did you notice the # on the carb main jets? The 4412 carb came with the #73 main jets.
I don't know the jet sizes right off hand. I'll start from the beginning. I bought the Scout, brought it home, dropped and emptied the gas tank, and continued normal tune up (oil, radiator, spark plugs etc.) I then got the new carb, and it ran great, I had an electrical problem, and had to replace the ignition pickup module. It sat for about 4 months, then went to start it up, and it ran like crap. Ever since then it has ran terrible. Replaced the gas tank, cleaned both carbs out. Still runs like crap. Replaced the fuel pump. Still runs bad. I'll post some pictures later today of the hose layouts of the engine.