Choking at 1000-2000 rpms

Hey guys, I'm new here and need some assistance. My father has a 65 Mustang with a small block V8. I drove it to my house to wax it for him. It was low on gas and had been sitting in his driveway for a few months. I drove it a few miles and put some gas in it. After about a mile it started back firing and really struggling off the line and in the lower rpms. I knew something was up and went back to my house. A neighbor suggested bad gas so we drain it and put new in. Still the same. Next I checked the screen in the carb but it was clean as a whistle. It idles fine but when reved at 1000 - 1800 rpms it ramps up and down. I ran out of time and haven't had chance to do anything else. What would be my next step? Thanks for any suggestions.:confused:

in line fuel filter????Vacumn hose off???

I couldn't find an in-line filter and was told they didn't have them back then. Where might it be? I'll have to look when I get home from work.

does`nt the filter screw into the carb where you hook your rubber gas line hose to it ? what do you mean by screen ? look at the points ..

Yes, the filter is in the carb where the fuel line goes in. It looks like a screen to me. Sorry wrong wordage. We pulled off the cap and everything looked good. Looked in the carb, hit the throttle, fuel streamed out at low rpms and when holding the throttle there the fuel stream gets weak. When on the throttle at the higher rpms the fuel turns to a fine mist and roars. This is all in the driveway mind you. When I took it for another drive it could barely get moving. When I finally got into second and third gear it sputters and backfires. But again at the higher rpms it runs. Maybe a bad fuel pump or the line clogged at it?

Maybe a bunch of gunk in the carb...

Did you check the point gap, condition, and the dwell??

What are the idle screws set at on the base of the carb??? 1 1/2 to 2 turns out should be a good starting point.

Is the choke plate wide open when the engine is warmed up??

for a 65' mustang im gunna guess it's stock? if it is it's probably got the 2100 motorcraft carb on it. they were common in that era of mustangs. and since you backfired the car the first thing i would go to is the pump diaphram. they blow out real easy with any kind of backfiring. i went through this on a jeep a had, changed out everything, fuel pump, filter, plugs, cap, wires, even dropped the gas tank and cleaned it cause the dang thing had just been rebuilt, but low and behold i had another bad diaphram from a small backfire when installing and setting up the new motor. it was really frustrating to boot! cause i had every diagnostic test done on my ignition system i could think of, replaced everything (course it was due so i wasn't too miffed going to NAPA) but as it would turn out the power valve again was the issue. after that she ran like new again

Bad gas (ethanol) only takes a couple months to break down 90 days is the shelf life on gas with ethanol (standard at the pump these days) and since it breaks down so fast it doesnt take much to harm the older carbs. all the issues as you describe are the same as my jeep which had the same/simliar motorcraft carb on it. it costs about 20 bucks to buy the power valve at NAPA or 25 bucks to buy the rebuild kit online and comes with the power valve the part number 4008 is typically the 2100/2150 motorcraft one you'll end up needing to get. just make sure you check the vaccum lines before you replace it. sometimes backfiring will also cause one of your lines to go kabloowee. not sure if you need it or not but i can email you a PDF file on the motorcraft to rebuild it. not sure when the last time you rebuilt the carb but it maybe a good idea to go ahead and do that as long as your replacing the power valve. there maybe some gunk from the bad gas (which can crystalize) these particles can get caught up in the jets.

Dave - I did not check the point gap and don't know what the dwell is. Do you know what the gap should be? It's an MSD.

OSK - It has a 650 Holley on 'er. A buddy also mentioned the power valve too. I'll have to get it apart to check. I've never worked on any carb before but I'm pretty mechanical so I guess it's a good time to learn.

Thanks guys for all the sugg's. I won't get to play with her til the weekend so I'll get back to you with any results . . . or failures!!

a holley will also be the power valve, they too are notorious for blowing those dang lil parts. the power valve is right on the front of the carb

If it has been sitting for a few months there is a good chance varnish has built up in the carb. Gas turns to crap very quickly these days, even sometimes with stabilizer in it.

Recently happened to my 27, hadn't driven it for a month or more and took it to a show downtown. It started running rough and I had to keep the idle up to keep it running at lights. Finally, when coming down the street to the shop I cranked it wide open through the gears and it started running good and has been ok since then. I think whatever was plugging up the jets got blown through from running it hard.

The new gasolines really take their toll on carb and fuel systems. :(

Don

yeah
if i dont start my willys regularly i end up having to tinker with the carb.

Well the good thing is that the Holley power valves are cheaper and more readily available than the motorcrafts, but thats just my own experience.

If it's an older Holley and the power valve is blown you should put the power valve blow out kit in. It's a ball check mounted in a brass tube that goes in the power valve circuit at the base of the carb. And if it set for a length of time at all the carb should be rebuilt.

On Sat. I pulled the air cleaner off. The inside was sticky in the carb. I sprayed some carb cleaner in it a couple of times and it seemed to cut out about 70% of the lower rpm stutter but not all. I played with the idle screws and set them at 1 1/2 turns on both sides. Isn't there a test if you turn them all the way in and the car dies your power valve is good? Well when I turned in the idle screw in the passenger side it kept running and on the driver side it died.? I took it for a drive and it was the same. It could barely get going and sounded like complete crap. It looks like I'll have to pull the carb. My neighbor has an AFB carb we're going to throw on to see if that's the prob. He says it should bolt right on. We'll see what happens.

From the sound of it I'd say your carb is full of varnish.

pull a plug or two and see if they are gas fouled ..

You can find on line step by step (w/pictures) instructions for rebuilding a Holley online. With the rebuild instructions from a kit it helps to understand and recognize the parts. Google or YouTube the carb part number. It does not hurt to take pics during disassembly with a cell phone.

Well with all that sticky stuff and spraying carb cleaner down it any of that varnish, ie the sticky stuff that is left overs from bad/old fuel is now going to be sitting in the bowl. as the particles slosh around either you get lucky if theyre small and pass em or if too big get caught up in the jets.

In my own opinion your overdue for a rebuild. your holley part numbers are pretty easy to figure out for which kit to buy. the number are facing you when standing at the front of the motor with the air cleaner off. if i remember right you'd said you had a 600. any how you'll want to get a clean parts bucket and some cleaning solevant for this from whay you described. get your rebuild kit and check online for a downloadable PDF file on rebuilding your carb (by part #) print it off and read through it and just check each step as you break it all down.

You'll want to soak your parts in the solevant until it breaks apart all the varnish, dont waste you money on the carb cleaner just yet, soak it cause theres passages you'll want to have that gunk broken down on. plus the whole thing will come out looking like new. after it soaks long enough to eat away (some carbs ive done or had done sat for up to 24 hours) then you'll want to use the carb cleaner to use pressure to blow out the passages. make sure all the gasket areas are nice n clean n smooth. to dry i like to use a lil pressurized air (when its almost dry)

When you reassemble the carb just make sure your jet size is correct for your application and the float is the correct height for your application. theres typically a chart that comes with the carb rebuild kit too so its not too difficult to find.

Good luck, and make sure you designate some work space to lay out all the parts and keep em on something like brand new shops towels or something so ya don't lose anything.

I finally got 'er back together and she runs like a top. I ended up swapin' the Holley for my neighbors Carter. I had to modify a couple things with the linkage and the air cleaner to make it fit correctly, but it's all gooood now. Thanks guys for the help. It's time for a cruise!!!

You are one of the very few people who ever come back and tell us how it ended up............thank you for doing that. Most times we offer all these suggestions and never find out what cured the issue. This is how we all learn.

Your original carb is probably fine but just needs rebuilt/cleaned. A lot of us on here are fans of the Carter/Edelbrock designs for street use so you have a good one on there now. Holleys seem to have a particular dislike for even the smallest piece of trash, my Son Don spent many a date fixing the Holley on his Olds convertible and got good at knowing right where to look to remove the spec that was causing the problem.


Glad you found your problem. :)

Don

Ditto, Don - It's nice to hear the resolution and know this one is "down-the-road". I have a feeling this is not the last we'll hear from this young man. Hope he keeps us updated from time-to-time on the '65!

You might have heard of an old time Gasser "Bones" Balough. He's a long time family friend and the neighbor that swapped me the Carter. We spent a few hours and a 12 pack last night tinkerin' with it. As much as I enjoyed the time, I still think he had more fun at his young age of 76 yrs. Between your gracious advice and his help, what a treat of a way to learn somethin'. We were trying get it ready for a scene in an upcoming movie shoot this weekend (Dec. 10). It looks like we made it. Thanks again and I will keep you posted on anything else.

Eric

If Bones is a friend you really need to document as much of his life as you can for posterity. So many of these greats pass and then we have so many questions we wish we would have asked them while they were alive. I bet he has a treasure box filled with old photos, articles, etc and if you sat him down on video and interviewed him about his racing days you would be doing the automobile hobby a huge favor. Please consider doing it and do it while he is young enough to be able to actively participate. I bet he would love you doing that.

We need to save our history, all the greats are leaving us.

Don

Your absolutly right Don. He's a great friend and a great racing legend. If you saw his living room, well it's a shrine!! If you google his name there's tons of stuff, interviews, racing clips from the old days up until last year. This past year is the first season we missed in a long while. We still sit in the garage after work and b.s. about it all. Such a nice man, and a blast to be around. He LOVES tellin' his stories. And everyone LOVES listening. He says it's what keeps him young. Anyways, happy motoring and I'm sure we'll chat again.

Eric