289 running rough once warm

[Husky350]

Hey guys,

I know these sorts of things are always a long shot, but just seeing if i can come up with any ideas that I haven't thought of already.

Background - 289 with edelbrock performer rpm manifold, HEI dizzy, msd wires, new plugs, extractors/exhaust, summit 600 carb, carter electric fuel pump(replaced fuel tank, sender, fuel lines to 3/8th lines when I put the carb and fuel pump on a couple months ago) alloy radiator/thermo fan, plus some more. Was running perfect for the last 4 months since new carb and fuel system.

So, yesterday I installed  Flowkooler water pump and stewart high flow thermostat as I was having a few overheating issues ONLY when using a thermostat and ONLY at low rpm driving(different story altogether ), plus when i pulled the water pump off when i did the front crank seal a few months ago it looked pretty sad.

While I was at it i did a flush of the block and radiator using some coolant flush, let it run for a bit, drained it all, then back flushed it with a hose till everything was flowing clear. Installed the new pump and thermostat, refilled it with coolant and started it up. Everything seemed to be running fine, just as the thermostat opened I decided to take it out for a drive. As soon as i got it out of the garage, it started missing, really badly. Well it felt like it was missing, or running rich, or lean…..it was just running crap, undrivable, about 2-300rpm lower than normal and jumping around. Put it back in the garage and left it overnight.

This morning while it was cold I pulled the plugs, a couple were pretty black, cleaned them off and re-installed(only reason i did this was because the engine was cold, i didn't want to check plugs later on and burn my pretty hands). Started her up, she ran perfectly. Sweet, must have been the plugs for some reason. Anyway, as soon as it hit about 170f it started running rough again, like a switch, pretty much when the thermostat opened i guess. Funnily enough it started running rough the same time last night.

Weird. Knowing i didn't touch anything else in the engine bay, apart from spraying water everywhere, i took the HEI apart to see if there was water in it. Nope.

Checked the timing again. It was fine.

Played around with the idle screws. Seems to get a bit more stable as i go leaner, but still rough and sounds like missing, not drivable.

Next i just sprayed carb cleaner everywhere to check for leaks, didn't notice anything.

Next I was looking at the clear fuel filter near the carb, it was only half full, usually 3/4 full. As i was watching it I saw it almost empty with the engine running, so I thought, YES, i found the problem, the fuel pump. So off I went to Eagle Auto parts and got a replacement carter pump, put it in and now the filter was 3/4 to almost full when running, HOWEVER, the miss and running rough was still there. So either there is something funky going on in the fuel tank, or the original carter pump i had decided to die at a convenient time(only a couple months old).

So, Im basically stumped now. The only thing I can thing of is either the HEI is stuffed(not sure how to test), their is some funky fuel problem happening, or, the flush has perhaps uncovered a passage through a head gasket.

Any other thoughts? Just weird as it was perfect the day before, and now after the water pump and flush it is undrivable. Only other variable maybe is the hot weather over the last couple days, maybe something to do with the fuel tank/fuel pump???(clutching at straws now)

[griff]

husky, athough theres many possibilities of a misfire ill start with one theory and let others add.
what type of choke setup have you got? so it runs fine cold but crap when at op. temp
either the choke is sticking on and running way too rich when warm (but fine when eng is cold) or when the choke comes off (like its supposed to at temp) there is a lean condition happening with your carb. Im thinking rich condition due to sticky choke.
what do all your plugs look like after it running at temp for a while? sooty, grey, white?
thats one theory down anyway.

[GLENN 70]

It could be dirt/ crap in the needle & seat after your fuel pump problem ,and when you had the fuel lines off at the pump . 1st check the choke is off .

[Husky350]

cheers for the replays.

It is an electric choke but it is working fine, had the filter off while i was adjusting everything today. The plugs were black when i pulled them this morning, but this if the first time i pulled them in 4 months, and was running fine till yesterday.
I only took the fuel lines off when i replaced the pump a couple hours ago. The whole system including the filter and carb is new, however i guess shit could have got in, so probably worth checking the carb tomorrow ;)

[Husky350]

Although it feels like a miss, it doesn't feel like it has anything to do with the idle circuit. In gear with the wheels chocked, it will run fine for about 3 seconds then lurch forward once or twice, then run fine for a few more seconds, then lurch forward again.

[Husky350]

i will add i also checked all the voltages to the pump and hei first and they were all good

[griff]

lurching can be a rich condition, some guys like to wind the mixture screws out on big horsepower engines to make it do that.
im still betting carb condition so give it the once over plus check your floats and reset your mixtures and see what happens.

[Husky350]

Sorry I actually did a typo,  I had to richen the mixture to get it to hold an idle, not lean it. I usually have the idle screws at about 1.5 out max, and today i had to go to 2 to 2.5 out to hold a rough as guts idle.

[GLENN 70]

 Does it idle or die  . It might be a misfire ,put a new set of plugs in it . NGK in a 5 heat range .

[Husky350]

It idled perfectly on 1.5 out on the idle screws until the flush, now it will pretty much die at that, and i have to go another turn plus to hold the idle, although it is still rough/missing. The plugs are newish(2 months) and i did clean them this morning, they are NGK AP5FS

[GLENN 70]

Ok they are the right plugs , I know it's a pain but I would still put a new set in . I would say it has picked up some crap in the carby ,it happens quite often when fuel line have been taken off and on . Just a little be of rubber off the hose and it will cause problems . It's a bit hard to work out without been there .

[Husky350]

Keep in mind fuel lines weren't taken off till after the problem. Yeah ill look at a new set of plugs.
Also weird thing is in the last 2 days it only runs rough once warmed up(exactly when the thermostat opens) which is about 160F

[GLENN 70]

Or maybe when the choke comes off . When its warm and runs crap with air cleaner off bring the choke on a bit. Or cover the top of the carby a little with your hands and see what happens .  Then cover it totally slowly and see if it stalls ,if it doesn't it has a vacuum leak .

[shaunp]

Is it a Chinese distributor ?  or it's just rich for some reason., summit carb will be Chinese as well, think they are Procomp. You could also measure the leads with a multimeter to see if any are HR.

[Husky350]

Trying to relate the problem to the flushing of the block, i used a hose with cool water to back flush the block after i ran it for a while with coolant flush. The motor wasn't hot, i let it cool for a couple hours, but it was definitely warm. You think its possible for the cold water to cause a leak somewhere?

[Husky350]

Leads are good tested them when I made them a few months ago.
Dizzy was on the car when i bought it, no idea of it's history.
The Summit carbs are an improved design of the Holley 4010, of which summit bought the design for off holley. Assembled in the states, couldn't tell you where the parts are made, but in my limited experience of carbs it is the best one i have used so far.

[shaunp]

Trying to relate the problem to the flushing of the block, i used a hose with cool water to back flush the block after i ran it for a while with coolant flush. The motor wasn't hot, i let it cool for a couple hours, but it was definitely warm. You think its possible for the cold water to cause a leak somewhere?

Likely unrelated. Don't over complicate stuff. I had a 2002 V8 Discovery that belongs to a mate here the other day, everyone was sure it had a fuel injection issue, I said, I reckon it needs leads, they are the ones it left Sollihull factory  with, no no they said, you know they are hard on coil packs, guess what it had 2 crook leads. not $350 worth of coils. Start with the simple stuff, does the choke work, ie go off when it's hot, is it flooding, are the leads ok, are the plugs ok etc. Engines all work the same. Spark, air fuel. It's extremely unlikely you have hurt an iron engine flushing it.

[Husky350]

Yeah i hear ya, only thing on the back of my mind is that the car has not been gradually running rough over time etc.
After my overhaul of the fuel system, leads, and new carb the car has been perfect for the last 4 months plus, not an inkling of a miss or rich/lean.
It's like a switch has been flicked directly after the flush/water pump.

cars…..it's a love/hate thing

[Husky350]

Just checked the needle/seat, all good there.

[GLENN 70]

I would still be a new set of plugs in , NGK AP5FS . ,it could be a lead or arcing out. Start the engine and try to hear a spark jumping ,or have a look in the dark . It could be so many things . Check under the dizzy cap for a crack . Sorry just pulling things out of the air now . Cheers Glenn .

[1966stang]

While changing the plugs do a compression test. My original 289 had similar problems and found compression to be low on a couple of cylinders. Still to pull it down to find the reason as I fitted a rebuilt engine so no clues apart from that but does seem strange that it appears to be temperature related.

Best of luck finding the problem

[Macka]

It just sounds like you have knocked the wire off the choke on the carb or something basic.  Get the car warm and take the air cleaner off and see if the choke stops working.  That's all it will be.

[Husky350]

Definatley not the choke.

Update:

Got some new plugs and while i was at it did a compression test.
Came back 160 across all with slight variation with 6 at 170….cold engine.

So chucked the new plugs in, reset the idle screws at 1.5 out, and started her up. As soon as the choke started to open she died. Took the screws to 2 turns out and it held the idle, but really rough. Played around closing the choke and it seemed to hold a better idle when the choke was almost shut, indicating a leak somewhere.
Sprayed carby cleaner everywhere, no indication of leak. Tightened every manifold bolt and carb studs, no change.

So it either sounds like air getting in somewhere or not enough fuel, but the needle/seat seem fine, float level seems correct and i did put a new pump on yesterday.
 

[shaunp]

Does it have power brakes? the booster could have died.

[Husky350]

Yeah i plugged off the booster nipple on the manifold to rule that out