joe73vette

The title says it all. It started right up last night and I broke-in the cam for 20 minutes. The ignition timing was a little late (zero degrees) so I moved it to 8*, but it still didn't have a real strong idle, dropping from 800 to 500 in gear, and not running well. Today I changed the oil and took it out for its maiden voyage and it wouldn't take a load, sputtering and cutting out starting up a hill. The vacuum at idle was only about 13". I reset the timing to 36* by 2000 rpm (14* at idle) and the idle vacuum didn't change. I turned the idle adjusters to best vacuum, settling on 2-3/4 turns from seated, bringing it to 15" with a slight flutter in the needle. It also has a sputter or miss at a steady 2000 rpm. It idles steadily, but not strong. Now it won't "take the gas" from idle (good pump shot) in drive and seems sluggish picking up rpms in park/neutral. I didn't even want to take it out for a ride for fear of getting stranded.


I used the same Q-jet as before, when it ran great, on the same manifold (baked and cleaned). The cam isn't real big, a Crane H-268-2 (218/230@.050; .459/.486 lift; 112°lobe sep), and the heads are those Summit brand Dart heads (9.6:1). I just tried disconnecting the EGR, no difference. Vacuum advance is on the same ported source as before.

It looks good, but why won't it run? Thanks, Joe
......

stingr69

Pull the plugs. Then you will know a lot more.

-Mark.

joe73vette

I pulled the easy ones, #1 and #5-8. They were all chocolate brown with black on one side of the center electrode and on the metal parts.

I'll post a picture after my camera battery recharges.

Joe

73jst4fun

I agree with stingr69, pull the plugs first, make sure your timing is correct, then I would look at the carb, float not set correctly, stuck,
dirty filter, vacuum leak.....that's where I would begin...good luck

joe73vette

I think tomorrow I'll try using manifold vacuum for the advance. Too late to run it tonight. Joe

cardo0

Carb should be OK if u drained it before letting it sit in storage. But if the old fuel was allowed to dry in the bowls it could be gummed up in the feed tube passeges.
I recall a car stumbles when its drunk on fuel but bogs when too lean. So does it sputter and chug then pick up speed or does it just go flat like someone unplugged it? Black plugs sounds like maybe a stuck choke or the power piston is stuck open as maybe a vacuum tube to the pwr vlv is plugged - i think its vac that keeps the pwr piston pushing the pri rods into the jet orifices and metering the correct fuel for load. Yea, try and give the pwr piston a push to free it. I think there is an access cover on the top hat to do this.
Anyways sounds like ur just finishing up from the overhaul. Congrats. cardo0

wogs73

Make sure the plug wires are correct. This happens sometimes and two will be swapped and it will run but not very good.

Hershey

Joe, pull your timing on around a little more, about 12-14 btc and see if that doesn't help. Hershey

joe73vette

Here's what the plugs look like: I don't know if the black is from all the oil on the cylinders and pistons from assembly or what? It was a little shiney.


I will check the following and let you know what I find:
Check wires are in the right firing order - checked some they were OK, will check the rest tomorrow
Check dwell and timing - dwell was 25*, now 30*; timing 34* @ 2000rpm
Look for vacuum leaks with starter fluid - tommorow
Check that EGR isn't leaking by opening it with vacuum - checked OK
Rap on carb to unstick float - pulled top off carb, level was low, might have leaked past well plugs - black float didn't seem to have gas inside. Found the power piston was stuck down, still isn't totally free.
Use manifold vacuum for advance - increased idle vacuum from 14" to 16".
Performed "bubba tune-up" by putting hand over choke with engine running to suck gas through passages. Idle smoothed a little.

I took it for a short drive, it still cuts out intermittently trying to accelerate up a medium hill as slow speeds, in either second or kicked down to first - can the carb bowl be draining that fast if it is really a low float? Didn't check it after running, will try tomorrow.

It did feel good for a second when it first kicked down. Joe

stingr69

Plugs are probably fouling out. What heat range are you using? Step up the heat range and make sure the carb is not flooding. Look for any vacuum hose leaks. This is probably nothing major, just typical fresh engine install issues.

-Mark.

joe73vette

When the motor cuts out under load, it feels like it is going to stall, like shutting off the key. It's not RPM related. It takes a second or two under load then it starts doing that cutting out and back on then out then on until the load is removed. Could it be the fuel pump went bad while it was out of the car? Or, what kind of electrical problem would do that? This one has me stumped. And the weather is supposed to be beautiful all weekend. Thanks, Joe

Matt Gruber

how many volts at coil +?

joe73vette

6 volts key on, 11 with motor running.

I accidently did some more diagnosis - I forgot to hook up the accelerator pump after verifying the jets and rods. The motor still ran but stumbled worse than usual when you give it gas. There is a bunch of grey smoke when while it picks up RPM, too, mostly from the right side exhaust.

Carb specs: #17054919, 74 pri jets, 43 pri rods, DA sec rods, 3/8" float level.
Joe

bobs77vet

did you know that mine did...

joe73vette

The plugs do look black, I'm using AC R44T plugs, which way is hotter, 43 or 45? I'm going to replace the fuel pump, too. Joe

bobs77vet

just a thought here your EGR isnt hooked up wrong and always getting vacuum is it? and you know the diaphram is working right and you can feel it moving when you put your hand underneath it?? if this is hooked up wrong the engine will run horribly...

silver74vette

I think going through the carb would be a good idea, inexpensive too. Sounds like fuel overindulgence and the soot on the plugs backs that up. Nice looking motor!!

stingr69

45 is hotter. Try some 45's and see if it helps. The new plugs will run a little hotter so they burn off the deposits better. Verify the accelerator pump and fuel delivery is fine. It is usualy something pretty basic that is wrong. I bet you will figure it out soon.

-Mark.

bobs77vet

you know, a screwed up fuel pump and floats that are out of whack will really ruin your day....

cardo0

Just guessing but check fuel press <10psi - best press for Qjet is 7psi. Could be a inlet vlv won't seat. But really that would be more of a problem at idle than when u open the throttles.
The power piston can have problems with spring and sticking and i think ur problems is in the primary side/circuits. So lets think about it:
1-idle circuit > OK
2-pump shot - look for fuel squirt > OK
3-high fuel press - inlet leakby/bad idle > OK
4-low fuel press - check with gauge? > could be lean bog ?
5-sticking pwr piston ?
6-bad choke - verify opens > OK
7-sec air vlv - not open untill high rpm? or flop open at light touch of throttle? > shouldn't open until throttle over 1/2 open
BTW i think the AC44RT(S) plug is just fine and its in the carb.
Hope this helps. cardo0