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Author Topic: Startup problems after head gasket replacement  (Read 332 times)

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Offline Bellavara

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Startup problems after head gasket replacement
« on: November 28, 2018, 06:38:52 PM »
I recently bought an 86 Eagle with the 258 I6 in it.  It's a great looking car, picked it up for $650 because it had a blown head gasket and it was shooting plumes of white smoke out the exhaust.

First day I get it home, I start it up and sure enough it runs just fine, except for the white smoke of course.  I didn't keep it on for more than 20 seconds, just enough to verify that the problem was there, and I shut it off.  Oil wasn't milky, coolant was brown, even more evidence toward exactly the problem it was supposed to be, so the disassembly on the engine began that night.

Fast forward about a week.  The (freshly machined) head's back on the block with a new gasket, valve train is put back in, valve cover is on with a new gasket, intake/exhaust manifolds bolted back down tight with a new gasket, carb is put back on.  I go to start it up...

Fuel is pulled through the lines, into the carb, and fuel starts to spark properly.  BUT...  The carb starts popping, very consistently.  The motor won't RUN, but it will CRANK just fine. Pop-pop-pop-pop-pop-pop.

Here's my situation right now, every tidbit of information I can think of.

I never touched the distributor, it stayed on the block where it was when I got the car.  The only thing I did was disconnect the plug wires from the plugs, but I numbered them properly so they are back in their correct positions.

I took off the carb, but I didn't adjust it in any way and stored it on a flat and level surface for the entirety of the procedure.  AFAIK it's a Carter BBD.  Sticker that's on it says it's a rebuilt carb installed in 2016, 30,000 miles ago.  Previous owner had a bunch of other maintenance done to the car in 2016 too, I have most of the old service information.

I checked the valve train when I put it back on, it all felt nice and snug, 26 foot pounds like it said in the manual that came with the car.  Besides, if one intake valve were to stick open the car would still start, it would just run like crap.

I also changed the oil and flushed the coolant, did a heater core bypass (it was leaking too, P.O. said), put new spark plugs in it, new T-stat and housing, and a few other smaller things.

There's no white smoke when I crank it, so I take that to mean that the head gasket job went well for the time being.

The one thing I can think of that might be a problem is that I bodged most of the vacuum lines in and around the carb.  I'm new to vacuum lines and they're confusing, so I didn't know that the pictures I took of everything before I took it all apart wouldn't really give me any information.  Do vacuum lines really have that much effect on the car starting?  I mean, it's still just an engine, should need just proper air, fuel, and spark to start and run.  I could understand vacuum lines being the problem if it ran like crap, but not starting AT ALL...?   :banghead:

So, what do you all think?  It sounds like ignition timing from everything I've read from other sites but that just doesn't make any sense to me, considering I never touched it and it ran just fine before I took it all apart.  I know for a fact that I put all the metal back together properly, and all the electronics like sensors and whatnot were easy to find matchings for.  The most confusing part to me is that most everything that should have an effect on the car running wasn't messed with (apart from the carb being removed to disco the intake/exhaust manifolds, and the valve train being removed (and stored gently in a cardboard box, nice and organized and safe until it was re-installed)).  Distributor was untouched, carb was removed gently and put somewhere it wasn't touched at all until I put it back on, and valve train felt nice and seated when I put it all back in.

I'm really stumped.  The night I went to start it up I had a bit of an audience watching, so maybe the car got shy?   :o

Online AMC of Houston

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Re: Startup problems after head gasket replacement
« Reply #1 on: November 29, 2018, 01:04:34 AM »
Back to basics.  Triple-check the firing order/plug wire placement.  If that's OK, sounds like a valve not closing (or stuck open).   If the machine shop ground the valves, but didn't take the same amount of metal off the top of the stem; valve may not be closing.    If you accidently "missed" the lifter with a push rod, a valve may be not doing anything.   I'd take off the valve cover, crank the engine, and see if one of the rockers isn't moving.   Or do a compression check to see which cylinder is the culprit (stuck-open valve = no compression in that cylinder) to narrow things down.

Good luck.
George G.
'81 Eagle Sundancer
'85 Eagle Waggie
1960 1902 Rambler Replica
'64 American
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Offline AMC1

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Re: Startup problems after head gasket replacement
« Reply #2 on: December 15, 2018, 09:45:18 AM »
How did your problem turn out?
1976 gremlin
pair of 1983 SX4's sports
1946 Cushman step-thru


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