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18 total messages Started by Charles T. Low Sun, 03 Jul 2005 12:39
rough engine intermittent
#3862
Author: Charles T. Low
Date: Sun, 03 Jul 2005 12:39
72 lines
4636 bytes
TIA to all.

1978 Chrysler 318 V-8 gasoline engine, www.ctow.ca/Trojan26, hour-meter 
coming up to 1000 hours, about half of them in the four years I've owned the 
boat.

Recently the engine began to run rough, stumbling quite badly. This happened 
several times about twenty minutes out of port, trolling along in the 
1200-1400 rpm range. Twice, I have then put the boat up on plane to scoot 
home (3200-3400 rpm), only to find that half-way home the whole problem 
disappears quite suddenly and dramatically, the engine smooths out, revs 
pick up and I have to pull back on the throttle.

One other observation: when misbehaving the port exhaust manifold (I think - 
the thing with the risers leading to exhaust hoses, muffler...) stays cold. 
Once the problem clears up, both manifolds get warm.

My mechanic found that some of the exhaust manifold plugs had corroded out, 
so he retapped and replaced them, cleaning up the engine compartment air 
(dangerous to be exhausting CO into engine room, I know), and he said that 
likely explained my problem: that after a while the engine area filled with 
exhaust which didn't support combustion well enough. Running on plane 
scooped more fresh air in through the vents and so it cleared up. (Didn't 
explain the cool port manifold however...)

The engine did sound much better with the plugs replaced, but the stumbling 
after twenty minutes of low-speed operation recurred. I checked both the 
water-separating and inline fuel filters, and found a trace of sediment in 
the water-separating one, but no water. I cleaned the air filter, and 
brightened and tightened the battery connections. The mechanic checked the 
distributor by feeling for shocks, but got none. Of course, when I took him 
out to demonstrate the problem, it didn't occur, although we went right upon 
plane rather than reproducing the experimental conditions exactly.

So, yesterday I changed the spark plugs (reminding me yet again of the joys 
of standing on my head for hours in a tiny space in the bilge). The old ones 
were blackened, and I checked a few gaps but didn't really dwell on this (no 
pun) and they seemed OK. The new plugs were in the 0.032" range. The old 
ones, especially at the aft end of the engine which sits lower due to the 
engine not being level in the boat (straight-shaft inboard), were oily on 
the threads, and I think that the further aft one had oil further into the 
block on the threads ... which seems strange to me. They're very hard to get 
at with a spark plug wrench, and I'm wondering if they were never quite 
tightened in enough. (I was careful not to overtighten, however - having 
stripped threads once many years ago...)

I was going to change the leads, too, just for thoroughness, but couldn't 
find the right marine set late on a Saturday afternoon. Will have another 
look Monday. The distributor cap and electronics control module were new two 
summers ago (about 200 engine hours ago), as were the plugs and leads.

Then, I took the boat out for a prolonged low-speed cruise - and everything 
worked perfectly. The weather was a bit cooler than it has been here (26C 
instead of 32C) and a bit windier, so again my original conditions could not 
be exactly replicated, but I'm hoping the problem had something to do with 
the plugs.

Summary: was running rough after twenty minutes of low-speed operation, port 
exhaust manifold cool, cleared up after a few minutes at planing speed.

Anything obvious that I'm missing?

Thanks again.

Charles

====

Charles T. Low
www.boatdocking.com

====
Re: rough engine intermittent
#3864
Author: Mike G
Date: Sun, 03 Jul 2005 14:05
46 lines
3312 bytes
In article <88f77$42c7dc6a$40ebcf0c$16800@ripnet.allthenewsgroups.com>, 
ctlow4@boatUNdocking.com[withoutUN] says...
> TIA to all.
> 
> 1978 Chrysler 318 V-8 gasoline engine, www.ctow.ca/Trojan26, hour-meter 
> coming up to 1000 hours, about half of them in the four years I've owned the 
> boat.
> 
> Recently the engine began to run rough, stumbling quite badly. This happened 
> several times about twenty minutes out of port, trolling along in the 
> 1200-1400 rpm range. Twice, I have then put the boat up on plane to scoot 
> home (3200-3400 rpm), only to find that half-way home the whole problem 
> disappears quite suddenly and dramatically, the engine smooths out, revs 
> pick up and I have to pull back on the throttle.
> 
> One other observation: when misbehaving the port exhaust manifold (I think - 
> the thing with the risers leading to exhaust hoses, muffler...) stays cold. 
> Once the problem clears up, both manifolds get warm.
> 

A couple of things come to mind but the top of the list one is that you 
are running rich and loading up the engine at the low RPM and the good 
run at WOT is cleaning things up. 

A compression check probably wouldn't be out of order either since the 
second item on the list is a question of how well the valves are 
seating. Especially if you do a lot of trolling. five hundred hours of 
more low RPM trolling then high speed operation can give you quite a 
build up of carbon which may be getting to a point where the seating is 
only marginal.

There is always the hotter plug thing but since I'd only consider it if 
you were doing a whole lot more trolling then running at WOT. I'd only 
suggest it after you gave things a lot of thought and a second opinion 
from your mechanic.

I know it doesn't address the manifold thing but.................

Good luck


-- 
Mike G.
Heirloom Woods
mikeg@heirloom-woods.net
www.heirloom-woods.net
Re: rough engine intermittent
#3844
Author: Bowgus
Date: Tue, 05 Jul 2005 21:35
32 lines
3093 bytes
Last season I had a problem with either the carb float sticking and/or the
needle valve sometimes not seating causing excess fuel to "dribble" into the
engine causing the symptoms you describe. I would then have to coax the revs
up and at the higher speed, that extra fuel was not a problem, and the
problem would resolve itself.

I was not that anxious to replace the float/needle valve last season so
thought I'd try something different. I installed a fuel shut off, and ran
the carb dry before storing (I removed the plugs and sprayed the fogging oil
directly into the cylinders and cranked over a few times). This spring
before firing it up, I sprayed carb cleaner into the carb fuel bowl via the
vent and let it sit for 5 minutes ... then started it up. So far no
problems, so here's hoping I won't have to work on the carburator at all.

Something I heard you might try, is install the fuel shut off (if you don't
already have one), and if it starts missing, shut off the fuel and run the
carb dry. Then tap on the carb (to free a stuck float/needle valve and
gently), then turn on the fuel and see if the problem is gone. I have a
mechanical fuel pump ... maybe if you have an electric pump, just pull the
fuse???

And if the problem goes, then I guess the decision would be to repair the
carb ... or not.


> Recently the engine began to run rough, stumbling quite badly. This
happened
> several times about twenty minutes out of port, trolling along in the
> 1200-1400 rpm range. Twice, I have then put the boat up on plane to scoot
> home (3200-3400 rpm), only to find that half-way home the whole problem
> disappears quite suddenly and dramatically, the engine smooths out, revs
> pick up and I have to pull back on the throttle.
Re: rough engine intermittent
#3846
Author: keithgriff_327
Date: Wed, 06 Jul 2005 06:30
9 lines
1605 bytes
15 years ago I had a 55 hp evinrude that ran very rough . Repair shop
did a tune up but could not find anything amiss. Next time out same
thing happened. Once up on plane , hitting wave tops , engine began
missing and stumbling. By accident I jiggled ignition key , found it
was loose. Turned out ignition switch was making/breaking in rough
water.
First thing I check now on every trip out.

Keith in BC
Re: rough engine intermittent
#3847
Author: Bowgus
Date: Thu, 07 Jul 2005 01:33
8 lines
1573 bytes
I'll remember that one

 Turned out ignition switch was making/breaking in rough
> water.
> First thing I check now on every trip out.
>
> Keith in BC
>
Re: rough engine intermittent
#3848
Author: Charles T. Low
Date: Sat, 09 Jul 2005 10:06
57 lines
3191 bytes
Thanks, Mike,

So far, I replaced the spark plugs and since then have had no trouble. That 
doesn't mean the trouble is over, but preliminary indications are good. The 
electrodes or whatever they're called were black, and there was oil on the 
screw threads, moreso the further aft on the engine (which sits a bit lower 
than the front) ... what this means I have no idea and so far no one else 
I've asked does either. I checked a few of the gaps and they seemed about 
the same as on the new plugs, around 0.032".

I'm also going to replace the leads just for thoroughness.

The engine was compression-checked four years ago, about 500 hours of 
running time, so a lot might have changed since then. But, although it uses 
oil, it doesn't use much. I put in a litre only every 50 hours or so (which 
is about when I should be changing it anyway).

Thanks again.

Charles

====

Charles T. Low
www.boatdocking.com

====

"Mike G" <mikeg@heirloom-woods.net> wrote in message 
news:MPG.1d31ba8bd040e98a9896fa@news.comcast.giganews.com...
>
> A couple of things come to mind but the top of the list one is that you
> are running rich and loading up the engine at the low RPM and the good
> run at WOT is cleaning things up.
>
> A compression check probably wouldn't be out of order either since the
> second item on the list is a question of how well the valves are
> seating. Especially if you do a lot of trolling. five hundred hours of
> more low RPM trolling then high speed operation can give you quite a
> build up of carbon which may be getting to a point where the seating is
> only marginal.
>
> There is always the hotter plug thing but since I'd only consider it if
> you were doing a whole lot more trolling then running at WOT. I'd only
> suggest it after you gave things a lot of thought and a second opinion
> from your mechanic.
>
> I know it doesn't address the manifold thing but.................
>
> Good luck
>
>
> -- 
> Mike G.
> Heirloom Woods
> mikeg@heirloom-woods.net
> www.heirloom-woods.net
Re: rough engine intermittent
#3850
Author: Charles T. Low
Date: Sat, 09 Jul 2005 10:31
62 lines
3759 bytes
Thanks. The carb remains a source of mystery to me, although I've read about 
how they work and looked at diagrams - I think I need to see it disassembled 
in front of me and be talked through it once. I have thought of a carburetor 
problem. I do have a fuel shut-off. Anyway, it's working at the moment, but 
I'll have to give this some more thought, because reliability is so 
important. My mechanic didn't mention the carbutetor, but I also didn't ask 
him.

I think it's more likely something affecting only some cylinders, because of 
the coolness of one manifold while the problem is active, resolving as the 
problem disappears.

Charles

====

Charles T. Low
www.boatdocking.com

====

"Bowgus" <bowgus@rogers.com> wrote in message 
news:EtidnVj-j7jnYFffRVn-rg@rogers.com...
> Last season I had a problem with either the carb float sticking and/or the
> needle valve sometimes not seating causing excess fuel to "dribble" into 
> the
> engine causing the symptoms you describe. I would then have to coax the 
> revs
> up and at the higher speed, that extra fuel was not a problem, and the
> problem would resolve itself.
>
> I was not that anxious to replace the float/needle valve last season so
> thought I'd try something different. I installed a fuel shut off, and ran
> the carb dry before storing (I removed the plugs and sprayed the fogging 
> oil
> directly into the cylinders and cranked over a few times). This spring
> before firing it up, I sprayed carb cleaner into the carb fuel bowl via 
> the
> vent and let it sit for 5 minutes ... then started it up. So far no
> problems, so here's hoping I won't have to work on the carburator at all.
>
> Something I heard you might try, is install the fuel shut off (if you 
> don't
> already have one), and if it starts missing, shut off the fuel and run the
> carb dry. Then tap on the carb (to free a stuck float/needle valve and
> gently), then turn on the fuel and see if the problem is gone. I have a
> mechanical fuel pump ... maybe if you have an electric pump, just pull the
> fuse???
>
> And if the problem goes, then I guess the decision would be to repair the
> carb ... or not.
>
>
>> Recently the engine began to run rough, stumbling quite badly. This
> happened
>> several times about twenty minutes out of port, trolling along in the
>> 1200-1400 rpm range. Twice, I have then put the boat up on plane to scoot
>> home (3200-3400 rpm), only to find that half-way home the whole problem
>> disappears quite suddenly and dramatically, the engine smooths out, revs
>> pick up and I have to pull back on the throttle.
>
> 
Re: rough engine intermittent
#3851
Author: Bowgus
Date: Sat, 09 Jul 2005 12:08
27 lines
3067 bytes
OT but may be worth sharing: And something else I once heard ... spark plugs
are subject to vibration, and the ceramic insulation may crack over time,
resulting in carbon tracking and reduction/loss of ignition spark. To sum
up, the story is that plugs may look good, but may in fact not be. So
replacing then every couple of seasons is I'm thinking not a bad idea ... I
think I'll include bi-annual plug replacement in my preventive maintenace.

> I think it's more likely something affecting only some cylinders, because
of
> the coolness of one manifold while the problem is active, resolving as the
> problem disappears.

In my V6, there's a ball/spring mechanism in the cooling system that I come
across every fall when I pull all the water lines for draining/winter
storeage. I've just now looked through my Seloc manual, and don't see it. It
may have something to do with controlling water flow to each manifold ...
dunno ... I'll keep looking for info on that. If one manifold is cold, that
says to me that's where (most of) the water flow is going.

And it could be you have 2 problems. Perhaps you had/have some water in your
fuel/tank ... gas line antifreeze (alcohol) would absorb any water allowing
it to pass through the system. Gas treaments apparently also absorb water.
One reason I picked a carburated engine is that they're much more resistant
to water in the fuel ... may stumble a bit, but the water tends to make it's
way through the carb eventually ... unlike an injected system which I
understand may have to be torn down to get the water out. So, a water
separator is a "shall" for injected systems.
Re: rough engine intermittent
#3852
Author: lbrty4us
Date: Sun, 10 Jul 2005 01:00
18 lines
2184 bytes
Charles T. Low wrote:

> So far, I replaced the spark plugs and since then have had no trouble. That
> doesn't mean the trouble is over, but preliminary indications are good. The
> electrodes or whatever they're called were black, and there was oil on the
> screw threads, moreso the further aft on the engine (which sits a bit lower
> than the front) ... what this means I have no idea and so far no one else
> I've asked does either.

And this is an interesting point.  Taken together with your
consumption, it could be sucking oil from the guides on start/warmup
that's sat in the head (proportionately moreso aft), and eventually
fouling the plugs.  Have you checked for any smoking at startup?  You
could also pull your new aftmost plug after a brief startup/shutdown to
see if it's likewise getting oily.  If it were the case the problem
would resurface after awhile & let you know.

Nice book, BTW.
Re: rough engine intermittent
#3854
Author: Charles T. Low
Date: Sun, 10 Jul 2005 10:59
48 lines
3035 bytes
Thanks and to the several others who have offered recent help.

And although I had hoped the problem was fixed, it recurred yesterday. As 
soon as it started to stumble, after trolling around for a while (teaching 
my daughter how to dock!), I took her up on plane and the whole thing 
straightened out in very short order. Very weird.

I haven't quite got the innards of an engine visualized to the extent that I 
can see how guides and spark plugs inter-relate, but no matter - all food 
for thought, research, and further discussion with my mechanic.

Thanks again.

Charles

P.S. And thanks for the kind words.

====

Charles T. Low
www.boatdocking.com

====

<lbrty4us@aol.com> wrote in message 
news:1120957210.860290.127160@g14g2000cwa.googlegroups.com...
> Charles T. Low wrote:
>
>> So far, I replaced the spark plugs and since then have had no trouble. 
>> That
>> doesn't mean the trouble is over, but preliminary indications are good. 
>> The
>> electrodes or whatever they're called were black, and there was oil on 
>> the
>> screw threads, moreso the further aft on the engine (which sits a bit 
>> lower
>> than the front) ... what this means I have no idea and so far no one else
>> I've asked does either.
>
> And this is an interesting point.  Taken together with your
> consumption, it could be sucking oil from the guides on start/warmup
> that's sat in the head (proportionately moreso aft), and eventually
> fouling the plugs.  Have you checked for any smoking at startup?  You
> could also pull your new aftmost plug after a brief startup/shutdown to
> see if it's likewise getting oily.  If it were the case the problem
> would resurface after awhile & let you know.
>
> Nice book, BTW.
Re: rough engine intermittent
#3835
Author: Bowgus
Date: Sat, 16 Jul 2005 20:55
19 lines
2400 bytes
About that ball/spring thing ... it's function is still not clear to me, but
... it's purpose seems to be to balance the cold water bypass to the 2 sides
of the (e.g. my V6) engine. There's a pic of it ... it's at the top of the
lower (bottom) diagram ... Warm Manifold System. So if one manifold is cold,
maybe the thermostat is not opening as soon as it should (engine is actually
overheating) and cold water is being directed more to one manifold (by the
tee valve assembly) rather than to both?

The link ...
http://www.perfprotech.com/home/techtips/warm-manifold-cooling-tips.htm

Hey, just thinking out loud here :-)

> In my V6, there's a ball/spring mechanism in the cooling system that I
come
> across every fall when I pull all the water lines for draining/winter
> storeage. I've just now looked through my Seloc manual, and don't see it.
It
> may have something to do with controlling water flow to each manifold ...
Re: rough engine intermittent
#3836
Author: Charles T. Low
Date: Mon, 18 Jul 2005 10:57
37 lines
2717 bytes
I had a little look at that link and am having trouble following the 
description - not the type of thing to read in a quick scan!

In the meantime, the engine is still intermittently running rough (when run 
at low speed on hot days for 20-30 minutes, clears up in a few minutes under 
higher load...). I have found corrosion inside the distributor cap and will 
be replacing that, then reassessing - the number of possible causes that I 
have come up with is a little staggering - and my mechanic agrees!

I also favour having a look inside the carburetor, but mechanic is hesitant, 
saying they're often never the same after, in his experience ... hmm...

====

Charles T. Low
www.boatdocking.com

====

"Bowgus" <bowgus@rogers.com> wrote in message 
news:nYydncM9N4HV6UTfRVn-sw@rogers.com...
> About that ball/spring thing ... it's function is still not clear to me, 
> but
> ... it's purpose seems to be to balance the cold water bypass to the 2 
> sides
> of the (e.g. my V6) engine. There's a pic of it ... it's at the top of the
> lower (bottom) diagram ... Warm Manifold System. So if one manifold is 
> cold,
> maybe the thermostat is not opening as soon as it should (engine is 
> actually
> overheating) and cold water is being directed more to one manifold (by the
> tee valve assembly) rather than to both?
>
> The link ...
> http://www.perfprotech.com/home/techtips/warm-manifold-cooling-tips.htm
>
> Hey, just thinking out loud here :-)
Re: rough engine intermittent
#3837
Author: Terry Spragg
Date: Mon, 18 Jul 2005 13:02
66 lines
4256 bytes
Charles T. Low wrote:
> I had a little look at that link and am having trouble following the 
> description - not the type of thing to read in a quick scan!
> 
> In the meantime, the engine is still intermittently running rough (when run 
> at low speed on hot days for 20-30 minutes, clears up in a few minutes under 
> higher load...). I have found corrosion inside the distributor cap and will 
> be replacing that, then reassessing - the number of possible causes that I 
> have come up with is a little staggering - and my mechanic agrees!
> 
> I also favour having a look inside the carburetor, but mechanic is hesitant, 
> saying they're often never the same after, in his experience ... hmm...
> 
> ====
> 
> Charles T. Low
> www.boatdocking.com
> 

One should expect it to be somewhat better, and in no qualified 
hands, ever the worse for care.

My old zenith carb was worn so bad that the throttle shaft rattled 
on idle, its' fibre end washers worn way out, delivering varying 
amounts of vacuum leak into the intake manifold, which really made 
life with the old girl an erratic thing, to say the least, 
particularly when lower power settings were needed.  As well, a 
somewhat sticky needle valve must have been able to stick either 
open or closed, mysteriously and capreciously. It's better, now.

Fixing a carburettor is an essential basic automotive and boating 
skill which, thanks to induction fuel injection and computerised 
engine control, is becoming a skill of the past. If your mech is 
dubious, you need a real mech.

A couple of small rubber "O" rings on the ends of the shaft, 
retained with a little brass snare wire seems to have steadied the 
engine up considerable.

Trry K


> ====
> 
> "Bowgus" <bowgus@rogers.com> wrote in message 
> news:nYydncM9N4HV6UTfRVn-sw@rogers.com...
> 
>>About that ball/spring thing ... it's function is still not clear to me, 
>>but
>>... it's purpose seems to be to balance the cold water bypass to the 2 
>>sides
>>of the (e.g. my V6) engine. There's a pic of it ... it's at the top of the
>>lower (bottom) diagram ... Warm Manifold System. So if one manifold is 
>>cold,
>>maybe the thermostat is not opening as soon as it should (engine is 
>>actually
>>overheating) and cold water is being directed more to one manifold (by the
>>tee valve assembly) rather than to both?
>>
>>The link ...
>>http://www.perfprotech.com/home/techtips/warm-manifold-cooling-tips.htm
>>
>>Hey, just thinking out loud here :-)
> 
> 
> 
Re: rough engine intermittent
#3838
Author: Charles T. Low
Date: Tue, 19 Jul 2005 11:30
39 lines
2904 bytes
Thanks, Terry,

A marine mechanic to me is a bit like a hairdresser to my wife - we have a 
relationship, and I feel loyal. That might interfere with getting my carb 
maintained, however, and I'll have to think about how to approach that. I'll 
come up with something. Step number one will be to replace my distributor 
cap, rotor and leads (they have to be specially ordered - old engine, 
1978...) and then reassess.

====

Charles T. Low
www.boatdocking.com

====

"Terry Spragg" <tspragg567nospam@rogers.com> wrote in message 
news:nqGdncHT_PO9NUbfRVn-qw@rogers.com...
> One should expect it to be somewhat better, and in no qualified hands, 
> ever the worse for care.
>
> My old zenith carb was worn so bad that the throttle shaft rattled on 
> idle, its' fibre end washers worn way out, delivering varying amounts of 
> vacuum leak into the intake manifold, which really made life with the old 
> girl an erratic thing, to say the least, particularly when lower power 
> settings were needed.  As well, a somewhat sticky needle valve must have 
> been able to stick either open or closed, mysteriously and capreciously. 
> It's better, now.
>
> Fixing a carburettor is an essential basic automotive and boating skill 
> which, thanks to induction fuel injection and computerised engine control, 
> is becoming a skill of the past. If your mech is dubious, you need a real 
> mech.
>
> A couple of small rubber "O" rings on the ends of the shaft, retained with 
> a little brass snare wire seems to have steadied the engine up 
> considerable.
>
> Trry K
Re: rough engine intermittent
#3839
Author: Kevin & Debbie
Date: Thu, 28 Jul 2005 22:54
56 lines
4349 bytes
Hi Charles,
I once owned a 1977 GMC van with a 350 carbureted engine. I bought it (ab)used and it used 1 quart of oil for 500 miles, 
I started using 20W-50 oil as the back plugs would foul with oil in the course of about 5000 miles, and I would have to 
pull them and clean them. It also would run rough if it was idled too much and would clear up once out on the highway.
I pulled the valve covers and found oil sitting there. The problem was the oil drain holes in the head were plugged and 
the oil was going down the valve stems into the piston chambers. I plunged out the holes with a coat hanger and the 
entire problem went away. I then got over 2000 miles to a quart of 10W-30 and the plugs never fouled again.
On this same vehicle I installed a GM professionally rebuilt carburetor and then immediately had to have it 
repaired/rebuilt by a local small engine place, who put the proper Power valve spring in.
FWIW.
Kevin

Charles T. Low wrote:
> Thanks, Terry,
> 
> A marine mechanic to me is a bit like a hairdresser to my wife - we have a 
> relationship, and I feel loyal. That might interfere with getting my carb 
> maintained, however, and I'll have to think about how to approach that. I'll 
> come up with something. Step number one will be to replace my distributor 
> cap, rotor and leads (they have to be specially ordered - old engine, 
> 1978...) and then reassess.
> 
> ====
> 
> Charles T. Low
> www.boatdocking.com
> 
> ====
> 
> "Terry Spragg" <tspragg567nospam@rogers.com> wrote in message 
> news:nqGdncHT_PO9NUbfRVn-qw@rogers.com...
> 
>>One should expect it to be somewhat better, and in no qualified hands, 
>>ever the worse for care.
>>
>>My old zenith carb was worn so bad that the throttle shaft rattled on 
>>idle, its' fibre end washers worn way out, delivering varying amounts of 
>>vacuum leak into the intake manifold, which really made life with the old 
>>girl an erratic thing, to say the least, particularly when lower power 
>>settings were needed.  As well, a somewhat sticky needle valve must have 
>>been able to stick either open or closed, mysteriously and capreciously. 
>>It's better, now.
>>
>>Fixing a carburettor is an essential basic automotive and boating skill 
>>which, thanks to induction fuel injection and computerised engine control, 
>>is becoming a skill of the past. If your mech is dubious, you need a real 
>>mech.
>>
>>A couple of small rubber "O" rings on the ends of the shaft, retained with 
>>a little brass snare wire seems to have steadied the engine up 
>>considerable.
>>
>>Trry K
> 
> 
> 
Re: rough engine intermittent
#3840
Author: Charles T. Low
Date: Fri, 29 Jul 2005 14:05
40 lines
3206 bytes
Thanks, Kevin,

I'm considering having the carb rebuilt, but have been warned that sometimes 
it ends up worse, even in experienced hands - or that such bad damage is 
found inside that it can't be salvaged.

Something like what you're suggesting makes sense ... I just have never 
personally looked into the guts of an engine enough to know quite exactly 
what you mean. But is the kind of thing you're suggesting something for 
mechanic, or could anybody do it? It seems to me that unbolting the covers 
and having a look wouldn't be beyond the average person's capability. Then 
you would need a gasket kit to put it all back together?

Charles

====

Charles T. Low
www.boatdocking.com

====

"Kevin & Debbie" <kevdeb@golden.net> wrote in message 
news:42E9622C.4020005@golden.net...
> Hi Charles,
> I once owned a 1977 GMC van with a 350 carbureted engine. I bought it 
> (ab)used and it used 1 quart of oil for 500 miles, I started using 20W-50 
> oil as the back plugs would foul with oil in the course of about 5000 
> miles, and I would have to pull them and clean them. It also would run 
> rough if it was idled too much and would clear up once out on the highway.
> I pulled the valve covers and found oil sitting there. The problem was the 
> oil drain holes in the head were plugged and the oil was going down the 
> valve stems into the piston chambers. I plunged out the holes with a coat 
> hanger and the entire problem went away. I then got over 2000 miles to a 
> quart of 10W-30 and the plugs never fouled again.
> On this same vehicle I installed a GM professionally rebuilt carburetor 
> and then immediately had to have it repaired/rebuilt by a local small 
> engine place, who put the proper Power valve spring in.
> FWIW.
> Kevin
Re: rough engine intermittent
#3841
Author: Kevin & Debbie
Date: Fri, 29 Jul 2005 22:00
57 lines
4561 bytes
Hi Charles
The actual R & R of the valve covers was easy enough and the cleaning of the drain holes was a no brainer, but to get at 
the covers to take them off my boat engines would be a rather large undertaking. The van engine wasn't too bad. I have 
no idea if you can still buy brand new carburetors or not, it may be an option. I had considered buying a brand new 
Holley back in 1980 but decided to go with the "Factory Fresh GM Rebuilt", which was junk. Apparently the most 
noticeable symptom of plugged drain holes was the puff of blue smoke that would come out of the exhaust pipe when I 
started the Van after it had sat for a while. I don't think I could see that on my I/O's but you might on your inboard. 
Just guessing.
I would mention my experience to your mechanic to get his opinion.
Good luck and have a great long weekend.
Kevin

Charles T. Low wrote:
> Thanks, Kevin,
> 
> I'm considering having the carb rebuilt, but have been warned that sometimes 
> it ends up worse, even in experienced hands - or that such bad damage is 
> found inside that it can't be salvaged.
> 
> Something like what you're suggesting makes sense ... I just have never 
> personally looked into the guts of an engine enough to know quite exactly 
> what you mean. But is the kind of thing you're suggesting something for 
> mechanic, or could anybody do it? It seems to me that unbolting the covers 
> and having a look wouldn't be beyond the average person's capability. Then 
> you would need a gasket kit to put it all back together?
> 
> Charles
> 
> ====
> 
> Charles T. Low
> www.boatdocking.com
> 
> ====
> 
> "Kevin & Debbie" <kevdeb@golden.net> wrote in message 
> news:42E9622C.4020005@golden.net...
> 
>>Hi Charles,
>>I once owned a 1977 GMC van with a 350 carbureted engine. I bought it 
>>(ab)used and it used 1 quart of oil for 500 miles, I started using 20W-50 
>>oil as the back plugs would foul with oil in the course of about 5000 
>>miles, and I would have to pull them and clean them. It also would run 
>>rough if it was idled too much and would clear up once out on the highway.
>>I pulled the valve covers and found oil sitting there. The problem was the 
>>oil drain holes in the head were plugged and the oil was going down the 
>>valve stems into the piston chambers. I plunged out the holes with a coat 
>>hanger and the entire problem went away. I then got over 2000 miles to a 
>>quart of 10W-30 and the plugs never fouled again.
>>On this same vehicle I installed a GM professionally rebuilt carburetor 
>>and then immediately had to have it repaired/rebuilt by a local small 
>>engine place, who put the proper Power valve spring in.
>>FWIW.
>>Kevin
> 
> 
> 
Re: rough engine intermittent
#3833
Author: Charles T. Low
Date: Thu, 04 Aug 2005 10:10
45 lines
3427 bytes
Thanks, Kevin,

I am certainly saving this information for future use.

In the meantime, however, I discussed rebuilding the carburetor with an 
engine rebuilder, and he interrogated me at length about my problem and 
found it very puzzling. He did say, however, that a simple explanation could 
be the richness or idle adjustment screws on the carb being out of whack (I 
having been advised elsewhere "not to go near that carb!"). I backed these 
two screws out a bit more (double-barreled carb) and the thing _seems_ to be 
working normally again!

There's also an idle-adjustment screw on the actual shift-cable linkage, but 
I'm talking about a spring-screw(s) lower down on the carburetor itself.

If it continues along like this, I'll perhaps still have the carb looked at 
over the winter, but for the moment I don't want to tamper with success.

Wish me luck!

Charles

====

Charles T. Low
www.boatdocking.com

====

"Kevin & Debbie" <kevdeb@golden.net> wrote in message 
news:42EAA705.4090600@golden.net...
> Hi Charles
> The actual R & R of the valve covers was easy enough and the cleaning of 
> the drain holes was a no brainer, but to get at the covers to take them 
> off my boat engines would be a rather large undertaking. The van engine 
> wasn't too bad. I have no idea if you can still buy brand new carburetors 
> or not, it may be an option. I had considered buying a brand new Holley 
> back in 1980 but decided to go with the "Factory Fresh GM Rebuilt", which 
> was junk. Apparently the most noticeable symptom of plugged drain holes 
> was the puff of blue smoke that would come out of the exhaust pipe when I 
> started the Van after it had sat for a while. I don't think I could see 
> that on my I/O's but you might on your inboard. Just guessing.
> I would mention my experience to your mechanic to get his opinion.
> Good luck and have a great long weekend.
> Kevin
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