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nate
 
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Default Low RPM

ok,

350 gm mercruiser.

I had a burnt valve. I took the head in to the machine shop and had it
replaced. I put it back together, did the timing ect. It is running a lot
better, but doesn't seem to have the full power. On the engine it says that
the max rpm should be 4400 - 4800. Although I only seem to be getting 4200
at the most. Also it seems a little slugish out of the hole. I checked the
compression on all clyinders and they are all very good. (160-170). I feel
as though it might have something to do with the timing. I read in a book
that the timing mark should hit in the same spot everytime. It's pretty
close but seems to very about 2-3 degrees each time. Might this be the
issue?

Any thoughts on what the problem might be here?


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Cam setup timing?

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Gudmundur
 
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In article ,
says...

ok,

350 gm mercruiser.

I had a burnt valve. I took the head in to the machine shop and had it
replaced. I put it back together, did the timing ect. It is running a lot
better, but doesn't seem to have the full power. On the engine it says that
the max rpm should be 4400 - 4800. Although I only seem to be getting 4200
at the most. Also it seems a little slugish out of the hole. I checked the
compression on all clyinders and they are all very good. (160-170). I feel
as though it might have something to do with the timing. I read in a book
that the timing mark should hit in the same spot everytime. It's pretty
close but seems to very about 2-3 degrees each time. Might this be the
issue?

Any thoughts on what the problem might be here?



So, I am guessing it did run better back before the burnt valve, and gave
you more power. If you had the head off, then you must have had to adjust
the valve lash. Back off until you hear the tick-tick-tick, and then tighten
slowly until the ticking stops, and adjust 1/4 to 1/2 turn more. Also, play
with the ignition timing. It may be just a bit late, advance it a bit and
'road test it'. Listen for the ping of detonation, in case you advance to
far. Also remember an over advanced motor will often not start when hot, it
will actually kick backwards and try to rip the starter right off the
engine. If you feel the engine doesn't make the power it used to, a bit of
tweaking is in order. Hope the new head is the same as the old head. You
did say you replaced the head? 67CC chamber vs. 73CC chamber? Port sizes
differant?


  #4   Report Post  
nate
 
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Same head. It does make a very light ticking sound, but that sound does not
increase with throttle. Would advancing the timing be to the right or left
of the line? also, would the adjustment of the rocker arms cause this
issue? And one last thing, I did put new plugs (gapped them) & wires in it
too.

"Gudmundur" wrote in message
...
In article ,
says...

ok,

350 gm mercruiser.

I had a burnt valve. I took the head in to the machine shop and had it
replaced. I put it back together, did the timing ect. It is running a
lot
better, but doesn't seem to have the full power. On the engine it says
that
the max rpm should be 4400 - 4800. Although I only seem to be getting
4200
at the most. Also it seems a little slugish out of the hole. I checked
the
compression on all clyinders and they are all very good. (160-170). I
feel
as though it might have something to do with the timing. I read in a book
that the timing mark should hit in the same spot everytime. It's pretty
close but seems to very about 2-3 degrees each time. Might this be the
issue?

Any thoughts on what the problem might be here?



So, I am guessing it did run better back before the burnt valve, and gave
you more power. If you had the head off, then you must have had to adjust
the valve lash. Back off until you hear the tick-tick-tick, and then
tighten
slowly until the ticking stops, and adjust 1/4 to 1/2 turn more. Also,
play
with the ignition timing. It may be just a bit late, advance it a bit and
'road test it'. Listen for the ping of detonation, in case you advance to
far. Also remember an over advanced motor will often not start when hot,
it
will actually kick backwards and try to rip the starter right off the
engine. If you feel the engine doesn't make the power it used to, a bit of
tweaking is in order. Hope the new head is the same as the old head. You
did say you replaced the head? 67CC chamber vs. 73CC chamber? Port sizes
differant?




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nate
 
Posts: n/a
Default

You know I was thinking about it. When I did the timing there were 2 marks
on the flywheel, the org. factory mark and was that was scratched in. It
only seem to run ok when I used the scratched mark. But when I inserted the
distrutor, I used the factory mark to align to Top Dead Center. The 2 marks
are about a couple of inch's apart. Is this the problem? If so do I need to
reinsert the distributor at TDC (with the scratch mark), or can I just move
the timing a couple of inch's?



"Gudmundur" wrote in message
...
In article ,
says...

ok,

350 gm mercruiser.

I had a burnt valve. I took the head in to the machine shop and had it
replaced. I put it back together, did the timing ect. It is running a
lot
better, but doesn't seem to have the full power. On the engine it says
that
the max rpm should be 4400 - 4800. Although I only seem to be getting
4200
at the most. Also it seems a little slugish out of the hole. I checked
the
compression on all clyinders and they are all very good. (160-170). I
feel
as though it might have something to do with the timing. I read in a book
that the timing mark should hit in the same spot everytime. It's pretty
close but seems to very about 2-3 degrees each time. Might this be the
issue?

Any thoughts on what the problem might be here?



So, I am guessing it did run better back before the burnt valve, and gave
you more power. If you had the head off, then you must have had to adjust
the valve lash. Back off until you hear the tick-tick-tick, and then
tighten
slowly until the ticking stops, and adjust 1/4 to 1/2 turn more. Also,
play
with the ignition timing. It may be just a bit late, advance it a bit and
'road test it'. Listen for the ping of detonation, in case you advance to
far. Also remember an over advanced motor will often not start when hot,
it
will actually kick backwards and try to rip the starter right off the
engine. If you feel the engine doesn't make the power it used to, a bit of
tweaking is in order. Hope the new head is the same as the old head. You
did say you replaced the head? 67CC chamber vs. 73CC chamber? Port sizes
differant?






  #6   Report Post  
Gudmundur
 
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Default

In article ,
says...

You know I was thinking about it. When I did the timing there were 2 marks
on the flywheel, the org. factory mark and was that was scratched in. It
only seem to run ok when I used the scratched mark. But when I inserted the
distrutor, I used the factory mark to align to Top Dead Center. The 2 marks
are about a couple of inch's apart. Is this the problem? If so do I need to
reinsert the distributor at TDC (with the scratch mark), or can I just move
the timing a couple of inch's?


I would leave the distributor alone for now, at least as far as pulling it
out goes. If you can get the desired timing without the advance can hitting
anything you will be o.k.

I hope I am correct about your motor here, Turning the distributor
counter-clockwise will advance the timing. I like a lot of advance, but
you have to quit when you hear pinging under acceleration when the engine
is hot, and you have cheap fuel in it. Also, I find with a lot of
advance the engine is hard to crank over when it's hot. The spark occurs
to early and almost stops the motor dead while cranking. If you have
that much advance, back it off a bit. I time by ear and by feel, and
not with a light. A light gets me in the ballpark only. Every engine seems
to have a personality, and some like a ton of advance, others don't, and
none seem to run at their peak using the factory setting.

As for the 'ticking', I was refering to the click-click-click of a
to loose rocker adjustment. I very very slowly adjust mine looser until
they very lightly start clicking, then very slowly adjust tighter about
1/3 turn past where they stop ticking. Never more than 1/2 turn.
Of course you do this one rocker at a time. If they are all clicking you
can't tell what's going on. I made a very special valve cover with eight
3/4 inch holes punched directly above the rocker studs. I can adjust my
valve train all day long, and never spill one drop of oil.

Hope all of this helps.


  #7   Report Post  
nate
 
Posts: n/a
Default

Gundmundur,

Thanks for the tips. I advanced the timing a couple of inch's this time
(instead of just a few º). I played around with until until I got the best
performance. It seems to be running really good right now. But I still
have that ting ting ting. If I adjust the rocker arms witht he engine
running, is oil going to go everywhere?

"Gudmundur" wrote in message
...
In article ,
says...

You know I was thinking about it. When I did the timing there were 2
marks
on the flywheel, the org. factory mark and was that was scratched in. It
only seem to run ok when I used the scratched mark. But when I inserted
the
distrutor, I used the factory mark to align to Top Dead Center. The 2
marks
are about a couple of inch's apart. Is this the problem? If so do I need
to
reinsert the distributor at TDC (with the scratch mark), or can I just
move
the timing a couple of inch's?


I would leave the distributor alone for now, at least as far as pulling it
out goes. If you can get the desired timing without the advance can
hitting
anything you will be o.k.

I hope I am correct about your motor here, Turning the distributor
counter-clockwise will advance the timing. I like a lot of advance, but
you have to quit when you hear pinging under acceleration when the engine
is hot, and you have cheap fuel in it. Also, I find with a lot of
advance the engine is hard to crank over when it's hot. The spark occurs
to early and almost stops the motor dead while cranking. If you have
that much advance, back it off a bit. I time by ear and by feel, and
not with a light. A light gets me in the ballpark only. Every engine seems
to have a personality, and some like a ton of advance, others don't, and
none seem to run at their peak using the factory setting.

As for the 'ticking', I was refering to the click-click-click of a
to loose rocker adjustment. I very very slowly adjust mine looser until
they very lightly start clicking, then very slowly adjust tighter about
1/3 turn past where they stop ticking. Never more than 1/2 turn.
Of course you do this one rocker at a time. If they are all clicking you
can't tell what's going on. I made a very special valve cover with eight
3/4 inch holes punched directly above the rocker studs. I can adjust my
valve train all day long, and never spill one drop of oil.

Hope all of this helps.




  #8   Report Post  
Gudmundur
 
Posts: n/a
Default

In article ,
says...

Gundmundur,

Thanks for the tips. I advanced the timing a couple of inch's this time
(instead of just a few º). I played around with until until I got the best
performance. It seems to be running really good right now. But I still
have that ting ting ting. If I adjust the rocker arms witht he engine
running, is oil going to go everywhere?


I have an old valve cover that I used a Greenlee 3/4 inch punch to
place 8 holes exactly centered over the rocker studs. This allows my
5/8 inch deep well socket to fit down over the adjustment nut.

When you adjust the rocker, back off very slowly until you hear the
tick-tick-tick. Then very slowly turn the adjustment clockwise until
the ticking stops. Proceed to adjust 1/4 to 1/2 turn tighter, but not
more than 1/2!

You will develope a feel for this adjustment. Your lifters are oil
filled hydraulic, and the whole point is that they 'compensate' for
normal wear in the valve train. While you are adjusting they are
dynamically changing. If you adjust to loose, they will reach the end
of their travel, and you will hear the ticking. If you adjust to tight,
the engine will idle rough as hell, not take a load at low rpm, and
probably burn the valves from not seating completely at high rpm.

A slight tick-tick-tick at very low idle rpm is tolerable and even
somewhat normal, so long as the ticking stops almost as soon as the
engine is brought above idle.

Two things to remember on Chevy rocker adjustment. 1 the studs are
pressed in and known to back out. If after proper adjustment, you
run the engine for several hours at high rpm and the ticking comes
back and sounds more like loud clacking, look for a stud which is
no longer anchored firmly in the head. 2 the adjustment is supposed
to be self locking, but if you play with the adjustment to much it
loses the ability to self lock and will begin to drift to the loose
side followed by the return of clicking noises. This is why all
serious high endurance engines change over to screw in studs and
jamnut adjusters. Some even run 'rocker stud girdles'.

Best wishes. Writing this reminds me that I need to go spend some
time under the hood of my tow vehicle. 1948 streetrod pickup truck.
Haven't messed with anything under the hood in 5 years other than
oil changes. Think it's about time for plug wires and a tune up.

Gummi (Icelandic horseman now boating in America)

  #9   Report Post  
nate
 
Posts: n/a
Default

Oh ya, and the ping doesn't get worse when I speed up. In fact I can only
hear it when we're idle.

"Gudmundur" wrote in message
...
In article ,
says...

You know I was thinking about it. When I did the timing there were 2
marks
on the flywheel, the org. factory mark and was that was scratched in. It
only seem to run ok when I used the scratched mark. But when I inserted
the
distrutor, I used the factory mark to align to Top Dead Center. The 2
marks
are about a couple of inch's apart. Is this the problem? If so do I need
to
reinsert the distributor at TDC (with the scratch mark), or can I just
move
the timing a couple of inch's?


I would leave the distributor alone for now, at least as far as pulling it
out goes. If you can get the desired timing without the advance can
hitting
anything you will be o.k.

I hope I am correct about your motor here, Turning the distributor
counter-clockwise will advance the timing. I like a lot of advance, but
you have to quit when you hear pinging under acceleration when the engine
is hot, and you have cheap fuel in it. Also, I find with a lot of
advance the engine is hard to crank over when it's hot. The spark occurs
to early and almost stops the motor dead while cranking. If you have
that much advance, back it off a bit. I time by ear and by feel, and
not with a light. A light gets me in the ballpark only. Every engine seems
to have a personality, and some like a ton of advance, others don't, and
none seem to run at their peak using the factory setting.

As for the 'ticking', I was refering to the click-click-click of a
to loose rocker adjustment. I very very slowly adjust mine looser until
they very lightly start clicking, then very slowly adjust tighter about
1/3 turn past where they stop ticking. Never more than 1/2 turn.
Of course you do this one rocker at a time. If they are all clicking you
can't tell what's going on. I made a very special valve cover with eight
3/4 inch holes punched directly above the rocker studs. I can adjust my
valve train all day long, and never spill one drop of oil.

Hope all of this helps.




  #10   Report Post  
calhoun
 
Posts: n/a
Default


"nate" wrote in message
...
ok,

350 gm mercruiser.

I had a burnt valve. I took the head in to the machine shop and had it
replaced. I put it back together, did the timing ect. It is running a
lot better, but doesn't seem to have the full power. On the engine it
says that the max rpm should be 4400 - 4800. Although I only seem to be
getting 4200 at the most. Also it seems a little slugish out of the hole.
I checked the compression on all clyinders and they are all very good.
(160-170). I feel as though it might have something to do with the
timing. I read in a book that the timing mark should hit in the same spot
everytime. It's pretty close but seems to very about 2-3 degrees each
time. Might this be the issue?

Any thoughts on what the problem might be here?

You have had this running 44-4800 at some time? If it never ran that speed
than you need a smaller pitch prop.
If it did run at speed and all you changed was the head than timing may be
an issue. Advance it 2 degrees at a time till you hear knock. See if that
picks it up a bit.
You did follow the timing instructions and remove/plug correct hoses or
disconnect certain wires (you didn't mention the year so I don't know what
kind of ignition you have)




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