Netters,
For the past couple of weekends I've been trying to get the leaks at my
OEM exhaust manifolds fixed but have not been successful yet. I've
started thinking about headers but I have a question for the group.
First, a little background on what I've done so far.
I've removed the manifolds, had them ground flat at their port flanges,
inspected the heads which look to be in good shape without pitting
around the exhaust ports, repaired one broken center port bolt by
drilling it out of the head and re-tapping the hole, installed a set of
new SCE copper gaskets from Bushkirk's (embossed side out and without
RTV sealant), and, using new bolts and thick washers with Never Seize,
carefully torqued the manifolds in place with a torque wrench set at 25
ft.lbs. Next I started the engine and after it warmed up listened for
leaks using a stethoscope. Unfortunately, both sides had leaks at the
bottom of the center ports---arrggggh!. I applied more torque (35
ft-lbs) to the three center port bolts which seemed to lessen the leaks
somewhat but did not stop them.
I plan to next drive the coach on my 50 mile local mountain run and then
check to see if the leaks get worse and if bolts need re-torquing.
However I don't expect the leaks to go away. It could be that the heads
are warped and no amount of torquing the bolts will seal the gap, but
again the surfaces around the ports look to be in good shape without
pits.
I think that the reason the center ports do not seal well is in part
because of the bolt pattern. These ports do not have a bolt at the
bottom, relying on the two at either side and one at the top to make the
pressure to squeeze the gasket. My question is why is it that headers do
a better job sealing when they use the same bolt pattern to seal the
center ports?
Phil Stewart
'76 Transmode, TN
For the past couple of weekends I've been trying to get the leaks at my
OEM exhaust manifolds fixed but have not been successful yet. I've
started thinking about headers but I have a question for the group.
First, a little background on what I've done so far.
I've removed the manifolds, had them ground flat at their port flanges,
inspected the heads which look to be in good shape without pitting
around the exhaust ports, repaired one broken center port bolt by
drilling it out of the head and re-tapping the hole, installed a set of
new SCE copper gaskets from Bushkirk's (embossed side out and without
RTV sealant), and, using new bolts and thick washers with Never Seize,
carefully torqued the manifolds in place with a torque wrench set at 25
ft.lbs. Next I started the engine and after it warmed up listened for
leaks using a stethoscope. Unfortunately, both sides had leaks at the
bottom of the center ports---arrggggh!. I applied more torque (35
ft-lbs) to the three center port bolts which seemed to lessen the leaks
somewhat but did not stop them.
I plan to next drive the coach on my 50 mile local mountain run and then
check to see if the leaks get worse and if bolts need re-torquing.
However I don't expect the leaks to go away. It could be that the heads
are warped and no amount of torquing the bolts will seal the gap, but
again the surfaces around the ports look to be in good shape without
pits.
I think that the reason the center ports do not seal well is in part
because of the bolt pattern. These ports do not have a bolt at the
bottom, relying on the two at either side and one at the top to make the
pressure to squeeze the gasket. My question is why is it that headers do
a better job sealing when they use the same bolt pattern to seal the
center ports?
Phil Stewart
'76 Transmode, TN
