I have a rebuilt 350 2piece rear seal that leaked from the get go .The motor is for my boat .The crank has a slight grove were the seal rides . The grove lines up with a offset seal that felpro makes . They the builder installed a blue felpro seal that rides in the normal location . So I pulled the motor back out an installed felpro 2912 seal . motor does not leak at ideal but around 2200rpm plus the seal starts to leak a dime size drop every 2 seconds . So fustrated I pulled the pan an seal back off. IS it a seal problem or could it be back pressure . The motor did not come with a pcv system ,Iam using high volume pump . vortec heads . felpro marine cam .I have been told the blue seal is softer so Iam planning on using a blue seal again . motor only has 30 hours on it .Builder is no help I am on my own. I am running the motor out of the boat till I get the problem fixed. Motor has 2 breathers that go to the spark arester. I need help ..
rear seal leak
- Thread starter jokswgn
- Start date
MYBAD79
Moderator
just two breathers and no vacuum line to the crankcase ?? The PCV hose might not be the solution but it's worth trying.... it's less than $20 in parts and it might fix the issue....
if it's just a slight groove - why did they not just polish it (too deep??) ???
If it doesn't leak at idle the seal seems to work fine.... again, try the PCV before you tear stuff apart....
GL
mrvette
Phantom of the Opera
I don't recall ever seeing a PVC system on a boat engine, they are never run under any meaningful intake vacuum, the two lines, one from each V cover to the flame arrestor are all I have ever seen....
when you run the engine, is it on a stand, or hooked to the outdrive??
do you have an vibration when hooked to the outdrive?? some friends just went through that, it can be either the gimble bearing or the universal joint....
in their case the gimble mount for the bearing is heavily corroded also, but still in use....
BTW, Welcome to the motley crew of the Flying Dutchmen....
:yahoo:
when you run the engine, is it on a stand, or hooked to the outdrive??
do you have an vibration when hooked to the outdrive?? some friends just went through that, it can be either the gimble bearing or the universal joint....
in their case the gimble mount for the bearing is heavily corroded also, but still in use....
BTW, Welcome to the motley crew of the Flying Dutchmen....
:yahoo:
The red 2912 is your best seal when others leak.
If you have oil past the seal, try polishing as mentioned or adding vacuum assited venting like a pcv or the breather lines.
If a new rebuild, give it a chance to seat better for less blowby.
Depending on rings and hatch, sealing might take a little longer.
If you have oil past the seal, try polishing as mentioned or adding vacuum assited venting like a pcv or the breather lines.
If a new rebuild, give it a chance to seat better for less blowby.
Depending on rings and hatch, sealing might take a little longer.
we have been running the engine on a stand . motor has around 20 hours on the water running . I hope a pcv valve does the trick.if not aleak down test will be done after that not sure what to do. Can the crank be polished in the block. thanks for your info.. One more thing that I found to be weird is when the motor is running above 2000 rpm it would spit oil out from the distributor gasket at the manifold ..an the clamp was tight
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TimAT
Addict, Cruise-In Bird-Run 1 Veteran
Are you installing the rear seal with sealant on the cap at both sides of the seal and along the edge where the cap mates to the block? No sealant ON the ends of the seal. Use the little plastic "spoon" to install both halves of the seal.
mrvette
Phantom of the Opera
tim I used hylomar on block an cap on the edge .I did put a dap on the seal .that could be my BIG mistake ... I did use the spoon the seal had no cuts when i removed it .
THE motor is out an running no leaks are visable with baby powder on back of motor . Only leak found was the distributor the mounting gasket would spit oil out at high rpm . the gasket is very soaked with oil.cam plug is not leaking galley plugs no leak .
mrvette
Phantom of the Opera
THE motor is out an running no leaks are visable with baby powder on back of motor . Only leak found was the distributor the mounting gasket would spit oil out at high rpm . the gasket is very soaked with oil.cam plug is not leaking galley plugs no leak .
I never got into it, but there is something about a SBC dizzy that involves a oil passage to the passenger/right side of the engine? think I remember that correctly....and so if you are leaking oil at the dizzy, I wonder how that top bearing is set and the amount of shims on the dizzy housing/shaft...that maybe it's not tight on the maifold for maybe too many shims under the dizzy housing to the dizzy gear....??
I have played with this a bit, certainly no expert, but maybe take a look, because for some reason the intake mani is lo on the block the dizzy will never really seal on the mani as it's riding on the oil pump shaft...??
:surrender::twitch:
big2bird
Charter Member, Founder Bird-Run, Cruise-In Bird-R
THE motor is out an running no leaks are visable with baby powder on back of motor . Only leak found was the distributor the mounting gasket would spit oil out at high rpm . the gasket is very soaked with oil.cam plug is not leaking galley plugs no leak .
I never got into it, but there is something about a SBC dizzy that involves a oil passage to the passenger/right side of the engine? think I remember that correctly....and so if you are leaking oil at the dizzy, I wonder how that top bearing is set and the amount of shims on the dizzy housing/shaft...that maybe it's not tight on the maifold for maybe too many shims under the dizzy housing to the dizzy gear....??
I have played with this a bit, certainly no expert, but maybe take a look, because for some reason the intake mani is lo on the block the dizzy will never really seal on the mani as it's riding on the oil pump shaft...??
:surrender::twitch:
The dizzzy completes the oil galley for the lifters on the (drivers?) side. I suspect that blowing oil out the rear seal and dizzy at speed is excessive CC pressure as well.
And no, your not gonna polish the crank installed.
SmokinBBC
Well-known member
Here is some more info on the crankcase pressure and how Davis Unified solves it for their dizzy. Got down to topic 4.
http://www.performancedistributors.com/technical.htm
Bird...have you ever tried this on any of your dizzy builds?
I have the new rear seal. I am putting it back together on thrusday .I will post my progress. thanks for the imput . My distributor is a mallory marine. If the seal does not cure my main seal leak I will have to say my crank needs to come out . I have run out of ideas . I will do a leak do test .Thanks Darren..
big2bird
Charter Member, Founder Bird-Run, Cruise-In Bird-R
I drill them when requested.
TimAT
Addict, Cruise-In Bird-Run 1 Veteran
Here's another idea- pull a little vacuum on the engine while it's running on the stand and see if that dries it up. Or give it a little pressure (static) setting there and see if you can determine exactly where it's coming from.
A little vacuum can be a good thing for several reasons- one of them is it'll help ring flutter- keep the rings set solidly in the bore and piston ring lands.
A little vacuum can be a good thing for several reasons- one of them is it'll help ring flutter- keep the rings set solidly in the bore and piston ring lands.
mrvette
Phantom of the Opera
Years ago, I had a Pontiac 455 with a persistent rear main leak, and so the machine shop had subbed in a Caddy 500? engine rear main seal....it was a wire reinforced neoprene 2 piece seal, with the ends supposed to mate perfectly round of course...well, it wasn't....it drove me krazy for a while there, I finally got pissed enough to dump some ten quarts of thin oil in the crank with it on the hook, propped that SOB up by the snout, and watched....sure enough....
so on the stand upside down a bunch of times, damned if that friggin' seal was going to kick my ass again....
finally got cagey/pissed enough to really look close as to how/where it was leaking the two halves of the seal did NOT make a round seal, it was OVAL, and so then clamped with the main cap, the seal never really ever mated with the crank on top and bottom, I finally miked the damn setup upon spotting the oil tracks, and a dap of RTV on the ends, bolted it down, and cured the problem...
I wonder if maybe something similar is happening here.....
:sos::sweat:
so on the stand upside down a bunch of times, damned if that friggin' seal was going to kick my ass again....
finally got cagey/pissed enough to really look close as to how/where it was leaking the two halves of the seal did NOT make a round seal, it was OVAL, and so then clamped with the main cap, the seal never really ever mated with the crank on top and bottom, I finally miked the damn setup upon spotting the oil tracks, and a dap of RTV on the ends, bolted it down, and cured the problem...
I wonder if maybe something similar is happening here.....
:sos::sweat:
Thanks for all the help . Ran the motor for about a hour 2000 to 3000 rpms no leaks finally . Tim thanks for you post on main seals I used that to the the t.I installed a2900 felpro seal. Replaced the distributor gasket mallory used a rubber gasket installed a felpro blue gasket no leaks .. I did use hylomar on the cap an block .Time to go chase tuna . thanks darren ....
