Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

Sign in to follow this  
smooth as glass

Now Cracked Exhuast Manifold

Recommended Posts

smooth as glass

After the head switch, waterpump and steering cable, I thought maybe I'd wax her up sit back and admire the work. Not to be! After a couple sets , smooth running and easy steering, I noted a bit of moisture on side of both exhaust manifolds, just slightly weeping from hair line cracks that I saw previously and caused me to pressure test before assembly. I guess we should have heated them when testing. Anyway with the new paint water is beading up, and then misting. Do you think some JB weld would seal it? And am I taking a chance of more cracks internal? They've both been leaking for some time just dripping done the side, (indicated by the staining before the new paint.) and then evaporating, at the bottom. So I hopin not to spend another 600 on exhaust manifolds. Opinions welcome.

Share this post


Link to post
martinarcher

My port side mani was dripping like that. JB weld was attempted and worked for a bit, but ended up leaking again. I was worried about it leaking on the inner jacket and causing a hydro lock condition so I wussied out and changed them. The best way to fix them with JB weld would be to "V" out the crack a bit with a die grinder to allow more JB weld to fill the void. Smearing it on the outside of the crack will not seal it. :no:

One thing to keep in mind, if your manifolds were pressure tested you already know more about your manifolds than I did. I was worried about age combined with my crack/leak.

Here's my research thread. I was after a bit of a performance upgrade as well as I was looking for aluminum manifolds. If your after cast manifolds you could end up much cheaper with a pair of GLM cast manifold.

Here's my exhaust project if your interested.

Good luck!

Share this post


Link to post
smooth as glass

Good stuff. Thanks so much, took me on my own research quest. Yours ended up lookin good! All still good? GLMs 1/2 OE, but sure are a lot of guys dissin them for quality control. you get what you pay for, my grand dad always said. So for now gonna try the weld and see! Thanks again.

Share this post


Link to post
Bozboat

After the head switch, waterpump and steering cable, I thought maybe I'd wax her up sit back and admire the work. Not to be! After a couple sets , smooth running and easy steering, I noted a bit of moisture on side of both exhaust manifolds, just slightly weeping from hair line cracks that I saw previously and caused me to pressure test before assembly. I guess we should have heated them when testing. Anyway with the new paint water is beading up, and then misting. Do you think some JB weld would seal it? And am I taking a chance of more cracks internal? They've both been leaking for some time just dripping done the side, (indicated by the staining before the new paint.) and then evaporating, at the bottom. So I hopin not to spend another 600 on exhaust manifolds. Opinions welcome.

For awhile there was a set of used monsoon manifolds for sale on this forum, I never saw that they sold. OP said they were in his garage taking up space for years.

Share this post


Link to post
jkendallmsce

After the head switch, waterpump and steering cable, I thought maybe I'd wax her up sit back and admire the work. Not to be! After a couple sets , smooth running and easy steering, I noted a bit of moisture on side of both exhaust manifolds, just slightly weeping from hair line cracks that I saw previously and caused me to pressure test before assembly. I guess we should have heated them when testing. Anyway with the new paint water is beading up, and then misting. Do you think some JB weld would seal it? And am I taking a chance of more cracks internal? They've both been leaking for some time just dripping done the side, (indicated by the staining before the new paint.) and then evaporating, at the bottom. So I hopin not to spend another 600 on exhaust manifolds. Opinions welcome.

Have you looked at any of the marine junk yards/recyclers??

350 is a pretty common engine, should be able to find a used set??

Although I have used JB Weld on lots of aluminum parts and it has never failed me.

Share this post


Link to post
martinarcher

Good stuff. Thanks so much, took me on my own research quest. Yours ended up lookin good! All still good? GLMs 1/2 OE, but sure are a lot of guys dissin them for quality control. you get what you pay for, my grand dad always said. So for now gonna try the weld and see! Thanks again.

Good man. I suggested them since they are cheap (cost wise) and I know you just finished a not so cheap project. I was leery about the quality as well which is why my boat is rocking the Stainless Marine stuff. Your grand dad knows his stuff.

Share this post


Link to post
Bozboat

Matt, When you change out the manifolds is there any concern about less back pressure burning up valves? Seems like less would be better, aircraft mechanic friend got all nervous when I showed him your exhaust project thread. Something about back pressure calculations bla bla, which sounded ominous to this rookie

Share this post


Link to post
martinarcher

Matt, When you change out the manifolds is there any concern about less back pressure burning up valves? Seems like less would be better, aircraft mechanic friend got all nervous when I showed him your exhaust project thread. Something about back pressure calculations bla bla, which sounded ominous to this rookie

That can be true for a poorly tuned engine. By allowing exhaust (burnt air and fuel) to exit the engine faster, your essentially increasing the amount of air that the carb has to pull in. If the engine is not able to get enough fuel to compensate for the additional air it can run lean, increase temps in the combustion chamber, and burn exhaust valves. This of course would be in extreme cases.

In my case that increase in air flow I don't believe is enough to outrun my 750CFM Quadrajet. A sign of running lean is a reduction in torque or low end grunt which many believe is caused by too little back pressure, but it is actually due to a lean burn condition (a side effect of high flow exhaust systems). Since my boat has as much or more torque than it did before the new exhaust I think i'll be OK. I also think adding water to the exhaust makes the possibility of eliminating enough back pressure to run lean pretty tough. Stainless Marine did their homework on this exhaust and has a great reputation for a reason.

If I end up being wrong, I'll throw a pair of Vortec manifolds, a high flow manifold, and a bigger carb on it and roll with around 330-350 hp. Thumbup.gif

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...