Exhaust manifold fix or replace

« **on:** June 02, 2013, 06:59:46 PM »

Well had the boat out pretty much all day, had a great time and the boat ran great... near the end of the day I started to hear a loud noise and thought something worse (rod knock) but found this hole in one of my BBC exhaust logs.

So...
1) can this be repaired with welding?
2) anyone know what causes this?

I'm guessing it has something to do with the new exhaust gaskets and high temp sealant, or maybe I over torqued the bolts? Anyone seen this happen before?

« **Reply #1 on:** June 02, 2013, 07:03:31 PM »

Quote from: riefer jet on June 02, 2013, 06:59:46 PM

Well had the boat out pretty much all day, had a great time and the boat ran great... near the end of the day I started to hear a loud noise and thought something worse (rod knock) but found this hole in one of my BBC exhaust logs.

So...
1) can this be repaired with welding?
2) anyone know what causes this?

I'm guessing it has something to do with the new exhaust gaskets and high temp sealant, or maybe I over torqued the bolts? Anyone seen this happen before?

Looks like a lean burn through to me.

IMHO I would not attempt to have it welded, although it may be able to be fixed, it won't last too long, the aluminum looks compromised and was junk cast to begin with.

Is there a name on them?

Perhaps someone has a set for sale.

« **Reply #2 on:** June 02, 2013, 07:37:11 PM »

Crap. They say Hardin so I assume that's marine.

I installed a brand new quick fuel marine 750 and one of their regulators last month; would the spark plugs confirm a lean condition?

Appreciate the help

« **Reply #3 on:** June 02, 2013, 07:47:14 PM »

Here's the carb specs, if that helps

« **Reply #4 on:** June 02, 2013, 08:04:09 PM »

Quote from: riefer jet on June 02, 2013, 07:47:14 PM

Here's the carb specs, if that helps

I guess I should clarify my post. A lean burn through does nor necessarily mean the engine was running lean, it means the exhaust was lean, this could be something a simple as the timing being too retarded, previous damage, poor casting from the get....

I have a set of those, but tunnels on here wants them. There was another set on here not long ago...

Take a plug out and take a look, but in all honesty, since it idled for a bit, the readings will be near useless.

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« **Reply #5 on:** June 02, 2013, 08:49:24 PM »

Can you clarify tunnels?

Yea I was thinking carb lean. Could not having a mechanical advance on the distributor cause this? Current setup has a vacuum advance that isn't connected.

Yea I emailed a guy about another set. Being a newb to jets, are any brands or types better than others? Would switching to headers be an option? I'm not sure how the through hull headers compare to logs.

« **Reply #6 on:** June 02, 2013, 09:02:56 PM »

Quote from: riefer jet on June 02, 2013, 08:49:24 PM

Can you clarify tunnels?

Yea I was thinking carb lean. Could not having a mechanical advance on the distributor cause this? Current setup has a vacuum advance that isn't connected.

Yea I emailed a guy about another set. Being a newb to jets, are any brands or types better than others? Would switching to headers be an option? I'm not sure how the through hull headers compare to logs.

Lose the vacuum advance and get a distributor with a mechanical advance and run the loosest advanced springs. You really want the timing to be between about 32* and 36* advanced at above 2500 rpm and higher. (all in by 2500 rpm.)

As for the brand names of exhaust manifolds, I would consider Hardin one of the better ones out there.

"tunnels" is a member on here.

Headers are pretty cool, but not without their issues.

Depending on what you are going to be doing with the boat, if you are keeping with the closed motor deal, do yourself a solid and stick with the logs. JMHO

« **Reply #7 on:** June 02, 2013, 09:21:52 PM »

Awesome. Thanks for the help GT

« **Reply #8 on:** June 02, 2013, 10:06:08 PM »

Get a set of harman marine. They have a thick block at ports where the water will cool up to port. Like these....
http://www.ebay.com/itm/Harman-Marine-454-Exhaust-Manifold-Aluminum-Boat-Header-BBC-Big-Block-V-Drive-/271206044165?pt=Boat_Parts_Accessories_Gear&vxp=mtr&hash=item3f2523d205

« **Reply #9 on:** June 02, 2013, 10:17:57 PM »

Quote from: Your Mom on June 02, 2013, 10:06:08 PM

Get a set of harman marine. They have a thick block at ports where the water will cool up to port. Like these....
http://www.ebay.com/itm/Harman-Marine-454-Exhaust-Manifold-Aluminum-Boat-Header-BBC-Big-Block-V-Drive-/271206044165?pt=Boat_Parts_Accessories_Gear&vxp=mtr&hash=item3f2523d205

As much as I like the idea, you may have fitment issues because I believe the Harmin's are quite a bit wider.

GT

« **Reply #10 on:** June 03, 2013, 05:57:50 AM »

If I could get them to fit, are the snails universal?

« **Reply #11 on:** June 03, 2013, 07:50:40 AM »

Yes and if you can find a step down snail, you can remove it and lightly port to get a 3 1/2. Dont buy the cheapo green snail/log gasket. Jim Brock on this site sells custom composite that are way better.

« **Reply #12 on:** June 03, 2013, 01:15:34 PM »

Do you have any pictures of your setup Your mom? Thanks for the info

« **Reply #13 on:** June 03, 2013, 06:58:23 PM »

Heres a pic of mine but its ford...Harman marine.

This is a pic of the step down cut off...some will have two areas to mount the exhaust hose and the smaller step doen will be 2 7/8 and by cutting that off you get 3 1/2. Any help for flow on log style is good.

« **Reply #14 on:** June 04, 2013, 08:07:50 AM »

Ok here we go. Flame away.
No disrespect to GT Jets but if it were mine I would mill out the cancer and TIG weld a patch panel in there all while bolted up to a head or drilled/tapped ¾” plate to control warpage. However that is just me. Also this would save the pain in altering elbows, pipes and what have you. But that is just me.
Also was this boat run in salt water ?

« **Reply #15 on:** June 04, 2013, 11:52:04 AM »

I've only had it in freshwater, but I've also only owned it since September of last year.

I may try and weld it because if it doesn't work I'll be replacing them anyways. I'm more concerned if I need to change something else (timing, jetting, cooling, etc) to prevent this from happening again. Think I'll start with the timing and maybe a marine distributor with mechanical advance.

« **Reply #16 on:** June 04, 2013, 12:27:40 PM »

Quote from: TJS Nordic on June 04, 2013, 08:07:50 AM

Ok here we go. Flame away.
No disrespect to GT Jets but if it were mine I would mill out the cancer and TIG weld a patch panel in there all while bolted up to a head or drilled/tapped ¾” plate to control warpage. However that is just me. Also this would save the pain in altering elbows, pipes and what have you. But that is just me.
Also was this boat run in salt water ?

No disrespect taken at all TJS, the only reason I recommended NOT getting them welded is because nobody knows the integrity of the rest of the cylinders and I hate doing shit twice. Also, they're cheap to replace used if you think about it.

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« **Reply #17 on:** July 13, 2013, 07:48:56 PM »

Well I tried the cheap approach and had them welded. Guy did a good job, welds lots of cast aluminum. Unfortunately it blew out... I also have another exhaust leak. Seems like I have some really high back pressure in this thing... well on to plan B

« **Reply #18 on:** July 14, 2013, 01:50:44 PM »

I scored a set of Harman Marine manifolds and snails. What gaskets have you guys had luck with?

« **Reply #19 on:** July 17, 2013, 12:14:19 PM »

Quote from: riefer jet on July 14, 2013, 01:50:44 PM

I scored a set of Harman Marine manifolds and snails. What gaskets have you guys had luck with?

No gaskets, a light coating of Ultra Copper high temp silicone and be done.

If you do use gaskets, use solid copper Cometics or similar.

You need to have the best possible thermal contact between the head and the manifold to get them to last.

GT

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« **Reply #20 on:** July 17, 2013, 02:27:35 PM »

Thanks.

New question... how can you check air/fuel ratio on a motor with logs/snails? Is there a safe place you can drill to add sensors? I'm still concerned the motor is lean and therefore hot and don't want to ruin another set of logs or something worse inside the motor.

« **Reply #21 on:** July 17, 2013, 02:34:36 PM »

Quote from: riefer jet on July 17, 2013, 02:27:35 PM

Thanks.

New question... how can you check air/fuel ratio on a motor with logs/snails? Is there a safe place you can drill to add sensors? I'm still concerned the motor is lean and therefore hot and don't want to ruin another set of logs or something worse inside the motor.

In a situation like yours,I would use a spark plug mounted pyrometer.

The make one with a type k thermocouple that can be mounted on the spark plug.

An AFM will not work with wet exhaust.

GT

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« **Reply #22 on:** July 17, 2013, 04:40:27 PM »

What kind of temperature should I expect? Thanks