Exhaust manifold split crack ?

[TheSportsmanDodger]

318 manifold cracked in half still attatched to engine with a good exhaust gasket seal.

Things to take into consideration:

Split is in between last two cylinders on the passenger side standing from the inside.

What is the 318 OEM temp at the eexhaust manifold?

Fillers and epoxies anyone?


Go.

Ideas?

[cosmic]

high nickel weld rod for cast iron will do it. not for to long. till it cracks again. be very careful not to hit the valve cover. been there done that.
this might hold ya off until you can afford a new manifold.

[TheSportsmanDodger]

I can weld it my self my issue is filling the crack first so Iwon't blow up in the welding process

[Lefty]

Use a brass drift as a backer behind where you will be welding (manifold has to be removed, and drift inserted into the port.), then weld with a high nickel rod made for welding cast iron. be sure to grind the crack opening to a v shape first, and it will likely takes a few passes to fill the crack totally. brass won't stick to the welded area, but it will prevent blow out from the back side. Also, be sure to drill a small hole at each end of any cracks to relieve stress or it will quickly re-crack.

[Froggy1936]

Cast iron should be heated very hot before welding . Frank

[cosmic]

The new style rods don't need heat any more. in the old days you would heat and then slowly cool. either by putting in a oven and slowly turning it down or wrapping in insulation. the new products don't need that step any more. Sodel SU89 rod. I call it the magical rod.
If the manifold is that bad just get a new one. I  hate to be the bad guy but that's just to far gone. no welding is going to help and even if you did. it wont last.
Im sorry I don't no of a product you can jam in there. those manifold just get to hot.

[Oz]

Do you have the welding equipment?  Or know someone who would do it for you cheaply?  If not, then the only option left is to replace it.

[Froggy1936]

Ah ha modern day improvements i did not know that existed. There are heavy duty manifolds available. And headers even with a single exaust is another option ! I know of no JB Type material that will do the job .  In total darkness on a long pull these manifolds will glow dull red ! They get very hot ! Frank

[cosmic]

Oh I forgot to say that I welded a Toyota corolla manifold 5 years ago and its still holding strong (but this style manifold doesn't get as hot). How ever when it came to my 440 it just kept cracking over time. I don't know about the 318, but franks said they also glow red hot.
Now please correct me if im wrong here. I was told by a senior fellow that when im driving down the hwy and say stop for fuel. If the engine is just instantly turned off that the manifolds cool down from red hot, to fast, and this is when they crack. I was told that you should let the engine idle for a minute or two, in order to let the temp cool down before cutting the heat to the manifolds completely.   
I now do this every time. it was such pain in the neck to change the manifold. I broke every bold.

[legomybago]

I've always been a firm believer in letting the rig idle for a period before shutting it down...I read somewhere (I think this forum) that letting an engine run idle before shut down, was bad on the manifolds? I dont believe that myself. Keep the antifreeze pumping through the engine to help with heat soak (my opinion).

We had an issue with the 86' P30, that when you pull off the highway and quickly grab fuel, start her back up and hit the road...bam! vapor lock! But if you let the engine run for a couple minutes after start up (engine temps cool down), then take off, it ran great. But now we have an electric fuel pump with the by-pass check valve, shouldn't ever vapor lock when thats systems on. We will see this year when it's 90 degress + outside....

[tiinytina]

Can be a good excuse to put on a nice set of headers...   Gone blew her small cracked manifold into a big cracked (sounded like dump truck) manifold when she backfired due to a bad connection onto the rotor cap, blew a seam out completely on that muffler as well...  now she sounds like  Harley with the Banks headers on her..... and she runs cooler too. 

[legomybago]

Headers with a cold air intake, like a Banks kit, is awesome on a p30. I can't put headers on my FMC due to too much radiant heat off of the headers. The rear engine compartment doesnt have air flow like a front engine set-up. I've been looking for an P30 rig thats being parted out that has a Banks Kit, and a Gear vendor up for grabs...hard find though.

[Stripe]

I thought those FMCs had a front air dam underneath just in front of the engine to direct air up into the compartment?  If I'm wrong wonder if that kind of thing is doable.

[legomybago]

No air dam...damn. After market side scoops! I have custom made air scoops underneath on the power steering and tranny coolers that provide air and keep them protected from rocks etc..

They are cooled by a reverse rotation fan blades, that blow engine compartment air out through the radiator and shrowds towards the back of the coach. The coaches have a lot of ambient heat build up in the engine compartment so a really good engine cooling system is essential. People have tried headers, and they create too much heat. Mine sits and idles at 180, but I havent had it out in the heat or hard pulls yet to really know how it's going to react. I still have the HUGE original brass radiator...I will update the rad in the future....  Hm?

[TheSportsmanDodger]

Tsh* Negative*

[Oz]

I've always been a firm believer in letting the rig idle for a period before shutting it down...I read somewhere (I think this forum) that letting an engine run idle before shut down, was bad on the manifolds?

I know you didn't read that here.  What you read is the opposite.  After driving, do not shut the motor off immediately.  let it idle down for a few minutes so the exhaust manifolds can cool down gradually.  It's the rapid cooling which can cause warping and cracks.

Now, back to any options out there about repairing the cracked-in-half 318 manifold this young man has.

So far, it looks like there really aren't any which really wouldn't be any better than just getting another one and replacing it.  As I originally said.
Some things just can't be cheaply fixed and expected to perform like a correct repair.  Looks like this is one of them.

Options appear to be: remove the cracked manifold and have it welded or buy a replacement.

[joev]

I agree with you he will just have to find another manifold
ANYBODY OUT THERE WITH A SPARE MANIFOLD please come forward

[legomybago]

"Come here manifold!, Come on boy!, Thats a gooood manifold"....

[Froggy1936]

Cooling down , Whenever the engine is operating at full throttle there is unburned mixture leaving the Clyinder This fuel continues to burn on its way out thru the manifolds creating way more than normal exaust heat . Allowing the engine to idle (actually it should be held at about 1000 RPM ) to help with coolant flow and air flow from the fan  For a few min . All those cracking sounds you hear are metal flexing as it cools . The time wasted doing this properly is opposed to finding a new part later And installing it along with the broken studs/ bolts . So wich is better ? Besides you can look at the scenery!  Frank

[legomybago]

Maybe Dave can come up with a schematic for an "engine cooler downer button"....

[DaveVA78Chieftain]

Nay.  This one is all on the operator 

[ClydesdaleKevin]

Best bet is to find a used manifold, or get headers.  Any other option is just a temporary fix that will lead you to more cracks, and then still having to buy a new manifold or headers.

Kev