Exhaust Manifold Advice

[Highdesertrat]

 

Hello I am new to the forum and to Datsuns and have recently purchased a 1978 620 17ft Sunrader with a cracked exhaust manifold. I was originally hoping to fix an exhaust leak and upon removal found out the manifold was in two pieces held together by a hose clamp and perhaps something like JB Weld. I addition one of the flanges has broken off. Having a whale of a time trying to find an inexpensive replacement. Tempted to order a shorty header from Top End performance for $179 , however it is uncoated and looks like it would require having an exhaust shop weld up connection to the downpipe. Not sure how much this would be but guessing $150 to $200? Any ideas and advice would be greatly appreciated

[ggzilla]

The stock cast iron manifolds usually don't break and are much more reliable than a tubular header.

 

Only $25 at Pick-n-Pull with three Oregon locations.

[Spades]

my advice is stay away from headers on motor homes. They almost always crack, even good ones that are thermally wrapped...you can expect a non coated and wrapped header to raise under hood temperatures. I would go with a Chinese cast steel manifold before a header on a rig like that.

 

I know there are still exhaust manifolds for these around that are stock and not cracked...and I would imagine cheap since most people install headers on their L20's.

 

If you have to go with a header, get one that is ceramic coated, if you cant afford that, then buy some Rustoleum high temperature ceramic paint and bake it as per directions. Then buy some thermal wrap and wrap that sucker up!

[Z-train]

Wrapping a header voids all warrantees.Really,REALLY not a good idea.

[datzenmike]

Oregon????? You are in the middle of L series land. Go to a few local junk yards/wreckers and find a '78-'79 620, '80 (only) 720, '79 A-10 (later 510), '78-'79 S10. (first gen 200sx} These will have the W58 round exhaust port heads and matching round port exhaust manifolds that will fit your '78.

 

Take note that many motors are swapped by now and the '77 and earlier manifolds won't work on yours. The earlier exhausts are bolted to the bottoms of the intakes and you don't want those. You know what yours looks like so just be sure. Some yards have half off days but I wouldn't expect you to pay more than $25-$40 and very likely much less.

 

Just like yours, there is a small S shaped metal pipe connected to the main down pipe and up to the intake manifold. If this is difficult to remove hack-saw it off leaving about 2". This can later be squashed flat with vice-grips and folded over to prevent leaks. On top of the intake there is a sealed pipe running front to back with much smaller individual pipes going down into each exhaust port. These can also be cut and flattened to seal them. This will give you a replacement exhaust manifold with disabled EGR and AIR injection.

[ggzilla]

How to avoid teh cracking? My header cracked coming home from Blue Lake (at the header flange of #4 pipe. It's the only non-stock part on the engine, so I'm ready to put the cast iron manifold back on. Except that it sounds kind of neat with the crack, like a locomotive or something.

[Spades]

Wrapping a header voids all warrantees.Really,REALLY not a good idea.

 

 

depends on the manufacturer. some manufactures stand behind their steel and welds, some don't. the reason some manufacturers won't warranty their headers after wrapping is because their welds will not stand up to the extra heat that is trapped by the thermal wrap...another reason is if people improperly wrap them, or they do not use a waterproof protectant over the wrap to ensure it is water tight.

 

So...not a good idea? Debatable. Cooler engine temperatures, more horsepower, ect...drawback is if you buy a cheapo header, it may pop welds, but lets be honest, that sucker will break anyway, and I have yet to see thermal wrap destroy a header that was of even decent quality. Maybe someone else can offer more input than what I have seen or I am aware of, but what I do know is, small engine...camper-loaded truck...header...yeah, been there, seen that, and the customer always comes back because it overheats on hills. How do you think the factory manifold cracked?

 

The motorhomes w/ headers I have worked on with properly applied thermal wrap seem to last longer and don't tend to pop welds, warp, or blow manifold gaskets. I know companies put the disclaimers on their labels about thermal wrap increasing weld temperature, but the truth is, a motorhome engine is usually overworked from the start, and without thermal wrap, the headers heat the engine bay up to the point where the cooling system cant keep up, and the motor home starts overheating and pinging, then EGT's go through the roof. Maybe my real world experience is co-incidental, but I have yet to replace exhaust components on a properly sealed thermal wrapped header setup, where as we often see motor homes and pickups used for towing in for cracked/warped headers, blown gaskets, or the "mysterious overheating issue that started the summer after installing my new pace setters"...but again, I may be wrong.

[Highdesertrat]

Thanks everyone for the advice. Searched every Oregon junkyard and finally found a manifold in Euphrata Wa , and had it shipped to me over the weekend. However it appears that it may possible be from a later model? There is some sort of exhaust valve that is not present on mine. I am wondering if I should take it to the welding shop and have some sort of block off plate installed ? Also if i cut and flatten the EGR pipe will this cause any drive ability issues? It appears a previous owner cut and flattened the individual air injection pipes running into the manifold.Here are a couple of photos of the old cracked manifold and the latest junkyard find.

[bbqbill]

you cnn get plugs from a a/c shop ,just take one out of your manafold to compair.i have the same manafold on my 76,the valve is bolted to the intake to help during cold warm up.

[datzenmike]

Oregon????? You are in the middle of L series land. Go to a few local junk yards/wreckers and find a '78-'79 620, '80 (only) 720, '79 A-10 (later 510), '78-'79 S10. (first gen 200sx} These will have the W58 round exhaust port heads and matching round port exhaust manifolds that will fit your '78.

 

Take note that many motors are swapped by now and the '77 and earlier manifolds won't work on yours. The earlier exhausts are bolted to the bottoms of the intakes and you don't want those. You know what yours looks like so just be sure. Some yards have half off days but I wouldn't expect you to pay more than $25-$40 and very likely much less.

 

This is a '75-'77 exhaust manifold.You need a '78-'80.

 

Send back and next time tell them you want the type that is not bolted to the intake.