My FJ40 has Header issues (1 Viewer)

[Iron_Pig]

I've had it on the road about 3 weeks now, The engine just started idling very rough,then not at all. As I drove from a friends yesterday it would shut off at a stop sign,belch black smoke from the exhaust when it cranked. It even back-fired once while going down the road about 40m.p.h.
The Motorcraft 2BBl carb was always a bit troublesome so I suspected it first. I adjusted it enough to keep the motor running but it was rough and still had black smoke from the exhaust.
I thought I heard a valve tap,but found it to be an exhaust leak at the header/manifold gasket of my 2F motor. As it got dark outside I could actually see a tiny spark of flame as I peered at the header gasket area.
Tomorrow I'll start again,first tightening the bolts to spec.Should this be done in any exact order? What's the lb. torque,off-hand? Are these symptoms signs of something more serious such as the gasket already blown,valve burned,etc.?
I have heard that headers are notorious for such leak problems.Would I be better off just getting a stock exhaust manifold somewhere? Where would you go from here? ???

 

[CruisinGA]

Headers, especially the MAF ones are notorious for leaks. No personal experience there.
When I had a blown exhaust gasket I replaced it with two dry OEM ones from Spector and did not tighten the manifold bolts in any particular order. No leaks since. The two gaskets are to make up for imperfections in the manifold and head mating surface due to warpage, etc. Probably should have used some Copper RTV, didn't think about it then.
My first step would be to check the exhaust gasket, if blown replace with 1 or 2, if not blown just tighten the header and maybe some RTV and see what happens.

 

[Poser]

Sounds to me that the gasket is already burned out, and will need replacing, if you can see flame and sparks...sounds fun!

If you can find a stock intake and exhaust that is in useable condition, go for it. I would change them out together, as getting them to seal to each other, and to the block can be a real pain, if not impossible, minus some machining, which is probably what they are going to need anyways, but, you may get lucky. I would look for the later model three piece exahust manifold and intake combo, as these seem to stay sealed to the block better that the earlier one-piece set ups.

What gasket are you using to seal the intake and header? I have used the green SOR gaskets for many swaps without problems. Be sure that the headers are not warped at the mating surface, which if it is, will need to be machined flat again, and could be a major part of your problem.

I would tear it apart, and take a look at the mating surfaces, and see what is going on.

Good luck!

-Steve

 

[fsusteve]

I agree with Bailey, always use two gaskets with a header and tighten from the center out in a criss crossing pattern until snug. You may have an intake leak since the exhaust shares the gasket, that would account for the rough running. I use red RVT on the header/intake side just to make sure of no leaks.

 

[Poser]

Re-tourqe after it is warmed up. And I check, and have found loose nuts, even after a couple days, so check that out.

Realistically, if you verify that the mating surface of the header is square, and not warped, and if it is, you cut it down so that it is square again, you should not need two gaskets, but I do use the High temp, non-corrosive (does not stink) RTV on these set ups.

A friend purchased a used one piece header, and had to have it cut almost .250" to square it back up, so look there. Clean it up, and put a good strait edge on it, you will see the high and low spots...

-Steve

 

[IDave]

Which header do you have? The one piece MAF has the worst reputation. I got mine to work/seal, however, without any machining. Just like Bailey and fsusteve said, double gasket and high temp copper permatex. In my case the header was thinner than the intake manifold. Some people use cut washers (shaped like a "C" instead of an "O") to take up the space difference. I didn't need to with doing the other stuff. I tightened the bolts from the inside out and retorqued daily at first then less often until it was stable (maybe 4 times total). I haven't fiddled with it for 9 months (except to check) and no problems.

 

[offcamber40]

Im curious as to what type of header you are using as well. I just recently went round and round trying to fix exhuast leaks on mine. Idave suggested to me to use the copper rtv high temp silicone, and it worked quite well on my MAF headers. I ended up using the early style manifold gaskets that have the dividers between the exhaust ports on the gasket (as opposed to the later model ones with large holes). I double stacked two, only using RTV on the exhaust ports to ensure a tight fit on the intakes.. my question though is about the flames you are seeing. I dont think an exhuast leak alone would cause this type of running condition. To be belching black smoke and popping, combined with the flames out the header would be more likely a timing issue or possibly a burned valve (worst case senario, let hope its not that). Id double up your gaskets w/ RTV, check the timing, then run a compression/leak down test if the condition persisits. It may still be carb related too? Keep us posted.

Mike

 

[Iron_Pig]

Sorry,I don't know what kind of header I have.It was on the 2F when I bought the rig. I'll tighten everything to torque specs ,for starters. If it still leaks,I'll disassemble and see what I've got. Thanks for your help.