Tons of Exhaust Manifold Leaks

[Subzero]

My exhaust manifold gaskets are not the right size, something I noticed before I bought the truck. They were bound to leak but now they leak. It is only the passenger side, the drivers side manifold does not leak but I'm sure it will follow soon enough. The bolts are badly rusted and one is pushed right through the entire mount and is secured with a nut on the other side. Will most likely need a torch to break them loose. Will the leaks do any damage to engine parts? The spark plugs got hit pretty bad by the leaks till I put a longer boot cover plug set on them. Any good gaskets to buy?

[HIO Silver]

Look into Remflex gaskets.

Prolonged exhaust leaks can erode the mating surface where it leaks. 'Had one on my 70 that the PO never fixed and the metal was gne from where it was leaking.

[BobbyFord]

If you ever have the heads off of the motor, have the exhaust side of the head milled, the exhaust manifolds milled flat and assemble with no gasket. If you use grade 8 bolts and grade 5 washers, it'll last forever.

[Subzero]

Thanks for the help, the leaks started about a month ago and will be fixed by June. Would that fall under prolonged leaks? I plan to have the engine rebuilt in comming years but for now I'm going to try and make it last as long as possible. If they are milled flat, should sealer be used or nothing? Should sealant be used on the gaskets too?

[BobbyFord]

Once everything is milled, you assemble metal to metal, no sealant or gaskets. I did the 390 in my 63 about 10 years ago, still has no leaks.

[hotrodfeguy]

I have found most of the time the Exhaust manifold side burns first. But Bob is right it can happen. But with the liquid cooling in the head side it takes longer. Als long as your at it when your pulling the exhaust side manifold off have that milled down I bet that was the issue. Or this is a good time to upgrade to Headers.

http://www.summitracing.com/parts/big-1 ... odel/f-100

[Subzero]

I wish I could buy headers and something to replace the rusted out duals on the truck but I'm tight on money right now so manifolds will have to do. I plan to have the exhaust replaced this year but it will be something low cost.

[HIO Silver]

There's a guy over in FTE with FE headers up for sale: http://www.ford-trucks.com/forums/12897 ... st13931831

[Red Mercury]

Bobbyford is right, no gaskets is the way to go if the surfaces are flat & smooth. I have a 79 F150 with the original 400 engine. It never had gaskets from the factory and I have had the manifolds off twice. 400,000 miles & never had a leak. Most people think that every exhaust manifold needs gaskets, but that is not true. Sometimes I wonder if gaskets can do more harm than good--leaks, rust, corrosion, warped manifolds. Not sure, just sharing my experience on the topic.

[Whateverman]

The FE exhaust manifolds seem to warp worse than any others ive ever come across.
U could try some no leak/no retorque header gaskets (cant remember the brand i used), i never tried them on my truck with the 360 underhood but they havent leaked even a little on 2 different motors
(they outlasted the 1st motor)
On the 360 i was goin thru gaskets every 2-3 months until I started using header gaskets slatthered with a ton of high heat anti-seize...that lasted 4-5 months..high heat rtv helped on headers but not on exhaust manifolds

[Ranchero50]

Ditto, no gaskets. Maybe a slathering of Permatex ultra RTV and pick up a box of NordLocks for the bolts.

Heat cycling and felt gaskets just doesn't work.

[gleno]

This thread is a little grey in the tooth, as they say, but if anyone in the Brain Trust has any quick thoughts...I would be very appreciative. A couple of years ago I put a fresh head in my 71 300 I6. I did nothing to resurface the manifolds at that time when I put it back together because I wasn't smart enough. I reassembled the engine with a gasket on the manifolds, and all was well for a time, until leaks began to develop in the forward exhaust/head ports. I now have the manifolds off and at the machine shop. On the engine, as well as my observation of the failed gasket, the story is clear: the exhaust manifold is bowed, with the carburetor area being the high point of the manifold bow.

I have block-sanded the head on the mating surface area with 220/400 grit, and it cleaned up pretty well. No rust or scaling left, so I have a pretty good plane to start over here. Supposedly, in a day or so, I will have my machined head back in hand, and I am at a point of a decision here.

Would a wise person separate the intake/exhaust manifold assembly and fasten them individually, without a gasket? Would a wise person keep the manifolds assembled and use a gasket? With a sealant, or dry? I have a Felco combination intake/exhaust gasket to work with here, but if there is a better product or approach, I'm an eager student.

It is easy to look at the long inline manifolds, and then appreciate the stresses of heat over the long and narrow span. The assembly calls for loading the center bolts first, which should flatten the manifolds most effectively. In this case, does it make sense to torque above specs on those center bolts to help keep the center region of the manifolds flat against the head? Or just set the center bolts up to full torque before torquing the outer bolts?

Should there be a sealer of any kind in this reassembly? Intake ports only?

Thanks to any and all for your input and experience here. Gleno

[Ohiotinkerer]

Remflex 3005 gasket is what you need - $40 on Amazon - after using them on the 360 in my bump I'm sold on them and will be using one on my 300 I6 build. I had my manifolds machined and cleaned up the heads and developed a leak again after 1 year of using FelPro gaskets and switched to Remflex and hadn't had any issues since. Use that and torque everything per factory specs and instructions and it should solve your problems........

[farmallmta]

If you ever have the heads off of the motor, have the exhaust side of the head milled, the exhaust manifolds milled flat and assemble with no gasket. If you use grade 8 bolts and grade 5 washers, it'll last forever.

Best answer to any question and posted on the internet anywhere on this date! This gentleman knows his FE exhaust leaks!

The shop manual calls for assembling with a coat of white graphite grease on the mating surfaces. This is a cook-in material that fills the iron pores and the baked carbon is all the extra seal needed IF the surfaces are flat-milled/planed properly. Chevy manifolds can be surfaced, FE manifolds must be planed. Yes, there's a difference and Bowtie freaks just can't grasp it , nor will they plane your Ford manifolds properly because... you know, CHEBBY!!!! *drool*