I finally got my 85 f150 300 started after putting I a new engine and rebuilt the c6. I am now having to replace the manifold gasket due to it leaking. I had to buy 3 gasket all ready just to get it on the first time. Any tips or tricks and swapping out the gaskets to were I dont have to do it again? Any help would be grate.

 

I have never worked on a six. What seems to be the problem? Gaskets go in ok and then start leaking later? You are talking about the exhaust manifold correct? You may have to take the manifold completely off and use a straight edge to make sure it's not warped where it goes against the engine.

 

As Dave said it might be best to pull the manifolds and check if both are level.

Did you have the exh. & the intake manifolds apart? If so did you bolt them together before bolting them to the head?
If so may want to loosen the 2 so they can move, bolt the manifolds to the head but not tight just snug.
Then tighten the 2 manifolds together then them to the head.

Oh and you have been starting in the center bolts and working your way up & down and to the ends.
Center top & bottom, right top & bottom, left of center top & bottom, etc.
Also do not do them all in 1 shot make 3 passes till tight.

The only other thing I had an issue with was I did not have the manifolds up high enough and caused a vacuum leak.
I was lucky and was able to loosen them and raise them into place and tighten back up as the gasket had only been on for about 5 min. of running when I found the leak on mine.
I am also running EFI exh. manifolds so I was dealing with 3 different manifolds at the same time.
Hope that helps
Dave ----

 

I only ran the engine for a couple of seconds and found the exhaust leaking from the center so I am wondering if it is the gaskets between the two. Is there a way to change just that gasket with out taking the both the off? Is running efi exhaust manifolds any harder to do or any performance benefits?

 

If it has only been a few seconds then I might try and reuse it but it brings up a question(s).

Why is this the 3rd gasket and did the others leak in the same place, center and exhaust?
If yes on the leaking same place then I would pull the manifolds off and make sure they are not warped. Might even want to take to a machine shop and have them run it thru to make sure they are true.
Or if you have a belt sander you can try running it across the face of the manifolds just be careful as the not to take too much off the ends as that can easily happen.

All the gaskets I have gotten the intake & exhaust are stapled together, paper intake to the metal exh. gasket. They say you can remove the staples and not use the exh. gasket but I have never done that.
Now you could get another gasket set and remove the staples and use 2 exh. gaskets and 1 intake BUT that may make the gasket to thick and the intake side may not seal and / or could crack the manifolds so I would not do this.
So if you have stapled gaskets then no you can not remove just that gasket and to give room to even slide the gasket out & in you would need to loosen the other manifold and this would happen anyway because the bolts / washers that hold the exh. also hold the intake manifold.

As for the EFI manifolds: It does have it's own issues. You need 3 or 4 hands to install as now you are dealing with 3 manifolds NOT bolted together.
There is no heating of the bottom of the intake manifold because they are not bolted together. This is only an issue if you drive when it is cold / cool & damp as it can lead to icing of the carb & manifold BUT there is a work around. At 1 time you could buy a plate that bolts to the bottom of the intake that you run heater hoses to and that would heat the intake manifold.
If you cant find this plate on line it is not hard to make using the gasket as a pattern to cut from a steel or Alum. plate and drill & tap for hose barbs.

It is said to use studs, nuts and the old thick washers. You can hang the gaskets on the studs, then with you 3 or 4 hands fit the manifolds up to the head, thick washer and nut to hold everything in place.
I have done this 3 times and it is only hard the first time as you don't know just how it all fits together. Some may even bolt the Y pipe to the manifolds to make them as 1 so now you are dealing with 2 manifolds and not 3.
That brings us to the Y pipe, you can only buy it with the cat and that is how it is listed when looking of it. It has been posted where the 2 pipes join the hole in the 1 pipe is really small and needs to be opened up, mine was ok and I did not use the cat ( not running any).
They say the EFI exh. manifolds flow better to give the motor a little boost in power but I can not tell you how much as I have not driven my truck with either set of manifolds, I have not driven my truck at all and I have had it since Dec 2015.

The reason I went with the EFI manifolds was the motor in my truck was changed an the factory front head pipe would not fit the manifold on the motor. I had a radiator a member needed and he the manifolds so we did a swap. I had to buy the Y pipe and the studs & nuts.
The Y pipe fit up to the newish exh. system I pulled from a parts truck with a short pipe and 2 clamps so I used all factory parts for the exh. system.
If it was not for that head pipe & manifold miss match I would not have gone with the EFI manifolds.
Manifolds & Y pipe

Hot water plate


Studs in head & gasket hanging on them

All bolted to the head

You can get the manifolds & Y pipe from the junk yard or buy new on line.
Dave ----

 

Sorry I have had this truck apart so long I forgot the exhaust manifold was taken to the machine shop and checked for straightness. The reason for the first gasket failure was because I tore it when trying to get it in stalled. Yesterday was the first time this engine had ever ran.

 

When I when and took the manifolds off I found the gasket between the two causing the problem. I tried to lossen all the manifolds bolt and tighten the three that hold the two together with result. Pulled everything apart and found studs to put in and replaced the gaskets one last time before buying a new exhaust manifold. After putting studs in it getting all back together it fixed it. Thank you for all y'alls help.

 

Good to hear you got it fixed.
If you took just the exh manifold to the shop and checked out good then bolted it tight to the intake that could have been the issue.
That is why I said to only bolt the 2 manifolds together loosely / snug then bolt them to the head again loosely / snug then do the 3 bolts on the bottom then to the head.
I also think the studs make it easier to mount everything and they are fine threads that help get a better "grip" to tighten it all down.

My first time when I did the EFI manifolds I had no leaks. Later on I found the a freeze plug on that side of the block leaking so I pulled the manifolds off to change out all the freeze plugs.
It was when I put it back together in a rush that I had a vacuum leak because the manifolds were to low. Only running a short time I undid the nuts and raised it up and tighten and was good ..... so far LOL.
Dave ----