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Discussion Starter · #1 ·
This is my first post here so bare with me, I have a 78' Bronco with 400 and it actually runs really good but it was using a lot of oil when I bought it. Because it was a hunt/fish I put oil in it and let it ride. I found myself driving this thing daily when the engine on my work ride let go. So, it smokes on start up and I find myself constantly adding when needed. I have to change or clean spark plug on #5 cylinder about every 2 to 3 weeks because it is fouled and had to replace a bent pushrod in the same position about 2 months ago. Other than that it runs great and seems to have plenty of power. How hard is it to replace the valve seals on this thing seeing I am fairly sure where my problem is, or am I looking at a very costly rebuild? All assistance greatly appreciated. By the way - nice site!
 

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They aren't bad to replace.
It can be done without pulling the head.
Just need to pressurize the cylander with intake and ex. closed to keep the valves from dropping. Pull the rocker and slip a new seal on.
Most compression tester kits have the attachment you need. Basicaly just need to thead it into the sparkplug hole and attach constant air to it.
Then just a matter of pulling the rocker out of the way.
 

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Then just a matter of pulling the rocker out of the way.
your missing the part about needing a spring compressor to compress the valve spring. When you do this be sure you do not drop the keepers any place that would be bad.
 

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your missing the part about needing a spring compressor to compress the valve spring. .

No I'm not, that's what the 2 links were for, to cover all the boring details. :toothless

You can release the keepers with a socket and hammer, even re-seat them that way too, but it's tricky. When I did the seals on a '70 Montego it was before autopart stores loaned tools, so I didn't have a spring compressor, kid helping me was slamming screwdrivers(drink not tools) and was passed out befor he finished the first head, left me to finish it so I could get to work the next morning. Ahhh, the good old days.
 

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when my valve guide seals went bad i went to advance auto and picked up a rebuilt set for 300$, and it was pretty easy, just always inspect rebuilt stuff carefully, on one of the heads i got on the cast boss part where the rockers bolt to had one of the little ears snapped off, and on the second one, one snapped off too but they attempted to weld and helicoil it so i told them to get me a new set and they worked great. my 2cents

-jay
 

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If his guides are good then no need to replace the head.
Depending on the miles on the motor, replacing the heads with fresh can easily lead to blowing the rings on the bottom end due to improved compression.

I haven't done a set of seals in a while, but the seals weren't more than 20-30 bucks the last time. Then it's just your time doing it, pretty cheap if your guides aren't worn too bad.

Don't forget to clean out all the crap left from the old seals.
 

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Discussion Starter · #8 ·
Well, that sounds simple enough so I know what I will be doing this weekend. I appreciate the great feedback!
 
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