Head replacement woes
Thread Starter
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Junior User
Joined: Feb 2007
Posts: 85
Likes: 1
From: Eastern Washington
Head replacement woes
'95 F150, 351, auto tranny, 125k miles.
This weekend I replaced the heads on my truck with remanufactured ones I got from the local auto shop. I also replaced the lifters, pushrods, rockers (with crane 1.7 roller rockers) and replaced the exhaust manifolds with shorty headers and gave it a new exhaust system, 3" cat back.
My problem is the new heads. I have a pipe that bolted to the back of my old heads and ran into a series of tubes that fed down to the exhaust, between the stock cats. One of my new heads supports this tube, the other does not. What does this system do? Will it hurt anything if I blank off the flange of the pipe that does not connect to the head anymore(the bolt holes do not even line up anymore...) or should I let it draw air from the engine compartment.
I know the right answer is to probably pull that head and send them back for one that is just like the original, but it is already installed and if I can work around it, I just want to leave it in. Other than not mating up to that pipe in the maze of emissions tubing in the back, it is just like the original.
p.s. Is there some trick to putting the tensioner pulley back onto the bracket? I can't seem to make it line back up correctly.
-Steve
This weekend I replaced the heads on my truck with remanufactured ones I got from the local auto shop. I also replaced the lifters, pushrods, rockers (with crane 1.7 roller rockers) and replaced the exhaust manifolds with shorty headers and gave it a new exhaust system, 3" cat back.
My problem is the new heads. I have a pipe that bolted to the back of my old heads and ran into a series of tubes that fed down to the exhaust, between the stock cats. One of my new heads supports this tube, the other does not. What does this system do? Will it hurt anything if I blank off the flange of the pipe that does not connect to the head anymore(the bolt holes do not even line up anymore...) or should I let it draw air from the engine compartment.
I know the right answer is to probably pull that head and send them back for one that is just like the original, but it is already installed and if I can work around it, I just want to leave it in. Other than not mating up to that pipe in the maze of emissions tubing in the back, it is just like the original.
p.s. Is there some trick to putting the tensioner pulley back onto the bracket? I can't seem to make it line back up correctly.
-Steve
New User
Joined: Oct 2005
Posts: 15
Likes: 0
From: Alabama
Those pipes are for the smog. I recently did a complete motor swap. I did a full GT40 conversion. The GT40P heads that I used did not have the ports on the back. I also ran new true dual exhaust. Therefore, I cut all of the smog off of my truck.
You could just plug it all off, or, I would double check to see if you did not get to different styles of heads. It might be possible that you got one head with larger valves. You never know. Personally, I would much rather have a matching set. If performance is the issue, I would rather have the set without the smog ports. It is that much less to worry about.
You could just plug it all off, or, I would double check to see if you did not get to different styles of heads. It might be possible that you got one head with larger valves. You never know. Personally, I would much rather have a matching set. If performance is the issue, I would rather have the set without the smog ports. It is that much less to worry about.
Former ******
Joined: Nov 2004
Posts: 4,901
Likes: 2
From: Salt Lake City, Utah
I would not mess with the emission equipment. Doing so is illegal and in addition, you have nothing to gain. Most vehicles loose some bottom end by removing the converters. True duals also result in additional power loss versus a properly set up single exhaust or crossover duals. I view emissions as a challenge. I like having a vehicle that can outrun most as meet all emission requirements. It also improves the resale value if the vehicle still has all its original equipment. Leave the emission equipment along unless it is broken or damaged, and if it is does fail, you have bigger problems than ruined converters.
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Junior User
Joined: Feb 2007
Posts: 85
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From: Eastern Washington
I'm not looking to remove the cats. In fact, I just put in a new one with a new Y-pipe, and ran a complete new exhaust system from headers back. The heads I have are different - valves are the same size, springs are the same, only one has exhaust ports like my old ones, and one does not have any.
There was also a port in the front of the head, which used to be plugged up by the alternator bracket bolt. This port was bigger than the original, so I had to run a bolt in and cut the head off of it - and it got rid of my exhaust leak!
So, the smog stuff just pumps air into the exhaust to let the cat process un-burnt exhaust better, right? Would it hurt if I just plugged the rear port as well, and then plugged the tube going into the cat? My friend has a '96 F150, and his truck doesn't have any of the smog stuff on it...
There was also a port in the front of the head, which used to be plugged up by the alternator bracket bolt. This port was bigger than the original, so I had to run a bolt in and cut the head off of it - and it got rid of my exhaust leak!
So, the smog stuff just pumps air into the exhaust to let the cat process un-burnt exhaust better, right? Would it hurt if I just plugged the rear port as well, and then plugged the tube going into the cat? My friend has a '96 F150, and his truck doesn't have any of the smog stuff on it...
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
This port was bigger than the original, so I had to run a bolt in and cut the head off of it - and it got rid of my exhaust leak!
