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Discussion Starter #1
Bought new Flo Tek aluminum heads for the 5.0 in our 65 convert. Drivers side hipo exhaust manifold bolted up with ease but I can't get the passenger side to line up after repeated attempts.

I can get the short & long bolts started at one (either the front most or 2nd from front) exhaust port but then it seems like the remaining holes in the manifold do not line up just right with the holes in the head. Looks like the manifold needs to move toward the back of the engine a tiny bit in order for the holes to line up. I had these manifolds on a set of GT40 heads so I've used them for years.

Whats making this hard is the rear of the exhaust manifold is engaging the H pipe opening so when I'm trying to position the manifold I'm having to lift the whole H pipe/exhaust system with it.

Thinking of unbolting the passenger side exhaust from its hangers to see if pulling it toward the rear will allow the room to position & install the manifold ? Never had to do that before but I'm at a loss of what else may remedy this so any suggestions are much appreciated...had to walk away yesterday, thoughts of picking up a baseball bat instead of the wrench were becoming very tempting.

Thanks in advance.
 

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If you measure the flange hole diameters on the manifolds, I think you will find they are very close to the bolt diameter. You need to open the holes roughly 1/32” over what you measure them to be. This will permit misalignment/manufacturing tolerances between the heads and the manifolds.

I would suggest gasket matching the manifolds, but don’t install the gaskets as they are not needed.
 

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Just a couple things as I just installed Hi-Po manifolds as well on my '68 302. They fit perfectly on my Edlebrock 5023 E-street heads with no mods needed to bolt holes. Some said you may have to die grind some to clear spark plugs, but my spark plugs fit with no modifications. I also advise to port match to the proper gasket as the manifold ports are quite small. It really does not take that much time and it grinds like butter. I was advised that if you go iron to iron head to manifold you need no gasket but iron to aluminum you need a gasket. I am installing a Fel-Pro SFL1415 gaskets with mine, but maybe not needed.
 

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please give an opinion on the heads after you've had some time with them. I know one guy who used them and they made a pretty nice difference on his car. i'm tempted to buy a set for myself.
 

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Discussion Starter #6
please give an opinion on the heads after you've had some time with them. I know one guy who used them and they made a pretty nice difference on his car. i'm tempted to buy a set for myself.
I sure will. I'm eager to get it running with the limited driving season here in MI. Just have to install the carb & PS pump after getting this manifold figured out...of course I did not take pics of how the PS brackets were set up - thought I'd remember- ya right. Its a pump from a 69 so it was a bit of a custom install which I didn't do. That may be a question for another post in the near future.

I appreciate the replies- gonna enlarge the manifolds bolt holes tomorrow. I like that plan better than unbolting the exhaust hangers to try to move the H pipe out of the way.
 

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I sure will. I'm eager to get it running with the limited driving season here in MI. Just have to install the carb & PS pump after getting this manifold figured out...of course I did not take pics of how the PS brackets were set up - thought I'd remember- ya right. Its a pump from a 69 so it was a bit of a custom install which I didn't do. That may be a question for another post in the near future.

I appreciate the replies- gonna enlarge the manifolds bolt holes tomorrow. I like that plan better than unbolting the exhaust hangers to try to move the H pipe out of the way.
If it were me, I would loosen the exhaust to move it back the tiny bit you need before I enlarged the holes. Just my opinion.
 

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I sure will. I'm eager to get it running with the limited driving season here in MI. Just have to install the carb & PS pump after getting this manifold figured out...of course I did not take pics of how the PS brackets were set up - thought I'd remember- ya right. Its a pump from a 69 so it was a bit of a custom install which I didn't do. That may be a question for another post in the near future.

I appreciate the replies- gonna enlarge the manifolds bolt holes tomorrow. I like that plan better than unbolting the exhaust hangers to try to move the H pipe out of the way.
thanks. my buddy did them on a late 5.0 for a build in MM&FF on an '85 capri http://www.mustangandfords.com/project-vehicles/mmfp-1006-1985-50l-mercury-capri-flo-tek-cylinder-head-and-cam-upgrade-part-4 . he had good luck with them, but more opinions are always good :)
 

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My mind isn't what it used to be, but I remember, at some point in time, hearing about header & manifold installation difficulties with some aftermarket aluminum heads due to part of the casting being in the way and needing to be ground away.
 

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Discussion Starter #10
Got it installed finally. Removed the bolts on the exhaust pipe hangers but that didn't help. On looking at the manifold closer I found some of the bolt holes had been drilled larger that others. Had to open a few of them up more to allow it to move far enough back on the head to line up all the holes.

Thanks again for your replies.
 

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Still have to install carb & PS pump. I had GT40 (non-P) heads on the previous 5.0

I'll post how much difference there is soon as I get her on the road.


Thanks again.
 

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Discussion Starter #15
update

Sorry for the delay in getting back about the Flo-Tek heads I bought. Review is 2 thumbs up. The 5.0 that was in the car was very tired so that may make this new setup seem better to me than others with what I'm comparing it to but the car definitely performs much better. Not sure i'm crazy about the b303 cam though- as some have said its not real street friendly- car doesn't like to go slow. For example when I shift into 3rd at about 30mph it doesn't like cruising at 35mph, if i don't continue accelerating it starts to have an intermittent lurch. i'm finding myself getting it up to 40 mph then shifting into neutral and coasting a bit to avoid the lurch when i'm in an area with 35mph or lower speed limits. The 3.00 rear gear is part of the problem but with as much freeway driving as I do I don't plan to change it.
 

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I had that "lurch" after I installed my custom cam, which is quite a bit more than the stock 5.0 but different than the B303.
I was able to tune most of it out with the carb. In my case (Summit carb) I opened up the secondary idle slots a bit more than stock and almost closed complete the primary idle slots. Fattened up the idle mixture a bit and 2 more degrees of initial timing and it won't lurch at 1600 rpms.
 
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