Exhaust Headers for '65-'70 Mustangs...

geoklass

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Sep 3, 2018
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1965 Mustangs are 55 years old. In their wildest dreams, I doubt that FoMoCo thought that they would see early Mustangs still on the road in 2020. I think that there are no parts or components that you cannot purchase for a 1965-1970 Mustang these days. The problem is that many of the parts are no longer offered at your local Ford dealers. The vast majority of parts are offered only from the aftermarket industry, with many of those parts being built off-shore. Motor mounts are at the top of the list. There are some nice looking motor mounts out there, particularly the ones that use a non-rubber insulator such as Pro-Thane or Energy Suspension. There are also the "replacement style" motor mounts, the kind that you can get at the local Auto Parts stores (like NAPA, Auto Zone, O'Reily's, etc.). These look like the original style mounts, but many of them are not even close. (I purchased a set of 1966 engine mounts from a Ford dealer last year, and it said "made in South Korea on it") They will bolt on to the chassis, and also bolt on to the engine, but they frequently lower the engine in the engine bay. With the naked eye, it's not easy to distinguish any difference. This holds true with some of the Energy Suspension mounts, too. I have seen some that lower the engine as much as 3/4", and again, it's tough to tell if you open the hood and look at the engine. For 98% of the things or components that you may bolt on to your engine, it really makes no difference if it sits a little lower in the chassis, and in fact, it can give you some additional room for a larger air cleaner without hitting the hood. This is particularly true if you have swapped in a 351W block to replace your old 289 or 302 engine.

But for Long Tube Headers, 1 3/4" primaries and above, beware. The headers bolt to the engine, and if the engine sits a little lower (sometimes by as little as 1/2"), the headers may come into contact with the chassis sub-frames, the steering system, or the suspension system. As the engine drops down, so do the headers, while the rest of the vehicle does not change. Every header manufacturing company that I know of builds their headers to fit on an engine in the stock, OEM location. "Stock" means that the engine is not sitting lower, or higher, or further back in the chassis. It also means that the engine is sitting in the stock location side to side. Many folks do not realize that the engine is NOT located at the centerline of the car, it's usually a little closer to the passenger side than the drivers side. When you are sitting in your Mustang, look at your feet. The driver's side floorboard needs room for three pedals. There are no pedals on the passenger side. Shifting the engine toward the passenger side a little also gives more room for the shift linkage on the transmissions in the trans tunnel. Several of these Mustang II suspension / steering rack kits for the early cars center-up the engine.

Anyone that has ever had to install (or tried to install) long tube headers on an early Mustang knows that there is very little extra room in there, between the engine and the chassis. If the engine is not EXACTLY where it needs to be (which is the stock OEM location), interference between the headers and the chassis is entirely possible. And again, it's very difficult to tell if the engine IS in the stock location. Sometimes your first clue is that the long tube headers you are trying to install hit something on the chassis or steering system. It's usually not a problem with the headers, it's either that they engine is not in the OEM location, or there are aftermarket suspension, chassis or steering components in the way, AND the engine is not in the OEM location. RCI Headers makes no bones about these issues, we go out of our way to warn potential customers in advance on our website. If the engine is sitting a little too low, we can usually fix that situation over the phone, but the reality is that the early Mustangs are between 50 and 55 years old. I suspect that the enthusiasts that have them now were not the original owners. I suspect that the majority of you that own the car now have no idea how many owned it before you. You may THINK that the car is totally original, but only a few really are. In short, and I kind of hate to say this, if you are unsure about your early Mustang, if you are not handy with tools and don't know how to modify things as needed, or have someone you can go to if you need to, this is probably the time to consider Shorty Headers (just saying the word makes me cringe)...
 
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dennis112

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May 15, 2005
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As usual, you are spot on George. The original 1 3/4" headers you had built for me and my 351W in a 65' almost 20 years ago fit "OK"--once I finally got them in place. They were a little self clearancing on the shock towers but that was minor and I was happy that they were in place. I've since moved on to using 68' Mustang shock towers/suspension in the same car and purchased a set of 1 7/8" headers. You repeated warned me that there would be problems in using them with a Z-bar and taller port 7721 heads (twice you wanted to cancel my order) but I instisted and made them work by me moving a couple of tubes (which is not something that the average enthusiast would ever want to entertain.) I appreciate your honesty on the matter. You could see my enthusiasm and sold them to me (after a lot of convincing on my part.)

Your a good judge of character.

Thank You!
 
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Ray65-71-73

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Dec 11, 2001
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When I put the first 351W in my 65 convertible I could not find commercial headers. So I made a set of equal length, 34 inch, 1.5 diameter primaries - 1.5 completely covered the D shape port. On the first rebuild I rounded the port to match the header.

Since I built them, they fit. But to install them I removed the heads.

I recently installed the third 351W - 427. I got a pair of shorty, stainless. I installed them with the engine raised about a foot, after the engine had been installed, and running, with other manifolds.

After having the engine in and out a few times, raising it to install headers is not a big deal.
 
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geoklass

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Sep 3, 2018
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Monrovia, California
For whatever reason, a lot of people try to install long tube headers in Mustangs with everything bolted down and in place. The engine MUST be raised a few inches, and the steering shaft MUST be removed (or moved out of the way). If people are incapable of doing things like that, they should stick with Shorty or Mid Length headers. I have said this over and over, including here on StangNet, 95% of street/strip cars do NOT need Long Tube Headers. We have converted a lot of all-out race cars over to our Mid Length Headers (1 3/4", 1 7/8" and 2" primaries), which are MUCH easier to install, lighter in weight, and less costly to purchase. Unfortunately, due to the design on the early Mustangs and super cramped quarters, we can't produce the Mid Length headers for the '65-'70 Mustangs...
 
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Ray65-71-73

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Dec 11, 2001
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we can't produce the Mid Length headers for the '65-'70 Mustangs...

And I assume you are working with a 289. Would you consider 34 inch at least mid length? I put 34 inch on a 351W, 1965 stock chassis, no messing with the steering. Ran them with two 351Ws for several decades.

I did them with 1.5 inch primaries because that is as big as the head ports. I could have gone larger. And no issues replacing the starter.

There are pics here:
 

geoklass

Active Member
Sep 3, 2018
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Monrovia, California
And I assume you are working with a 289. Would you consider 34 inch at least mid length? I put 34 inch on a 351W, 1965 stock chassis, no messing with the steering. Ran them with two 351Ws for several decades.

I did them with 1.5 inch primaries because that is as big as the head ports. I could have gone larger. And no issues replacing the starter.

There are pics here:

On the 1965-1966, Long Tube headers are much more of a problem on the 302 engine than on the 351W engine. The extra deck height of the 351W block gives us more room to clear the steering box. But, we can use 1 3/4" primaries on both the 289/302 and the 351W. The primaries on our Long Tubes are between 32" and 34". We are under the opinion that 1 1/2" primaries are a little small for 351W's with 400+ inches. but 1 5/8" is fine. In some cases, 1 3/4" can be considered overkill.