[Rapaiz]

I've been working on my car for about a year and trying to wrap up some things. Purchased the car from a second owner who did some work. Either the original or the last owner did some screwing an wrong things. 66 Mustang V6 converted to a 289 or 302 (I can't tell which yet as I haven't opened the engine.

Anyways, trying to put the pipes back on using new flange bolts. They wouldn't work and turns out they are bigger than the bolts I took off. Turns out they had used 3/8 instead of 7/16 bolts. I'm not surprised. I verified the casting number D1OE-9430-CB (passenger side) that they are Ford manifolds and should be 7/16 so I removed them and I was able to clean up the holes and get the studs into them.

When removing one side, it was missing the 2 middle longer bolts on one side. Because of this and also because I didn't want to reuse the fasteners, I started looking for a bolt kit. But this is where I am confused.

All of the bolt kits I see have short and long bolts (a pair per port), but my castings have 3 different hole lengths. All of the short bolts are the same, but the two outer long bolt holes are 0.25" shorter than the 2 middle long bolt holes as measured on the casting. The driver side, which had all 8 bolts, have 3 different lengths, but they are clearly not OEM.

Here are some photos of the manifolds pointing out the different casting heights for the holes.

I checked the hole depth in the head and they are all the same depth. So the question is, should I have 3 different bolt lengths, or will the long bolts in the bolt kits work for these headers. Any idea how much thread engagement there should be?

Also, anyone use the Manifold bolt locks? Do they work and are they worth they extra money? I'm not sure if the missing bolts came out on there own or if prior owners just screwed it up.

Any help is appreciated.

 

[awhtx]

Your first problem is that you have the wrong exhaust manifolds for a '66. Your D1 manifolds came off of a 1971 or later car. The flanges where the exhaust pipes connect may be in the wrong location for a '66 Mustang. Here is a photo of the correct manifold. Notice that there are only two different length bolts used to attach it to the engine.

 

[zray]

If you are using stock iron exhaust manifolds and the stock iron cylinder heads, I strongly suggest not using any exhaust manifold gaskets.

any machine shop can check and resurface the manifolds if they not already completely flat. The cost is minimal.

most of these cars with iron heads and manifolds left the Ford factory without any exhaust manifold gasket. After a few minutes of running the microscopic carbon bits in the exhaust will seal up any gaps in the manifold surfaces. And you never have to worry about replacing a blown out exhaust gasket again.

I’ve been building Fords without the manifold gaskets for over 50 years. No leaks so far.

Z

PS: another plus is your bolts won’t need checking & retightening. I check them once after run in just be sure, but they are always spot on.

 

[Rapaiz]

Your first problem is that you have the wrong exhaust manifolds for a '66. Your D1 manifolds came off of a 1971 or later car. The flanges where the exhaust pipes connect may be in the wrong location for a '66 Mustang. Here is a photo of the correct manifold. Notice that there are only two different length bolts used to attach it to the engine. View attachment 886741

Thank for confirming the year. As I mentioned it is a converted 6 cylinder. Any way to check the engine date?

It has pipes and it all seems to fit and line up well on the underside. But good to know in case I replace in the future.

So assuming I keep them, would I just get a bolt set for 71 and later? I think some of those came with bolts and some studs and nuts. I guess that would fix the issue too.

If I buy the proper manifolds, I assume the will bolt up, but I may need to adjust pipes.

 

[Rapaiz]

If you are using stock iron exhaust manifolds and the stock iron cylinder heads, I strongly suggest not using any exhaust manifold gaskets.

any machine shop can check and resurface the manifolds if they not already completely flat. The cost is minimal.

most of these cars with iron heads and manifolds left the Ford factory without any exhaust manifold gasket. After a few minutes of running the microscopic carbon bits in the exhaust will seal up any gaps in the manifold surfaces. And you never have to worry about replacing a blown out exhaust gasket again.

I’ve been building Fords without the manifold gaskets for over 50 years. No leaks so far.

Z

PS: another plus is your bolts won’t need checking & retightening. I check them once after run in just be sure, but they are always spot on.

Thanks for the info. That sounds interesting. The heads are on so not sure how to check them for flatness without pulling them.

 

[awhtx]

"Any way to check the engine date?"

You can go under the car and look at the engine block near the starter. You will find a number in the same format as the number on your manifolds except the 4 numbers in the middle will be 6015. Near that number you will find a 3 or 4 character number that be a code for the day the block was cast. It will consist of a numeral, a letter, and then 1 or 2 numerals. If you find those numbers post them here.

 

[zray]

Thanks for the info. That sounds interesting. The heads are on so not sure how to check them for flatness without pulling them.

Heads rarely warp. But you can check with a straight edge with the heads in place. The manifolds are more likely to warp a little. Making them perfectly flat is a simple job for a machine shop. Less than a 1/2 hour for both manifolds.

Z

 

[Mcmahst]

I wonder if the PO put a 71 or later engine in the vehicle as part of the conversion? Before you buy parts, make sure you know what you have.

 

[Rapaiz]

I wonder if the PO put a 71 or later engine in the vehicle as part of the conversion? Before you buy parts, make sure you know what you have.

I'm sure that is what they did. I just wasn't sure on the year for the engine and didn't realize the manifolds would be slightly different. I guess I can't even say 8fy manifolds were ever in a mustang. Could be a bronco or something else.

Not sure of the year on the tranny either. Know it is a C4.

 

[Rapaiz]

"Any way to check the engine date?"

You can go under the car and look at the engine block near the starter. You will find a number in the same format as the number on your manifolds except the 4 numbers in the middle will be 6015. Near that number you will find a 3 or 4 character number that be a code for the day the block was cast. It will consist of a numeral, a letter, and then 1 or 2 numerals. If you find those numbers post them here.

Here is what I found.

 

[MidnightExpress]

Here is what I found.

View attachment 886821

Looks like a February 9th 1970 cast date with a 1969 casting number. It is a 302ci

 

[awhtx]

You apparently have a Frankenstein engine. D1 exhaust manifolds would not be correct for an engine in a 1970 year model car. Can you pull the valve covers and look for the casting dates on the heads? They will be found amongst the valve springs.

 

[MidnightExpress]

You apparently have a Frankenstein engine. D1 exhaust manifolds would not be correct for an engine in a 1970 year model car. Can you pull the valve covers and look for the casting dates on the heads? They will be found amongst the valve springs.

A D1 casting number could be correct for a 1970 as D1 is 1971, and a D1 engineering number could be a design change for the 1971 production year correct? So essentially the engine could have been out of a 1971 year vehicle, but assembled and sold in 1970 much like a '64 1/2 Mustang is titled as a 1965? With both C4 and C5 castings numbers as design changes were implemented. Or am I not thinking correctly?

Much like my titled '92 F150 is a 9th Gen aeronose, but it's assemble date is December '91 which by year, would mean it should have a 8th gen bricknose, but since it was ordered and built in 1991 for 1992 production year, a new design change, it has the 9th gen aeronose.

 

[awhtx]

I am not aware of any 1971 Fords that were built in February, 1970.

 

[MidnightExpress]

I am not aware of any 1971 Fords that were built in February, 1970.

D1 is not a date code but a working engineering design for 1971

 

[awhtx]

D1 is not a date code but a working engineering design for 1971

And as far as I know there were no 1971 year model Fords built in February, 1970.
Maybe the OP will tell us if his D1 manifolds have 0B? casting dates.

 

[Rapaiz]

And as far as I know there were no 1971 year model Fords built in February, 1970.
Maybe the OP will tell us if his D1 manifolds have 0B? casting dates.

I can pull a valve cover and get numbers for the heads.

We're do I look for the manifold casting dates?

 

[awhtx]

Here is the original left side manifold from my Sept 1964 built Mustang. The engineering code is C3OE-9431-A and the date code is 4H27 or Aug 27 1964. The intertwined CF represents the Cleveland Foundry.

 

[awhtx]

And here's the right side. C4OE-9430-A and 4J9.

 

[MidnightExpress]

And here's the right side. C4OE-9430-A and 4J9.

Those are 1964/1965 exhaust manifolds. September 9th 1964

Edit: You knew that already. 🤥 I got mixed posters mixed up.