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Discussion Starter · #1 ·
I just bought a 66 convertible and i have a few questions about what type of oil to put in it and where i can find the numbers tagged on the engine to find out if its a true I-6 from 66.

Thanks,
Kyle.
 

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Hi Kyle,
Can't answer the last question but for the oil you need to make sure the oil has the proper level of zinc in it(.I believe it's 1200 ppm or more.) It has been removed from most oils in recent years(by the EPA because of catalytic converter damage) but is needed for older flat tappet engines such as is in you Mustang. I use Amsoil synthetic 10W-40. And I would definately recommend a synthetic for engines that have been overhauled and have fresh seals in them. (Old seals will sometimes leak because synthetic cleans so well.) There is also a good oil additive, ZDDP Plus -http://zddplus.com/- that can be added at each oil change when using modern oils without enough zinc.
Happy Motoring!
JT
 

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Hi Kyle,
Can't answer the last question but for the oil you need to make sure the oil has the proper level of zinc in it(.I believe it's 1200 ppm or more.) It has been removed from most oils in recent years(by the EPA because of catalytic converter damage) but is needed for older flat tappet engines such as is in you Mustang. I use Amsoil synthetic 10W-40. And I would definately recommend a synthetic for engines that have been overhauled and have fresh seals in them. (Old seals will sometimes leak because synthetic cleans so well.) There is also a good oil additive, ZDDP Plus -http://zddplus.com/- that can be added at each oil change when using modern oils without enough zinc.
Happy Motoring!
JT
I've use Amsoil 10w-40 in my '65 289 since 1982.
 

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Another thing to check is the head. Casting number will be to the left of carb on top the intake log. If matching, it will be C6?? also.
 

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Your engine block may have a C5 date code. I've seen six cylinder cars from 1968 that came with an engine block date coded for 1965. Apparently, Ford was too lazy to change the numbers in the mold.
 

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All iv used in my '66 289 is Quaker State 10-40. Its still running fine after 200,000 miles.
 

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Underneath the engine, between the starter and oil pan will be the engine casting number and date code. Its usually hard to read from underneath the car, in the tight space between the starter/oil pan, and with the oil/grease buildup thats probably covering it. However, it is possible to read if you can clean it off some and have a good flashlight. Write down the numbers and google "mustang casting number decoder"

If you're looking at the front of the engine, just to the right of the distributor and below the driver side head will be a small flat piece sticking off the block with numbers/letter stamped on it. This is the engine assembly date code... the exact date the engine was actually assembled

Also, in the lifter valley under the intake manifold there will be 289/302 stamped on the block itself. If you take the valve cover off there will also be 289/302 stamped onto the top of the cylinder head as well. The heads could have been swapped out however.

+1 for 10w40 synthetic oil
 

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Underneath the engine, between the starter and oil pan will be the engine casting number and date code. Its usually hard to read from underneath the car, in the tight space between the starter/oil pan, and with the oil/grease buildup thats probably covering it. However, it is possible to read if you can clean it off some and have a good flashlight. Write down the numbers and google "mustang casting number decoder"

If you're looking at the front of the engine, just to the right of the distributor and below the driver side head will be a small flat piece sticking off the block with numbers/letter stamped on it. This is the engine assembly date code... the exact date the engine was actually assembled

Also, in the lifter valley under the intake manifold there will be 289/302 stamped on the block itself. If you take the valve cover off there will also be 289/302 stamped onto the top of the cylinder head as well. The heads could have been swapped out however.

+1 for 10w40 synthetic oil
He has an inline six.
 

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His casting number should be easily seen next to the exhaust head pipe.
 

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If you want to get technical there are no "numbers" matching cars as there was no way of tracking whether the engine was the one originally put in the car. It is possible to have a block other than a C6 put in your car at the factory level. I have seen it before in an original owner car.

But for the most part as people have said check the passengers side of the block just above the oil pan. It will be partly behind the exhaust pipe but clearly visible if the motor is clean. As was said C corresponds to the 60's (D-70's ect) and the number following refers to the year. Good luck.
 

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Discussion Starter · #13 ·
Damn all of you have been very helpful. This is my first project car and I think since I have awesome people to help me out it will go very smoothly. It turns out that it's an original I-6 from 66 I think it's a 200 but i am not sure.

Thanks again
 
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