frame perches
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Freshman User
Joined: Jan 2013
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From: nebraska
frame perches
does anyone know if there is a difference in the frame perches on a 2wd crew cab from a 390 and a 300 six? i pulled my 390 and put in a 300 and moved my perches forward to the next set of holes in the frame but they are still to far back. so i bolted the perches to the 300 mounts and set it down and the holes are off by more than an inch. iv done this swap on a 4wd and i dont remember needing to drill new holes or anything . the info i find online says the 300 and 390 should use the same perches but i cant find any info that says if the are the same on the crew cab trucks or why moving them didnt work. the motor looks like it may be sitting a little high too.
Senior User
Joined: Jul 2003
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Take a look at the link that EP145 gave in post #2 when you asked this question a week ago https://www.ford-trucks.com/forums/1...e-perches.html
The information hasn't changed, the FE and I6 perches are the same, take a look at the pictures and make sure you have the right ones. Are you SURE the engine you removed is a 390, and are you SURE it had the correct perches to begin with? I think you may actually have 302/351/400 perches, if you aren't the original owner you don't know for sure what someone else may have done in there. Post a picture of the perches you have and it may be easier for someone to help identify what they actually are.
The information hasn't changed, the FE and I6 perches are the same, take a look at the pictures and make sure you have the right ones. Are you SURE the engine you removed is a 390, and are you SURE it had the correct perches to begin with? I think you may actually have 302/351/400 perches, if you aren't the original owner you don't know for sure what someone else may have done in there. Post a picture of the perches you have and it may be easier for someone to help identify what they actually are.
Hotshot
Joined: Apr 2009
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From: Stanley, VA
On 2WD mounts crew cabs are the same as regular cabs,
This is what the parts catalog says,
Engine support bracket
73/74 2WD w/ 300 6 cylinder
RH D4TZ-6028-B
LH C5TZ-6029-A
75/76
RH C6TZ-6028-D
LH C5TZ-6029-A
73/76 2WD w/ 360/390
RH D4TZ-6028-B
LH D4TZ-6029-B
It shows the RH tower is the same part number but it doesn't go into the details of what the differences are between the different part numbers.
This is what the parts catalog says,
Engine support bracket
73/74 2WD w/ 300 6 cylinder
RH D4TZ-6028-B
LH C5TZ-6029-A
75/76
RH C6TZ-6028-D
LH C5TZ-6029-A
73/76 2WD w/ 360/390
RH D4TZ-6028-B
LH D4TZ-6029-B
It shows the RH tower is the same part number but it doesn't go into the details of what the differences are between the different part numbers.
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Freshman User
Joined: Jan 2013
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From: nebraska
the motor i pulled is definitely a 390 and as near as i can tell was the stock motor in the truck . and i just looked at a 78 f100 2wd with a 300 that is factory and a 1 owner truck and the left mount is shorter than mine and looks a little different shape . and then i went and checked another truck that i know is the original 77 390 and his perches are identical to mine. so if your parts book is correct those two trucks and mine should all have the same frame perches.
Ford Parts Specialist
Joined: Nov 2006
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From: Simi Valley, CA
The motor I pulled is definitely a 390 
and as near as I can tell was the stock motor in the truck.
And I just looked at a 78 F100 2wd with a 300 that is factory and a 1 owner truck and the left mount is shorter than mine and looks a little different shape.
And then I went and checked another truck that I know is the original 77 390 and his perches are identical to mine.
So if your parts book is correct those two trucks and mine should all have the same frame perches.
and as near as I can tell was the stock motor in the truck.And I just looked at a 78 F100 2wd with a 300 that is factory and a 1 owner truck and the left mount is shorter than mine and looks a little different shape.
And then I went and checked another truck that I know is the original 77 390
and his perches are identical to mine. So if your parts book is correct those two trucks and mine should all have the same frame perches.
On sale day, 360's magically become 390's!
360/390 look identical, share the same block, the bore is the same (4.05"), the stroke is different.
Measure the stroke to determine engine size. 360 = 3.50" / 390 = 3.78."
Engine supports: 6028 right & 6029 left ~ Parts catalog pics: Left: 240/300 / Right: 360/390.
Senior User
Joined: Jul 2003
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Like NumberDummy said, 390s were never original in a 1977. The truck probably came with a 302/351M/400 and IF it now has a 390 then someone may have dropped it onto the original 302/351M/400 engine perches, as the 390 will physically bolt in without changing them. If yours are the same as his then therefore you also may have 302/351M/400 perches.
What is the fourth digit of your VIN? Also, what is the fourth digit of the VIN for the "original 77 390"? That will at least tell us what engine the trucks originally came with and may give an indication of the perches, though not for certain as they also could have been changed. For example, my truck's VIN starts out F26Y... The "Y" means it came from the factory with a 360 engine.
Can you post a pic of the perches you have, from multiple angles if possible?
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67nukeford
1967 - 1972 F-100 & Larger F-Series Trucks
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Jan 16, 2008 09:38 AM
