70's engine swappers, here's a question
 

Home made 4x4 frame, want to drill the perch holes, so here we go.

The "constant" is going to be the bellhousing location, that will never change..... as if it was in a '73-79 4x4.

Here's what we know (I think, lol): The FE and 300 use the same perches, only in two different locations, up through 1976. They have a top bolt spacing of 2.5".
The later 351M/400 perches allow a 351W, 302, 351C to drop in directly. They have a top bolt spacing of 4.25"
The later 300 perches are different than the earlier 300/FE perches. They have a top bolt spacing of 3.38"
... so relocating the 300 perches to put an FE into a '78/79 is not just a matter of moving those perches to the rearward holes. Also, one can not just bolt in a set of 351M/400 perches into a '76 or older truck.

Now, here's what we don't know, but read about: The FE can drop into the 351M/400 perches, but moves the engine 1 inch. Which direction I dunno, but keep in mind the bellhousing will not move regardless of engine.
... so which direction does the FE move when installed in a '78/79? And so vice versa, if you drop a 351W into an older FE perch truck, it would move the engine the opposite direction 1 inch. (I have about 14" from motor mount bolt to bellhousing for a 351M, and 351W)

What we don't know, but want to know: If using the earlier 300/FE perch with the 2.5" top bolt spacing, I would have the holes drilled for the 300 up front, then the FE hole rearward, and if I have to compensate an inch for the other engines, where would they be? to move the 2.5" top bolt spacing 1 inch, I'll end up with a swiss cheese frame rail, and that is not good. But if there is no 1 inch difference, then all is well, I can use an older 300/FE perch....here's hoping.

So if anyone can help out here, I'm grateful.

EDIT: If it helps any, I believe the 4 speed frame rail linkage bracket locates the same regardless of engine?

I thnk you need to keep in mind that the frames changed. 73-77 'highboy' frames are onedesign, and the 77-1/2-79 frames are different (married transfer case design). From my experience, the engine perches do not interchange.

engine towers ormotor mount frames regardless of how you label them are indeed different depending on engine family..i.e: (302-351w or 351m-400 or 352-360-390 or 429-460) and only certain ones interchange... the 73-77 250 uses a differant crossmember assembly than the 78-79 250 so those mounts also differ and all the 100-150 mounts are the same as the 78-79 mounts, again depending on enginge family...the 2 wheel drives are yet also differant...i think your bes bet is pick a motor family and install the motor mounts/towers for that engine....

I've got the perches for '78/79 300 6 4x4, the 351M/400 4x4 (302, 351W, etc...) and I need the perches for the F100-150 FE 4x4. Then I'll have all three for my frame. This is going to double as an engine/trans testing stand, so locating the holes for the perches is preferred. However, going with all of the different perches, I'll end up with a swiss cheese area of the frame. When I measured the highboy 4x4 ('76) the perch distance was different than the '78/79 300, and that's what threw me off. So, if the earlier 300 6 perch is the same as the FE, then the top bolt spacing should be the same, only located differently on the frame. What I couldn't do, was remove the perch to look at the frame top, and see how the holes located. If there's only 3 holes, then the FE and 300 share the middle hole, IE the 300's rear hole becomes the FE's front hole. But if there are 4 holes, then I need to know the distance between the two middle holes.

I've had some time to think this over and I'm thinking I'll need to find an earlier pair of 300 6 4x4 perches, and not use the '78/79 300 perches, and just keep the 300 6/FE 3.38" type perch for both locations. Now I just need the bolt hole locations as mentioned, 3 holes or 4?

if you want all the original frame mount locatios meusure a 1/2 ton 4X4....it should have all the frame hole locations for any engine...ford never changed the from 73-79...and the 1/2 ton 300ci are supposed to be the same as the 390 towers...

I did that. I have a '79 Bronco that I put a 300 in, and a '78 F150 4x4 w/351M. The 300 perches in the Bronco don't match the bolt holes of the 351M perches. Therefor if the FE is supposed to move to the opposite holes of the 300, then it won't work. Along with the master parts and accessories catalog I have, it lists several different part numbers for these perches, but they don't display measurements. Since the FE was discontinued, and the 351M/400 took over, then the perch was changed, and so were the bolt holes on the frame. Unfortunately I don't have an earlier 4x4 with an FE.

Comparison Photos of Engine Perches - FORDification.com In this link it explains a bit, but it doesn't give the top bolt hole measurements.

Here's a pic I found showing the frame where the perches would go on a '79. Notice the 8 holes on the inboard face. Also notice there's only 3 holes on the top, and that the forward hole is located closer together than the rear hole. This appears to be different than early '77 and older highboy, but I can't confirm it to be the same on the '77 and older half ton.
http://i320.photobucket.com/albums/n...framefront.jpg

I'd love to know the differences as well as I am contemplating making a jig for the cummins motor swap mounts I made when I put the thing in my '74 crew cab F-250 (high boy).

While I don't have a 78/79 frame to mess with yet (may happen Saturday) I do have the high boy style. Here's a couple pics - which are not as good as the one you found. While it is similar to the 78/79 you post I agree with you in thinking they are not the same. There are the 8 holes there and then the 3 on top, but they might be in different locations fore and aft...

Keep in mind the cross member under the engine was being cut down for the cummins swap - so that is not stock.
http://i453.photobucket.com/albums/q...0swap/x249.jpg
http://i453.photobucket.com/albums/q...wap/x253-3.jpg
http://i453.photobucket.com/albums/q...wap/x251-2.jpg

Do your top bolt holes measure 2.5" in between each one? By virtue of 3 bolt holes on your frame, that tells me the FE and 300 share the same center hole, and if they use the same perch, then they should be an equal distance in theory. That would help me a lot. The next step in all of this, is to find the location of the engine mount bolt, and triangulate that with the top frame holes. Knowing the distances, I can trig it out, and compare the '78/79 300 perch holes with the earlier holes to determine if they are the same fore and aft..... again, in theory, lol.

Based on a drawing I have here that I did for a buddy a while back I've got:
0<--2.5"-->0<--4"-->0<--3.25"-->0 I THINK the 2.5" spread is toward the rear of the truck but I'm not positive and can look tonight.

Those measurements are on the CL of the holes too - just hard to draw that here.

Also there is a 3.5" vertical gap between the top row of 8 holes and bottom row.

I think a light just went off in my head. I'll dare to say the only interchange between FE and 300 6 perches is in a 2wd truck, and that the 1" difference I read about between them and the Windsor/335 series is the 1" in height. The lower half of the Windsor and 335 series blocks are the same, which are not the same as the 300 or FE.

I would dare guess the FE and 300 6 use different 4x4 perches. That link I posted only says FE 4x4 perches, it doesn't say FE/300 6 4x4 perches. It doesn't go into any depth about the 4x4 beyond that.

here's my '79 Bronco centerlines: 0<--3.38"-->0<--4.25"-->0 The bellhousing surface to motor mount bolt is 17" on the 300, and 12" on the 351M. I have an FE with no motor mounts, and so I've estimated it to be either 12" or 14" for that one.

The tentative bolt hole measurements you have certainly show the 300 and FE would be different bolt hole distances, so the perches are probably different. I would like to verify this, as this will change everything. :eek:

And all along, I was thinking the FE and 300 6 used the same perch for the 4x4. Hopefully someone can prove this as well.

In my manual, it shows the 300 6 4x4 left side perch as C6TZ-6029-E and the FE as C6TZ-6029-F

I wonder if being a crewcab, yours may be different than anything else?

From what I have read - crewcab specs are the same as the "highboys". I have the FE motor mounts that came out of the truck for sale in my parts thread if those might help you.

Are they handy to measure the top holes on? I'll check out your parts thread.

I can grab them at the shop tonight and look.

Parts thread link - pretty much all parts are listed in the 1st post
73-79 parts - LOTS - Page 26 - Ford Truck Enthusiasts Forums