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'56 302/c4 swap - can stock crossmembers stay in?

 
  #1  
Old 12-04-2010, 04:41 PM
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'56 302/c4 swap - can stock crossmembers stay in?

Iím making good progress on my 56 F100 in grease scraping, so am looking at soon
ordering my engine and transmission mounts for the swap.




I whipped out my tape measure and compared the engine/trans mounts to the current frame mounts.

It looks like the current frame mounts can be left alone/in and just add the new 302/c4 mounts.

Is this true? Is there someone who can verify for me that my stock engine and transmission crossmember can be left in/alone?

The truck came originally with the 272/Fordomatic and Iím leaving in the stock front suspension.

Thanks!!
 

Last edited by AmericanROCKBREAD!; 12-04-2010 at 04:43 PM. Reason: add eng photo
  #2  
Old 12-05-2010, 11:37 AM
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Not usually. The problem with that crossmember, is that it makes it hard for headers with any thing other than a stock engine. you'ld have to mount the engine high enough to clear, and that may make it look funny. Personally, I would make sure of where you want the crossmembers to go, and mount the engine one in there (with bolts, not welding), then remove the original (by cutting off the rivets, and saving it) then mount the tranny one. Usually, unless you move the engine so that it clears, it will interfere with the oil pan being removed while the engine is in the truck, or it can interfere with servicing the transmission later. You could, possibly, have some luck leaving it, if you use a set of shorty headers, like for a later Mustang or something, but still mounting the engine high enough to clear. I think the motors being mounted high makes the projects look a little strange, or somewhat tacky, but that is my opinion.
 
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Old 12-05-2010, 01:33 PM
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I left the crossmember in place and had no problem with the height of the engine or the headers. Here is a pic of my setup showing the trans, crossmember, and the exhaust system that I was in the process of fabricating when this pic was taken. It is my own personal opinion that this crossmember is critical to the structural integrity of the chassis in that it provides the bracing needed to counteract the rotational forces applied to the frame by the cab wings. This trans is an AOD but I started with a C4 and changed direction before the cab was mounted.
 
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Old 12-05-2010, 01:34 PM
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i left mine in with a c4 302, didnt have any issues, but i converted to a firewall mount brake master cylinder. The main reason i left mine in was advice from a guy who has fixed some messed up frames. He said when you remove that bell housing crossmember the frame horns that hold the front of the cab up eventually start sagging due to frame twist. that crossmember did more than hold up the engine. it kept the frame from twisting. just my 2 cents.
 
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Old 12-05-2010, 02:17 PM
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I stand corrected.....awesome. The one like that in the Chevies (most recent project like that I've dealt with) has to come out. The cross member can be removed though, BUT you MUST install at least one of the replacements before removal to address the potential twisting mentioned above. Personally, leaving them in looks tacky when trying to make a clean build, but that is my opinion.
 
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Old 12-05-2010, 05:11 PM
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I cut the cross member on my 55. The reason being the C4 transmission would be very difficult if not impossible to remove with it in place. I cut the cross member on both sides, welded"arms" out on both sided of the cut piece of the cross member then replaced the cross member bolting it back together through the "arms" That allowed the cross member to remain a structural part of the frame support and then be removable for servicing. The "arms" are inside the crossmember and not noticeable until under the truck and see the arms inside the cross member. Kinda hard to explain but hope you get the idea.
Larry
 
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Old 12-05-2010, 06:05 PM
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I see your point there larry, the cross will need to be removable, or the tranny won't be removable, unless the body is lifted, or the engine removed too.
 
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Old 12-06-2010, 11:17 AM
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CROSSMEMBER ADVICE - THANKS!!

wmjoe1953 - Thanks for your input and working through the crossmember qusetion. Your input is appreciated.

Charlieled - GREAT photos! This is what I was hoping for because I'm not a fabricator and am doing my project in a residential neighborhood in my garage. The least amount of fab to my frame, the better for me.

55F100tx - Thanks for more support in the leave in category. The experience of you folks that have done what I am doing is valuable.

larryb346 - A approach that combines the best of both worlds. I could only hope to meet a fab guy who wouldn't charge an arm and leg to do some work for me (and lend me a car trailer).

THANKS AGAIN TO ALL. JUST THE INFO I WAS LOOKING FOR!
 
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Old 12-06-2010, 11:35 AM
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Something you could do, is get some small box steel, or even some flat strip, and make "connecters" for the original. Using grade 8 hardware, you could drill holes through the crossmember, and cut it on both sides, using the "connectors" to reattach it. Using box steel tube would be ideal, and it wouldn't be hard to do. You would maintain the support of the original, and be able to remove it for transmission access.
 
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Old 12-06-2010, 05:08 PM
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With the small size of the 302 and auto trans, I would leave that crossmember in place. If you remove it, over a period of time the front cab mounts will start sagging.
 
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Old 12-06-2010, 06:41 PM
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Americanrockbread.
I think you will find once the cab and other parts are installed you will not be able to remove the transmission with that cross member in place.At least that is positivity the case in my 55 with a 302/c4.
If your limited in tools you could use a hacksaw or cutoff tool and cut the cross member on each side to remove it, leaving a couple inches on each side near the frame. It would take some work but could be done with very few tools. Then you could use 4 steel plates about 6 inches long and a inch or so wide. I would use 1/4 inch thick plate. You could then take the removed piece to any place that welds and they would easily weld the plates to your removed piece leaving about 1/2 sticking out the ends of the crossmember. When you returned home you could hold the piece back in the original position and drill the solid part of the crossmember and through the plate and bolt it back in place. I would put one plate on each side of the removed piece (front and back) and each end making 4 total pieces needed. The cross member is in a inverted "U" shape so the plates would go on the inside of the "U" so wouldn't be seen once installed. Once bolted back in place it will support the frame rails as well as it did before you cut it. If others can remove the transmission with that crossmember in place, they have something different than I have.
Larry
 
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Old 12-07-2010, 12:28 PM
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Leaving in stock crossmember

Hello:

BBKtech2 - I'm leaving it in! I'm convinced that for me, this is the best way to go.

Larryb346 - Thanks for your suggestion regarding a simple fab. I do see the issue with removal of the transmission. I'm not removing my cab at this time and I'm sure I can get the engine/trans unit in up and over the stock crossmember.

If I end up needing to work on the transmission, I'll take the engine/trans out as a unit - I'm imagining that it won't be often that I'll need to pull the trans once I'm up and running. The front end can be removed as an entire unit, so with new nuts and bolts, it won't be that tough to get to the trans if needed.

All that said, it's possible that eventually I'll have something fabricated, but in the mean time, there's still PLENTY for me to spend $$$$$ on.

Joe
 
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Old 12-07-2010, 01:11 PM
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So....even if I have a fat MII crossmember a few inches forward, you think I'd need something to tie the frame together at the cab mounts?

Dan
 
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Old 12-07-2010, 01:30 PM
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Yep. I never saw a problem with the sagging front cab mounts when I did a Camaro subframe and removed the stock trans x-member, but my boxing plates for the Camaro welded to the area around the cab mounts. With the Must II's the rigidity of the Must II x-mamber is to far forward of the cab mounts to help.
What you'll notice over time is the cab's floor pan lip that sticks down, slowly working it's way down to the frame as the mounts sag down. In a truck with tight hood lines, this could cause a problem in the future.
 
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Old 12-07-2010, 01:43 PM
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Could you not just convert the rivets to bolts and the then the cross member would be removable?
 

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