I'm looking at installing a 4.6 in my 65 M100 and have to make a decision about front suspension upgrades. I have the 78 I-beams/disc brake set up ready but am also looking into the crown vic swap. Someone recently mentioned that pro shops do not do this swap. Anything I should be aware of before I decide what route to follow?

 

I am currently waist high in my swap, and I am going about a it in a different way the previous people's. If you do it the way Car-Crafter did it I could of done it in 3 days, and I wouldn't have to take the front end off the truck. I am sectioning the frame so my final ride height will be around 5 inches at the frame with enough clearence to be do-able.

None the less it gets right down to what you want as a truck owner. The I-beams can be bent for a 2" drop, and look great with 17's and modern SUV tires. The 4.6 is easy enough to fit into an I-beam truck, but motor mounts can play hell from what I have heard.

The CV front end is superior in every way in a street driven sense compared to I-beams, but do you plan to go off road? The CV front end always lowers a truck. How much depends on how you tweak the installation.

I think a proper shop would have no problem with the swap, but you'd probily have to show them how others have done it to ease there worries. If you lived near me I would do the suspension part of the swap for you, and you could re-install your motor later.

 

im interested on how you are doing your swap ziegelsteinfaust i dont care for how high they set after the install i want it to set a few inches lower the 5 inches off teh ground would be the ticket!

 

I will do a write-up after I finish in a couple of weeks.
From I see as I have been going through the install is the way I am doing it is the lowest one can go before you Z the frame. The problem with Z'ing the frame is that where the cut has to be made is right under the middle cab mount. Which practically makes it a no go unless you wanna modify the way the cab mounts.
So the way the I did it with sectioning of the frame to accomodate another 2.5 inch drop is about the only way.
Also I can still drop it 2-3 more inches on the springsfrom what I heard.

 

ill be watching.

 

I would definitely like to see some pictures Ziegel. I am going to be laying my 63 uni on the ground and want to do the Crown Vic but wasn't sure how to go about it.

 

Here's a link that may be helpful deflayted.

https://www.ford-trucks.com/forums/7...o-67-f100.html

 

I have a few pictures here.......... Ford Truck Enthusiasts Forums - CTom's Album: Crown Vic front end...............

 

A question,

How was the engineering issue overcome of placing a cast aluminum cross member that is designed to be fully cradled and restrained from any flex or movement by the unit body construction of the donor Crown Vic vehicle, and then mounted on to a ladder type truck frame that flexes by design?

How was the stress/flex metal fatigue life cycle of the cast aluminum caculated as the truck frame flexes?

I, along with some highly rated aftermarket suspension designers would like to know the secrets.

Garbz

 

Hey Garbz, how much does the truck frame flex from front to back and side to side, especially with the cab bolted on? Is the problem just that the crossmomber is cast aluminum or that it bolts in and not welded in? I've seen you post a couple tomes about this issue and just wondering?

 

Just watch the box on your truck as it moves up and down left to right as the frame flexes. If it did not flex it would break from fatigue. The cab leans one way and the box the other. This flex happens every time you enter your drive if is it is above the elevation of the road or a parking lot or an off camber turn. The steel of the frame is designed to do this along with the cross members to allow a bit of give. this is why there are rubber pucks at the cab and core support mount points to absorb some of the flex and prevent sheet metal stress damages.

Slick frames are a riveted ladder construction and if the front left is raised by the suspension the right rear will dip with the right front and left rear remaining the same. It is one of the reasons the uni failed as under load the frame flexed and the body did not causing the doors to open or jamb shut.

The Crown Vic is a unitized construction vehicle. The mounting points are rigid and unmoving with engineered forged steel inner steel mount points that are encased within the sheet metal structure and held in place with resin glues. The CV cross member is cast aluminum and is not designed to move with a frame. it is engineered to be a rigid mount point for suspension attachment. If you really look at one when it is mated to the car on the line as a component with the engine in place on the mounts and all the suspension attached. It was made for ease of production and install not a cool piece to be used for suspension on a truck with twice the front weight bias of the car it was intended for.

And lets get in to weight. Yes the CV and a truck weigh similar on the scale but that means jack. The CV has a 50/50 weight bias front and rear. A truck has a 70/30 weight bias meaning that most of the weight under normal driving is on the front wheels. This load increases exponentially as brakes are applied as more bias is shifted to the front.

Remember this is a casting not a forged piece. It has potentially the same metallurgical strength as the pot on your stove.

But then again i may be wrong.

Garbz

 

Ok so I get the frame flexing thing, but how much can the frame flex in the front where the CV x member is bolted in. That seems like a pretty short distance between the firewall and the core support for the frame to flex enough to harm or damage the x member. I can't imagine it would have any flex when the original twin I beam x member is in there also. Just in the front, I know that the rest of the frame has sopme flex to it. I see my bed move everytime I pull into my driveway. So 20% more weight on the front with the CV frontend in there isn't OK, how could you change it to be better balanced and more of a 50/50 weight.

 

Key is this. Cast aluminum will not tolerate any flex. Even a teensey bit of flex say 1/32" will cause metal fatiuge and ultimate failure. Boxing will not get rid of it as it will torsionally work the mounting bolts. Aluminum is fine in compression but not in tension or torsional loading. When is the last time you have seen aluminum bolts holding any important fixtures together?. If the frame flexes in the rear it transfered the load all the way to the bumper in front. No way around it on a ladder type riveted frame.

Only way to change bias is to add equal weight to the rear axle as the front which is impossible in a truck unless it has a constant load in the bed and impratical for custom suspensions.

A twin i beam frame will torsionaly load just like an eary slick one and you can watch the bed do the same trick side to side with the cab. It is all part of the design.

If any one can come up with any engineering to rebut me please feel free to post it.

Garbz

 

I'm no engineer so you won't hurt my feelings, here to learn. Just a thought...What about bracing the frame in an x pattern under the bed?

 

Would welding all the crossmembers where they are riveted together help the flex issue. Also does the whole frame need boxing or just cab forward. And 1 more thing, the CV frontend made with a steel crossmember would be fine even welded in. I'm asking that last question for the reason of the weight bias. Is the geometry of the cv frontend fine for a truck other than the fact that the x member is cast aluminum.