'72 K5 - Greg's @MightAsWellK5 Build

[folkenheath]

This seems totally do-able... Given that I cut the pan directly over that main bearing cap, what sort of clearance do you all thing is realistic?

-G

Are you talking between the oil pan and suspension or the oil pan and crank/rods?

Here's my take. Yes, you might be able to get it so there is a notch in the oil pan. In my post above I mentioned .050" inch absolute minimum clearance for the rotating assembly, this is from clearancing blocks for stroker cranks.

However, say you do get that clearance and your panhard now clears the oil pan, now your safety factor is gone. Stuff bends and flexes, and if you have to clear your oil pan for the panhard, then if the panhard does ever hit it during a hard manuever or something, then most likely you are going to cause engine damage when a sturdy steel bar contacts a rapidly rotating crank and rod.

With that said, my oil pan does look to have more clearance under it then yours does in that location, but I don't like putting moving components that close to it either. I left considerable clearance under the oil pan for when stuff flexes under loads. If one bar hits another bar, no big deal, one of them will probably bend a little but you'll still get home. But if something hits your crankshaft, it may easily be catastrophic.

So in my opinion if you need to clearance the oil pan to run a bar through there, you are running it too close. I would rather you have more room under the pan, then if you contact the pan, you know you need to address an issue, but at least you are less likely to actually cause engine damage.

 

[Greg72]

I was talking about the about of free space that's likely to exist on the inside of the oilpan around that bearing cap... If there's 1" of gap between the two, I wouldn't feel all that guilty stealing 1/2" of it to get the notch I need.

It's not 100% clear to me just HOW deep of a notch I'll need yet. I totally appreciate what you are saying about a catastrophic failure, but this interference is ONLY an issue under full bump (6" uptravel) for both wheels simultaneously (basically landing off a hard jump)... for 99.9% of the activity the PHB is not going to be anywhere near the oilpan.

I was already planning to have a set of "failsafe" bumpstops worked into this design.... the ORIs have an internal bumpstop, and you're not SUPPOSED to need anything else, but it feels safer to have some kind of structure in place to keep the struts from puking their guts out or tearing free of the mounts when the truck comes back to earth for a landing.

One of the things with linked suspensions is that the amount of "flex" or "odd" cycling that could happen with leafsprings and shackles is supposed to be eliminated. When you cycle the suspension in the shop....what you see is what you get in terms of clearances and fitment. Stuff happens, and I'd never want to leave the "thickness of the paint" clearance like Brandon mentioned in previous posts... but it's awfully hard to leave 1/2" - 3/4" of clearance around things in anticipation of bent parts, etc.

There is always the option to raise the engine (again) for more room, or at least when I notch the pan make sure that the notched section uses a heavy gauge steel and perhaps build a small "girdle" brace around it that helps spread the loads back down into the oilpan bolt area That way, if I do ever get a strike on the pan, it's a lot less likely to collapse onto the spinning crank.....

Maybe.



-G

 

[folkenheath]

I completely agree you can't leave 3/4" clearance around everything, I didn't, some places I have less than an 1/8". But the crank is one of them where I did leave a lot of clearance. As you know, you have to build some things for worst case. Yes, 99% of the time there will be a lot of clearance there, but one hard landing and you'll be wishing you had more if it actually does hit the crank. Crank clearance is not something I skimp on when it comes to moving suspension parts. I know links are way more firm than leaves, but stuff still flexes, especially when it comes to kinetic energy. Thats the difference from being able to drive away from everything but a hard landing, or driving away from a hard landing as well.

 

[Greg72]

Point taken.

If I can notch the pan while maintaining internal clearances to the rotating assembly, and also gain 1/2" - 3/4" of space between the PHB and the notch (while also incorporating very high-durometer bumpstops under each framerail for the axle to crash into when SHTF..... that might be adequate margin.

-G

 

[kgblazerfive]

How much comparable effort would it be to stretch the wheelbase 3-5 inches and fix just about all the issues you are dealing with. It would create different ones however less critical like stretching the wheel wells.

 

[Greg72]

How much comparable effort would it be to stretch the wheelbase 3-5 inches and fix just about all the issues you are dealing with. It would create different ones however less critical like stretching the wheel wells.

Sweet Jeebus!!

.....adding wheelbase at this point in the design/build is NOT a trivial task.


All of the suspension design and link placement (both front AND rear) was based on a 107" wheelbase. I can't even imagine the amount of effort it would take to go back and rework everything that's already been completed.

But I guess the simplest reason is that moving the front axle forward another 3 - 5" would look like total a$$. The proportions of the front fenders would be completely wacky with a huge new "stretched" section near the door hinge, with almost no fender left in front of the tire where the turn signal normally resides. YUCK.

I'm 90% of the way done with the front suspension now.... I guess that sometimes when I get into the minutae of each step it might make it seem like I'm still miles away from completing it. The fact is that the stuff I'm dealing with isn't really all that major compared to all of the pre-planning and building that has gotten me to this point. Yeah, I've got a PHB clearance issue to sort out, and my PS framerail is getting a bit too "notched" for my liking.... but those will resolve themselves in the next couple of weeks. The mounts for the struts are looking pretty simple based on where I plan to put the lower eyelet mount.... and the upper mount will be only slightly higher than the engine cradle tubing that's already installed, so I don't forsee any hood clearance issues when I get to that step in the build.

It's all about refinements at this point..... the major parts are looking good. I just need to leave them alone now and focus on the fine-tuning.


-G

 

[kgblazerfive]

Ok was just wondering

 

[ashman]

Sweet Jeebus!!

.....adding wheelbase at this point in the design/build is NOT a trivial task.


All of the suspension design and link placement (both front AND rear) was based on a 107" wheelbase. I can't even imagine the amount of effort it would take to go back and rework everything that's already been completed.

But I guess the simplest reason is that moving the front axle forward another 3 - 5" would look like total a$$. The proportions of the front fenders would be completely wacky with a huge new "stretched" section near the door hinge, with almost no fender left in front of the tire where the turn signal normally resides. YUCK.

I'm 90% of the way done with the front suspension now.... I guess that sometimes when I get into the minutae of each step it might make it seem like I'm still miles away from completing it. The fact is that the stuff I'm dealing with isn't really all that major compared to all of the pre-planning and building that has gotten me to this point. Yeah, I've got a PHB clearance issue to sort out, and my PS framerail is getting a bit too "notched" for my liking.... but those will resolve themselves in the next couple of weeks. The mounts for the struts are looking pretty simple based on where I plan to put the lower eyelet mount.... and the upper mount will be only slightly higher than the engine cradle tubing that's already installed, so I don't forsee any hood clearance issues when I get to that step in the build.

It's all about refinements at this point..... the major parts are looking good. I just need to leave them alone now and focus on the fine-tuning.


-G

...so, that's a no then?

 

[Greg72]

...so, that's a no then?

Perceptive!

I really do spend a LOT of time considering the options when I run up against a problem....

To be completely fair, I probably don't spend enough time explaining my entire thought process around here. There are so many specific things that I want (and don't want) to happen with this build and I'm constantly running through that entire list each time I need to make an important decision on how something will be built.

The body and wheelbase MUST look as stock as humanly possible, that's non-negotiable..... So I can't stretch the wheelbase any further, even if it would save me time.


-G

 

[MNorby]

A plan B if all else fails could you set your inboard bumps lower so at full axle bump it will limit to say 5" up but under flex since the bumps would be inboard they wouldn't hit and would allow full flex uptravel. If that makes sense.

 

[4X4HIGH]

Greg, you should REMOVE the oil pan then cycle the suspension and see how close things get to the rotating assmebly and THEN check to see if there is room to "notch" the pan the amount needed in the location you need. You would need to pull the pan anyways in order to cut the pan. Also don't forget to rotate the crank in such a way to have the worst case scenerio of counter weight/connecting rod in the area that needs clearance.

 

[76zimmer]

Plan C.....put a short stroke SBC crank and 2 bolt caps in it and butcher the pan!

 

[Greg72]

A plan B if all else fails could you set your inboard bumps lower so at full axle bump it will limit to say 5" up but under flex since the bumps would be inboard they wouldn't hit and would allow full flex uptravel. If that makes sense.

....I see what you did there! Good idea.


-G

 

[imiceman44]

....I see what you did there! Good idea.


-G

That is the way to go when you have a problem area in the middle.
I was working on a design where I have 2 soft shocks on the ends and a couple in the middle to make a flexy side to side suspension but stiff on jumps.
Same idea but for a different reason.:thumbup:

 

[TheBeast_88K5]

 

[imiceman44]

That is the way to go when you have a problem area in the middle.
I was working on a design where I have 2 soft shocks on the ends and a couple in the middle to make a flexy side to side suspension but stiff on jumps.
Same idea but for a different reason.:thumbup:

By the way I have refrained from commenting until now but dude stop the butchering.
Also on the PHB and drag link:
If they are equal length and parallel to each other you will not get bump steer.
If they are parallel to the axle lateral movement is minimized. Also the length help to.
I would worry more about bump steer and less about the other.
Just my 2 cents.

 

[Greg72]

2013.02.09 - UPDATE! - ...AND HERE WE GO!!!

As I've said previously.... It seems like I'm 90% there with the front suspension mockup at this point. But mysteriously, there is a lot more than 10%-worth of hours left to get things wrapped up. Fortunately for me, I had squirreled (did someone say "SQUIRREL!?") away a 3rd set of framerails along the way.... Though with the snowstorm we just had, i had to wade through about 3' of snow to get my hands on it and drag it into the garage.

It was a bit of deja-vu all over again. As I'd done for the frame boxing process originally, I cut the framerail down lengthwise to get a consistent width across the upper and lower rails (roughly 1-1/8") and then clamped the first piece into position to get my new "high-clearance" framerail started.

The objective with any sort of extreme frame modification is to avoid doing a bunch of straight vertical cuts where the parts will be grafted together. To that end, I spent quite a bit of time working on a template that would avoid those sorts of unions... You can see in this photo that I did a v-shaped pattern for both the forwardmost section, and for the joint where the 2nd new frame section will ultimately go.

The final step for the day was laying in the 2nd half of the new frame section. I ran out of time, so it's not fully seated flush yet, and the overlapping section is currently hiding the "interlocking" v-shape where the two halves will be dovetailed to each other.

Not bad.


I end up with 2-1/2" of crucial "extra" space underneath the framerail... Plenty for the pumpkin and the PHB link.

Next step will be to cut out a 1/4" thick reinforcement plate to go on the inside of that new framerail that precisely follows the shape (from well before the first frame joint, and well beyond the last joint). That will allow me to strengthen the entire structure and eliminate any concerns about a single weld-joint failure in the future. The inside framerail (closest to the engine) will get that same 1/4" backing plate. Overkill perhaps, but not worth taking a chance to save a couple pounds of steel.

Once this frame mod is completed, I can move on to the butchering of the oilpan.


-G

 

[cybrfire]

That's awesome and cwazy all at the same time.

 

[Greg72]

Cwazy™


...I like that.

Definitely feels that way sometimes.


-G

 

[bp71k5]

Its like one of those movies where you think you have the plot figured out, but then a big twist gets thrown at you.

Are you going to use the new sections to completely replace that part of the old frame, or sandwich the old frame with the plates and cut away the low hanging portion?