Questioning the setback plates...

[jeromio]

Okay, I am expecting some skepticism here - actually looking for it.

 

LoneStar's install looks pretty straight-forward. Reproducible. But I'm considering doing things differently.

 

I'm considering (just thinking out loud here), the possibility of completely removing the datsun motor mounts, and instead using the Camaro mounts. Or fabbing something very similar to them. These would be bolted to the Datsun cross member via some cross member extensions.

 

Something like that. The extensions might actually also bolt up to the tie rod mount. That bluish line (PC Paintbrush, oi) is meant to represent the steering shaft. The drivers side Camaro style mount tower would need to be modified to allow the shaft to pass thru.

 

Why would I want to do this? Well, it looks like the standard LS1 low alternator and A/C compressor locations would work with the Datsun mount towers out of the way. So, what I'm thinking is that it would be easier to come up with a different way to mount the engine than it would be to come up with different ways to mount those 2 accessories. And who knows, maybe I'll want to get a blower in there down the road?

 

Also, it seems like this would be fairly straight-forward. Need to get some more measurements and specifics - right now this is only a hair-brained idea. I already have these camaro mount towers - very beefy units. The steering is the only problem that occurs to me right now, and right now it doesn't worry me too much.

 

Basically, instead of setting back the motor mounts, I'd be setting back the motor mount towers.

[pparaska]

I think it's a great idea. Just a bit more fabbing. But I'd consider mounting straight to the frame rail instead, after you reinforce the rails (scab some 1/8" steel on the top, bottom, engine side walls). Yeah, you'd have to put in a "hole" for the steering shaft. Check out the Ford forum, I think firebern did this on his install.

[jeromio]

I did consider mounting to the frame rail like the Ford guys.

 

But, I think this would create more steering interference and also limits header choices. MikeSCCA had to add an extra joint to the steering for example.

 

Also, I kind of like the idea of the forces vectoring primarily downward, vs the motor pressing down on mounting "arms" and also out against the frame rails.

 

I think mostly what I'm shooting for is sort of making the datsun straight crossmember into more of a K style member. The extra pieces would be welded to the existing cross and then bolted to the frame rails and/or bolted to those cast strut rod mounters. I suspect that this will increase the rigidity of the frame as a side benefit.

 

I wish I had an extra cross-member to play around with. Maybe I'll see about picking one up.

[pparaska]

Ah - like a K member. I see now. I like that better. It seems if you did that and mounted to the bottom of the frame rail, behind the crossmember, you'd get away from header AND steering shaft problems. I see now - Cool.

 

I agree the JTR brackets are a bit disconcerting - lever arms and all that.

[BLKMGK]

I started to post this but it sounded silly but since it osunds like Pete might be in the same ballpark I'll toss it out... Some of the 'rods out there look like they use a "cradle" under the motor with mounts on it. Instead of attaching right to the crossmember have you considered a cradle under the motor that would attach to the frame above andor below? I understand you're hesitancy to stress the frame but is the current crossmember not doing this as well? Is it really putting all stress into the suspension or does the frame see some as well? I'm not sure a cradle is any better than mounts right to the frame but I'll toss that out for others to shoot down or not

 

Hrm, maybe run something to both the frame AND the existing crossmember? Or am I restating what you guys are already discussing?

[jeromio]

Here's a refinement to the original diagram that probably will end up just confusing things further:

 

It's sort of similar to the idea of adding an "extra" cross member for engine mounting. And that might work since there's probably enough room under the LS1 oilpan for one.

 

To answer the question, in my non-mechanical-engineer opinion, adding another crossmember would not add the outward stress to the frame.

 

What I'm proposing is to bolster the Datsun crossmember. And it very likely won't end up looking like the cartoon I've just posted up there. Imagine the engine crossmember, bolted to the framerails, but the center of it is bent forward, until it touches the datsun crossmember. Then that joint gets welded. Then the 2 triangles created by frame rail, crossmember and "bent" engine crossmember are covered in metal plate which gets welded to the 2 crossmembers (but not the rails). Then some motor mount towers are attached to this new metal surface.

 

Something like that.

[pparaska]

Th OE crossmember is bolted to a reinforced area of the frame rail. Actually, I've seen designs that improved upon the attachment by adding a bolt (and spacer) that went through the frame rail top to bottom more inboard of the OE bolt holes. This was to stiffen the connection.

 

I think as long as you consider the local stiffness of where you add frame mounting for a cradle or crossmember "K" attachments, you'll be in good shape. A simple piece of 1"x1"x8" steel angle welded to the lower inside corner of the stock frame rail just aft of the crossmember should provide a sufficient local stiffening for any attachment. Add a gusseted tab to this inboard of the rail, and mount the K member legs or cradle to it.

[Dan Juday]

Yup, Pete's got it figured out. That's the same direction I was going in. One thing I might add, if you want to avoid any re-engineering of motor placement. Before you cut off the Datsun towers, fab up a set of JTR motor mounts and make yourself a jig, a chunk, or several chunks of metal welded together, to represent the motor block. Really only the mount area. Then add pieces that attach it with bolts or screws to the frame rails or shock towers. Then when you are ready to weld in the Camaro towers you can bolt them to your jig and locate the motor perfectly in the JTR position.

[jeromio]

Well, unfortunately, as it's an LS1, the JTR plates won't work. Which has alot to do with what got me started down this train of thought. That would be a pretty good idea though.

 

What I think I'll do is, using LoneStar's photos and the JTR book and Paul R's photos as reference. I'll see about picking up an extra datsun crossmember, and start turning it into a K member, using the actual LS1, outside of the car. Plywood firewall and 2x4 frame rails might come into play as well.

 

If it doesn't work out, then I can apply that ill-gained knowledge to the crossmember that's in the car now, and do it all the old-fashioned way (put motor in, center it, tack things in place, remove motor, repeat, etc). But, I think it will work pretty well. This won't be my first engine swap .

 

Actually, the one last bit of info that would be most helpful is the distance between the bottom of the LS1 pan and the crossmember...

[Lone Star 1]

Hey Jeromio

I think this is a great idea. I didn't have all those accessory when I started my install, and didn't realize how limiting those Datsun motor towers were going to be. Maybe even a piece of square tubing, or round pipe running all the way through the cross member and welded, then turn up directly under the LS1 motor mount. That's the type of thinking (outside the box) that it takes to do this kind of thing.

 

[ September 04, 2001: Message edited by: Lone Star 1 ]

 

[ September 04, 2001: Message edited by: Lone Star 1 ]

 

[ September 04, 2001: Message edited by: Lone Star 1 ]

[pparaska]

jeremio, I really like this idea. I guess you might still have issues with the steering shaft, but that can be worked around, I'd think.

 

If you design the bolting arrangement to the frame from your crossmember K extensions, I'd think you'd be adding some stiffness to the crossmember/rail system, probably stiffening the car in torsion. In this way, it's probably preferable to a separate, parallel crossmember for the engine.

 

Sweet!

[Guest Anonymous]

I am extremely interested in this idea however I am just not getting a mental picture of this "k" concept. Maybe if I were chatting in the forum where I could ask and recieve answers backa and forth it would help. Are we still scheduling chat times?

 

jake

AZ

[Danno74Z]

Well I was beginning to wonder if I was the only one having issues fitting the GenII -LT1 engine or the LS1 into the engine bay in the setback position. The Datsun engine mounting towers in conjunction with the setback plates make for a very challenging install because of the location of the accessories on these engines.

 

Another alternative is to use the Corvette (92-96) accessories and mounting bracket. One needs the harmonic balancer, alternator, serpentine belt, and AC compressor if you want AC. This is a direct bolt-on to the Camaro/Firebird LT1 engine and it will fit into our Z’s The new setup puts the accessories on the driver’s side of the engine and just slightly above the valve cover. I have priced this new setup out and used components run about $500 complete. W/O ac and the price drops a lot. With this new setup you can now use all the JTR plates etc. as normal. Granted this makes for a more expensive conversion, but one does not have to deal with fabbing up a new crossmember or putting unnecessary stress on the frame rails which they were not really designed to hold. It also sounds like the steering linkage becomes an issue with a new crossmember so one has to weigh that problem. Anything can be made to work with enough perspiration but I’m looking at this alternative real hard

 

Danno74Z

[jeromio]

Here's an example of a K member:

 

 

This one is custom made for swapping an LT1 into a 3rd gen RX7. Kinda nice how the strut rod mounts are integrated with it. It's unfortunate the the Z's are welded to the frame. My modded member will have to bolt to the strut rod mounts. And of course my mount towers will be attached much farther back, on the diagonal "arms" of the K, as opposed to the straight-across part.

 

Got the image from Granny's Speed Shop (hope they don't mind). They have a complete detailed write up of how to put a smallblock in an RX7 - online, for free.

 

If anyone's interested, they also have a HUGE write up of the LS1 at http://members.tripod.com/~grannys/engineschevrolet.html. It's hard to read cuz there's no paragraph breaks or anything. Just 6-7 screenfulls of detailed text. Interesting though.