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setback plates


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i've been working on a file for my setback plates to send to the laser cutters and was wondering what you think.

 

normal_setback%20plates.jpg

 

i was thinking of then welding on pieces of 1" bar stock as spacers, then drilling them out. with this setup i think i can drop some decent weight from the plates compared to the JTR ones. i was wondering if i could remove some of the middle of the plates, in a triangular pattern, to further reduce the weight or whether that would weaken the plates too much?

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I really wouldn't bother with this design over the original. Carbon steel weighs 0.277lbs/in^3. Just eyeballing this design you would be saving about 1.5lbs. Also I feel the strength of the plates would suffer. If your interested in saving weight you should go with the alum spacers from JTR. They will be a lot lighter than sqare tubing.

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Guest JAMIE T

Your plates look great. I can't beleive folks who talk about the strength suffering when lightening the mounts and plates. Look at what they bolt to!!! Flimsy stock datsun frame stand-offs. Any mount made of 5/16" plate is going to stronger than the stock datsun crap. I'm making mine out of aluminum anyway. Properly constructed spacer/setback plates will be plenty strong in aluminum. Properly gusseted parts will be strong as they'll ever need to be.

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Muskrat,

yes, they are for the standard sbc. i just reshaped the JTR ones so they wouldn't look mismatched to the chevy motor mounts.

the reason i'm looking at welding 1" round bar stock on for the spacers is because,

1) i don't think there will be much difference in weight between those and the aluminum spacers and any difference will be made up by what i removed from the origional plates.

2) i would rather have 1 piece of metal that looks like it belongs there than have a motor mount bolted to a slab of steel which is used to sandwich a piece of aluminum to the engine block.

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Muskrat' date='

yes, they are for the standard sbc. i just reshaped the JTR ones so they wouldn't look mismatched to the chevy motor mounts.

the reason i'm looking at welding 1" round bar stock on for the spacers is because,

1) i don't think there will be much difference in weight between those and the aluminum spacers and any difference will be made up by what i removed from the origional plates.

2) i would rather have 1 piece of metal that looks like it belongs there than have a motor mount bolted to a slab of steel which is used to sandwich a piece of aluminum to the engine block.[/quote']

 

Hey thats fine. I do think the shape looks better than the JTR design. They will not be as strong but as Jamie pointed out they still will not be the weak link in the setup. As for the square tubing I think the JTR book mentioned that some people have used square tubing. You would have to find the two different sizes and all but that shouldn't be that hard. I personally think the JTR spacers look really good. Keep in mind now that the spacers in the JTR drawings are different than the spacers that you buy from JTR. The ones you actually buy are T shaped and would complement the look you have with the mounts.

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i'm not using square tubing anywhere. instead of using the aluminum spacer, i'm going to use 3 pieces of 1" round steel stock with the center drilled out which will be tig welded to the setback plates.

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instead of using the aluminum spacer, i'm going to use 3 pieces of 1" round steel stock with the center drilled out which will be tig welded to the setback plates.

 

I'm using something similar. It's a thick-walled steed tubing I found a local scrap yard. It measures approx .850 OD and .450 ID (.200 wall thickness) I simply band sawed 3 for each side and slid them over the bolts as I mount the set-back plates to the block. No need to weld them to the plates since they can't go anywhere once bolted into place. Been set-up that way for several years now.

 

BTW, I modified the design of the set-back plates to give me another 1/2" of nominal set-back. I did this because I am using a small diameter (Late model, computer controlled HEI) distibutor, which is the limiting factor for set-back distance. 1/2" isn't much, but it was easy to do, so why not :-)

 

Paul

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PaulR, your're using an automatic tranny though right? i will be using the T56 so i think if i were to move the engine back any more i might compromise the placement of the shifter in the car. otherwise i could move the engine back another inch at least because the LT1 has the front mount distributor.

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