Pocket

iTrader: (24)

Ive been lookin and batting around ideers and All the problems Ive heard about aftermarket K members was fitment and failure due to engine weight

So

Why not front and mid motor plates and then a modified K member eliminating any upper support from the K member

Any opinions?

xpndbl3

iTrader: (5)

haven't heard of many kmembers breaking from race use, and if you're planning a motor plate then it would be a strip only type of car. the kmembers "might" fail due to pot holes, etc on the road but some have driven over 20k miles on theirs with no issues.

V8Rumble

iTrader: (2)

I looked into using front motor plates (aka "elephant ears") when I was thinking about building a big-block powered MoPar A-body*, but really hated the idea. Mainly because in order to have enough strength to handle the 450-500 HP I was contemplating, there was no way that they wouldn't interfere with most of the work I'd have to do under the hood (and those cars seem to have a bit more room under the hood than ours do!). I can't even picture myself trying to do plug changes on a thirdgen that had headers & a motor plate - I'd probably get too frustrated & burn the d@mn thing to the ground!

If it was me, I'd do as much research on the K-members as possible, but I'd definitely lean that way. I can think of a couple of good groups that should be able to give you good, practical info - the first would be guys who road race their cars, & the 2nd would be auto-x'ers. Both stress their chassis' to a significant extent, & road racers in particular would be highly interested in weight savings, so they could probably give you the real info. (Disclaimer: I worked pit crew for 3 or 4 years on a class-winning 4thgen, so I may be a little biased! )

I don't know all of the applicable sites/forums to suggest, but I do know that this one is very good, & should be able to get you started. Good luck!

*(With those cars, the motor mounts are integral to the K-member, so you need to swap the whole thing to swap different engine families.)

Shagwell

several people on here have over 20K road miles on tube k-members.
If you search, there's a post on here about tube k-members with pics of one that's being designed for auto-cross. Much heavier duty than it's predecessors.

The problem with block plates is vibration. You really have no idea how much a motor rattles around until you drive a vehicle with block plates. Bolts rattle loose, you g/f complains about riding with you(or, depending on how shes sitting, she may just leave you to be alone with your car....... ) As xpndbl3
stated, they're basically drag only. - I'll be running block plates with my new chassis, but I'm going to use small urethane bushings around the bolts, thus giving me some flex. - Also, block plates require a lateral restraint of some type, which is yet something else to transfer vibration. You'd think the trans mount would suffice, but it's not enough.

Sonix

iTrader: (1)

can anyone point to a pic of a motor with front (or any style) of motor plates?
or what they do?

I've heard a bit about it, but i'm not totally sure how they are connected to the car, in order to stiffen up the motors mounting points. (that's the gist right?)

AlkyIROC

I only use a front plate. Although I'd love to install a mid plate, there's very little room to put one in. When using a motor plate system, you need an engine locator bar. Mine is bolted to a motor mount hole on the driver side of the engine and the other end is attached to the underside of the frame near the steering box. The locator keeps the engine from moving forward and backwards as the plates try to flex. It can break tranny mounts if it flexes too much.

I use a ProFab tubular k-member without any engine mount brackets.

Sonix

iTrader: (1)

so that big plate, right above your steering gear, is "the" motor plate? That keeps the engine from twisting around the axis of the crankshaft right?

and the engine locator bar, is below the motor, where we can't see it in those pics? That keeps the engine from going front to back?

...and you are using a profab tubular k-member, without any engine mount brackets.... so, no typical engine mounts, in the clamshells, below the block?
what constrains the motor side to side?

xpndbl3

iTrader: (5)

the plate stops the motor from twisting side to side and the locator on the block stops front to back movement

Sonix

iTrader: (1)

ok, so if a person added a motor plate, it's to help stop the motor from twisting? assuming all else is "stock" under hood?

You still need your motor mounts and whatnot to keep the motor from going up/down right?

AlkyIROC

Front motor plates rigidly mount the engine to the frame. It can't rotate, it can't move side to side, it can't move up and down. Because of how metal can flex, it "can" move forward and backward.

Front motor plates eliminate the clamshell engine mounts. An engine with a lot of torque and using the mounts on the side of the block can actually distort the cylinder behind the mounts. Even my engine isn't at that level yet.

If you don't want to use front motor plates, the next best thing is to install solid motor mounts. This keeps the engine rigid.

My front motor plates you can see in the pictures are 1/4" thick aluminum. They're bolted to some brackets that I welded to the frame with a 1/2" grade 8 bolt on either side. The plates fit behind the water pump so the water pump bolts and the 2 lower front (old style motor mount holes) secure the plate to the engine. Because the plate isn't very rigid going forward and backward, an engine locator bar is used which you can't see in the pictures. It's a 1/2" or 3/4" steel tube with some rod ends on either end. Some cars use 2 of them, one on either side of the engine. I only use one. It's only job is to keep the engine from moving forward and backward.

The motor plates attach the engine to the "frame" and not to the k-member (suspension). If the engine produces enough torque, it can twist the frame but my chassis is set up well enough that both front wheels come off the ground the same distance with very little twist.

A rear motor plate is normally recommended for support. It's only a thin piece of steel plate. Usually about .090" thick. It's main purpose is to hold up the back of the engine. Right now the rear of my engine is supported by the tranny mount. If I ever break the tailshaft of my tranny or blow up the tranny from something exploding inside the tranny, the back of the engine will drop down. A poorman's fix is to run a cable under the bellhousing (chains not permitted)