solid motor mounts?

well i wrecked my xj and bought it back, so i figure i can try all that frankenstein stuff and see what works best before doing it on my replacement xj.
when i was messing around with speed on small cars i made some big round washers and put them on either side of the rubber bushing on the motor mounts and welded them in place, therefore making solid mounts. this does alot for torque. it was a front wheel drive though.
would that be a bad idea for something like a jeep or any 4wd for that matter?

Id say it could be a disaster, the 4.0 is plenty powerfull to shear the bolts on the mount to begin with let alone take away all its give and I bet they pop PDQ not to mention all the bad vibrations your gona get.

eh...just a thought.

you need HD poly mounts if you want to go that route.

brown dog
MORE

lots of folks make them.

Solid engine mounts can be done (I've installed metal engine mounts on bracket racers before,) but they're not without their problems...

You'll need to bush the mount through bolt to make sure it's SOLID in the bore. Leaving it loose will damn sure shear the bolt sooner or later. The effect of the small bushing is nominal, but it's important to reduce the momentary shear load when you stick your foot in it (leaving clearance for the bolt will just give it one Hell of a beating...)

You'll probably need to reinforce the frame sill significantly. Since the XJ isn't "framed" with a heavy mounting point, you're likely to pull the screws out in rather short order. You probably don't want to do that...

The use of SAE Grade 8 bolts is not indicated - their failure under shear is rather more dramatic. Designing from scratch, I'd use two or three SAE Grade 5 screws in place of one SAE Grade 8, and I'd do a few other things as well (which I lack the means to explain easily at the moment - it's just a picture in my mind anyhow.) Multple screws have a directly relationship to increases in shear load tolerance. I would probably redesign the engine bracket and the frame sill bracket for a "face" interface tho - making it easier to use three or four screws instead of just one... I may have to start designing this after all...

Likewise any ISO screw with a property class of 10.9 or higher. "Strong" also means "brittle" - where a Grade 5/8.8 screw would bend a little, a Grade 8/12.9 screw will more likely shatter. Not pretty.

In short, it can be done, but there are a number of pitfalls to look out for. If you don't feel like engineering the thing, and you don't want to pay someone else to do it, you're really better off getting polyurethane-bushed engine mounts. It's a sort of compromise - and it's already designed for you. The torque loads and shear loads involved would make this a little more complex of a problem than what you had to solve on "Sport Compacts..."

Dont solid mount the motor. You are asking for trouble as people have pointed out above. Shell out the $100 or so for the MORE bomb proof motor mounts. I have had my MORE mounts for 6 years or so now and have NEVER had an issue with them and the are still holding up strong even with a very healthy stroker motor

AARON

new stock ones are 30 a piece from autozone with lifetime warranty.

I had poly ones from rustys on my MJ, and I loved them. More torque, quicker response, more noise in the cab. I didn't mind, but the ladies didn't love it. It helped stiffen up the steering noticablly.

mjma said:

It helped stiffen up the steering noticablly.

Click to expand...

nice