I'm dropping a 3800 motor into my Isuzu pickup and had questions for those who are familiar with the stock 3800 mounting configuration.

I have to mount the engine much higher than in a stock setting for clearance issues (this is for a 4x4 offroading truck application).

I am using the stock Camaro mounts.

I would like to keep the motor mounts close to the engine to keep the torque on them as low as possible, so I brainstormed an inverted mouting configuration. This pic shows a backing plate of 1/4" steel and the lower hole will pass through a frame sleeve of sch40 pipe welded in the frame.

Before I go any further, I may have already made a mistake in assumoing these motor mounts can operate at this angle, any comments?

http://berisford.net/uploads/cpom/projectpup/9/5.jpg

here is my progress so far.

http://berisford.net/uploads/cpom/projectpup/9/6.jpg

http://berisford.net/uploads/cpom/projectpup/9/7.jpg

http://berisford.net/uploads/cpom/projectpup/9/8.jpg

The metal you see here is all 1/4". The plan is to add third load-carrying piece in the middle of 3/8" steel. The gussets in the middle would be 1/4". The triangular gussets on teh backing plate would be 3/8" steel.

http://berisford.net/uploads/cpom/projectpup/9/9.jpg

This engine is a stock '02 3800 (estimated 200 peak ft/lbs).

Any comments?

 

That's a damn good job so far.
The only thing I can see is the 90* leverage the plates on the block will see,especially on the driver's side.
If the base for the mount had been more "under" the engine the plates would not have seen as much shear and would have more of a straight pull up on them.

Hope it makes sense to you.

 

Thoughts:

The closer the mounts are to the engine the MORE torque load they take. Farther apart is like a longer torque arm. There is less load on the mounts the farther apart they are.

You are using the mounts at a bad angle. The weight of the engine, which is the main load on the mounts, should be pointed at the base of the mount about 90 degrees from your design. You are going to have metal-to-metal contact in the mounts quickly, I believe. You won't like it.

Your frame attachment is going to try to twist the frame rather than load it in compression thru its vertical dimension. That's not too good.

You are using the bolts to carry most of the loads. They should be used more to attach the parts. Some of them are mostly in shear, which isn't good.

Suggestion:

Build a U-shaped "cradle" from rectangular tubing with a wider open top which passes under the engine in the area of the mounts, if that's possible, and wraps over the top of the frame rails. I would look like the horns of a Longhorn steer. Attach the engine mounts to the top of the frame rails and hang the cradle in double shear (both vertical walls of the tubing) from the bolt thru the engine mount. That would be the tips of the horns.

If necessary for clearance the portion of the cradle under the engine could be plate rather than tubing. If you were using 1/8 wall tubing about 3 inches wide, 1/4 x 3 or even 3/16 x 3 should be good, especially since it will be bent.

I applaud your desire to fab this yourself. I also applaud your willingness to ask for comments. No offense intended in my critique of your design, BTW.

Good luck.

 

yea, all that stuff is in pure sheer, although as big as you are making everything, it will probably hold.

 

will this config solve my problems?

http://berisford.net/uploads/cpom/pr...motormount.jpg


Any advice for beefing up the engine bracket? Others have suggeste dit needs more beef.

RE: comments about the 90* angle the engine brackets will experience, I am copying the stock engine bracket design, and just making them a bit shorter. I believe as long as I make the engine bracket as strong or stronger, I don't think I will have a problem. As to how to make them stronger, not sure yet...

No offense taken , this board seems much more civilized than the other's I post on anyway. criticism welcome

 

The stock bracket is that far away from the engine and running 90* to the engine and what looks like 8-10" away? Its the distance away that matters. Never seen an American car like that. Don't mean there isn't some.

 

Better!

Forget the 3/8 thick stuff. You're not building a locomotive here.
You can "beef it up" by making it lighter. Put the metal where it needs to be.

Make those 3 x 3/8 gussets 2 x 1/4 max thick BUT run them to the bottom of the frame rail and put them at the outer ends of the plate.

As for the "bracket 1/4 and 3/8 steel", again forget the 3/8. Make the bracket go from the top to the bottom of the engine mount (1/4 MAX thick) plate. Taper it to about 1-1/4 high at the Camaro mount and radius it around the Carmaro mount thru bolt. Box the bottom of that bracket with 1/8 MAX strip up to the 1/4 frame plate and the full top all the way past the engine mount bolt. Wrap it around the radius if you can. 1/8 is overkill.

Cut the "1/4 plate" off at the end of the Camaro mount. Any metal beyond that point is useless. It only needs to be as wide as the Camaro engine mount.

I think you ought to use grade 5 bolts instead of Gr 8. They are strong enough and a little more ductile. Gr 8 are very strong but more brittle. You might consider a 7/16 for the long one thru the frame. Drill a clearance hole for the spacer on the top of the frame rail and just a clearance hole for the bolt on the bottom of the frame. Have the spacer (1/2 Sch 40 pipe) protude a little thru the top and Mig weld all around it.

Think like a "load" or force. Imagine how the weight of the engine gets into the frame rails. Where there are big loads you need to have more vertical section, Once you get about one bolt diameter past the bolt thru the Camaro mount, any extra metal is a waste. The farther you are from the attaching point on the engine, the shorter (vertical) the mount can be. IOW, it can be a triangle in the front view you show, because that's how the loads are. I wish I could explain moment diagrams in words.

The top and bottom boxing plates are in tension and compression not shear. This is good. They keep the side plates from buckling better than making the side plates thick.

I hesitate to suggest this, but your 1/4 thick stuff could be replaced with 3/16 if you did it right. You might need a (.083 thick) doubler in certain areas, but that would be the elegant solution. I wish I knew how to post sketches.

 

LR: The stock camaro mount when bolted up puts the through-bolt point on the top of the frame rail--It's 7"-9" long.


OLD: Here's the new plan based on your advice and some simplification. I have been overlooking the easiest idea because of how long the stock motor brackets were I just assumed they had to be long.

http://berisford.net/uploads/cpom/pr...otormount2.jpg

Hopefully I can contribute some stuff to this forum you guys have been a big help. I'll be running this 02 3800 engine via a DIY fuel injection and spark controller called megasquirt which some may have heard of and some pics and info on my experience some might find helpful.

 

Good job! I had a thought (or maybe a dream) about the mount last night. Extend the plate that the mount attaches to across the top of the frame rail instead of just attaching it to the corner.

Good luck.

 

That looks a 100% better and I don't think it will break as easy like that.
Come on in and let us know what ya think sometime.

 

http://www.berisford.net/uploads/cpo...ctpup/11/1.jpg
http://www.berisford.net/uploads/cpo...tpup/12/12.jpg
http://www.berisford.net/uploads/cpo...tpup/12/13.jpg
http://www.berisford.net/uploads/cpo...tpup/12/14.jpg
http://www.berisford.net/uploads/cpo...tpup/12/15.jpg
http://www.berisford.net/uploads/cpo...tpup/13/13.jpg

 

Looks good!