How do you decide motor placement??

Specifically the height. I have a '42 MB with a 4.3L V6 : My new plasma cutter showed up Saturday, I got the frame rails boxed in and everything welded up and reinforced. I am using the Advance Adapter engine mounts. Currently the mounts are clamped to the frame rails. I want to make certain the location before I weld the mounts in.

As far as left and right, I am letting the transmission decide the placement. My jeep had a Chevy 153 4cyl bolted to a SM420, adapted to the Spicer 18. Seeing that I was going from 1 GM engine to another, and the bellhousing bolted right up, it makes sense to follow the "If it aint broke, dont fix it" rule, at least to me. This also allows me to avoid building new driveshafts.

Front to rear, there is ample room for the radiator/fan. I can remove the distributor cap, but the distributor itself might be cutting it close.

My main unknown is the height of the motor. Obviously, I want it low enough for the hood to clear. Rather than guess, I bolted the hood, fenders and grill on and checked. I have about 1/4" clearance from the top of the air intake assembly to the bottom of the center seam in my hood. (hangs about 1/2" below the underside of the hood.)

Is that 1/4" enough? I can physically lower the motor. The jeep is equipped with Rancho 2.5" lift springs. I put a jack under the front pumpkin and lifted the jeep completely off the ground with it, there was still 3-4 inches clearance between the top of the diff and the oil pan, and the front drive shaft wasn't any where near the starter. Currently, The crankshaft pulley is about centered up and down on the front stock crossmember.

I am done working tonight, but would like to have the mounts welded in by tomorrow evening. Any suggestions / advice would be appreciated.

 

the top 1/4" factor is your limit ,,,maybe look at having to shift motor to the side to work the steering shaft passed the exhaust manifold ?
if the 1/4 works I wouldn't lower it...edit :if you do lower it then with a lot of flex you have to deal with where the frt driveline would fit in...edit :also the motor will torque twist some so that needs to be taken into account

 

go as high as you can without hitting the hood, but realize this may interfere with the transmission hitting the tub. You may go high, then need to modify the body. The transmission and transfer case side to side is easy to relocate. Ignore your driveshafts. put the engine/transmission assembly where you want it and if they work, great, if not they are relatively inexpensive to have made or make your own,

 

Is there another way to determine what my max flex would be? Other than putting a jack under the axle on the passenger side and lifting until both tires leave the garage floor? Because if that is it, there isnt a lot of flex on my front end. Doing that I still had ample front drive line clearance.

 

Intake assembly hits the hood long before the transmission hits the tub (1" body lift). Side to side (a matter of 1 to 1.25") shouldnt change my driveshafts would it? Because an additional nudge to the passenger side would make routing the steering a little easier. It had a manual saginaw conversion before, but I am adding power steering during this project.

 

if your transfer case is in the same position there may be no need to modify driveshafts, but driveshaft dictating the placement of the engine is not the best idea. Typically the front driveshaft slip yoke is pretty worn out anyway. You can shorten one yourself easy and have a longer one made fairly inexpensively. I would not let the driveshafts dictate your build.

 

well my front driveline polished and wore a spot on the starter and on the bell on my dauntless with a texas d300 ,,,, a tiny change in angle could make for a no interference fit ..... I brought mine to fallbrook tire and shaun and I used the fork lift to check everything

 

Motor height is all about what your plans are to use the Jeep for: Higher motor will raise your center of gravity......also by raising the motor drive shaft angles both front and rear come into play. A normal engine install would have the motor higher in the front than back.......3-5 degrees is a pretty normal slope. If your looking for more ground clearance at the skid pan or break over angle then a higher motor mounting location might be warranted. Otherwise lower is safer.

There is a sweet spot........have the motor and transmission hanging in there together and mount it where it best fits for : Clearance, drive shaft angles, oil pan clearance, hood clearance, skid plate, firewall , valve covers, inside floor pans., radiator ..............ETC .
No one size fits all...............plan ahead as to where the battery or other under hood accessories you want may have to go........I would just tack it in place and let your build develop around it some and if you find you have to make an adjustment later, it's much easier to do so by removing a few tack welds.............

 

As in, lift it by one tire? The tire shop is about 500 yards from my house...

 

i used his forklift
more control ....do it against his bank so it cant fall over

 

One way to check for clearance is to measure from the bottom of your bumpstop to the top of the axle where it will hit. This is the maximum (plus a little squish of the bumpstop pad) that the axle can move up. Armed with this measurement you can check clearance all along your axle housing and pumpkin without lifting and twisting the axle. I like to allow for an extra inch to insure clearance and keep in mind that the axle is not going to move straight up and down. It is going to swing toward where ever your shackles are... normally forward unless you've reversed them. So keep this movement in mind. This takes time and some imagination but I've used this method on several vehicles and never had a clearance problem. And it saves me from having to find a forklift to borrow

Regarding engine placement, it is always a compromise and as Tarry said alot depends on what your personal goals are. I personally prefer to keep the engine as low as I can set it to keep the center of gravity nice and low. I also like to set them as far aft as practical as well, again to even out the weight between the front and rear axle. But it is always a compromise

 

Consider the added weight of a winch, if you'll be using one, and the fact that those new springs will settle or sag somewhat over time. Not a huge deal but, if you're cutting it close in the build stage, you could end up with a rub a few years down the road that wasn't there when you built the rig.

I'm with terry in placing the engine as low as you can without interference elsewhere. Best way to go IMO.

I have seen guys cut that seam/ridge on the underside of the hood to make clearance for the air cleaner. Not that I endorse hacking up a good original hood. Just a thought.

 

Thought about it, then reinforcing around it. But I'd like to keep the hood original if I can, same reason I dont want to cut up my fenderwells for the exhaust. Gonna take all these suggestions, go back out today. Measure 300 times, weld once.

 

Well I got everything in and set up. A friend had a set of Sanderson full length coated headers I was able to acquire on trade. I have 1/4" clearance between the air filter assembly and hood seam, 6.5" between the water pump pulley center bolt and the grill (Not sure whether I want an electric or mechanical fan yet, but should have room for either), Header is tight but will make it around the stock master cylinder and clutch linkage, Steering shaft sits above the new engine mount by 1/4", and there is a solid 3/16" clearance between the steering shaft and the driver's side header. Hey, an inch is as good as a mile, right?

Using the measurement to bump stop method suggested by Fly Navy I have at least 1.5" of clearance between the axle and any point of contact. Welded up the mounts to the frame. Feeling pretty good about my progress this week.

 

Celebrating my accomplishment with some Knob Creek...

 

nice!

 

Looks like you have more clearance then I have for the steering shaft. Should work. By the way What year is your motor?

 

Its a 2000. Vin code W out of an S-10