1st gen dakota motor mounts don’t line up to BB spools

Howdy

I dropped my 512 into my 1954 C series pickup on a 1989 dakota frame today and learned something I’d like to share with the whole class

The dakota 3.9 v6 that I pulled out of this std cab rwd longbed had spool mounts- they looked very similar to the ones in my 1973 swinger. My 400 block has the late model big block spool engine brackets. From what I’ve read the 1st gen 87-96 daks the motor mounts are the same for 3.9 v6 and 318 or 5.2, but different from the 4cyl mounts. Makes sense right? Since the 3.9 is basically a 318 with #7 & #8 cyls chopped off.

I’ve also read that the late big block K members in muscle cars you could swap small block LA to B or RB 361-440 because the mounts are in the same place. 3.9=318. 318=440. So maybe 440=3.9? No such luck. Maybe the next guy will turn up this thread in a search because I didn’t find anything past the now discontinued schumacher swap kit parts.

So I figured I would probably have to move the mounts for rad clearance or proper driveline offset to match my ‘custom’ rear axle, but it turns out that the dak mounts weren’t even close to fitting on the big block. With the passenger side installed the driver’s side was way up by the oil pump body. The passenger side is too far off center- even farther than a standard driveline offset.

Luckily the frame side mounts unbolt from the crossmember leaving a decently clean canvas to work with and the motor side spools will be easy to connect being just one big longitudinal bolt per side. Fabrication time!

In other news for all the people rushing to duplicate my easy quick little weekend project the rear sump melling 8 qt pan fits nicley behind the crossmember and a deep cast trans pan fits just in front of the stock trans x-member.

I have the motor just sitting in the chassis now with a huge hole cut in the firewall. It’ll probably sit there for a while before I crib it up and make new mounts.

Problem is, that the later K members are different not the same. It's the early ones that are the same. You got it backwards.

73 and up is the cutoff

http://www.moparts.org/Tech/Archive/motor/42.html

There is great info there! It’s hard to read online I’ll print it out at work today.

You’re saying the 73 up spool mount Kmembers don’t swap LA to B/RB but the earlier biscuit k members do? My 73 /6 I got a conversion kit to drop a 318 in there.

I'm not saying anything that generic. For B bodies, that generally applies, but I am not a B body guy. For A bodies it does not apply. For C bodies, well the early ones didn't come with an LA option so who knows.

The linked info details most of it.

Makes sense. I don’t understand why the 73+ spool mounts aren’t a popular retrofit. I guess all the cool cars were 68-73 or earlier. My 408 1972 demon would rip a biscuit mount in half every six months or so before I got fancy through bolted ones. That was only 400tq at the wheels.

The replacement poly bushings I got for the late 70s 400 spool mounts should hold up pretty well and they will definitely make fabrication easier for the frame side mounting brackets. Still haven’t decided if I’m going to go with a weld on or bolt on solution- welding would be easier but dropping a motor in is easier if you don’t have to come up over the mounts and my hood fenders grille and rad support come off in 1 piece with 4 bolts.

Since this is the street rod section, most of the info here probably applies more towards the guys building the pre 60s stuff, not whatever applied for the 60s and newer stuff.

For what its worth, my 39 Dodge pickup that is on a 91 Dakota frame has the spool motor mounts on its 5.9 Magnum (360). The biggest difference is that the motor sits back 6" from the original motor location on the frame. I did not (nor do I ever) expect anything the Mopar factory ever offered to "fit" perfectly for my application, but it was nice to be able to modify some parts off Mopar vehicles to make the process work more easily. I try hard to keep the brackets that bolt to the motor unmolested.

I have built a few street/hot rods (more then a dozen), and in every instance, the desired motor and trans were hung in the engine bay on the cherry picker with the trans supported with a floor jack. They were positioned where they needed to be (sometimes there is very little clearance, the motor/trans has to sit in an exact position) and then brackets were built to hold the motor/trans in that exact position. I find its often easier to locate the trans mount before building the motor mounts. The option of being able to use a factory engine bracket and part of its existing chassis bracket to locate a motor/trans is a nice advantage.

Sometimes the biscuit motor mount is the best option because it will fit in places the spool mount doesn't fit. When I use the biscuit mount, I usually cut off the stud and drill a 3/8" hole through both steel brackets and the rubber and insert a 3/8" bolt with a lock nut. That still allows motor movement without the concern of easily breaking the rubber mount that sure seems to be a lot weaker these days then they used to be. Gene

Thanks for the response Gene!

That makes sense on the year thing except my ‘54 230 flatty mounted with the opposite triangle than modern motors- one in the front two beside the bell.

Like you said the shallow front section of my rear sump pan will have to be maybe 1/2” (or less?!) above the motor crossmember and even then I might lose the under dash guts for my fresh air door to make room for an air cleaner. Cyls 7&8 are basically under my dash. I think the C-series would look terrible with a scoop or molested hood. With the motor sitting up and crooked right now it looks like it will have to come down just to make room for a naked carb with no air cleaner! Side to side is of course also a deal where there is only one place it can go- straight and perpendicular to the pinion.

I am definitely looking at using parts of the stock female flanges off the dakota frame. Being able to drop the motor into the slots and retain it with the washers locked under the top flanges is a huge advantage over trying to line up three holes exactly and I suspect this mill will be in and out a few times before it gets plumbed and fired.

I also agree on the driveshaft/trans mount getting done first. Lining up the tail perpendicular with the pinion will be easier from the back and the single point mounting will allow a tiny bit of fine tuning up front before finalizing the triangulation with front mounts.

I want to cut off the tops and bottoms of the female mounts and re-connect them with 3/16” plate so that the mounts would still be a bolt-in deal on the xmember. I might burn them in anyway but at least that way they could be located in a way where after I tack them up I can just pull them to finish welding instead of pulling the motor to access them. I’ll find out when I make them- sometimes the cardboard and metal have their own ideas. In any case they will be super strong I’m going overboard on strength on everything for this big block.

Rdr

I think Dodge trucks used the front motor mount and the 2 on the side at the bell into the early 60s. Usually you ended up cutting the two side brackets off the original frame if you went with a modern motor mounting system.

I installed a small block Mopar in a 54 Dodge pickup, on that one I used an F,M, & J (Aspen/Volari) clip. Even with that, the small block protruded into the cab the full width of the motor & exhaust manifolds and was 6" deep. The "new" firewall was about even with the bottom of the dash. The motor sat low enough there was plenty of clearance to the hood. Unless your truck body is deeply channeled over the frame, I think you will have enough clearance for an air cleaner assembly. The air cleaner assembly should sit forward of the dash. There still should be enough clearance for the fresh air vent on the cowl as well, but you may need to do some careful firewall notch design.

I did a 50 Dodge truck, and that motor also protruded into the cab, and my 39 on the Dakota frame also protrudes into the cab. I think its because Dodge set the original motors in the original trucks centered above the front axle, and the modern motors are longer then the original flathead 6s were and are designed to sit farther back. My 54 was an original V8 truck, so who knows. It was lacking its original motor when I got the truck. Gene