MOTOR MOUNTS

[BOZO]

I am putting an L20b from a 1978 620 into a 1974 620. I noticed the rubber part of the mounts are different. The 1974 being just a square rubber biscuit and the 1978 being an interlocking rubber mount which is a bit taller than the other. The steel motor brackets SEEM to be the same. My question is which motor mount should I use?

[DanielC]

i have heard that when putting a L-20-B in a 521, use the L-16 motor mounts.  I would try the 1974 rubber motor mounts, with the 1974 steel brackets.

[datzenmike]

Try both but probably use the L20B rubber isolators. The L20B is 2 cm or 3/4" taller than the L16/18 so maybe this is the difference.

[BOZO]

Thank you both for your replies. I will clean up and paint both sets of brackets and have them both ready when it comes time to stab the motor in. Gonna try it first with the L18 mount and bracket.

[distributorguy]

I think you'll find a slight difference in the steel portion of the brackets as well.  I have an L16, 2 L20's, and an L20 from a 720 here.  All of them had a different setup for motor mounts.   :confused:

[BOZO]

Well, dropped my L20b into my 1974 620 this last weekend. My thinking was to use the 1974 L18 motor mounts and rubber isolators.I know L20b's are taller but I figured the block width dimensions were the same. Upon setting the the motor brackets side by side, the L20b brackets look the same but are a lower profile. After much cussing and prying, I ended up using the L20b motor brackets with the L18 isolators. This is just speculation but I think the L20b block may be a bit wider in cross section than the L18. I have some good comparison photos of the motor mount brackets that I would show but my Android pad does not seem to offer up attachments.

[banzai510(hainz)]

use the 74

[BOZO]

The 74 motor brackets would not fit, but using the 1978 L20b motor brackets and the 1974 isolators it dropped right in. Also makes my motor sit low.

[racerx]

Can u go on AutoZone and cross reference the motor mounts and also see the measurements.

[Moist Lightning]

Try both but probably use the L20B rubber isolators. The L20B is 2 cm or 3/4" taller than the L16/18 so maybe this is the difference.

Does this mean I don't have to modify my KA24de brackets? As they are usually dropped 3/4" and put on l20b rubber mounts.  

 

Edit: I have l16 mounts

[BOZO]

I wish I had measured across the bolt holes on my 74 kingpin frame and compared it to the 78 ballpoint frame to see if there is a difference while I had the motor out of the 74. But hindsight is 20/20. If there is a difference it might help to solve future problems juggling motor mounts. I also wish I had checked to see if there was a width difference between the L18 and L20b, but I was just busy trying to get my truck back on the road.

[Moist Lightning]

Found some l20b mount is my parts bin. 

 

l20b mounts: Roughly 1.9"

L16 mounts: Roughly 1.5"

 

Edit: these are height measurements. 

Edit 2: turns out the mounts i had arnt l16 mounts as i just ordered some off rockauto. They ended up being the same height as the l20b mounts. Im thinking they might have been 520 mounts. Next time I order parts ill get some 520 mounts and measure them, unless someone else has some lying around they can measure?

Edited September 17, 2020 by Moist Lightning
Correcting Info