My reduction drive was made by Dave Johnson
Canada. It is a belt drive with a 2.1:1 ratio. It is pretty
heavy at 52lbs. I elected to use this one for a few reasons:
- It is made in Canada
- I know at least three people using Dave's redrive with good
success. One of them has been using it for more than 6 years.
- Dave produced over 400 of these redrives. The model he now
sells is the fourth generation of his product that evolved over more
than a decade.
- A belted redrive allows me to simplify the engine installation by
keeping the mostly stock intake manifold and by using a carburetor on
top of that manifold.
- Dave provides a lot of support, not only for his products but he
spends a lot of time helping builders to rebuild and convert their
- His redrive is among the cheapest ones on the market.
being what it is, errors or issues are to be expected. And there
were some issues with mine that needed to be addressed. Initially, I
was not able to fit the reduction drive on my engine because the dowel
pins would not align with my engine bloc. I presume that the assembly might have moved
during the milling process. While I was proposed a fix I could apply
locally, I preferred to have a unit that I could easily re-install on a
different engine bloc if I ever need to do so.
Reductions replaced the unit without any hesitation.
I sent my re-drive back to him by bus and a totally new one came about a
month later. This one fitted much better (all holes aligned perfectly),
but it still had a few minor issues. On the following
pictures, we see the new re-drive (w/o the lower front bearing) installed
on my dummy engine to see how it fits.
of the few minor issues is that the material around the lower left bolt
has not been milled to a flat surface to allow the bolt head to sit.
I brought it to someone I know who has a milling machine and he quickly
The assembly of the re-drive is pretty straight forward
and the process is very well explained in Dave's instruction manual.
The first step is to mount the main assembly to the engine.
Once all bolts (except the lower right bolt which attach the starter
mounting plate) and the engine dowel pins are set, the bolts are torqued and safety tied.
oil seal holder on my unit is still off-center a little bit (.006"), but the seal appears to
fit well. If it ever causes a problem (like premature oil leaks), I
will re-center the seal holder with a centering ring that Dave provided to
me and fix it in place with dowel
I discussed this point with Dave and he was very surprised
since his matching process is very exact. However, upon reflecting
on this, he believes that he may not leave enough play for the assembly
bolts whose holes are drilled to tight tolerances (on a standard Subaru
bell housing, these holes are drilled much larger than they need to
be). The precision fit is to be assured by the dowel pins. I
would bet that future units won't present this problem at all.
leaves me with an additional thought... as my mentor says, I spend too
much time measuring and not enough progressing...
My own "OUPS!"
When I tried to torque the lower right
bolt to 19ft-lb, the aluminum spacer for the starter support crushed!
:( That spacer is made from a 5/8" machined
aluminum rod. The wall of the thin portion (which has a outer
diameter of .450")
is only .049" thick. While I was explained the proper torquing
procedure and was offered a replacement part, I decided to go ahead an make a new spacer
from a steel rod. Then, I remembered that I had an old
underwater scooter shaft laying in a box in my storage room. That
1/2" shaft is made of Stainless Steel and is a perfect material for
the purpose. This was the first time I used a lathe and it
really makes me appreciate the amount of effort spent in making those
of the few minor issues was that the holes in the lower front bearing
support were not drilled and tapped as per the instruction manual.
The manual mentions that the holes are pre-drilled to 3/16" and we
need to match drill the front plate with these holes, then tap the front
plate to 1/4 NC and final drill the front bearing support to
1/4". On my support, the holes were drilled to 17/64".
Unfortunately, on that day, Dave was un-reachable, so I followed
the advises of a local expert. I installed the front bearing drilling
and tapping the holes in the front plate to 1/4 NC. Then, I drilled two holes in the bearing
support to 5/32" using my press drill. I matched drilled the
plate and enlarged the holes to 3/16". I inserted two
3/16" by 1-1/4" dowel pins. These pins now ensure proper
alignment of the bearing assembly.
I spoke with Dave, later, he approved my installation procedure but he
also mentioned it might not have been necessary as this was a result of a
change in design. The new bearing support is better designed to ease
the removal and replacement of the bearing assembly.
the end, the re-drive appears to be a nice unit. I look forward to see it
running. I know several people using it for years with great
success. They are all happy with theirs.