qd-20 conversion to fuel pump

[amuller]

I have a 1959 Johnson 10 hp (QD-20) that I want to convert from pressure tank to pump. The original-looking way to do this is with a bypass cover with a pump mount. The number is 305751 or (?) 308396. Anybody have one of these lying around?

[Steve D]

If no one comes through with an original you can make an adapter plate similar to the one in the 1st picture (I believe courtesy of Frank R. back in the day).

Also someone on ebay is selling fabricated ones. I recently bought one, haven’t tried it yet but looks to be able to do the job just fine. https://rb.gy/zpeaem

[Steve D]

My 1st reply went poof, maybe because I included a link?? Very frustrating.

Anyway amuller, if no one comes up with an original you could make an adapter plate similar to the one in the 1st picture (courtesy of Frank R. I believe back in the day before he retired from making stuff).

Some guy on ebay is also selling a fabricated version that I recently bought but haven’t tried yet. But it seems to be able to do the job just fine. I won’t include the link this time, just the screenshot of the page and if you want it you’ll have to search for the item manually.

For anyone reading this he also makes them for the 7-1/2 HP making it much easier to convert those to a fuel pump, rather than having to go in behind the manifold and mess with that.

I personally like the pressure system but I have converted a couple for myself and converted for others too.

[Steve D]

Also for what it’s worth, my personal preference is to use the top cylinder for mounting because what I’ve experienced is it gives you a little more clearance for the hoses angled down and more flexibility with the type of fuel pump to use because of their individual design. If that matters to you, if you can get an original, that would be the 305751 version.

[frankr]

That milled version is very interesting. Does he say to mount it on top of the bypass cover, or in place of the bypass cover? If without the bypass cover, you won’t have the deflector. Will that harm performance? Very interesting.

I can still make one of my adapters, if somebody sweet-talks me enough.

[Steve D]

Good question Frank, didn’t think of that. He says in place of…not sure if or how that would effect performance. If I have a chance to mount it on one of my motors and try it out before the end of the season I’ll post back.

[need2fish]

My understanding is that the deflector is to make sure as much of the the incoming charge as possible is not directed into the the “top” of the cylinder where it will get ejected out the exhaust side before combustion starts . I’m probably not stating the intent coherantly, but it’s all about making combusion as efficient and as powerful as possible. Loop-charging takes it one step further.

[fleetwin]

frankr wrote:

That milled version is very interesting. Does he say to mount it on top of the bypass cover, or in place of the bypass cover? If without the bypass cover, you won’t have the deflector. Will that harm performance? Very interesting.

I can still make one of my adapters, if somebody sweet-talks me enough.

I was thinking the same thing….

[seakaye12]

frankr wrote:

305751

What do they look like; Frank?

[Steve D]

Steve D wrote:

Good question Frank, didn’t think of that. He says in place of…not sure if or how that would effect performance. If I have a chance to mount it on one of my motors and try it out before the end of the season I’ll post back.

Ok, so curiosity got to me. I installed the plate on my ’55 Johnson 10 horse, and took it out yesterday. This wasn’t an extensive hours long test. Just an initial test to see if this plate would have any immediate negative effect on the way the motor ran. I would have to say it did not. Maybe if I ran it longer, or tested on a bigger motor there might be, I don’t know. I looked at the top plug before and after and it looked to be burning about the same, maybe only slightly wetter?.

https://youtu.be/8YZ_BOiuMp0
https://youtu.be/R4De-DZ7O28

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