OPS .67 Engine setup

[AaronWilson]

Hello everyone,

I am brand new to this hobby. About twenty years ago my dad and I started a 1/8th scale Pay n Pak dumas hydroplane kit. It got set aside in the closet until a few years ago when I picked it up with the idea of finishing our twenty year old project.

I have bought an OPS .67 engine to power this thing. Unfortunately, I am having trouble finding information on the engine. I am hoping to know the factory settings for the screws and the proper path for the water cooling. Sorry that these are such basic questions, but I have been all over the net and have failed to find answers. If there are diagrams available somewhere I would be eager to see them.

Thanks so much for any help you can provide.

Kind regards,

-Aaron Wilson

 

[brad nichols]

Start with the needle 3 1/2 to 4 turns out. If this is a new motor let it run rich for a few tanks. Motor should burble when it runs and not scream. When motor has some run time on it you can start to lean it by turning the needle in. When set properly the motor will stumble for a second or 2 then rev when the carb is wide open. Get a good pipe and set it at about 11 1/2 to 12" to the start of the widest diameter from the plug or centre of the cylinder along the pipe length. If you are cooling the exhaust, go through the top fitting then out the bottom then to the head and out. Find a local club fellow boaterhere on IW or post where you live and get with some fellow boaters as it is always better to run with others and they can provide lots of help and information. You will also meet some of the nicest people in the world!!

Brad

 

[Matt Smith]

I ran one of these engines the past couple of seasons, and I always had issues with it running hot. You will need 2 water pickups, one for the cooling head, and one for the exhaust. I pulled the cooling head off, and used a dremel to make the ports a little bigger for more water flow. It definitely helped. I ran a Macs pipe at about 11-1/2'' without issue with an X460 Octura prop.

As far as anything OPS goes, I would contact David Simpson. www.gotnitroonline.com

 

[Ray Sametz]

Aaron, set the head clearance at 0.018 thousands. If you can find an aftermarket rod (RPM) change the stock rod. Run a high oil content in your fuel. Follow Matt's suggestions also. PM me your address, I'll send you some S/S bolts for that motor. Run a rich fuel mix or you'll surely hurt the motor.

 

[Rudy Formanek]

When OPS 67's were the hot engine (back in the 80's), we would all put Aeromarine drum valves on the back, RPM rods and RPM carbs. The OPS super needle bearing conrod set-up didn't work for us. The Keeley titanium needle bearing rod didn't work for us, maybe because we would run 60%. They might work if you run 15%. The stock disc valve would break if you ran it long enough. Set your motor mount up so you can swap in a CMB Greenhead, probably what you'll go to next.

 

[Jerry Betke]

My son Mike and I ran these engines successfully for a number of years. The engine you have will work just fine in your scale. The above suggestions on cooling, pipes and fuel are good. If the engine has a disc valve, we found the best performance and life was to set it as follows. Loosen the retaining pin set screw and slide the disc out. Place the disc on a flat surface to check that it is not warped. If it is warped excessively, you will need to find a replacement. We would lap the back plate surface to assure that it was flat. When you are reassembling the disc, place a .002 shim under one side of the disc, push the retaining pin to hold the disc tight against the back plate while tightening the set screw against the retaining pin. Slide the shim out. We found this to be the ideal clearance for the disc. I would recommend putting a second set screw in to act as a lock. If you use locktight on the set screw it will most likely find its way to the retaining pin, making It most difficult to remove. We found that the engines performed best on 50% nitro with 18% oil content. I have some other suggestions to share as well. Also, I have some parts, drum rotors and carbs for these engines that I would like to sell. PM me your e-mail address if you are interested.

 

[Jerry Betke]

Brad, I will put together a list and send it out in a couple of days. Merry Christmas, Jerry Betke

 

[Jim Allen]

I ran highly modified OPS .65, .67 & .80 cu in engines for many years. These engines with their 5 transfer design became the basic design for my .90 cu in bar stock engines. The photos show some of the parts that were re-designed to make the engine reliable. They include; balanced inverted drum valves; fully balanced rotary valves; fully balanced bell valves; crankcases; cylinders; pistons; carburetors; tuned pipes; crankshafts; hardened steel roller rods; hardened steel front ends; etc. The basic 5 transfer design, with radial angle changes, proved to give excellent scavenging characteristics with bore increases from the original .956" to 1.125". The exhaust's width, shape & angles were also modified to give better flow. The stroke remained at the original .902" length.

Jim Allen

Note; Fuel used; 80 % nitro, 12 % ethylene oxide, 8 % oil.

 

[Tom Foley]

Good engine but requires slightly rich needle and 20 % oil . Run 25 % nitro with the stock head button @ .018 - .020 and it will live a happy life . bearings are small so change them frequently and flood the engine with after run oil when through . stock water fittings are too small , re- drill and tap to 10-32 for big water fittings . The International Hobbies water cooled exhaust adapter was a good part if you can find one . You can also make a coil of tubing to carry water around the exhaust coupler for longer life . I still have a few .65's and .67's for fun running but can't seem to get to it !! Good info from all the guys here .