Novarossi keep .21 head squish

[James Schmidt]

Hey guys I have a new NovaRossi keep . 21MP inboard. From Ron Shaw. It's the same engine as the .21 keep/ M outboard. Anyway, if you run this motor in your outboard let me know what head clearance work for you I will be using stock head Botton. I run 60% nitro. Do any of you guys know what the clearance is without any shims on the stock head Button? my engine came with two heads shims one 11 Thousand and one 4 thousands. I am wondering whether I have to buy a shim kit to achieve the proper head clearance. Since I don't have a squish gauge I may have to go to the auto parts store and get a plastic gauge kit if no one on here knows what the head clearance is without shims. Everyone's preference on head squish may vary 1000 in either direction but just looking for a ballpark.Any input would be appreciated

Thanks

Jim

 

[Bill Britton]

About 8-8.5 ought to be pretty good.

 

[Mike Hughes]

Using a piece of thin solder, you can squish it at top[ dead center and then use you mics for a measurement. Or just pull the head and do it that way. I like the solder way......Im lazy LOL

I do believe you will have to loose that .011 shim. Might have to keep the .004 shim. I personally run .006 in my 21s.

 

[Brian Sorgente]

Everyone has their own way of doing things but if that motor has a domed and dished piston (yes you read that right) plasti guage is the way to go. I havent run a keep yet but head clearance is pretty standard across the board as long as youre bowl volume is in line. I always break motors in rich at 0.012 then drop them to ~0.008. Tighter is always better but if you expect to pop a plug once in a while and dont feel like diging elements out of the head/ piston, 0.008 works well. At the end of the day it depends on what youre looking for but that should get you in the ball park.

Brian

 

[James Schmidt]

Many thanks guy's I run all my other 20 motors at 0.008. This is the first nova Rossi I've owned in quite a while, I wasn't sure if I'd still run the same clearance but thank you for the help. Sounds like I need to get a shim kit. I've been breaking it in on the bench this is going to be a good running motor she sounds great !!

 

[RonShaw]

James,

Great advice above on head clearance. .006-.008 is a great number for 60%. I personally like using a depth guage with plug adapter as working with those types of clearances is very critical. Check the center depth of the dish on the piston first. Its usually around .013-.015 deep. This will be added to your .008 you are looking for so with the adapter you will now shoot for .021-.023. Since the squish is tapered and doesnt always match up perfectly with the piston, I prefer the depth guage over the plastiguage and solder methods, as the closest point of the squish and piston will be up next to the sleeve and will prevent an accurate measurement with the other methods. There are guys that make the glow plug adapters to fit any standard digital or analog dial depth guage.

 

[RonShaw]

James,

BTW, the easiest way to measure the center depth of the dish on the piston is to remove the head button and piston/rod assy. Install the adapter into the head button and install guage. Place head button directly on top and centered with the piston. Zero the guage. Then remove from the top of the piston and place on top of a flat piece of glass. The number you get (usually .013-.015) will be the depth of the piston dish.

 

[James Schmidt]

Thanks again Ron for the help!! I have a quarter of a gallon threw it on the bench, and she still tight as all get out.I think it will be a full gallon with a heat gun before I can put it in my boat. It's a lot of work but I know it's gonna be worth it !! I can tell this motor has a lot of power. she sounds great !!

I'll let you know how she performs once I got it in the boat and dialed in

Thanks again

Jim

 

[RonShaw]

Sounds great Jim. Patience is key....

 

[Alan Elzer]

Just curious how long do you run engine each time. And what temperature do you try to maintain or does it matter?

Sent from my SM-N920V using Tapatalk

 

[James Schmidt]

You know timing each run sounds like a good idea I never thought about that, but I've been running 10 ounces at a time it's probably running around five or six minutes maybe. The way I figure it 10 ounces at a time is like eating an elephant. It's done one bite at a time.

The temperature however is important on a brand new motor. Cold is not good. You probably heard this im many posts on his site . But it's not rocket science .

Temperature is needed to expand the sleeve so it cycles with out to much pinch.You can damage your engine if you don't reduce this pinch.

The temp I use is that that lets engine cycle without stress. The first time I tried to roll it over I had to heat it with heat gun to between 250 and 260. Now after 3/4 of a gallon of Fule through it, the motor rolls over freely at 190 degrees. So while engine is running I try to keep it at 190. It's hard to do with all that Fule running rich through engine cooling it off, so it may be a good time to put it in my boat and run it with out cooling.

Some will suggest an exact temp, but I think it's about what's needed. This engine is one of the tightest engines I every broke in, so heating it up was a must IMO. Believe me I'm no pro and had a lot of help from some people who been in the hobby for many years.

Hope this explains my position and helps you

Jim