Author Topic: New Build- New Questions  (Read 11420 times)

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Offline LittleMow

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New Build- New Questions
« on: March 14, 2010, 10:20:55 pm »
Couple questions on my first engine build. Some info i did not find with the search button. Hope this helps some other newbies as well. I'm working with a 31" (17hp to be exact) OHV Single cyilnder  Non-Avs engine. Cheeta Cam from mike at precision Cams, EC Balnced crank, EC Milled head, EC springs/Retainers, EC roller Rockers, Mild port/Polish, ARC Rod and flywheel. Now i have talked to a few guys from heymow and they have enlighted me alot about what to do, but here a few things i'm unsure about:

- The stock plug is a RC12yc champion, atleast this is what was on the motor. Should i run this plug or does anybody find that an NGk or other brand works better? Cold or Hot Preference?

-There is alot of info about the EC copper head gasket on here, I wish EC could have put a note of preping the gasket in with the new gasket but when torque the gasket to 250 inch ibs; should you do this in incriments? If so how much of an incriment? or from hand tight right to 250 in lbs?

-When mounting the engine to the frame do yall use the stock spacers under the oil pan? Or mount it rite to the frame? Not sure if flex or tweak would affect the engine block.

-The stock engine Tins for my motor had 2 top engine covers, a black metal cover then brackets for a second Red top metal cover. Being Air cooled should i run both covers or just one cover?

-Walbro 56 carb- The fuel line inlet hose on mine is a very short brass fitting coming straight out from the carb body. This fitting is about a 1/4" long, not big enough to even fit my fuel line with a clamp, does this come off of the carb or is it missing something there?

-Lastly exhaust, I plan on running 1 1/8" ID from head to 1 1/2" ID to 1 7/8" out the side. Do you think this pipe is big enough to have a deep tone? Or is this to big of a jump in size?

Well thanks all for reading  :D Any info you have would be appreciated! Jim
*2010 2nd year/ First year mod-x c/p*
*2009 1st year build/ IMOW class*

Offline The Tank

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Re: New Build- New Questions
« Reply #1 on: March 14, 2010, 10:24:15 pm »
I prefer the NGK plug, had too many problems out of the champion. I run the NGK equivelent of the stock champion plug. The the piece coming off of your carb is missing the plastic elbow that will press onto it. As for my engine its bolted straight to my frame and haven't had any issues. Yes Id use both tins on the engine.
Frank "The Tank" Woods

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Offline LittleMow

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Re: New Build- New Questions
« Reply #2 on: March 15, 2010, 03:50:16 pm »
tank- thanks how about the exhaust? is this about the correct step up in sizes?
*2010 2nd year/ First year mod-x c/p*
*2009 1st year build/ IMOW class*

Offline The Tank

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Re: New Build- New Questions
« Reply #3 on: March 15, 2010, 03:56:58 pm »
I think the 1 1/2" exhaust should be big enough. I stepped up from 1 1/8" to the 1 1/2" on mine and it has a deep tone.
I did forget to mention the NGK spark plug number. The NGK number is BKR5E.
Frank "The Tank" Woods

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Offline Huffy044

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Re: New Build- New Questions
« Reply #4 on: March 15, 2010, 08:33:02 pm »
Try to find a earlier one peice tin for your flywheel cover. When you go from a stock flywheel to a ARC wheel you will notice the ARC flywheel is thinner than a stocker. You need to cut the bottom side of the tin off so it drops down to within 1/4" of the fins on the flywheel. I am talking about the opening in the shroud. The fins act like the impeller in a pump and the opening is like the wear plate.  If it's not close air just moves around and slips out. Look at a old car and see where the fan goes in the shroud, close and near the end.

Copper head gasket: hang it on a wire, take a propane hand torch and heat it until it turns purple, this is annealing it. drop it in water or let it cool, then coat it with copper coat twice and let it dty, torque like you said in small increments. I use ft lbs, start at 5 and go up 5 each time. I have gone back after several heat cycles and retorqued it but found no increase was needed, Besides you have to remove the exhaust to get to one of the bolts.
Forgot to tell you, when you break the rockerams and the rocker studs, email me and I'll tell you how to fix that problem. tdaniels@smurfit.com
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Offline LittleMow

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Re: New Build- New Questions
« Reply #5 on: March 15, 2010, 09:50:13 pm »
ok thanks guys. this helps alot.

huffy, im runnin ec rollers with the plate trick. should be ok from what i hear.

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*2009 1st year build/ IMOW class*

Offline markiemark

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Re: New Build- New Questions
« Reply #6 on: March 15, 2010, 11:29:46 pm »
i used lil propane hand torch but it didnt seem to work im going try use a noraml torch to heat it up
Mark Laird
www.northbaylawnmowerracing.com
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Offline jerb

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Re: New Build- New Questions
« Reply #7 on: March 16, 2010, 12:09:59 am »
modifying the tin work as such is worth about 25 degrees reduction in cylinder head heat....i think i took about 1'' off bottom of shroud and opened the whole to match the flywheel..
Tim Jerby
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Offline LittleMow

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Re: New Build- New Questions
« Reply #8 on: March 16, 2010, 09:24:18 am »
Alright that helps a bunch, New problem: I ordered a briggs piston # 796172 for my standard bore 31" this pistons part # superseddes to #791937. well the rings it came with have a gap of .045!!. Measured my bore it is 3.569. My stock piston measured at the same at a 3.569 at the bottom of the skirts. The old "stock"  ring gap i measured at .028 which is within the briggs .030 specs in the book.

 Buuuut The new piston is a 3.559 and like i said with a ring gap of .045. At first i figured my bore was maybe .020 over being it has a "sears reconditioned" sticker on it. Now i'm thinking i have order the wrong piston, or maybe received the wrong piston? Anybody know which piston i should be using? O i'm also running the 6279 rod with the large journal 31 crank.

George- if you see this, i talked to you last night about this problem, so here are the specs that i have gotten from it.
*2010 2nd year/ First year mod-x c/p*
*2009 1st year build/ IMOW class*

Offline LittleMow

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Re: New Build- New Questions
« Reply #9 on: March 16, 2010, 01:32:27 pm »
ok well new info. Looks like i have a .010 piston and bore. For some reason my doner engine has a .010 piston in it. So thanks to all for helping me out! Looks like back to the machine shop!  :doh:
*2010 2nd year/ First year mod-x c/p*
*2009 1st year build/ IMOW class*

Offline LittleMow

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Re: New Build- New Questions
« Reply #10 on: March 28, 2010, 11:04:00 am »
Well back to my ring gap problem. I have gotten a .020 OS piston from ec. Took my .010 OS block to a machine shop and had the block machined .013 more for a total of .023 over stock. I could not find a spec of piston to bore clearence in my briggs book, but the machine shop guy said .002-.004 is what he does all the briggs motors. So i get home and go to check my ring gap with the .020 OS rings. And i'm getting .018 ring gap with the ring set about an inch down into the cyilnder. Before the shop did my block i set the .020 os rings in and they overlapped.(of course they were bigger then the bore). Being .023 over stock bore i should have .003 ring gap......

So am i checking my ring gap correctly? I was shooting for .003-.005 like i read george does but .018 seems like i might have alot of blow-by problems?  I'm Lost for words on this issue. Im getting burn'd out on this engine and have not even started to assemble the engine yet.. what ya think? :confused:
*2010 2nd year/ First year mod-x c/p*
*2009 1st year build/ IMOW class*

Offline birdman_express

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Re: New Build- New Questions
« Reply #11 on: March 28, 2010, 01:39:25 pm »
You had the right idea in your thinking, but you didn't use the right math.
Pi needed to be involved in what you wanted. You need .020 rings with a
regular piston to file fit close, so with a .020 piston, you will need larger rings still.
Marc Baker

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Offline LittleMow

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Re: New Build- New Questions
« Reply #12 on: March 28, 2010, 01:53:53 pm »
So for a grass cutter what i have now will work fine, but high rpms more heat and such .018 is not good. ok so now i have to get custom cut rings? Briggs doesn't make anything bigger then a .020 set of rings. Where should i be looking to get a set?


I found a briggs # 690168 for .030 oversized rings. This is odd considering i heard they don't make anything bigger then .020. Thoughts?
*2010 2nd year/ First year mod-x c/p*
*2009 1st year build/ IMOW class*

Offline markiemark

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Re: New Build- New Questions
« Reply #13 on: March 29, 2010, 12:30:58 am »
briggs  made .30 over at one time but no longer does so that part number is no longer good unless you find a dealer with new old stock and just happens to have them.
Mark Laird
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Offline LittleMow

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Re: New Build- New Questions
« Reply #14 on: March 29, 2010, 09:12:03 am »
Well i called a few local places and they do not stock them. called 3 places i found online and nobody has stock in them. So does anybody have a set or know of a place where i can get a set of these? #690168 briggs part number. My only other option is to resleeve this block i guess?
*2010 2nd year/ First year mod-x c/p*
*2009 1st year build/ IMOW class*

 

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