Heymow - Lawnmower Racing Forum
Engine Help => Briggs Flathead => Topic started by: Tom Price on November 06, 2008, 01:31:50 pm
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Is the Billet rod model 28 the stock length I assume? Also the billet counter weight link, that is the links for the synco-balance on my 28cid flattie right? Kinda new to lawn mower engines but tryin to learn!! So if I put the billet flywheel on it would be wise to put a billet rod, counter weight links and cam in so I don't blow something else up right?
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The standard length ARC rod is number 6280, I believe that is the one E.C. lists as the model 28 rod. The billet counter weight link (dog-bone) is a much needed item, as the factory ones are prone to breaking and sending the balancer out the back of the block. If you have a crank with the removeable eccentrics, you could one up it and remove the balancer all together and install the ARC counter balance weights on the crank. The billet rod is also a good thing to have. These items wont really net you any more power (well, some due to less weight), but they help the engine live. You need to make a strong foundation before putting all the power into it. Once all the weak links have been addressed, then worry about cam, carb and so on. Putting in that expensive can, only to have a weak rod fail and break the cam on it's way out the block is no fun.
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Yeah, that's what I was wondering if those were the critical parts to upgrade in a mower engine to upgrade when you start building. I know when you build car engines its the same way with fixing the weak links first. I was basically wanting to put a billet flywheel on and remove the governor. BUT I new more rpm's meant other stuff wouldn't take it so I was going to put in a billet rod and a race cam with the billet "dog bones" for the syncro balance. Not wanting to spend a ton now, just get a good foundation for future mods. Thanks!
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Depending on how wild you are going to get with the engine you could get by with an OHV rod and a billet dog bone.
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If you have a crank with the removeable eccentrics, you could one up it and remove the balancer all together and install the ARC counter balance weights on the crank.
You mean the brass counterweights? Then I can remove the syncro-balance? Just making sure I completly understand what you were refering to. Like I said, kinda new to mower engines. :rockwoot:
Depending on how wild you are going to get with the engine you could get by with an OHV rod and a billet dog bone.
Not too crazy, just want something that will be strong and durable. What I mentioned previously would be about it for a while.
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Yup, if your crank has the removeable eccentrics, take the whole balancer out and install the brass weights. You get a bit more viration at low rpm, but it balances out higher up. You could go the ohv rod route, but the billet rod will last the engines lifetime more than likely, so once you have it, you have it. That's just the way I look at it. Spending a bit more now will save you a bit more later in my opinion.
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Cool, Thanks! You cleared up a few questions I was wondering about, appreciate it! :)
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the 6280 ARC rod is NOT the same length as the stock rod, you must use the AVS piston with the 6280 rod!! check the pic in this thread out.
http://www.heymow.com/index.php?topic=8427.0
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HMM, old age must be creepin in on me, forgot about that. Yup, need the avs piston to go with that rod as well.
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HI i was in the same boat as you the beg. of this year and if fig out some things im list to help you out
1. The billet syncro link is important its only $25 and they will break it happen to me and cost me a whole motor.
2. the Arc brass weights i have had no luck with them at idle or lower rps id say under 2000rpm the machine vibrates extremly. so be smart and leave them alone.
3. Use a Stock OHV rod and piston combo and it will work very wheel i ran like this all year reving up to mid 5000rpm and worked fine and also can be done cheap.
4. Advance your timing a smalll amount maybe order a #3 key going to much and it will be hard to start and will loose more then gain.
5. It all about the FLOW in a flat head so maybe a 11hp briggs head but dont go shaving the head alot cause again you loose more then you gain.
5. Try drilling the main jet in the carb that the jet in the bottom once you take the bowl off try drilling by .002 intill it revs all the way up and seems to run well.
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HI i was in the same boat as you the beg. of this year and if fig out some things im list to help you out
1. The billet synchro link is important its only $25 and they will break it happen to me and cost me a whole motor.
2. the Arc brass weights i have had no luck with them at idle or lower rps id say under 2000rpm the machine vibrates extremely. so be smart and leave them alone.
3. Use a Stock OHV rod and piston combo and it will work very wheel i ran like this all year revving up to mid 5000rpm and worked fine and also can be done cheap.
4. Advance your timing a small amount maybe order a #3 key going to much and it will be hard to start and will loose more then gain.
5. It all about the FLOW in a flat head so maybe a 11hp Briggs head but don't go shaving the head a lot cause again you loose more then you gain.
6. Try drilling the main jet in the carb that the jet in the bottom once you take the bowl off try drilling by .002 until it revs all the way up and seems to run well.
Every word is right on! I have done the same thing except for #1 and #6 and I can get my motor to 5,500rpm on the track. It has stayed together (so far).
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For a fairly stock build I would disagree on the 11 hp head. I am running one and I love it. If you are running a stock cam that is the way to go.
Rather than just drilling out the jet a little at a time I would order an adjustable needle for it. It is very cheap to do and it will be much more tunable.
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Yea I forgot to add that I had a cam in it...
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I think you mean the adjuistabale get on the bowl if so there is a actual jet inside the carb you need to open up to allow more fuel to flow into the carb. Yeas you need the adjustable needle but u will also need to drill the main jet out itself. Take the carb and undo the bowl and remove and you will see up in the hole a slot for flat head screwdrive take that jet out and it be long brass tube with a hole in the middle and then 2 holes on the side. That the way iv been taught how to correctly do the carb jetting.
Rember all lil things add up. Use the search on the fourm and type and 99% off any question has been posted on here once. THis site is almost a bible to me.
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the 6280 ARC rod is NOT the same length as the stock rod, you must use the AVS piston with the 6280 rod!! check the pic in this thread out.
http://www.heymow.com/index.php?topic=8427.0
So the 6280 is not stock length? Well.. is the OHV rod strong enough that if I put a cam in it I don't have to worry about it coming apart? Where do I get the AVS piston for the 6280 rod and will it work with the stock crank?
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Nope it's not, it was designed for that piston...
Yep...it is strong enough...
Nope you don't have to worry...
Just order it with the rod...
Yep it'll work with stock crank.
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Will the OHV rod work in place of the flattie rod?? Meaning same length, just swap them out or swap out the rod/piston assemblies? Any part#'s for the stock OHV stuff?
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Will the OHV rod work in place of the flattie rod?? Meaning same length, just swap them out or swap out the rod/piston assemblies? Any part#'s for the stock OHV stuff?
Yes the rod is the same length as the flathead rod. I believe the part number is 494504S. So all you will need to order is the rod (around $36), a gasket set (around $30), and a billit dog bone(around $25). That will give you a strong depenable bottom end.
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My engine in a 28T707 and it says that is the same part# for the rod as you gave me for the OHV... What would a model code be for an OHV engine?
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My ohv is a 28n707. If I recall correctly, I thought someone had said that briggs may have superceeded the standard l-head rod to the same number as the ohv rod..not sure on that though.
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I did read somewhere that the old OHV rod was superceeded to the new # I was given... so I wonder if that means that my rod will hold up?? :confused: But my parts list I have here for my motor says part# 494504 not 494504S...
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I think that came about just recently. Your engine may be older, and have the old style rod in it more than likely.
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Looks like the old 494504 rod is being replaced by the OHV rod, the 494504S. 8)