Building a hopped up 5hp FH and I have some questions

Clayon

Clayon

#1
#1
Ok, for the last month or so I have spent some time trying to find all the info I can about building a modded 5hp Briggs flathead. I have also spent some time gathering parts. The motor I have is a 5hp Briggs I/C flathead, with the sleeve and the 2 bearing on the crank.

I know that first and foremost if I remove the gov. like I am doing I will need a billet flywheel and connecting rod, which I have. The flywheel is stock size, and the connecting rod is 3.875'' from ARC.

I also bought a 233ss cam. What kind of springs should I use with this cam? or do I need aftermarket springs? and will the stock valves be good enough?

Also, should I get billet lifters? and if so, would the +1.00" billet lifters be okay?

Okay, now what about the carb, can I just jet the stock Briggs carb to work? or should I get a raptor carb instead?

I know how to port/polish the block, clean up rough castings, trim the eyebrows, etc. but what about milling the head? If I trim the eyebrows to increase flow, would milling the head just be going backwards? or how much would be okay to take off?

I bought an advanced flywheel key kit from Riekens Racing, what degree key would be best to use on a motor like what I'm building?


I know I've asked alot of questions, but I really appreciate the help, because I want to make sure I get the right combination of parts so that I build the motor right.

Thanks in advance for the help. :thumbsup:
 
bigdadywayne87

bigdadywayne87

New Member
#2
#2
well as far as i know when you shave the eye brow you increase the cc of the head and by milling the deck or head you lower the cc for higher compression but as flow goes it's all in the angles so go bigger valves and do 3 angle valve job if it's for racing if not i would not worry and for your cam i cant say for lifters i run stock but you do need to up grade the springs and retainer for sure once you use a over stock lift/duration cam and i do know if it is a high lift/duration cam you need billet steel lifter's that's all i have in the briggs world for info
 
vwfan79

vwfan79

Active Member
#3
#3
I may be wrong but I think with that cam you can use the stock size lifters, and yes go with the billet one. It would be a good idea to get new valves and lap them but stock size should be good for your set up, get the dual spring kit and just use the outside spring it come with retainers and locks, Turk Brothers racing has everything at great prices too. I didn't mill my head but used a thin copper gasket and it seems to have higher compression when I try to pull start it, I have to get it past the compression stroke or it rips my arm off. I used a 6° timing key and its seems to be a good fit. As for the carb the raptor one would flow better but not an expert on these so someone else will know better.
 
creia

creia

#5
#5
Re: Billett Lifters
Depending on the lift of your cam, you MAY have to have "reliefs" (tapers) cut in the block to accommodate the lifters. This is a job best left for for a machine shop unless you really know what you are doing and have the correct cutting equipment . "Billett" lifters have a radius (more material) where the stem meets the flat bottom plate, which gives them their added strength. If possible, and you are preforming a relatively mild build, go with the stock Briggs 5 HP lifters. I remember that there was a OldMiniBikes member awhile back that bought billett lifters and ground off the radius instead of having the block reliefs cut, which kind of defeats using (and paying the $$$) for billett lifters in the first place.
Michael
 
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vwfan79

vwfan79

Active Member
#6
#6
Yup that was me, not the recommended way but I would have to image the material of the billet lifters over all is stronger. I personally didn't like the idea of removing material from an area that is already a weak point in the block, and I didn't have resources to have someone weld the lifter boss. This is my opinion and I am still happy with my decision. My cam has .300 lift and would allow the exhaust lobe to go by but not the intake, with your cam at .233 you may be alright.
 
roccosbike

roccosbike

#7
#7
Clayon, a 233 cam is just a stock lift cam with a more aggressive ramp lifting the valve,so you can use stock billet lifters and you can buy a pair of them from these guys. American Power Sports - Karting Parts & Accessories you dont need real tight springs for that cam either, that cam is known as a slapper cam.just run two raptor exhaust springs and your good.Oh you can get the springs from the same outfit.No reliefs will be necessary. Be careful starting the motor because that cam has no comp release,get it just past the comp stroke then give it a good pull.:thumbsup:
 
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creia

creia

#8
#8
I would recommend installing UPPER valve spring retainer (cups) as well. If you go with a Raptor valve spring kit as Rocco recommended, I believe that they will come with them.
Michael
 
Clayon

Clayon

#9
#9
Thanks guys for all the info. Wouldn't the stock size billet lifters be the exact same size as the stock lifters? I think I will get some just to make sure everything is strong enough.

As it turns out the cam I am getting is not a 233, it is 96-3, the guy I am buying it from just degreed it.
 
creia

creia

#10
#10
Clayon said:
Thanks guys for all the info. Wouldn't the stock size billet lifters be the exact same size as the stock lifters? I think I will get some just to make sure everything is strong enough.

As it turns out the cam I am getting is not a 233, it is 96-3, the guy I am buying it from just degreed it.
Click to expand...
Clayon,
It is not about the SIZE (length). Relief cuts in the block are typically needed due to the different SHAPE of the billett lifter, at the bottom. The taper (radius) will not allow them to penetrate the block far enough to lift the valves high enough. take a look at some "regular" Briggs lifters and compare them to "billett" lifters- the difference is easy to see.
Michael
 
jeep2003

jeep2003

#11
#11
the billet lifters arnt necessarily stronger. you get them because they are lighter so you can rev it higher without valve float. and in turn you can also run softer springs
 
PhilosoRaptor

PhilosoRaptor

New Member
#12
#12
Hey there fellow Canadian :thumbsup: Just a few things to add.

If you already have the ARC flywheel model number 6620 seen here ARC Flywheel, then it is already going to advance the timing to 30* BTDC.

Now if the seller of the cam is correct in calling it a 96-3 then you are looking for 28-29* BTDC for timing.



So you could just run a normal straight piece of keystock or maybe experiment with a 1-2* offset key being inserted backwards to retard the timing to within spec.

As for milling the head I decided to use a thinner head gasket to compensate for the loss of compression from shaving the eyebrows. Anymore compression and advanced timing and I would really be asking for trouble trying to pull start! But like all the others have said, just roll it over to the compression stroke and give it a good pull!

Other than that I hear the 96-3 is a little hard on the block and lifters so you may want to weld the areas around the lifter bore!

Cheers and good luck :smile:
 
Clayon

Clayon

#13
#13
Thanks Michael, I understand what you mean about the lifters now. And thanks PhilosoRaptor for all the info, I will use a copper head gasket instead. :thumbsup:

Does anybody have a picture or know where I could find a picture of a block with the reinforced lifter bor area? I guess I should get that done right away.

Also, can anybody tell he how to determine the degree of a cam?

Thanks. :thumbsup:
 
PhilosoRaptor

PhilosoRaptor

New Member
#14
#14
Clayon said:
Does anybody have a picture or know where I could find a picture of a block with the reinforced lifter bor area? I guess I should get that done right away.
Click to expand...
Hey Clayon,

Here are some pics of the lifter bore area that I had my friend weld for me. I told him to add as much extra material as he could, afterwords I just ground it flat and made sure it interfered with nothing that would be moving inside the engine. Be careful welding, my friend said I should have lent him the lifters in order fill the bore so nothing burnt through. I had to do a little reaming of the bores afterwards because of this.

There are some more pics on the forums, I just can't find the threads at the moment. EDIT - here is one thread http://www.oldminibikes.com/forum/briggs-stratton-engines/42667-5hp-briggs-build.html#post291793




 
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creia

creia

#15
#15
Clayon,
The 96-3 cam is MUCH more radical than the 233! I have heard that some guys in the karting forums nickname these "Block Busters" (for very good reason) due to how hard they are on the engine. As others have already advised, you should get block work (welding) done to strengthen it, by someone that really knows what they are doing.
Michael
 
Clayon

Clayon

#16
#16
Thanks for the picture philosoraptor. :thumbsup: No I see better what has to be done. :thumbsup:

And thanks Michael for the info on the cam, I will either get the block work done or I will get a milder cam. :thumbsup:

How would I go about checking to see if this cam actually is a 96-3? :shrug:
 
Clayon

Clayon

#18
#18
Ok thanks Chad, that will help me out alot. :thumbsup:

I guess I should have thought of that because I think the Dyno cam in my 6.5hp clone has the number there as well. :doah:
 
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