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Old 12-27-2008, 01:20 PM
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briggs help!

i have a 6.5hp briggs intek. im looking to get some more ponys out of it. does anyone know what i should do? im going to shave the head down but i dont know how much . thanks for the help

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Old 12-27-2008, 01:35 PM
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Shaving the head should increase compression a bit.....thus more HP.....

Go to this link.....

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Old 12-27-2008, 01:57 PM
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I am guessing the intek is still a sidevalve engine. If it is, shaving the head as well as cleaning up the ports will help. A word of caution regarding milling the head...too much will cause the valves to touch the head, I discovered that as a teenager. Took a while to trace it down, but cure the problem with clearancing the head around the valves. The combination did 2 things, most likely cause some flow restriction and secondly, after milling the head(actually, lapping as we did Motorcycle heads) so much to bump compression, I probably lost a considerable amount when cutting for valve head clearance. I could have probably generated more power with a less shave and not notching the head. They,like flathead Fords,benefit from "relieveing" around the valves and to the cylinder. If the intek is an overhead valve...most of what I posted will be useless.
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Old 12-27-2008, 02:00 PM
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hot briggs

I worked with the nephew of Bus Schaller who did the camshafts for Mickey Thompson's Indy cars... they set some motorcycle records at bonneville... george pulled 19 HP out of a 5 hp briggs...george made a new con rod out of a 1 inch aluminum plate, drilled and crossed and put a dipper on it. I don't remember if he made a new head or just milled and did valve clearance ...ported and relieved the block like they did on old ford flat heads ..You grind an air channel in the top of the block and round the side of the top of the cylinder so the air flow is smothed.. just don't go below the ring heigth unless you pin the rings so they won't rotate. George coppied the cam profile he wanted from a hot 2 liter ford 4 he had. he used a degree wheel and dial indicator to graph it out then marked the Briggs cam with machinisrts die and started on a bench grinder grinding and checking then smothed the profile with a belt sander .. when he was done he took it into the Ford factory and had a machinist.. heat it and either nitride or the casinite it. You can buy casinite in a can, heat the cam and cover it with the powder and bake it... then a slow cool down... and hope it doesn't warp. I don't know if he used a different piston or not. ..he used some motorcycle valves and springs. He made a new intake pipe and used a small motorcycle carb. I think it was a mikiuni ? It pulled 19 HP at the gocart shop and surprised a lot of people when his kids were racing.
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Old 12-27-2008, 02:02 PM
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safe as any other sideshaft- bump the compression up to ablout 11:1, port the head, bigger carb, bigger cam, stiffer springs, exhaust pipe.
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Old 12-27-2008, 03:03 PM
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Quote:
Originally Posted by 1995nicholas
i have a 6.5hp briggs intek. im looking to get some more ponys out of it. does anyone know what i should do? im going to shave the head down but i dont know how much . thanks for the help
Just to set the record straight, your motor is probably rated for 6.5 ft/lbs of torque, not 6.5 hp. Here's the blurb from Briggs....
"For walk-behind mowers, Briggs & Stratton engine sizes typically range
from 4.50 to 8.75 gross torque. For riding mowers the sizes typically range
from 10.5 to 26.0 gross horsepower"

When we were racing go-karts years ago, some of us dads got together and formed an outlaw class for ourselves using the 8-horse block. (This is back in the day when Briggs rated these small motors by hp, not by torque like they do now). Most of us were old enough to have lived through the flathead "hop-up" era, so we fiddled around with using a rotary grinder mounted with a burr for cutting aluminum and JB Weld to re-contour the intake port in the block. Using a D shape in the port will help flow. The flat part of the D should be on the short turn radius.

We relieved the blocks down to the top of the top ring with the piston at TDC. Using a layer of clay on the underside of the head and turning the motor through a cycle will tell you exactly where to cut the head for valve clearance when shaving the head. Cut a relief in the head so that the valve sinks into it at full lift. It's hard to explain without a picture, but if you envision holding the head in front of you, you could drop a thin coin the size of the valve head into the relief and it would fill the relief back to the surface of the combustion chamber. Cut the relief just deep enough to provide a few thousandths clearance between the face of the valve and the head at full lift.

You can more than likely buy hot rod cams for them off the shelf now, but back then, we mounted the cam up in a vise and twisted it to a few degrees retard to give the motor more top end. Looking through valve spring specs from a TRW catalog yielded a stronger spring that would drop in.

We used to use a much larger Walbro pumper carb that was converted to use alcohol. Yeee-haw.

Last edited by techinspector1; 12-27-2008 at 03:10 PM.
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Old 12-27-2008, 03:29 PM
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this engine is off a pressure washer. im going to use it for a 10ft fan boat. it says 6.5hp on the side of the motor and is a ohv. i have a 6.5 on the boat now and it just a little to slow for me. i was thinking that if i get a fue more ponys out of it the boat will go better. but i dont know how much to take off the head? .010-.015-.020????
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Old 12-27-2008, 04:51 PM
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Quote:
Originally Posted by timothale
I worked with the nephew of Bus Schaller who did the camshafts for Mickey Thompson's Indy cars... they set some motorcycle records at bonneville... george pulled 19 HP out of a 5 hp briggs...george made a new con rod out of a 1 inch aluminum plate, drilled and crossed and put a dipper on it. I don't remember if he made a new head or just milled and did valve clearance ...ported and relieved the block like they did on old ford flat heads ..You grind an air channel in the top of the block and round the side of the top of the cylinder so the air flow is smothed.. just don't go below the ring heigth unless you pin the rings so they won't rotate. George coppied the cam profile he wanted from a hot 2 liter ford 4 he had. he used a degree wheel and dial indicator to graph it out then marked the Briggs cam with machinisrts die and started on a bench grinder grinding and checking then smothed the profile with a belt sander .. when he was done he took it into the Ford factory and had a machinist.. heat it and either nitride or the casinite it. You can buy casinite in a can, heat the cam and cover it with the powder and bake it... then a slow cool down... and hope it doesn't warp. I don't know if he used a different piston or not. ..he used some motorcycle valves and springs. He made a new intake pipe and used a small motorcycle carb. I think it was a mikiuni ? It pulled 19 HP at the gocart shop and surprised a lot of people when his kids were racing.
I don't know who you are, but from your posts on the 390 cam and this one...I'm beginning to think you are either senile, confused or just a blatant B.S. spewer. I will read all your posts with that filter and suggest others do the same. By the way, my wife worked for Mickey.
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Old 12-27-2008, 07:26 PM
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Get some brass shim sheet and lay the stock head gasket on it and scribe the pattern onto the brass punch out the holes and lightly tap the new gasket with a dimpled shrinking hammer and dimple it .Install this with some head gasket silicone and it will get you some extra compression.
I have used this method of making a head gasket for some riding lawnmower engines we raced around the yard.
Also is your boat belt or chain driven? You could change the gearing or pullys possibly.
I attached a picture of the stuff you do the head gasket with try to find the thinnest brass sheet.
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Old 12-27-2008, 09:07 PM
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you can buy a lot of off the shelf parts for these engines... not as much as the 5hp briggs, but not bad. I prefer the GX200 clones- just because its fun to make power on the SUPER cheap. you can pick thos engines up from harbor frieght for $130 new, add $20 in springs, a $25 piston, a $50 cam, a $30 carb and some work bench time and you can double the power.

This forum really isn't for sideshafts- i suggest looking into gocart racing forums. the principles remain the same but the application changes some when you drop to about 4% of a typical SBC...
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Old 12-27-2008, 10:34 PM
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bus schaller

Woodz428.... Google mickey thompson schaller camshafts. or talk to bus's son about george green's projects or the old hotrod magazine about the 63 indy race. bus made a lot of HP from single cyl engines.
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Old 12-27-2008, 10:35 PM
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I remember when I was at the Briggs & Stratton tech school when the Intek
design engine came out. We stripped them down to nuts and bolts and then put them back together.
IMO I thought they looked pretty weak all around, so I wouldn't try increasing
compression if it were me. (may chunk a rod)

Cleaning up the ports to increase flow, and advancing the timing with a coil bracket should boost the power.

If you do try to shave the head, remember to check the valves to make sure
they don't hit the piston.

Check out the local mower shops, you might find a good deal on a bigger engine.
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