VALVE GUIDE REPLACEMENT BRIGGS FLATHEAD

A SIMPLE PLAN

A SIMPLE PLAN

Member
GOT BRIGGS, EX VALVE GUIDE SHOT. GOT NEW GUIDES COMING. I KEEP SEEING that we pull the old guides out of engine with a puller/bolt. i threaded in 5/16" tap for fun... i dont see how /that there is a an actual valve guide pressed in the cheap throwaway engine? it looks like the "valve guide" is just a hole drilled in the alum block ?

do we drill a hole thru the alum the size of the OD of the new guide, whatever size that is, and then knock the new guide in the block? with expensive BRIGGS valve guide driver $30 for a tool... i will use ONCE? all it is is a 1/4" OD rod that has the end machined 1/4" out of 1/2" or whatever size hard steel rod? what size drill bit do i need to use to drill out the "valve guide" (alum in the block) to fit the new bronze/brass valve guide?

simplest thing in the world but im not spending $100 on tools to drill out/drive in $5 valve guide in the block. super glue the guide in the block? red thread lock. it cant be an extreme pressure application if the valve is a little loose and has OIL on it when installed. the reamer... $30 for the valve guide? that should be the right size for 1/4" valve stem out of the box. so.... drill out old valve guide with what size bit for the new valve guide to fit in the block? 231348 is the valve guide's #
 
nno brazing rod... no torch that gets that hot. the guide is wasted from cocked spring? it needs a new guide. how to drill the hole out for new guide. size drill bit?
 
A SIMPLE PLAN said:
GOT BRIGGS, EX VALVE GUIDE SHOT. GOT NEW GUIDES COMING. I KEEP SEEING that we pull the old guides out of engine with a puller/bolt. i threaded in 5/16" tap for fun... i dont see how /that there is a an actual valve guide pressed in the cheap throwaway engine? it looks like the "valve guide" is just a hole drilled in the alum block ?

do we drill a hole thru the alum the size of the OD of the new guide, whatever size that is, and then knock the new guide in the block? with expensive BRIGGS valve guide driver $30 for a tool... i will use ONCE? all it is is a 1/4" OD rod that has the end machined 1/4" out of 1/2" or whatever size hard steel rod? what size drill bit do i need to use to drill out the "valve guide" (alum in the block) to fit the new bronze/brass valve guide?

simplest thing in the world but im not spending $100 on tools to drill out/drive in $5 valve guide in the block. super glue the guide in the block? red thread lock. it cant be an extreme pressure application if the valve is a little loose and has OIL on it when installed. the reamer... $30 for the valve guide? that should be the right size for 1/4" valve stem out of the box. so.... drill out old valve guide with what size bit for the new valve guide to fit in the block? 231348 is the valve guide's #
Click to expand...
This is not a job for most racers without the proper tools, knowledge, and experience.
You can pull the old guide out, or simply machine it out.
If you tapped the aluminum, that is incorrect. Some blocks do not have guides installed on the intake side. All blocks have them on the exhaust side. By tapping the aluminum on the intake side with a 5/16" tap, you probably ruined the block. How did you center the tap to make sure that it was straight and concentric with the valve seat? That takes a centering guide or a mill.
Always use straight flute reamers for valve guide installation. A drill bit cannot possibly make the correct finish and interference fit. Use a hone to finish the ID to recc'd clearance.
Likely if you take it (or send it off) to someone to have repaired, it will be even more costly now to fix your mistake and likely need to replace the seat at the same time.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
FWIW, we use longer valve guides that are also made of a better material so you can run tighter clearance for greater valve stability, less valve seat bounce, and more power as a result.
 
Ask your local small engine repair shop . If karts are raced in your area you will not be the first racer they've dealt with
 
are you threading the guide to extract it? in the old days there was a tool you could run through the guide that would knurl and resize the guide. I would not recommend it to last a long time but a possible band aid
 
A SIMPLE PLAN said:
GOT BRIGGS, EX VALVE GUIDE SHOT. GOT NEW GUIDES COMING. I KEEP SEEING that we pull the old guides out of engine with a puller/bolt. i threaded in 5/16" tap for fun... i dont see how /that there is a an actual valve guide pressed in the cheap throwaway engine? it looks like the "valve guide" is just a hole drilled in the alum block ?

do we drill a hole thru the alum the size of the OD of the new guide, whatever size that is, and then knock the new guide in the block? with expensive BRIGGS valve guide driver $30 for a tool... i will use ONCE? all it is is a 1/4" OD rod that has the end machined 1/4" out of 1/2" or whatever size hard steel rod? what size drill bit do i need to use to drill out the "valve guide" (alum in the block) to fit the new bronze/brass valve guide?

simplest thing in the world but im not spending $100 on tools to drill out/drive in $5 valve guide in the block. super glue the guide in the block? red thread lock. it cant be an extreme pressure application if the valve is a little loose and has OIL on it when installed. the reamer... $30 for the valve guide? that should be the right size for 1/4" valve stem out of the box. so.... drill out old valve guide with what size bit for the new valve guide to fit in the block? 231348 is the valve guide's #
Click to expand...
Let's all be glad this fella ain't no brain surgeon! Holy smokes guy, while your at it might as Waller out side cover hole and replace it with some jb weld just to be extra safe.😉
 
J'-remy said:
band aid
Click to expand...
Legend has it that is the OG's middle name? It's hard for average folks to wrap their heads around just how much perfection actually goes in to building The Flathead. And that is why it will always be a respected relic in my shop. I am gonna have nightmares about this horror story surgery and its rabid surgeon for at least a couple nights now. So thanks lol.
 
It's not a FORMULA1 engine or over the road diesel meant to last a million miles. Just a little engine to play with. It will most likely outlive me with good oil n moderate use
 
that was the idea of 5/16 tap... to knurl the guide... still looooose. but the guide is so loose, doesnt matter. how did i center it... the tap centered itself ;) with pilot hole... the original guide that is toast from cocked spring? 7.75-8mm drill bit is abt the same OD as the bronze guide .310"... the 7.75mm is .3051181" .... 7.8mm bit is 0.307087" still a touch smaller than the .310 OD of the valve guide. so ... close enuf for me
 
Drill bits do not make round holes is the first reason.
Second is that drilled hole can be larger than body of bit.

As stated, a reamer is the correct tool for the job. A guide is inserted in the valve seat to keep tool aligned. Otherwise, valve will not be able seal on the seat.

Before you completely ruin your block, drill a hole in a piece of aluminum to see if you will get acceptable results. Try to replicate exactly what you will be doing in your block.
Keep in mind that the guide must remain in place after the engine heats up.

Proper tools are an investment. Getting the job done correctly is the reason different tools exist.
Not only will you block be ruined, but also your new guide wanted. Any other work done to the block is also wasted.
 
A SIMPLE PLAN said:
that was the idea of 5/16 tap... to knurl the guide... still looooose. but the guide is so loose, doesnt matter. how did i center it... the tap centered itself ;) with pilot hole... the original guide that is toast from cocked spring? 7.75-8mm drill bit is abt the same OD as the bronze guide .310"... the 7.75mm is .3051181" .... 7.8mm bit is 0.307087" still a touch smaller than the .310 OD of the valve guide. so ... close enuf for me
Click to expand...
I thought you said that the guide was "wasted?"
So then you tapped a 1/4" valve bore with a 5/16" tap to try to knurl it?
Now you are trying to drill to fit a .310" guide in a .305" or .307" hole?
And you'll finish ream the guide with what size drill bit?
All without centering the guide in the seat?

When you get done with your experiment, install the new valve and shine a light in the port and let us know if you see light around the face of the valve and seat.

You're right, this is not an F1 engine or million mile diesel engine.
I'm all for the DIY'er, but you sir, are in way over your head and capabilities.
 
A SIMPLE PLAN said:
that was the idea of 5/16 tap... to knurl the guide... still looooose. but the guide is so loose, doesnt matter. how did i center it... the tap centered itself ;) with pilot hole... the original guide that is toast from cocked spring? 7.75-8mm drill bit is abt the same OD as the bronze guide .310"... the 7.75mm is .3051181" .... 7.8mm bit is 0.307087" still a touch smaller than the .310 OD of the valve guide. so ... close enuf for me
Click to expand...
Do what you want, hopefully others with limited experience will not be influenced to try the same things and ruin a racing engine. Why post if you have no intent to follow recommendations?
 
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Gotta try it. If hole drilled thro valve guide is close to OD of new valve guide a little tapping to get valve guide in shd do it. 7.85mm drill bit is closer to .310" . but those bits not ez to come by or cheap. So 7.8mm will have to do. Bit should follow old guide path close enuf. We shall see. Machine shop closed. The guide fits the new valve fine as is as long as don't collapse thin walled guide driving it home shd be ok. Time will tell. I'm not scared. High rotary speed n low bit weight n ream hole til it's just so
 
You better take that engine to your local small engine repair shop and ask them to put the guide in. They should be able to do that for fairly cheap and not destroy the engine like you are about to do.
 
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