Export thread

Oil clearance

#1

Stryped

Stryped

I have a 27 hp Briggs v twin with aluminum rods. I broke a rod so I am rebuilding it. It goes to my lawn mower.
Can you tell me what to look for in terms of clearance between my rod and crank journal? If the clearance is too much, can I mill the rod halves to make the large rod journal smaller if that makes sense? Could it be done with sand paper and plate glass like you use to flatten a cylinder head surface? Thanks for your help!


#2

S

slomo

This one of those ultra fast deck removed mud bogger mowers?


#3

Scrubcadet10

Scrubcadet10

i would get your model type and code numbers, contact briggs, and ask for the clearance between the Rod big end and crankshaft journal, if they give you a spec, buy some plastigauge and go to work...


#4

Stryped

Stryped

slomo said:
This one of those ultra fast deck removed mud bogger mowers?
Click to expand...
No it’s to my John Deere zero turn


#5

Stryped

Stryped

Scrubcadet10 said:
i would get your model type and code numbers, contact briggs, and ask for the clearance between the Rod big end and crankshaft journal, if they give you a spec, buy some plastigauge and go to work...
Click to expand...
I have no clue who to contact at Briggs.
I have heard a rule of thumb is .001 times the crank normal diameter but have no clue if that is right.


#6

sgkent

sgkent

it is for pressure systems for the street. Don't know on splash systems. You can get the measurement by subtracting the crank journal spec from the rod dimension spec. If one starts sanding, do not pinch the journal or a whole world of hurt will happen. I used to resize 50 - 100 automotive rods a week for many years.


#7

Stryped

Stryped

sgkent said:
it is for pressure systems for the street. Don't know on splash systems. You can get the measurement by subtracting the crank journal spec from the rod dimension spec. If one starts sanding, do not pinch the journal or a whole world of hurt will happen. I used to resize 50 - 100 automotive rods a week for many years.
Click to expand...
What do you mean pinch the journal?


#8

Scrubcadet10

Scrubcadet10

Stryped said:
I have no clue who to contact at Briggs.
I have heard a rule of thumb is .001 times the crank normal diameter but have no clue if that is right.
Click to expand...
shop.briggsandstratton.com

Contact Us

Contact Page
shop.briggsandstratton.com shop.briggsandstratton.com


#9

VRR.DYNDNS>BIZ

VRR.DYNDNS>BIZ

Stryped said:
No it’s to my John Deere zero turn
Click to expand...
Journal and crank specs exist for standard. No current engines under $1500 or so have specs for regrind of journal and a rod to match by B&S as far as I know. Part cost is usually less than regrinding journal and specs for regrinding are seldom properly followed. Buy the parts or short block so you don't have to do it again. In addition, compression Top dead center will change if parts not proper and head to piston contact is very possible. Never tighten a rod cap to close the gap period - think of the out of round condition you create. Some times you can clean any transferred material off the crank with tender care and measure it for spec pass and reuse - this a shop will seldom do as the time cost equals a crank. Make sure to check journal in several clock positions. More wear will be found at top dead center.


#10

StarTech

StarTech

Only milling on rod journals will make the clearances worst otherwords the only way to make the rods to fit tighter is make their hole smaller not larger.


#11

sgkent

sgkent

I used to size connecting rods for a living. When the rod halves are sanded, the edges also come in closer. If you think of a clock, think of the pairs 8 and 2, and also 10 and 4. If the rod is not 100 percent centered when it was honed at the factory, 8-2 or 10-4 can be closer. Example, 10-4 might be a shorter distance than 8-2 if the rod and cap were slightly off center when honed but it could be within an acceptable distance at that time. If you start bringing the 12-6 dimension together to make the hole smaller then that 10-4 example distance can change enough to pinch the crankshaft so the rod seizes. That measurement could have been fine but you changed it after the factory honed the big end of the rod. We used to measure 360 degrees of the big end as we resized it to not get caught in that rabbit trap.

Attachments





#12

Stryped

Stryped

sgkent said:
I used to size connecting rods for a living. When the rod halves are sanded, the edges also come in closer. If you think of a clock, think of the pairs 8 and 2, and also 10 and 4. If the rod is not 100 percent centered when it was honed at the factory, 8-2 or 10-4 can be closer. Example, 10-4 might be a shorter distance than 8-2 if the rod and cap were slightly off center when honed but it could be within an acceptable distance at that time. If you start bringing the 12-6 dimension together to make the hole smaller then that 10-4 example distance can change enough to pinch the crankshaft so the rod seizes. That measurement could have been fine but you changed it after the factory honed the big end of the rod. We used to measure 360 degrees of the big end as we resized it to not get caught in that rabbit trap.
Click to expand...
Makes sense. But what if you took equal number of “strokes” on sandpaper on both halves of the rod?


#13

sgkent

sgkent

Stryped said:
Makes sense. But what if you took equal number of “strokes” on sandpaper on both halves of the rod?
Click to expand...
you missed the point. It isn't just the top to bottom clearance you are changing but also side to side ESPECIALLY if the cap is offset, which you can't measure without very expensive devices like one of these
https://cdn.shopify.com/s/files/1/1418/7084/products/AG-300.jpg


Footer Links 1

Top