Heymow - Lawnmower Racing Forum

Engine Help => Briggs OHV & Vanguard => Topic started by: cable1981 on July 02, 2017, 11:28:10 am

Title: Briggs 31 Non Avs VS Avs Pistons
Post by: cable1981 on July 02, 2017, 11:28:10 am

I'm trying to find a piston for a Briggs 31 non avs, pn 692273. It has been right next to impossible to find it, and was told by Briggs that its obsolete and no longer available.
Question is, can i put in a piston from an avs engine, pn 796173??
They have the same bore, only difference i can find is the avs/non avs

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: nic_hayes on July 02, 2017, 06:58:37 pm

Use this .020 over piston,

http://eccarburetors.com/estore/796173-briggs-model-31-avs-020-piston-assembly.html?category_id=420

With this ARC billet rod,

http://eccarburetors.com/estore/6280-arc-briggs-model-28-billet-rod.html?category_id=412

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: nic_hayes on July 02, 2017, 07:02:47 pm

Just remember you will need to have your block bored .020 over.

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: cable1981 on July 02, 2017, 07:12:42 pm

Will that piston work without using the billet rod? Our rules state "OEM connecting rods must be used"

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: nic_hayes on July 02, 2017, 08:15:36 pm

Is your original piston short with the thin rings like the one in the link? If it is they yes it will work. If it's the old style big piston with wide rings then no.

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: cable1981 on July 02, 2017, 08:39:24 pm

I want to say it's got thick rings on it, they measure roughly 1/16 of an inch each

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: cable1981 on July 02, 2017, 08:48:05 pm

It also only has 3 rings where it's showing 4

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: chavez on July 02, 2017, 11:09:35 pm

Just use the avs rod and piston together.  The avs rod is a little better I think.  It's what the rest of the crew at Puk run in mod.

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: cable1981 on July 03, 2017, 11:12:48 am

Thanks the the help guys. Now doing the 020 bore, and cleaning up the head, is that gonna change things enough to where I'm gonna have to make a timing change?

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: nic_hayes on July 03, 2017, 12:08:53 pm

Quote from: cable1981 on July 03, 2017, 11:12:48 am

Thanks the the help guys. Now doing the 020 bore, and cleaning up the head, is that gonna change things enough to where I'm gonna have to make a timing change?

No.

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: cable1981 on July 03, 2017, 02:40:41 pm

Thanks guys for all the help it's much appreciated

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: cable1981 on July 15, 2017, 08:22:13 am

Got the block back, put everything together, and it will not fire. I've checked recheck and checked again, but still seems like it's not getting what it needs at the right time. Any thoughts?

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: cable1981 on July 15, 2017, 08:30:40 am

I used the avs piston with the avs rod, do I need to find an avs camshaft as well?

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: outlaw#6 on July 15, 2017, 12:22:54 pm

No the 31 non avs cam is fine, check your timing though. Flywheel in the right position? Camshaft lined up properly?

Do you have good compression with the new rod/piston/bore combination?

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: cable1981 on July 15, 2017, 11:52:41 pm

its got good compression. however a whole day working on it, the newest "wth" was fuel coming out the exhaust pipe as i tried turning the engine over.

Title: Re: Briggs 31 Non Avs VS Avs Pistons
Post by: Tom Price on July 17, 2017, 11:06:19 am

Check your timing