Heymow - Lawnmower Racing Forum

Engine Help => Briggs Flathead => Topic started by: laurw1 on May 15, 2018, 10:17:17 am

Title: Are All Opposed Twin Blocks The Same?
Post by: laurw1 on May 15, 2018, 10:17:17 am
Hey so I was wondering if say the blocks for the 40, 42, and 46CI blocks are all the same. I am asking because I have a 42CI 18HP opposed twin with a wrecked block, and a 40CI 16HP opposed twin thats all good, so I was wondering if I could swap the crank and rods from the 18HP and put them into the 16HP without having to mill the pistons?
Title: Re: Are All Opposed Twin Blocks The Same?
Post by: PJG56 on May 15, 2018, 11:44:36 am
40ci & 42ci blocks are basically the same so you can swap crank and rods,with no issues
Title: Re: Are All Opposed Twin Blocks The Same?
Post by: laurw1 on May 15, 2018, 12:53:50 pm
Thank you, do you know the differences the 46CI block has? I'm curious now
Title: Re: Are All Opposed Twin Blocks The Same?
Post by: PJG56 on May 15, 2018, 04:18:27 pm
On the long stroke 46 there are cutouts in the block for the rods to clear,thats the only difference.
on the short stroke 46 the block is the same as the 42 and uses its crank,but has a 3.5625 bore instead of the standard bore of the 40,42& 46 of 3.4375

the 40ci has 2.19 stroke,42 has 2.28 stroke and long stroke 46 has 2.46 stroke
big bore short stroke is 2.28 same as 42ci
Title: Re: Are All Opposed Twin Blocks The Same?
Post by: BIG AL 202 on May 16, 2018, 01:33:14 pm
They also had pressure lube blocks and they did make a big bore block. The big bore block used a 42ci crank to keep it 46ci. The horizontal and vertical blocks are different but alot of the internals interchange. I have heard of big and small valve blocks but have not seen any.
Title: Re: Are All Opposed Twin Blocks The Same?
Post by: rotten ron on May 16, 2018, 11:38:00 pm
Where is Rooster? He knows all about these blocks
Title: Re: Are All Opposed Twin Blocks The Same?
Post by: cycloneracer on May 17, 2018, 01:13:43 pm
Rooster hasn’t been here since 2014........