Heymow - Lawnmower Racing Forum

Engine Help => Briggs Flathead => Topic started by: Wheelinhorse on January 05, 2022, 07:20:26 am

Title: Full 46ci pressure lube oppy build thread- now with billet goodies
Post by: Wheelinhorse on January 05, 2022, 07:20:26 am
Look, I know oppys are now dinosaurs for you racers, but for us offroad tractor guys its a cheap, torquey option that works very well for what we do.
Been acquiring parts and will be starting a build soon. Complete 46CI pressure lube vertical engine, a horizontal cam cover, pump, sump, etc..  and recently scored an ARC wheel, rods, AVS pistons, and Precision 212alt cam. Yes it will be flipped horizontal. Intake is an early 2 piece, massaged, 1" tall adapter and a 27hp Kohler command 'pumper' carb on top, and 2:1 header, all are currently on the stock internal 18hp powering it right now. They both work very well- the carb made a day and night difference in power.
Since im much more concerned with low/midrange grunt than a top end screamer, how do you feel about this cam versus the stock 46ci? I have the ability to knock some base circle off the stocker, as well as all the equipment necessary to play with porting, decking/milling, valves, seats and angles, etc...
How about trading a bit of airflow for a boost in compression, a big oppy no no....
Come on, most of these things arent even raced anymore, you guys can give me some direction without giving away secrets cant ya? Ha.
Title: Re: Full 46ci pressure lube oppy build thread- now with billet goodies
Post by: BIG AL 202 on January 06, 2022, 02:45:07 pm
You never mentioned boring to fit 31ci pistons. There is no substation for cubic inches. I believe it will make about 50ci. The cam grinder to use it Tim Isky. He's been grinding oppy cams for a long time. You are on the right track.
Title: Re: Full 46ci pressure lube oppy build thread- now with billet goodies
Post by: Wheelinhorse on January 07, 2022, 06:29:19 am
Had no idea these blocks could be taken out that far, if at all. Is there enough meat?
Title: Re: Full 46ci pressure lube oppy build thread- now with billet goodies
Post by: BIG AL 202 on January 07, 2022, 05:27:06 pm
YES!
Title: Re: Full 46ci pressure lube oppy build thread- now with billet goodies
Post by: Wheelinhorse on January 10, 2022, 07:53:07 am
Uh oh. I have a Kwik Way boring bar and sunnen hone in the back room, some stuff I never got rid of when I closed the speed shop. This could get silly!
Title: Re: Full 46ci pressure lube oppy build thread- now with billet goodies
Post by: BIG AL 202 on January 11, 2022, 08:27:13 pm
NOW THAT"S WHAT WE LIKE TO HEAR!!
Title: Re: Full 46ci pressure lube oppy build thread- now with billet goodies
Post by: Wheelinhorse on January 20, 2022, 09:47:45 am
I built a crude but functional flowbench and am learning a lot. Although I cannot get actual flow numbers, I can measure gains and losses and am pretty surprised at some of the findings so far.
Title: Re: Full 46ci pressure lube oppy build thread- now with billet goodies
Post by: PJG56 on January 24, 2022, 03:36:55 pm
Had no idea these blocks could be taken out that far, if at all. Is there enough meat?
In order to go to 31ci bore(3.5625") youll have to sleeve the block.