Topic: tips for most power in a stock rebuild

[dang107]

the class I race has a stock eng. rule were allowed to remove gov. and change air cleaner and exh. I've have motor 101 and I'm wondering if there are any tips for getting the most power out of a stock rebuild. considering the vid is directed at building a race bullet I realize I can still use alot of the info but is there anything that stands out for a stocker. also what should my target rpm. be for the most torque? any help will be appriecated.

[mowmaster]

I am assuming that a good Port & Polish is out of the picture?
Is that all the rules, or give us the specifics.
Andrew

[dang107]

replace air cleaner remove gov. and change exh. thats about it

[mowmaster]

have a high-flowing exhaust, make a large air cleaner that will scoop air (so face towards the front). And personnaly, i would not completely remove the governer, i would adjust it untill it what you need.
Andrew

[Squidd]

also what should my target rpm. be for the most torque? any help will be appriecated.

For a stock cam. right around 3650-3700 rpm so you might as well leave the govener in and tweak it slightly.....

[mowdak1]

You really aren't going to gain a lot by removing the governor. Most torque out of that engine is more than likely going to be seen at your designed governed speed. Not that you can't turn it faster, and get a few more mph out of it, but you don't need a great deal of torque when you're crowding top speed. Torque is going to be needed coming out of the corner, and the air and fuel flow on a stock carb/stock cam aren't going to allow you to gain a great deal more than you'll find at 3650 rpms.

If allowed you could bore it .030 over using a stock Briggs .030 over piston, and that would get you a little more torque, but you won't gain much there. Aside from that getting the steering, weight distribution, and tire pressures dialed in and reducing rolling resistance so that it handles better than anything else on the track, and rolls with as little resistance as possible is going to buy you more than anything.

It's all about finding the little things and making the most of them all. Make the most of a sack full of little things and they become a big thing!

[dang107]

sorry about not responding I went to france for a race and wasnt able to read your responses so first thing I took a threaded exh and bottomed in to the exh port and matted to port so there wasn't a step then I cut it off flush to head and buil the exh aproximately .200 larger than outlet to help with reversion. on the intake side I made a new intake similar to a veloicty stack that mounts the air cleaner in front of the eng I made heat shields for the carb to block exh heat from the intake and float bowl as well as the fuel tank I did remove the gov. on the eng. I m using right now but I can still use it on the eng. i'm building I have a tach and cyl. head temp on the mower right now and have it geared to run about 4500 rpm after 4200 it doesn't seem to pull any more I geared for this rpm because I race on a oval but I haven't tryed lower rpm do you think I should?  also what do you mean buy tweaking the gov.? could you explain alittle more? also I had a couple of 12hp carbs so I decided to mod one just to see if there were any gains I port matched the carb to air cleaner intake making it round instead of D shaped tha poished the bore and cleaned up the venturi removed the choke and mod the throttle plate screws and shaft. I opend the jet  .010  and cleand the burrs out of the intake and matched it to the head when i put it on the mower it was a huge difference it reved faster  and seemed to make more power than my 12.5 carb. after all the rambling I'm wondering if there is any tricks I could do to the 12.5 carb to make it better without mod. so much thanks for taking the time to read such along post but please tell me what you guys think considering that my rules say eng must have stock internals I don't know if the carb falls into the grey area of the rules

[bountyhunter]

 Hey Where you running the tractor at I live in MI to and would like to see them run.

[dang107]

charlotte mi, maple rapids mi ( which is the stock eng class. it's good racing cause you have to be fast with the chassis not just spend alot of cash on a race bullet to be fast) and I believe theres arace in morris mi. next weekend

[bountyhunter]

Found Maple rapids site am going sunday what ## are you?? have fun good luck!!

[Don Gienger]

Well Stock Motor Class
While most people think all I do is USLMRA motors I do build anything. I mean I have one or two motors in the "Stock Motor Class" in other parts of the country that are kicking butt.

There are lots of little things you can do legally to a motor to make it faster. My DVD does tell most. But you are face with a cam, timing and carb that are stuck at 3,650 programming. I mean the motor was only designed for this rpm band so you are SC in a word.
Can you use timing keys?
Can you remove the choke and or do anything to the carb?
How do they check for stock motor?
Heck you could bore the motor but Briggs only makes .020 over piston anymore. If you are to bore the motor why not go 31 CID?
So OK that is a little extreme.
What about ARC Rod? What about long rod Technoligy? I mean put an ARC rod in and shorty piston. The motor will breath totally different in a better way then a short rod deal. Better rod and lighter piston.
Porting helps but what about carb. Remove choke? Make the main jet bigger?
Timing? Stock timing is at 17 degrees. A #4 or #6 Key will work well.
In it's true stock for with little mods the motor is only going to make power to 4,200 rpms and then fall off and end at 5,200 maybe 5,500 rpms. That is seat of the pants testing by the way.
Help that helps.
Don

[dang107]

well I appreciate the response first i'm #107 stop by and say Hi. second some of the rules are pretty clear no offset keys and no internal mods. so I assumed no porting and no changing of parts head and so forth I planned on asking about the rod with tech officials simply for reliability. my goal is to build a strong reliable stocker something I can run for a season or two. I do think it's fare to say boring the block would be okay because not many people are willing or have the means to buy a new motor when the rings or cyl wear. I get the impression from the rules a rebuild is alright but a purpose built motor isn't. from watching the vid. there was a ton of useful info. but what about the guys using bolt on parts? for instance optimum exh dia. and length? I threaded in a stock exh. cut it flush and made my exh aproximatly .150 to .200 bigger thinking about what a car eng. would want I did remove the choke but only for safety with that cheap plastic and only those little tabs holding the butterfly in I don't want that coming apart and hanging the throttle If it was built diff. I probably would have left it. so what about internal clearances ring end gap and so forth? would you use the same spec for a higher Rpm eng? thanks for taking the time to answer such a long post but I bet theres other guys who would benefit.