Engine rebuilld vs replace

[AirJunky]

Originally Posted by scottyb

There are hidden costs in the clone engine swaps or any BB conversion...... stock rebuild is definitely the most economical thing you can do to revitalize the cart

Would be interesting to see actual numbers for each situation. Even if their ballpark figures.

Also, how much speed/torque are you seeing from a rebuild?

[CC-John]

Originally Posted by BLACK DEATH

Scott, could you really tell that much of a difference in the flatty with more compression?

A mild boost in compression will really wake them old flattys up!! Most flattys only have a 5 or 6:1 compression ratio..

Back when I was 6 or 7 years old, I had a live-axle, go-kart with a 3.5 HP Tecumshit flathead on it.. With the help of my dad, we milled the head, removed the governor, retarded the cam one tooth and ground off the compression relief, did some mild porting & relieving*, fitted a 5 horse carburetor, and a straight tuned pipe on the exhaust.. It went from barely being able to get out of it's own way at 15 MPH, to a 50 MPH screamer that would boil both rear tires from a dead stop for as long as you wanted to stand on it.. The engine looked like a stock engine from the outside, still had all the 3.5 HP decals on it.. I used to annihilate the other kids in the neighborhood with 5 HP Briggs on their karts.. Having a "sleeper" is soooo much fun!!!

(*) Relieving is a trick from the days of the old flathead Ford V8's.. You basically mill a shallow trough in the deck surface of the block, from the valve seats to the cylinder bore.. This improves the engine's breathing at high RPM's when the head is milled to raise compression..

[AirJunky]

Originally Posted by CC-John

It went from barely being able to get out of it's own way at 15 MPH, to a 50 MPH screamer that would boil both rear tires from a dead stop for as long as you wanted to stand on it..

Hehe, I'm all over that.....
Would be cool to see if an old Marathon could actually wake up that much.

[scottyb]

Originally Posted by BLACK DEATH

Scott, could you really tell that much of a difference in the flatty with more compression?

Yes It made a big difference in how it pulled. It made more power all that you could feel from the seat of your pants

[BLACK DEATH]

The seat of your pants is always the best way to tell, thanks