What Mods can be done before reliability suffers ??

[spybot]

I think these questions will be of interest to new and old engine folks

When moding an engine what can be done before they effect reliability ?

Say piston scalloping this helps the flow but it also effects the reliability.
Where as smoothing the intake flow helps reliability.

What are the pros and cons of each mod ?

High Compression Heads skimmed .30 thou
Port Matching
Intake path smoothed out.
Pistons and Rods statically blanced
Exhaust polished to mirror shine
Intake polished to dull finish
Ports chamfered
Piston and Block Scalloped

If someone could give me the pros and cons of each please.
If its a Pro why is it and if its a con what is that makes it so?

Disregarding the time factor in doing some of the above as i know some of them will take hours to complete with very little benefit if any at all hence the questions.

what kills reliability most of all ???
The above is based on a V4 but it should apply to all engine in theory.

 

[jimmbo]

If you were to take say a 90 hp crossflow and do all the changes to make it the same as the crossflow 140 hp, it should be as reliable as and have the same longevity as a 140 from the factory. Provided you didn?t cut corners in quality. Any further increases in power could affect longevity, durability, and enjoyable use of the engine.

?What kills Reliability most of all??

1) Lack of maintenance

2) Owners that tinker and modify engines without knowing/understanding how engines operate and/or what modifications are doable, and what the outcome will be

 

[spybot]

But what if you took an original 140 and done the mods listed how would they effect the motor

 

[jimmbo]

There will be a loss of longevity, and the more the engine is modified, the less suitable it will for non racing applications

 

[Scott Danforth]

As Jimmbo stated, lack of maintenance is the number one killer of reliabiliyt

here is the thing with modifying 2-strokes. "its a fine line between making power and making junk with a slip of a die-grinder" -

balancing is required with any rotating assembly, so that is a pro. this is static and dynamic balance.
polishing the exhaust helps (probably not enough to notice)
polishing the intake track is a con. you would be better off blasting the intake runners
increasing compression by machining - this usually simply makes the motor ping or have the piston contact parts (combustion chamber / piston dependent)

scalloping to free up air flow is a good thing, however one slip with the die grinder and you have junk.

mods to a 2-stroke are usually done for speed/power with longevity and reliability not being part of the concern or focus.

so of all the mods listed above, only balancing (both static and dynamic) actually would improve reliability as it will minimize the harmonic forces trying to rip the motor apart.

 

[Faztbullet]

High Compression Heads skimmed .30 thou...........Pro--higher compression lil more kick in da pants...Con--higher quality fuel needed
Port Matching........just idles better and wont see/feel any noticeable HP increase unless ported to 140 spec
Intake path smoothed out.............better idle and maybe a lil increase in bottom end
Pistons and Rods statically blanced.....smoother motor...no HP increase also need crank balanced if above 6500..
Exhaust polished to mirror shine.......waste of time IMO
Intake polished to dull finish.......you want it bead blasted not polished...you want fuel to tumble and stay atomized
Ports chamfered....rings wont catch
Piston and Block Scalloped ........only if your going to spin it above 6500rpm...reliability going down as skirt is life of piston
You need to decide that (A) Im going to make a stock 140 with cleaned up block or (B) I going to build race motor as some of these mods are not for stock engines.....

 

[Texas Prowler]

High Compression Heads skimmed .30 thou...........Pro--higher compression lil more kick in da pants...Con--higher quality fuel needed
Port Matching........just idles better and wont see/feel any noticeable HP increase unless ported to 140 spec
Intake path smoothed out.............better idle and maybe a lil increase in bottom end
Pistons and Rods statically blanced.....smoother motor...no HP increase also need crank balanced if above 6500..
Exhaust polished to mirror shine.......waste of time IMO
Intake polished to dull finish.......you want it bead blasted not polished...you want fuel to tumble and stay atomized
Ports chamfered....rings wont catch
Piston and Block Scalloped ........only if your going to spin it above 6500rpm...reliability going down as skirt is life of piston
You need to decide that (A) Im going to make a stock 140 with cleaned up block or (B) I going to build race motor as some of these mods are not for stock engines.....

This dude^^^Rocks!

 

[Chinewalker]

When balancing moving parts, you're basically getting the motor closer to design specs and not actually gaining anything by modification. On our stock racing motors, we might acquire as many pistons and rods as possible, then weigh them against each other to choose the ones that are closest in mass. Rods that weigh the same can then still be out of balance if one has more mass at the wrist pin than the crank end, so you choose the ones that match both ways. On a stock motor, you mix and match the closest parts as you're not allowed to remove material to achieve that balance.