High Compression

[calemoses]

mate use to run a ke30 with a 2k in speed way, he says he use to shave 40mm of the head! he said youll need bigger valves better/ dual carbs and a big air intake, then go lol, anyone tried this? how long would it last he said 2k's hold up better than the 3k or 5k

[Taz_Rx]

40mm would be half the head....maybe 40 thou?

Have a read of "how to build a tough k motor" in the faq ;)

[LittleRedSpirit]

Nah his mate said take 40mm off. I say go for it. Let us know how it runs.

[Trev]

Nah his mate said take 40mm off. I say go for it. Let us know how it runs.

 

Ha

[ke70dave]

40mm hey.

 

Must be one of those new fangled valveless engines. They fast.

 

Persuming he meant 40thou, thast 1.016 mm.

 

I dunno if thats alot or not, but depends how many times its been skimmed in its life. A 40yr old (2k must be close to 50yr old?!?) head may have been skimmed twice in its life, so its possible you may have already removed 0.5mm already.

 

Heres the link to that tech article

 

http://www.rollaclub.com/wiki/index.php?title=Tech:Engine/K_Series/How_to_build_a_tough_K_motor

[altezzaclub]

mate use to run a ke30 with a 2k in speed way,

 

He needed it because the cam he would be using was so pathetic at filling the cylinders over most of the rev range so it had to compress the hell out of the mixture to make it fire.

 

The hotter the cam you use, the more compression you need to get it to go at anywhere except at its peak rev range.

 

Using high compression with a milder cam will give detonation problems and make it harder to turn over on a starter motor. They reckon a 4% power increase with each full compression number lift, but obviously it will give the rings and bore a hard time, as well as piston crowns and small end bearings.

 

Boring it wold be a better way to raise the compression, that saves any trouble about valves hitting the head. Then you could use bigger valves and a wilder cam with more lift.

[calemoses]

the head or block or something sure that's what he said, but you know how mesurements change over time lol

[coln72]

With some of the fuels they used to run in speedway, that sort of compression may of been realistic. I can't remember what it was now, but an old speedway racer was saying he had to add castor oil into his fuel or it would wear out his rings in a meeting.....

[Trev]

 

I dunno if thats alot or not, but depends how many times its been skimmed in its life. A 40yr old (2k must be close to 50yr old?!?) head may have been skimmed twice in its life, so its possible you may have already removed 0.5mm already.

 

Heres the link to that tech article

 

http://www.rollaclub.com/wiki/index.php?title=Tech:Engine/K_Series/How_to_build_a_tough_K_motor

 

I only took 65 off my L20 head :P

[Redwarf]

I've had .125 off one. Had to mill new screwdriver notches back into the head.

[Trev]

I've had .125 off one. Had to mill new screwdriver notches back into the head.

 

I stopped as I didn't have any cam support shims to bring the chain tension back up.

[altezzaclub]

I stopped as I didn't have any cam support shims to bring the chain tension back up.

 

On the L16 we bought a half-link for the chain.. The nice thing is, with OHC you don't lose the rocker ratio.

 

Still, I'd go for the largest bore, shortest stroke and smallest head to get high compression without skimming it to death.

[Trev]

 

 

On the L16 we bought a half-link for the chain.. The nice thing is, with OHC you don't lose the rocker ratio.

 

Still, I'd go for the largest bore, shortest stroke and smallest head to get high compression without skimming it to death.

 

Could not have said it better actually.

 

Only did it to mine as the head was off after the gasket blew.

[parrot]

I had a big compression L20B once. Not sure how much was off as I bought it like that, but it was a lot.

 

They got around chain tension by tapping a new hole in the front of the block to locate the chain slide further inward. That worked great, until I put the head back on with a spacer and put the slide back in it's original holes without noticing the newly tapped hole. Unfortunately the bolt hole they had tapped went straight into the water jacket, and all the water pumped out of the jacket and into the sump.