Raise Compression and advance timing

[robert0762]

I am going to bump up my compression some this year and have a few questions. i have a HJR mx hardcore port job 4 mill crank 28 pwks and pc pipes. I have heard that going to high on comp will hinder your topend. So I am wondering what is safe to run as far as comp numbers go. I am planning on running cam 2 110 octane mixed 50/50 with 93 pump gas and caster at 32:1. I dont know what my static numbers are now but i do knoe that the ex port is 28mm below deck.

 

As far as the timimg goes i want to advance as much as poss also but dont want to much that it hurts topend performance. I am thinkin about gettin a dyna ign and getting someone to program me a custom curve. advance as much as i can for low and mid then pull it back on top. But if i dont do that will 6 deg be too much/

[bbcmudtruck]

Generally stock cylinder motors afe run between 4-6 degrees. You'll just have to play with it and see where it likes it best. If your crank is welded, then I wouldn't worry about adding a little compression. I usually run around 180psi without issues. Be sure to run the correct amount of octane woth higher compression and more timing.

[252wheelieking]

Generally stock cylinder motors afe run between 4-6 degrees. You'll just have to play with it and see where it likes it best. If your crank is welded, then I wouldn't worry about adding a little compression. I usually run around 180psi without issues. Be sure to run the correct amount of octane woth higher compression and more timing.

 

With a 180psi. do you run straight race fuel or race fuel/pump gas mixed 50/50?

What timing do your engine reacts better to with your octane choice?

Edited February 9, 2011 by 252wheelieking

[robert0762]

Do I need to rejet when I raise my compression?

[06specialedition]

I run +5 timing and 19cc domes on my stock stroke with no problems.