I want to add Automatic compression releases to my bike and I saw SE ACR heads. I wonder how they perform.Do they increase power like ported heads? Is it better to have these heads or install ACR to standard heads and port and polish? My bike's mods are in my sig. Thanks in advance

 

Why do you think you need compression releases?

Short answer is to add CRs to your heads. The ACR heads have 95" combustion chambers and large valves. Long answer is that while you have the heads off, check into cam upgrades and have your heads ported and setup for the new cams.

 

I've done a couple TMan builds with ACR's. We machined the ACR holes & then sent the otherwise stock heads to TMan for him to do his magic.

Where I was once "not on board" with the ACR's.... I have changed my opinion & would even consider using them on my own bikes.

 

Those heads will suck the bottom out of the torque curve on that 103", and with the kidney shaped chamber design, the edge of the piston dome will have to be machined for clearence, once surfaced to establish the correct cc's.
Scott

 

Most of your reputable builders now can machine for the ACRs. I sent a set of stock heads to Headquarters, had them machine for the ACRs and work their other majic on the heads. Bike stock was a 103 with ACRs, but I want to keep the heads for a future project. I have not installed ACRs on any of the builds that I have done for others as I was leery of them, much the same as PhilM, but firgured to give them a fair shot on my personal bike. They work great and I am now a believer. Turn the key, hit the switch , and she fires.

Buy some take off heads or have your own heads redone, you will be better off in the long run.

 

Thanks for the replies. When I have my heads ported do I have to change pistons also? I don't want more compression. This will be a dumb question but can you please tell me what would be the main advantage of porting heads if the compression ratio stays the same?