Going to swap out gear cams tomorrow and install a set of HQ39g cams. Compression ratio should be around 10:1. I have seen some say these run best at 10.5:1 and others say they had great results at 10:1. I have read a lot of good things, but have seen very few Dyno sheets to see where torque usually kicks in with these. I have a +/-2 and +/-4 keys and was thinking of installing the 2 degree advance for a little stronger bite down low. Anybody run these with an advance that can give some feedback, or am I better off installing straight up at 10:1?

 

I would run it straight up, had it in my last bike and had a tq dip down low but had a thunderheader on it. It really kicks in around 3000 rpm, but that bike had less than 10:1 comp.

 

Thanks Blue. When I was looking at the HQ39 last year, you responded and said you really liked them. It also sounds like the heads you had on that build are similar to some I just installed a few weeks ago, so hoping I get similar results. I looked at that old post and saw you had around 111 ft lbs peak. What was the overall torque curve like - can't find hardly any Dyno sheets.

 

That bike has been gone for about 6 years now, but off the top of my head it peaked at around 4000 rpm and the hp would pull all the way up. I wouldn't worry about the low end with IC of 36 on that cam.

 

I run them at 9.6:1 static in my 95" they come on strong at 2800 (had to upgrade my stock clutch). At 10:1 I would definatley install them straight up.

 

Thanks both for the input. I just got back from dealer and had bearings and cams pressed into cam plate. I will install straight up and hope they run strong down low. I fought some low end power issues the past couple years and am a little paranoid, even with 36 intake close.

 

What exhaust are you using?

 

I have had several different 2-1 pipes, but just put on a set of old Fatcats with louvered baffles. I was worried the big overlap and scavenging of a good 2-1 might cause over-scavenging, but seems most guys I have seen having good results wth the HQ39's were running fatcats.

 

Did either of you have to do anything to ensure proper valve clearance with be hq39 cams? My heads have springs for .600 lift, but valves are stock size. I took bike around block today to make sure no leaks, etc. Valve noise was louder and got me wondering if valves might be hitting. Also turned pushrods 20 flats (24 tpi) preload.

 

I'm using forged flat top pistons, so the valve relief's were in the right place even with my slightly larger valves, I checked the clearance before I put it together (.020 off the heads and .030 head gasket with stock 06- beehive springs).
The HQ39 have pretty high TDC lift .193 IN/.191EX. What pistons do you have?
How does the motor run?
Mine is quiet, although I can hear a bit of valve train noise around 2500rpm.
Do a compression check.