[weedy64]

Anybody know what stock valve spring pressures are at a known installed height? They don't really spec. it in the manual, just free length #s for both Int and Ex.

I felt mine were weak so they got pulled while it was apart and new ones from KW purchased.
Well, I had time during the holidays too muck with it and was re-assembling the cylinder head with different cams (Kent, I have never run them) and KW dual valve-springs, and I dont feel good about it...they are like compressing rocks and I can't turn the cam with all tightened. The head is off the bike, so its just my hand on the cam gear. I will try again with some soft channel lock pliers and then I will drop to one single spring and try again, with a oem cam if necessary.

I measured a couple KW springs and both were at or above spec 65# at 1.375"

I maybe bought too much spring for a 0.375 VL cam. Im now nervous about stressing the cam chain with so much pressure and I no longer have oems to measure.

I guess my next step is to put in weak hardware store springs and measure my installed height and rotate cams and check for binding.

 

[color me gone]

i believe stock install height is 38mm. Seat pressure at that height is 35lbs-ish. I don’t know open pressure. I think Ace Performance back some years ago saw 40+lbs by shimming the stock springs. I would have to dig in the shop to get the shim thickness. My 1427 with 445” lift intake cam had 65lb carpenter springs. 1mm over size valves. Valve control was a issue approaching 13k. I am currently at ~50lbs in my 1361. 415 intake lift. Power dies at 12.5k. Not sure if it’s spring pressure or my exhaust is small.
I purchased a 1287 second hand. Built by Ace. It had 372” cams from web i believe. The springs were shimmed oem. No issues with valve control. 40-45lbs will obviously be easier on the cam chain.

cmg

 

[color me gone]

PS…

65lb springs on .400 lift is a cam chain killer.

cmg

 

[weedy64]

I think maybe my scale calibration was inaccurate. I will install a few valves in the head and recheck in place with a machine shop's spring tester. My oem installed height should have grown a little with mileage and a valve grind.

What do you use for measuring installed height in this type of head? My valve mike is for V8s and is too big for these. I got the ~1.375" IH with the tail from my calipers, no error there lol.
So 50# IH and a spring rate of 280#/" gives I = +105# and E = +98#. I think it can live with that. Only thing I can do is ditch the oem base washers and run flatter ones to gain IH if the springs are still too much or get OE springs.

Id hate to blow a cam chain!.

 

[color me gone]

Kzscott cut open a head…lol. Clean shot to measure.

APE has a method for measuring on their site that is pretty straight forward.

cmg