Saw this thread and am confused as to why you wouldn't be able to run high lift cams with oversize valves??
https://honda-tech.com/zerothread?id=168244

 

because the larger lift on the cams would make the valve open more. and since the oversized valve head is "larger" it will come closer to the piston top and might cause contact.

it's not that you cant run larger valves with the bigger cams you just gotta be sure your valve relifes on the pistons are big enough.


[Modified by non-VTEC, 9:18 PM 5/12/2002]

 

i heard that the new skunks used with oversized valves will touch each other. not the piston, the valves will touch. im sure they would hit the piston too like stated above

 

I understand the reliefs coming into contact but why the valves? Is it something with Skunk2 only? If you can't use oversize valves with Skunk2 then you couldn't use them with JUN either......right?

 

valves can touch easier with oversized valves or long duration cams. It can also touch when adjusting your cam gears for more overlap.

 

The most sure fire way to check for valve to valve clearance is to run the cams in a head bolted onto a block with no pistons/oil pan etc and do a visual of how close the valves are during the overlap phase.

Sounds like a pain in the butt, but it's a lot better than clicking your valves togther.

 

Unless the two valves are touching each other when installed and closed in the head, how can they touch each other when they open? The valve guides run parallel to each other, so the valves could never touch each other. I guess if the valve guides were installed crooked or so worn out that the valve could wobble, but then the motor would not run very long anyway. There is no way that changing to a higher lift cam make valves touch each other.

 

The concern is with intake valves touching exhuast valves during the overlap period on long duration cams with alot of lift during the overlap period.

This can be worrisome since most tuners like to increase overlap when they retard the exhuast cam and advance the intake cam.


[Modified by Rocket, 7:16 AM 5/13/2002]

 

actually you can just bolt the cams ontot he head without boltign head ot the block, bust turn both gears for clearance check ... I do it all the time with 0.5mm os

greg

 

Valve guides are not parallel to each other. They point inwards to each other. B16/B18 heads all have a spherical combustion chamber, so the valves are pointing towards each other. Maybe your thinking V8's that only have two valves and have a flat combustion chamber.

 

My bad. I was thinking only in terms of exhaust to exhaust and intake to intake...not intake to exhaust. Excuse me while I spit out some crow feathers...

 

Oversized valves don't give you any extra horsepower on NA Hondas, and not enough to make them worth your time on FI and nitrous applications. So who cares anyways.

 

 

Greg, how do you acount for how much overlap the cams have and where the valves would be? I have always done what was said earlier with the bolting to the bare block with the crank and timing belt and hand cranking the motor.

I can imagine(with just the head not bolted to the block) turning the in cam and the ex cam the same amount at the same time(to simulate the timing belt turning them) but how do you keep the valvesprings from moving the cam more than you want it to?