joerocket107
Veteran
Hey has anyone heard of replacing the cams on the rx1 when running the big HP numbers with a less of a duration on the cam? And changing out the springs and valves to. I am shooting for around the 350 mark. MC express turbo, Lowcompression pistons and carrilla rods on order. Just waitng for the 05 RX1's to come in. Thanks
RX-Boy
Extreme
We just finished a rx-1 head with porting, bigger valves, new springs, titanium retainers, and we stayed with stock cams, It should be worth another 40+ hp
KnappAttack
24X ISR World Drag Racing Champion
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Don't bet on it RX-boy. It won't do any good till you run out of turbo at about 400 hp. Good Luck with it though. Mike Knapp#17
joerocket107 said:
MC recomends a cam timing change I believe. I'm sorry that I do not have the details, but I'm sure someone here does.
With the thicker head gasket that MC supplies you are moving the valves further away from the piston, effectively changing the valve timing. I don't know what they are reccomending to adjust it though.
wolfman
Newbie
Valve timing
Changing different thickness of head gaskets does not change valve timing on a four stroke motor. The valves are timed/linked to crank shaft by the timing chain. When you set the relation up between the two the crank is normally at #1 top dead center and then you adjust the valve timing accordingly. So a thicker gasket doesn't change that relation. The valve can be farther away, but the valve is still going to open at the same time in relation to the crank rotation. Unlike a 2 stroke were you put a thicker or thiner base gasket in you change the relation of the port opening to the top of the piston, and that changes port timing because the crank will be at a different degree of rotation when it is closed or opened.
Wolfman
Changing different thickness of head gaskets does not change valve timing on a four stroke motor. The valves are timed/linked to crank shaft by the timing chain. When you set the relation up between the two the crank is normally at #1 top dead center and then you adjust the valve timing accordingly. So a thicker gasket doesn't change that relation. The valve can be farther away, but the valve is still going to open at the same time in relation to the crank rotation. Unlike a 2 stroke were you put a thicker or thiner base gasket in you change the relation of the port opening to the top of the piston, and that changes port timing because the crank will be at a different degree of rotation when it is closed or opened.
Wolfman
peteracing
Expert
cam timming
WOLFMAN, if you add a thicker head gasket, the valve timming
is going to change! unless you have ''sloted'' cam sprokets..
Its not going to change by much but it will. Like a worn-out chain,
it's lengt change (thicker head gasket = farther cam to crank distance)
WOLFMAN, if you add a thicker head gasket, the valve timming
is going to change! unless you have ''sloted'' cam sprokets..
Its not going to change by much but it will. Like a worn-out chain,
it's lengt change (thicker head gasket = farther cam to crank distance)
Mountaintech
TY 4 Stroke God
Peteracing is right. Adding a thicker head gasket will advance both intake and exhaust cams in the RX1. MCxpress recommends bringing the intake timing back to stock position when installing thicker gasket. As for the exhaust timing they say it is actually better slightly advanced.
wolfman
Newbie
I should have reworded it. I was refering to lakercr saying that moving the valves farther away from the piston will change vale timing. Moving the valves away will not change timing, but moving the cam shaft center line from crank will. If the gear is around 3" in dia. than roughly every .025" will be 1 deg. of timing. This only holds true on a overhead cam motor. A push rod motor on the other hand doesn't matter what the head gasket thickness is it always gong to be the same because the cam never moves in relation to the crank. When I wrote the first response I was thinking more on a pushrod motor than a overhead cam motor.
Wolfman
Wolfman
peteracing
Expert
valve timing
WOLFMAN, i know you knew that
WOLFMAN, i know you knew that
wolfman
Newbie
Sometimes it is hard relaying the info from the brain to the finger tips with out it sounding all jumboed up. lol 
I have built alot of racecar motors in my time and I just never take for granted that when your markes are lined up to put the chain or belt on that the cam is timed straight up at zero. We alway degree are cams in, and in most cases they are alway off. Thats part of mass production.
And I'm sure thats what Lakercr really meant.
Wolfman
I have built alot of racecar motors in my time and I just never take for granted that when your markes are lined up to put the chain or belt on that the cam is timed straight up at zero. We alway degree are cams in, and in most cases they are alway off. Thats part of mass production. And I'm sure thats what Lakercr really meant.
Wolfman
Yeah, I used the word 'effectively' to save myself from having to type something like the last couple of posts above...
Jack_Shaft
TY 4 Stroke Junkie
So what's the final word? Advanced intake timing by one tooth when using the double Yamaha base gaskets????
-JS
-JS
SuperDave
VIP Member
Valve timing
On race motors i found the best way was to set up lobe centers.
On turbo motor having the exhaust a little advanced so that overlap is not as much really helps turbo motors.
Many years ago on V8 American ford motor you could get same power at 6 lbs with turbo cam compared to double boost with stock cam.
If you put in thicker gasket that means cams are advanced which gives you heavy idle and better bottom end but will suffer a little on top.
285 duration 507 lift compared to 256 duration and same lift 507
This cams specs i tryed on datsun and found more power out of 256 and gas mileage from with 256 at up to 36 MPG compared to not much over 20 MPG with 285
Other motorcycle engines I would setup 110 degree lobe centers and big difference on dyno and when taken out on road.
On race motors i found the best way was to set up lobe centers.
On turbo motor having the exhaust a little advanced so that overlap is not as much really helps turbo motors.
Many years ago on V8 American ford motor you could get same power at 6 lbs with turbo cam compared to double boost with stock cam.
If you put in thicker gasket that means cams are advanced which gives you heavy idle and better bottom end but will suffer a little on top.
285 duration 507 lift compared to 256 duration and same lift 507
This cams specs i tryed on datsun and found more power out of 256 and gas mileage from with 256 at up to 36 MPG compared to not much over 20 MPG with 285
Other motorcycle engines I would setup 110 degree lobe centers and big difference on dyno and when taken out on road.