Cam timing. Check my work please

[db484bhpv8]

Currently checking the cam timing on the newly installed Tornado cam.

Heres the spec



I set TDC with the dead stop method so am happy with that.
The JP timing gear was installed on the zero keyway.
A new dial gauge has been set to the top of the inlet retainer.
I turned the engine clockwise till the dial gauge reached top ie reversal point and set to zero.
The engine was backed off .1 then back clockwise to 0.05 and i recorded 81 degrees ATDC, carried on past the zero to 0.05 again and recorded 149 ATDC. So add the 2 together = 230 dived by 2 = 115

So it seems the timing is out by 5 degrees.

Correct? Now do i alter the JP crank gear to 4 degrees retard or advance?

[clive f]

excuse my ignorance Derek, whats a JP Crank gear? do you not the vernier set up on the cam sprocket?

[db484bhpv8]

clive f said:

excuse my ignorance Derek, whats a JP Crank gear? do you not the vernier set up on the cam sprocket?

The JP is different. The cam gear is fixed and the crank gear has 9 keyways. Each key way is 2 degrees offset to the teeth so you can adjust 2,4,6,8 degrees retard or advance from the zero setting

[db484bhpv8]

Just refitted the crank gear to the 4 degree advance keyway and checked again.

Got 77 and 143 = 220 / 2 = 110. Sorted.... i think

[HarryW]

Years since I looked at RV8 cams but that seems like a very tame cam to me? Is it because it's blown? Lift looks very low too? Again is it a lack of pocketed Pistons?
Can't comment on the actual timing you've carried out, the only query I do have though is; if the adjustment is on the crank pulley is your timing mark now off by the same amount?

Edited to add I'll take back the lift comment, got metric and imperial mixed up, for some reason I read 0.5" as 5mm

Edited by HarryW on Friday 20th March 20:25

[Pupp]

Sounds like you've sussed it to me; only gotcha I can think of from memory is the 'dwell' time when the dial gauge reverses but I imagine you will have split that too. I like the JP gears; no prospect of anything slipping when installed. clever stuff.

Even more confused you had inlet valve/piston issues 'though if timing was retarded... exhaust yes

Were you using a duplex set up before? If not, just watch out for clearance with the inside of the timing cover if it's an intermediate one (the webs where the dizzy hole is)... mine needed some material removing

[Pupp]

On the lift figures, that's plenty - especially with the rocker ratios - rollers would be a good investment if not in there alraedy