So I have an unknown rv cam in my 20r engine. When I put timing to 7btdc it is definitively not the right setting.

If some of you with rv cams can chime in and let me know what you have yours timed at that would be great so I can get a range.

Also, any advice on timing by ear.

 

Did your chain posibly skip a tooth? Just a thought. How is it acting "not right". Your advance sounds about right to me. I have mine at about 12°, but that's with a mech advance dizzy (no vac advance to unhook when setting so that would be like yours at idle with vac hooked up).

 

Mine at idle is 10 degrees to the zero mark are u going by that or the 85 markon the gauge

 

it idles fine, just doesn't sound great and seems a little sluggish

i'll check what mine is without the hose unplugged

and see how it does at 10

I was going by the 8 5 mark, how else would you do it?

head has been decked too, I know that can affect it a little

 

Timing light with a delay is how you could do it.
Get the truck up to running temp, play with timing till it "sounds best" with vac hooked up, unhook avac and note where timing is set, take for a drive and pull a good hill. If it's pinging on the hill, retard timing some and repeat till you find where it feels right. Keep an eye on your plugs to make sure you're not too advanced/lean.
Adjustable cam gear would be a good investment with the block and head decked, something I've been meaning to get for years.

 

i was using a timing advance light, mine is set to 9.5 degrees to be picky thats with my hoses off, when i hook my hose up i only use the ported one on the outter end and it does not seem to do anything at idle since its a ported vac, i never have hooked up my manifold side of teh advance, not sure if i need to as i didnt' set up the carb or timing but it does pull well

 

so it looks like my water choke is not working which has complicated things a little. But how are you guys getting accurate degree readings? I am looking at the 85 0 on the engine and kind of envisioning about where 12 would be (where it sounds pretty good, with vac attatched).

 

i advance till i get negative results out of the motor...

im around 10-12, carbed 260 cam

 

How is the advance giving 8 degrees advance at idle I thought the manifold source was supposed to work at high altitude and the ported only works on acceleration? 12 at idle hooked up and 5the unhooked? What advantage is that over only using the ported source to the putter diaphragm

 

Set your timing at 30-32 degrees "Total" timing with it all in at about 2000 RPM. You will need a "Total" type timing light that you can purchase at Sears to do this. This method eliminates "Playing" with the timing at lower RPM ranges and should give you good performance.