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rv10 cam - how much advance?
https://www.slantsix.org/forum/viewtopic.php?t=43622		 Page 1 of 2
Author:  gtdart [ Sat Feb 12, 2011 9:16 pm ]
Post subject:  rv10 cam - how much advance?
I'm looking for low end, hill climbing torque for my 64 dart conv.

'75 peanut head 255
9:1 compression
Erson ground RV10 cam
single Carter
no accessoires
3.21:1 rear gear with tall rear tire
833OD

The Intake Center line of the RV10 cam is 108 degrees (per cam card).
Installed on dots, I get 112 degrees, 4 degrees retarded from the cam card spec. I'm thinking of shooting for 106 degrees, which would be 2 degrees overall advance. Is this a good target for my daily driver? Chain is a new Cloyes double roller, which appears to be responsible for the 4 degree retarded ICL.

I know I need to advance this cam, my question is, how much? I live in a really hilly place, gaining 2000 ft in elevation on my 11 mile drive home from work.
Author:  Dart270 [ Sat Feb 12, 2011 9:21 pm ]
Post subject: 
I will never degree ANY cam for a 225 at more than 104, based on my experience and others. I would set your at 100-103 if you want low end torque.

Lou
Author:  gtdart [ Sun Feb 13, 2011 10:27 am ]
Post subject: 
Thanks for the quick response Lou. From what I've read here, 4 degrees advance seems to be on the high side of the recommendation. What are the tradeoffs with 4 or more degrees advance, besides top end power? Is milage and drivability compromised? This is a daily driver and, as you can see from my gearing, I'm trying to stay away from the gas station. :wink:
Author:  Aggressive Ted [ Sun Feb 13, 2011 11:32 am ]
Post subject: 
Doc suggested I run mine with 4 degrees advance and it gets good mileage with lots of power down low. I have run rear ratios from 2.93, 3.23 and a 8 3/4 Sure-Grip 2.76 which is my favorite. If you advance the cam and recurve the distributor you will have lots of torque which equates to better mileage and crisp starts. Cruising at 60 mph, it turns 2500 rpm, 15 to 18" of vacuum and 25 mpg with #57 jet @ 3500 lbs. For reference my recurve chart is under Engine FAQ.
Driveablity is improved with more advance on this cam. I can spin both P225-60 tires very easily with this setup.
Author:  gtdart [ Sun Feb 13, 2011 2:45 pm ]
Post subject: 
I just finished installing the offset bushing and hit 103 degrees.

Drilling the Cloyes cam gear gave me a little trouble. There is a dish cast into the gear surface running right through the cam pin alignment hole on both sides of the gear. My drill press wandered just a little off center. When installing the bushing, I had to clock the bushing a little to hit the cam pin center line so the gear would seat on the cam. Instead of installing the bushing in the traditional "advance" direction, I installed it in the "retard" direction and advanced the cam one tooth. In the end, I installed an 8 degree offset bushing and, because of the slight re-clocking of the bushing, I achieved 6 degrees of movement.

It's nice when the math supports the final results. With a 50 tooth cam gear, one tooth = 14.4 degrees on the crank. My initial install was at 112 degrees requiring that I advance it 8 degrees to achieve 104. By advancing the cam by one tooth and retarding the gear by 6 degrees (14.4 - 6 = 8.4) I snuck up on my alignment from the other side - so to speak. Where did the .4 degrees go? I'll chalk that up to human error - close enough.

Thanks again for the re-assurance about where to position this cam. Once it's running, I'll tackle the distributor curve.
Author:  Dart270 [ Mon Feb 14, 2011 7:30 am ]
Post subject: 
Sounds perfect.

When I have done degreeing, I am not confident of my measurements beyond +/-1 degree. I accept that as the error. I do not have a huge wheel, and of course there is backlash to keep in mind.

Lou
Author:  Doc [ Mon Feb 14, 2011 8:42 am ]
Post subject: 
If at all in doubt, check the overlap event to see how well centered it is over true TDC... with the advance, you should see more overlap on the intake opening side of TDC.
Run this check at the valve stem, with your lash settings.
With mild RDP grinds, (= a short overlap period) combined with lots of cam advance, just make sure the exhaust valve is not closing before TDC, when at your final lash settings.
DD
Author:  gtdart [ Mon Feb 14, 2011 4:34 pm ]
Post subject: 
Thanks Doc, will do. I'm still waiting for the gasket set to arrive, did the cam install with the head off. I'll close up the top end first, checking the overlap as you described before I button-up the timing cover.
Author:  Doc [ Mon Feb 14, 2011 5:06 pm ]
Post subject: 
You can set the head on the block and install the rocker shaft w/ 2 puchrods, to do the overlap at lash check... basically do a "mock-up" so you can see what the engine will see, once it's together and at lash.
DD
Author:  gtdart [ Wed Mar 02, 2011 1:04 pm ]
Post subject: 
After a few days away, I mocked-up the head and number 1 rockers. Intake center is at 76 degrees and exhaust is at 73 degrees. The Exhaust closes at 40 degrees after TDC. Does this sound correct?
Author:  Doc [ Wed Mar 02, 2011 4:14 pm ]
Post subject: 
Those numbers do not seem right.
See the specs below and re-check.
DD

Image
Author:  gtdart [ Wed Mar 02, 2011 6:39 pm ]
Post subject: 
Thanks Doc, I'm clearly not getting this - first time for me. Here's what I'm doing. All measurements taken from the top of the valve.

Intake open @.050" = 0 degrees
Intake close @ .050" 208 degrees
- duration = 208, card lists it at 210

Exhaust open @ .050 = 141 degrees
Exhaust close @ .050 = 355 degrees
- duration = 214, card lists it at 212

I made the following illustration to help me visualize what I'm trying to confirm. Am I seeing this correctly?

Image

So, while duration isn't what I'm needing to address at the moment, the exercise at least revealed that I wasn't reading the wheel correctly before. I'm assuming that I need to confirm the intake and exhaust open and close events to determine my overlap in relation to TDC. From my numbers above, I'm lost on how they relate to the numbers listed on the card. The intake centerline method was used achieve the initial 103 degrees advance.

Here is my cam card:
Image

thanks, -shane
Author:  gtdart [ Fri Mar 04, 2011 9:39 am ]
Post subject: 
I'm still fussing over the final cam location. I'm repeating the numbers I listed above and verified that while the exhaust closing event is happening 5 degrees before TDC @.050", actual final close happens at 35 degrees after TDC.

To me, it looks like the overlap is favoring the intake side and the exhaust final close is not before TDC.

Doc, Am I interpreting your instructions correctly? Is it safe to close up this motor?

thanks -shane
Author:  Doc [ Fri Mar 04, 2011 9:50 am ]
Post subject: 
So with the intake at .010 lash, it should start to open somewhere around 45 degrees BTDC.
With the exhaust at .020 lash, it is closed at 35 degrees ATDC, is that what you are seeing?
DD
Author:  gtdart [ Fri Mar 04, 2011 10:02 am ]
Post subject: 
With intake lash at .010", it starts to open at 30 degrees BTDC.

With the exhaust lash at .020", (previous measurements were at .012" lash - too tight) it closes at 5 degrees ATDC.

thanks, -shane
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