Timing issues

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Ironmike

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Hi guys! I'm brand new to Mopars and the forum, so please have mercy on me.
Here's the car: 71 Demon 340, 4 speed and I THINK...3:21 rear end. 8 3/4 of course.
Weiand intake, Holley 700 DP and Mopar's Purple 509 lift cam.
Only own it a week or so and it's soooo cold blooded on cold starts, but seems to run pretty good after warmed up. Very torquey, nice throttle response. Just didn't seem to have the top end it should.
Today I put a timing light on and can't even see the TDC mark. Fiddled around and finally figure out the initial timing is 20 degrees AFTER TDC idling at 1100 RPM. I'm thinkin' "no way".
So I retard it down to right around TDC. Go for a ride....seems ok but, but maybe not as torquey. Gonna try a cold start tomorrow and see what happens.
Not sure if the mark on the wheel is off or the the cam(kinda radical for me) is affecting timing.....basically what I'm askin for is HEELP!
All kidding aside, any help would be greatly appreciated.
 
I have, a used, unknown to me 340. Dial indicators, degree wheel; tells me it is 284; .484 lift, 108 centerline. 10.25 compression (70 340).
It won't idle under 30 degrees. I have talked to people, and read up on-line.
It seems the answer is; let the engine tell you what advance it wants at initial; if it starts with no kick-back, then pull the rest of the cent advance out of the dissy. I haven't gotten that far yet.
 
The timing is a mess if it shows 20ATDC. Question is why. If the cam is a .509 the idle will be bad. Simple fact fo life with that cam regardless of how good the package is matched. If you can get it to idle at 750-800 with 15° initial then you're getting warmer. If you can get it to run on those settings, then you can start debuggint the rest of the combo. A stick, mild 340 with the .509, with mild gearing, will be a pig from idle to about 2500 when it IS running well.
 
moper said:
The timing is a mess if it shows 20ATDC. Question is why. If the cam is a .509 the idle will be bad. Simple fact fo life with that cam regardless of how good the package is matched. If you can get it to idle at 750-800 with 15° initial then you're getting warmer. If you can get it to run on those settings, then you can start debuggint the rest of the combo. A stick, mild 340 with the .509, with mild gearing, will be a pig from idle to about 2500 when it IS running well.
Click to expand...

Now we're gettin' somewhere. OK, I actually LIKE a rough idle camshaft. The thing is, I don't think a cam with this kind of lift will idle under 1000 RPM or so. It seems to like to idle around 1200 or so. Anyhow, I played around after work and have it set now at 14 degrees BTDC initial, idling at 1100 rpm. Haven't driven it yet(rain), but seems to idle waaay more consistant and starts really easy. Waddaya think? Am I getting close?
What about total timing?
By the way, thanks for your help.
Mike
 
Keep the settings the same and advance the timing. If the RPM picks up, you need to keep advancing it until it doesn't pick up any more RPM.

Advance, reset carb to idle rpm, advance... until it doesn't pick up any more.

Bump it maybe 2* at a time.

Max initial without run-on or kicking back on the starter is where you want to be.

That cam should be able to idle under 1K
 
If it works for you then it must be fine. I like a good running all around engine and that one isnt...lol. But it aint my car. You are not idling officially, you're in the transfer slots if you're at 1100 or 1000 rpm. The cam might sound killer, but it's soft under 2500 when it's running the way it's supposed to.
 
moper said:
If it works for you then it must be fine. I like a good running all around engine and that one isnt...lol. But it aint my car. You are not idling officially, you're in the transfer slots if you're at 1100 or 1000 rpm. The cam might sound killer, but it's soft under 2500 when it's running the way it's supposed to.
Click to expand...
OK, so help me, Jedi Master. You're right on about being in the transfer slots. I was ALMOST ready to drill a couple 3/32 holes in the plates until I read the last couple posts. I drove it today and jumped on it pretty hard. Actually runs pretty strong. Lotta rubber in 2nd gear. Actually hooks up pretty hard too. I'd say right now it's very close.
I WILL get that thing to idle where you guys say it should. I may not know Mopar's yet, but I can tune a Holley.
I really thought these old technology Purple cams HAD to idle higher 'cause of the overlap. See, I'm learning.
Anyhow, my Cragars came tonite and the next big purchase will be a new center section with 4:10's.......I think. Maybe a wee bit more agressive.
I CANNOT live with a 3:23 rear gear.
So once again, thanks guys! And please keep the advice coming. I'm a sponge.
 
Run as much intial timing as you can with the 509 cam in a SB. Recurve the distributor if you have to get at least 18-20 degrees intial while keeping total at 34-36 degrees.

You'll need 3.91 or 4.10 gears with it also.

The 509 cam does pull very strong from 2500-6500rpm but is kinda piggish down low.:-D
 
lol.. Seriously Mike, if you like it an it works for you you're doing fine. It's your car, your foot, and your acceleration. I'm just saying what I'd do if it was mine. No problem. More gear will help you in any event.
 
Your idle RPM has a lot to do with what duration you are running and not so much the lift. If your duration gets up into the 300 range then 1200-1300 is a normal RPM at idle. But a 280 duration will idle lower so 800-900 is normal. This is as long as you have everything else like timing, carb adjustments and dist pick up gap set correctly.
 
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