Bump your timing to 16 and see what happens. If it helps you will need to recurve your distributor.
Anybody running the '68 4 speed 340 cam?
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Swinger 340
Well-Known Member
Maybe I need to play with my timing. I do run the 68' 4 speed cam in my 69' 4 speed, with power brakes and the Vacuum is a little low for the booster to work well. I have no issue in my 72' Van with the DC auto transmission cam, with the brakes.
I have heard the vacuum is low for p. brakes. What number are you getting for vacuum?
Swinger 340
Well-Known Member
I'm getting like 7.
I and other members have spotted enough discrepancies to know you're full of crap. I actually don't care or want to know about you and your "mopes" but you're always right there shoving your "high pressure 367" in everybody's threads for all the world to see. So don't blame it on me. It's your own darn fault.
340six
King Of Bling
What does the cam card look like.
Wow that is low. Mine is around 10
I don’t think I got one although the numbers are out there. I believe it has 52 deg overlap 114 lsa slightly more duration than a regular 340 cam
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I've got a comp XE262 in my 1971 stock 340. Idle timing @16*, idle speed 650 rpm, and 13 inches of vacuum. No issues with my stock PB......180lbs cranking pressure.
Swinger 340
Well-Known Member
Mine came with power drums, but it also came with the automatic cam not the 68' 4speed one. I added it during my rebuild in 1988. I wonder if that is why Dodge added the automatic cam in all the early 340's and dropped the larger one, from the 68' 4 speeds. I always wondered why some 340's were hotter than others, if a 4 speed motor was installed in a automatic car.
Has anyone tuned their 4 speed cam with a vacuum gauge. Set the timing at maximum vacuum readjust the idle mixture and speed, and see how it starts and runs. You guys that have 4 speed cams, when you installed them, did you degree them in? Was the cam ground with advance built in?
Swinger 340
Well-Known Member
Thanks Toolmanmike, I will look into adjusting. I just set the timing to TDC as the book says. The car runs well, it just shows a low VAC. Everything else is a NO, unless the purple DC cam already has it added in.
It will probably be happier with 10° or more. The vacuum should rise with more timing. I guess I can't say that for sure. I haven't paid attention to that. When you advance your base timing you will probably have to limit your total timing (at 2000+ rpm) by modifying your distributor. This whole thing can gat a bit complicated. That's why most people just find a happy medium and as long as it runs good, doesn't kick back against the starter (from too much advance) and doesn't ping, all is good.
Is it the DC cam P3412044 68 340 Man. (LSA 114 / 276/284 / .444/.453" / ICL 112) or something else?
That cam has less overlap than the 340 4 speed cam if I am reading the specs right so perhaps 10 degrees is to be expected.
You have the car timed at TDC as in 0* ignition timing?
No wonder it has low vacuum. I've never had a mopar, let alone one with a bit of camshaft that liked anything less than 10-12* BTDC for ignition timing.
If your car is a stick, you can turn up the idle a bit as well after setting the timing to a better vacuum signal.
If you use vac adv connected to man vac, you will surely increase vacuum. I would think that cam will want 25-30* at idle & you should get at least 2" more idle vacuum.
Scroll down to post #6: www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html
Scroll down to post #6: www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html
Well I am running a solid roller with 246/250 and .648 lift on a 108 and I have around 8-9”s at idle and 18 cruising . That’s with a single plain intake .
Just advance your idle timing to 12-14 and you will be golden .
It takes 10 minutes counting getting your tools out !
Just advance your idle timing to 12-14 and you will be golden .
It takes 10 minutes counting getting your tools out !
You didn’t read. Post #7 says 18 degrees initial….again I am just looking for comparisons from people who have this cam
The only Direct Connection/Mopar Performance 340 cam I am aware of is the automatic cam. I've never seen nor read no heard tell of them making a 4 speed cam.
Swinger 340
Well-Known Member
I just through the box away when I moved 5 years ago. I'll check tomorrow to see if I still have the paperwork. BTW, in the box was a Crain Fireball. I just couldn't bring everything with me.
Forgive me if I asked, but have you verified your timing is correct? In other words verified your timing light is accurate? Also, have you verified TDC with a piston stop and checked that the balancer marks are in the correct location, that maybe the inertia ring hasn't slipped?
I’m sorry ,I missed that post .
I have never run the 68 4 sp cam but I have run many bigger cams . I would expect 12-14 @ idle and pushing 20 @ cruise . There will be variables like compression, timing , carb and exhaust system etc…. But under 10 just doesn’t seem right for that cam .
Have you tried another vacuum gauge?
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