268 Voodoo cam rpm and vacuum

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mbaird

mbaird

mbaird
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I'm running a Lunati Voodoo 268 duration (60403 If I remember correctly) cam in my 360.
I'm pulling around 11.5" of vacuum @ around 875-900 rpms idle in park.

I know this is a fairly common combo.... What are you guys getting for vacuum and idle RPMs?
 
I run a Comp 268, I don't know if the profiles are similar, I get 13 inches at idle.

Have you dialed it in with a vacuum gauge?
 
Still sorting things out....

Kb107s
J heads with bowls blended
LD340
Dougs 452
Initial 16-18 before ( still playing with that) 36-38 total

Vacuum signal bounces slightly 10.5-12ish
 
When you get the timing permanently situated, then you need to check the vacuum. I wouldn't worry about it until then, because the initial timing will greatly affect the vacuum reading. Adjust carburetor first, then timing.
 
I've played with 3 different carbs so far... carter AFB , 650 DP and 750 vacuum secondary.
I'm more familiar with the Holley and have a slew of them .
I can't do any road tuning until my friend stops by on Sunday to weld the perches to the axle tubes.
just trying to get some feedback from others with a similar combo.
 
mbaird said:
I'm running a Lunati Voodoo 268 duration (60403 If I remember correctly) cam in my 360.
I'm pulling around 11.5" of vacuum @ around 875-900 rpms idle in park.

I know this is a fairly common combo.... What are you guys getting for vacuum and idle RPMs?
Click to expand...
I run a Comp 262 XE and have 15 @ idle 850 rpm .
 
Keep in mind that our elevation (~2800 feet MSL) means a slightly lower vacuum reading. Those numbers don't sound out of line, but they really don't matter a lot. How does it drive?
 
I have that cam. That idle speed seems a bit high-ish. Try around 750 unless you need it that high for an Auto. I think I got 15" before I pulled the motor.

Do you need higher vacuum? Like power brakes or a racing class with a vacuum rule?
 
jerry6 said:
24 , has me wondering if I have a problem with 15 with a Comp XE 262 , 10 " difference is a big gap considering my cam is about the same .
Click to expand...

They are nowhere near the same. You aren't even comparing apples to oranges here. The stock 340 cam has a much slower opening and closing rate, plus it's on a 114 center. Modern cam grinds have much more area under the curve and will have less vacuum.
 
C130 Chief said:
Keep in mind that our elevation (~2800 feet MSL) means a slightly lower vacuum reading. Those numbers don't sound out of line, but they really don't matter a lot. How does it drive?
Click to expand...

I can't really drive it until I get my perches welded.....
This is a new rebuild..
 

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power brakes with 11.5 vacuum , not sure that is good enough .
 
I had a 340 dart sport (4Dad owns it now) running running a comp .638 roller with PBs
And it had no problem supplying enough vacuum. ...
But it's not like I was Autocrossing with it.

I still have to tune the Vacuum advance and mess with the jetting.
 
Perches are welded in now.....

While I was waiting for Joe to arrive I warmed up the engine and checked the cylinder pressure. I am get a small lifter knock but can't isolate which one....
2 cylinders were 135-138 and the rest were 145ish.... 1 plugs was light but all others were black. This is a brand new motor with about 1.5 hrs on it...
 

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I'm getting around 14" with a Comp xe268 in a 318, sounds like something is up with yours. I believe the Voodoos are slightly more tame (and probably a better cam, I run a smaller one in my 350 truck and it's great).

Anyway, wiped intake cam on that cylinder maybe?
 
CultClassik said:
I'm getting around 14" with a Comp xe268 in a 318, sounds like something is up with yours. I believe the Voodoos are slightly more tame (and probably a better cam, I run a smaller one in my 350 truck and it's great).

Anyway, wiped intake cam on that cylinder maybe?
Click to expand...

A 60403 Lunati is a step up from a Comp xe268. The xe268 has slightly more advertised exhaust duration, but the Lunati has higher lifts and faster ramps, so the duration at 050" is actually more on the 60403 than it is on the XE268. The lunati will have more area under the curve, and I would expect it to have slightly less vacuum. It wouldn't be much, I would still expect it to be around 13" at idle.

Comp XE268
Basic Operating RPM Range: 1,600-5,800
Duration at 050 inch Lift: 224 int./230 exh.
Advertised Duration: 268 int./280 exh.
Valve Lift with Factory Rocker Arm Ratio: 0.477 int./0.480 exh.
Lobe Separation (degrees): 110
Grind Number: CRS XE268H-10

Lunati 60403 (now #10200703)
Basic Operating RPM Range: 1,800-6,200
Duration at 050 inch Lift: 226 int./234 exh.
Advertised Duration: 268 int./276 exh.
Valve Lift with Factory Rocker Arm Ratio: 0.494 int./0.513 exh.
Lobe Separation (degrees): 110
 
Cyl pressure seems low for a fresh rebuild . Can you list the rest of the build ?
 
jerry6 said:
Cyl pressure seems low for a fresh rebuild . Can you list the rest of the build ?
Click to expand...

Well, the 107's and J heads wouldn't necessarily be a high compression combo if the engine wasn't zero decked or the heads shaved. Especially with bowl work that would increase the size of the chambers.

With only 1.5 hours on it, the rings may not be fully seated either, especially if it hasn't moved (no load on the engine).
 
Nothing special.... 2.02s in J heads with a little bowl work./ KB107 .030 over /LD340 / hughes rockers , valve springs and retainers / Dougs 452 headers / cloyes timing set / melling pump / stock rods with beams polished / Mopar electronic with orange box / Holley 750 / 904 with TF2 kit / 3.55 SureGrip in 8 3/4 / 74 Dart Power disc upfront and Jeep discs in rear / new front suspension and Hellwig sway bars front and rear.
 
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