Regrind Cam?

-
bobscuda67

bobscuda67

Well-Known Member
Joined
Aug 27, 2005
Messages
2,106
Reaction score
387
Location
Michigan
Last year I put a Comp Cams XE274 in my car and I'm not real happy with it. It has a rough idle to it, but it has 16 inches of vacuum at idle too.
Car has a 340 with Magnum heads and exhaust manifolds.I'm thinking I could install Rhoads Lifters, kinda noisy though. Or I could have the cam reground. Is that a dumb idea because of the cost? Or just live with it.
 
If I was going to all the work and expense of pulling the cam, having it reground and reinstalling it with new lifters, I would just put in a new cam.
 
I really like the lunati voodoo 262. works very well with manifolds, has a nice sounding musclecar idle, but not rough. Has shorter duration but has the similar lift as the xe274 so shouldnt have any valve train problems.
 
Rough idle and 16" of vacuum? :-k What's the rest of your combo? intake, carb, timing advance at idle etc...

What RPM are you idling at? 16" is a little more vacuum than I would expect from that cam. And I agree with Mike, I wouldn't bother with a regrind. New cams aren't all that expensive, and you're going to have to spring for new lifters anyway. I'm just wondering if there isn't something else going on, 16" of vacuum isn't usually an indicator for a rough idle.

Looking at the cam-

XE 274:
advertised duration: 274 int./286 exh.
duration at 050" : 230 int./236 exh.
lift at 1.5:1 : 0.488 int./0.491 exh.
Basic Operating RPM Range : 1,800-6,000

By comparison, my Lunati Voodoo 60404 (old part #)

10200704 (new part #)

Advertised Duration: 276 int./284 exh.
Duration at 050": 234 int./242 exh.
Lift at 1.5:1: 0.513 int./0.533 exh
Basic Operating RPM Range: 2,200-6,400

Obviously the Lunati 60404 is a little more cam, the 60403 is closer to the equivalent of the XE274, so the 60404 is about one step up. But I'm idling at ~10" of vacuum. Idle is definitely choppy, but I wouldn't call it rough, at least not when it's warmed up. It's probably about the limit for what I would consider for a daily driver though, which is how I use my car. At least for a 4 speed car, an auto would make it a little easier to manage in traffic. ;-). But not as much fun.

1968 340, .060" over, KB 243 hyper pistons, Lunati 60404 cam, duration 276/ 284, Lift .513/ .533. Compression ~9.8:1. 308 heads ported and flowing 264cfm at .500", Doug's headers, Summit 2.5" dual exhaust with Dynomax welded Ultra-flo's. Eddy air gap intake, holley 750 DP, Timing set at 20* initial, 34* all in mechanical only.

Idle is about 750-800 in the video, the little rallye dash tach isn't all that accurate

[ame]https://youtu.be/62bjHlxzsoA[/ame]
 
Marcohotrod said:
not a very big cam, and a good amount of vacuum, maybe running rough cuz of something else
Click to expand...

WHat's the timing like on this engine? Idle speed?


toolmanmike said:
If I was going to all the work and expense of pulling the cam, having it reground and reinstalling it with new lifters, I would just put in a new cam.
Click to expand...

I'd agree with this. Looking at your current cam I'd go with one of these.

Crane 694561 or 15006
 
That sounds mighty good.

72bluNblu said:
Rough idle and 16" of vacuum? :-k What's the rest of your combo? intake, carb, timing advance at idle etc...

What RPM are you idling at? 16" is a little more vacuum than I would expect from that cam. And I agree with Mike, I wouldn't bother with a regrind. New cams aren't all that expensive, and you're going to have to spring for new lifters anyway. I'm just wondering if there isn't something else going on, 16" of vacuum isn't usually an indicator for a rough idle.

Looking at the cam-

XE 274:
advertised duration: 274 int./286 exh.
duration at 050" : 230 int./236 exh.
lift at 1.5:1 : 0.488 int./0.491 exh.
Basic Operating RPM Range : 1,800-6,000

By comparison, my Lunati Voodoo 60404 (old part #)

10200704 (new part #)

Advertised Duration: 276 int./284 exh.
Duration at 050": 234 int./242 exh.
Lift at 1.5:1: 0.513 int./0.533 exh
Basic Operating RPM Range: 2,200-6,400

Obviously the Lunati 60404 is a little more cam, the 60403 is closer to the equivalent of the XE274, so the 60404 is about one step up. But I'm idling at ~10" of vacuum. Idle is definitely choppy, but I wouldn't call it rough, at least not when it's warmed up. It's probably about the limit for what I would consider for a daily driver though, which is how I use my car. At least for a 4 speed car, an auto would make it a little easier to manage in traffic. ;-). But not as much fun.

1968 340, .060" over, KB 243 hyper pistons, Lunati 60404 cam, duration 276/ 284, Lift .513/ .533. Compression ~9.8:1. 308 heads ported and flowing 264cfm at .500", Doug's headers, Summit 2.5" dual exhaust with Dynomax welded Ultra-flo's. Eddy air gap intake, holley 750 DP, Timing set at 20* initial, 34* all in mechanical only.

Idle is about 750-800 in the video, the little rallye dash tach isn't all that accurate

https://youtu.be/62bjHlxzsoA
Click to expand...
 
Thanks for the replies!
The timing is set at 16* initial and has 34* at 3400 and the idle speed is 850. The vacuum advance is connected to manifold vacuum.
The compression ratio is 9.9 and I am using the 1.6 ratio rockers, so the lift is a little more.
With the 904 auto I have to slip into neutral at lights and that gets a little old. Since it's not a daily driver it's not that big of a deal I guess.
I have it apart now to replace the timing chain so it's a good time to change it out, or not.
 
Just richen your idle mixture and kick the idle RPM up too 1000rpm. Problem solved.
 
vacuum advance goes to carb above the throttle plates, in other words ported vac . manifold vacuum will add a lot of timing to engine. make the motor run bit rough. also, timing should be more at lower RPM.
 
I've spoken with Oregon many times since I have used their services a few times. One thing they said to keep in mind concerning regrinds is that according to them, the factories, especially Mopar hardened their cams almost completely to the core. That's important information......and information that companies like Comp are tight lipped about......IF they even know at all.
 
I agree with 72bluNblu on this one, I have a .030 over 340, KB 243 pistons, stock "X" heads using a Lunati 60403 cam, with LD 340 intake, 700 Holley DP, stock 340 manifolds and summit 2.5" exhaust and the car pulls approximately 15" of vacuum at 750 rpm.

So I would guess the vacuum is about what to expect from the camshaft in your engine.
 
You must log in or register to reply here.
-

Back
Top