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| | | | Joined: Apr 2002 Posts: 2,168 A teacher, but always an apprentice. | | A teacher, but always an apprentice. Joined: Apr 2002 Posts: 2,168 | Thinking about swapping the stock lm7 cam for a comp cams 54-424-11 cam. Here are its specs:
Basic Operating RPM Range: 1,400-6,700
Intake Duration at 050 inch Lift: 212
Exhaust Duration at 050 inch Lift: 218
Duration at 050 inch Lift: 212 int./218 exh.
Advertised Intake Duration: 265
Advertised Exhaust Duration: 271
Advertised Duration: 265 int./271 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.558 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.563 in.
Valve Lift with Factory Rocker Arm Ratio: 0.558 int./0.563 exh.
Lobe Separation (degrees): 115
Camshaft Gear Attachment: 3-bolt
I am wondering what this will do to the vacuum and if it will affect a brake booster significantly?
I just want to pep this engine up a bit.
Thoughts? Critiques? Suggestions?
Thanks Bolters. I know I’m in good hands here. | | | | | Joined: Feb 2004 Posts: 29,803 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,803 | That's a relatively mild cam, somewhat similar to the Comp 268H that I put in a lot of street engines. It will have a slightly choppy idle and the manifold vacuum at idle will be a little low, especially if you're running an automatic transmission. A manual shift vehicle can get a little higher idle speed, maybe 750-1000, and the vacuum will stabilize. All the 268's I've had on the dyno pulled strong from about 2k RPM to 7K. This cam should be fairly similar in performance.
Be sure to check closely for valve to piston clearance, particularly at the exhaust valves.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Apr 2002 Posts: 2,168 A teacher, but always an apprentice. | | A teacher, but always an apprentice. Joined: Apr 2002 Posts: 2,168 | Thanks what I’m looking for. A good strong pull throughout. Would it be low enough, Jerry, to warrant using a hydro boost? Or will the vacuum booster suffice? I was looking at 8-9” dual diaphragm for space saving with the lm7 heads/covers. | | | | | Joined: Feb 2004 Posts: 29,803 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,803 | Put a vacuum reservoir canister somewhere. I've used discarded Freon canisters, or even a length of big PVC pipe with both ends capped, bracketed inside a frame rail. Fit a grommet into one end cap that will accept a check valve for a brake booster, and run a line from another fitting to your booster. The tank will stabilize the vacuum and hold it anytime the manifold vacuum gets low.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
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