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  #1  
Old Sep 30th, 09, 7:14 PM
awbrooks496 awbrooks496 is offline
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Alex
 
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Default 496 Cam ?

I posted this question under the Engine heading, but I think I will get more responses here.

I have a 496 that was built awhile ago. I am now ready to put it in the car. I have been reading on here about 496's and cam choice, and would like some opinions. The engine does have 049 heads I am sure they have been worked over fairly well, because the shop that built the engine is known for head work. I just can't find the paperwork on it right now. The bottom half is a Eagle Stroker kit. I was told the compression would be around 10.5 to 1. They also studded the mains (2bolt) if that really matters.
Cam:
XM270H-12
.544/intake .547/Exhaust
270/286
LS:112

This is going in a 79 Malibu that will see more street use. I will be having a th400 built, so that opens things up.

Opinions Please.... I don't want to starve the BBC and be unhappy with performance right from the start. I noticed that the grind the builder put it is actually a marine cam??? Thoughts?
Thanks
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  #2  
Old Sep 30th, 09, 7:45 PM
Jason Snyder Jason Snyder is offline
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Default Re: 496 Cam ?

the intake duration is only 226@.050 !!! it will idle like a stock 350 !! if you want performance ? you better swap out that cam ..... look into something that has 240@.050 duration @.050 , this is a good stating point for street performance . For example , that cam would barely lope in a 350 smallblock . now add 150 cubic inches and it becomes smooth as a babies @ss !
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  #3  
Old Sep 30th, 09, 9:11 PM
69 Malibu 69 Malibu is offline
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Default Re: 496 Cam ?

Why did the builder choose that tiny cam?
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  #4  
Old Sep 30th, 09, 9:12 PM
awbrooks496 awbrooks496 is offline
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Default Re: 496 Cam ?

That is the funniest thing I have heard today. "Add 150 cubic inches and it becomes smooth as a babies @ss!"
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  #5  
Old Sep 30th, 09, 9:19 PM
awbrooks496 awbrooks496 is offline
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Alex
 
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Default Re: 496 Cam ?

Todd,
I am not sure... I think it was one of those situations... I explained what I would be doing with the car and they stuck something they probably had in there. This is horrible to say, but I never asked the specs. They just told me it would be lopey and I would need at least a 2400 stall. Pretty sure it was a combination of me being very passive in the situation and them just having that cam. I wish I would have been very direct. You live and learn. They are a great shop and have done several things for me in the past. They know that I do more cruising, but I sure don't want it to sound like my 86 Chevy truck, or perform like it.
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  #6  
Old Sep 30th, 09, 9:20 PM
68chevelle533 68chevelle533 is offline
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Default Re: 496 Cam ?

I agree that cam will run out of steam in a 500 cubic inch engine real early. You need something that builds power to at least 5500rpm.
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  #7  
Old Sep 30th, 09, 10:06 PM
z15cam z15cam is offline
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Default Re: 496 Cam ?

Fist you need to know the Engine Build Spec’s to ascertain that the 496 does indeed have a 10.5:1 Static compression. If the 049’s have a 122cc Combustion Chamber and a 25.7cc Domed Piston used with a .019” Steel Head Gasket (.044" Quench) the Static Compression would be 10.5:1. Now you have to pick a Cam with an Advertised Intake Duration that will give you between an 8 to 8.2:1 Dynamic Compression.

I believe the Comp Cams Extreme Marine HFT Series with a 112 LSA is an excellent choice for a 496 Stroker but the XM270H-12 Range 1600 – 5800rpm 226/236 @ .050” – 544”/.547” 112 LSA would give you approx an 8.6:1 DCR which is, in my opinion, TOO HI for Pump Gas and you should run a longer duration but stick with the XM Profile like the XM 278H-12 installed at say 110 (2 degrees retarded) to achieve a dead on 8.2:1 DCR - Range 2000 – 6200rpm 234/244 @ .050” .564”/.566” 112 LSA. I have personally run the XM278 and got to say its one BEAR of a Torque Cam. With an 8.2:1 DCR your Advance will be limited before the motor will PING. I would consider the next Profile the XM288H-12 installed at say 106 degrees (6 degrees advanced) which would give you an 8.12:1 DCR (Very nice indeed) Range 2500-6500rpm 244/254 @ .050” - .570”/.575” 112 LSA.

With a 112 LSA you can run 3.31 or 3.08 Gears.

Download and install Patrick Kelly’s DCR Calculator here: http://www.empirenet.com/pkelley2/DynamicCR.html
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Last edited by z15cam; Sep 30th, 09 at 11:31 PM.
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  #8  
Old Sep 30th, 09, 10:36 PM
wildman926 wildman926 is offline
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Default Re: 496 Cam ?

If you are not afraid of solids, this would be your excellent choice in for a solid ft. It is one of the grinds that made Harold Brookshire famous. -

A solid will ALWAYS make more power

Lunati 402A7 -
Solid, rough idle. Good cam for bracket racing in 396-454 cubic inch motors. Needs 3500 RPM stall converter, headers, 10.5:1 compression ratio and 4.10 gearing.

Advertised Duration (Int/Exh): 288/296
Duration @ .050 (Int/Exh): 255/263
Gross Valve Lift (Int/Exh): .612/.630
LSA/ICL: 110/104
Valve Lash (Int/Exh): .024/.026
RPM Range: 3000-7000

The longer stroke and cubes will tame this down a bit, and you will love how it idles. Here is a video of it in a 496 -
http://videos.streetfire.net/video/S...-El_101416.htm
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  #9  
Old Oct 2nd, 09, 5:48 PM
awbrooks496 awbrooks496 is offline
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Default Re: 496 Cam ?

Hydraulic, rough idle. Strong cam for 496-540 cubic inch motors, also great in 465 HP EFI boat engines. Needs 4000 RPM stall converter, headers, 10:1 compression or better, and 4.10 gearing or better. (850 cfm carburetor recommended)

Advertised Duration (Int/Exh): 296/306
Duration @ .050 (Int/Exh): 239/249
Gross Valve Lift (Int/Exh): .575/.580
LSA/ICL: 114/110
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 3500-6500
Includes: Cam Only

Part Number: 302A9LUN
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  #10  
Old Oct 2nd, 09, 5:48 PM
awbrooks496 awbrooks496 is offline
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Default Re: 496 Cam ?

What about this cam (above)?
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  #11  
Old Oct 2nd, 09, 5:52 PM
awbrooks496 awbrooks496 is offline
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Default Re: 496 Cam ?

There was another Lunati Solid that I liked. I will post those specs in a few. Question... With the longer stroke bigger cube motors does that change the stall needed. I guess this would be a better example: If you put a 402A7 in a 396/427 let just say it requires a 3500 RPM Stall. If you put that same cam in a 496, which from what I gather the longer stroke/etc tames the cam down a bit. Will the 496 use the same stall speed? I am new to some most of this. I just figure there are no dumb questions.

Thanks
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  #12  
Old Oct 2nd, 09, 7:48 PM
427L88 427L88 is offline
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Default Re: 496 Cam ?

Good question. I'm on my 3rd set of GM heads on a 439 ci motor with that cam. It would take the powerband to abit over 6000 in 496, giving you great 5800 rpm shiftpoints. Reckon on 3000 rpm powerbands, and you might be able to get away with 2800 stall! See the 439 shifts up at 6600, so you need all of 3500 stall.
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  #13  
Old Oct 2nd, 09, 8:37 PM
wildman926 wildman926 is offline
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Default Re: 496 Cam ?

My similarily spec'd solid roller, Voodoo 60234 in my 496 behaves very well, and I have the same specs that Lunati recommends concerning compression, stall, and gearing, although not needed. You will be just fine.

But it does lower the requirements for the engine to run at it's best.
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  #14  
Old Oct 2nd, 09, 9:40 PM
awbrooks496 awbrooks496 is offline
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Default Re: 496 Cam ?

Walter,
Thanks for the advice. Would you go with the roller like you have, or the 402A7 like you mentioned earlier? I like the idea of the roller, but I wonder (another question) will I have to worry about the additional lift and clearance piston/valve? It seems like a ton of lift to me, but I know it really isn't. Thanks
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  #15  
Old Oct 3rd, 09, 12:49 AM
wildman926 wildman926 is offline
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Default Re: 496 Cam ?

Alex,

In the beginning of the thread, you stated that your car is more street use, so unless you are willing to shell out the coin to do it right on a solid roller, I would go with the solid ft. What I mean is this - Isky Red Zone lifters with EZ Roll option, a Rev Kit, and a stud girdle. The lifters have no needle bearings, and order them with the street oiling option. The rev kit keeps the lifters in constant contact with the cam, so no pounding during lash. The stud girdle just adds extra insurance. I did all this on the current 10.5-1 496. I had tons of P-V clearance.

I am building a second BBC, and it will be using the same solid ft cam I just mentioned, or maybe the new and improved version, Lunati 60243, and using Crower EDM holed lifters.
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