I've got an Olds 403 that I'm in the process of collecting parts for. The cam guru over on ROP suggests a custom ground Lunati; of course he's a dealer for them (I'm looking for some more unbiased opinions). I read a 403 thread on here from a few years back where a member said he ran the Isky Mega 280 in his 350 and 403 circle track cars. I'm wondering what the consensus is on why to choose one over the other? Are my cam consideration choices too big for my goals? I also don't want to undershoot the cam! Here's what I've collected for my build so far: 1979 Olds 403 from a T/A Olds C heads (already been to the machine shop w/new valves, comp springs & guide plates), have to go back for drilling out the bolt holes to 1/2" and redrilling and tapping the rocker studs too. Olds 330 Crank (freshly machined .020 mains .030 rods) Harland Sharp Roller Rockers Edelbrock Performer RPM J&S Girdle 7 quart pan My goal is a hot street engine with 400+ lb/ft and 400+/hp. I'll most likely be getting the KB hypereutectic pistons that are .024" over unless the machine shop says I need .039" over (this is KBs sizing to use BBF rings), one cylinder does have slight pitting and needs to be cleaned up. I'm planning on 10:1 CR so that I can run pump gas. This will be going in 3300# Cutlass with a 200-4R trans and an 8.5" 10 bolt geared 3.73. The specs on the ISKY Mega 280 are: Product Description Application: High performance use/bracket racing. Lopey idle. 2500 Stall. 9.5-10.5:1 compr. 3.90-4.11 axle ratio. Up to 780 CFMCarb RPM-Range: 2500-6800 Value Lift Int/Ext: .517/.517 Value Lash Hot Int/Ext: .000/.000 ADV Duration Int/Ext: 280/280 .050 Duration Int/Ext: 232/232 Lobe Center: 108 The specs on the Lunati Street Master Hydraulic Flat Tappet Cam 285/285 are: Product Description Hydraulic Flat Tappet. Good cam for high performance street or Pro Street applications. Needs 2000- 2500 RPM stall converter, headers, 9.5:1 compression ratio and 3.73 gearing. Rough idle. Advertised Duration (Int/Exh): 285/285 Duration @ .050 (Int/Exh): 235/235 Gross Valve Lift (Int/Exh): .540/.540 LSA/ICL: 108 Valve Lash (Int/Exh): Hyd/Hyd RPM Range: 2000-6000 Includes: Cam Only What's the deal with Lunati claiming power coming on lower and signing off earlier even though it's a bigger cam?
What year Cutlass? Not sure about Lunati but the Isky decal would be hamb friendly I did run a Lunati in a 225 slant six . Had a lot of varoom varoom
I'm using a Lunati Voodoo cam in my 355 and it has a lot of bark to it, but only a 268/276 grind with a .489/.504 lift. I would check that Lunati .540 lift carefully for interference. I'm leaning towards the Isky in your case. My Lunati is very quiet under the valve covers, a frequent complaint on a comparable Comp Cams product.
Lunati may have 4-6* advance ground in. This would show on its advertised RPM. If you go with Isky I'd advance it 4* anyway for the street. I live local to Isky and use them in our circle track engine.
Having been a long time Olds man, it really doesn't matter which cam you choose as long as you don't overdo the lift if you are using stock rockers and stay with 110 to 112 degree lobe separation. The less separation you have will enable you to bleed off some compression and allow a more radical profile on the cam.
Both have good tech departments. Have you talked to them? Cam selection is a bit more detailed than deciding which six pack to pull out from the cooler. Based on your application they can play with lobe separation, lift, and duration to get what you have in mind. The Isky cam you listed seems to want a bit more gear that your 3.73s and the other may have more lift than you can use.
I had a 3.56 stock rear in my Ford when I put it together... lugged badly under 1500 RPMs. This is critical to avoid. I ran some numbers carefully since I don't have overdrive, the magic number was 3.89 and drives well around town in 4th gear. I'm doing 3200 at 70 MPH.
Yes, you need to be up in the power band a bit at cruise RPM. All kinds of free calculators to play with tire size and axle ratio to test RPM at different MPH in each trans gear. All the pieces need to work together for a driveable street engine. It is easy to kill driveability with too much cam. I have done it many times in my younger days.
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