Join Date: Nov 2006
Location: North Channel Lake Huron
Re: 454 build will it work?
Over the years I've learned you have to be particular with the BBC Valve train as they are HEAVY. If the Rocker Geometry is not accurate you can quickly damage Valve Stems and wear out the Guides and break components ... etc. GM Engineers did a wonderful job Designing & SPEC the MK IV - Believe me - So Don't Astray from it.
I like the Torquer 268H-10 or that Lunati 112 LSA profile cammed in a low compression 425Hp 454 - They are virtually maintenance free but will want to rev Past 6000 so that Valve Train has to be relatively sturdy and accurate. Unfortunately your modified (milled .030") 049 Heads are imposing forces on the Valve train Geometry and move the Valves closer to the Piston, not that a Mid .5 lift a 268 duration should comprise the pistons but it does compromise the Valve Train & Intake Geometry which is an Expensive FIX.
If you want that 9.2:1 Static, I would see about trading them 049's in for a set of 118cc 781 castings and all concerns about Rocker Geometry and Intake mating will be gone as well as the expense of modifying parts that make them worth less to enthusiasts that know better.
Of course you can use the 113cc 820 heads and up the Static to say 10:1 and run a bigger cam like a XM274H-12 or XM280H-12 placing the DCR at 8:1 but now it's a 92 Octane 6200 rpm 500Hp mill ;o)
You can mill approx .005" to .010" off a Head to Straighten and refresh the surface but .030" is over board as it effects every component of the Valve train and Intake System.
Racing Catalogs do not Cross reference Component Compatibility well but their Parts are designed for OEM SPECS; for instance, your Pistons are designed for either the 820 or 781 heads, depending on desired Static compression, Cam Selection relative for Pump gas. I think if you used (unmodified) 122cc 049 castings with them pistons, a Blower would be in mind. The Larger Domed Speed Pro ZL2349F30 Pistons are more suited for the 781 and 049 Castings - You beginning to get the Drift ;o)
Never let a Mechanic or Machinist's talk you into shaving Heads for the sake of Hi-Perf as it opens a whole can of Expensive Worms that may or may not work as they plainly have no clue what they are doing in regards to SPECS; however, you can Deck the Block to accommodate Head Gasket thickness and Quench.
If I ever happen to break a push rod, or any valve train component, in my 625Hp SR MK IV, I can reach into the carcass of a Wrecking Yard Block and use that part. I'm pushing the envelope on Pump Gas with a 10.2:1 Static SR Donovan Cam Gear, Crower HIPPO, Lunati Cammed, 7000 rpm 625Hp 460 running TRW Speed-Pro L2465F30’s with 2.19/1.9 Manley Severe Duty Pro Flow Valved 781 casting topped with a Jomar Girdle, forged rotating assembly and considering 402ci 820's Heads with a Bigger Cam - We are a Sick Lot ;o)
A Holley 750 Dp 4779/Elelbrock RPM is just fine to reach 6500 rpm but an 830 cfm 4 Corner Annular 80511-1 NASCAR/RPM Air-Gap does the Job to hit 7000 rpm with Oval Ports providing the rotating assembly is Forged. A cast crank (recommended X-Drilled) is just fine under 6800 rpm but then again a HFT Lifter Baffs at 6400 rpm in a BBC but will hit 7000 in a SBC. I shifted my HFT 340 MAG Dodge Engine at 7200 rpm but I did damage my valve seats over time. You don't know what I put my British 1600E Lotus Cortina and Swedish B1800 and 21MEF 240 Volvo's through. Love the BMW 2002 and the awesome Toyota Crown, Truimph TR6, 2+2's ...etc. Oh My them Leyland and Jaguar DOHC Engines are Special.
I can put it across better then Most Enthusiasts with the least amount of words and wish I had this knowledge when I Started; but, I lived through the process - You want to Race - Click on my Flickr Cannon Ball Daily Grocery Getters for the last 40 years - There are ONLY 2, which I still ride, a 4 wheel GM 70Z & a 2 wheel Breganze Laverda 750 SF - Both are Table Top 7000 and 8000 rpm 1970 Vintage ;o)
Last edited by Z15CAM; Aug 29th, 10 at 06:39 PM.