How would you build an engine for a sleeper? You know, something that doesn't necessarily LOOK all that special but RUNS HARD. Well I have a few thoughts.
Displacement - More cubic inches are the ticket if you are not going to use a power adder. There are 4.5" stroke rotating assemblies available so let's go big. That puts us at 488 cid and as we all know, more cubic inches can use/hide more camshaft. With a longer stroke and the big (heavy) rotating assembly, don't be afraid of .003" clearances on the mains.
Camshaft - Speaking of camshaft, we don't need to go hog wild on the duration or the TYPE of cam. Flat tappet hydraulic will work just fine if you don't have the money to spend on a hydraulic roller. If you REALLY want to go for it.... use a SOLID ROLLER cam. One with moderate duration around 242/248 @ .050" and around .600" lift on a 108 LSA. The tight LSA is nothing to be afraid of as far as idle characteristics. Sure, it will have a slight lope but with that many inches, it won't be a tuning problem! If you want a dead steady idle, we can open up the LSA to a 112 from 108. Run a tight lash and only the best will be able to hear the solid lifter tick.
Cylinder heads - Okay, most guys don't know Pontiacs so you can paint your ALUMINUM Edelbrock heads Pontiac Blue and you are good to go! Of course, they would be FULLY ported! You've got a lot of cubes there that need to be fed. While we're at it, let's get around 10 1/2 to 1 to make this big monster SOMEWHAT EFFICIENT.
Intake Manifold - Same deal. You MAY be able to get away with a Torker 2. It IS a single plane intake, but who DOESN'T have an aftermarket intake these days?
Carburetor - Rochester Q-jet or an Edelbrock Performer Series carb will fit the bill nicely for the sleeper effect. Perhaps a little TOO well. Most guys look to HOLLEY for performance so a 4150 series wouldn't be out of place. Just TELL everyone your 1,000 cfm carb is a 750.
Ignition - Substitute your red MSD distributor cap with a black cap and no one would be the wiser.
Exhaust - We KNOW the reproduction Ram Air manifolds are good for at least 550hp
You won't need anything fancy because cubes are king. All we have going on here is a larger stroke crankshaft. In that case, we like to reduce the rpm's somewhat. Let's say a peak power rpm between 5,000 and 5,500 with a redline between 5,500 and 6,000. Some guys are afraid of a little rpm but with a street/strip style engine with a redline at 6,000 rpm, that is not a big deal because the engine only experiences that rpm for literally a second--- it's not living up there for hours at a time. With that many cubic inches, there will be an overabundance of torque so unless you are prepared for some serious chassis upgrades, we can suggest tailoring the torque peak so the low end is manageable with a major bulge in power/torque in the midrange. That goes back to the camshaft and induction. We will be building an engine just like this in the near future so take a look at
How many cubic inches do you need?
January 11, 2015
Heritage Series Pontiac 488
April 26, 2014
I feel this is a necessary topic because I have been reading some postings online that can make a guy just shake his head in amazement. Even when tal...