This engine does not perform anywhere near my expectations and will not run on pump gas. What I am hoping for is a solution to the running problem. I am prepared to replace the camshaft and modify the pistons or replace them as needed. My goal is an 11-second street/strip bruiser. Can you help with suggestions or recommendations?
Jeff Smith: What were you thinking? Why would you assemble an engine without having the cam specs tattooed on your right forearm? The most telling information is the cranking compression at 185 psi. This is almost ideal for pump gas but you report the engine rattles, which is a bit confusing. Let's start with a timing curve. You should have 12-14 degrees initial backed up with another 20-22 degrees in mechanical advance for a total of 32-36 degrees. If the engine still rattles, pull a little more initial out. If it still rattles, then we'd suspect you have too much static compression. Stock 455s come with dished pistons around 30 cc's and now yours are flat. With pure flat-tops, you've likely got around 11:1 compression depending on how much the heads have been milled.
With 185-psi cranking pressure, your cam must have sufficient duration to bleed off cylinder pressure to test at that level because the intake valve closes later on a long-duration cam. So the cam may not be the cork. You need to know at least the lift and the duration, but to check that, you'll need to pull the intake and check the cam with a solid lifter. Hydraulic lifters bleed down too quickly to use for checking duration and lift.
The biggest limitation is that ancient Offenhauser manifold. Those dual quads may look cool, but sell them to a '60s archivist and step up to an Edelbrock Performer Olds 455 (PN 2151, $236 through summitracing.com). Edelbrock has a Victor 455, but we wouldn't recommend it for your application. Olds motors are known for their torque. Our recommendation would be the Performer, a 750-cfm carb like a Speed Demon, and perhaps a dual-pattern hydraulic flat-tappet cam of around 240/246 at 0.050 with a lift of around 0.520-0.550) using a 1.6:1 rocker ratio to help bleed off that cylinder pressure of that high static compression. Of course, this also means 131/44-inch headers. Cast-iron exhaust manifolds will not make any appreciable power. This won't get you into the 11s, but it might squeak you into the 12s.
David Freiburger: I disagree that you can't use a hydraulic lifter to degree a cam. It's certainly not the advisable procedure for precision, but a pumped-up hydraulic lifter would need to be pretty wasted to be overcome by the tiny spring pressure of a dial indicator. And you don't need to pull the manifold if you can rig a setup to place the dial indicator at the tip of the pushrod. Just make sure the lifter travels freely up and down.
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Synthetic Oil:Bad Idea?
Anthony Carson, Red Lion, PA: I'm trying to decide if I should switch to synthetic oil for my daily driver. You guys have tested the stuff quite a bit and always show a power gain while claiming superior lube properties, and I hear similar praise from people I know who use it. My daily driver is a '91 Firebird Formula with the TPI 350 engine and 700-R4 auto trans. I change the oil about every 3,000 miles, and since I know the previous two owners, I know they took similar care of the car. The engine is mostly stock but it has almost 150,000 miles. I've heard that high-mileage engines shouldn't be switched over to synthetic oil. Is this true, and if so, why? I've been told that older engines may start to leak if you switch them to synthetic. Is this something I may have to deal with?