Q I just got done installing a brand-new 502 crate engine in my Elky, which runs great by the way. The oil pressure at an idle is around 15-17 psi. I called GM, which referred me to my local GMPP dealer, where several people said that is normal. They agreed with me that it was low, but they were told that is what they have seen in these engines. Is that correct? It comes up as you get on it to about 40-45 psi max, but it's at an idle that I get really scared. Can you guys shed any light on this? I'm using the correct oil (10W-30) as recommended for the first thousand miles. Any suggestions?
A First we'll start with the GM party line. The normal hot oil pressure spec with 10W-30 for your 502 crate is (are you sitting down?) 6 psi at 1,000 rpm, 18 psi at 2,000, and 24 psi at 4,000! The manual says this is the normal spec. I certainly wouldn't want to see the minimum. Now let's go over our experience with these engines.
Back in '98, we screwed together a '71 Chevelle and installed a 450hp/502 crate and a TH700-R4 with a set of 3.73:1 gears. Over the past 10 years, it's been on at least six full Long Haul Power Tours without missing a beat. It now has at least 45,000 miles on the clock. The car runs high 12s all day long and knocks down 14 mpg on the open road at 70-plus mph. It's a very fun car to drive and kills the tires at will! Now for the oil pressure. It's right in line with the same pressure you're seeing with your engine. This is also with 10W-30 oil. Why I left the engine alone is that during this time, we were doing a lot of contract work for GM Performance Parts. We wanted to see if this type of pressure would cause any issues. Well, after 45,000 miles and cutting filters open on every oil change, we're here to say that your 15 psi at idle and 40/45 psi at cruise is just fine.
What would we change? If you remove the oil filter, you'll notice an oil filter adapter: a little threaded nipple which will thread out of the block with a 9/16-inch Allen wrench. Directly under this nipple is a check valve in case the factory oil cooler gets plugged or damaged. If you're not using the factory cooler, you can remove this check valve to eliminate four 90-degree turns that the oil must make to get around this check valve and increase the oil pressure by at least 5 psi. It will also lower your oil temperature slightly.
Also, we'd recommend 10W-40 engine oil. Big-block engines, with their long stroke and large bearing journal diameters, create a good deal of heat, which translates into high oil temperatures. It will love the slightly thicker oil. The Gen VI big-block also has a good deal of oil bleed through the lifters to lube the net-lash rocker arms and to keep it cool. This is another reason the hot pressures are slightly lower than you'd expect.
After all of this, we hope you've found some comfort in your oil pressure readings. These engines are just about indestructible. They are a blast to drive. Have fun in your Elky.
Q When mixing and matching main bearing halves for proper clearance, should I be concerned about where I put them? Should changes be against the main caps or the block webbing? Or doesn't that little bit of misalignment matter? Also, when painting the block, do I have to worry about overspray in the freeze-plug holes creating insulated hot spots? Thanks for your time.
Eau Claire, WI
A When fitting main bearings, we always try our best to keep the standard oversize bearings in the main caps and adjust the upper shells in the block to adjust bearing clearance. If you think about it, we line-hone blocks to bring the main saddles into perfect alignment and then place the over-/undersize bearing shells in the main caps. If, for instance, you install an undersize shell to tighten up the clearance in one of the five mains, this would be the first place the crankshaft would contact when you have a loss in oil film. That shell would be 0.0005 inch closer to the crank than the rest of the shells. Sometimes you just can't do it and you need to install both upper and lower shells of a 0.001-inch-under set. Hopefully when you have to do this it's because the crankshaft is slightly undersize, and then everything is back into alignment. Good thinking, though.
When swapping out shells for clearance, you must stay with the same manufacturer and design. For instance, Clevite 77 offers many series of bearings depending on the application. The standard street-performance bearing is the P-series, which has a soft flash plating to aid in embedding debris without causing bearing troubles. These bearings also have a low level of eccentricity, which means they have extra clearance close to the parting line to retain oil for engine start-up. Next, we come to the most popular engine bearing for high-performance and drag racing, the H-series. These bearings have a medium level of eccentricity and do not have the flash plating, resulting in better seating. Also, these bearings have enlarged chamfers for greater crankshaft fillet clearance. This is what makes these bearings most desirable. We used to have to mock up standard bearings in the lathe and cut the bearings for extra clearance for the fillet. Now they just fall out of the box! As long as you stay within the series, you can swap shells around for the perfect fit.
After building engines for over 36 years, I've never seen a problem by painting a block and getting overspray into the water jackets. Obviously, if you have a concern, just mask off the freeze-plug holes before painting. Thanks for your questions.
If you have technical questions for Kevin McClelland, send him an e-mail at firstname.lastname@example.org.