Dead End Big-Block
I built a 440 stroker engine for my Challenger. The specs are: 4.350-inch bore, 4.250-inch stroke, 7.100-inch rods, Icon 2618 forged -17cc dish pistons with .005-inch wall clearance, Total Seal moly conventional rings, 440 Source aluminum heads (CNC ported and milled .050-inch, a Comp cams hydraulic roller XR292hr-10, 1.6 roller rockers, a Street Dominator intake, and a Holley 950 Ultra HP carburetor. The engine has 215 pounds of cranking pressure, and I'm using 20/50 oil with75 pounds of pressure, and the timing is set at 36-degrees total.
When started cold, the piston slap is very loud, but goes away when warmed up. After driving to shows and cruises every night, the engine started to burn oil, and is getting worse each week. By summer’s end, it was smoking badly. I checked intake gasket, head gasket, valve seals, pcv, and they all checked ok. I took the engine apart to find the thrust sides of pistons and cylinders scored. Are forged pistons not recommended for street use with continuous expanding and contracting? What street friendly piston can handle estimated 600 horsepower and 600 lb-ft of torque? Can Mahle 4032 forged pistons with .002-.003-inch clearances handle the power? Would a shorter rod with longer piston combo work better? I need it to last longer than one summer.
Dave Davies - Via email
Dave, I think your expectation that the engine last more than one summer is more than reasonable. In fact, it should last for many years, even with hard use. The parts you selected are very good, and it should have been a nice durable engine combination. There is no problem at all running forged pistons in an application like yours. Those Icon pistons should be nearly dead quiet. The long rods you used did result in a shorter piston skirt, but at the same time the rod angle and side loading is reduced. I can assure you that a shorter rod isn’t the solution to your problem. The parts you used are a proven combination.
The first clue of what might be going on was the piston slap when the engine was fresh. To me this indicates that the piston to wall clearance was never correct. In fact, the cylinders are what I suspect is the source of the problem, and there are numerous machining errors that can cause premature wear, including out of round, taper, improper surface finish, or neglecting to detail the bottom of the bore. Unless you ran the engine out of oil or seriously overheated it, I would put this one squarely on the machinist and engine builder. Believe me, I have seen plenty of freshly machined blocks that I wouldn’t put together to run in a garbage truck.
I have a ’70 440 block, verified by the casting numbers. At the moment, I do not know the head casting number. I put this engine together in the late ’70s with pieces purchased from the local speed shop. I got it running, but it never ran right. It always had a vacuum leak that I couldn’t find, so it got stuck away as life got in the way and time became way too short. Fast forward 20 years, and I tried again. The intake appears to have a gap at the valley so I tried swapping intakes with the same results. These were Chrysler Six Pack intakes, and one was aluminum, and one cast iron.
I’ve been a subscriber for a long time and don’t remember seeing or hearing anything like this. Is the block decked, or heads shaved? I don’t have a 383 intake to try. Is it possible a 383 intake would fit?
Bill Deeter - Via moparmuscle.com
Bill, if the engine is a 440, the low deck 400 or 383 intake will not fit. There is really no way you can mistake the two. You need to check alignment to see if the manifold fit is causing the problem. The best way to do this is a trial fit with no gaskets, using a known good intake manifold. Lay the intake squarely in place and feel if “rests” evenly on both heads. Worst case scenario, if it rocks, something is way off and there are problems with the heads, block, or manifold. Next, do a careful inspection at each corner of the manifold and heads with feeler gauges to see if the intake sits unevenly. Also check for gaps at the top of the flange versus the bottom in the lifter valley. If a gap is showing on either top or bottom, there is an angular mismatch between the face of the heads and the intake. Corrective machining of the heads or intake is the only cure.
If the measuring and inspection shows the manifold off front to rear at the corners, something is machined out of parallel, or possibly the dowel pins were left off the decks. The block’s decks, the heads, the intake face or any combination of the three could be machined out of square. Such error in machining is all too easy if the machine work was done carelessly, or without the appropriate fixtures.
Look through the bolt holes, and note the position of the threads in the heads relative to those in the intake. The manifold should be low on the heads, as indicated by this alignment, by roughly an amount equal to the total gasket thickness. If the bolt holes are centered with the threads, or high, the manifold needs to be milled to correct the alignment. I think if you go through this careful inspection process, the misalignment can be tracked down pretty quickly. Correcting it, though, can be tricky even for a good machinist.
I'm looking at getting a Sonoramic long ram intake for my ’71 Chrysler Newport. The car has a factory 383HP that is bored .030-inch over, and the compression ratio is 9.5:1. I also have a Comp Cams XE 268 cam and 440Source heads. What style of carburetor would be best for this engine? My two direct comparisons are the Edelbrock versus the Holley. Edelbrock has carburetors specifically for dual-quad applications, but Holley also has some small carburetors in vacuum-secondary form. I know that I will not be gaining any performance, but I want the look without over/under carbing the engine. I believe I have to stay with 500 cfm or lower.
Dan Gilewich - Via email
The way I see it, outside of restoring a set of OEM carburetors, the Edelbrocks are the way to go. These units much more closely resemble the stock units, and since you are primarily going for looks, they are much more appropriate. To me a set of Holley carburetors would look completely out of place on that induction unit. Get the 500-cfm dual-quad units and a pair of tuning kits, and you might be surprised by the responsiveness of your ram inducted 383.