Engine Build - RPM Short Block - Budget Build

Instead of searching for a 360 and having it rebuilt, we got a rebuilt short-block from RPM Engines. Even after paying the $110 core charge, the price was $678-significantly cheaper than a rebuild. The engine includes Federal-Mogul bearings, Badger cast pistons, a Dynagear timing set, a Melling cam, Sealed Power rings, and Pioneer brass freeze plugs. Virtually any American V-8 short- or long-block is available from RPM.
Instead of searching for a 360 and having it rebuilt, we got a rebuilt short-block from RP
The first thing we did with the RPM short-block was use our Powerhouse dial indicator and deck bridge to determine the piston deck height so we could calculate the compression ratio. The deck height varied from cylinder to cylinder due to the use of several rod castings-Chrysler wasn't known for killer production tolerances, anyway-but the average was 0.100 in the hole. Combine that with the 11cc dishes in the pistons, 0.041-inch-thick head gaskets, and 75cc chambers, and it's easy to see that a 360's compression can be as hideously low as 7.5:1.
The first thing we did with the RPM short-block was use our Powerhouse dial indicator and

Our goal was 9.0:1 compression, so we spoke to the Mopar specialists at Hughes Engines for advice; they ran our combo through their computer to determine mechanical compression ratio versus cam timing to deliver a goal of 165-psi cranking pressure. They milled 0.070 off a set of 596-casting heads we provided to achieve chamber sizes of 51 cc's. While Mopar Performance offers 0.028-inch gaskets to increase compression, the Hughes combo would deliver about 9.0:1 with regular 0.041 gaskets.
Our goal was 9.0:1 compression, so we spoke to the Mopar specialists at Hughes Engines for
After pricing cylinder-head rebuilding at local machine shops, we opted to choke-up the extra change to have Hughes perform its Pro Pocket Stage 1 portwork to the heads (seen here in the exhaust port) in addition to the rebuild. The porting makes the heads flow well up to 0.500-inch valve lift-stockers give up at 0.350 lift. Hughes' advice and patience was also invaluable.
After pricing cylinder-head rebuilding at local machine shops, we opted to choke-up the ex
Hughes also had the heads cleaned, magnafluxed, and shot-blasted, then pressure checked them after porting. The pro valve job included new 2.02/1.625 valves, 11/32-inch bronze guides, new Hughes springs matched to the cam, new retainers and keepers, Viton seals, and a complete balancing of valvespring pressures and valve tip heights. Hughes angle-cut the intake surface to compensate for the 0.070 milling, and the intake ended up fitting perfectly. The heads dented the budget, but we were happy.
Hughes also had the heads cleaned, magnafluxed, and shot-blasted, then pressure checked th

This is what we look like when we're voiding the warrantee on our new RPM engine by swapping in a performance camshaft. The 'stick is a Hughes Engines grind that takes advantage of the greater rate of lift per degree of cam rotation allowed by Mopar's large- diameter lifter foot. The hydraulic grind is a Hughes HE2430AL spec'd at 0.504/0.515 lift with 1.5:1 rockers. Our stock rockers proved to have 1.38:1-1.43:1 ratios, so true lift was closer to 0.480/0.490. Duration at 0.050 tappet lift is 224/230, and the lobe-separation angle is 110 degrees. We didn't actually coat the cam with lube until final assembly.
This is what we look like when we're voiding the warrantee on our new RPM engine by swappi
We used our Powerhouse dial indicator, dial-indicator stand, and Pro Crank Socket with a Lunati degree wheel to check the cam and found it about 3 degrees advanced when using the RPM-supplied timing set. We also plotted the cam-lift curve, then checked valve-to-piston clearance at every point in the curve.
We used our Powerhouse dial indicator, dial-indicator stand, and Pro Crank Socket with a L
To solve the cam-degreeing problem we used Mopar Performance's P4286500 offset cam-key package. We installed the keys such that the cam was rotated counter-clockwise in relation to the cam gear, thereby retarding it. We had to redegree the cam twice before we found the key that set it at Hughes' recommended specs.
To solve the cam-degreeing problem we used Mopar Performance's P4286500 offset cam-key pac

Here's the bigger problem: The valve-to-piston clearance was too tight thanks to the head milling. The intake valves got as close as 0.013 to the piston at 10-25 degrees ATDC, and the exhaust was 0.020 at 10-25 degrees BTDC. Hughes recommended 0.080 on the intake and 0.100 for the exhaust in this application. Here's how we fixed it: First we marked the pistons with a Marks-A-Lot, then installed the heads with checking springs on them. We brought each piston to TDC, then pressed the valves into light contact with the pistons to mark them. Once the head was removed, we drew the shape of the valves on the pistons, then used a carbide bit to hand-cut valve reliefs. During grinding, the engine was sealed in a plastic garbage bag with a duct-taped hole only around the area to be ground.
Here's the bigger problem: The valve-to-piston clearance was too tight thanks to the head
Here's what a finished piston looks like. We ground the reliefs deep enough that we could switch to 1.6:1 rockers and still have clearance. Even so, the nastiest cut was only 0.075 deeper than the top of the piston. That's less than 5/64 inch, if it makes you feel any better in those terms. It was scary work, and it took a bunch of time and patience to double-check every valve, but it was worth it.
Here's what a finished piston looks like. We ground the reliefs deep enough that we could
The next issue was pushrod length. With milled heads and the smaller base circle of the bigger cam, you always need to check it. We bolted on the rocker shafts and used a wire feeler gauge to check the preload of a pair of lifters resting on the base circle (that means both valves are closed) and found it to be about 0.040, which is OK. If the lifter preload is too much, you can cut thin spacers out of sheet aluminum or steel to put under the rocker shafts, or get custom pushrods. Our rocker geometry was pretty bad, but we didn't do anything about it.
The next issue was pushrod length. With milled heads and the smaller base circle of the bi

It can wait until after you've prelubed the engine, but don't forget to install the distributor/oil-pump driveshaft. There's a brass bushing in the block for the 'shaft, and it pays to make sure it doesn't need to be reamed to fit before the engine is assembled. Before final assembly we brought the number-one cylinder to TDC on the power stroke to simplify initial timing settings, then lubed the cam and didn't rotate the engine until it was ready to fire up.
It can wait until after you've prelubed the engine, but don't forget to install the distri
We used the intake that was on the nuked 318 that came with the car--an old Edelbrock Torker 340 with ports way too big for the 318. It matches the 360 ports, and while a dual-plane is not preferred by Edelbrock for street use, we figured it would be acceptable with the cam, manual trans, 4.30:1 gears, and light vehicle weight.
We used the intake that was on the nuked 318 that came with the car--an old Edelbrock Tork
For final assembly we used a complete ARP engine and accessory fasteners kit. It's a bit of a luxury for a budget buildup, but it pays for itself by eliminating the hassle of trying to find all the right bolts. We opted for the black-oxide six-point bolts-much preferred to the stainless 12-points, in our opinion.
For final assembly we used a complete ARP engine and accessory fasteners kit. It's a bit o

A 273/318/340 oil pan (right) won't work on a 360 (left) because the size of the rear-seal area is much smaller on the 360. We bought a PAW chrome pan, sandblasted it, and painted it to cure the problem.
A 273/318/340 oil pan (right) won't work on a 360 (left) because the size of the rear-seal

Rumpity engines equal big glory, noise, and tire smoke, so that's where we spent the most time and money with this budget buildup. The Duster came with a 318 that was seized thanks to a brutal overheating, and it would have been most practical to replace it with another one of the die-hard little mileage masters. But we're not really into practical, and we wouldn't have felt right if we didn't at least try to make serious power.

The solution was to step up to a 360, spend as little as possible on the short-block, and put our bucks where the cachongas live: compression, heads, and cam. The result was an engine investment of $3,427.65. If that sounds high, remember that some magazines consider $5,000 cheap for a motor, and they don't include all the little stuff such as paint, gasket sauce, dang-it small stuff, and things you break and buy twice. We did. Read and learn.

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