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Compressed Cubes

Squeezing 74 more inches in a 318.

John Stunkard - June 07, 2012 10:00 AM

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We found out that the seats would have to be milled for the needed clearance with the 1111 spring set. In the interest of time, we instead opted for a set of springs from COMP that Hensley had on hand. Obviously, the matched 1111 spring is the optimum choice for the Whiplash cam to get the most rpm out of it; Dave said we will probably need to address the problem of the lower spring pressure, so we’re considering our options…

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For break-in, we are leaving out the inner coils to prevent damage to the cam during the run-in cycle. The careful measurement coupled with calculated numbers resulted in finding a true spring pressure of 315 lbs-ft installed and a max lift of .612-inch prior to coil bind.

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Jack soundly raps the newly-installed cylinder head springs with a rubber mallet to make sure the parts are all seated properly. You do this because you really don’t want your spring and valvetrain set-up to come apart by accident when you first start your motor.

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New Cometic head gaskets helped us get the compression down to a pump-gas friendly 9.48:1. Ours were C5633-070, a .070-inch thick version for the 318, and are made from a carefully-selected multi-layer stack that is riveted together. We laid it on the engine to ensure all the bolt openings and water jacket ports lined up. Permatex 80065 sealant was sprayed on them for final installation.

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As mentioned in the text, torque readings on a multi-stack head gasket install should be double-checked; wait 10 minutes, redo the initial spec, and then step to the next increment (in our case, 70 lbs-ft/80 lbs-ft /90 lbs-ft). We also used new ARP head bolts for safety.

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This is how the installed Hughes rockers and pushrods look; a guide plate is used to prevent the pedestal-mounted rocker roller from moving off the top of the valve, resulting in possible breakage.

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Made by Edelbrock and marketed by Hughes, the guide plates have large bolt openings so they can be tightened down part way and adjusted for clearance based on the specific cam specs. A light hammer tap sets them into proper alignment and they are torqued down.

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A dab of lithium lube is placed on each pushrod and valve before the rocker is fully installed.

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This is the adjuster lock that holds each rocker at the proper lash spec. They will be checked again during the run-in process, and redone when the inner springs are installed following run-in. Due to the hydraulic cam, they will not need to be adjusted again after that.

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This is the second tube of special assembly lube that Hughes includes with the cam; we used the first to coat the lobes prior to installation; the second one is squeezed onto the cam near each lifter base for added insurance at start up.

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Here is the Edelbrock intake from Mancini Racing; our QFT (Quick Fuel Technologies) 680-cfm carb is on it. QFT had sent us their dual-feed line, a braided steel version, which really helped clean up its appearance. Jack made sure the intake was square and then milled an extra bung to allow us to install both the heater hose and the water temp reader.

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The AirGap is actually the same height as the RPM intake. The difference is the lowered floor on the AirGap.

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Proper intake sealing is critical; the ends can be filled with silicone if there is a small gap, but in our case, we needed the cork pieces from our Mancini-supplied FelPro kit. Jack used yellow “gorilla snot” weather seal on the ends; that cork is not going anywhere with this stuff on it.

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The square ends of the cork should be liberally filled with RTV-type gasket sealer to make the corners seal. A blob should squeeze out when torquing the intake down.

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We got back to work on putting the rest of my new 392 wedge engine together.

As we told you last issue, this was a standard 318 block that had been prepped by Hensley Racing for a stroker bottom end. That came as a complete 318 kit by Mancini Racing that pumped the small block to the legendary displacement of 392 cubes. We covered that; now we will get to put the rest of the top of the engine on, using some pretty trick parts.

As we have mentioned several times, Hughes Engines played a big role in what we ended up using for valvetrain parts. Dave Hughes has spent years pushing the envelope on street cam design, using larger blanks to create valvetrain parts that function specifically in the Chrysler engine environment. To that end, he sent us a HEH2832AL Whiplash kit, a hydraulic model that would feature .558-inch intake and .576-inch exhaust specs.

Coupled with new 1111 series springs, it would make a pretty complete package, as Hughes had previously sent us PRW’s special stainless-steel 1.65 ratio rockers, 5/16-inch .083 wall, 7.550-inch oil-through pushrods, lifters, and Edelbrock guide plates. The rockers are pedestal-mounted like Magnum rockers, as the AAEQ heads are a replacement version for that engine. Hughes had previously prepped the hardened seats for us.

We ran into one issue – the heads were prepped for our previous single spring layout and we found the 1.800-inch installed inner-spring height of the new 1111 versions Hughes had sent us were not possible without cutting the seats again. As an alternative due to time, we opted for a set of COMP springs of similar construction and spring tension that had an installed height of 1.700-inch and shimmed the seats, which had been cut to 1.760-inch for the previous single-coil spring install. Jack Moore, who was doing the assembly, carefully measured everything and found the replacement dual-coil spring could handle up to.612-inch lift without binding.

The COMP units off the shelf from Hensley were also a double-coil design with a little less open spring pressure (295 versus 320), but we would have stayed with the all-Hughes combination under other circumstances. We might still end up with issues due to the high lift versus open spring pressure; one alternative will be to switch over to the 1.5 rocker outfit Dave offers. For now, we will take responsibility for whatever mayhem results.

The trick to installing these parts was taking our time. Jack Moore, who was putting the engine together for us, had not used the Hughes pieces before. As he progressed, he was frankly impressed with the way the design was laid out. The main ingredient in the formula is lubricating the pushrods to make sure the rockers stay wet; lots of oil and lithium grease came into play here to make sure everything worked as it should.

We were concerned about compression; with a standard shim gasket, it would have been above 11.0:1. We found that we needed about .070-inch to get it down to 9.5 (9.48 to be exact). These came from Cometic, whose C5633-070 gaskets are a riveted stack; Jack says in big-block apps they sometimes need to have the rivets removed and be single-layered back onto the engines (not much fun without studs). After using Permatex 80065 spray sealant for insurance, he checked them to make sure everything lined up right.

Now, the heads are torqued to 70lbs-ft to start, but Jack has found it wise to let the torque setting “settle” the multi-piece gaskets; therefore, he will wait five to 10 minutes and hit them all at 70 again to make sure they are tight. Often, one or two will still need the wrench again, which might be the gasket stack compressing. Once the wrench clicks at 70 without hesitation, he will draw them to 80 lbs-ft and wait again. Double-check the 80s and finish at 90. One big plus to our pedestal-mounted rockers is that re-torquing after warm-up will not require disassembly of the valvetrain.

There was one other thing we needed to address. The Edelbrock RPM intake we had was slightly mis-milled; which was why we had run into leakage problems so often; Jack discovered this as he began the work of prepping it for reinstallation. We could have milled it down, but since the rest of this motor was basically new, we looked at our options. Mancini Racing Enterprises has been our go-to source for almost everything, and they did have a new Edelbrock RPM AirGap for us to use. It looks good, but most importantly, this design will eliminate having the hot oil on the bottom of the intake runners.

Here we go. Thanks again to everyone who helped make the 392 Wedge project a reality.

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