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'67 392 Hemi GTX - FAQ!

Please note: This page is out of date (the current configuration of our '67 GTX is quite different from what is described below), but there is still some good information here.

Crowbarring the Hemi:
Here's a copy of an email exchange between us and Jesse Holling. Jesse is wanting to put a 392 in a '70 Challenger with power steering and power brakes. If you have additional suggestions for him, please email him directly.

We hope you find some useful information for your 392 application! If you have additional questions, .

At 05:01 PM 3/10/97 -0800, Jesse Holling wrote:
I stumbled across a complete '58 392 Hemi that just had a quality fresh rebuilt with stock intake and exhaust that I couldn't pass up and will be getting in a few weeks. I am considering putting it into my '70 Challenger that has PS and PB and hope you have a little time to help me determine the viability of this project.

I've spoke to QEC in Oregon, a local racer, a few MMLers, and a Rick Clapham in Denver and all indicate the transplant is do-able but with conflicting answers on a three main issues (PS very close to the #3 cylinder exhaust, PB booster close to head, and can use small block isolators/mounts on stock motor mount location without needing modification).

From your given pictures, it looks like you needed to modify some already made headers to get around the PS box. Was this a good solution and who's exhaust did you use?

My Challenger is a 4spd. I understand the 392 cranks didn't come completely drilled for a pilot bushing. Did yours need drilling or did you put a pilot bushing in the flywheel which has been suggested to me?

Also did you have to modify the motor mounts or could you just use small block motor mounts that were swapped left for right?

Lastly, the cam in this engine is a 270 duration w 430 lift (I don't have the @50 or overlap numbers yet). I am considering something with a little more lift while still getting a mild lope a idle. I noticed a 280 dur, 480 lift in your 392. Does that one give big car shaking at idle with little vacuum or is it a nice street mix?

Here's our reply:

Here's what I have done, plus some things I know or have found out from others.

I think you have a great idea. As a matter of fact I had wanted to find an E-body, Challenger preferably, when I found my GTX.

First of all, the 392 is actually wider engines than the 426, about a 1/2" or more, I think. It is a tight fit in the GTX engine compartment. The power steering unit (PS) is quiet a bit larger than the manual box, and does cause clearance problems with any kind of exhaust. I think the stock cast iron manifolds would clear, but I never tried them. They are not what one would want on a performance engine. I have tried the truck manifolds which are a lot better than the car manifolds, but they will not fit without raising the engine quite a bit.

The headers used were Hooker's for Chevy Big Block engines. They have 1 7/8" diameter tubes. The Chevy flanges were removed and 392 flanges were added. The port spacing was close enough that the passenger side tubes while still welded to the collector could be convinced to match the 392 spacing. It has been several years since I modified these headers, so I do not remember all the details. The photo on our Web page, "Engine out of car", shows the headers with an extension on the collector side. I removed the original header collector flange and welded a length of 2 1/2" elbow, because I though it would be a good idea to get the flange connecting to the exhaust pipe down where it would be easier to bolt and unbolt. Adding them did cause a slight problem.

When I first made mounts (the K-member portion) for the 392 (more later) I left the GTX's big block K-member motor mounts in place for later conversion back to a 440 if I wanted. The 392 mounts were directly in front of the 440 mounts and, in fact, welded to the 440 mounts where they met. Anyway, when my wife (Julie), son (Jimmy) and I attempted to install the engine with the newly modified headers and the transmission bolted up, it would not go. The newly added extensions hit the 440 mount on the driver's side. We recovered from that by removing the passenger side header. We removed it because it would be the easiest to replace after the engine was installed. The driver side header bolts are much harder to get to because of the - you guessed it - power steering unit. We did not try removing the transmission, so I do not know if that would have worked.

Otherwise, the main problem with the passenger side, same is true for the driver side, was forming the header tubes to fit the 392 exhaust port shape. The header outlet bend that I added continues the block hugger concept and runs very close to the oil pan on the way down and back.

Now the driver's side. The headers as purchased were configured such that the passenger side tubes joined mid-flange (between cylinders #4 & #6) front to rear. The driver's side tubes were collected at the rear of the engine, under cylinder #7. Since the starter is mounted on the driver's side this required the header to be completely cut apart for reconfiguring the tube arrangement. This was quite a job especially for someone who did not have good welder and very little welding experience - none welding thin material. To make a long story short I did get the header back together. The starter can be removed with the header installed. I did end up needing a short section of tubing to complete the refab job. (Note: There may be other headers that would be better suited for this job. I did not check. Someone had told me that the Chevy Big exhaust port pattern was fairly close to the 392 pattern, so I went with them.) As you noted in your E-mail I still have to do some creative forming to clear the PS unit. The way I ran the individual tubes required denting the # 1 & 5 tubes. The tube for cylinder # 3 was tucked in tight and did not require modification. The # 1 tube runs directly over the power steering unit and required the heaviest modification. This was in part due to the motor mount design I had used (more later). The header tube would not go between the PS unit and the motor mounts, 392 & 440. Also the length of tubing for #1 would have be considerably longer to go any but the most direct route. The #5 tube could possibly be left undented if the motor position is right.

Even with the creative forming the engine is sitting a little high in the front to get clearance. The intake is not level. In addition the engine is little offset to the passenger side. Regarding height, the engine is a tight fit under the stock hood. Using the single plane two-four intake with a 5/16" thick spacer for the 6-Pak setup clears okay, but I have not measured to see by how much. The stock dual plane manifold is taller and might not clear. I would measure the clearance for you now, but the hood is off the car. I have started a major project which includes making new motor mounts and building a set of equal, full length headers.

Now, more about motor mounts. I have never tried the small block mounts. I did not know to try them when I built my first set. My first set were built to mount the 392 in a GMC (Yuck!) 4x4 truck I had. I used these same mounts with minor modifications when I put the 392 in the GTX. The motor mounts were built to use rubber isolators from Chassis Engineering. The isolators were positioned horizontally not at an angle like the stock small and big block isolators. Would the stock small block mounts work? I don't know, but I suspect you might still have a problem with header clearance and routing. It would be worth a try because building special mounts takes a lot of time. Good luck. The new motor mounts I am building will still use the Chassis Engineering isolators, but they will extend approximately 3" farther down toward the K-member than my first set. The isolator will also be farther away from the PS and closer to the engine. This will allow room for the #1 header tube to be routed down and then around the PS unit on the engine side. The new mounts should be complete and installed in a couple of weeks, hopefully less. Then comes the chore of building the headers.

I have talked with "Headers by Ed", and he has convinced me that equal length is very important if you want to get the most out of your engine. So that is what I am going to shoot for. I think its going to be a very difficult task. You might want to check back in a couple of months and see how things went, or are going, whatever the case might be.


My cranks did not come drilled for the 4-speed pilot bearing, so I did use a flywheel mounted pilot bearing for a while. When I later was getting ready to install another 392 in my GTX I had the crank drilled for the pilot bearing. The flywheel mounted bearing worked okay, but in addition to not being the correct diameter the crank hole is also not deep enough for the transmission input shaft. You either have to cut off the end of the input shaft or drill the hole deeper. I recommend drilling the hole deeper and installing the pilot bearing. The reason I did not was that I did not want to disassemble the engine at that particular time. (The GMC has automatic and therefore this was not a problem.)


The 280/.480" cam I have been running sounded and worked great. You should not have any problems. My engine is currently disassembled. When reassembled a 294/.510" cam is going back in, so you can see that I did not think the 280/.480" was too much.

I would be interested in hearing about your progress on your 392 Challenger. The installation except for the exhaust manifold/header problem is really pretty simple. Good luck! -- Jim

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How is your 392 setup?

Please note: This page is out of date (the current configuration of our '67 GTX is quite different from what is described below), but there is still some good information here.
  • 11:1 Jahns Pistons
  • Bored 0.060" Over
  • 440 - 6 Pak Holley Carburetors
  • K&N Filter
  • Adapter Plate Mounted to Weiand 2x4 Aluminum Intake
  • 2.125" Intake Valves (Sterling, w/11/32" Stems) (to be installed soon)
  • 1.880" Exhaust Valves (Sterling, w/11/32" Stems) (to be installed soon)
  • Hardened Exhaust Valve Seats
  • Bronze Valve Guides
  • Heads Mildly Ported, To:
  •     Smooth Sharp Edges
  •     Reduce the Size of the Valve Guide Bosses
  •     Blend Valve Seat to Pocket Transition
  • A833 4-Speed, With Coarse Input Splines
  • Centerforce 10 1/2" Dual-Friction Clutch Assembly
  • 4.10 Dana 60 with Suregrip
  • 275R50x15 B F Goodrich T/As
  • 1 7/8" Block Hugger Headers (Currently)
  • 2 1/2" H-Pipe
  • 2 1/4" Tailpipes
  • 2 1/2" DynoMax Super Turbo Mufflers
  • Mopar Performance Electronic Ignition
  • MSD 6AL
  • Mallory Promaster Coil
  • Carter HP 100 GPM Electric Fuel Pump (but wouldn't recommend it - too loud!)
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