The Hemi Rebuild - Dual 4bbl Carb Power!

Well... I can honestly say with my hand on my heart that I never thought I would have to make a page like this, but, as most of you reading this know, it's not all roses in the custom car game. Big boys toys can come with big boy problems. Sadly, with only a mere 2,000 miles on the odometer... the 540 Hemi started to make a faint "knocking" sound. I picked up on it early and knew something wasn't right and stopped driving it immediately. It wasn't a loud "bashing" knock, but enough to signal the engine wasn't happy.

I limped it to Henrys Rod shop to see if they could help me figure it out. With some advice from the original engine builder (Tim Banning) he suggested we try a valve cover space kit as it sounded like rockers hitting the valve covers, after several weeks waiting for the kit to land, sadly it didn't cure the issues. Worth a try though.

Next we tried to replace the flex plate as it sounded very close to this area. Brand new plate in, ARP hardware and installed to spec, but sadly, the noise was still present. With these external engine remedies failing to cure the issue, Henry's and I knew there was only one real way to get to the bottom of it... pull the engine out and tear it down. Gutted.

A week passes and the Hemi is out, on a stand and off to a local Automotive engine / machine shop in Tauranga to tear it down. Long story short, it remained here for nearly 4 months, yes 4 MONTHS and all that had happened was a disassembly. I chased them up, went in, called, but just a lot of talk, excuses, and no movement. Nice enough people so they will be saved the embarrassment of being called out. The time was one factor and appalling, actually terrible, the other was they felt and seemed way out of their depth with Hemi experience and really had no idea. 350 Chevs and similar seemed like their area of expertise limits.

I made some calls and talked to a good Mopar friend (Wayne) who owns, races and has a lot of real world experience with Hemis. He recommended two places, one being Marsh Motorsports. I called and instantly felt at ease. Loud, happy and a bit full on but I felt confident. They had worked on many Hemis and had all the machines in house. In NZ, there is literally only 2-3 options so, I had to just go for it!

Tony Marsh (the Father / original owner) has a lot of history in NZ drag racing, in particular with Hemis and set many records. Marsh Motorsports also built the current fastest naturally-aspirated small block in the world. Between Wayne, Marsh's records, customer feedback, their Facebook page following and their history, I was sold and trusted my gut and to commit to the build with Marsh Motorsports. That's the best way to do it, do your research, find the shop that suits, don't overthink it or second guess, back them, yourself and commit!

I collected the Hemi from the Tauranga Automotive shop and took it up to MArsh Motorsports. After being handed a disassembled pile of Hemi parts, within a few weeks and in between other builds, Marsh Motorsports had a closer inspection of my engine. Conclusion: they said without a shadow of a doubt, it was "cylinder / bore wash". All cylinders had a decent amount of gasoline go through them and clean off the protectant layer of oil, leaving the pistons and rings to scuff.

The pushrod holes were also not big enough, allowing the pushrods to make contact with the holes themselves along with skimping on various items like timing chains and smaller parts that I had no say in. The pushrod contact was more than likely the "knocking sound". These were all thankfully picked up by Marsh Motorsports who rectified the issues using high quality parts. My crank, camshaft, valves, springs, lifters, etc were all in perfect condition (only 2,000 miles on it) so thankfully, it was mainly pistons and rings to buy.

The main damage (cylinder wash) can be caused by faulty injectors, poor tune, poor break in procedure or all of the above. I was truely unaware of how bad it can be and the damage fuel wash can cause to an engine. This left a very sour taste in my mouth from the EFI experience. YEs, it can happen with carbs but with so many parts to an EFI system, it's more susceptible to these types of issues.

My EFI always felt slightly out and had some idle / throttle issues but overall, ran pretty well. Running well or not, sadly, at any stage, fuel wash caused by faulty injectors and/or ECU issues can happen. I'm not about to put myself at the hands of an ECU in this car again. With this in mind and a lot of research and consideration, I decided to go back to the Challengers muscle car roots and go for dual 4bbl carbs for the fuel feeding.

That's right! Carburetors! The majority of muscle and classic car owners still run carbs for a reason - simplicity. Less parts to go wrong. sure, EFI can run smooth (when dialed in) but when (not if) they malfunction or you have issues, trouble shooting them is a nightmare. Laptops or tuning shop required, so many parts to query, injectors, leaks, fuel rails, ECU problems, the tune itself, throttle bodies, IACs, the list goes on. With carbs, if there is something fuel related, it's the carb. That's it. In some cases, a simple screw driver will see you right or on the way home.

I considered this carb vs. EFI debate long and hard, research, soul searching, asking myself what the car wants and I know I 100% made the right decision. This is a 1970 muscle car, having carbs is part of it. I love my carbs, less crap, very similar driving experience with the added bonus of simplicity, ease and peace of mind. Two 4bbl carbs also just look fucken mean on top of that big ole Hemi! Lots of people are switching back from EFI to carbs. Seems the grass isn't always greener.

Carbs tuned right are on par with EFI for power and response, often making more power than their computer controlled competition, however, for some and in most debates or discussions on which is better, there are 2 main "cons" for running carbs that pop up more often than not. They are: fuel vapour lock (heat soak) and cold starts.

With vapor lock, your fuel line heats up after a long drive and if you go to fill up your car for example, the 10 mins you spend allows the heat of your engine with a mechanical fuel pump on the hot engine block to literally turn you fuel in your lines and bowls into vapour form and make it extremely hard to start. It literally goes from liquid to gas form and with no fuel in the lines, you're going to have a hard time starting or bringing getting it to flow again. Embarrassing at a busy petrol station forecourt mid-summer / holiday season.

Fuel vapour can be fixed by a carb spacer to distance the carb off the hot intake which helps a little but isn't a fix by itself. The best remedy is an electric in tank fuel pump. I already had one for my EFI setup and being in a cool gas tank far from engine, it has zero heat issues and because of the constant electric pump pressure, the fuel flow is instant.

My original 440ci Magnum had a 4bbl which had a mechanical pump on the block and on long drives and in summer temps, I suffered from my fair share of heat soak moments. As annoying as they are, there is a solution so that is no longer a "con" for carbs. In tank pump and carb spacer. Done!

As for cold starts? For me this was never an issue. I live in a micro climate which sees average (driving) temperatures of 10-12C (50F) in winter to 20C (68F) to 28C (82F) in summer. Sure it can get colder or hotter but I don't go driving in 5C (40F) temps, not enjoyable. Besides, when I am out in these colder starts or when I want to kick her over in winter, starting these classics is an art and fun! It takes a little feeling, a little gas, grab the throttle, bring the rpms up to 1,500-1,800rpm for a minute (to get oil flowing) and then once up to temp, off you go. Easy!

Carbs have also come along way with technology and tuning. My AVS2 series Edelbrock carbs have the more modern "annular boosters" which are awesome! In laymans terms, instead of one large jet of fuel, its smaller holes releasing fuel like a "misty spray" vs a "hose". This allows for better fuel atomization which equates to better bang, power, fuel economy and response. The annular Edelbrock carbs are as close as you can get to EFI response, I'd say 90% EFI drivability and I've had both. The 10% difference is an excellent trade off for the EFI issues I had and the simplicity and ease of tuning with the no frills carbs!

Once the 540ci was built, it was time for Marsh Motorsports to tune up the Edelbrock carbs (they are die hard Holley / Quickfuel guys lol) but said they'd tune the Edelbrocks for me. I supplied Marsh with Edelbrock calibration kits, pump nozzle kits, 1:1 throttle linkage and my TTI headers for tuning. The calibration kits aren't "necessary" but if you are dyno tuning an engine professionally, it's better to supply them with all the tools they need to dial it in properly. Marsh fired up the engine for the first time, checked the filter, made sure the build and quality was up to their standards, broke it in, did the first oil changes and gave the engine a big green tick of approval. She's good to go!

In terms of tuning, I wanted to run 95 fuel like last time, I can make plenty of power on it, while not 98, it's the convenience and safety factor that 95 fuel is everywhere. When you have a 8.8L Hemi with a drinking problem, you don't want to be in the middle of Buttfuck nowhere with no place to tank up. Also, with the likes of Only BP and Mobil being the only ones sell 98? No thanks! I'd rather drop 15-20hp and call it a day.

Gull also discontinued 98 and went to 95 a year back with zero plans to bring it back. Unlike the original build which had a 10:1 compression, talking to Marsh they said with our shitty fuel in NZ, 10:1 comp would be too much for 95 fuel. He made adjustments in the pistons to lower compression to mid-high 9s to help and tuned it accordingly. It all helps run better.

Doing this also lost a bit of power, from around 660hp/691ft-lb to possibly 30 less on each figure. I didn't want this so Marsh said there's many ways to gain that back, one being port and flow work on the heads. I said I'd love to stick to the 660hp I had but if he hit 700hp+, I wouldn't be disappointed either! I didn't want much more than that, like 800hp+. On the street, it's just useless (for my goals). At the old 660hp, she hooked and BIT perfectly. Throw you back in the seat stuff. And as the old saying goes, "Spinning ain't winning! "

Once built, the 540ci Hemi was taken to Henrys to reinstall it, then Hamish my auto sparky removed the EFI injector cables, left the ECU to run the Dakota Digital dash and gauges and installs the new Autometer 0-15psi gauge, US Shift throttle position sensor and make sure everything was good to go. It was a relatively easy process to swap from EFI to carb on an engine that never had it. Main cost was the carbs, then EFI to carb regulator. The intake had to have the fuel rail holes plugged and painted over as well. This not only tidied up the engine and lost a little weight, we had to do it to be able to run the new fuel lines and carb throttle linkage.

The photo gallery below will show the process of tearing it down, the rebuild, parts used, etc. I thought I would share this experience, as it may actually help someone going through a similar issue (bore wash), or wanting to go EFI to carb. Despite what happened, it's still a fun project LOL. Even this shit excites me. Researching new pistons, regulators, carbs, AN fittings, etc all hours of the night to once again, resurrect and bring this big beast back to life: bigger and badder than ever!

Parts Used in EFI to Carb Conversion and Hemi Rebuild

Edelbrock AVS2 "Thunder Series" 650cfm Carb w/Electric Choke - Part # 1906
Edelbrock AVS2 "Thunder Series" 650cfm Carb w/Manual Choke - Part # 1905
Edelbrock AVS2 Series Calibration Kits (x 2) - Part # 1948
Edelbrock Accelerator Pump Nozzle Kits (x 2) - Part # 1475
Aeromotive EFI to Carb Dual Stage Fuel Pressure Regulator - Part # 13220
Aeromotive High Fuel Pressure Gauge (0-100psi) Part # 15633
Aeromotive Low Fuel Pressure Gauge (0-15psi) Part # 15632
Aeromotive Black 3/8" NPT to -8AN Fittings for Regulator Ports - Part # 15616
Aeromotive New 10 Micron Inline Fuel Filter - Part # 12650
Autometer Sport-Comp II Pro Control 0-15psi Fuel Pressure Gauge - Part # 3667
Fragola -8AN to 5/8-20" Fittings for Carb to AN Adapters - Part # 491967-BL
Fragola Black PTFE 6000 Hose and PTFE Fittings for "Fuel Log" Carb Feed
US Shift Throttle Position Sensor Kit for Edelbrock Carbs
VHT Hemi Orange 550F Engine Enamel Paint for Hemi = Part # SP120
VHT Gloss Clear 550F Engine Enamel Paint for Hemi = Part # SP145'
Performance Car Graphics Custom "540 HEMI" Air Cleaner Decals

( Build in Progress... )

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As soon as I heard the knock, driving ceased immediately. The Dodge went straight up on my hoist to try and locate the "knock" myself...
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Time to start checking some basics by process of elimination. First we tried the flex plate and new ARP hardware as it did sound close to that area and flex plates can be off or "wobble". Installed and no change.
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Next after some advice from the original engine builder, he suggested we try to install a Spacer Kit as it is possible for the rockers to hit the valve covers. Not sure why after only 2,000miles and a new build they would start to hit, when surely those spacings should have been dialled in prior but I followed his advice. Longer spark plug tubes were also needed other wise the originals would stretch and get damaged. They arrived after several weeks and installed but sadly, no change. Knock still present.
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After a few more diagnostic attempts, pulley system wobble, transmission, converter, rockers, checking for collapsed lifters, etc with no success, there was really only one thing to do... time to tear down the engine.
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In order to do a proper tear down inspection, and eventual re-build, there is no other way to do it than the engine being removed. Within a few days of making the call, the 540ci Hemi was hoisted out from the Challenger's engine bay.
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Lucy waiting with all the other cars who also need work. I decided to bring her home while work was being done and help free up space at Henry's since the engine inspection and build would take several months. With parts delays, waiting for custom spec pistons, push rods, shops working on other vehicles, etc. If you've been through these builds, then you know exactly what I'm talking about! lol. Two lessons. It never gets done on time and it definitely never gets done under budget!!
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Back at home while the engine work is being completed. She looks amazing, good to see the engine bay, k-frame, etc all looking solid and fresh (as they should). Making the most of this bad experience! lol
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Closer up...
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The original #'s matching 375hp "440 Magnum" looking on wondering why all the fuss. lol Still stoked to have the Hemi and will get her dialled in properly (and locally!). Will eventually build the 440 up as a display engine, half way there. Just need manifolds, 4bbl carb, paint air cleaner, timing chain cover, etc. Very cool display piece!
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With the Hemi out, the transmission obviously had to be removed at the same time. I used this opportunity to really pep up the TF727 and change something that had always bugged me, the forward pattern manual valve body setup. Currently, while in traffic, going from [3] to [N] to let her idle or a quick rev while rolling, or even hopping in every time going from [P] to [1] (furtherest apart on a FMVB) was a rigmarole in a ratchet shifter. I had always wanted to rectify this at some stage by installing a REVERSE manual valve body (RMVB). [1] to [N] was one shift, [R] to [1] was 2. Clean easy and when the Hemi was at WOT, you're pushed back into the seat so grabbing the pistol grip to shift up a gear was easier to pull back with the flow, vs. against it, pushing the shifter forward. While getting this done, Chuck Mann installed a whole bunch of 727 racing goodies I ordered. You can see the full build on this website on the "Torqueflite Race Build" page.
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Some people might say it's a little bit overkill to build the trans as well since it was performing nicely and everything was perfect. Good to inspect it (no harm) while the Hemi was getting the same treatment and BEEF it up too.
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The 540ci Hemi block after being completely torn down. Sad sight!
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From the front...
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The bottom end...
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Keith Black 426 Based Block.
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The 4.505" bore showing some light contact scuffing.
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All cylinders scuffed...
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The CP pistons themselves (great pistons by the way and not their fault at all). You can clearly see the contact point and darker grey damage resulting from scuffing the wall.
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Worse! The entire side profile making contact...
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All pistons had this damage, not 1 cylinder "having a bit of bad luck", all 8!!
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Another finding was damaged 3/8" HD Manton push rods from inadequate tunnel clearance. The damage is clear to see, enough contact to literally make a groove.
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All 8 pushrods have to be replaced...
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The contact point on the "tunnel" or pass through hole where the push rods were making contact.
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The 540 Hemi standing out in the machine shop waiting room with Fords, Chevs, Holdens, Japanese, all kinds of builds and work going on. Very cool! Good or bad, you simply have to enjoy the experience. :)
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After being at a local Tauranga Engine / Automotive Reconditioning shop for nearly 4 MONTHS, my patience had worn thin. All that happened in that time was disassembly. Not good enough. Actually embarrasing. That and the fact they seemed out of their league with Hemis. I collected the Hemi and took it to Marsh Motorsports Ltd in Auckland whom came recommended by a good Mopar man I know who has, races and owns big cubes Hemis. I trust his wisdom. Very pleased to get it out of the Tauranga shop!
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A better overview of all the parts in my van: block, crank, heads, intake, EFI, damaged pistons, sump, valve covers, the internals, bolt ons, etc, all accounted for. Right... now to take it to a proper Mopar shop!!
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While I'm waiting for the engine build, I got side tracked and will be buying a new Tank Inc EFI tank, 340LPH pump and floatless fuel sender. This is just a new fuel filter as I want everything fresh... having had cylinder / fuel wash, I don't want any risks with anything fuel related, old, stale, too much fuel... fuck me haha. Doing everything I can to be safe.
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Some new goodies while I wait for the engine build. What car guy doesn't enjoy these packages!
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New Autometer Fuel PSI Gauge, Part # 3667. This will replace my old EFI Fuel PSI gauge in the lower left hand dash area under the cluster. The EFI pressure is different to carbs (way higher). The old gauge was 0-100psi and was generally set at 42-45psi. This new gauge is 0-15psi which is easier to view and keep an eye on for carb psi ranges. More precise for smaller increments. My dual 650cfm carbs will be set to 5.5 / 6psi MAX. So trying to keep an eye on 5.5psi on a 0-100psi gauge is impossible lol. I'll get a photo as the build goes on and it's in place. Can't beat Autometer!
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One of the best new parts I have ordered and absolutely crucial to the new carb set up. The Aeromotive dual stage EfI to Carb Regulator. This unit allows me to maintain my Aeromotive electric in tank fuel pump (340lph) and fuel lines (inlet / feed and return). It first takes the pump pressure (usually set for EFI) and controls pump/line pressure, dropping it to whatever we set, generally 14-16 PSI. The secondary regulator then takes it further and controls the carburetor pressure, anywhere from 5-9 PSI. Mine will be set to 5.5 / 6 PSI. Very nice piece!
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The dual regulator has: inlet feed fuel line, return fuel line and 2 ports for feeding the carbs. I'll be blocking one with a 3/8" NPT pipe plug and using -8AN PTFE to feed my two carbs via a custom "fuel log" style set up. -6AN would suffice but since I'm running a single feed line vs. 2, better to have a little more flow and size. Consensus is, either dual or single line feed will work fine, just a matter of appearance and making sure your engine doesn't run lean or run out of puff.
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The regulator also has 2 x 1/8" NPT ports for running pressure gauges. One of the gauges is for the (high pressure) tank side (0-100psi).
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The other 1/8" NPT port is for the carb side (0-15psi). Both PSI gauges are a must have to maintain and keep your fuel pressure set correctly. As you saw before, I also have a fuel PSI gauge in the car to also keep an eye on things. Once set, they should be good for life but, I'm not taking any chances.
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Here's a diagram of how it is set up. Simple. Clean and "if" I ever wanted to go back to EFI (extremely unlikely), it's just a matter of putting the EFI regulator back in. All my EFI stuff; regulator, throttle bodies, rails, etc have been stored safely in a storage container in my garage. I doubt I'll ever go EFI again, not after my fuel / bore wash issues but, they aren't taking up any space safely tucked away.
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Waiting for an engine build is long. There is literally nothing you can do but prepare for its arrival and have everything planned out and the parts ready to go. Here I'm just looking for a nice place to put the new (larger) dual regulator. Tucked just behind the large "Hemi" orange oval air cleaner seems to be the ticket. The current fuel and return line from the tank reach perfectly, one -8AN line out from the right side to feed carbs, 2 x gauges (1 on front with 90 degree elbow facing towards camera and the other facing straight out close to the firewall. Perfect!
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The "US Shift" Throttle Position Sensor Kit. This bolts to the carb and runs in conjunction with the throttle and ECU. I am still running the ECU to control gauges, shift gear display, etc... basically everything but the injectors and anything fuel related.
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Closer up of the TPS... it's a nice unit. Quick shipping, instructions and gear from US Shift.
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The 540ci came from FHO painted in a deep orange, I was never a real fan of it. Looked more Chev orange than Hemi. I wanted VHT engine enamel Hemi Orange. It's a can spray but don't let that fool you. It's all in the prep and is from my research, the highest rated temp engine paint. Plus... it's a lighter nicer orange. So, I had to take the air cleaner lid to bare metal (only piece of the engine I have) to remove the darker orange and coat it: prime, orange and then clear.
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New custom "540ci HEMI" air cleaner decals from Performance Car Graphics. Great product, fairly prompt delivery but no notification, emails or updates. It just randomly shows up lol. But hey! They made it.
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Closer up. With the air cleaner and engine being repainted a different shade of orange, a new decal was required. I got a few spares... they came a long way and I'm not risking fucking up one or it being crooked and having to wait another 4 weeks! They look mint though!
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Here's a good comparison. The #'s matching (in progress) 440 display engine is VHT Hemi Orange and what I am going with for the 540 Hemi. The air cleaner orange I believe is POR 15 Engine enamel Hemi Orange. It's a more vivid or reddish orange. Different strokes for different folks but I much prefer the lighter VHT Hemi Orange!!
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Another photo trying to capture it in real world light from a different angle.