Rebuilding the Hemi

Well... I can honestly say with my hand on my heart that I never thought I would have to make a page like this, especially this early, 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. It wasn't a loud "bashing" knock, but enough to signal the engine wasn't happy. Most may not have even picked up on it. I will share a video of it in case others are having a similar issue.

I took it into 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, still the noise was present. Sadly, with these exterior 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. 

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 them up and instantly felt at ease. Loud, happy and a bit full on but I felt confident. They had worked on many Hemis, 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!

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, 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.

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. This was more than likely the "knocking sound". These were all thankfully picked up by Marsh Motorsports who rectified the issues using high quality parts. 

Cylinder wash can be caused by faulty injectors, poor tune or poor break in procedure. I was truely unaware of how bad it can be with a new engine. This left a very sour taste in my mouth from the EFI experience. It was always a littler rough, had some throttle issues and then the fuel wash but faulty injectors and ECU issues. 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 them for a reason - simplicity. Less parts to go wrong. sure, EFI can run smooth 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. There are 2 main "cons" for carbs when speaking to most, 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. Embarrassing at a busy petrol station forecourt mid-summer.

Fuel vapour can be fixed by carb spacers to distance the carb which helps a little but isn't often a proper fix but the best fix and in my case, is an electric in tank fuel pump. I already had one and being in a cool gas tank far from heat, it has zero heat issues and because of the constant pump pressure, the fuel is quick to get to the carb without any heat issues.

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! Besides, my previous EFI system was never perfect. Cold starts also took a little practice.

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 8 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 in some cases and response. The annular Edelbrock carbs are as close as you can get to EFI response, I'd say 90% EFI response 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!

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. They ran in the engine, checked the filter, made sure the build and quality was up to their standards 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. 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 tunned it accordingly.

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. 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.

Summary: Thankfully, I'm not a downer, and I'm lucky enough to be in a position to be able to afford a rebuild. These things can happen, to any engine, any brand, it can come down to a bad tune, single part (often a low value one FFS) and sometimes even luck (good or bad). 

The photo gallery below will show the process of tearing it down, the rebuild, parts used, etc. I thought I would share this experience, I could keep it quiet, and hide it trying to save face, but why? I'm not ashamed or upset and it may actually help someone going through a similar issue. That and funnily enough, it's still a fun project LOL. Even this shit excites me. Researching pistons, rings, why and how all hours of the night to once again, resurrect and bring this big beast back to life, bigger and badder than ever.

Build in Progress (Check in for updates...)