This is part 2 of many in Limitless’ engine build. – be sure to check out the rest of the posts there. Pictures – my AFR heads! They were technically the last part I bought for the first engine, but since that engine went bye-bye, these ended up being the very first part selection of the overall build! In a way, they (and the cam, which I’d already selected but hadn’t purchased), guided the rest of things…but it all worked out in the end!
There are a *ton* of parts in an engine. One piston, mounted on it’s rod and ready to go, has 16 different parts…two bolts, two bearing halves, a cap, a rod, a pin, two spirolocks, 4 oil rings, a top ring, a bottom ring, and the piston itself. Multiply that by 8 pistons per engine and we’re at 128 parts already…and don’t even get me started on the valve train. All things considered, there’s probably over 500 parts in an engine…and as I mentioned previously, they are all important.
In the interest of time, I will not go through each and every individual part here – though I’ll try and do a good job of going through all the parts in more detail through the later, assembly focused blog posts. But in keeping with the current theme of planning the overall engine, I thought it would be worth outlining the overall component choices, and why I chose them…so consider this a high level overview before we start diving into the nitty gritty. I’ll cover things in roughly the order you put them together, since that seems to make the most sense.
Block
Starting off simple. Somewhat obviously, I went with a Chevy Big Block. In this specific case, I chose a Mark IV 454 block, since they’re pretty much the most common, easiest to get parts and modify for, etc. Mine happens to be bored 0.040″ over, since it was already 30 over and needed some cleanup. It’s also a 4 bolt main since I wanted the longevity, and it’s a “seasoned” block – meaning it’s already been used. In a weird twist, blocks are one of the few areas that you actually want something used. It’s pretty hard to break them beyond repair, and if they’ve been well used then they’ve “settled” molecularity, meaning that any machining you to do them won’t shift further under hard use. This is the one part of the engine that I didn’t get new, because a new block costs *way* more, and isn’t actually really any better for my needs.
Rotating Assembly
You can’t have an engine without pistons, rods, and crank! Together they make up the full rotating assembly, one of the most critical parts of an engine. In my case I wanted forged everything – again for the longevity – and the fact that my block was 40 over made pistons a bit harder to find, since 30 and 60 are the common sizes. I ended up with a Scat crank and rods – both forged steel – and forged aluminium ICON pistons. They’re all internally balanced, since that’s kind of the only way to go, and have a two piece rear main seal since I need that for the mark IV block. I went with the “flat top” pistons for two reasons. The first is that they promote pretty much the best quench / flame propagation, and the second is that they were the best fit for my desired (pretty low) compression ratio, given my heads.
Cam
The “brain” of an engine…a cam is what programs the engine to behave the way it does. Arguably the most complicated aspect, or the most multi dimensional, a cam affects pretty much every aspect of how the engine operates, and is sort of the thing that ties everything else together. In my case, I had a few unique requirements – I needed to handle wet exhaust without reversion, and needed a relatively high peak horsepower figure at a relatively low RPM. I ended up going with a custom grind from COMP cams, courtesy of Hardin Marine…it’s relatively low duration and high lift combo, with an aggressive profile. The duration helps with the reversion (wet exhaust) and low RPM power, and the lift and aggressive profile help with making as much power as possible.
Heads
Heads have one very simple job – get as much air into the engine as they possibly can. Unfortunately far too many people still think that the bigger the head, the more flow, the more power…but this isn’t true. As the runners get bigger, the velocity drops assuming the vacuum on them is the same…and lower velocity is actually bad. So really, the trick is to maximize velocity, without choking flow potential. If a 200cc runner flows as much as a 400cc runner, that air is moving roughly twice as fast – which is a really, really good thing. I ended up picking a set of AFR 265 Ovals for a few reasons. They’re aluminium (and anodized for marine use), so they’re lightweight. They flow *incredibly* well, with teeny tiny runners, so they’ll make stump pulling torque and gobs of power at the lower RPM – key for my application. And they’re incredibly well built, with top of the line valves, springs, etc. They’re the second most expensive line item in the build after the rotating assembly – but, short of switching to a whole different engine – are definitely responsible for the most amount of power.
Valve Train
The oft overlooked valve train is in charge of putting the cam’s requests into action. A lot happens between the lobes of a cam and the valves themselves, and it’s the valve train’s job to make it all happen. I went pretty much exclusively COMP here, partially because they’re a big name for a good reason, partially because they had everything I wanted, and partially because when one company does the cam, lifters, pushrods, rockers, etc…everything just sort of works, and you only need to bug one tech support line. And their tech support is AWESOME. I have a full roller setup in my engine, again for longevity…hydraulic roller lifters, Hi Tech pushrods, and Magnum roller rockers. The valves are stainless and inconel to survive the marine environment, and the springs are PAC racing springs since they came with the AFR heads (though I did spec them specifically for my application, which AFR did for free – thanks AFR!)
Intake
There’s three basic kinds of intake – the dual plane, single plane, and tunnel ram. Dual planes are great for almost every car other than all out racers, because they actually work at lower RPM that most cars spend their time at. They effectively split the intake into two (hence “dual plane”…), which doubles the signal at low RPM. It also doubles the restriction at high RPM! A single plane is just the opposite, so it favors high RPM work. Then there’s a tunnel ram, which is effectively a single plane on steroids, and frequently has two full carbs / throttle bodies on top. This was actually one of the hardest components to pick, but also weirdly one of the easiest. There is ENDLESS debate on dual plane vs. single plane vs. tunnel ram for various applications online. But for my application, a single plane was the clear choice…and so I went with an Edelbrock Victor Jr., one of the best single plane intakes there is.
Fuel
Right from the start, I knew I wanted EFI. I have not-at-all fond memories of our only carbureted boat…it ran good, if it would run at all. Rain? Nope. Cold weather? Maybe. Hot day? If you’re lucky. Now, from my sledding experience, I know carbs can run really, really well. But this is a pleasure boat – even if it’s an obscenely over powered one – and I want it to start in a second or two, without muss or fuss, all the time, no matter what. I also want it to run equally well on a 35 degree day in July, as it does on a 10 degree day in October. And most importantly…every ounce of fuel economy I can possibly squeeze out of this build will pay for any extra cost, guaranteed.
Plus, for the INFINITE fear mongering over EFI in a boat, or even EFI in general, it’s actually not bad. It barely costs any more than a carb ( ~$300 over the cost of a 15k engine), and as I mentioned it will pay for itself over time. More importantly, engine guys are engine guys – not computer guys. Tuning carb jets for hours on end? Easy. Downloading newfangled software on a computer doohickey machine? Terrifying. Thankfully, I am a certified computer nerd, and while I know my way around carb jets, I also know how to use that newfangled software – and know how much more powerful it can be. So I went with EFI – in this case, a Holley Sniper system. It’s “plug and play” as much as it possibly can be…it meets all my needs, it’s coast guard certified (which is HUGE), and it’s affordable and accessible without sacrificing performance. Talk about ticking all the boxes!
The kicker came when I realized how much work it is to get an aftermarket EFI system – even a certified one – installed in a certified way. I won’t say much for now because, to be honest, I’m still trying to figure it out…but at some point I’ll go into detail on the rest of the fueling system, with the multiple pumps, tanks, lines, and coolers needed to make it all work. Maybe a carb would have been better after all…sigh.
Ignition
At this point, the engine is pretty much done…but something needs to make the air / fuel mixture go boom. That’s where the ignition system comes in! The name of the game here is KISS – keep it simple, silly. Yes, there’s all sorts of fancy high end multi spark digital capacitive discharge systems. Yes, the Sniper EFI can actually run the ignition itself if I get a certain hookup. But again – this is all about what I need for my setup. And my engine will never turn over 5k rpm, so I don’t need the fancy multi spark digital capacitive ignition. It’s also a jet boat, which is a “one curve” engine…it doesn’t need fancy EFI control. What it does need is rock solid reliability, coast guard certification, and a reasonable price tag. Oh, and a rev limiter, if I ever get any air and the engine tries to see how high it can rev. And so for that, the Pertronix Flame Thrower Ignitor III with matching coil is the winner…with some standard plug wires from JEGS since they were on special.
Oiling
Oil is the life blood of an engine…without it, the engine dies, real fast. So while it has almost nothing to do with the performance of the engine, it’s possibly the most important important section! Thankfully, it’s also pretty easy. I wanted a wet sump system for simplicity, and because it will more than do the job. I went with a Melling 10778 pump after extensive googling on the Socal Jetboats and Offshore Only forums, and a Moroso pan with a decent amount of oil control (and matching pickup). Critically, I also went with a full remote mounted thermostatic oil cooling system. This means that a) my oil will always get to temp, allowing it to boil off any water, and b) it will never get over temp, ensuring my engine is always protected!
Cooling
Last but not least, the humble cooling system. You’d be forgiven for thinking this isn’t even worth mentioning, but unfortunately in the boat world – and specifically the jet boat world – this is a whole different can of worms. There are a myriad of options here and considerations to take into account, but generally the goal is very simple – get the engine to operating temperature, and keep it there. Given you have a near infinite supply of lake water to accomplish this, you’d think the best method would be well established at this point…but alas. Some people want straight water cooling, some people want water restricted cooling, some people want thermostatic cooling, some people want straight exhaust, some people want water injected exhaust, others want water jacketed exhaust…etc etc. Anyways, despite the myriad of opinions, I went with a “full flow” bypass thermostat on the engine, and full water jacketed marine exhaust. More on that much, much later – but this post is long enough as is!
– Dennon
