(EDIT: You may want to read the whole thread before replying; this story took a hard, drifting left turn about halfway down the first page.)

It's time to build a new engine for the Race Dart. The relatively stock engine my friend Bob and I built in my garage three years ago has run strong for 9 Lemons races, 5 burnt/blown head gaskets (mainly from too much ignition advance after decking the head, among other factors), and the ingestion of an air cleaner nut that made pistons 1 and 6 look like the surface of the moon. But the crack we've had in the cooling jacket for 5 races is only getting longer, and apparently Barr's Leak washes out after a while. After we get the new engine swapped in we'll do a teardown and see if this short block is salvageable, but that's a topic for the future.

On the engine stand in my garage, I have a spare 5-plug forged crank 225 (casting number 2806830-2) with "F225 T 1112" stamped on the block deck pad. Forum searching leads me to believe this is a 1970 truck engine, but if anyone can decode this completely I'd appreciate it. It did come with a front-sump oil pan.

The plan for this engine is generally as follows:
-Batch-fired multi-port fuel injection. (Bob is doing the research on this because I'm not entirely convinced that electrons even exist, but we will probably end up using MegaSquirt. There will be a future thread in the FI section with specific questions on this front.)
-Dual Dutra Duals. I'm thinking 2" primaries into a single 2.5" pipe with a nice high-flow muffler, but I'm open to feedback on this.
-Normally aspirated at first (until we win Class B at Lemons and get bumped up to Class A, where we will be hopelessly outmatched. Then we add either a turbo or a blower; the jury is still out on that.)
-Generally spending most of its life getting flogged on a road course between 3500-4500 RPM with a top speed in 3rd no higher than 5000 (with a lightly massaged A904 behind it and 3.55 rear gears)

I wasn't really planning a long-rod build initially, but I just picked up the following for a good price (Thanks DI!):
-1 matched set of 198 rods
-6 Silvolite H1291 Pistons (dished hypereutectic 2.2 turbo pistons, .045” over for the slant)
-2 boxes of Hastings 2M4206 Rings (I think these are moly coated)

I haven't disassembled the engine for measurements yet, but I found some generic figures for other long-rod builds on this forum. I think we'll be fine continuing to use the head from the current race motor, which already has a little porting and 1.70/1.44 valves. This head is currently shaved something like 0.085" for an average cc volume of 46 mL. The dishes in these H1291 pistons are a big help; I'm figuring a SCR of something like 9.4 as opposed to the current engine at ~8.8 with stock rods and flat-top pistons. (When/if we do ever add forced induction, I would probably build another head with oversized valves and not cut as much off the bottom.) I'll confirm these numbers once I get my own measurements.

I also bought one of DD's last blueprinted oil pumps (with the high-volume 1" thick rotor and a case-hardened gear). The current race motor is using a Melling pump with a 7/8" thick rotor, so this won't be a huge increase. But it should help since I plan to open up flow with as many of Doug's oiling system mods as possible.

So this brings us to the inevitable question: what camshaft should I use? I'd obviously prefer something that would perform well both NA or with 5-8 psi boost. I assume the best option for ensuring the life of the gear would be to send the stock camshaft to OCG for a re-grind.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

An 830 block is a good place to start.

The cam is the last piece of the puzzle......after head CC and figuring block deck height with rotating assembly.....convertor...gears....

Myself....Id build a fairly stock CC head and deck the block to get the target SCR.
A more open chamber is easier with big valves and high lifts.

The first thing is a crank so you can get some measuring done.

Digital calipers.....

With 198 rods, those pistons and an uncut block your pistons will be about .020" down the hole.

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Official Cookie and Mater Tormentor.

Sounds like a fun buildup. I am also scheming a new LeMons engine for our Valiant. With 9.4:1 NA, I would use the OCG 346 cam with 106 LSA. For a compromise where I would add boost later, I would use something more like the 1947 w/a bit shorter exh like 819. For those, I would run 106 up to maybe 108 LSA and degree at 98-100 centerline.

For boost and 8.5:1, I would do something like 1947I and 2106E and then 112-114 LSA. Hard to optimize both. Cam regrinds are cheap and races are expensive...

Lou

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Home of Slant6-powered fun machines since 1988

That's about what I've read. Luckily these pistons have about a 20cc dish, otherwise I'd definitely be building a new head.

Thanks for the recommendations, Lou. I think rather than compromise, I'll probably just pick a good regrind for NA and then swap it whenever we get around to forced induction. That could still be a few years away, depending on how things shake out.

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

I like that kinda talk. Happy planning and building.

Lou

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Home of Slant6-powered fun machines since 1988

Resurrecting this thread, as I'm finally getting around to putting this engine together a year later. Unfortunately, although I have all the machine work done except getting the crank rebalanced, the entire plan has now changed. Now I'm buying the big damn turbo kit off SSG Pohlman's truck and running that on the Lemons car because I make bad decisions for a living. The general plan is to keep the boost low for our first race, maybe 6-7 psi, and dial it up from there. It's gotta stay alive for 8 hours of hard driving at a time.

I've got this block bored for the metric pistons and 198 rods, which is fine. All I have left is to finish some minor oiling mods on the crank and have it rebalanced. The OCG 346 camshaft I ordered will go on the shelf for a later build. The head is a different story. It's cut for 1.70/1.44 valves and I've done some bowl work and port polishing, but I had it milled 0.080" for NA use. I just confirmed the chambers measure 48cc.

To make matters worse, the dish in these turbo 2.2 pistons isn't as big as I thought; they're more like 15 cc instead of 20. I don't have a final piston deck clearance number yet, but if I assume 0.020" down the hole like I've read elsewhere for long rod builds, this engine will be making around 9.6 SCR when it's all together. That's using an Aussie head gasket I picked up from Lou, with a 3.53" bore and reported compressed thickness of ~0.045".

So there are a few ways I could possibly go here.

1. Ideally, I'd like to reduce the SCR while using the existing big-valve head. I'm just not sure how low I need to go for turbocharging to make any sense. In order to get down to 9:1 SCR, I'd need a head gasket with a compressed thickness on the order of 0.080". I don't know if that exists anywhere. Or I'd need to take another 5 or so ccs out of each piston top, which doesn't look too feasible. However, some combination of both might work.

2. I also have a totally stock, freshly rebuilt head with 58cc chambers. That would give me ~8.6:1 SCR. I'm not sure how much power I'd lose by running stock valves vs. bigger valves with the turbo (or alternatively, how much more boost we'd need to make the same power).

3. Finally, I can bite the bullet and spend another few hundred bucks to have yet another head cut for big valves but with less deck milling this time. This isn't a great loss in the long run; I already have two sets of 1.70/1.44 valves I can use, and the NA head can always go on my Valiant. It's just more money, and more time with the die grinder when I already have way too much work to do in the next 3 months.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

What kind of octane gas can you get for a Lemon's race?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

What is the status on the port EFI? That will help with durability and tunability quite a bit.

I am thinking the stock-valve head might be the way to go. You could pop the valves out and do some bowl porting if you have not already. Boost overcomes flow problems like nobody's business...

Ryan Covalt is looking to make a MLS gasket order and thickness can be changed easily, IIRC. You might talk to him.

Lou

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Home of Slant6-powered fun machines since 1988

x2 for the stock head under boost.
Make sure the valve springs are strong enough and bolt it on.

Having to dial back the boost to control detonation defeats the purpose, and the fuse ends up shorter anyway.

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O==\=/==O

"A mechanic is Somebody."
- Jim Preston

An .080 head gasket is asking for trouble IMO.

Why can't you machine the pistons to get 5cc out? Not enough meat?

Good point, Gregcon. If the pistons are as thick as I think, you could just flycut them 0.030" and gain about 5 cc's. You can measure the piston deck/top thickness and then decide. I bet you could flycut as much as 0.060".

Lou

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Home of Slant6-powered fun machines since 1988

You can typically get 100+ octane gas at most tracks, but it's big money. We usually run 93 octane that we buy at the pumps off site. That being said, endurance racing is harder on everything than you might expect. For the purposes of calibration, let's say I'd want this engine to be safe to run on the street with 87 octane.

Fuel injection isn't going to happen this year. That's one of those projects that is just complicated enough to keep us from starting it when Bob and I both have so many other projects to juggle. We're only doing the turbo for MSR this year because this complete system (with a carb already set up for blow-through) fell into our laps. An upgrade to MPFI is still in the long-term plan, and that would allow us to safely run more boost once this setup is proven out.

If the pistons were flat top, then cutting about 0.035" off the top would get me where I need to be (EDIT: it would get me down to 9:1, which is still maybe higher than ideal). Of course I'd need to assemble one on a rod first to verify my starting point in the block. I need to verify some dimensions, but with the big dish in the middle it looks like I'd need to take off about twice that. The dish itself is ~0.25" deep, but I don't remember how far down the top ring groove is.

Yeah, the more I think about this the more I'm leaning toward just running the stock head. I don't like the idea of taking meat out of these pistons and potentially hurting the engine's long-term durability. I can always build another high-zoot head and swap it on later.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Simplicity and a relatively conservative tuneup usually translate to durability. I agree using the stock valve head is the way to go, at least in the first incarnation. You have a small cam, so the springs should work fine. 6-8 psi boost will make you plenty of power and should be good on pump 93. Carefully monitor and tune for AFR of 11.5:1 or a bit lower under WOT. If you don't have a working AFR gauge, get one. 20 deg total timing. Can you drive it on the street for AFR tuning purposes?

Lou

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Home of Slant6-powered fun machines since 1988

Yep, the turbo setup includes a wideband O2 sensor and AFR gauge. The car's registration is a few years out, but it has good plates. That's been good enough so far for the occasional low-key test drive on my side of town.

So with 6-8 psi at 8.6 SCR, you think a 71+ stock cam is the way to go? I have one of those on hand; I'll just have to pull it from the engine that's currently in the car.

Still need to think about how to handle ignition timing. We're currently running a Mopar EI distributor with what I think is 18 degrees mechanical advance, using a GM HEI module and the vacuum pod capped. Shawn has the turbo system on his truck set up with a locked distributor and electronically controlled advance, with a Hobbs switch to pull a set amount of timing when boost comes on. But I think he's keeping that distributor.

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing