Trying to accomplish a fun little street burner for the wife. She wants a mudstain buster. Rough idle, fun acceleration, stop light to stop light. Compression, looking at around 9.5-10:1. 1.70in and 1.44 exhaust or close to it. Head work, Offy 4bl intake. 3x2 Hooker Headers. Automatic with nice stall, 2800-3200. 3.55-3.73 8 3/4 or a 4.10 7 1/4. Tire size roughly 26" 275/50r15 or a 28" 275/60r15 E.T. Street.

I'm a fan of the 7 1/4, but don't recommend it any longer. Need a SG for strength, and the parts just aren't available, any longer. What year is the car? If 66 or older "A" body, the hooker headers will not fit.

PS: You should really start your own thread.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Thank you all for your input - much appreciated!

Think it's time to grab some 198 rods - anyone have some to sell? PM me if you do - I'd much rather grab some from here than go the reconditioned route (but glad that's an option).
-Chris

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'68 Barracuda - taking advice on increasing street torque, power, & road handling. Click To See It

A bit of a digression from the 225 to the 198 slant six - a BMW S54 is also a 198 cubic inch motor with a similar 3.43-inch bore (3.58 inch stroke). But the S54 has relatively short 139 MM connecting rods ( 5.472 inch ). The peak hp of the BMW is 343 HP at 7,900 rpm, 273 lb·ft at 4,900 rpm. They make power at high RPM and require manual valve adjustment.

I wonder if the mostly neglected 170 might be impressive with a supercharger. The numbers for the relatively sophisticated S54 come at a high RPM, which no 225 could hope to reach, but a 170 might reach a pretty impressive level, at high RPM a turbo is probably more practical than a supercharger. If a 225 is modified to produce 280 hp and a daily driver, that kind of "Lou" motor is pretty impressive indeed, compared to the costs of this German "198" slant six http://mywikimotors.com/bmw-s54/

The 7 inch rod discussion is always interesting. I have a set of 198 rods from years ago, but would that 9.7 static compression ratio be good in a 1/2 ton truck ?

Sounds like your plans are sound. Make sure to spend plenty of time or $$ on the cylinder head porting, and from a reputable shop or carefully do it yourself. When the K1 rods and Wiseco pistons were $1000-1100 for the whole set, it was really a great bang for the buck. Now the pistons and rings are harder to find and are more expensive. You can make plenty of power with 225 rods and pistons, at least in the low-mid 200 HP range if you assemble the combo well and port a good head. The OCG 346 cam installed at 100 deg would work well with your other parts and 9.5-10:1 on pump premium. Spend time or pay someone to recurve the dist (DusterIdiot?).

Keep the questions coming,

Lou

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Home of Slant6-powered fun machines since 1988

I already have a thread I started on this from a few weeks ago. lol. The car is a 65 and no the Hookers aren't a direct fit, but they can be modified to work. I've done some phone calls and found some ole info on the /6 and Hughes will be the way I'm gonna go on the cam.

Older thread resurrection.
A couple years ago I was faced with needing to rebuild the 22R in my '84 race-chase/desert explorer truck. I had the option of picking up a later long block core or rebuilding the existing. Getting the core meant that I could get the rebuild done with the truck still in operation, but that core was the later, shorter deck (& shorter rods) engine. My engine builder told me that long rods are great for racing & hot street engines, but aren't necessarily what you want in an engine that is going to be worked hard. That increased dwell at TDC also increases the knock sensitivity of the engine. Something I had noted my longer rod engine seemed to be. I had the short deck engine rebuilt and it had far less knock sensitivity than the old engine did using the same peripherals.
Food for thought.........

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Thom

Cross-threaded is tighter than Lock-tite

Gee, I had thought it would produce more even burn and thus be less detonation prone. Not sure of the physics on that one. I could see it either way.

I just ordered pistons for a future 198 crank in 170 block with 5.7" (170) rods and ~1.45" comp ht pistons. 3.625" stroke and 3.504" bore is 3.44L. I think it will spin 7000 no problem. Yes, boost. Might take me another year or two? Nice to hear my rod ratio will be slightly higher than the Beemer mill.

Lou

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Home of Slant6-powered fun machines since 1988

The physics behind building a "long rod" engine usually goes well past most performance enthusiasts ability to digest. Its been hyped up in magazines for decades, but the true benefits have been proven time and time again on the race track and dyno to be negligible in lower power grassroots performance and racing situations. They can be beneficial in short to medium stroke engines that operate in a very high RPM range for extended times like circle track and drag engines that rarely fall below 7000 RPM. It is really only above those RPM's that a longer rod length to stroke ratio will be of any benefit, and the 225 engines rod ratio is just fine for any build that could ever be conceived. Because the longer rod by its nature and physics looses low RPM torque and moves it to the top end of the RPM range, you are defeating the purpose of building an engine that has such good torque down low to begin with by removing a feature from the engine that helps create it. Granted, the 198 rod length does give the slant guy the ability to use a more economical piston alternative, the lose of what you are giving away and loosing in the torque department is far more valuable. Just know that going into it.

Probably the most famous Pro Stock racing team of modern times was/is Reher-Morrison, they wrote many engine building articles dispelling a lot of common errors and urban legends in high performance engine building. They have tested both on the dyno and race track the theory of longer rod lengths and their effect on the power output of an engine. In just one engine in particular, they increased the rod length by over a full inch, in .050" increments. They found that other than the powerband being moved higher in the engine itself, there was no gain or increase in HP or torque of the engine at all. No performance gain at the track either. So they and numerous other respected racers and builders doing their own testing and evaluations also concluded that the connecting rod did nothing more than what its name implies, and that it simply provides the connection between the piston to the crank. And of the top 50 or so things you do when you set out to design and build a performance or racing engine, changing the rod length to stroke ratio isn't one of them.

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There's no such thing as too much cam....only not enough engine!

My long rod junk always seemed to like less timing, but that comes from a combination of things, not just rod length.

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Official Cookie and Mater Tormentor.

That BMW motor is probably the last na M3 motor that BMW will build. It would be good if you can match the performance, even with boost. The BMW guys spend huge amounts of money to get more power from them, there is a $7,000 dry sump system for them. Historically the small BMW six had a 3.1-inch bore, just getting ~ 3.4 inch was difficult.

I picked up a 170 a few weeks ago. I'm looking forward to your project. I don't have the resources to do a whole lot, but I like the little 170 and hope to see them get some respect.