I am still mulling over the possibility of building a long rod motor out of the 198 i recently acquired. The 198 was a remanufactured unit that spun the #3 con rod bearing and scored the crank. I have a choice of regrinding the crank and getting new con rod bearings, or getting a 225 crank and new bearings. Either option will cost about the same, or close enough to make money not a factor in deciding which route to take.

My question has to do with piston options if I chose to build a long rod motor. Putting a 225 crank into a 198 while keeping the 198 rods will put the pistons 0.2425 inches farther up the bore. I need to verify how far down in the bore the pistons stop at TDC with the 198 crank, but I believe that adding 0.2425 inches of stroke will result in the pistons coming out of the block at TDC. This means that I need to get a piston that has the piston pin hole closer to the top of the piston than the stock slant six pistons.

I have never built a non-stock motor before, so I don't know where to begin to look for piston choices. Can someone point me in the direction of a catalog or searchable database that will list piston diameters and wrist pin locations? Adding to the complexity is the fact that the block has been bored .060 already.

I am trying to pencil out costs to decide if I should just repair the 198 crank and keep the motor a 198 or if I should make the leap and build a long rod motor. My goal would be to build a strong motor for street use in a heavy vehicle, probably naturally aspirated but possibly getting forced induction in the future. Any advice, recommendations, input, and/or guidance is greatly appreciated.

DOC's stroker article mentions a few options on piston choice. If you have the rods already it is no more expensive to build as far as I've experienced. I don't recall which engine mine were originally from,but it's either the 2.2 or 2.4 Chrysler turbo engine,they are cheap if you just use a cast piston and are available individually. One has a small dish (the early 2.2) and the later has a larger dish. You will need to do the math but I'm pretty sure the larger dish and a head skim will get you in a good place. I bought the small dish and machined them to exactly the comp I wanted,but if you don't have facilities to do this it is obviously an added cost. A standard sized piston will put you ata .045" oversize slant bore...ie the Std 2.2 piston is 3.445". You will need 2 ring sets since you can't buy individual rings like you can the pistons. I found it cheap and a worthwhile modification and gets rid of the old beer can style heavy pistons and you get a much nicer ring set as well.

OK- I am aware of the 2.2 or 2.4 piston choices, but do those go .060 oversize? I would need a metric piston that went about 1.5 mm oversize. I believe 2.2 pistons are available 1.5 mm oversize, but I would also need to bore the block out a bit too, which adds to the cost. Hmmmm.

It is true: "speed's just a question of money. How fast you wanna go?"

That'll be 2.2—2.5. The 2.0/2.4 are a different engine family altogether, though the 2.4 is said to have a 3.44" bore (like the 2.2/2.5) and Wikipedia (for all it's worth, which can be less than zero) says the 2.4 turbo engine features 'Mahle cast eutectic aluminum alloy pistons". No idea whether the 2.4 Turbo pistons are easily compatible with a Slant-6 rod, etc. RockAuto shows pistons and rings available in 0.020" and 0.040" oversize, the latter of which would give you 3.48" bore --> --> 235 cubic inches (3.86 litres) with a 225 crank. Offhand I doubt you'd find non-custom 0.060"-over pistons for this application, but if you did, that would wind you up at 238 cubic inches. Probably not cost-effective to spend custom-piston money to get 3 extra cubic inches.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yeah. If I were starting with a non-overbored block and had the money to do a complete custom motor build, I would go with the 2.2/2.5 pistons (sorry about the 2.4 typo!). However, the 198 block has already been bored .060 over, so to build a long rod motor I need to find a piston that will work with both the 198 rods AND a bore of 3.46 or larger.

I think cost wise it will be cheaper to just keep the 198 a 198 and get the 198 crank repaired. A long rod motor would be nice and fun, but I don't have the money for the pistons, rings, and overboring it would take to build it.

You can use 2.8L Chevy pistons in standard bore that is 3.502" and is the same size as the Wiesco. In my car that put the piston about .020 down in the bore with 198 rods. Gives you a cheap alternative in a cast piston. I think the wrist pin is a couple thousands larger than the slant 6 but the rod can be easily reamed when you have the pistons put on the rods.

Rick

PS. All this is from memory, but is pretty close. If you need something exact just let me know. Lou has the same set up in one of his engines.

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Thanks!

I also just confirmed that the 198 with the 198 crank puts the pistons .177 down the hole at TDC, so just dropping the 225 crank in is not an option. That would put the pistons .0655 over the deck. Increased compression is good, but I think that would be too much.

The piston I used was a Federal Mogul Part # 516P for a 173 ci Chevy.

Rick

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

If you are trying to do it on the cheap just get another 198 crank and call it done...not what I'd do,but it gets the job done. I just looked at the build sheets for the 225,I used Clevite pistons,early 2.2 Turbo models with a 11.5 cc dish machined into them. We don't have these engine sizes over here,but even with shipping they were still cheaper than a stock set for a 225. I know the 225 has that much excess metal in the block deck area it isn't funny,but the idea of using a longer rod,lighter piston,better rings and just a skim off the deck and head with the option to dish the piston was just too good a thing for me to pass up....but hey,plenty of ways to skin a cat...just as long as the cat gets skinned!!
By the way,no, I don't literally skin cats for any of you who may take this the wrong way!
As to what over sizes are available in the 2.2 piston,well,you can look that up as easy as I can. If you need to go out to 3.5 then there's other options for you,I've never used the larger pistons but I know people over here that run a Holden piston with 225 rods to get a large bore.You WILL need to at least hone to size for whatever piston you choose,you cannot have any ridge at the top of ring travel when changing the rod/piston package.personally,I'd measure the bores first to see what it will clean up at,removes a lot of options that may not be available to you.

Thanks! Someday I would LOVE to make a trip to Australia and New Zealand.

The 198 was given to me by a board member after he removed it from a Valiant a friend of his owned. The friend purchased the 198 as a remanufactured 225 engine from Jasper Engines (a nation-wide engine remanufactured here in the States). The 198 was run for an unknown number of miles in a street car until it developed a nasty rod knock and oil leaks. So it was pulled, stored, and eventually given to me. I have diagnosed the rod knock to a failed #3 con rod bearing, but I have not diagnosed what made the con rod bearing become oil starved, seize, and grind itself to oblivion on the crank journal.

Maybe I can convince my brother to give me the crank and block from the good running 225 in his 74 Duster! Probably not, unless I build him a fresh hydraulic lifter 225 for his Duster. Time will tell.

If I did the motor now, it would definitely be trying to do it on the cheap. However, if I bide my time, I might actually get the 225 motor from my brother's Duster to play with. I might just mothball this 198 until I have the money to build up a long rod motor right.

A couple of points:

- A long rod engine does not add stroke, the stroke remains at 4.12 (225) but the rod ratio, piston weight & ring drag relationships improve.

- A factory 198 has a - .070 (really around - .080) negative deck height. (a 225 is called-out at - .145)

- A ".020" oversize 2.2 piston measures 3.465.
A while back we took a .060 225 block, bolted a torque plate to it and re-honed it to .065 (.005 more or .0025 per side)
The block's bores all cleaned-up quickly and evenly... then we built a long rod 225 out of it.

- See if that spin #3 198 rod is any good. You may only have 5 useable 198 rods to work with.
DD

If that's the case, then you could make a cool long-rod 194 Slant-5 engine (225 crank, 3.46" bore), with a baffling firing order of 1-5-6-2-4.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Right. I was talking about adding the 225 crank (4.125" stroke) to the 198 (3.640" stroke) engine while keeping the current 198 rods and pistons. This would increase the stroke of the 198 motor (effectively making it a 225). However, with the current 198 crank (with the shorter crank throw), I measured that the pistons sit .177 down the bore when at TDC. Putting the 225 crank into this motor with the current rods and pistons would increase the crank stroke by 0.2425 inches and result in the pistons popping out of the top of the block at TDC by 0.0655 inches (-0.177 + 0.2425= 0.0655).
I wish I had that. Jasper must have done something bad when they remanufactured this engine because the pistons now sit .177 down the hole at TDC. Well, obviously they did something bad because the #3 bearing became starved for oil and seized. I guess I really need to tear this thing down and see what is going on.
Hey, that sounds like a plan! I might give that a shot.
Will do. In case the #3 rod is junk, I have already sourced a single NOS 198 piston from a dealership that was closing and selling of its old inventory. So I have at least 6, but possibly 7, good 198 rods.

If I can tear this motor down and figure out the cause of the oiling problem, and if I can get enough dough to get a 225 crank, .020 oversize 2.2 pistons and rings, and pay for the machining, I may build a long rod motor yet! Thanks for the info Doc! I am new to custom engine building and really appreciate the help I get on this board.

If you are already that far down the bore, sre you sure it is not a 225?

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

The engine code stamped on the id pad by the alternator lists it as a 198 and the connecting rods are 7 inches center to center.

Engine code stamped by alternator: GW198 R 3449 0200

Also, my rough measurement from the top of the piston to the middle of the combustion burn ring on the cylinder wall was roughly 3.5 inches. Definitely not 3.1 (170) or 4.1 (225) inches.

However, I am not above admitting I make mistakes. Once I pull a connecting rod out I will do a careful measurement of the distance between the piston pin centerline and the crank centerline and see if it isn't 7 inches, but I did already lay a measuring tape on an installed rod and the number I got was longer than 6.7 inches, the 225 con rod length.