i was looking at some of my engine parts catalogs from last years sema which got me to thinking about making a stroker slant, here is what i came up with. offset grinding the crank to honda size journals.
by offset grinding the crank to 1.90" you can move the center line up to .1435" this gives you +.287" throw. then you can clean up and polish the journals to 1.89" honda size. the extra throw gives you a stroke of 4.41". with a mild over bore of .030 you can have a 245ci slant six, the big bore weisco pistons with a bore of 3.504 gives you 255ci. the honda rod is only .940 wide on the big end stock slant rod is .985. by using a mitsubishi size big end you get 1.038 width and can shave it down to fit. the length of the rod would depend on the compresssion distance of the piston you use, lots of choices out there.

will this work?

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71 valiant 225, 904, 7 1/4
69 W200 power wagon 318, np435, np205, d44 front, d60 rear

I have thought about very similar things, and Mike Jeffrey and others have been using Honda and/or SBC rod big ends for a while.

Rod length might be a killer when trying to use a factory Honda or Mitsu rod, unless you are building a low deck (170 block) motor.

Lou

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Home of Slant6-powered fun machines since 1988

powerwagonpaul:

I was also curious about the proposed connecting rod center-to-center length and what the final deck height you would want to achieve. Any thoughts on these two dimensions?

I'm assuming you would be using the taller 225ci block so I too wonder about the viability of the stroke, rod length, pin (compression) height and resulting deck height. I also wonder about cylinder side loading given the outcome of the resulting "rod ratio". Not sure without doing some math whether things get better or worse.

Russ

Finding long connecting rods with small & wide bearing ends... is the issue.
Yes... you can have custom con. rods made but the cost goes way up when doing that.

Rod ratio is not a big concern... a stock 225 has a 1.624 RR, a long rod engine is 1.697 and what you propose has a 1.587 RR, using a 7 inch rod length.
FYI, I have a 260 SL6 that has a 4.500 stroke and uses the 225 con rod (6.700 c to c) so it has a 1.489 RR and that engine runs fine.
DD

Wouldn't stroking an already long stroke motor just lose rpm potential, I think their would more potential heading in a sqaure direction as in bigger bore to close in on that long stroke.

Kev

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custom rods are the key. what i came up with is a rod that has stock .910 top end and a honda size big end. it would be 6.75" c to c. using a 10.70 deck and weisco pistons at .025 over, .041 head gasket, and 57cc heads this would give you about 8:1 cr. and 244ci.. the piston would be .120 in the hole so you would have plenty of room to cut the block for more compression. rod ratio ends up being 1.530, you might lose a few rpm on the high end, but ill bet its worth it.
k1-weisco makes rods if you order pistons from them you might get a break. with enough interest and a consensus on what to use, might even get a break on a group buy.

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71 valiant 225, 904, 7 1/4
69 W200 power wagon 318, np435, np205, d44 front, d60 rear

Guys:

I'm a long time inline six fan but relatively new to the slant six with lots to learn. I've been able to find sources for most engine dimensions but haven't been able to find a reliable factory spec for the 225ci block height or the pin (compression) height. Is the 10.70" block height indicated above the typical factory value or is that a target height after (block) milling?

Russ

I had the small ends of my 198 rods bushed to fit Metric piston pins.

My stroke is 4.475" and it doesn't get turned faster than 5000 rpm.

It makes big low end and mid. The top end drops off pretty fast above 4500.



CJ

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Part of Tyrde-Browne Racing

Crank centerline to deck spec is 10.68", but most forged crank engines (76-down) are more like 10.73". Stock piston comp ht for all Slant 6s is 1.74".

Lou

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Home of Slant6-powered fun machines since 1988

One thing that you have to remember about a Slant, no matter what stroke you have the crappy small ports and bore make RPM somewhat irrelevant anyway.

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Official Cookie and Mater Tormentor.

Dart270:

Thanks for the block and compression height specs. It's about what I had guessed but it's always nice to have good accurate numbers.

Slantzilla:

We have the same problem with limited port flow over in the "big" Ford 240/300 camp. Classic Inlines has an aluminum head in development (similar to their "small" Ford 144/200/250ci head that's in production) that should give us much better capabilities. However, due to the bad economy, that project has been stalled.

Russ

CJ,
did you grind the crank or cut and weld it to get that stroke? also wondering what pisons you are using? and how do you like it?
Paul

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71 valiant 225, 904, 7 1/4
69 W200 power wagon 318, np435, np205, d44 front, d60 rear

What happens whenn your rod ratio is under 1.5? doesn't one of the articles on the forum say below a 1.5 ratio cause problems?

Kev

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Well, I love it of course! Would I do it again? Read on!

This is a weld up forged crank. It's turned back to standard bearings for the slant. The local crank guy had it for four months before he had a "window" long enough to accomplish it. There was a lot of straightening involved to get it back where it needed to be with all that welding.
The ARP rod nuts cleared the block by 0.010" when I got it back. There was grinding involved for that. The bores are notched to clear as well.
Your likely going to spend somewhere in the neighborhood of $750 for the crank work alone. Don't enter into a stroker lightly.
By the time I took delivery, my engine assembled cost $4100. I ended up spending another $400 getting the head straightened out after the machinist fixed it, and still didn't get it right.
I've found a machinist that has a lot better idea of slants now, so I could probably cut that by a bit. Still, $4k is a pretty good number for an engine like this. It's not like building a Chevy SB. I can get a pretty hot SB built for $2100. I've built pretty nice SB LA's for about that too.

The build is a long rod stroker. Pistons are H827P50MM Federal Mogul
with a compression height of 1.268"
Bore is 3.445" Going to the next oversize on these pistons puts the Bore at 3.504"

7.005" 198 rods, cleaned up and polished, and a lot of weight taken out of them. The small end is round now.

A little more cam, and it would probably run right up to 5500 rpm with power. But it delivers on the bottom and mid beautifully with what is has!

Take a look in the FAQ under engine build matrix.

Once I get the new car together, I'll start getting serious about an A-100 pickup. The stroker engine will go into that. It'll make a seriously strong engine for that application. As it is, I've about run up as far as it's wise to go with this engine.

The metric pistons have smaller rings. In my long stroke application I've found that I get ring flutter at engine speeds over 4000 rpm. Due to the bore size, the oil control ring has a hard time dealing with large amounts of oil flowing to the back of the sump under hard acceleration. Tension of the oil ring is lower for smaller bores. With larger bores, higher pressures are possible without creating excessive wear.

Keep in mind that I'm in the deep 15's. Best of 15.02 in the quarter.
Using a Jeffery deep sump with baffles has decreased my launch oil burn considerably. It has not stopped it. I run positive seals on the valve stems.
I also went with gapless rings. They have performed well enough, but don't play well with the long stroke. At higher RPM, as I mentioned above, I get flutter. The rings don't seal consistently. Having it to do over again, I would have tossed iron in there and not worried about fancy stuff. It doesn't pay back with a stroke of this size.

0.125" off the deck, .040" off the head. 300 Ford Valves.

Look over the engine build matrix.

My new race engine will not be a stroker. The benifits of high rpm power far outweigh the few cubic inches one can gain through stroking.
Never know, I may bore it out to the 3.504" oversize and use it in the new Dragster for licensing. With the 3.50 gears, it should perform admirably in the lighter chassis.

Sorry for the long post. Hopefully it will help you in the decision making process. If your building a 4x4 a street car or tow rig, the stroker can be a good choice. Mine pulls like a nice small block two barrel rig. If your looking at a strip car, I recommend you look into something that will rev a bit higher.

2¢

CJ

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Part of Tyrde-Browne Racing

CJ,
thanks for that reply, lots of good stuff there. from what you are saying this works just like i had hoped it would. i'm looking at building an engine for a friend. he is trying to get another a100, and wants me to build him a slant for it. i figured a stroker would be just the ticket.
i know cutting the crank is costly, i was looking for a more cost effective way to stroke it. the savings in things like clearancing the block, and reworking the rods might offset the cost of the rods. longer rods and shorter pistons make sense. i was looking at the weisco pistons cause they will come in the same box as your rods, there are many other options out there.
i wanna build one!!

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71 valiant 225, 904, 7 1/4
69 W200 power wagon 318, np435, np205, d44 front, d60 rear