Next engine

[rickwrench]

It will be time for a new engine in the delux in the next year or so, and I like to build them on paper ahead of time, it's cheaper that way. So how about this:
US 250 block bored to 3.72".
US 250 crankshaft, rod journals cut down to 1.89" (mitsubishi rod journal size) and offset ground +.23" for a total stroke of 4.14".
Mitsubishi '93-'99 4G63 rods, 5.906" C to C, narrowed .0222" on each big end face to the stock ford thickness (I measured .9935"), pin honed out to .9122". These engines are pretty common, in Mitsu Eclipse, Galant, Eagle Talon, Laser, among others.
Stock ford +.040" 6.5 cc dish pistons, 1.5" comp ht.
This combo puts the piston .007" above the deck, but when I get the used rice conrods rebuilt, I'll have the machine shop take all of that away when they resize the caps. So, zero deck.
Using a modern "thick" (.040" - .045") head gasket I actually end up with perfect quench clearance.
4.14 stroke x 3.72 bore = 270 c.i.d. and it's still a "small" six.
I've got a D7 head that I'll give the band saw treatment to (ala Al/Jack), some chamber re-shaping to unshroud the valves, increase the chamber volume 3-4 cc's in the process, good port and polish, probably a 30* cutback on the intake valves. I'll end up with about 10/1 compression ratio with this set up. A little high, but I think that an ideal quench distance, 92 octane gas, and coating the piston tops, valve faces, and chamber will take care of any possible detonation issues. I've used Techline (CBC-2/X and DFL-1) coatings in the past and they work GREAT. I haven't figured out how I'm going to cure the head coatings though, the head is too long to fit in the oven...
I'll fabricate an up and over six tube intake for either a 600 cfm Holley or maybe a Holley Pro-jection efi system (I don't know yet on that one). I wonder what kind of flow the sawed head intake ports will have.
Weld up some headers, of course.
With the extra displacement, I can run a little hotter cam, too. The most expensive part of the build will probably be the crankshaft. Stock used 4G63 rods are cheap, the junk yards are full of them. A new project for this summer, or next winter.
Rick(wrench)

 

[Anonymous]

arty:

Rick,

That's awesome!! How much do you think the crank work will cost?

arty:

 

[Anonymous]

[No message]

 

[Anonymous]

id strongly go for a OZ x-flow head, much better flow outa the box,

everything else seems alright.. i am sure xecute will be happy to reel of number about machine work as soon as he reads this thread... in fact i think he wont even read the whole first post.. he'd be too keen to answe

cheers.joe.

 

[80broncoman]

I have never looked at one but it might save a headache if you look and make sure that the rods will clear the cam. look at the stock rods and the new ones compare thickness (from crank to outside). And look of course at clearence between cam, crank, and rods in motion. Once you have a number
you can do the math with the new stroke.
Hope I didn't dampen dreams for this , but it is better to find out now than on the engine stand.
Jim

 

[xctasy]

Lookes great. The 250 cam is moved up quite a bit on the 200, so hopefully there should be clearance there. The base circle diameter may need to get shaved.

The rod ratio and over lap. 1.42:1 is as low as I've seen with a hot six. The overlap should go below 210 thou.


The benchmark I've seen work suprisingly well in the past is the Holden 235 stoker. Started out as a 202 cube 3.625 by 3.25" (201 cube calculatied), and then it gets its crank biffed for a 221 Ford I6 crank. That gets offset truned down to 1.89, a set of 5.25" Holden rods added, and thats a stump pulling engine combo. Final combo, 3.685 by 3.685". Rod ratio 1.42:1. Pistons were shaved down to 1.555" Federal Mogal or Speed Prp forged, a Falcon 250 design running in a 1.62 in those days, which were avialable untill 1990.

I don't like poor L/R engines, especially ones that push the envelope on a six with only 10 counterweights. The torsional vibration period is very intense on some sixes, and the automaker does many 300 hour tests to get the durability right.

But 270 cubes is 270 cubes! Since the four cylinder components are always subjected to more bumps and jounces than a six, the componenets shouldn't be a problem. Mallory metal may have to be added to balance things up, but I'd say go for it.

The overlap is supercritical as panic says. Don't go over 5000 rpm with this beast. Make the torque do the walk!

 

[80broncoman]

Scariest crank I ever saw is a pontiac 301 bent 8...... care to guess how many counter weights?..... you have to see one to belive it ..TWO!!!
One each end. This engine is a very light engine.
Olds 307s had widowed main webs in the block. Thats right, they had holes cast in them. You can't get any thinner than that. Good thing somone didn't try to combine the two.
Jim

 

[StrangeRanger]

Thought of reducing your stroke by .007" and leaving your rod centers alone? It would lessen your displacement to 269.5 CID but it would give you just a bit less machining to pay for. Actually since you would probably need to deck the block anyway as part of the blueprinting process, you might want to take another .010-.020 off the stroke, it's not going to cost you much displacement and it is going to give you more clearance on the camshaft.

 

[rickwrench]

No idea on the cost of the crank work. I'm sure it's gonna be quoted as pricey though. More than a V8 crank, as there are six throws to index and offset as opposed to four. I'll see what kind of deal I can work out (I can talk!). I got a great deal on cutting a half inch off a buick 350's mains. I thought (a little) about the crankshaft overlap issue, but the 250 doesn't have much overlap to begin with. I figured a quarter of an inch difference in overlap is a lot less than some of the cuts I've made on Buick cranks, and no ill effects. I'll just make sure the grinder leaves a nice big fillet radius. When cranks break, the breaks start right at the inside edge of the rod journal or the outside edge of the main, grinding in a generous fillet radius is great insurance. Also, there is only one rod per throw, soooo..... we'll see. Since I installed the T5's and tachs, I don't think I've revved either of the Falcon engines past 3800-4000 rpm. When I was running ford-o's, who knows what they were revving to. I'm not chicken about revving, my Corvair sees the redline about every other time I drive it. The exhaust note at 4500-5500 rpm getting onto the highway is very addictive, at around 4500 rpm the cooling fan cavitates, and suddenly you have no fan noise and an extra 15-20 bhps, whooooosh. If it only had heat... I just don't seem to rev the Falcons that much. Both motors I have are stock(ish) torque motors. I briefly (2 mos.) had an Edelbrock tri-carb setup on the Squire, but I don't think I ever really got fully into the secondaries the entire time it was on there, and I got crappy mileage to boot. Heck, 4 door station wagons aren't sports cars, and with a jumbo torque I6 motor I'd probably just shift even earlier. I like the serious 1500-3000rpm grunt of these sixes more than the rev. Extreme piston acceleration is what kills cranks (and rods) anyway, not low end torque.
When I take apart the 250 core I'll check the stock rod to cam clearance. The stroke does get a nice increase but since the journal is smaller so is the rod. It still moves out some, so, before anything else gets done, I'll make sure of cam clearance.
I thought about dropping the .007" of stroke when doing the calculations, but I've never seen a re-sized rod that was within .005" of it's original length.
Rick(wrench)

 

[Anonymous]

[No message]

 

[rickwrench]

Hi Panic, I've hit your site a few times in the past, always full of good info.
It turns out 4G63 rods sit on a 1.772" journal instead of 1.89" (which is the rod bore - no bearings - oops). So pretty much no overlap at all.
On the other hand, while I was playing with numbers, this interesting possibilty came out of nowhere. It's been said that the 200 can't be stroked because any stroke increase will cause rod interference withe pan rails, and cam. Has any body done a reduced/offset journal stroke? With a reduced journal the rod ends/caps pretty much stay within the same dimensions, the rod beam moves out a little, and if there is going to be interference anywhere it will be here.
If you offset grind the journals to 1.889" and 3.36" stroke (a weld-free offset), use Toyota 3TC 1.8l rods (1.4835" c to c) pin honed to chevy size (.927"). Use Keith Black 3.736" dia. 305 1.261" c/h flat top pistons (#kb153). You get 221 cid. The piston sits .032" down in the hole and with a 62cc chamber head, an .040" head gasket, you get 9.1/1 compression ratio. The dreaded journal overlap on this combo is .389", which is better than the stock 250 (.306"). I don't know if it will work without hitting the cam, though.
Back to the thinking room on the 250.
Rick(wrench)

 

[Anonymous]

Cam interference would make me very nervous, but the pan rails can frequently stand to be "trimmed" a bit w/o consequences.