the stroked 7m...again. possibly some new info?

[87hilux7mge]

so, ill be getting some parts through a trade, one of said parts is a 97.5 mm stroker crank.

after doing some math (albeit some pretty crappy math, mine sucks) i deduced that if you use the stroker crank, and a stock compression height piston, you would need a 5.85" connecting rods.

so i searched, and found these. forged eagle "I" beam 5.85" rods. so heres the difference in measurements.

stock rods:.......................................... SBC rods:
length: 5.984"/151.986mm................... length: 5.853"/148.659mm
rod journal: 2.047"/51.991mm.............. rod journal: 2.100"/53.337mm
housing bore: 2.167"/55.039mm........... housing bore: 2.250"/57.147mm
pin size: .866"/21.995mm.................... pin size: .927"/23.545mm
big end width: .977"/24.815mm............ big end width: .940"/23.875mm
pin end width: .977"/24.815mm............ pin end width: 1.060"/26.923mm
weight: 615 grams............................... weight: 580 grams

differences:
length: -.134"
rod journal: +.053"
housing bore: +.083"
pin size: +.061"
big end width: -.037"
pin end width: +.083"
weight: -35 grams

so its got larger bore for the pin and journal, but i might be able to find a bearing to soak up the extra, as well as a pin bushing. being as they differences are excessive, i should be able to find the appropriate pieces.

stock:.................................................. .. stroked:
bore: 3.307"/84mm ................................ bore: same
stroke: 3.583"/91mm............................... stroke: 3.839"/97.5mm
displacement: 184.559cid/3.024L.............. displacement: 197.746cid/3.240L
rod/stroke: 1.670:1................................. rod/stroke: 1.527:1
avg. piston speed: 3565.68 fpm................ avg. piston speed: 3814.68 fpm

so we end up with an increase of .216 liters, as well as a lower rod/stroke ratio and a slightly higher piston speed, and about 150 grams weight savings over stock (less if you go for a H beam style rod).

the benefits are, less dwell for the piston at TDC, increasing cylinder fill velocity in the lower rpm's, which should help out the large ported, long runner 7m engine in the low rpm.

the gains are smaller, but i think it could be done, and i intend to build this at a later date. if anyone has any other opinions on this subject, id be happy to hear them, as im thoroughly open to others input and calculations.

go!

[El Supracabras]

Sorry I dont have a more useful comment, but you must really love that truck .... or math. I would think the stock 7mge would have plenty of power for wheelin (maybe not boggin). I never had a problem in my old 86 samurai with its whopping 66 hp and I tested that poor little thing. Not many people have invested that much into the 7MGE, most saying the benifits are too minimal to justify the cost and effort.
I'm not against what you are doing, but why dont you use a gte setup? It's already set up for boost and capable of 400HP so you can worry more about mounting the supercharger and plumbing and installing the engine.
Just an opinion, good luck with it, i'm interested in seeing a supercharged 7m in a pick-up (or anything!).

[87hilux7mge]

Originally Posted by El Supracabras

Sorry I dont have a more useful comment, but you must really love that truck .... or math. I would think the stock 7mge would have plenty of power for wheelin (maybe not boggin). I never had a problem in my old 86 samurai with its whopping 66 hp and I tested that poor little thing. Not many people have invested that much into the 7MGE, most saying the benifits are too minimal to justify the cost and effort.
I'm not against what you are doing, but why dont you use a gte setup? It's already set up for boost and capable of 400HP so you can worry more about mounting the supercharger and plumbing and installing the engine.
Just an opinion, good luck with it, i'm interested in seeing a supercharged 7m in a pick-up (or anything!).

the truck will definitely have plenty of power with a GE, i just want to do a supercharged one for the hell of it, and too see what i can squeeze out. yea i could use a gte motor, but thats been done a million or so times. i like to do different things haha.

yea, the stroker setup is just workin with parts i have really. when i get forged pistons for 250 and a stroker crank in trade, and i only would need 220 dollar rods, my wheels start turning (probably not the best thing for me to allow). it would be sick to have a stroked, supercharged 7m, and have it be reliable still.

and put simply: yes, i love my truck ALOT haha. thanks for the reply and interest tho!

[El Supracabras]

Well personal enjoyment is what really matters and if nobody tried crazy tihs like that, the world would be a boring place.
Not sure if you've seen these already but if you havn't it should get the gears turning.
http://www.youtube.com/watch?v=EdoGnvPxXJw&fmt=18
http://www.youtube.com/watch?v=0HyhUusmQlQ&fmt=18

[87hilux7mge]

those r sick, that thing puts out some crazy power. i dont know how much power ill put out, but im guessing with the S/C about 260, more tq. itll be sick.

after the stroker gets assembled (if it ever does) then i wanna build a 22re with my M62 S/C. be pretty sick if i put the same effort into it as i am the 7m.

[87hilux7mge]

some more info and calculations to input here. ive tried to research the best i can and provide the most accurate measurements.

i calc'd the two assemblies total length:

stock:....................................... stroked:
stroke: 3.583"/91mm................. stroke: 3.838"/97.5mm
rod L: 5.984"/151.89mm............. rod L: 5.853"/148.659mm
comp H: 1.299"/32.764mm......... comp H: 1.299"/32.764mm

so, divide stroke in half, add rod and piston compression height, and we get thus:

stock: 9.0745"/230.503mm........ stroked: 9.0715"/230.404mm

so a difference of .0030"/.099mm. id say thats acceptable, especially if a shaved block comes into play.

now if i can only find a way to get bearings, revised bushings and somehow increase the thickness of the journal end, id have a cheap solution to a "more effective" stroker for the 7m.

i spoke to the machine shops around here, and none of them were confident about getting such undersized bearings, or custom making smaller bushings for the wrist pin bushings.

if i could get some 5.85" rod blanks, then id be free to machine them as i see fit, and could possibly work it to use factory bearings and bushings, as well as solve the thickness issue so i can avoid rod slap.

the only other problem i see at this point, is the relatively low R/S ratio, especially for what is considered a short rod setup. 1.6:1 is sposed to be the lowest acceptable for a short rod setup, and side loading, ring seal, rod angle and piston slap could become an issue. any thoughts??

if anyone has a line on a place that would do the machine work in the WA area, or where i can get rod blanks, chime in!

[MA70-3.0GT]

Just a suggestion, but if you had to get the big end shells made up, couldn't they include side "lips" like a crank thrust bearing to make the difference in journal width & prevent float.

I'd be tempted to agree a better solution would be 5.85" blanks machined to take stock shells & pins, guess it depends on feasibility of any solution to the narrow big end.

(actually, some motorcycles use the small end to locate the rods laterally particularly on roller bearing bottom ends. Would the extra width up there help you work a solution maybe with two piece top-hat bushings? )

[87hilux7mge]

good suggestions, and yea i did actually look into custom bearing halves for the large end. unfortunately, theres not enough room to make thrusted rods. and they have their own inherent problems.

some blank rods would help, but im not finding alot of support from rod companies either. as well as rebushing the small end. no one wants to do it

but, ive considered another idea. the alternate piston idea will work, and i found a machinist that will rebore the pistons wrist pin holes.

so once i get the money for some ridiculously overpriced honda pistons, then ill be able to maybe come up with something

its just an idea in the back of my mind anyway. ive got all the parts except the pistons as of now, so if i can find a dang job then ill be able to put some more effort into this.