7 Bolt Rod Question

Ok so I have a set or 7 bolt eagle rods and wiesco pistons sitting in my garage, onlt 350 miles on them from an old project. Now I have been looking into the differences in the rod big end from the 7 bolt to the 6. The diamiter is the same at 1.771 inches (thats the good!!) The width of the 7 bolt is thinner by .079 inches. Now that doesnt hold any oil pressure back from what I am aware(correct??) If the side of the rod ever actually touched the crank then wouldnt there be bearing material there too?? And wouldnt my rods have some wear on them in that area?
Thanks Guys
-Greg.

 

Come on guys, I know someone know more about engine oiling systems than I....

 

[atc250r]

I wouldn't do it. The rods moving horizontally on the crank is just begging for bearing wear and likely bearing damage. I believe Curtis had a friend that tried running an Evo8 piston and rod combo in his 6 bolt and it worked OK for a while then failed. Hopefully he'll chime in here.

John

 

Oh thats the kind of answer I was looking for. But yeah that would be cool if he chimes in. I want to know more. In my head it would work but I do see what your saying about them wearing funny because of the rod being about to move by close to a tenth of an inch.

 

[atc250r]

Yeah, and the tenth of an inch of side to side is more than enough to interfere with the mere thousands of clearance that the bearing has to the crank journal. Once the bearing touches the crank a few times it doesn't take very long for rod bearing failure to occur. 6 bolt rods are good for 500whp on a decent tune, just use them rather than "hack" it with the wrong size rods. Once you factor in the hours you'll spend building and installing an engine it cheaper to do it right than to do it twice.

John

 

Yeah I actually have a set of 6 bolt rods sitting right next to them, So I will probably just send them both to the machine shop and have the piston end of the rod machined down to fit the pistons I have.

 

[curtis]

Greg........ Curtis here chiming in. Hold on this is going to take a while might want to go get a snack and a Mtn Dew or a frosty beverage GVR4 drinking team your responses will be welcome.....

My buddy put a set of evo stuff in a 6 bolt motor everyone said "oh it will be fine" it wasn't knock sensor going off due to the fact the rods were shifting.

Now the cure...

I've been dealing with this problem as well actually its all I lack, well that and the turbo. I just sold the s362 but I've found a 400 series I'm looking at that flows up in the 90 to 95 lb per hour range. /ubbthreads/images/graemlins/idea.gif. I have two butchured cranks here and lots of other toys ready for install but the motor comes first. I bought a set of pauter x beam 7 bolt rods with 20 over aries lightened pistons. I have these and plan to make them fit only delay now is if I want a 4g64 de-stroker or not. Theres plenty around here in the yards its just taking time and tools to the junkyard to get one out.

I have a new PTT dual disk so not going 7 bolt so I'll make all this work by either buying custom pistons for the 4g64 or just staying with a 2.0 liter.

Now the cures I've thought about.

Simply weld a bead around the journals and machine to fit but everyone around here doesn't want to do it because it side loads on the stone which will wear the edge down and then they'll have to reset up the machine. Welding also brings up the fact it may warp and have to be re-straightened, nitrated, cryoed etc. The price of all that would be as much as new rods.

First Bill Miller Engineeering does pistons for Nascar that use Honda size thin rods in a Chevy V8. I've talked to them on the phone and the owner Bill told his engineer I was on the phone with to send a set and they could build them. But thats after I make a decision on which block...... The pistons hold the rod centered in the bore only shift would be the pistons. Rod centering pistons on ebay look close at the bottoms

Second is bearings I found that Mazda in europe has a small diesel engine that has 45mm crank bearings which means the trust could be used on each rod. THATS BUYING 4 SETS OF MAINS BUT I'VE WENT THIS FAR SCREW IT I'M FIGURING SOMETHING OUT... But since its in over the pond the chances of finding good specs and info is out.

Third and probably the best solution so far is Ducati yes motorcycle I found also on google that Dukes have the same size crank as the mazda and our rods. I also found that the ducati's have roller bearings on the crank so a set of needle bearings on our crank would eliminate 95% of start up rotational drag. Yes 95% I've done alot of reading on this. I went by our local bike shop but they don't do ducatis so My next stop will be Nashville when I get a chance to make a trip down there. I think it was out of a 996 engine I found.

Now another thing I checked on last week was a torrington bearing on each side of the pin. I took a piston and rod to a industrial bearing supply house and we checked in some books and found that I can get some that are just a little larger (metric vs english system) but the thickness would be off and would have to build a piston jig and mill out the internal distance on each side. Then ad the weight of the bearings that doesn't fit anyway. /ubbthreads/images/graemlins/banghead.gif

Now the guy behind the counter had a seriously crazy thought and It may work. He checked another catalog for snap rings. He found snap rings that were like 2.4 mm thick and 21.something in internal dia, so one on each side of the rod floating on the pin would keep the rod from side loading against the crank. There hardened steel so that part would be fine, just kind of seat of your pants lawn mower repair.

Now another option would be to simple machine spacers out of aluminum or manganese bronze and put next to the rods and the pistons. Weight wouldn't be that great but they would have to be perfect fitted due to inertial forces slinging them around. They could go out of round wear and come apart.

I really think the best bet will be a set of bearings with thrusts but finding them has been the hard part as with anything else there's no specs or pictures just part numbers and applications.
This I believe is the best cure because your not pumping all the oil out and flinging it off the crank. and with a needle bearing set up it will rev just like a bike. Which is what I want. If the thickness is off I'm sure needle bearings of different lenghts can be found. Most needle bearings I've read about have side thrusts to keep the oil from flinging out, I even found a company that is in the process of building automotive bearing replacements but after a few emails into them I gave up.

Lots of people around here think I'm pill taking crazy but I like solving stupid problems I force on myself to save a buck but I have figured out alot of silly crap in the last 38 years and God willing will be able to keep it up. All this is mainly because my last car cost me tons of money, 4 engines,7 transmissions, 3 rearends, 6 sets of aluminum heads, numerous clutches, nitrous kits, twin turbo kit, cage etc. After it was all said and done I got about 10% of what I spent out of it, The galant on the other hand is cheap when you build or scrounge around for ebay parts, parts here, local friends etc. Building is the fun part with me don't know what I'll do when its finsihed this time. I guess sell it off and buy a pile of chromemoly and start welding up an atom or something.

Just google search 45mm thrust bearings etc and see what else you can find. If you find anything let me know with a PM and we can talk on the phone. If anyone else has any thoughts post them up.

 

[Dialcaliper]

Curtis, I don't know about the cost comparisons, but if you're going to go through all that trouble on the engine, why not have a custom forged crank made to fit 6-bolt mains and 7-bolt rods? It's something that could probably be made from a 6-bolt blank, simply by cutting narrower rod journals. Magnus sells shelf stock cranks for $1600 - whoever they have make them might do it (heck, they do custom strokes), or a company like SCAT could do a custom one. I know there's definitely the urge to do something yourself, but kludging something together that can ruin all the other hard work you've done doesn't seem worth the savings.

Barring that, the thrust bearings are probably the way to go. The car you're looking for with 45mm mains is the Mazda 2 Diesel sold in europe. You might also try medium displacement motorcycles (the big engines like the hayabusa use larger, and small engines use ball bearings)

I would certainly rather DIY on a lot of things, but sometimes there are things that the right pieces and tools just aren't available.

 

Wow I am SO glad that someone wants to try stuff like this just as much as me! Ok I think the way I am going to go with is using the thrust bearings. Now all the info I have is that the inside of the rod without a bearing is 1.890 (48mm) the inside diamiter of the bearing has got to be 1.771 (45mm) the width of the inside of the bearings thrust part(not sure the technical name) is 1.038(26.365mm) and the outside width of the thrust has to be 1.117(28.37mm). Now with that said, that gives me a .0395(1mm) thrust part of the bearing. So tomorrow I am going to call clevite but I wanted to put these numbers up so you could double check them with your numbers and see if you get have the same. Basically I am going to give them the info and let them search for them. Clevite Catalog 872 pages is more than I have time to go through, So I am sure they have some kind of better way of finding something on there end.
I really thank you for spending that much time to let me know where you are at in this search. Oh by the way the welding and machining of the piston was one of my first ideas and the machine shop quickly put the X on that one.
-Greg

 

[Dialcaliper]

I actually did just go through the clevite catalog searching for "1.77" and scrolled through the search results looking for "main bearing" and skipping any that have the "thrust washer" note.

Everything that came up as a main bearing was no joy; the suzuki swift 3-cyl, some hondas and diahatsu engines use separate thrust washers. Also ran across some "cam bearings" and "auxiliary shaft bearings". I'd bet money that they all just use standard rod bearings for the mains, with special small thrust washers to cut costs. Makes perfect sense now, especially since any small engine is built on a budget. /ubbthreads/images/graemlins/banghead.gif

Odds are high that the Mazda 2 is the same. So it's highly unlikely that a one piece bearing exists, much less fits unless there's a motorcycle, but it's probably the same story there.

The 7-bolt rods are narrower by only 1.4mm, so there's not much to work with there. You might be able to bore out the rods and make a thrust bearing shaped shim out of heat treated steel or bronze that rides in between the rod and the bearing, but the sides would be awful thin (.030" per side is sheetmetal thickness /ubbthreads/images/graemlins/ooo.gif ). Maybe you could cut the rod journal even wider to allow a thicker shim?

 

[curtis]

^ Man that the problem no one wants to cut the sides of a crank. As for a custom crank I've already thought of that a friend of mine had a storker crank built down in Memphis for his 7m supra for 700. It turned a 3.0 to a 3.6 or so what ever gives a 101mm stroke is what he had done. No cutting rods are no problem. Greg if you find a thrust bearing that will fit on the crank perfect the rest is easy ....Lets say the crank is 2 inches side to side and the rod is 1.75 and the bearing you find is 1.6 in between I can cut the rods down here on my mill..I can cut to 4 decimal points so I can get it perfect.......... you find us bearings I'll take care of your rods for you. Theres many kinds of thrust one piece on each side with journal bearings for the middle 2 piece with journals and half a bearing in the middle and the same as the last with needle bearings. I'll do some more research tomorrow. I just spent all day fixing the mower and getting leaves up. I want a shower and food .

 

Well I have been talking with the guy from clevite and I totally confused him so I had to make a picture and figured I would through it up here.

 

[curtis]

Sweet now the 1.038 is flexible as well as the thickness of the thrust. As long as the journal width fits the crank and it has a trust on each side we can thin down our rods to match our bearing.

 

[Dialcaliper]

Hmm - I just thought of another solution:

All of those 45mm cranks use thrust washers....

Machine a circular step for the thrust washers around the bore of the rods, as well as a locking slot for the lug with the right depth to bring it back to 6-bolt rod thickness. I would definitely put the locking lug in the rod rather than the cap. Diagram of Thrust Washer. I think it would be easily doable with a properly trued mill or lathe.

The best part is that you should be able to order the washers separately from the bearing sets. After that, you just throw in 6-bolt rod bearings and go. You're not limited to whatever light-duty rod bearings the OEM chose for the tiny engine, and no crazy custom bearings are required, and you can customize the clearance. As long as the step is sufficient, and the clearance is tight enough, I don't think you should have any problems with the washers flying out, as oil pressure should keep them in place. It might be worth looking into pinning them in place with press fit pins or even recessed flush rivets if you need piece of mind.

 

[grocery_getter]

Guys, I've been following this discussion here... and one question pops into mind. Why not just use a 7 bolt block to go with the 7 bolt rods? Is there something I miss?

 

[curtis]

I'm not sure with Greg but with me I've already got a new PTT dual disk for a 6 bolt and I have the 6 bolt crank I started butchering down and also a butchered 6 bolt crank thats done and ready to fly I snagged up on ebay, then all the little stuff that may not work on a 7 blot as well as a day of standing over the block de-burring . So by going 7 bolt I'll be going backwards

 

Well this may actually sound stupid on why I dont want to build another 7 Bolt but here goes... Once apon a time I wracked up a HUGE credit card debt with my 95 gsx and built my 7 bolt... spent 4200 dollars and 365 miles later the thing crank walked... at that very moment I decided that I will never own a credit card or a 7 bolt again in my life. (and I just cant put a 7 bolt in the galant with out feeling like I am taking the sack out of the bull) Oh and I am one to try to invent something, fail, try it again, fail, try it again....(you get the point)
My saab has a hydrogen generator in the trunk.... enough said.
-Greg

 

[grocery_getter]

Greg, that first failure was because you are building your 7 bolt from your 95 car. Try building a 7 bolt from a 99 car, with the separate thrust bearing style. I think you will be very surprised. The '99 7 bolt block has so much more build in advantages compared to the old reliable 6 bolt from the performance stand of view it seems extreme to me to try to build a 6 bolt just for the sake of it. It'd be different if a 6 bolt core and components are all you already have available to you (like Curtis).

 

Oh yeah well I got a block sitting in my garage... I probably should have told you that. Haha. /ubbthreads/images/graemlins/blush.gif But just so everyone is aware BEARING COMPANIES SUCK TO WORK WITH!!!
I will keep everyone posted even if you dont like what i am doing /ubbthreads/images/graemlins/devil.gif

 

[curtis]

^exactly the decision I've come up with. Emails to every company I can find and nothing in response.

I'll go ahead and share this. I sent this to Greg in an email other night.

Timkin rollerized engine video

Now I read in some ducati books on the web that the journal of the crank was 45mm id and 80mm od which is huge. /ubbthreads/images/graemlins/dunno.gif