Thinking about 4G powered FC. Some questions.

4GFC · Post by **4GFC** » Wed Jun 15, 2005 9:34 am

Hi all, I've been reading on this forum for a short while. I just have a couple questions about those that are going the wideblock route.

Crankwalk? Is this an issue? My biggest reason for my desire to do this swap is to make about 400RWHP, which shouldn't be a problem; however, I have read some things on DSMTuners that would have be believe that the 4G64 is also prone to premature thrust bearing failure. There would no point of going from the shotty realiability of the 13B just to get some crankwalk shortly down the road.

My other big questions lay in the drivetrain. I know some are planing on using the Mazda R series transmission (B2600, 929, TII, FD3S) for the simple reason that it bolts to the wideblock. Awesome, no need to re-invent the wheel. I'm wondering though. With the bell from the B26 on a TII trans, what ind of clutch setup will be used and what starter will be used? Starion peices? I read somewhere that input shaft size and spline is the same as the Starion. What about input shaft length? Is the R input shaft long enough? What flywheel is to be used?

Thats all.
Jeremy

Mike · Post by **Mike** » Wed Jun 15, 2005 12:03 pm

Technically any engine with a crankshaft can crankwalk, but it is specifically only really a problem on 7 bolt engines. Those on DSMTOONERS were referring to the 4G64 narrow block, which are all 7 bolt except for those who use the G64B, Hyundai 6 bolt 4GCS, or the rare 6 bolt 4G64 from Mitsubishi Expos or Eagle Summits. The 4G64 6 bolt wide block, however, is much easier to come by in Mitsubishi trucks, vans, and wagons and not prone to crankwalk.

<a href='http://rebuilt.net/Mitsubishi_Engines.htm' target='_blank'>http://rebuilt.net/Mitsubishi_Engines.htm</a>

Concerning the Model R transmission, any 87-88 B2600 bellhousing may be used, including the 4X4. Being a Mazda bellhousing, the only starter that will probably work is the B2600. Since the B2600 uses a G54B engine, either Mazda or Mitsubishi G54B flywheels should work as long as they bolt up and are the same diameter as the 260mm B2600 flywheel. The clutch must basically match up with the flywheel diameter and use a 23x1 spline. If a 260mm flywheel was used from the B2600 or Starquests, then you should use a 260mm clutch with a 23x1 spline like those from the B2600, Starquests, or even the TII Rx-7. It's a relatively easy task fo clutch shops to customize a clutch setup for you as well. DJ is currently working on obtaining an 87-88 B2600 bellhousing to test the input shaft length, but at this time it is unknown whether it will work or not.

peregrine · Post by **peregrine** » Wed Jun 15, 2005 11:42 pm

</div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (4GFC @ Jun 15 2005, 01:34 PM)</td></tr><tr><td id='QUOTE'> Hi all, I've been reading on this forum for a short while. I just have a couple questions about those that are going the wideblock route.

Crankwalk? Is this an issue? My biggest reason for my desire to do this swap is to make about 400RWHP, which shouldn't be a problem; however, I have read some things on DSMTuners that would have be believe that the 4G64 is also prone to premature thrust bearing failure. There would no point of going from the shotty realiability of the 13B just to get some crankwalk shortly down the road.

My other big questions lay in the drivetrain. I know some are planing on using the Mazda R series transmission (B2600, 929, TII, FD3S) for the simple reason that it bolts to the wideblock. Awesome, no need to re-invent the wheel. I'm wondering though. With the bell from the B26 on a TII trans, what ind of clutch setup will be used and what starter will be used? Starion peices? I read somewhere that input shaft size and spline is the same as the Starion. What about input shaft length? Is the R input shaft long enough? What flywheel is to be used?

Thats all.
Jeremy [/quote]
ok. i thought you posted *FD*. i was gonna say go ls1. pardon me, but whats an FC?

4GFC · Post by **4GFC** » Thu Jun 16, 2005 12:56 am

Thanks for the reply Mike. I know all motors with a crank are susceptible to crankwalk, I've seen a 2JZ crankwalk, but even some six bolt motors have walked in the past. I just wanted to know if this was one of those motors that may be more prone to it. It would seem to me that crankwalk is caused by a lot of clutch setups where the pressure plate clamping force is increased dramatically. It seems this mostly happens with the ACT pressure plates. I would guess the added clamping and lack of oil to the bearings at startup is the key to it all.

Peregrine, the FC or FC3S is the second generation Mazda RX-7. If I had an FD, I would definitely be going the LS1 or 20B route. I'm still not putting the LT1 out yet for the FC, but I would rather be boosted than have a V8 rumble. I just like turbos I guess.

Post by **DJpowerHaus** » Thu Jun 16, 2005 10:37 am

one of the beneifts of the wideblock is using the 240mm flywheel (not 260mm). This extra diameter will hold more torque than a smaller disk so you do not need as agressive of a pressure plate to hold the same power. I'm still probably going with the baddest I can get, but whatever. The 6 bolt motors are LESS likely to CW, but yeah, anything can crank walk.

the bellhousing pattern is MITSUBISHI, not Mazda, so using a B2600 starter would work, but a Starion one would work just as well.

I still dont have the B2600 bellhousing.. but I have 5 RX7 transmissions here so I've got $$$$ loss as a motivation. Just give me some time.

peregrine · Post by **peregrine** » Thu Jun 16, 2005 11:42 am

</div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (4GFC @ Jun 16 2005, 04:56 AM)</td></tr><tr><td id='QUOTE'> Thanks for the reply Mike. I know all motors with a crank are susceptible to crankwalk, I've seen a 2JZ crankwalk, but even some six bolt motors have walked in the past. I just wanted to know if this was one of those motors that may be more prone to it. It would seem to me that crankwalk is caused by a lot of clutch setups where the pressure plate clamping force is increased dramatically. It seems this mostly happens with the ACT pressure plates. I would guess the added clamping and lack of oil to the bearings at startup is the key to it all.

Peregrine, the FC or FC3S is the second generation Mazda RX-7. If I had an FD, I would definitely be going the LS1 or 20B route. I'm still not putting the LT1 out yet for the FC, but I would rather be boosted than have a V8 rumble. I just like turbos I guess. [/quote]
then go with a turbo v8

i had a twin turbo mustang a few years back and when it was running it was alot of fun. it only ran about every other month it seemed like though. <_<

rarson · Post by **rarson** » Tue Jul 19, 2005 8:25 am

smog brings up a good point! A good way to help ensure your motor doesn't walk is to not place that pressure on the crank when oiling is low (or non-existant, such as startup). I never leave my foot on the clutch at stop lights, always go into neutral. I think even just that will greatly reduce your chance of crankwalk. Another thing, look at the numbers of how many 7-bolts have walked versus 6-bolts. There was obviously some sort of flaw, maybe some kind of casting contamination or design flaw. SOMETHING definitely increased the chance because for sure, there are more 7-bolts that have crankwalked. I would feel relatively safe with a wideblock 6-bolt (hell, my 7-bolt '97 GSX still hasn't walked yet).

GRNDSM · Post by **GRNDSM** » Tue Jul 19, 2005 9:09 am

Jeremy,

Stay away from 7 bolt 4G63 motors and you should be fine. The rest of 4G6x family engines (including 6 bolt 4G63) are no more prone to crankwalk than any other engine.

Given how 2G motors (the most common 7 bolt 4G63) do not have side bosses for RWD motor mounts, you are not going to be using it anyway. So that would be the LAST thing I would worry about doing 4G63 swap. Believe me, there are plenty of other issues to occupy yourself with.

As for clutch pressure plate causing CW… This point never seems to sink-in with some people: HEAVY(er) PRESSURE PLATE DOES NOT CAUSE CRANK WALK! It will accelerate thrust bearing wear, but it will NOT cause it… If you have a 7 bolt motor, which is destine to walk, it will walk, even if you have an automatic tranny with very little thrust loads.