7 bolt build? or 6 bolt swap?

[99vipereater]

I am going to be building my car for around 500HP and keeping the 2g head for its better designed Intake runners. I will be putting an eagle 100mm crank in it and some nice race bearings so I don't think I'd have to worry about crank walk. Also the main journals are shorter in the 7 bolt less friction= less work for x amout of horsepower right? That and I like the fact that the main bearing caps are all forged into one peice vs. several on the 6 bolt which i would have to modify for a 100 mm crank.The question is should I build a 6bolt botom and swap it or just build my current bottom end?

 

['97boostinGST]

Like 3/4 of the members will tell you to do a swap.
I myself am going with a 7 bolt forged.

 

[kbiker76]

If its the 99 engine I think you should be good. The later model 7 bolts aren't as prone to crankwalk because of the changed thrust bearings.

 

[7naYRu7_rs]

dont worry about crankwalk on the 99 7 bolt engines. they have been redesigned with a new thrust bearing i believe. and i think a stroker kit will be pretty cool!!!

ah you beat me to the reply kbiker!!!

 

[rocketfish]

ive read so many articles on crankwalk. The percentage of motors that crank walk ACTUALLY happens to is minimal. This being said, yes it is a design flaw, when and why it happens unkown. I prefer to use the 6 bolt just for a peice of mind, but ive seen plenty of 7 bolt built motors run for years with good power and no problem. roll the dice my friend!

 

[force_feed]

Build the 7 bolt!

 

[LiquidX]

Build up your current block bud! IF you could find a bare bottom end for dirt cheap and it's 100% fine I'd then say grab it but I wouldn't sweat it. Lighter internals FTW!

 

[FLASH1970]

The 99's and some of the 98's have a split thrust bearing design like the EVO's have. The chances of a late model 7 bolt block crankwalking are about as likely as a 6 bolt... If your current engine needs a rebuild, just rebuild the engine in the car.

 

[99vipereater]

I am going to do a compression test to see how badly it needs rebuilt. It has 120k on it and no problems thus far. It was basicaly a 1 owner (father son) when I bought it and well maintained by the dealership.

Ive got a few supporting mods on it right now, getting ready to do a timing belt job, new cometec head gasket, arp studs, and other maintinance items. Plan is to run it stock on my E3 16G for a while save up a big chunk of cash and build a stroker with GT35 HTA.

Thanks for the feedback its nice to hear other dsm'rs reinforce my original notion that my 7bolt would be just as reliable built as a 6bolt lower.

 

[99vipereater]

So I ripped the motor out and am sending it off to the machine shop next week. Rebuilding the bottom end all stock for now with some ACL bearings and doing all my head work cams, springs, valves, port, ect. Then I'll stroke it in a couple years when I get sick of tweaking with this set up. Thanks for all the advice guys. My block even has two shims on either side of the center main to adjust thrust play. Don't know if that is something new when they redsigned it or not.

 

[DSMsOwnYourV8]

I was recently having this same debate, but then I found a cherry 98 GSX with a 6 bolt swap and forged bottom end for a really good deal, and it kind of made my decision for me.

That being said, I would probably just build the 7 bolt if I was you.

 

[95weclipse]

ive read so many articles on crankwalk. The percentage of motors that crank walk ACTUALLY happens to is minimal. This being said, yes it is a design flaw, when and why it happens unkown. I prefer to use the 6 bolt just for a peice of mind, but ive seen plenty of 7 bolt built motors run for years with good power and no problem. roll the dice my friend!

Sorry but if you have read SO MANY articles on crank walk then you should know why it happens on the early 2g 7 bolts 95-96.5....but it does not happen on the 1g 7 bolts... 92.5-94 (I believe these are the years for the 1gs)

Its all in the OIL GALLERIES on the block, if you take a 1g 7 bolt and look at it from the bottom you will notice that the oil squirters are like a 6 bolt and have their OWN passage. On 2g 7 bolts they use the same oil supply as the main bearings. The squirters are basically a check valve but when "crud" gets in there it will stick open that check valve and to much oil will be lost through that squirter which in turn destroys bearings because of the oil pressure loss. If you remove those squiters and tap the hole you can put a set screw in place and this will rid the early 2g 7 bolts of the dreaded crank walk.

 

[eltitillo]

yeah man im rebuilding my 7 bolt with forged internals and im doing some real research to find the cure to this crankwalk and im rebuilding my 95 engine that crankwalked so i will let you know what is the results

Sorry but if you have read SO MANY articles on crank walk then you should know why it happens on the early 2g 7 bolts 95-96.5....but it does not happen on the 1g 7 bolts... 92.5-94 (I believe these are the years for the 1gs)

Its all in the OIL GALLERIES on the block, if you take a 1g 7 bolt and look at it from the bottom you will notice that the oil squirters are like a 6 bolt and have their OWN passage. On 2g 7 bolts they use the same oil supply as the main bearings. The squirters are basically a check valve but when "crud" gets in there it will stick open that check valve and to much oil will be lost through that squirter which in turn destroys bearings because of the oil pressure loss. If you remove those squiters and tap the hole you can put a set screw in place and this will rid the early 2g 7 bolts of the dreaded crank walk.

im working on that

 

[95weclipse]

Well if your building it with forged internals then do it asap. I would have a machine shop do it. or you could just buy new ones and have them installed and if you keep your oil changed then you should never have a problem with crank walk

 

[spanksterer]

build the 7 bolt it will be all good

 

[spawn87]

i was going through the same dilemma couple months back and after much search on the forums i decided to build a hybrid motor 6bolt bottom with 2g head.

all you need is to customize one motor mount and bore out the head bolt holes on the 2g head. get the best of both worlds. thats my 2 cents.

 

[99vipereater]

i was going through the same dilemma couple months back and after much search on the forums i decided to build a hybrid motor 6bolt bottom with 2g head.

all you need is to customize one motor mount and bore out the head bolt holes on the 2g head. get the best of both worlds. thats my 2 cents.

Yea unless you have a late model 7 bolt then I don't think there's as many issues with crank walk. Besides evos are 7bolts just well refined.

 

[spawn87]

well if your going to build a block the 6bolt is already a stronger foundation IMO

ive owned a couple DSMs and never had any crank walk issues so i can't say anything about that but as far as the evo goes, same code for the block but not the same thing as ours. more refined, yes. but for us to compare to an evo is really saying alot.

in any case i was just offering another suggestion that takes the best of both gens.
good luck with your build.

 

[johnnybies]

Its slim to none that it happens really. i mean most people are just thinking better safe then sorry.

 

[99vipereater]

well if your going to build a block the 6bolt is already a stronger foundation IMO

ive owned a couple DSMs and never had any crank walk issues so i can't say anything about that but as far as the evo goes, same code for the block but not the same thing as ours. more refined, yes. but for us to compare to an evo is really saying alot.

in any case i was just offering another suggestion that takes the best of both gens.
good luck with your build.

I was not comparing our cars to an evo, just stating that Mitsubishi stuck with the 7bolt crank. So it can't be that bad of a design just needed some tweaking which it sounds like it got in 98-99+

 

[99vipereater]

Built the 7bolt forged internals stroked it and built up the head and threw some nice 272 cams to top it off I just put the motor back in the car and I will post up a video and some HP numbers when I get it dynoed. I think this was a really good route to go and will keep everyone informed with any reliabilty issues that I hope I don't have. Anyone looking wondering wether to build a 7 bolt or not I would recomend it if you (A) Have the split thrust bearing design. or (B) Are not building some monster for strictly drag racing.

 

[91stocker]

Why do i remember reading something about the 7 bolt blocks being a major pita to clearance for a stroker bottom end?

 

[99vipereater]

Why do i remember reading something about the 7 bolt blocks being a major pita to clearance for a stroker bottom end?

I have no idea my shop did the rotating assembly. I know on the 6 bolt you have to trim the main caps so they'll clear with the added stroke.