Has anyone ever run into a shop that said the 7 bolt has structural issues that would cause them to advise against building one up? I got one shop saying "The cranks have some hardness issues due to their nitrating process" and "Beyond the hardening issues 7 bolt rod journals are not as thick as 6bolt and allow less surface area on the rod bearings and are more prone to issues"

so they do not offer a warranty on any 7 bolts they do build up if customer wants to go ahead...

stock 7 bolt can handle upto 400WHP. Do you need more than that? I think shop is using "structural issues" as an excuse not to give you warranty to save cash if they f*ck up your build

What shop is this?

7 bolt rods are thinner than 6 bolt rods and a 7 bolt crank is not nitride coated from the factory.

Rob C. in 5..4..3..2..

That's a good point, we actually had a chat not long ago about 7 bolts, and Rob brought up some good point. let me see if I can dig it up.

It was another thread but I did find this one:
http://www.ca.dsm.org/forums/ubbthreads.php?ubb=showflat&Number=363919

Welcome back Steve.

I know an excellent machinist in Belleville if that might help.

Ghislain

I have been past that point for a few years now, time to look at 700 as a goal

Same guy that did my 6 bolt.. Rob Vine @ Carquest on Harriett st. He does excellent work.

Good read here but CW is not my concern at all with this block just the crank coating and the thing about the rod journals, from what I gather having the crank nitrided is my option here.

can't say, but they are a great shop to deal with...they are just making sure I have all the info before I make my decision.

With numbers like 700hp you should probably be looking into a forged crank.

This is what I have been refering to when trying to decide what to use for my build.
https://docs.google.com/spreadsheet...tYW5BMFlSeFdGUTFEOXBxaVE&usp=sharing

I'll chime in here I guess. (Long boring post warning)

I'll start off with saying Im no expert, and take my opinions with a grain of salt.

First, I built and machined my 7 bolt for two reasons. First being I already had a 7 bolt to build. Second I wanted to try something different as I had already had 4 6 bolt builds and a few more than that machining favors for friends under my belt.


I'll mention here what I feel are the drawbacks to a 7 bolt, and how I overcame them.

First, oil starvation of the mains, and more importantly the thrust, due to the check valves in the squirters sticking open at low RPM when they should be closed causing premature wear of the thrust caused by design of location. They share the feed to the mains rather than have their own supply from the main galley like 6 bolts.

My solution: Blocked them with 6 mm dowel pins. Its a press fit, and that was done. After three days of reading, searching, and contemplating, I decided they weren't going to cause ill effects by doing so, especially since I am running meth, which will help cool the piston, which is what their function is for anyways.

Secondly, no factory nitriding. To me, this is bad for some reasons, and also I dont think it matters in MOST cases for some reasons.

First why its bad. Nitriding is a HARDNESS process of the surface. It DOES NOT make your crank STRONGER so to speak. Mitsubishi probably didn't do it after the 6 bolts because it was unnecessary for their new improved design. Boy were they wrong. Nitriding or not does not effect the structural "strength" of the crank, and in my opinion, "MAY" even cause it to be weaker. Hardened areas are more brittle and will crack before they bend.

The advantage of a nitrided crank is so when your motor is starving oil, and your bearings begin to wear and touch the crank, its hard enough that it wont disintegrate along with the bearings.

Example, All motors are prone to crank walk. The reason 6 bolts lasted longer, and what leads me to believe there is so much propaganda towards the negative of a 7 bolt, is because 6 bolts had stronger surfaces on the crank that didn't wear as fast as 7 bolts when starved of oil (for long or short periods) and secondly 6 bolts had no crank sensor to get kicked out and be in short a fail safe to get a rebuild like 7 bolts did.

Im not convinced that nit-riding a crank benefits high horsepower motors, but rather is just a fail safe to save your crank when things start to rub, or there is a lack of oil pressure.

When I built my engine, I did something which I find is probably going to be worth while reliability wise and performance wise. I doweled the 7 bolt girdle (which a 6 bolt doesn't have BTW) The girdle is also what attracted me to a 7 bolt. Its sheer beefiness just screams that this bottom end inst twisting. Why is twisting under stress bad? Things begin to touch. See where Im going with this?

So, First I dialed up the block straight on the mill, picked up the center of each main within .0001", and pitched in two very accurate holes for hollow dowels where the main studs go on every main.

Then I did the exact same thing to the girdle. Now I can clamp the girdle tight to the block with ARP hardware, and not worry about the center-lines of the two halves distorting away or getting oval.

I checked. I torqued the girdle down after the doweling, and used a bore gauge to check the ovality of the main bores. All within .0005" roundness. You cant ask for better than that. I also built a split thrust block, so worrying about some slight distortion of the thrust bearings because of torquing the girdle is non existent.

I'm building a stroker 7 bolt as we speak for a spare motor. The only thing I'll do different, is o-ring the block. I wish I would have taken the time to do it to my 2.0L, but oh well.

Another thing I'm going to do, because I'm road coursing this car, is nitride my stroker crank. With all the twists and turns and starts and braking, there is likely to be a little starvation at times because im not that hard core to go dry sump. the extra hardness of the crank should help protect it when times are tough.

Ive had a 6 bolt and a 7 bolt side by side cleaned fresh out of an ultrasonic tank, and had the chance to visually compare the two blocks.

The differences favor the 7 bolt. Less casting flash, more radius's instead of square corners, a big beefy girdle, and less casting flash in the oil return holes to the crank case from the head.

I'll also add, anyone building a 7 bolt, probably doesn't use the OEM rods and pistons, so the size of the rods argument is thrown out. If you are building an OEM 7 bolt, just throw in OEM 6 bolt rods and pistons for the stronger rods.

Again, just my two cents. I believe its all propaganda, and a 7 bolt can be made just as good or better as the strongest 6 bolts have been made with the right approach.

In short, your shop is slightly misinformed, and just watching their back due to the bad rep of the motor for obvious reasons (crank walk)

If you DO nitride you block, make sure you CHECK IT AFTER, cause despite the claim that it doesn't change the size of a journal, it CAN!

Omfg I just had epilepsy x 10000000

Dont you have some Dim Sum to make or something ?

Let's not get into this Mr. I have 1 more bolt than you

You asked for my input, I gave it. Last time I share technical thoughts around here for a while. Back to the skirt thread

Nono, that was good. A little more than we probably bargained for but good.

You know you're OCD wheennnnn....

Good info Rob


Lets change directions a bit...
7 bolt vs 6 bolt piston/rod naked. Enjoy it

Ignore him Rob. All he does is sell over priced Hondas. That was a very good write up

I dont think he sells too many at that with all the time at his desk spent post whoring this place

The difference is pretty significant!

For all the people that tried to open the file I linked I have changed it to anyone with the link can open it now.

https://docs.google.com/spreadsheet...tYW5BMFlSeFdGUTFEOXBxaVE&usp=sharing

Hey we're still steady...slow and steady obviously

That's an obvious difference in thickness. I can't say I've seen the rods and pistons next to each other in a pic before.

Still standing by my 6-bolt's. Although I gotta say, after reading your write up, I'm tempted to go back to 7 and go through the oh wait..that's a waste of money, nevermind I already committed to Ruben's built 6 bolt.

I'm still on the fence about sealing my oil squirter's on my 7bolt, I want to do it for the security but I'm kind of worried about my OEM pistons with 220,000km on em..

Rainbow says I should keep them as long as they pass inspection.

Why not just buy new ones if its a concern of yours? They gotta be what, a few bucks a piece?

Techniclly if you allways have good clean oil.. then you should never have to worry about your squirters.

<---- believer in that squirters are not the cause of CW.



Altho I dont see tearing a 7bolt apart.. and putting the stock oem rods and pistons back in. Atleast invest in 6bolt internals or aftermarket.

Why not ? They are good for up-to 400-450 whp. That's a lot of power that not many DSMers ever get to. Stock OEM is garanted to work right and cheap!

As shown in my spreadsheet, if you want to be safe for the 400 range you can go with the 1g rods and 2g pistons.

LOL Alex, I see you started pulling apart one of your cars and have changed your signature to indicate this

Yep watch chars disappear when I pull tranny tomorrow. Some nice stuff coming up for sale soon

One more adventage to 7 Bolts is lighter reciproccating mass which should be good for a Corner Carver kind of Sled.

Some have rebuilded 7 Bolts using OE Parts with excellent results.

Keep us posted Steve.

Some great info on here!! Will definitely help with my build aswell.

Latest email from them after further consultation: This makes me feel better about my decision to build a 7 bolt

No matter how clean your oil is, there will always be carbon deposits throughout the motor over time and the squirters WILL stick.

repost. oops

Is it the squirters themselves, or the check valves? I think someone said they are not that cheap? Maybe in the big picture of an engine build, but they ARE around $100. for the check valves, and around $165. for the check valves WITH the squirters.

for those who wakeup in morning and worry about weak rods in 7 bolt watch this evil tsi stock 7 bolt pass.

I think you're thinking of 6 bolt squirters Ziggy. The 7 bolt design is very different from the 6 bolts. As far as I know, the 7 bolt squirter is all one piece (with check valve included), but one of the 7 bolt guys would have to chime in on that.

Jeremy, you are correct. My mistake. I WAS thinking of the 6 bolt squirters.

Also, Tim Zimmer's built '99 7 bolt puts to rest any doubts that 7 bolt can't be be build to handle power like a 6 bolt: