Leforce

The car is equipped with a 4.1L BC stroker, Darton sleeves, 100mm bore pistons, twin turbo kit (GTX28 x2), & a Hollinger sequential gearbox. While the car was being tuned on the dyno, motor oil started leaking from the block, it was obvious that the block had cracked. The tune was almost done, reaching around 750 whp. The block had multiple cracks in the crank case , (check the attached images). During the tune the car was subject to hard/harsh gear shifting as we were setting the ignition cut needed for the flat shifting feature. I wonder if that had caused such block damage or whether the VQ35DE is generally weak for such power level. I also wonder if installing further mods such as aftermarket main caps & girdle could've prevented such issue.
I'm currently searching for a another block, I'd appreciate your feedback how to prevent such issue from happening again.

dkmura

iTrader: (64)

Sorry to hear about this failure, but at least it didn't happen during a race weekend. While I'm no expert, you are obviously exceeding the design specs of the VQ block with this project. Sequential gearboxes only add to this stress.

canadarob

iTrader: (1)

ouch, how much tq?

OldManZ350

iTrader: (23)

Sorry.......

Having an Billet Girdle is a MUST in a build like this.

How was the motor broken-in? Miles before Dyno?

Where did you get the Block?

Did you have it Magnifluxed?

Who installed the sleeves?

Who built the motor?

What were the Clearances?

Leforce

Thank you for the feedback guys, torque was around 678ft lb
The block was purchased used, it was not magnufluxed, break in period was very short I'm afraid. If you check the photos, the cracks are at the crank compartment, so sleeves & clearances has nothing to do with the issue. I spoke with a VQ35 specialist shop & they told me that such cracking is common at such power level & they offered me a billet block, I'm seriously considering it, it might be a once & for all solution.

rcdash

iTrader: (18)

I'm not an engine builder expert but most shops are biased to provide an answer that gets you to buy something for them.

I can tell you that most anecdotal reports of block failures are due to no billet girdle and sleeve installation issues.

I have never heard of a block cracking without (improperly installed) sleeves and with billet girdle. 700 ft lbs is no issue for an unsleeved block. If you want to go beyond that then sleeves might be worthwhile but very few have a proven track record (e.g. Dynosty). Even one of the Darton facilities have several failures under their belt.

Good luck

PS. A used, heat cycled block is preferred over a new block btw

LowPhats

iTrader: (1)

^This. A billet girdle really should be on the list.

Was Mazworx the shop that you spoke with? I have been following their new billet block production for the past couple months and have been considering it as well. You can answer me in a pm if you'd rather not say here.

It's always sad to see stories like this though, and I truly wish you all the best moving foward.

Cux350z

iTrader: (162)

Be sure to install a fluid damper crank pulley. Two main brands for the Z. ATI and some other one. While it may not solve your issue...it will be a good thing regardless.

OldManZ350

iTrader: (23)

Absolutly......

Italianjoe1

iTrader: (6)

Darton sleeves are probably the culprit here, as mentioned. Improper install is a major issue, as the shop has to remove a lot of structural material from the block to make room for the new sleeves, and if there is any excessive clearance that could allow flex or insufficient clearance that could allow the sleeve to cause pressure points in the surrounding casting when temperatures change, you can end up with a cracked block.

meatbag

iTrader: (9)

You might need to switch to a motor plate front and mid

Leforce

Please elaborate further

meatbag

iTrader: (9)

We did a couple drag cars awhile ago that would crack in almost the same place and it ended up coming from the fact we were still using factory motor mount plates with solid bushings, went to a front and mid plate and removed the factory mounts and never had the same problem again.

You can see the front plate in this picture on my car.

rcdash

iTrader: (18)

^ fascinating. Thanks for sharing. So the standard solid motor mounts are placing too much stress on the block. That's not good. I will have to look into it and wonder if just adding the front plate would be sufficient.

iideadeyeii

iTrader: (6)

^^ First time I've seen this. ^^
Glad to ACTUALLY learn something new on this site for a change.

meatbag

iTrader: (9)

Mazworx ran into the same problem on there s13 drag car I believe but i could be wrong.

Leforce

In my case the cracks had nothing to do with the engine mounts (check the images in the first post). But that's definitely something to consider for future builds. Meanwhile, I purchased another block & a billet girdle to get this car going.

rearranged

Might not be a bad idea as a preventative measure.

meatbag

iTrader: (9)

How do you know it had nothing to do with it? I saw your images. Did you read my post?

OldManZ350

iTrader: (23)

What he said.......

This Guy has a lot of knowledge and experience with the VQ. Don't be to quick to dismiss he's help as you did mine.

If you know what did not cause the block to crack, then you should be able to figure this out on your own and not need our help.