Boost on Stock Pistons

[gottadiesel]

I am sure this has been discussed, I have searched and heard differing opinions. I would appreciate some feedback from those who have done the typical external mods for longer term and have had success with stock internals. How many miles and how much boost.

My engine is being done from top to bottom, but replacing with stock internals where required - pistons and cams are being replaced at this point, some items are still being tested and inspected. But the machinist, who has done some 7MGTE, but not a specialty of his, suggested upgraded pistons for another $500 if I was going to go over stock boost, but from what I have read, that is not the 1st item needing upgraded, my understanding is that it was the cam gears that were the weakest link. But then I thought, am I guaranteed that the replacement pistons meet the same specs as the stock ones or was it just a concern from a machinist who is not real familiar with the capabilities of this motor?

I am not looking to use this car for screwing around (drifting, racing etc) it is my daily driver that once in a while like to have that additional power... like when some 16yr old with a civic tries showing off lol... You can see my basic plan in my signature for mods...

Anyway all opinions and experiences shared are appreciated.

 

[tekdeus]

Stock pistons are good for 400rwhp. I've been around that level for a couple of years on a stock JDM 7M.

 

[GrimJack]

The nice thing about forged pistons is the extra insurance... get a bat batch of fuel and detonate a bit? Stock pistons are DONE. Forged, however, should be fine.

That said, with decent tuning, stock pistons can last - DrJones ran a stock bottom end to 500 rwhp for a few years. I don't think it ever blew up on him. However, this was tuned by him, an excellent pro in the field, using an AEM standalone.

 

[gottadiesel]

Thanks Tekdeus - I was planning to hover around the 400 mark also, will only be using a piggyback fuel controller, am not an expert at it, only advantage is I am in the electronic control industry both design and database programming etc... but once I am at that point would like to perhaps find someone local that would be interested in assisting for a fee of some sort...

Anyway so let's say I go with the extra insurance there (which is a good point by GrimJack) then what else is good insurance, rods, cam gears, cams??? I guess the question is what I am looking at doing, do I just stick with a stock motor or do I have it built, I have a hard time doing it half a**ed if I am going to build it with all the insurances... But at the same time, I am already over-budget, so if I decide to have it built, it will sit a bit longer before I can drive it...

Hope my quandary makes sense, also one of my other questions is, if the machinist is buying stock pistons, are there differing levels of quality to worry about?

Thanks again.

 

[GrimJack]

Personally, I'd get your stock rods checked, but I would expect them to be fine. I'd buy ARP main and rod bolts. That's not much of an expense.

There is an article posted on http://www.7mpower.com by Will Neely about how to build a 7m for each power level, it's certainly worth a read.

 

[tekdeus]

I did forget to mention I'm running ARP head and connecting rod bolts, with a GReddy metal head gasket. Those are a good minimum for a stock engine. Looking at your mods in your signature, it looks like you're ready to run around 400hp. Just take it to a dyno and get your piggyback tuned by someone who knows, carefully as you up the boost. 15psi is a good safe standard for pump gas, which is around 350-375hp on a 57 trim turbo.

 

[Mr. Y]

Check dyno section for Sean's X-Man record. It was 753rwhp.

 

[gottadiesel]

Thanks for the advice, I will order the other ARP bolts along with the Head ones that I had planned. I read the article and yes some good validations as far as making sure the plan is good for the goal.

My plan was to build for the 400hp range, but then run it at the 350hp... I am all about safety factor...

So the only issue that I may or may not have, is that I am in rural WA, so there are no specialty machinist within 80miles, but everyone I spoke to recommended this shop and they have been great to work with, so I hope they do as good of a job as everyone says they do...

Thanks

 

[a_sesshoumaru]

i been running 19psi with stock pistons and rods of a MP T70 for 1 year already and is still strong, i think with meth they can hold 23psi with no problem at all. i think they take 500rwhp easy with meth.

 

[gottadiesel]

Thanks for the input, I had another discussion with machinist, this time his son who works with him and who I originally spoke to... I think the dad is an old school small/big block V8 guy. His son seems very familiar with the 7M and understands what it is capable of and the kind of tolerances needed... In fact when I asked about ra value for prepping for MHG, he said they surface to an ra value of about 13, so I figured he is not a sloppy machinist... But I am going to go with the ARP, head, main and rods, they also inspect rods thoroughly prior to re-using... he also recommended a line hone when changing to arp mains... I hope it is done soon, can't wait to get er back on the road... I am driving our backup car that usually does not go anywhere often... a beat up 97 cavalier that is girl baby blue... if driving that is not motivation to get it done, don't know what is...

 

[Kai]

Line hone...just for using ARP main studs? I've not heard that one before...

The less machining you have to do, the better. This isn't a Chevy small block.

 

[IJ.]

All in the tune, detonate it hard once and you'll break the ring lands in cast pistons.

 

[gaboonviper85]

Arp main studs/bolts are over kill and not needed unless you just want to say you have them....arp torque spec is much greater than stock meaning you'll have to line hone as more clamp force distorts the caps.

 

[IJ.]

Arp main studs/bolts are over kill and not needed unless you just want to say you have them....arp torque spec is much greater than stock meaning you'll have to line hone as more clamp force distorts the caps.

Pardon?

 

[gaboonviper85]

Pardon?

Pardon what

 

[IJ.]

more clamp force distorts the caps

Where did you pull that one from?

How much distortion have you measured Stock Vs ARP studs?

 

[gaboonviper85]

Where did you pull that one from?

3 point bore mic on my previous failed engine build showed .0007" give or take when over torque'd...I'm sure I could replicate it all over again on video if you like?

 

[gaboonviper85]

Didn't use arp honestly...just used stockers with more pressure.

 

[IJ.]

Define "over torqued"

NEVER had a tunnel issue using ARP's spec and Moly lube.

 

[gaboonviper85]

Define "over torqued"

NEVER had a tunnel issue using ARP's spec and Moly lube.

That could be my bad...I didn't use lube as I was just getting initial measurements for bearings.

I honestly forget the torque as it was about a year ago and I was just fucking around...wasn't really trying to produce data:-/