Max boost on stock bottom end

How much boost would be safe for a stock 7 bolt bottom end with a built head and good headgasket?

20 psi ? I saw some run on 25 psi

Obviously it's going to depend on your turbo, but from the knowledge I have gathered you should be able to max out anything below a 50 trim and not worry about the bottom end. I'm sure somebody will correct me if I'm wrong.

On a 7 bolt, I wouldnt push it past 350. However, I would (and probably will) push my stock 6 bolt bottom end to ~450.

i've seen some guy at the tracks boosting his at 23psi with 110 octane, he had the basic exhaust system, uicp, filter...very suprised that he ran mid 13s all day

I'd push a stock bottom end to ~400 without having to worry. 4g63's are strong ass motors, stock 6 bolts will hold over 500hp.

I don't know about power, I think the record is in the 550hp range.. I'd have to look on Dsmlink fourms, their was a thread about that about a month ago. I day dream most days about getting a dirrect port setup for my 2g. I would love to see If I could get up their in those kind of #'s. Thats about $2000 away for me for the basic supporting mods and parts.. Zex Dirrect port kik, Progressive digital meth controler, cams, clutch. Got the ARP's and Cometic.. Not a real sinario though.. Sigh...


6bolts are fucking stout. Their is a guy here in spokane who happens to be a huge theif, but had his engine and tranny build by Jake Montgumry in Nampa, ID. Who is running a baiscly stock 6bolt bottem end with a Gt42 with a race head and putting down some stitty # at 30psi. He's such a fag.. 6bolts are seriously proven stock blocks though. If I had one, I wouldn't even touch it unless the compression was bad. Just put a new front-case, oil pump and complete t-belt kit including pullies and shoot for the moon...

Jeff Harrington holds the 7bolt record

Hey all, I wanted to share my dyno results with you.
We got the MAF settings, so the car will at least idle.
I am VERY happy with the resluts.


551 FWHP
501 Torque
36PSI of boost

T4 60-1 compressor and T350 turbine with .70 AR comp and exhaust.
272 HKS cams
Lower and 2 sides honeycombs
Straight C-16
60lbs/min of airflow
Timing of only 12 degrees
Stock bottom end
Stock 2G intake
1G TB
950cc injectors
Hacked MAF
MBC

99 GST
10.70 at 135mph

Yikes! That guy has more nuts than me. I do know/know of several local guys that have been pounding 500+ from stock 6 bolt bottom ends for years. I dont want to push it though, I like it when the rods stay intact and straight :).

Hey man, even the smallest of motors can break rods. Power doesn't break shit, stupidity does!! (No in my case though :))

I know the hp rating but, I was told high boost causes alot of strain on the motor (duh). I told my friend I was planning on pushing about 24psi of boost or where ever my turbo reaches full efficiency at. He told me not to run over 20psi. This kid used to be a big dsmer so I trusted that he might know a little bit but from my understanding with a built head all I have to worry about is not hitting or going over the 400hp mark.

I have been waiting on somebody to catch that. I read your post about max boost and everybody was giving you hp rating. lol

Anyways... I have seen people safely run 24psi on a stock bottom end, so I would assume your safe to that point at least. I'm only gonna run 20psi on the streets with my monster even though I know it'll handle a lot more than that.

Look at it this way. If you run too much boost and mess something up, then it just gives you a good reason to rebuild it stronger. :wink:

True, but boost and HP are intertwined. You could run 20psi on a t-25 all day but if you slapped on a 60-1 and cranked it up to 20psi, I think something would fly through the hood on a stock bottom end. So I would say 20-25 psi because I doubt you're running a GT35r. What turbo are you planning on running?

I will still be running the current turbo that is on my car. It has similiar flow charts as a big 16 I believe. We never really identified it. I have ran 24psi once and it pulled a hell of a lot harder and held fine but, that was just for one pull and before my new head/headgasket. I plan on logging the lb/min flow and stop turning up the boost when the flow stops increasing.

I did post the Boost. It said 36psi on his 60trim. Boost is a stupid way of looking at the question. It's not about boost, it's about airflow. Airflow=power. Their is a mechanical limit to the internals, and it is obviously close to 550hp. What ever "boost" it takes you to get this is upto the turbo you use.

So, I guess the real question is. At what point on what turbo will the mechanical effency of our 7bolt blocks fail?

Ahh, I missed that. You did post the boost scottsee. :thumbsup:

Alright. I was thinking there may be a point where the extra pressure from high boost would cause some problems. I guess I was right about my first thoughts of my only worries being staying at or below the 380hp at the crank. I doubt the turbo will be too efficient above 24psi but, as soon as the head is on and the project is done I'll be sure to post up my findings for everything.

i was under the impression that stock 7bolts could hold 500hp max... i am pushing for 400 on a OE 7bolt... :2cents:

im pushing 21 psi on the stock 7bolt block. i have one hell of a shitty tune goin on, but its quick and i havnt had any unusual problems. I'm blowing a few hoses here and there, mostly vaccuum hoses. my valve cover and whole head are still sealed well, no oil leaks. i think im somewhere in the neighborhood of 330hp though.

Well thats it... I'm decided. I'll just keep cranking the boost up untill I get near the 380-390 hp at the crank mark or the turbo runs out of power(efficiency). BTW springs, valves, retainers, locks, guides, and a bunch of other stuff came today... waiting on one more order and the brains for the new head will be going in... mwah hahahahahaha.

:thumbsup: