Stock Internals

[86TSiGuy]

To everyone out there who is or has run mods on the G54B stock bottom end; How much power and what mods are/were you running?

[boostandmuscle]

To everyone out there who is or has run mods on the G54B stock bottom end; How much power and what mods are/were you running?

*DM performance ran 367whp on a stock bottom end for 3 years i believe thats the right numbers.. could be off a few though

 

our stock bottom end is pretty damn bullet proof if the car is tuned right

Edited October 6, 2008 by boostandmuscle

[Technology]

Nobody has really ever pushed it to its limits honestly.

 

If you install ARP head studs, MPI and a big turbo, you might be the first to find out.

 

But 250 whp isn't too much for an all stock motor. Been done. Probably a lot more than that.

[TainterRacing]

I would say the Rpm has more to do with it then any thing keep it less then 6000 and it will do you good for some time.

[Caliber308]

Leaves me out

 

CALIBER 308

[Kellydahman]

I have pushed it to the limits. Numerous times.

And let's just say 350rwhp is safe for everyday driving on the stock bottom end with counter balance shafts.

[JustPaus_88TSi]

I have pushed it to the limits. Numerous times.

And let's just say 350rwhp is safe for everyday driving on the stock bottom end with counter balance shafts.

 

 

And what was the limit on that specific application? What failed and was it completely part related, or did fuel and/or ignition timing play a role?

 

 

350rwhp is vastly different when it comes to internal stress between a MPI setup or a TBI with big boost.

[mikec]

The old scuttlebutt said:

 

long block is good for several hundred HP if the fuel system is tuned properly. The stock crankshaft is a forged & nitride hardened part... about as strong as it gets. Lots of V8 guys go to Summit Racing or high-perf sales places to replace their factory crank with something forged & hardened... StarQuests START OFF with a good crank. Unless some previous owner schmuck (or cheating machine shop) replaced the factory crank with one from a Caravan, pickup, etc. that doesn't have the hardening.

 

Rods are darn durable too, especially if shot-peened. Years ago a 2.6 engine set up for drag racing use the stock rods and pounded out around 600HP for a full season on one set of stock rods, crank, and bearings.

 

The "weakest" link in the bottom end are the pistons themselves. The factory cast pistons don't survive long at mega-boost pressures, especially if the air:fuel mix is incorrect. The ring lands are the weakest part; they just crush when "things go wrong during the combustion." Hyper-eutectic pistons are a little stronger; forged pistons are a lot stronger in general. With a properly tuned MPI setup though, folks have been running in the 300HP neighborhood on healthy stock pistons for a while now. Getting high HP takes a lot of boost pressure if you stick with the throttle body - it's a narrow restriction AND the fuel distribution to each of the 4 cylinders is NOT consistent... so some cyls run rich and some run lean... the lean ones consume pistons. With a multiport conversion, a consistent fuel distribution is MUCH easier to achieve... and not as much turbo boost pressure is required to obtain the same horsepower so that's easier on the pistons too.

 

With a tuned MPI setup, I wouldn't be too afraid of 300 to 400 flywheel HP on a stock crank, bearings, and rods. Pistons?... don't know, haven't been there myself but I'd personally not risk it - I'd just get forged ones and think "better safe than sorry." Being cheap when trying to make 2 times the stock HP is a sure way to end up with a blown engine instead. Once you get to that HP level, the tranny and U-joints become the weak links. The differential is 600HP+ capable though. 88-later CVs and half-shafts are pretty stout too; the earlier ones are not quite as strong but as long as you don't have wheel hop from a worn suspension they'll take quite a bit more than stock HP too. Wheel hop will kill ANY halfshaft/CV/U-joint in short order.

 

mike c.

[Starwolf]

Just curious but i would figure the head would give out before the pistons. But you never really see that...or i guess we do see a lot of blown gaskets/cracked heads.

 

If your whole bottom end is forged what is the chances of the next thing breaking is a 700$ marnal head?

 

:thread20jacked8wq: *sorry lol

[mikec]

Depends "how" you get the high HP. If you're using high boost pressures, then the head bolts/studs can become the source of failures. The cyl head slowly deforms under the stresses of combustion pressures pushing UP while the bolts hold just a few points down - that tries to bend/flex the head into McDonald's arches. Skinny bolt heads & small washers concentrate the forces over a small spot... wider diameter washers spread the load out. Softer aluminum heads can actually compress (you'll see a washer-shaped divot form) under these loads. As this divot forms it's the same as having loose mounting bolts/studs - you loose clamping pressure on the head gasket and the head "lifts" off the block/gasket a little too. Now the gasket blows.

 

The head itself won't crumble to pieces. The only "weak" spots for the head are:

* the perches/towers where the head bolts/studs attach - the "divot" stuff. Thick/fat washers that cover the whole tower top are the best you can do.

* cracks from thermal issues (bad cooling system).

Aftermarket heads are made from various alloys; some are definately tougher than others. Some Marnals are good (there are other Marnals made elsewhere that use a softer material good for non-turbo engines only). The factory "T" castings are darn good.

 

For a high-HP motor, NOT using ARP head studs is silly. They cost the same as the factory bolts but are much stronger and have far better washers to help spread the loads out, reducing divot formation.

 

ARP fasteners in the bottom end are not necessary. Even ARP has stated the factory Mitsu fasteners are plenty good.

 

mike c.