chuntington101

so whats the most someone has pushed out of an ally block???

just trying to find the upper limits of the block, then you can detune to a safer level!

thanks Chris.

HIGHRPM

I have a 427 C5R, F1-R making over 800rwhp with about 14.5 lbs (195kpa) boost. So far its been totally reliable. The low end power is so great that I rarely have to push the motor to 6000rpm. I handle most street encounters in the 3000-5500rpm range....more than power enough to take care of business..... not having to repeatedly push to motor to redline does give some measure of added reliability. The cost of a C5R 427 is high...probably not warranted for most street driven cars.

Earl H

Once again, are we talking hp or boost.

What about a stock stroke C5R vs. a LS2 block re: reliability at the 800+rwhp level-used regualarly? I see a lot of guys saying that the iron block is better for strength. That implies that alluminum isn't strong enough to handle the power. Is this the case? What are the high hp/hi boost import motors doing (i.e. Supra, WRX,etc.). Are they refreshing every other race or year as well?

YELLOHHH

My .02, it's all in the tune.

Earl H

Sometimes its better to sit silently and let people think (well you know the rest)...

ForceFedC5

I am NO mechanical engineer, but this is my take on it.

An aluminum block will flex or break before an iron block.

If you run the aluminum block at high hp levels (the question is how high?) the block will flex and distort. After a certain amount of time this will either wear the internals or block enough to cause some type of failure.

An iron block will also flex and distort, but the pressure levels are much higher.

Of course, the way the block is made also affects the life span. I'm sure there is a very good reason why Lingenfelter only offers C5R race blocks on their high hp twin turbo's.

Questions:

What are acceptable power levels for the stock bore/stroke LS6 and LS2 blocks?

What are acceptable power levels for a stock bore/stroked LS6 and LS2 (382 and 402, respectively)

What are acceptable power levels for an iron block?

Also, can someone fill me in on the iron blocks? Do they have a cast or forged crank? Are they stock displacement of 408 CI?

To define acceptable, I'm talking about JB type of abuse. Long blasts in and out of boost (and interviewing Hot Torco girls! )

JB's been abusing his 346 for YEARS and it seems to be fine. I do not know of a 382/402/427 that has taken that kind of abuse and still functions as well.

DOUG @ ECS

I know of a ton of them?? mine, J.J's,Billy182's 427, just to start.

Mopar Jimmy

The GM ironblock that is being discussed is 6 liters and uses the same type of cast crank as a LS1 motor and i am pretty sure its the exact same crank. This is the 6 liter ironblock that is used in many GM trucks that were built during the same time frame that the LS1/6 motor powered the C5.

The stock displacement of the ironblock if pulled from a SILVERARDO, etc, is 6 liters which is the same cubes as a stock cid LS2 motor. In order to achieve the very popular (especially with the go fast f-body aftermarket crowd) and battle tested 408 STROKER cubic inches one has to utilize an aftermarket forged 4 inch stroker LS1/6 crank and bore the ironblock out .030 and use aftermarket forged pistons which are off the shelf (as this is a very common overbore for ironblocks) in order to accomadate the larger bore size of the ironblock (bored .030).

Most of all of the components on a stock cid LS1 motor are interchangeable with the LS1 motor.

ForceFedC5

And they beat the snot out of their car on a regular basis like JB?

Wait till I get my car.. we gotta hang!

chuntington101

so are you guys saying its just the flexing of the block that causes the faliures or is it the material around the liners???

sooo if that is the casue of the problem, then you would imagine solid mounting the block would make it beable to handle more power???

i guess what im getting at is what actually goes on the ally block that doesn't on the iron????

thanks Chris.

ForceFedC5

Those guys are not saying it.. I did. and I'm not an engineer.

(and I DIDN'T sleep at a Holiday Inn Express, either) :o

DOUG @ ECS

Sure do, I think you need to come to the Glen with us.

LinearX

Since big cubes and boost don't seem to have the same longevity as a stock cubed motor, what about something in between like a 370/383 engine?

#001 2001 Z06

You, however, know what you are doing and that matters more than a lot. It's all in the build, tune, cooling and fuel.

I would say just because someone has the parts, it does not mean they can or will put them together correctly. There are a number small and big cube motors out there, that run just fine and a number of them that do not. Also, some have been replaced or rebuilt.

A reliable stroker under full or any boost is a lot of fun.

Mopar Jimmy

Many people seem to have good success with a 383 stroker motor for F/I!!!

0Slowhawk

I know a ton too,but I know alot more that tried pushing the extra power and went boom

Now,if we talk race type cars,then I can show people alot of 7-8 second cars but that is alot different than street cars

0Slowhawk

On another note. If I was building a Vette for myself it would be a 402 with decent heads and a mild Cam,then add a D1 at 12lbs,fuel system and an alky control kit. This would be a 100% daily driver that can run 9's at the track.

Too bad I'm just building a 99% track car though for a project

ForceFedC5

What combo would you use if you were partially insane and wanted the potential for 850+rwhp?

Long engine life, streetable are key

(I'm beginning to think stock stroke ls1/ls2, C5R (too much $$), or iron 408?)

0Slowhawk

408 iron ,Turbo.

and deep pockets:o

SurfnSun

I could be wrong but theoretically don't turbo motors love more bore and less stroke? Using something like a de-stroked C5R block bringing you to ~377ci should be the best for power and longevity. John Meanie that build the 1200 hp C4 talked about cylinder pressure being the killer of high hp motors. He stated he'd rather have something like 550lbft of torque at 6k rpm vs 800lbft at 4k. I will see if I can find the article.