I have an '02 ZO6 with Magnusen SC, Lingenfelter tuning, headers, mini-tubbed rear wells and 345 drag radials, etc.
In the quest for morepower, I'm building up a new motor and have already bought a GM H.P. "C5R" block - the one with siamesed cylinders -- 4.125 inch bore -- which with 4 inch stroke gives a full 7 liters (427 cubic inches). I intend to build a normally aspirated 427 of about 525 - 570 RWHP.

Both my local speed shop, who has done very good work on everything I've had done to date, and a reputable engine builder which I intended to have build the engine, tell me they can build the engine to achieve that ormore power. However, they have advised me v e r y s t r o n g l y against building this as a 427 cubic inch engine, and suggest I go with a 3.75 inch stroke instead, for about 400 cubic inches. They say that everything they have heard is that 427s give problems due to a combination of: a) poor rod length to stroke ratio, and b) thecrank dipping into the oil in the wet sump (racing C5Rs were dry sump, the street version of the block is made for a stock LS1 type wet sump). This result is short cylinder wall/piston life (I can live with this) and flattened main and rod bearings "within maybe only a hundred hours" (I can't live with this).

On the other hand, Ed Potter at LPE, who has never steered me wrong, says the C5R block can make a good engine and a 4 inch stroke has caused LPE no real problems.

DOES ANYONE have lengthy experience with a 427, C5R or Darton sleeved, it shouldn't matter, that has some real mileage on it -- say 25k+ miles or 100+ passes through the 1/4 mile? How durable are these things? I'd willing take an engine that just wears fast because of the poor rod/stroke ratio -- and maybe needs a rebuild by the time it has 50K miles on it, even 40K -- as long as it will be reliable until then.

Stories and comments, anyone?

 

The local guys you are talking to do not know what they are talking about.

I am using a 4.125" stroker and not having any problems or burning any oil.

There are many people on here with 4.125" stroke not having any issues. Never have I heard of someone scared of the 4".

 

I don't have one, but I have heard that a 422/427 was pretty much the limit... over that and hte pison to rod angles get extreme. That said, LPE knows their stuff ( :nono: ) and won' steer you wrong. Also, MattG has tons of miles on his A.R.E. 436 c.i. super-stroker w/ no problems that I've heard of. PM him for some good info. I have heard that an all bore 396 (I think that's what it comes out to be) is the way to go for high power, high RPMs, and long life but I haven't researched it.


[Modified by Mean Green, 9:50 PM 4/12/2004]

 

Lets see, I know at least MattG, NeptuneBill, Buckmaster, Flyin' Brian on this board and many other people on other boards that are having no problems with the 4.125" stroke.

I think there is even a guy on the Southwest forum with a 4.25" stroke and no problems.




[Modified by kumar75150, 4:26 PM 4/12/2004]

 

I agree with KUMAR that your local yocals are not too well schooled in LS1/6 if they are telling you 4.00 strokes in a C5R block are unreliable. Do you think that MTI and LPE would guarantee these motors for 2 years 24K miles if there were issues? I say let your engine tuner stick with building old iron sbc 350s and go to MTI, LPE, CARTEK, ARE, etc. when it comes to hiring the best for building 427 LS1/6 cid superstrokers! :chevy :cheers:





[Modified by MTI 427 Roadster, 11:33 PM 4/12/2004]

 

No need for that, he's buying the block and all the internals, so even those engine builers can put the parts together.

 

:bs

 

4.250 and no problems with almost a year now. 434 CI.

Research it. Mine is extreem but I can live with a shorter than stock life. :reddevil

 

Lots of 4.00" stroke 383's around too! :yesnod:
Roy

What is the flattened main/rod bearing syndrome? :confused:

 

The C5R was built to be able to run a 4 inch stroke and last for 24 hour racing! The street is a LOT kinder.

 

40 1/4 passes, lots of street WOT & 5000 miles.

NO PROBLEMS :steering: :chevy

 

As to the main bearing flattening, I'm told the poor rod length/stroke ratio means the bearings take a real pounding and that they deform, or wear out of round, pretty quickly.

 

THE ENGINE IS ONLY AS GOOD AS THE ENGINE BUILDER THAT BUILDS IT.LISTEN TO THE PROS LIKE ED POTTER @ LPE.THIS ISNT THIER FIRST RODEO.IF I WAS BUILDING WHAT U ARE I WOULD CHOOSE LINGENGENFELTER PERFORMANCE ENGINEERING.LPE IS LEGENDARY AND THIER ENGINES ARE BULLIT PROOF. MY 2 CENTS .......LOL :chevy

 

Mine is only at a 4.010..........but it sure does like sustained 90+mph speeds so according to your local shops theory..........mine should have died long ago :D
A stated its all in the attention to details, choice of parts, matching up the drive train and building for an application in mind. Many of these vendors give 2 year 24K warranties on Strokers :eek: :yesnod: good luck!

 

Contact Chris at AP ENGINEERING for the real scoop on the c5r block..........

 

Stealth (Tek Warrior) is running a 441 now, what is that a 4.250"?

 

No, STealth is runnig a C5R block with the standard 4.125 bore and 4.125 stroke=perfectly squared 441cid motor. He also is the first C5 to run N/A into the 9s with his recent runs of 9.98 at over 136MPH through an automatic!!!! :cool: I would say this a winning combo!!!!! :cheers: ;)


[Modified by MTI 427 Roadster, 9:54 PM 4/13/2004]

 

dang, if you have that kind of money to waste on a corvette... why don't you do it right the first time. Get a good vendor like MTI for example. 500 ponies for 20k, with a 2k year warranty. Any vendor that warranties their work IMO is a sound deal. why risk having an old school engine builder kiss up more than 10k in expensive parts :(

if i had a 40k vette, + 20-30k you wasted on mods... I would have a porche GT2 by now ;)

 

First, I can see no reason to waste money on a Porsche. As my vette is now, with the Magnusen SC, etc. it will and has smoked even upgraded Turbos and GT2s in the 1/4 mile, and it handles as well. It also looks like a sports car, not a jelly bean.

And, I met with the engine builder and sorted out the problem. He thought I wanted an 8000 rpm rev limit and was advising the 1.56:1 rod/stroke ratio on the 427 wouldn't do it, and that I should back off to 3.62 (about 395 cubic inches) and it would do that and be a screamer. But I want the cubes, so I'll stick with 6,500 rpm and it will be solid.

As to his being an amateur, this is Nascar country and he builds winners, including engines that took two poles last yearsnf one that took Daytona several years ago. He's building my engine because he wanted to do a C5R, and I'm taking a chance, but he knows his stuff: he's building the engine with piston-centered rods, saving close to 100 grams per piston -- it will be the only C5R (or vette, I imagine) with them, and he showed me a few other tricks on the heads that strike me as impressive.

We'll dyno it at More Performance when its built and I will post results, good or bad. But the rev limit for long life will be 6,500, even with those super light pistons and rods.

 

If you are concerned with a 4.000" stroke slapping the oil, go with a dry sump. :yesnod: