2000LS1

I don't know if this has been posted here or not but I found this interesting quote in the depths of the internet:
"We designed the competition engine using as many production parts and processes as possible," said GM Racing engine specialist Ron Sperry. "In order to reach our performance targets, we had to modify the block design. GM Powertrain engineers had some prototype block configurations they were studying for future products, and they made some of these available to us for the C5-R engine development program." -Ron Sperry http://www.c5rmotorsports.com/engine.htm


[Modified by 2000LS1, 9:38 PM 7/6/2003]


[Modified by 2000LS1, 12:46 AM 7/7/2003]


[Modified by 2000LS1, 12:46 AM 7/7/2003]

Scissors

You mean the LS2/LS7?

2000LS1

Yes, sorry don't know what I was thinking. Could a mod please fix the title for me?

*EDIT* "LS2/LS7"


[Modified by 2000LS1, 9:39 PM 7/6/2003]

SWCDuke

The key to increasing the bore is siamizing the cylinders, but this has often proved problematic in the past. The Vega block was siamized and the siamized bores were implicated as one of the issues with the cylinder wall scoring problems. Beginning in '75 the dies were modified to create a slot between the cylinders about a half inch deep from the top of the deck, and this got some coolant all around the tops of the cylinders, which is where most of the heat is. Being as how it was die cast with a open deck, it wasn't difficult to implement. A sand cast block with internal coring is a different story. Maybe some of you remember the original 400 SB from about 1970. It too was siamized and wasn't considered a good building block for a high output engine.

Notwithstanding the above, the current C5-R block is obviously not suffering from any bad effects due to siamizing, so whatever engineering tricks they are using should bode well for a larger bore production block as long as the tricks are amenable to volume production.

Duke

need-for-speed

:yesnod:
I had always heard the same thing about the 400 SBC. I also heard they were prone to overheating due to the siamesed cylinders. I posted a question on a couple of Camaro boards because I was considering building one for my '67 Camaro. All of the guys w/ 400's said they had no issues w/ overheating. Same thing for the 502's. Here's to hoping for a large displacement LSx engine. :cheers:

I Bin Therbefor

Other portions of the article cover several interesting points.

"The key components of the C5-R racing engine are a heavy-duty siamesed-bore cylinder block. . .

The chief difference between the production and racing blocks is the cylinder bore diameter. The production LS1’s dry cast-iron cylinder liners are fully water-jacketed with coolant passages between adjacent cylinders to enhance cooling. The racing version has siamesed cylinders without water passages between adjacent bores. This modification allows engine builders to increase the bore diameter from the production 3.90-inch dimension up to a maximum of 4.160-inch diameter for racing."

Note "siamiesed cylinders without water passgaes between adjacent bores".
:cool:


[Modified by I Bin Therbefor, 12:43 AM 7/7/2003]

Scissors

Now the big question is, how does that configuration stand up for a home user putting 200,000 miles on the car without a personal pit crew?

Rocketblock

[QUOTE]I"We designed the competition engine using as many production parts and processes as possible," said GM Racing engine specialist Ron Sperry. "In order to reach our performance targets, we had to modify the block design. GM Powertrain engineers had some prototype block configurations they were studying for future products, and they made some of these available to us for the C5-R engine development program." -Ron Sperry http://www.c5rmotorsports.com/engine.htm [QUOTE]

This also might have been a nifty way of using exotic parts and configurations they needed for racing but want to call "stock". Some may never see their way into street engines. :)

GDP

I'm sure that GM will have tested it. :yesnod:

SWCDuke

If a siamized block can put out 600 HP and run LeMans, I don't see any problem with 200+K of normal street driving and an occasional track session. I can't remember when the C5-R suffered an engine failure. I remember one was using a lot of oil at Daytona, but that was at least three years ago. Those things are about as reliable a race car as was ever built, and I have no doubt GM has learned a lot and the lessons are in the C6.

In the past some GM execs have said you don't learn anything from racing. Hogwash!!! GM has been learning from racing ever since Zora put his cam in a Corvette and ran 150 MPH on Daytona beach in 1955.

Duke

Scissors

I agree, but race engines go through a lot fewer heat cycles than personal engines. The problems facing an engine with a lot of heat cycles are different (in some ways) than the problems facing a race engine.

LongTimer

I still learn something everyday here. The chart at the bottom of the article indicated that the 7 liter C5R engine has Cast Iron Sleeves!!? I thought I had read on the site that the C5R was sleeveless. Interesting.

I would have expected that the race team would have a sleeveless engine before production gets one. Does this mean that there will NOT be a sleeveless LS2 or LS7?

SWCDuke

Good point to bring up. Themal cycles are a particular problem with engines that have dissimilar head/case materials, and I had head gaskets replaced on both my '72 Vega GT (Al case, Fe head) and '88 MBZ 190E 2.6 (Fe case, Al head) during the warranty periods, but the head gaskets on my SWC (Fe/Fe) and Cosworth Vega (Al/Al) never gave any problems.

The other thing to consider is that over the life of the average automobile engine (as documented by numerous studies) about 80 percent of wear occurs during cold start and warmup. Thus, it's best to avoid short trips, and go easy on the throttle and revs until the engine warms up.

You're worse off driving a mile and shuting off the engine than driving 10 miles or maybe even 100 miles.

Duke

bigblockbob

I agree it goes through fewer heating and cooling cycles. However a normal engine will never be put throughthe extreme torture of a twenty four hour endurance race. I think that the endurance race tests the siamise bores plenty... and as for the oil using thing at daytona. it was probably some screwed up rings. Just my .02 $ worth.

Curtis A. Franz

The old Chevy 400 small block had siamesed cylinders and the hot rodders learned to live with it. Those were the original 406 and 427 small blocks. The new C5-R has more room with a raised cam (versus the old block) to swing the long stroke cranks. :chevy