BlackHawk T/A

iTrader: (3)

GMPP claims the bay-to-bay breathing windows on the LS7 gained them 20-30hp over previous LS engines. They used them in the new LSX block also.

Is this for real? Page 31 in the Feb. GMHTP, but I'm sure its on the net too.

Quickin

Where's that 30-40 hp in the LS7, don't see it in that engine either.

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stevewix

wtf is a bay-to-bay breathing window?

96 Comp T/A

iTrader: (8)

I guess that means that the dry sump, 4" crank, titanium rods, bigger cam, titanium valves, 4 1/8" bore and GIGANTIC square port CNC'd heads were only worth another 65 hp? Give me a break. You want to buy a bridge?

67camaro

iTrader: (28)

LS6 Blocks also have them. LS1's dont.

BlackHawk T/A

iTrader: (3)

I find the claim a bit far-fetched. I wanted to see if anyone else knew about it.

Robin L

Yeah I wonder how they came up with that number. I am going to find out and I will let you know.

Based on conversations with people who have experiance I have heard in the area of 10 horsepower.

I would say that there would be a lot of factors such as stroke, RPM range that would effect the ultimate horsepower gain verses a block that doesn't have the windows.

Again when I find out the source I will post a update.

Thanks

Robin

MeentSS02

iTrader: (11)

I'm in the market for one...whatcha got?

Quickin

I think the fact that there are 427's out there for the past 6 years using LS1/LS6 blocks and LS1/LS6 heads and LS1/LS6 intakes that have more HP than the LS7 427, there AIN'T no damn way that this one thing creates 30-40 extra HP by itself. Common sense really. And there isn't 30-40 HP more anyway, it just isn't there. If it were true the LS7 427 would be laying down 530-540 RWHP.


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Robin L

As I said I talked to my contacts at GMPP. First I have not seen the article but I can say that it is true. Well the word I got was that is was "close to 30 Horsepower". That is from the guys who worked on the development of the LS7.

Bay to Bay breathing is something that I only learned about about 2 years ago. My Engine guy Jeff Steahly had talked about drilling the bulkheads in my 306 Ford Real Street engine. Jeff had been making this modification on many of his customers NHRA Super Stock engines with positive results. At the time it was very hush hush. He said that on the dyno they typicallly saw about 10 horsepower over previous baseline numbers. Remember this was on small block chevy engines. Small stroke engines.

On the LS7 you have a lot more volume of air that is being pumped as the pistons move up and down. Drilling a hole in the bulkhead was worth power.
Now as you can imagine this is not a modification for the timid. Better to buy a block with this done.

On the Ford engines there is an oil passage that is very close at the front bulkhead. It becomes a matter of how much do you want to remove before you risk the strength of the bulkhead. Us racers are used to taking things to the limit, finding the weak spot then backing off a little bit.
Most people are not in that type of situation.

Unless your engine builder knows the risks I would not recomend you making this modification.
It is another advantage of the LS7 block over a re sleeved LS2.

If you notice the new GMPP LSX Block has passages around the mains to promote Bay to Bay breathing.

So yes this story is true. 30 horsepower in a large bore stroke deal.


Have a great day!


Robin

Robin L

No, only LS7 and GMPP LSX blocks.

I don't know about the other aftermarket blocks.

Robin

mzoomora

iTrader: (36)

I laos remember reading that the LS6 had windows for better bay-to-bay breathing when they were released. I couldnt find any GM releases, but here are a couple things I found.
http://www.idavette.net/hib/ls6/page3.htm
http://www.dw1977.cz28.com/whats_new.html
I also remember big power claims then, in the area of 20 hp.

WECIV

Do C6 Z06's have these? Or is this a new thing for the LS7?

W

WECIV

Google LS6 Breathing Windows and you will find that the LS6 did have these things. Can anyone provide a diagram on how these things work? Thanks!!!

W

slt200mph

iTrader: (42)

I gotta run up the flag on that one... ... Yes the windows are the difference in the LS1 block and the LS6 block and I beleive those changes were incorporated into all the LS serise engines that came after that..LS2 ect. ect. I have major doubts that it would produce that much of a horse power gain..if so the LS6 cam and heads with light weight hollow stem valves were only good for 15 HP in the 405 HP version and even less in the 385 HP version..

Robin L

It looks like I need to got back and take a look.



Robin

mzoomora

iTrader: (36)

I can explain it, but I cant find a diagram. The thing is because the LS series engines are deep skirted with cross bolted mains the banks of the cyclinders go all the way down from one side to the other, unlike older small blocks where the caps were lower than the rest of the block. Older small blocks had fair breathing because the oil pan was deeper and all the pressure was distributed there. LSx oil pans fit tight to the block and can restrict the large volumes of air that the pistons displace on the down strokes, so they put windows in between each pair of pistons to let the air move around.



In the picture you can see where the crank mains are and that slit above it is the window (not the vertical one, I am pretty sure that is a water jacket).

96 Comp T/A

iTrader: (8)

Something else to consider is that with high crankcase vacuum found in most max effort engines with dry sumps and vacuum pumps this should even make less of a difference. I believe I saw somewhere that the NASCAR engine builders are now partitioning off the oil pans in an effort to decrease windage travel in the lower ends. These engines would have at least 1 dry sump pickup in each section though.

Keith

It is a big deal in repli-racer sportbikes. I can see it helping a lot in larger bore, large stroke engines too.