LT1 POWR

I was looking through a Jegs magazine cause I was bored at work and I saw that they have lifter valley and main girdles and I was wondering when they would be needed? It says its for high rpm or high boost levels. It also says you will also gain hp by keeping the block from twisting and the cylinder bore from distorting. I was just wondering if this would be beneficial in keeping the block together with 15-20psi on a street car or if its more for a all out race motor? Anyone have an experience with these?

Also when are stud girdles needed? I am running crower aluminum 1.65 RR's and I'm not sure if I have 3/8 or 7/16" studs, but I plan on revving to around 6500 max, around 17psi and putting down about 650rwhp.

Steve in Seattle

The benefit of a large displacement engine, or a stock one on high boost, is that you don't need the high rpms smaller engines require for the same flow/hp.

If you're only turning 6500 I'd be suprised to hear anyone push shaft rockers or even a stud girdle on your build. 7/16" ARP studs are probably mandetory for any decent build, but to girdle them? Seems to be people on both sides of that issue. 8000+ and you'd be crazy to run without at LEAST a girdle.. but that's a whole different animal there.

If you find a block girdle for the LT1, let me know. Most 4-bolt caps are slanted at various degrees, although the vette 4-bolt caps are straight up. Any main girdle you find for the LT1 will likely need some machine work or at least some decent set up to get right. I have billet-splayed caps myself, but no girdle. Many engines over 650 survive without a block girdle, but I wouldn't say it's detrimental... just probably not nessesary at your/our levels.

But you may consider a partial rock block (just a few inches up the water jacket) to help support the mains. It'll help resist twist on the block side, and be a lot easier to do after getting the small block back from the machine shop... and you won't have issues with your oil pan selection/custom build like you would with a engine main girdle.

James Montigny

ARP Pro 7/16" studs will handle it just fine. They're nice and thick.
I see no reason for a girdle or shafties for that setup.

I've got a set (barely used) for sale if you're interested.
I had to swap them out for longer ones to accomodate my new head/longer valve setup.

LT1 POWR

I'm running a very similar setup to yours. I've got LE dart heads also. The pushrods I purchased with the heads and rockers are 7.800 long, but I haven't check them yet. Does that seem too long?

James Montigny

7.800" ?
I thought my 7.500" were long.
How long are your valves?

You'll need some very tall studs to handle the height of those rockers.
That, or you'll have to use shafties.

I went with 2.10" ... those will still be too short for your application.
I doubt you'd even get two threads in.

Steve in Seattle

Wow. Those Dart heads sure are tall.

For comparison, my 396 came out to a 7.000" pr with a 0-decked block, and "cleaned-up" LT1 head castings and new valves. And I thought being 0.2" under stock length was a lot.

LT1 POWR

It says its specifically for a LT1. I called them and it looks like it will fit splayed 4 bolts since the 2 outer bolts are at such an angle that they wouldn't interfere.

I don't know, just something to think about for high boost/hp motors.

Steve in Seattle

Ahh... cool.

1) Does it lock into the front and rear blocks as well? Or just the center 3?

2) Does it require machining the caps flat on top? (i.e. just longer studs/bolts)
or does it use stepped studs like our windage tray does (i.e. one nut to hold down the main cap, then a narrower thread/nut above that holds the girdle in place)?

3) Any word on oil pan limitations? WIll it fit a Canton or stock pan? (I imagine I'd have to remove the Canton crank scraper or the stock windage tray depending on set up.)

LT1 POWR

http://www.jegs.com/i/Horsepower+Sal...0-LT1/10002/-1

Here's a link.

Looks like it ties all of them together. Doesn't look like it would cause any clearance problems as it doesn't look very thick.

Injuneer

Just a single point of reference, but one that I know most of the details on. A buddy of mine had a shop build a 383 LT1 on a stock 4-bolt main block, running 20+ psi of boost off a Vortech S/C. Before the shop built the engine, they did some measuring on the block, and found that it shared a lot of the reinforcement features of the Gen 1 "Bowtie" block. Based on that, they built an 1,125HP LT1, with no main girdle and no block fill. Engine routinely ran to 8,000rpm. After running the engine at the track for more than a year, and pushing the 3,900# 30th SS convertible to 9.04@156mph, they removed the engine and stripped it down (they were upping it to 1,350HP, using a Dart Iron Eagle Gen 1 block). The LT1 block was in excellent condition, and was sold to a guy building an 1,100HP nitrous motor.

LT1 POWR

So was that a LT4 block then, or was it a 2 bolt converted to a 4 bolt. Is there any difference in the block between the 2 bolts and the 4 bolts. I know the LT1 is a strong motor, but some reinforcement couldn't hurt, especially when its a street motor that I don't plan on taking apart and rebuilding an time soon.

Injuneer

There is no such thing as an "LT4 block". All of the ....327 castings are identical for the 2-bolt and 4-bolt blocks. They used the 4-bolt blocks in all Corvettes, and for all "replacement" motors on all "body" lines. 2-bolt configuration was used in all other applications. It has straight bolts, not splayed bolts, and the measurements seemed to indicate that the meat was put in the block knowing that they would be using the straight 4-bolt configuration. To get a factory 4-bolt block from GM in 1997 (when he originally started his buildup), all you had to do was order it. He used the same block for 3 years, building it up to 750HP, then to 950HP and then to 1,125HP. It saw a lot of track time. At one point, and for 2 years after he retired it, the car was the quickest known LT1. Check the "Fastest" thread on the Drag Racing forum. Look for "George Baxter".

jakesz28

When my motor was built I asked about filling the block and the shop said it wasn't needed. When I talked to the next shop about freshing it to make sure it was ready to get pushed a little harder, I asked about filling it again. This was the second time I was told it wasn't needed. Low nines are easy with this combo and I hope to get more out of it.

Ive considered asking a bout the valley girdle but at that put it may be time for a taller deck and larger bore.

Stephen 87 IROC

I run a girdle on my rocker studs mainly because I can't afford a set of Jesels and because my triple springs are around 800 pounds open pressure.

As for the lifter valley girdle, how many GM blocks have you seen split in 2? My guess is very few to none. Ford 302 blocks is another story. They can be split very easily and require the girdle.