Elysian

What is the maximum safe bore on an LT1 block? I've seen 4.030, 4.060 . . . how big can I safely go?

dhdenney

iTrader: (53)

To my knowledge it's only .060" over.

BizZzatch350

iTrader: (33)

yep .060 is supose to be the max, .030 works fine to build a 396 or 383.

-PEPE-

iTrader: (10)

I'm curious now, if .030 includes 383-396 what does .060 consist of cubic inch wise? Didn't think you could go bigger than a 410ci or so on an LT1 due to thinning the cyl walls.

Nap

Excuse my ignorance but how are they putting out the 427 super cars, is that a different block?

MEAN LT1

iTrader: (2)

Usually they use the C5r block which has more"meat" to bore with and to stroke.

Vendetta

Or they use cylinder sleeves.

Keep in mind the 427s are LS1-styled motors, not LT1.

BizZzatch350

iTrader: (33)

Just depends on what size stroke crank you use, that and bore make the cid. Mark Montalvo has built some big inch LT1s but there is a ton of work that goes in to the block and rotating asembly, he built an LT1 in the 42x range using a 4.00 crank. You cant go to big on bore with an LT1 block with out turning it in toa door stop. Big cubes are all good and well but for a street/strip car your getting the most for your money out a 383 or 396. Going that big costs money. Joe Overton who is the fastes NA LT1 is at 388cid, his work is in the head and cam. Cubes are great but you have to have a head to match and take advantage of it. Your car is going to run man once you put some heads and a 12 bolt in it.

The Formula for CID is

Bore X Bore X Stroke X # Cylinders X .7854 = CID

-PEPE-

iTrader: (10)

hey thanks for the forumula and replies, learned something new today.

* 12-Bolt update: Bought my friends 12 bolt out of his 96Z28 3 weeks ago but been rained out last two weekends now. But!!! since I've had time to stare at the SOB I decided to tear it down and give it a once-thru (was bored). Well already the front seal was leaking so I knew I'd be resetting my gear lash and had to pop the cover, well in doing so found a bad carrier bearing & race and that was all I need for an excuse to replace the current 3:73s with 4:10s like my current 10 bolt has. But I also learned my axle has 33 spline Moser shafts, I knew he'd replaced the Eaton with an Auburn 700hp posi but was excited to see a 3-Series carrier (thicker gear set by roughly .230 thousandths) and Ford 9" style bearing hub assemblies (no C-clips), so when I install the 4:10 gears today I'm going to go ahead and put in extended studs for NHRA rules or whatever for slicks. Oh and it has ABS setup...not bad for 500 bucks and being 2 yrs old

now I'll need some 15x10 Prostars and 27" ET streets

hot_red_z28

For anyone who is confused about where his value of .7854 comes from like I was, the actual formula extended out is:

(Bore/2)^2 X PI (~3.1415926) X Stroke X # of Cylinders = CID

which equals:

(Bore X Bore)/4 X PI X Stroke X # of Cylinders = CID

which can be regrouped as:

(Bore X Bore) X (1/4) X PI X Stroke X # of Cylinders = CID

or:

(Bore X Bore) X (PI / 4) X Stroke X # of Cylinders = CID

The value of PI/4 is approximately .78539... and is simply shifted to the far right of the equation...

dhdenney

iTrader: (53)

I feel like I have to say something too. There's a cost benefit tradeoff to the bigger cube motors. They might make some more power but how much do you wanna pay? Like Bizzzatch350 said, there's a lot of work that goes into those things and it's expensive. 396 is cost effective, can do the deed and is still durable. For what you might pay for a 420 something CI LT1, you could do a 396 with a helluva power adder.

Fahad

What about 409ci LT1, need spec of 409ci?? did LT1 have another block, like LS1's (C5R)?? Why most people use 383 & 396?? i heard from many.. the 383 is better for street race and 396 is better for NOS and track what's your opinion's of that guys??

Thanks for advance..

dhdenney

iTrader: (53)

409 is just .030" over and a 4" crank. I think the main reason this setup isn't used much is due to clearancing for the larger crank. Probably not quite as durable. As far as 383's and 396's having duties in different realms, I don't think it matters. With a stroker, you'll just make more TQ the bigger you go, you can run bigger cams, and all that good stuff.

Vendetta

409s are far less durable. It's such a long stroke, and piston to oil pan clearance is zilch.

Elysian

What, exactly, has to be clearanced?

Vendetta

I didn't word it right, but what I meant was the piston at the bottom of it's stroke and how close it is to the oil pan.

Elysian

So is there anything else that would need to be clearanced to make a 409?

V8_DSM_V8again

http://www.geocities.com/MotorCity/7610/dyno.htm

409 Cubic Inches: LT1 motor

TPIS 409, from Hi-Tech Performance March 1997

350 LT1 block, .100 over

Callies 3.875" steel crank

Manley 4340 5.85" steel rods

Ross 11.2:1 pistons

Ported LT1 heads, 2.00/1.56" valves

TPIS Miniram intake, 58mm throttle body, 30lb/hr injectors

TPIS ZZ9 or 409 cam, both tested: 409- 225/225 @ .050, .525/.525 lift, 112deg sep; ZZ9-212/226 @ .050, .483/.520 lift, 112deg sep

dhdenney

iTrader: (53)

Now how'd they do that? I have never heard of that!

RacinLT1

had to be sleeved for .100 over,at .060 the walls are paper thin.

the reason 383 and 396 are so popular is because they are readily available parts. there is no "race" lt1 block,although there are rumors of a dozen or so "bowtie block LT1's" out there. GM scrapped that program when they swapped to the LS1.