Has anybody been able to put a 4.000" Stroke crank in an LT1 block? I am getting ready to sell the 383 to help pay legal fees and figure that when I recover I want to either try something 'new' or start with an LS1. I was thinking of a 4.000" stroke on a 5.7" rod and 12.0-12.5:1 CR. that is all I have thought of so far. Not sure what heads yet and when I decide on heads I will get a cam to try to match them. Right now I was just wondering about the crank Combo. If it will work, will the block need a little more than just some 'massaging', or will a Grinder take care of all the clearancing I would need?

 

Well you can get one in a SBC block, but the depth of the LT1 cylinders will make a 4.00" stroke a bit of work. It has been done, and you would have to get a setup to work to fit everything in the block.

The Eagle 435340006000 crank needs 6.00" rods and a 1" compression height piston to work. That also means that the counter weights are going to be hanging out there so it's going to be an even tighter fit.

As I have said before I don't think the $ per HP are worth it when you go from a 383 to 396 to 408 are worth it.

Bret

 

Actually, I considered a 6" rod at first. I thought that there may be a problem with the long rod and long stroke and the piston stalling for too long at the top and Bottom of the stroke.

 

or if you got to go big 3.85 stroke and sleeve the cylinders. that would allow for a lot larger piston. and you would still have you 400+ cubes.

 

One of the engine shops was selling an LT1 409ci short block... 4.00X4.030, but they no longer show it in their online catalog. Makes you wonder why.

A former member here claim to have built a 4.00x4.090 "421" and a 4.125x4.030 "421", so it has been done. There's also someone that posts here occasionally who claims to have a sleeved 4.00x4.120 LT1 "427".

Its just a matter of how much effort you want to invest in it for the unique ability to say "I have an LT1 4XX cubic inch engine."

 

I read effort as money.

 

Put the money in the heads and valvetrain rather than trying to go that big. You will get more bang for your buck.

Rich Krause

 

I just did not think that the cost would be 'too much' more for a larger stroke Forged crank over a Stock stroke Forged crank. I am pretty sure the price is near the same. I figured most of the added cost would be in clearancing or extra machine work.

 

And custom pistons, less choices when you go beyon 355 and 383

 

Hmmmm. I guess I was figuring that the pistons might be only 50-60 bucks more than a normal 3.850 stroke piston set.

 

I have a 4" stroke crank in my new motor (LT1). Easy when you use the right parts and costs no more than a 383/396.

 

...................well tell the folks at home more about it Johnny. Seriously.............im curious about this 4 inch stroke. How did you make it work jason. Thanks Prorac1

 

Use 383 pistons for 6" rods, but back off to a 5.85 rod... then get a 4" crank and some copper gastkets.

The slug will be 0.025" out of the hole, and some 0.065" gaskets will get you great quench.

Going 30-over, with the 4" crank you'll have a 408ci LT1, using off the shelf parts (assuming you have a 4" crank).

Clearancing will be a PITA, and you may even end up trying a few different sets of conrods...


The big question of course, is: what heads will you get to feed it?

I'm gonna have enough problems hoggin out LT1 castings to feed a 383 I'm building... fortunately I'm going with a small backup plan (Weisco pistons with reliefs to fit 23 AND 18* valves).

Power's in the heads... smart money's there to start.

 

there is the point, power is in the HEADS!

Nothing wrong with a 1.00" compression height piston really and it's much better than the piston sticking way up into the gasket. I'd rather have a really thin gasket and the piston in the hole.

Bret

 

I know of more than one LT1 block where clearancing for even a 383 (3.75" stroke) hit water. I think that if you didn't hit the water jacket when clearancing for a 4" stroke, no matter what rods you had, you were lucky. And even then, I think you would some pretty thin metal there. The Lunati Pro Mod rods seem to have good clearance. They are better in that respect than Eagle H-beam and Crower rods. The best rods I have seen for clearance are the Oliver billet I-beam rods. Most motors don't need these, which is good considering the price. But on my new motor I am using a set and they required very minimal clearancing. Almost none in some places.

In an NA motor the relatively high revs needed to make power will come into play when considering a long stroke motor. At 7,000rpm a 4" stroke and a 6" rod will produce a max piston speed of 4,648f/s and a max acceleration of 119,384f/s^2. With a 3.75" and 3.48" stroke and a 6" rods the numbers are 4,357 and 110,174 and 4,043 and 100,489 respectively. For a street motor these differences are significant.

I think a 4" stroke is too long. Jason, and other knowedgable people obviously don't think it's an issue. But if I wanted a 4" stroke small block I would use the lightest pistons and stongest rod bolts I could find. And definitely a 6" rod, though the difference in acceleration is small I think every bit may help.

Rich Krause