Just as the title says. Looking for a low CR with stock heads.

 

That would depend on the counterweights of the particular crank.

That question combined with the little bit of info you posted about what you are looking to do makes absolutely no sense whatsover.

The longer the stroke the harder time you will have keeping compression low with stock heads, and rod length does not affect compression.

Why don't you paint a boader picture of what you are trying to do?

 

Sorry for the lack of info. I have a set of pistons and a crank that I am wanting to build. The compression Height on the pistons is 1.120 and they have a 7cc dish. The crank is a 4.000 inch stroke internal balance. I want to use a 5.850 rod to keep the compression around 10:1. Is this possible or will the counterweight hit the skirt? I know it depends on my parts but I was hoping somebody had already done this and could tell me what they did. Thanks

 

as far as I know there is no way you can get a 4.000 stroke crank to fit in an LT1..... I know some have done 409 LT1's and I'm unsure of the bore and stroke combo but I know that a 3.875 crank and a .030 over (396 cubes) requires quite a bit of clearancing for the rod bolts. you're talking a full 1.25" more than that..... i don't think it can be done....

 

Anyone else have any comments on this? I would like to know if I can stuff a 4.000 inch crank in my lt1.

 

As Outlaw basically said, yes, but you're going to have to do a SHATLOAD of block machining. It probably won't be cheap. And I don't know, but you might want to use a Vette's 4bolt block, or machine in splayed caps for your 2bolt block.

 

A 4" stroke does fit. I think the biggest reason you don't often see it is that I am unaware of a 4" stroke 1-piece rear main crank. There are adapters so you can run a 2 piece rear main crank in a one piece main block so it can and IS done just not often. 3.75/3.875 1-piece rear main cranks are easy to find LOTS of options.

 

I have a 1 piece seal 4.000 stroke. Its just not the best brand. its a CAT brand. It says its good to 1000 hp so I figure I could put 400 to it.

 

You'll almost certainly want to use the 2 bolt block (more meat) and have it machined for splayed caps to get the clamping force... and even then, you'll have so much EXPENSIVE clearancing to do, you'll need to X-ray the block to be sure you'll have meat left...

I think it'll be a cool, very expensive, and prone to early death approach.

 

The clearancing will depend on the actual parts selected but what I hear from a guy who has done several is that with the quality parts he uses the clearancing is not that bad and longevity is not an issue.

Far the 2 bolt mains comment there is only one LT1 block casting 2 or 4-bolt mains was just final machining.

 

Here's an LT1 clearanced for a 4" stroke using Compstar 6" rods.

 

I am definetely(SP?) going to go with splayed caps. Anybody recommend a certain brand? Thanks for the pics of the clearancing. What do you guys think of the CAT crank? I was actually looking into the compstar rods. What kind of power can you put to them and how much were they? I also have a set of Scat Capscrew 4340s. Might use those. Thanks for the input

 

The Compstar stuff is Callies "budget" line, think they are like $700 rods and all the reports I have heard is they are quite reasonably priced for their strength, the Scat rods will probably take more than that CAT crank if the rods will fit. I would worry about the crappy CAT crank taking out the Compstar rods because is certainly would be the weaker of the two.

I briefly owned a set of CAT 1.65 rockers they looked like garbage and CAT is such a bad company they did not care when I onformed them the rockers measured 1.6 ratio instead of 1.65. A company that doesn't care about something like that is in the buisiness of making crap to take money from people which is different from making performance parts. I know of a couple other guys that had those rockers actually fail.
It might last for you but I wouldn't spend too much putting things together for fear of losing the entire investment when one cheap part lets loose.

 

I have been wanting to make a cool post for my mailbox. I think thats what I will do with the cat crank. Is the compstar stuff good to 500-600 HP? or could I get the Eagle H Beams or Use my scats? Now Ill have to get a seal adapter cause Cat is the only one that makes the 4.000 1 piece crank. Ive got a set of pistons. I am thinking of going with 5.850 rods so the compreesion will be around 8.5-9 so I can put my Novi2K on it.

 

I would say Compstar rods are the least of your worries.

 

With 1.12 CH pistons, a 4 inch strole and a 5.85 rod, with the block decked to 9.000, pistons will still be .030 in the hole. NOT a good idea.

Here's another vote for NOT doing this engine as you are suggesting.

 

Then what can I do to keep the compression down with stock heads? Get a new set of dished pistons with a 5.7 rod?

 

.030" in the hole will be the compression killer. But earlier you said you wanted to 10:1???

 

I am looking for any CR between 9-10:1. I just need to know how to get there with a 4.000 stroke and keep the stock heads.

 

http://www.torinocobra.com/Randys_tools.htm

Use this link to play with your CR. Seems like you know most of your variables.