[Blown06]

Seems like you could run a shelf piston with a 4.250" arm and a 6.000" rod.

Would it clear the cam? What other issues might it have?

Just wondering how this would run. Would make 427" out of a stock iron block with a 4.030" bore.

 

[racer7088]

Lot's of issues with one being cylinders are too short to adequately guide the piston at TDC and you would have to have a custom crank made as well as 6.000 rods wouldn't clear. 99% of LS cranks which are cam-cut for 6.125 long rods. Rods may or may not hit cam at 4.250 stroke depending on many factors. pistons might hit main webbing at BDC too depending on piston shape and skirt profiling and design. Crank might not balance without a lot more heavy metal as well.

 

[Blown06]

Lot's of issues with one being cylinders are too short to adequately guide the piston at TDC and you would have to have a custom crank made as well as 6.000 rods wouldn't clear. 99% of LS cranks which are cam-cut for 6.125 long rods. Rods may or may not hit cam at 4.250 stroke depending on many factors. pistons might hit main webbing at BDC too depending on piston shape and skirt profiling and design. Crank might not balance without a lot more heavy metal as well.

Pistons hitting anything should not be an issue as they aren't coming out of the bottom of the sleeve any more than a 4.000"/6.125" combo.

What do you mean about the cylinders being too short to guide the piston at tdc?

Obviously the crank and rods would not necessarily be shelf items. But what do you mean by needing a custom crank as the 6.000" rods wouldn't clear? Wouldn't clear what?

Rod ratio is doesn't seem that far out of control at 1.41.

Looking for input for a motor that would be mainly drag raced with the occasional cruise night. Probably less than 4000 miles a year. Not scared to freshen up once a year. It would more than likely also be encouraged by miller lite and a procharger.

Just looking for something a little different than your run of the mill cookie cutter combos.

 

[Blown06]

I need to edit my first comment. Pistons hitting the webbing of the block should not be an issue. I wonder if pistons hitting the counter weight would be an issue though??? No reluctor on the crankshaft to worry about.

 

[racer7088]

you need the counter weights to be the right height which is determined by the rod length so the crank company needs to know you're going to run a 6 inch rod or the pin boss will hit the counter weight.

 

[blackonblacksls]

you need the counter weights to be the right height which is determined by the rod length so the crank company needs to know you're going to run a 6 inch rod or the pin boss will hit the counter weight.

You have built some stuff similar to this haven't you?

 

[E.R. Racing]

Don't have a 4.25" crank, but our lunati pro series 4.185" crank clears a 6" rod.

 

[racer7088]

You have built some stuff similar to this haven't you?

Oh yeah. but 6.0 block only has a 5.450 long sleeve or so so that's not a really good idea in that block.

With an average ring stack of .700 you only have a half inch of piston skirt in the bore down there. not many skirt profiles like that to say the least.

Internet is very very spotty at my shop right now and still no regular phone so it's hard to even get on here most of the time.

 

[fastrobroy7]

Oh yeah. but 6.0 block only has a 5.450 long sleeve or so so that's not a really good idea in that block.

With an average ring stack of .700 you only have a half inch of piston skirt in the bore down there. not many skirt profiles like that to say the least.

Internet is very very spotty at my shop right now and still no regular phone so it's hard to even get on here most of the time.

FOR SURE he has, he built my motor!! Five years later, god knows how many passes. Erik knows his stuff, issue i had was going for 30# on stock heads, motor didn't get hurt just FINALLY made the head gasket disappear

 

[fastrobroy7]

And I was curious, why don't you half fill the block, 1/2" head studs and take the bore out to 4.070 and use a 4.100 stroke? Then have Erik or Kurt pin the mains and get some prc 247's if you want cathedral or prc 260's if you want square port.

 

[blackonblacksls]

I was speaking specifically about the long stroke stock block stuff. I thought I rember some weird displacement stock block stuff he had built. That had a lot of stroke

 

[LosLS2]

I don't even like the 4.00 stroke on a stock block for something resembling a daily driver. Fine for a race car or weekend warrior.

 

[fastrobroy7]

He put the 3.9 stroke in my iron block with a 4.020 bore

 

[blackonblacksls]

He put the 3.9 stroke in my iron block with a 4.020 bore

Yeah they are talking about 4.25

 

[LosLS2]

3.9 is a good stroke for a stock block.

 

[PuRpS]

i refuse to do anything more then 4" with a stock block


just not worth the head ache in my opinions

 

[My6speedz]

Does Compstar make a 3.9 crank?

 

[PuRpS]

Does Compstar make a 3.9 crank?

i think they may have stopped making them ???

 

[racer7088]

I was speaking specifically about the long stroke stock block stuff. I thought I rember some weird displacement stock block stuff he had built. That had a lot of stroke

We did some drag race only that had 2 ring pistons that were NA and they ran vacuum pumps. It was an .043 top and 2mm oil rail. I think it was only .920 comp. ht.

 

[fastrobroy7]

i think they may have stopped making them ???

I'm pretty sure Callies and K1 still are making them right now