Looking to build my first LS engine and swap it in place of my 505ci BBC in my First Gen using an LQ4 as the base block. I keep reading of the woes of using a 4.0 stroke with the bdc issues of piston scuffage, premature wear, and oil consumption. In that I want a long wearing engine I turned to the 3.9 stroke which the LS novice in me assumes should be more desirable for rod angularity, thrust loads and the skirt problem from the cylinder bores being 2 short...SOOO by my calculations I need a piston with a compression height of 1.165 2 valve reliefs and 4.030 diameter to work with a 6.125 rod and 3.90 crank...NO PROBLEM IF YOU RUN A FORD...I cant find a piston with Chevy valve reliefs in this configuration. What am I overlooking?
Also I find it odd that if 4.0 strokes in 6.0 blocks pump oil and have longevity issues why do all the mainstream vendors jump straight from 3.622 to 4 inch stroke in their lineups with 3.75, 3.875 ( from my conventional SBC days), 3.9 variants curiously missing?
The way I have it arranged in my mind based soley on data gathered so far is 4.125 stroke doable for short term max effort race, 4.100 much more desirable for race application with less potential for premature wear, 4.00 durable as a race stroke in the LQ4 block but wont experience anything remotely approaching the legendary LS durability when used as a street or DD engine which brings me to 3.9. Educate me on how hopefully my assumptions are wrong.
one more question and I know this is silly to yall, but what is the difference between conventional 6.125 2.10 SBC rods and "LS 6.125" rods? Is there a big end or edge fillet difference or are they in reality the same rod?

Thanks
Shawn

 

Interested in the responses to this thread. I too have had the same question in mind. Maybe we can have some vendors chime in!

Subscribed!

 

Nothing out of the ordinary. It's because most vendors and others jump right to the 4 inch stroke is why you can't find shelf pistons. But...not a problem. Pick your pistons, in bore, dish/dome etc and call the manufacturer and have them set a custom compression height. Last set I bought from diamond cost me 50 bucks extra over the price of the set of 8 for a custom compression depth.

 

The small end of the ls rod is offset slightly. You make a small block rod work, but I bet it would end up costing more than just buying ls rods

 

Thanks for the reply would never have thought it would be that little a premium for custom pistons. That's what ill do call em up and see do you remember how long it took em?

Thanks for the info on the rods too

 

Not too long. I suggest calling a few different places. Call up hke. They are a direct dealer with wiseco.

 

I'm in the same boat you are, using an 4.040 block with a K1 3.900 crank and 6.125 rods, had to order custom pistons. Not a lot of extra money at all.

 

Sometimes you can tweak the deck and use a shelf piston. I'm building a 370 with a piston for 6.125 rods. with a 6.100 rod. I have a 9.2155 deck on my 6.0 iron block.

 

Can you turn me on to who you called? How long it took? and how pleased you are?

Shawn

 

AES, a sponsor here, does 390cid engines with a 3.80 stroke in 6L blocks. You might be able to get the rotating assembly from them (which is Callies Dragonslayer crank and Compstar rods w/Diamond pistons).

They do the 390 for high boost applications.

 

I did find ONE off the Shelf piston for this application. Its a Probe 8.5 cc dish however if I zero deck and mill my L92s say .025 using a .040 MLS gasket i should end up with 10.7-10.8 ( depending on the combustion space of the gasket ) that would be right in the range im looking for ( would prefer a tad more but oh well ).


http://www.cnc-motorsports.com/pisto...-125-rods.html

 

Back from the dead...

Is there a meaningful difference in the longevity of a 3.90 stroker vs a 4.0 stroker?
Thinking about a torque-oriented build, slowly trying to get my bearings and work out a plan.

 

Well engine builders say the shorter stroke motors live a longer life due to them keeping the bore further up into the cylinder wall and are able to rev a little bit higher than a motor using a big stroker crank. Plus the shorter stroke motor eould hsvd better control of oil control. I believe that myself..... it's a member on here that built a 333 ci motor using a 4.8 factory crank and putting it into a 6.0 block with LS3 heads. That motor spins 8000 rpm!!! Not the normal LS stroker build for sure! Matter of fact that motor would be called a destroker.

 

old *** thread but the Arias 1010510 piston is 4.030" bore with a 1.065" compression height.....when run with a .927" wrist pin GEN I style rod at 6.200" length can work with a slightly decked block.

 

the newer series LS engines are dead on they DONT have offset like the older sb, bb Chevy

Building The Chevy LS Engine...
Chevy engine featured an offset connecting rod, the
LS series features on-center connecting rods (pin
bore in relation to big end bore). Do not use offset
connecting rods in any Gen III engine!

Enginebuildermag.com
On most rods (except Chevy “LS” engines), the pin bores are offset slightly.

LS Engine insight
While the “standard” small block/big block Chevy engine featured an offset connecting rod, the LS series features on-center connecting rods (pin bore in relation to big end bore). Do not use offset connecting rods in any Gen III

 

What other benefit do you get with the 4.8 stroke = high RPM?
Really expensive rocker arms...

 

It used to be done pretty regularly when there weren't a lot of LS rod choices out there. It works fine, but there are enough LS rods now that it's not really an issue.

FYI, did you see how long ago he posted that? I'm not even sure he posts here anymore...