Building 355 for 52cc LE2 Heads

[Casey96SS]

I am in the process of rebuilding the motor for my 96 SS. I plan to do a 355 with the stock crank. I have a good local machine shop that I trust and he will machine anything any way I want. I may or may not have him do the assembly.

Here is what I have to work with:
-Used block and crank. (Have not been rebuilt)
-Fresh LE2 heads with new Lunati 73925K5 dual springs. (Measured at 52cc)

Parts I plan to use:
-Scat 6" forged I beam rods
-Mahle forged pistons (or similar)
-Lunati cam from Lloyd in the 226/234 110 LSA range or slightly larger
-I have all the other odds and ends since the car was running last year in similar fashion but blew a head gasket and spun a cam bearing.
-Will be changing to a 3.90 gear. Car is an M6.

My budget is $3,000 to get everything back together including machine work. Machine shop told me $1,700 to do all the machine work and assemble the short block which I thought was fair.

The problem I am having is getting a safe SCR with the 52cc heads. This will be a weekend cruiser and not a track car so I would like to stay in the 11.5:1 SCR range. I know you can run a larger cam to lower the DCR, but I would prefer to not push things to the limit to have to do this. Hoping to not sacrifice low end in order to bleed off compression.

I get the following SCR with a +5cc Mahle piston
12.28:1 with a .035” quench
12.1:1 with .040” quench
11.92:1 with .045" quench

Seems like an +8 to +10 cc piston would be great but I cannot seem to find anything in that range. The dish pistons jump up to +16cc which would drop SCR to 10.64:1 with .035" quench. Would I be giving up a lot of power running at 10.64:1? I am assuming I would not have to worry about detonation issues then?

Everything I have read about these motors pretty much says to run the tightest quench you can.

Anyone having any suggestions on putting this thing together with my 52cc heads? Thanks for any input!

[Nostang 96z]

I would shoot for a dynamic compression ratio of less than 8.2-1 to be safe on pump gas, keep the quench between .035 and .042 and you will be fine. Pick a piston that gets you right at 11.5-1 compression ratio and then pick your cam to get your DCR as close to 8.2-1 as possible to be safe on all kinds of pump 91-93.

Something like this would work great.

4.030 bore
3.48 stroke
4.125 head gasket
.035 compressed thickness
52cc combustion chamber
-8cc flat top pistons.
-.006 deck height

The above gets you right at 11.55-1 compression. Then pick the cam to get you 8.2-1 DCR compression. I know a GM 847 cam will get you there with 11.5-1 compression and runs fine on pump gas.