Ls3 shortblock

[iamdub]

I already run 93 daily as that is what my truck was tuned on. My heads where the stage one porting from texas speed so I'm basing my numbers off there charts. And no boost. I'd love to break 400whp tho.

As far as I know stock dimensions other then 20 over and I'm going to buy a bridge and dial indicator and see if I can get exact measurements. I was basing it off of .007 out of the hole which came up a few times on fourms when looking up ls3 stuff. Also using .051 gasket for cr calculator.

You're doin good measuring things for yourself, especially with a modified block. .007" out of the hole is what's expected and averaged for a stock block, but you gotta know where YOUR particular engine is at, again, since it's modified. This is no area to just guess and hope you get lucky. Breaking 400WHP should be easy, but you're gonna need a cam, which makes knowing your PTV clearances even more important.

I like the idea of 243s on a 6.2 block in a truck. The 243s don't flow as much total volume as the rec port heads due to their smaller runners. But, the smaller runners mean increased low-RPM port velocity over the large runners of the LS3 head. This will increase low- and mid-range power while still not being a real "choke" in the upper RPM. This is ideal for a heavy SUV. The CNC porting will raise the power band of the heads a little and make them a little more like the stock LS3 heads for a bump in the top-end power. You'll also have the better intake-to-exhaust flow relationship of the 243s. Their smaller chamber (diameter included) will raise the CR a good bit compared to stock LS3 heads. "High" compression equals more power (torque included) across the board. All good stuff. Just gotta ensure it's good and will stay good by taking a few simple measurements.

TSP mills the heads to your specs as part of their Stage1 service. Did you buy them done or did you have them done? Have a spec sheet or know the chamber volume and/or how much they shaved?

 

[JDopirak]

You're doin good measuring things for yourself, especially with a modified block. .007" out of the hole is what's expected and averaged for a stock block, but you gotta know where YOUR particular engine is at, again, since it's modified. This is no area to just guess and hope you get lucky. Breaking 400WHP should be easy, but you're gonna need a cam, which makes knowing your PTV clearances even more important.

I like the idea of 243s on a 6.2 block in a truck. The 243s don't flow as much total volume as the rec port heads due to their smaller runners. But, the smaller runners mean increased low-RPM port velocity over the large runners of the LS3 head. This will increase low- and mid-range power while still not being a real "choke" in the upper RPM. This is ideal for a heavy SUV. The CNC porting will raise the power band of the heads a little and make them a little more like the stock LS3 heads for a bump in the top-end power. You'll also have the better intake-to-exhaust flow relationship of the 243s. Their smaller chamber (diameter included) will raise the CR a good bit compared to stock LS3 heads. "High" compression equals more power (torque included) across the board. All good stuff. Just gotta ensure it's good and will stay good by taking a few simple measurements.

TSP mills the heads to your specs as part of their Stage1 service. Did you buy them done or did you have them done? Have a spec sheet or know the chamber volume and/or how much they shaved?

I sent a set of 243 takes off heads in and they just milled them .005 I did not tell them to milled them to any specific measurements. No spec sheet just the one they have online for there stage one porting. I have contacted the place who has tuned my truck twice a few times today asking various questions and they have not been too helpful as in not answering all questions or giving advice which sucks because they have already tuned my truck twice I thought they would be more help.

I am curious if my current fuel pump and injectors will be fine I have a flex fuel truck I know they flow better then none flex fuel trucks. I contacted texas speed and they suggested this cam

• TSP L92 Truck Cam 216/228, .600/.600, 113 LSA (25-TSP216228-113)

I also called btr and they suggested there
BTR GEN III & IV TRUCK CAM - STAGE 2 - V1 - 31218132R1

212/218 .553/.553 113+2
I already have a 212/218 cam.

Complete street said my 212/218cam is really small for 6.2 and they want to do a one off custom cam.

So everyone has a different opinion on what cam to use.

Everyone however said 11 to 1 should be fine running on 93 but I unfortunately can only get 91 some times but as long as I dont beat on it it should be fine.

 

[kbuskill]

Contact Vinci hi-performance

@Rocket Man has had great customer service from Roger... even has his personal cell number.

 

[Tonyrodz]

I sent a set of 243 takes off heads in and they just milled them .005 I did not tell them to milled them to any specific measurements. No spec sheet just the one they have online for there stage one porting. I have contacted complete street performance a few times today asking various questions and they have not been too helpful as in not answering all questions or giving advice which sucks because they have already tuned my truck twice I thought they would be more help.

I am curious if my current fuel pump and injectors will be fine I have a flex fuel truck I know they flow better then none flex fuel trucks. I contacted texas speed and they suggested this cam

• TSP L92 Truck Cam 216/228, .600/.600, 113 LSA (25-TSP216228-113)

I also called btr and they suggested there
BTR GEN III & IV TRUCK CAM - STAGE 2 - V1 - 31218132R1

212/218 .553/.553 113+2
I already have a 212/218 cam.

Complete street said my 212/218cam is really small for 6.2 and they want to do a one off custom cam.

So everyone has a different opinion on what cam to use.

Everyone however said 11 to 1 should be fine running on 93 but I unfortunately can only get 91 some times but as long as I dont beat on it it should be fine.

View attachment 260503

What's the sense of having it and doing all that work if you can't beat on it??

 

[avalonandl]

You can try thicker head gaskets for lowering the CR.

 

[JDopirak]

What's the sense of having it and doing all that work if you can't beat on it??

Towing power mostly.

 

[Dantheman1540]

Don't touch the CR you will love the snappyness of the high comp. I'd call someone and have a cam custom specced the 212/218 would waste a lot of other good things that motor has to offer. I second the choice on Roger Vinci great customer service and very fast not to mention free cam specs.

I'm jealous that's gonna be a sweet motor for daily driving and towing.

 

[iamdub]

High compression = towing power.

To be more specific, 11:1 isn't all that high these days. You also need to keep in mind that this is your static compression ratio (SCR), derived from calculating the mechanical dimensions so it's really more of a "benchmark" number. What affects the engine's operation is the dynamic compression ratio (DCR). The airflow and air events in, through and out of the engine determine the DCR. Having a cam with lots of overlap (low/"tight" LSA) generally will result in not so high of a DCR since the intake and exhaust valves are open at the same time for more of the duration than with a high/wide LSA cam. I like an 8.5ish DCR. If you know of or find someone that can plug in all the numbers (like with Desktop Dyno), they can determine your DCRs with various cams. A good tuner will tweak the timing to optimize the engine for the 91 octane. Also, if you have the quench height as tight as you can safely get it, this will increase compression but also mitigate detonation and promote more thorough burning of the fuel mixture. This is where measuring your piston height really comes into play. Say you were aiming for a safe .038" quench height. Assuming the piston comes outta the hole .007", you need a .045" gasket (.045" - .007" = .038") Piston heights can vary a lot- .011" and .012" isn't uncommon. Say yours measured on the high end at .012". You'd just run a stock .051" gasket to net a .039" quench height. FWIW, I'm running a .045" gasket and my pistons came out around .010", for a .035" quench. With a (presumably) 200K-mile engine and spinning it to 6,000RPM, I'm probably taking a little risk here. But, with the lightly shaved heads (.020"), cam and tighter quench all creating a sizable bump in torque and fuel burn efficiency around 2,000 RPM, I'm getting 2-4 MPG better at highway cruising speeds than I did with AFM.

So, yeah, don't fear compression.

Also, as Dan said, that 212/218 wouldn't be much of anything on a 6.2. That's the cam I have in my 5.3 and I'd consider it the bare minimum. But, it's ideal since it's a "truck" cam, meaning it doesn't negatively affect low-end torque. For more cubes, you need more duration. Talk to Vinci and/or others to get their recommendations an see how they compare to that TSP L92 truck cam.