Got a stock gen 4 5.3 with a btr stage 2 truck cam 212/218. Got a great deal on 241 heads and I’m in the process of boosting this motor with a single turbo charger. I know it will drop scr but with flat tops and some gaskets what wouldn’t compression be and not hurt performance out of boost? I know 317 are too large. I want to keep it pump gas and 15-20# boost max. Gt45. Can I run these without losing drivability but also drop scr for my turbo?

 

And also does anyone know if it is ok to swap the gen 3 truck pan for the gen 4 to eliminate the oil bypass for the afm since I deleted the dod. I have the oil pressure drop issue with the o ring valley cover and heard it’s the oil pan that needs to be dealt with. Instead of take the bypass out I have an extra pan sitting in my garage off my lm7

 

On a L33 factory 5.3L with flat tops with 243 head your about 9.93:1 compression.

So if you ran the 241 there like a 66cc vs 64cc so it will only drop to about 9.7:1

If you went with an .040 head gasket you be back around 9.94:1

It's all relative and you would need to physically measure to verify true compression ratio. but this is a pretty close idea.

L33 Stock

L33 W/241

L33 With 241 and .040 head gasket

 

Ok so I won’t really lose much compression if any at all from my stock 5.3 with flat tops and 243 heads then? I just want want to drop under 9 for drivability but also be able to feed it boost without detonation or pinging

 

WARNING: CONJECTURE AND OPINION BELOW:

I think our cast pistons are the weak link, especially with tight OE rings. Before I put the time and expense into dropping compression, I would maximize what the motor can make on 12-14lbs. Some may (and will argue) this, but I strongly feel 12-14lbs is the limit for a SBE LS on pump.

I thibk if if you're gonna do anything, a boost friendly cam is better money spent

 

Sorry this is not a stock build. Stock heads and block and gen 4 rods and pistons but aftermarket cam and the supporting needs obviously. Not an all out build but a nice fresh engine that can take moderate boost levels

 

Still wouldn't go over 12lbs ish on pump gas

 

And that’s because the piston is the weakest link? I’ve seen and read people run stock pistons with a good tune and no issues. That’s why I wanted to run lower compression. You think oem flat tops won’t be good for 12#?

 

As mentioned, On a stock cast piston it's hard to push these things.

Can you do it? Yes. Should you Do it? No

Why Not? Well todays pump gas is full of various solvents and chemicals that when mixed blend together creating this pump gas. There are alot of variables. Who blended it? How long has it been sitting around? Is it a summer blend or a winter blend? No two oil companies Blend the same mixture to create gas. You will even find variances between Refineries in different regions. Not to mention differences from batch to batch from the same refinery.

It's not always about the piston itself either. Even the Gen 4 rods can bend...

 

I would be tempted to run the motor as is with the 243/799s and get a truck turbo cam from your favorite cam supplier and let her run like that. I think you'll be $$ and HP ahead in the end this way.

Id rather make 550hp on 10lbs than 490hp on 12lbs if I had the choice: and I think that's about the realm you're headed too, IMO

compression also helps spool and generate torque: so I wouldn't drop comp unless absolutely necessary: like from 13.5 to 10 for boost