espey34

iTrader: (1)

Doing a very mild build on a 05 lq4 4l80e that I’m swapping into my 05 Silverado 4x4. Looking to keep it very well mannered as I do occasionally tow with it and plow snow.

I ordered a tick towmax stage 2 214/224.571"/.561" LSA114+4. I plan on getting a set of 243 heads and milling them to bump the compression as close to 11:1 as I can without running into clearance issues. Also will be using the stock mls gaskets .051” thickness.

Will i I be safe taking .030” off of them without ptv issues and can anyone tell me what comp ratio would be with that setup?

Ls7colorado

iTrader: (3)

I wouldnt want 11:1 compression plowing snow.... mainly because I wouldnt want to be running premium fuel in a work truck
With that small of a cam I doubt you would run into issues, of course I would still check though.

espey34

iTrader: (1)

I get what you’re saying but this truck is my daily driver and I don’t do a ton of work with it. Just looking for something a little more fun to drive but still be useable when I need it to work hard.

0352Marine

Without decking the heads and using a .051” head gasket and averaging the piston deck height to .006” out the hole. Some are .002” and others are .008” won’t know until it’s measured but going off an average of .006” your already at 11.16 to 1. Remember the stock heads on a 4” bore are the 317 heads which have a cc of 71. 243 heads are a 64cc

0352Marine

Might want to do some more research before you create an expensive fireworks show.

espey34

iTrader: (1)

Are you thinking about the lq9 possibly? 10:1 stock compression vs the lq4 having 9.4:1 stock?

Everything ive read has very mixed opinions on 243s milled .030 on an lq4 anywhere from 10.5-10.8:1

0352Marine

Yep sorry your right. I didn’t notice you had said LQ4. Duh

0352Marine

I calculated 10.82 to 1. It would be more accurate if I had known piston to deck height and head gasket bore size. This is pretty close though. The dish is a -6cc

0352Marine

If you deck the heads .030” you’ll be around 11.66 to 1

0352Marine

11.66 to 1 would require you to run either a octane booster or race fuel. I try to stay around 10.5-10.8 to 1 for 91 octane which is what is sold where I live

0352Marine

This is a good write up for compression calculation. I don’t like using the calculators online because some are setup for - to be a dome and others are + for dome. It’s always been best for me to do it by hand.

https://www.google.com/amp/blog.jepi...%3fhs_amp=true

Che70velle

iTrader: (6)

Im at 12.42:1 on 93 pump. Lots of guys run 12:1 on 93. The cutoff is 12.5:1 to safely run 93, but I understand 93 isn’t available everywhere. Just wanted to keep this legit concerning requirements.

Germansheperd1

Maybe on an old tech iron headed engine but not so on a engine with aluminum heads. My Mustang is 11.85:1 and it runs excellent at 30* initial timing with Shell V-Power 93.

64post

iTrader: (5)

Do you mean 30* total? And not initial?

Germansheperd1

Initial

patSS/00

iTrader: (6)

For a PTV calculator, try this:
PTV calculator
You have to know the valve drop. Also the values for the cam lobes (tappet lift @ TDC) have to be approximately right, you can get those online for Comp cams, if your cam is not Comp you can find a Comp cam that is close and use those values.

Shtstr

what inlet valve closing point are you using. ABDC.
​​​​​​Just wondering what dynamic compression you are running.
most say 8.5 Max for 91USA octane 95 octane Australia.

stockA4

Your combo sounds great to me. No issue milling the heads a bit for PTV which doesn't become an issue unless you're using a larger cam that's opening the intake before TDC.

everybody on here always seems to forget the fact that a STOCK LS2 is 11:1cr!!! This same engine was installed in lots of heavier vehicles including trucks! There's a truck called the trailblazer SS and it comes with an 11 to 1 compression LS2 and you could tow stuff with it and plow snow with it if you wanted to. Stock engines are designed to run fine on crap 87 octane fuel even if premium is recommended, the LS2 can survive its entire life on 87 octane if you're a cheapskate, Look at the stock timing curve on that setup. Nobody's reinventing the wheel here, You're not going to break anything or blow anything up

Che70velle

iTrader: (6)

Actually the LS2 compression ratio was 10.9…but what’s 1/10th a point among friends? The LS7 was 11:1 for anyone following along.

68Formula

Towing and plowing on 87 with 11:1, is a quick way to find out if those knock sensors are working.