00pooterSS

iTrader: (40)

If it were mine, I wouldn't be too afraid of it ending up in the high 10's on compression on min 91 oct and I think I'd prefer mid 10's at minimum

Keep in mind trucks are now coming with over 11:1 from the factory in a lot of cases and they have to keep compression low enough for idiots doing idiot things. In other words they can keep them idiot proof even in the 11.x:1 compression range

Direct injection does help with detonation control a bit.. but my truck with the 5.3 is 11:1 stock, the 6.2 is 11.5:1, and you can get a 6.2 with a max tow package.. and both the engines can be ran on 87. It's not preferred on the 6.2, but they can WITHOUT blowing up. Again, that's with GM considering that someone may run 100% throttle with a trailer up a grade for a long period of time.

Just make sure you punch in your setup into a DCR calculator for the minimum octane you'll be running since that is the true number that will dictate what you can get away with. General rule of thumb is the bigger the cam the lower your DCR will be though, which puts you safer if you're not gonna be on stock cam. However if you cam it right you'll be looking for the lowest possible intake valve closing point to build low end which pushes up DCR. So check it all out.

You can degree the cam to get your DCR just right too.
I imagine around 10.5:1 with an IVC of around 36 ABDC would be the sweet spot for you. But run that by a tuner and the cam manufacturer.
I know just enough to be dangerous at this point so get with some of these tuning gurus that can tell you a safe DCR for running 91
Edit: getting this right will give you better MPG too, likely better than stock even with the mods.

Keep in mind if you really get worried about knock when towing, you can always downshift the truck when you tow, instead of letting it lug at high load and low rpm to help stave off knock. Hell I think most of us do that already anyway.

1994Vmax

iTrader: (4)

Truck torque build is use the 706/862's every time. If you want to get spendy with them ( and it's not that spendy) a 2" intake valve is a nice touch.. it even the fits the stock seats better than the 1.89" does. Compression isn't a big deal.... my 2013 Max Trailer 6.2 truck is 10.5:1 and they do quite well on premium pump fuel. You will be around the same 10.5:1 mark with the 706/862 heads.

Leave the 243 heads and sell them to some goober that think they are "Corvette" heads lol. Will pay for the smaller 706/862's which are basically able to be had for free and whatever you want to do with them.

00pooterSS

iTrader: (40)

The 243's he has are already milled to what should be almost exactly the same as a 706 head

They are both great heads. But the 243's are free since he already has them. I don't know how much better the 243 is, but it's for sure not a worse head. Especially considering some of the 706's crack. I'd just run the 243 myself.

1994Vmax

iTrader: (4)

He can also easily sell those 243 heads to some knot head for a ridiculous price as they have this mystique around them they do not deserve. Very few 706's crack and most that did have already been dealt with. Fun fact... Castech made 243's too.. and they cracked too lol.

Not my build though so whatever floats your boat however giving up 20 lb ft or more below 4 grand is what I would be looking at and that is reality with the 243 versus smaller port heads... This is one of those many instances of being on this forum and it's not a rAcE tROk lol.

00pooterSS

iTrader: (40)

What? (the bolded part) 243's are stock on a 5.7, how is recommending them recommending them race ****? Besides I recommended against square port which would have been your "rAcE tROk" recommendation..

243's crack.. well there sure are a hell of a lot less threads about it. So i'd roll the dice toward the 243 if it was my build. But in either case I would look for the castech logo and weigh out the options.

And for port size the 706 is a 200 cc and the 243 is a 210

This is going on a 6.0, a 6.0 should not have issues keeping up velocity with a 210. Loss of port velocity is where you'll see the drop in power you're talking about.

Do you have any posts I can read through that show a 243 is down 20 ft lbs below 4k vs a 706 on a 6.0?
I'm all for learning and don't mind being corrected. I'd love to read on it so I don't give out poor advice.

Some guys think 243's are "omg corvette heads" and other idiots think 706s "roooool alllll"
They're both great heads. Anyone with a brain can admit that.

1994Vmax

iTrader: (4)

Because this forum gives advice off of things like the internet... and focuses on high rpm hp. If you want fun pictorals you can look at Richard Holdner's 706/799 comparo on a 6 liter but I don't reference it directly because his cam choice is a lot larger than what is being used here. I think he gained 9 hp at the top of the rpm band with the 799 and lost torque all over the curve below 5000 with the 799 head with a much larger performance oriented cam.

The flow on these LS heads is incredible... and you do not under any circumstance need a head that flows 250 cfm or so on an engine where the OP specifically says its staying around and below 4000 rpm. That's why... It's why I always use the race truck thing... because it's all people care about. You will have better control of port velocity with the smaller head and in turn make more torque where it matters. I also do this stuff in the real world and find a lot of replies here somewhat comical. Have a good one... you are just going to argue with me how I am wrong anyway and I am not replying any further.

00pooterSS

iTrader: (40)

No you just realized I'm not the typical internet idiot you can talk **** to and make yourself feel better.

That's why you're running off.

If I remember right that's the test where they used stock chambered 706's against stock chambered 243's and the test with the 243's didn't have a chance at keeping up in the low end due to lower compression. Every 706 nut swinging doofus missed that part.

His first test he did that on was on a 5.3, the second was on a 6.0

On the 6.0 they tested STOCK 706 against 799 heads. The 706 was up 12 ft lbs over an UNMILLED 799

AND 799's are not equal to 243's!

00pooterSS

iTrader: (40)

Here's the proof to back it up with pictures and flow numbers. 799 versus 243

https://ls1tech.com/forums/generatio...ifference.html


With milled 243's, he can have the low end, and the top end.

I posted proof. Where's yours.

00pooterSS

iTrader: (40)

Doesn't need a head that can flow 250?
You do realize there will be times he uses full throttle right


And did you really just say "you're just going to argue with me so I'm not replying any further" How fragile are you dude!?

But seriously, read what I posted above. There's actual good tech info in my posts to support my stance and this is just a conversation. You can do it buddy, it's not gonna hurt you and you'll be okay.

RedXray

If you have HP Tuners you could easily flash in a "tow tune" with some timing pulled in both the high & low octane tables. A quick flash in just a matter of seconds (if your scans are detecting knock). You could also adjust the "shift scheduled" under the performance tables (tow/haul button) to keep the engine at a higher RPM during up/down shifts. This will help keep the engine out knock by eliminating any low RPM lugging situations. Towing only 10 times a year there are workarounds to be able to enjoy a nice compression ratio without hurting the engine... If you have the device.