2004 6.0 NV4500 Tahoe

[iamdub]

Next point of thought, which gaskets to run.
ls9 gaskets 10.07:1cr
LQ4 gaskets 10.16
Cometic.041 and have 10.4:1

Currently has 10.39:1cr with the 862s and LQ4 gaskets.

What's the difference in the 243s compared to your current 862s?

Unless yours is tuned to the ragged edge on a consistent type and quality of fuel, you'll see virtually no difference between 10.4 and 10.07 static compression ratio. If it's already tuned for ~10.4, you might as well stick with that unless the 243s put you in danger with the quench height.

What can make a difference is the flow characteristics between the heads since that will alter the dynamic compression ratio.

Also, Fel-Pro has .041" compressed thickness MLS gaskets in 3.945", 4.100", 4.175", 4.200", and 4.270" bores for half the price of Cometics.

 

[iamdub]

Milled .010 so that puts it right at 10.4:1 with the cometics. Quench should be really good then too right @iamdub ?

Depends on piston height at TDC. Do they come out of the hole any?

Them 243s chambers are stock other than the .010" mill? Was their volume measured to know exactly where they're at? They're usually larger than advertised so that milling might've just put them at or closer to their advertised volume of 64.5.

 

[Dantheman1540]

What's the difference in the 243s compared to your current 862s?

Unless yours is tuned to the ragged edge on a consistent type and quality of fuel, you'll see virtually no difference between 10.4 and 10.07 static compression ratio. If it's already tuned for ~10.4, you might as well stick with that unless the 243s put you in danger with the quench height.

What can make a difference is the flow characteristics between the heads since that will alter the dynamic compression ratio.

Also, Fel-Pro has .041" compressed thickness MLS gaskets in 3.945", 4.100", 4.175", 4.200", and 4.270" bores for half the price of Cometics.

Depends on piston height at TDC. Do they come out of the hole any?

Them 243s chambers are stock other than the .010" mill? Was their volume measured to know exactly where they're at? They're usually larger than advertised so that milling might've just put them at or closer to their advertised volume of 64.5.

The main difference between the 243s and 862s is the porting on the 243s. They should flow considerably better at the top end. All valve train from the 862s will be swapped to the 243s so no changes there.

Did not know felpro had those gaskets I will have to look for those!

The bottom end is a bone stock LQ4 so tbh idk, I’ve only ever had the pistons exposed one time when the valve dropped.

I received no data on chamber measurement but I thought I remembered reading LS6 243s which these are typically have slightly smaller chambers.

 

[iamdub]

The main difference between the 243s and 862s is the porting on the 243s. They should flow considerably better at the top end. All valve train from the 862s will be swapped to the 243s so no changes there.

Did not know felpro had those gaskets I will have to look for those!

The bottom end is a bone stock LQ4 so tbh idk, I’ve only ever had the pistons exposed one time when the valve dropped.

I received no data on chamber measurement but I thought I remembered reading LS6 243s which these are typically have slightly smaller chambers.

Bone stock bottom end that has never been milled? Every block is different and should be measured. But, I believe the consensus is that the piston comes out .006-.008" on the LQ4. If that's the case, you should be safe with the PTV clearance but the quench would be questionable. You have any modeling clay? After swapping over the valves, I'd get them chambers measured. You gotta know what you're working with.

 

[Dantheman1540]

Bone stock bottom end that has never been milled? Every block is different and should be measured. But, I believe the consensus is that the piston comes out .006-.008" on the LQ4. If that's the case, you should be safe with the PTV clearance but the quench would be questionable. You have any modeling clay? After swapping over the valves, I'd get them chambers measured. You gotta know what you're working with.

I was assuming .006 but I don’t know if the block has been milled or not the PO only said it was “refreshed” I did borescope the cylinder when I did plugs Saturday and I can see hash marks so maybe it was milled and the cylinders honed but that’s pure speculation.

The heads have the standard Ls6 valves in them now, I could measure the chambers with them in correct?

 

[Rocket Man]

Phuck me Amazon will have the gaskets here Monday so I guess it’s game on Donkey Kong

Gotta love Amazon.

 

[iamdub]

I was assuming .006 but I don’t know if the block has been milled or not the PO only said it was “refreshed” I did borescope the cylinder when I did plugs Saturday and I can see hash marks so maybe it was milled and the cylinders honed but that’s pure speculation.

Mine, with 200K, had pretty strong crosshatching. This is no area to be speculating. You can either take the "safe" route and sacrifice efficiency/power or measure a few things and optimize this bish (for NA or very low boost) while you have the prime opportunity.

You've seen this, but to refresh your memory, here's mine upon teardown for its refresh: https://www.tahoeyukonforum.com/threads/growing-up-doesnt-have-to-suck.93510/post-1425133

The heads have the standard Ls6 valves in them now, I could measure the chambers with them in correct?

Cool! I thought they were bare heads. The other valves, if previously machined, could sit a little lower on the seats, raising the CCs. Measuring the 243s as-is would at least give you a really close idea of the volume. You can always measure the piston height once you have the 862s off and order the head gaskets from Summit. If you have to get some from Cometic, you'll likely be down for a few weeks, a month, six weeks... who knows?

 

[Dantheman1540]

Mine, with 200K, had pretty strong crosshatching. This is no area to be speculating. You can either take the "safe" route and sacrifice efficiency/power or measure a few things and optimize this bish (for NA or very low boost) while you have the prime opportunity.

You've seen this, but to refresh your memory, here's mine upon teardown for its refresh: https://www.tahoeyukonforum.com/threads/growing-up-doesnt-have-to-suck.93510/post-1425133




Cool! I thought they were bare heads. The other valves, if previously machined, could sit a little lower on the seats, raising the CCs. Measuring the 243s as-is would at least give you a really close idea of the volume. You can always measure the piston height once you have the 862s off and order the head gaskets from Summit. If you have to get some from Cometic, you'll likely be down for a few weeks, a month, six weeks... who knows?

Well, I found that Felpro has .041 gaskets that can be here in a week as can the Ls9s.

You make a good point and I don’t mind having it down for a week. The next questions are how do I measure piston height and chamber volume easily?

 

[Dantheman1540]

This is totally not okay, oil pressure was a little low this morning until it got warm, probably down to 15psi but no clatter or ticking. This is with 5w30 and 1qt of Lucas oil Stabil, makes me kinda want to do an OP or O ring if I'm gonna have the motor apart for a week.

 

[pwtr02ss]

This is totally not okay, oil pressure was a little low this morning until it got warm, probably down to 15psi but no clatter or ticking. This is with 5w30 and 1qt of Lucas oil Stabil, makes me kinda want to do an OP or O ring if I'm gonna have the motor apart for a week.

61 inside? You mad man