Jesse_Boyer

update:
1. several have recommended I head for 11.3-11.5:1. Another member (which I've quoted in another post) is running 11.7-.8:1 and having great luck.

2. Also, according to the sheet below, can anyone determine the size of the valve reliefs?

3. While many have said I need to go with a 0.040" Cometic gasket, several other very prominant members have said they ONLY use GM MLS gaskets. Much more forgiving if the surface isn't 100% perfect. Since I won't be pulling the shortblock to machine, this seems like a wise move. Is there any thinner GM MLS gasket available for this application?

4. Playing with the calculator... -0.007" out of the hole, 0.051" gasket, 2cc reliefs (speculating at this point until someone can tell me what they really are (emailed JE as well)), 59cc chambers. = 11.21:1. I was actually hoping to get it up a bit higher as another member is running ~11.8:1 and he's having pretty good luck. If I find a 0.040" gasket, that would take this to 11.63:1... pretty much what I'm looking for (if I've guessed correctly at -2cc of valve relief.)

5. LG (and another individual) recommended I ditch the 225's and go in favor of 205's or 215's. Sadly, I already have the 225's at home.



I'm trying to answer a bunch of details as I want to swap the top-end of the motor while I'm home on 'leave' from my deployment. Thus, I need to iron out all the details, bang out the top-end swap in a day, and tune/enjoy the car until i go back for another 6-months.

Bottom end: (and other items that I won’t be changing)
700 miles on fresh bottom end.
LS1 block honed to 3.905
JE pistons; flat with valve reliefs (spec sheet is attached at the link below)
Scat Rods (ARP bolts)
Stock crank
G5x4 from LG
ls6 oil pump
42lb squirters
1-7/8” ARH’s w/o cats
Vararam

Current top end:
stock MSL head gaskets
Patriot heads w/ 59cc chambers (reported from the previous owner),
LS6 intake, stock TB.

It will soon enough be replaced with AFR 225’s (PN #1660 for small-bores) and a FAST 90/90 or 92/92 combo.
I’m looking for the compression in the 11:5.1 range for a nice N/A setup. I don’t DD this and it doesn’t see any thing but BP 91-93 fuel. Unless you recommend a different CR, that's the current goal.

Having digested the details, what should I run for head-gaskets and chambers to get the CR right? Cometics or GM MLS? I’d rather not mill the heck out of the heads if I don’t have to as it limits what I can do with them after I’m done (selling them to someone else, frankly).

Much thanks, all.

JE Pistons spec sheet:

chevy406

Short answer - get the AFR 1660 with 62cc chambers and use .040" Cometic head gaskets and you will be right around 11.0:1 with those pistons.

tblu92

When I did my heads/cam change i was told the same thing from many vendors about which head gaskets to use---ALL said that IF you are not removing the block to re-surface or clean up use-- only the GM stock graphite type gaskets---reason being with a UN-surfaced block it may have some normal slight variation or flaws on the surface---So in order for the gaskets to seal up prperly and take-up the variations you need ones that can be more forgiving---On a resurfaced block that is 100% flawless you can use all the aftermarket styles as they will seal then easily--- JMO

chevy406

If you are not planning on a power adder, then the Cometic head gaskets will be just fine with a good cleaning of the deck. Granted if you have any gouges or scratches that you can catch with a finger nail you will have to address them.
The main reason you want a .040" head gasket is for the tight quench with the AFR heads. It will help a lot with running the 11:1 CR.

You did not mention piston to valve clearance, and that should be checked before final assembly - regardless of your aftermarket pistons.

Mr. Jones

I just completed a similar build.
I went with the cometics 0.041 gasket.
I read about the leaks some people were having. Cleaning and the lack of scratches are what work. Use lacquer thinner to clean the surfaces.
11.0-1 CR sounds good but look into Dynamic compression ratio,
this is the average compression. It takes into account the valve events.
look for a 8.7-1 DCR this will work with 91 octane.
There is a excel program on the forums that you can plug in the numbers and get a DCR.
Post your cam specs and I will try to run the numbers for you.

Jesse_Boyer

Those are the heads I have, but I'll need to mil them down to 62cc. I have 66cc heads. Will I be creating any alignment issues with the FAST if/when I have these milled down to 62cc? Any idea how much, approximately, they will have to take off to get the chambers down to 62cc?

I need to look into more gaskets and find some thicknesses. I was planning on Cometics, but tons of guys run stock MLS gaskets with great results.

I will definitely be checking P/V with the new motor. No point in it all together only to have it crash/burn...

LG doesn't post the specs. They can make great power with the G5x4, but they know the specs too! I sent an email requesting the same information (same exact verbage as the first post) from LG.

There is a couple people on the forum that know the specs and I would really, really appreciate it if they'd chime in on this question.

chevy406

With 66cc heads and the stock GM MLS .053" thick head gaskets, you will have 10.1 CR. Head gasket thickness not only affects compression ratio, it also affects your quench. You want as thin a gasket as you can use yet still maintain PTV clearance.

Typically it takes .006" milling of the deck to reduce the combustion chambers by 1cc. So you would need to mill your 66cc heads by .024" to get them at 62cc. I am sure that is all AFR does too. That won't cause any problems with your intake manifold.

I did a little searching on the LG4x specs yesterday, but never got a definitive answer. Something like a 236/244 duration with low .600" lift... Plugging that into the PianoProdigy spreadsheet shows you will have a dynamic compression ratio ~ 8.00 (assuming the 62cc chambers and .040" gaskets). Even more reason to get the static compression up if you are dead set on that cam. You might even try to bump the CR up to 11.3...

Jesse_Boyer

I actualyl already have the cam... it's in my current motor. PM coming your way.

Mr. Jones

Quick and Dirty Cam/SCR/DCR Calculator Spreadsheet
Modified and Simplified by PianoProdigy - PianoProdigy@gmail.com
Values that are green are standard stock LS2 values (if only swapping a cam, leave them alone).
The blue values are calculated and thus, are not editable. Compression values are orange (not editable).

0.006 0.050 0.200
Intake Duration - ID (first number) 285 236 157
Exhaust Duration - ED (second number) 293 244 165
Lobe Center Angle - LCA (also known as LSA) 112 112 112
Intake Centerline - ICL (LSA - degrees of advance e.g. 114+2 = 112) 110 110 110

Intake Valve opens - IVO 32.5 8 -31.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 72.5 48 8.5 ABDC
Exhaust Valve Opens - EVO 80.5 56 16.5 BBDC
Exhaust Valve Closes - EVC 32.5 8 -31.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 114 114 114
Overlap 65 16 -63 degrees

Bore 3.905
ST = Stroke 3.622
RL = Rod Length 6.098
Number of cylinders 8
Deck Height (how much pistons come out of the hole) -0.01
Piston Dome or Dish (- for a dome + for a dish) 0
Compressed Head gasket thickness 0.041
Cylinder Head Chamber Volume 61

Static Compression Ratio 11.60 :1
Dynamic Compresion Ratio 8.62 :1
Rod to Stroke Ratio 1.68 :1
Bore to Stroke Ratio 1.08 :1


Note that a 59cc chamber -2cc of valve relief in piston = the 61 cc in the calc

236/244, 112cl, 2 deg adv cam plugged in-not sure how close this is to what you have.

chevy406

Using some revised duration numbers for this cam, from the same spreadsheet... (note I am not exactly sure on the deck height of your block, .007" out of the hole is typical on the LS1).

Intake Duration - ID (first number) 289
Exhaust Duration - ED (second number) 293
Lobe Center Angle - LCA (also known as LSA) 111
Intake Centerline - ICL (LSA - degrees of advance e.g. 114+2 = 112) 109
Bore 3.905
ST = Stroke 3.622
RL = Rod Length 6.125 (typical aftermarket rod length)
Number of cylinders 8
Deck Height (how much pistons come out of the hole) -0.007
Piston Dome or Dish (- for a dome + for a dish) 3
Compressed Head gasket thickness 0.04
Cylinder Head Chamber Volume 60
Static Compression Ratio 11.23
Dynamic Compresion Ratio 8.28

I would recommend bumping the static CR to 11.2 using .040" gaskets and 60cc chambers. Using the 62cc chambers at 11.0 CR will have dynamica CR at 8.07.

By the way, I thank you for your service to our country.

Jesse_Boyer

gents, much appreciate the calcs! I wouldn't mind playing with that a bit. If either of you could send me that spreadsheet, I would be very grateful. JesseLukeBoyer @ Hotmail.com

This is from another user who is running the same cam.
Just looking for some thoughts on running a bit more compression to get the DCR upwards of 8.7CR like this user. Necessary or not? To do that, i'll have to mill a bit more as I'm certain I have larger reliefs than 1cc. If that's the case, when am I going to run into trouble with intake alignment/etc? P/V clearance?

I will have my wife locate/scan the piston cut-sheet from JE so we know exactly what we're working with. The only detail I'll be missing is the distance out of the hole. I don't know if the block has been touched, unfortunately.


edit: I forgot to say thank-you. However, the soldiers here deserve all the thanks/credit/praise. As one of the engineers, I simply have to deal with the living conditions and the other mildly unpleasant items. (truth be told, I very much like what I do and manage to stay extremely happy here). The soldiers, however, deal with minimal accommodations. Their living conditions aren't nearly as nice as what I'm afforded and they're doing the actual 'work.' While I play a roll, those ladies and gentlemen are outside-the-wire... carrying out the mission. I'm a pawn... they are the Kings and Queens of this operation.

Mr. Jones

I used -0.10 for the piston deck height.
most aftermarket pistons pop up a little higher than stock.

Jesse_Boyer

I'm assuming you used -0.01, not -0.1, correct?

Also, just to put this two places in the thread... this is the JE pistons spec sheet.


It lists the depth of the cuts for the valves, but not the diameters. I've sent an email to JE regarding the volumes and typical protrusion from an undecked block and hope to hear back from them early this week.