Does anyone know the quench space for this arrangement?

Stock LS1 piston
AFR 205 milled to 59cc combustion chamber
0.040" head gasket

 

Quench = compressed head gasket value - piston to deck value

LS1's are usually out of the hole and it can range from .005>.010

So measure your piston to deck value and plug into the formula.

 

Thanks Pred. I thought head design came into play, but I now see that as long as the quench pad of the head is "even" with the gasket surface of the the head, it does not. And along those same lines, it would follow that milling the head does not change the quench space. Is that right?

So the quench with a 0.040" gasket would be between ~0.030-0.035".

Judging from what is said in this article, that's very tight! In their opinion, too tight!

http://www.chevyhiperformance.com/techarticles/94138/

Some images, courtesy of CHP....

 

.030-.035 is ideal quench for stock shortblock LS1/LS6. That magazine is trying to cover a lot of motors including old SBCs. The LS1 is built with much tighter tolerances. You know the recipe...quit questioning it and just do it!

 

lol This is worse than when I was trying to pick an exhaust system!

My car is probably in good shape wear-wise: 30kmi, no prior use of nitrous....

My tuner is concerned about the high compression and the potential for pinging. (93 octane, 10% ethanol)

Oh screw it! I'm going to follow the recipe and if it pings we'll work with the timing.

 

and make friends with someone that sell TORCO

 

Party crasher!

I don't want to have to use TORCO!

 

The recipe was invented by Tony Mamo. He lives in southern California. The best gas they have is 91 octane. With the tight quench of .032", he was able to run full timing on 91 octane. Honestly, if you follow the recipe to the letter, you should have no worries.

 

Thought I would chime in here quickly...

59cc's with flat top pistons (no valve reliefs) is too much IMO for CA/AZ crap 91 octane. The most I normally recommend for someone pushing it to the max is 62 cc's with an .040 gasket. Assuming valve reliefs and a cam that is 232+ @ .050, then I would recommend 60 cc's in the land of 91 octane....59 cc's might be pushing it on 91 (usually no problems with 92 or 93), however with a fairly sizable cam to bleed off the cylinder pressure a little you might squeak by with the right tune and a 59 cc chamber (on 91 octane fuel). Even if you get a little knock retard here and there its not the end of the world....thats what the damn computer is there to do anyway (help you out in the event it senses detonation). If you were attending a track event (sanctioned or otherwise....LOL) and absolutely knew you wanted the most from your combination, then you add Torco or splash some 100 unleaded for that tank only....still lets you cruise around the majority of the time without the added expense and hassle.

Just some food for thought....dont even think about 59 cc's without valve reliefs....it will detonate on 91 octane in any kind of heat and backing off the timing is just going to result in lower power which wasn't the objective of putting the combo together in the first place.

Tony M.

 

Ok *sigh*, here's what old Shev is going to do.

I'll get the AFR 205's with a 62cc combustion chambers. I'll use the 0.040" thickness Cometic gaskets, and the "Tony Mamo" cam.

I won't worry about leaving a little performance on the table, if I'm at or above 410rwhp and 400rwtq I'll be happy as a pig in swill. And this combo will still be good even if/when 93 octane is no longer available here. Plus I'll have a wee bit more PV clearance...

In the event that I can't get the Cometic gaskets to seal, I can go to the thicker gaskets and have the heads milled.

I think I'm done!

God bless LS1tech!....and it's excellent membership!

 

You'll be very happy with this combo with less to worry about

 

Phil, hurry up and install your parts!

 

its in the shop now

 

Size of the combustion chamber dont matter for quench, so by going with the 62cc your only losing a touch of compression. Good question for Tony, or anyone playing with quench, which will effect the Detonation quicker -1cc of chamber size, or -.005" thickness in gasket? (just threw the two different measurements out there dont worry). I am running 59cc, .040" HG, .010" out the hole, -2cc VR, for about 11.47:1scr, 9.437:1 dcr on 92pump no kr with 28* timing NA @ 13.1:1AFR.

 

Good luck man. After almost 4 hours of tearing my car apart, I'm ready to pull the heads off, and start installing the exact Mamo recipe you are following. I'm a bit nervous about not getting the gaskets to seal- is the consensus no copper or copper spray? I can tell you that there is no way I can do this twice so if I spring a leak I'll be fuked- cuz I'll be out of time to fix it for most of the summer and my car will be out of commission.

so are you using copper spray with cometics or no?

Best of luck to you.
Dave

 

There are people who have claimed to have run .025" clearance without problems with an LS1. I would make sure it is warmed up before reving at the clearance though.

How big are the valve reliefs on the stock piston? How much are you planning to flycut?

 

I haven't decided yet, Dave. I'll have to see what people are having success with but I'm leaning toward using copper spray.

Good luck. And make sure you post your results!

 

NO copper spray. The manufacturer of the gasket calls for a dry install....I would imagine they know what they are doing.

I have built a handful of LS1's with Cometics and never experienced a problem with leaks. It comes down to the proper prep and two very flat surfaces. Assuming the block is straight and the heads are also (which can be checked with a machinist's straight edge if in doubt) what I have done successfully in the past is to use a medium length bodyman's longboard with either 320 or 400 grit wet/dry sandpaper and I use WD40 as a lubricant. This is of course after removing the larger debris that might be left over from the removal of a composite style OEM gasket. The later model OEM stuff uses an MLS type which usually comes off without much drama or left over residue on the block surface. Anyway....work the longboard diagnally over the blocks deck (remove the dowels) and go in different directions diagnally right, diagonally left, and even straight across. Be generous with the WD40 and the paper will cut a little better and last longer. Wipe clean when your done and you should have a very clean shiny deck with no dull areas which would indicate a low spot. This process also removes some of the risers in the metal from the milling of the deck and leaves a nice smooth surface for the Cometic gasket to seal to. MLS style gaskets need a fairly smooth finish to seal up correctly. I usually do the exact same prepwork to the deck of my cylinder heads, even though the mill we use at AFR leaves them very smooth....I just spend less time on the heads because they are real staight and very smooth right out of the box...

Hope this info helps...

Tony

 

How much material needs to be removed to get a 59 cc chamber on a set of 205's? They would be going on a 402 with a 14cc dish.

 

Each cc = .006 milled, so at 66cc out of the box, you need to take off .042 to get 59cc. I'm pretty sure it's 66cc out of the box....