I'm almost certain Stano has the 62 cc heads. He told me that his compression ratio was 11:1 which I don't think is achievable with 66 cc.

He also replaced the injectors for more power, but stock cam and exhaust. He did make 409 RWHP on a generous dyno. Those numbers might not be too easy to repeat around town. I saw the AFR car that made 480 RWHP make 460 RWHP on a more stingy dyno. Best,

mtv

 

As it was explained to me, having .025 less deck height translates to about 4cc less combustion chamber volume. If you have heads milled .030 and then have a deck on the short side of that tolerance you can have up to an effective milled head of .055" which comes out to around a 56cc combustion chamber. That would put the CR around 13:1. On the other hand if you have heads milled .030 and have a deck on the tall side you could end up with an effective .005 milled head which would put you at around 10.3:1. These are extreme tolerance differences, no doubt, and for the most part more theoretical than real life, but because the tolerance is there the potential for extremes exists.
I too find it difficult that GM would have several different thickness gaskets available at head mounting time, but that is what I was told and I am just passing that on. I basically derived from that info, that one should determine deck height over piston TDC and compute the actual CR based on the two items that one can control. Gasket thickness and head milling. A blueprinter would have no issue with this since those tolerances would be 'blueprinted out'. However, us guys that want to do a h/c swap, have to hope that aftermarket heads would fit without too much post purchase fiddling. What I am wondering, and starting to realize is, for the majority of us weekenders that undertake these projects the tolerances are within reasonable windows and we don't have to worry about the minutia. But there are some that go into a project armed with the best knowledge they have been able to get and have problems that are difficult to correct, mostly because the tolerance was out, or on the hairy edge.
As far as AFR milling the intake port I'm sure they would do that when milling the surface. Those numbers were just what I was given. I'll bet the max figure was probably based on the amount of clearance under the manifold more that the left/right head spacing.
I called the number on the website and asked to speak to a technical rep. Maybe someone else can call and clarify this.
As for me, I am going to buy my heads shaved .015" and use stock LS1 gaskets. I'm going to have the motor out on a stand because I'll be doing some internal work on it and I'm checking the deck height and ptv clearance as well. I will probably have an set of ISKY flycutting tools hanging around just in case. I submitted you would probably want to have the heads milled after you determined the deck height because it is expensive to do a second time, or to have to flycut the pistons to drop CR is a waste. Didn't mean to rewrite the Magna Carta here, just wanted to discuss this at length and explain I am the messenger and I hope I got the message correct.

 

I'm having the AFR H/C job done right now. The car is in the shop and work begins tomorrow, I hope, since it didn't start today. I asked about the tolerances reported in this thread and was told that +/ - 0.025 deck thickness is a huge differential and is an unlikely occurance.

If Arkay's calculations are correct, then GM QC would be out the door with that kind of varriance. I'm running a standard gasket. A very thin gasket could increase the possibility of valve piston clearance, a CR above 11:1 that could ping the engine and or cause timing issues. The last thing I want is to be constantly in the shop trying to get the timing just right or forced to buy only the very best (most expensive) fuel. I like filling up at Costco and want to continue. So it's the 62 cc head, 220/224 581/581 115 LSA, an underdrive pully a better oil pump and 400+ RWHP on an A4 AE. Best,

mtv

 

Every .006" =s 1cc. So your about .018" higher than average (.007" at least that I have seen or heard) on your deck height. Thats about 3ccs. You can measure the thickness of the AFR heads and compare them to stock. I forgot what the thickness is on LS6 heads but I have measured them before to see whether they had been milled or not. Just for reference my heads have been reworked twice and have had two .005" cleanups done on them which results in .010" shaved off the head. My Deck Height is .014 due to Diamond Pistons w/6.125" rods and a .005" clean up on the block. So that puts me at .024" when considering the piston out of the hole and heads being milled. I run a .581 lift cam...but I also have -2cc valve reliefs. Just make sure the piston to valve clearance is checked you should be ok. If I remember right there shoud be about .005" clearance because things stretch under RPM...go double check that.

Normal deck that I have seen ranges from .003-.009 out of the hole. If the heads are not milled like .030 you should be ok. Nevertheless Piston to Valve Clearance should be OK. Stock 2002 MLS Gaskets are .054". Subtract your deck height and that puts you at .029" quench. I think you will be just fine.

 

MTV, just to keep things clear, I didn't state the the tolerance was +-.025 but the TOTAL tolerance is .025. I implied that with my example and was incorrect. Sorry for that error. It was late. That would put the +- figures in the +-.012 range. But that could still acount for enough CR variance to cause detonation with heads milled as small as .030.

 

The standard AFRs are 66cc. We offer decking for a additonal $75 when you order the heads. The key like several guys have said is to always check p/v clearance with bigger camshafts. We've run a 224 & 225 camshaft with heads cut 25 before & had no issues. That being said its always better safe than sorry. We have 10 sets of the AFR heads on order, if anyone has any questions or is looking for a set drop me a IM.

Jason
Texas Speed
www.texas-speed.com
806.866.0734

 

Ok, deck height variance was what led to messed up compression leading to detonation on an AFR built LS engine with AFR heads milled .30 for a 62 CC. The solution is to check deck height and then work backwards. Seems like a lot of work. I am going to go milled .30 for a 62 CC and use a stock gasket (not certain of its exact thickness) & unless I have an “extreme� variance on the low side I hope to be fine with no detonation on 93 octane. P/V clearance should not be an issue with a lift of .566 (I hope). How does duration matter ? (EDIT) duration @.50 or advertised duration? (mine is 286 which is longer than the newer xe lobe 224 cams) What compression does a .25 mill allow ?
Thanks for the tough info guys.

 

my heads spinnin

 

Oh yea and how much HP can I expect from my K&N....Haha J/K
Look what you started.