I'm looking into two possible options for my h/c setup on my Z. The mods are LG Lt's, x-pipe, borla cb, DR's and a honker intake. I've decided to go with the LG motorsport g5x4 cam and a textralia clutch, but am waiting to purchase the cam, in particular, until I've decided on heads. I'm looking to eventually dip into the 10's with this setup; my question is this:

With a h/c combo, would I be laying down bigger numbers/ quicker et's with a set of ported PRC 243 stage 1 ls6 heads, or a set of AFR 205 milled to 62cc? I've been told that with the PRC's I could go with a bigger duration/lift cam than if I went with the AFR's.. I've been impressed with the flow #'s on the AFR's, but it looks to me that the PRC's would have more lowend torque.. My buddy is telling me he'd give me his PRC heads for $600 bucks... I was just curious what you all had to think regarding these setup options.

 

Look into the Trick Flow 215 heads and have them milled. Give Ron @ Vengeance Racing a call.

 

In my opinion, the AFR's are a better head. Better low end response and the decks are thicker. When they port the 243's, the rocker stands can weaken. The AFR's have a better valve drop as well compared to the stock GM heads.

 

Thanks guys, anyone else?

 

Just keep a close watch on what your final CR will be after milling and
your choice of head gasket. For sure if you are planning on running just
pump gas.

 

I've been thinking of getting some AFR's but never seem to go on sale They seem to have good flow numbers

 

I don't think they ever really go on sale, but you might find a vendor willing to throw in some head gaskets or other parts to sweeten the deal.

 

Check out these threads:

http://forums.corvetteforum.com/show....php?t=1859936
http://forums.corvetteforum.com/show....php?t=1866372

 

The AFR's will be the better performing head, if your budget allows for them. Better port design, larger valves, and smaller chamber size = more compression.

If the PRC's aren't milled, and you use a stock thickness head gasket, you should be able to fit them without having to notch the pistons.
The AFR's may or may not fit w/o notching. There seems to be a lot of conflicting info out there about p/v clearances with AFR heads. Tony Mamo will likely tell you anything bigger than low 230s duration isn't gonna fit, but LG will tell you the X4 will clear with 59cc AFR 205s and a .040" gasket. Honestly, I can't tell you who's right, or what "it'll clear" really means to the people claiming it. Anyways, if you find they don't clear...be ready to spend more money to cut the pistons.

The X4 is a big cam (mid 240s duration), and with stock heads/stock gasket, you probably are only seeing about .050" clearance to the intake valve.
Most people will recommend a minimum of .080" clearance to the intake valve, and .100" clearance to the exhaust. When you get into custom heads, remember milling, bigger valves, thinner gasket, etc will further reduce that clearance. That's why I said the stg1 PRC's should fit if they aren't milled, since they use the stock dia valves, and if I recall, the valve seats may be sunk a little deeper too (for additional clearance).

I am running the X4 cam, with 59cc TEA stg 2 ported 5.3l heads with bigger valves and .040" head gaskets. This is about the limit for compression on 93 octane (I"m at 11.7 scr / 8.6 dcr) I also notched the pistons .100" deep to achieve adequate intake valve clearance. (Sorry, no dyno #s or track times yet). With 62 or 64cc heads...your compression definitely won't be too high. Not with that cam...


Personally, for what you want (1/4 mile - where hp is everything and lowend tq not so much a concern)...if money was no object, look into the small bore AFR225s, Trickflow 215s, or ETP 225s... mill them down to 59-61cc for best compression, and notch the pistons if needed. Add a ported FAST 90 setup, and expect a 500rwhp beast that will pull hard to nearly 7500rpm.

 

Ok guy's here's an update;

I talked with Tony Mamo and will be ordering a ported fast 90 with a ported ls2 tb. That'll put the following mods on the car
-Mamofied 90/90, LG Pro's, xpipe/borla cb, honker(may switch to vararam), U/D pulley, textralia, DR's..

I've been reading a lot of different threads discussing PTV/ flycutting pistons, etc.. To avoid some of these issues and attaining clearance I'm looking at this setup. G5X4, AFR 205's 61cc, and the stock head gasket rather than the cometic .040" Let me know what you all think about this combo.. and thanks guys for your responses, they've been more than helpful!

 

I'm also looking to the AFR's over the TFS's because of their increased valve drop. I've seen, heard, and read nothing but positive things concerning AFR and Tony Mamo as well .

 

I would talk to Tony about trading off the cam for an AFR 224/228 on a 114 for a thinner gasket. There are trade-offs that can be made in any setup and he can provide you some guidance on them. I have been working with him on my setup for several months. My parts will be here in a few weeks and then I have to stare at them until the weather breaks in April

 

Running milled heads and the G5X4 cam I can almost gaurantee you will need to fly cut your pistons. I can't find the specs on the g5x4 cam from LGMotorsports but the g5x2 specs are 232/240 .595/.610 112. I'm going to be running the 62cc Dart Pro 1 heads with a 228/231 .571/.573 112 cam and, according to another forum member, will just barely make the minimum recommended clearance of .080 intake and .100 exhaust...and this is with the stock thickness gasket .051. I'd like to use the .041 gasket to achieve 11:1 but if I have to fly cut the pistons I'll lose the gain from running the the thinner gasket.

 

You honestly think he's going to get into the 10s with a 224/228 cam?

If anything, for the OP's stated goals, he should be looking at the smallbore AFR 225s for that cam and application.


You have to understand that aftermarket heads are not all the same. You can't rely on just a chamber size to tell you how much clearance you'll have, or what will clear, as you have no idea how far up in the chamber those valveseats are placed.

As has been claimed by LG on LS1Tech, even 59cc AFR's have more valve drop (clearance) than than 100% stock GM heads.

Your Dart's on the other hand, start out with less valve drop than stock heads.

 

Yes, I realize that all heads aren't the same. However, AFRs start with a 66cc chamber so I just assumed that milling the heads .275" to achieve a 61cc would put the valves close enough to the piston to require fly-cutting the piston with a 240s/.620"s lift cam.

Valve drop...seems counter intuitive more valve drop = less clearance. Running 10s with a 224/228 cam is indeed very possible. Good set of heads, intake, headers, 3.73s (event 3.42s), 3600 stall (assuming an A4), sticky tires, and, of course, a 125hp shot of the juice and I guarantee your in the 10s...I plan to be anyway.

 

I thought Tony got pretty close with that setup, if not into the 10's.

 

With the AFR's, each .006" milled reduces the chamber size by 1cc. So to reduce the chamber by 5cc means milling them .030".
ok, I guess you don't know what valve drop means.

Valve drop is a measure from the valve at rest in it's seat, to the deck surface of the head. It is simply a measure of how far up in the chamber the valveseat is located.

Take a head with no springs in it, put it chamber side down on a table. Hold a valve up in it's seat. Then let it drop down until it hits the table. The distance the valve moved is known as valve drop.

More valve drop = the valve is higher up in the chamber, and therefor, starting it's travel further away from the piston, it will always have more p/v clearance than a head with less valve drop.

 

Between the AFR 205 and the TFS 215 which head has the most valve drop?

 

These are awesome heads and you will not be disappointed with them!

I've got them and they are great! I made with my H/C set-up 423 RWHP and 399 RWTQ!

See the sig below!

Thanks,Matt

 

Ah yes. I was calculating using .055 = 1cc rather than .0055 = 1cc...oops....thought it sounded too high