I am removing my heads to get them ported next week and was wondering if I will run into clearance issues if I had them milled too by .030?

The car is '08 A6 Z51 with a Comp Cam.

*** Update ***
Cam specs are NOW:
227/231 .613/.617 lift 115+3 LSA

 

should be fine. I have a 230/234 with a little more lift. My LSA might be wider, but the shop that designed the cam and installed it said there was plenty of room to mill the heads. Only reason they didn't was because of the CA gas.

 

Any idea what the LSA was? 115, 116 or higher?

 

No probelm with that. In a matter of fact Texas Speed recommended that package for me. ...same exactly cam spec. But I had the L92/L76......milled .20. Your LS3 should have more clearance anyway.

 

No, they won't say. But if your heads are coming off anyway, you might as well measure the clearance. That cam is pretty mild though.

 

Every once in a while a thread comes along that has such dangerous info in that it becomes nec to type some long winded info.....

In any install, the need to measure clearances is the responsibility of the installer. It is 100% rediculous to install a cam and rely on asking someone if "it fits". Why?

If you order a bunch of cams all with the same specs, you dont get a bunch of cams all with the same specs. When you order a 230/234 114+2, you may get a 230.8/233.4 113.7+2. In addition I have been present when Comp Cams sent one tuner a cam that had the intake and exhaust lobes reversed. It was checked on a cam doctor. This could result in a 230/234 114+2 being a 234/230 and you better believe that affects clearance.

To start with, a bunch of tuners have done tests to show what doesnt fit. When the Ls3?L92 heads came out, it was found that the huge intake valve didnt have much clearance. Texas speed posted their results of a .140" valve drop. If you mill, thats more like .110 valve drop. Now if someone tells you "it fits", and sells you a cam in the 230's, beware. Livernois Motorsports actively participated in a test of these heads in a GM High Performance Mag test where it was found that a 232 on a 112 without milling was near the limit of what fits.

Each Intake duration degree is about .006" lost and so is a degree on the LSA. Milling .030" kind of eats away at the clearance. For the record: A 230 114+2 with .030" is not going to yeild .080" P/V clearance, you need to flycut.

Keep in mind that the stock LS3 valves are welded 3 piece hollow stems. If they hit, they cant be used. It takes a missed shift overrev to need a healthy repair.

What you have to walk away from here are the following:

1-Buying a cam where the specs are secret: tell them to keep it.
2-Do not think thsat you can check clearance sitting at a desk with a calculator. Cams can be ground wrong. You have to mechanically check it or at the very least, verify the cam specs (cam doc).
3-aftermarket valves have thicker margins and this takes away clearance by another .030".
4-Dont ever take someone's word for what cams fit and what ones dont. One bigger cam that sells a lot was factually clayed and also tested with test springs and it has .047" clearance on the intake side with no milling or thinner gaskets. Its a mid 230's intake duration. You need .080" minimum.
5-Spring wear out and become more inclined to float a valve over time. Take heed.

For those that dont know a margin:


My $.02 : Use thinner gaskets before you mill. Gaskets increase compression by an additional 30%. Milling also hurts flow so its a last resort. If you use a big cam and want optimum compression read this:

http://forums.corvetteforum.com/c6-t...mpression.html

 

That cam is way too small to expect anything from porting these heads. The LS3 starts off life as a 260cc runner and thats too big already unless its a solid roller cam. The LS3 head did not develope from the LS7 program, it was the LS7 prototype. It was well known that the 260cc runner was way too big and it was downsized in the final LS7 head. Its around 240cc's on the LS7 and that is being used on the 427 displacement. Porting usually takes the LS3 heads to 275cc's. One drive on a trick flow head car will show you the throttle response that can be had.

Ported LS3 heads get you 20hp or so on a stroker with a huge cam. You will gain about 6rwhp up top and lose 10rwtq through the midband if you port. Bumping compression is likely the best move on its own. I'd get .040" gaskets and bolt them right back on.

A better plan is to sell you LS3 top end for 1500 and buy the Trick Flow 235 (not a typo, the 235 fits the Ls3). Hinson Super Cars used the TF235 on a stroker LS3 and hit 593rwhp and 611rwtq.

You will gain 30+rwhp and big TQ down low. The TF235 also allows for all the compression you need without flycutting because it uses a 13.5 degree design. I'll bet you will see close to 500rwhp with a 224 cam and 11.4:1 compression.

 

Once you pick the intake and ex duration, the LSA and advance are picked to determine where the cam is going to peak. A 230 114+2 peaks at 6300. Wider LSA's delay the intake valve close and you lose low end in favor of a higher HP peak. Since the intake manifolds we use force the peak at a set RPM, this isnt going to be synergistic. LSAs dont get picked by what you like. Advancing lowers the peak. A 115+3 is about 6300. A 230/234 115+3 would drive really nice. I use a 230/230 115+1 in A6 cars. Bigger splits add power past the HP peak but introduce big overlap.

Advancing lessens clearance, wider LSAs increase it. Increasing displacement peaks HP sooner with a given cam. A 230 114+2 in a 416 stroker would peak at 5900.

 

The latest --Hot Rod---mag compares cyl heads----the CNC"d 243 was almost as good as your favorite Trick Flows !!?? What's with that ??

 

Thanks for your input Spin, great information there, and OUCH, lol. I was really hoping porting the heads would get something more horsepower wise with the current cam in the car. Any recommendations on the lift for the cams you are talking about?

 

Is there normally enough clearance to install the .040 head gasket on an LS3 with one of your cams (230/234)? If so how much TQ and HP would you gain, and where?

 

Listen to spinmonster. I would love to see someone ditch the l92 head and put on trick flow 235's. The 225 would be even better witht the smaller exhaust port. I think a 225 milled to 62cc would take you up to around 11:7:1 compression and still give plenty of ptv. By now everyone has read the pat g afr 230 thread and while the results are impressive I don't think the 230 is any better than a trick flow 225. His afr heads had several one off tweeks and were not the same head that the average joe can buy, unless you want spend 3600 bucks on heads. I say the trick flow 225 is better because of its valve ange and increased ptv clearence.

 

Thanks all you guys for the comments. Here is something to muddy the waters, kinda, and I'm sure you can't trust these programs too much but here it is. Downloaded a program that takes in all the motor info, including induction and cylinder heads "Port Flow" data. I selected my current cam and changed the "Port Flow" table from stock to the ones reported from the CNC porting and it went from 403 HP @ 6000/403 TQ @ 3500 to 424 HP @ 6500/ 399 TQ @ 3500. This program assumes completely stock other than the cam and that it is a Manual tranny. It seems right on for the stock part as my car dynoed at 420/398 with the cam, headers, CAI and tune. Again, take it for what it is worth.

 

I wish I was smart enough to understand all this!

 

Back on this topic again thinking about pulling the trigger, except no milling just porting from a local guy. Here are the flow numbers:

Flow Numbers

Intake Exhaust
.100 80.9 60.3
.200 159.9 129.9
.300 237.1 180.1
.400 291.2 226.0
.500 330.8 255.9
.600 365.9 268.1
.700 376.6 272.1

So let the comments fly..... Hope to get some good power from 4000+ RPM's

 

What changes were made to the port volume to achieve those flow numbers?

 

I don't know yet, just know he does full cnc porting and valve job, just talked to him briefly yesterday and he gave me this flow number sheet. I am looking for some opinions/feedback if I am going to get some good gains.

 

If I were you..I'd wait for another month and see what the new Trickflow ls3 heads will do. The new heads are suppose to outperform anything presently available. They decreased the intake down in size and that picked up the velocity. Just my two cents...Mike

 

I have been considering that too, just being impatient and and there is a big difference in price too of course!

 

ttt