Choosing heads - help.

[redsap05]

The ls3 head is good but its not the gift from god eveyone cracks it up to be. If you simply mill the head the car gains 20-25 rwhp. That just goes to show you that a 70cc head is not Ideal for a 6.2 . Yea you can do porting to them and people have made good numbers. When I get my ls3 I am going to take the road less traveled with it. Iam going to put cathedral heads on it and ditch the l92/ls3 heads. Theres a huge thread on ls1tech that talks about it, patrick g ditched his l92 heads an ls3 intake in favor of afr 230 heads and a fast 102 intake. He gained like 120rwhp in a automatic! My recomendation is a trick flow 225 milled to 62 cc, that alone will take you a full point in compress from 10:7:1 to 11:7:1 and still have plenty of ptv clearance, A g6x3 cam and fast 102, The same comb recently made 530 rwhp on a 6.0 Ls2! I can only susspect that a 6.2 ls3 will do even better.

[Stay Marine]

Wondering the same thing. For conservative gains, check out Scoggy Dicken Chevy. They do similar headwork as offered by GMPP. They have done several of these with no adverse reports back to date--apparently. On a stock LS3, the new heads netted 25hp to the wheels. The Hot Rod article shows several options. SD will do just the headwork for $500. Beefed up valvetrain adds more. The summary above provides great insight...bottom line, talk to your tuner (or a pro) about matching the cam to the improved flow rates....the exhaust is the greatest factor restricting the LS3 HP. With improved porting, you don't have to go to a radical cam to notice significant gains.

[speedster]

Originally Posted by nuptualnemesis

This is probably more than you asked for but here goes.

Higher flow numbers move more air and fuel. Larger motors need higher numbers to make power but an LS3 may not. This is a small block. You can hog out a port and flow high numbers but loose horsepower because you loose velocity and air speed which make horsepower. Many porters now try to smooth out exhaust air flow rather than max out exhaust CFM flow.

Mid lift flow is more important than maximum flow because average horsepower is more important than maximum horsepower. Low rate flow is even more important on a street car that will seldom see over 4000 rpm any way. High lift flow rates are more important for high rpm power. Flow rates over .6 lift are not relevant to a cam that only has .610 or .620 lift. The valve will never open to .7 or .8 lift.

I have a 231/247 duration .617/.624 lift 113 LSA cam. I think this cam is too big and plan on a 231/236 in the near future with a 114 LSA. The duration spread was too big before and now my heads flow percentage is better so less exhaust duration is needed. A little wider LSA will spread the horsepower over a wider range and make the cam less peaky and more streetable.

I installed TEA ported heads (L92's, this is the early LS3 head and almost identical) on my LS3 that were rated at 355 cfm intake at .600 and 264 cfm exhaust at .600 and LOST 15 HP on the dyno. Went to the track to verify and ran slower. Pulled the heads and flowed them and they flowed 344 intake and 220 exhaust at .600. Way too skewed to make power. Flow within 80% of intake to exhaust is usually best. So much for advertised flow numbers.

I worked with a local head porter with a flow bench and we got my stock heads Intake flow at .600 up from 306 to 320 and exhaust up from 210 to 242. The exhaust needs more work for a better intake to exhaust ratio so that you don't have to spread the duration numbers so far apart on the cam. You do not want to loose velocity on the intake by increasing flow. Many heads are rated by the size of the intake port. For example AFR has a 185, 205 and 225 head. This is the cc size of the intake port. A bigger motor needs a larger head for more flow. A smaller motor needs a smaller head. The bigger head may make more maximum horsepower with a loss of average horsepower or it may make less horsepower because the smaller motor can not keep up with the flow.

A lot of old school porting tricks such as air foiling the intake and exhaust guides bosses in the bowl don't help LS3 heads. These heads are very efficient out of the box. They do benefit from combustion chamber reshaping and short side radius smoothing on the exhaust. GM was more concerned with a clean burn than max power. Taking the bump out of the quench area on the spark plug side and laying it back at a slight angle allows the piston to push the air into the exhaust more efficiently. Almost all race head combustion chambers are straight across and slightly laid back on the header side.

I picked up the 15HP I lost plus 10HP more at peak and 12 to 15HP more in midrange. Added 2mph on top end at the track. But I also re-geared so top end could have been affected by the gear change.

The only real test for better heads is a dyno or the track on a similar size motor. You can't trust flow ratings to be accurate or better for your combination. I would not get an out of the box CNC job. Some after market heads MAY be better but you have to look at the size motor and intake (fast = $900.00) and throttle body ($300.00- $500.00). A stroker motor or blower motor needs different heads than a stock motor and cam.

The recent series (3, I believe) of Hot Rod magazine tests did not test a stock LS3 size motor. The cubic inches were less for earlier motors or more for stroker motors. The Mast Black Label redesigned head is very expensive and a blower or stroker is needed to take advantage of it.

You can save money on an intake by getting a VMax ported intake. The VMax ported throttle body is more effective with a Vararam or New Era straight shot intake than a curved tube intake. I picked up 15HP with the VMax ported intake and throttle body ($150.00 each). Pete at VMax told me the ported throttle body would increase response and drive ability more than increase horsepower and it did both. I did not dyno the intake and throttle body separately.

I would recommend sending your stock heads to Darren Morgan. He is a top national porter and involved with Engine Masters every year. He has offered to port, mill, valve job and assemble, with your new springs, retainers, etc., for $599.00 on this thread http://www.camaro5.com/forums/showth...t=42255&page=5. This thread also has a lot of good information about head porting.

This is a super price and a good valve job is as important as air flow. Racing valve jobs have 3 to 5 angles and the angle degree and width is all important. Milling helps increase compression which is good for a cam but reduces deck thickness which is bad for blower or nitrous. Also be careful with cams over .600 lift because of valve to piston clearance with milling. Some head shops charge $200 to $300 just to mill, valve job and assemble heads. You should upgrade the stock roller rocker trunion bearings with better springs but roller rockers are not necessary. The pro's and con's of this goes on and on. Dual springs are better with a cam and power adder. I also think patriot springs, even gold springs, are not near as good a comp cam tool steel. The tool steel retainers are cheaper than titanium but lighter than standard retainers. I shift at 7,000 rpm.

Good information here ^^.

As far as your request for the proper heads/cam is concerned you need to assess what your intentions are for now and possible future upgrades.
Questions like:
Driving venue - street, road course, autocross, drag strip, measured mile (what % of each)
RPM range - cruise rpm, "max" rpm and rpm range - higher vs. lower; e.g. low end torque versus high end HP
Cam sound/overlap/duration - do you want a smooth stock "electric" idle, do you have any problem with a "lumpy" idle.
How often do you want to maintain the cam/lifters/springs? - Never, occasionally, often?
What other items are you planning - matched components work best.

Anyway for an answer to your original question - most people prefer the smallest ports that generate the most flow under the curve and target the .300 - .500 lift range.

There are many great sources for cylinder head information. Darrin above sounds like a great source for you. You also may want to give Tony Mamo out at AFR a call. He is a wealth of knowledge on this subject too.

Enjoy !