mike m

iTrader: (6)

Give LG motorsports a call or vette doctors. Both shops buy and install Absolute Speed heads. It seems people post mostly bad results with poor combos with any head be it tea, patriot or AS heads. I have seen personally many dyno sheets from vette doctors dyno over 440 with cams in the 228-230 range on vettes.

LS1 Power Plant

iTrader: (7)

I made okay numbers. 460 RWHP 415 RWTQ NA and 610 RWHP 615 RWTQ on the juice. The NA numbers were on a rich/24 degrees timing nitrous tune through the full exhaust. There is more left, maybe 475 leaning it out and bumping timing up.

mike m

iTrader: (6)

Those are some real good #'s. esecially for an NOS tune.

jrp

iTrader: (16)

what was the rest of the setup? very nice numbers

rare bird

Is there anyone else out there who has actually checked (cc'ed) there own runner volume, no matter who ported your heads (not relying on head porter claims) who has some real world dyno numbers (or track times). What are the head runner volumes, who is the shop that ported your heads and what components are on or in your motor. Hopfully we can compile enough info to help ourselves and fellow LS1 enthusiasts.

offaxis

iTrader: (19)

Maby this car
https://ls1tech.com/forums/dynamometer-results-comparisons/195453-got-tuned-up-today.html

Also a friend of mine thats not on the boards made 438 with these heads with a 10bolt and 410 gears

CHRISPY

On my 360 setup I had ARE ported 5.3L heads, 228cc intake runners and 230/230 112LSA cam. Ran 11.154 @ 123.XXmph 1.50 sixty powershifting on slicks with 4.11 gears.

Current combo 3550 pounds.
Heads have 236cc intake runners (LS6 head) 385 cubes and 236/240 cam. 11.10@125.05mph in it through CATS on a slick at ~3600 pounds.

Kevin'

The question isnt have these heads made good power. Any engine combo will make the appropriate power if the combo is properly matched to the engine-car's intent.

The problem arises when a hot rodder attempts to install race heads and a race cam with a street engine running street compressions on pump gas. The result is a confused engine: the engine doesnt know if it is a street engine or a race engine. Displacement and RPM range plays alot in what you can or cant get away with regarding port volumes.

If you are going to run your LS1 with a stock displacement, stock Static CR, and install these 236cc heads; then you can bet your peak Tq wont enter the picture until well after 4000+rpms and your peak HP wont surface until well after 6500-7000+ rpms.

If you build this kind of an engine and you plan on shifting gears in the 5500-6000 rpm range then you have missed the peak hp range of your engine and you have mismatched the components to the intent (H/O Street Performance...not Dedicated Racer) of the engine-car combo.

When this conversation comes up I always like to throw out this point:

1) You can over build your engine and it will rev to 5000 rpms
2) You can build your engine just right and it will rev to 5000 rpms
3) You can under build your engine and it too will rev to 5000 rpms

Q: So of the three possibilities-which engine build is correct for your engine-car combo?

If you are going to run the stock displacement with the 236cc heads, then you really should consider Nitrous, Turbocharging, or Supercharging your engine as the extra port volume is perfect for post nitrous or post boost: this requires altering the stock compression ratios. Still the 236 is a little too large for a street Nitrous, Turbo, or Supercharged engine.

You would make better power with a street Nitrous, street Turbo, or Street Supercharged engine with the 346 displacement if you chose cylinder heads in the 200-215cc range. To state the obvious...if you are going to utilize a power adder then you will need some platform that allows for engine timing retard and fuel enrichment.

As far as a normally aspirated engine is concerned - these heads are too large for street driving if you keep the stock displacement and stock compression ratios.

Keep in mind we have not even touched on gearing nor the weight of the car. So far we are only dealing in the efficiencies of the engine regarding a specific rpm range.

Kevin,

Bowtieman4life

iTrader: (1)

Yeah! What he said.

Ragtop 99

iTrader: (7)

If all head porters were equal, then the cc relationship would be highly correlated with results. However, experience in the LS1 market has shown that poorly ported low cc heads exist (generally, not for long ) as do larger cc ported heads that have performed well. Point being that when it comes to buying LS1 heads, port volume has not been a great indicator of performance so far. It appears that the new AFRs will live up to the theory, but so far results are only back from sponsored test mules. It is also worth noting that the AFRs will achieve it after significant changes to the head, which are beyond a typical port and polish.

As far as torque goes, an LS1 with stock heads and cam has a torque peak over 4000. With an LS6 intake, most set-ups with a cam under 230* make peak torque in the mid-4000s with some of the monster cams peaking around 4800. Given the shape of our intakes, to use heads designed for a torque peak under 4000 rpm seems like it would be a mistake. On a stock bottom end, most people are willing to rev to 6400 - 6600 so a HP peak of 6200 is no problem.

CHRISPY

The AFR's have significant changes compared to the stock LSX heads including taller runners.

Also the AFR 225 should SIGNIFICANTLY outperform the 205s on a stock cubed motor with a cam that is specc'd to peak in the 6200-6600rpm range.

Something we also need to factor is intake flow capabilities. The LS6 intake is only flowing about 280cfm. Also does anyone have port volume information on the Ls6 intake?

I think you can have a very high performing (Both RWTQ and RWHP) stock cube motor with a 235cc intake port provided proper parts selection is done.

Kevin'

Based on what actual hard substantiated facts are the 236cc heads creating more power compared to brand [x], and at what rpm are the peak tq/hp being made? In order for us to get anything out of this thread we all must compare appes to apples and oranges to oranges.

I guess this means we would have to define the test parameters before we can reach a conclusion of any kind. Such as a test specifically for cylinder heads that fall into the engine-car combo in an H/O Street category, and then a test for cylinder heads that fall in the Weekend Warrior engine-car category. Then we would have something conclusive to make an educated purchase.

What tests have you seen where a side by side test has been performed regarding head testing on an actual running engine on a dyno? The only LS1 tests I've seen involve intake swaps and cam swaps - I've not seen any Cyl.Head swap testing to an LS1...as of yet (Hopefully the performance mags will pick up on this void).

Actual Port Volume cc does make a difference as well as volumetric efficiency - granted the LS1 is a unique engine in a class all its own. GM out did themselves and suprised the entire world with another Push Rod engine that kicks butt, but - the point I am making is this: peak power in a specific rpm range depends on matching Dynamic to Static CR relationship with the Port Volume, based on the Port flow relationship to the cam profile, within a specific level of performance desired: at a specific rpm. This means matching port pressures to cylinder pressures to engine rpm.

That is a good point about the stock LS1 not making its peak torque till around 4000 rpms!

If people are willing to spin their engines to the 6000-6600 rpm range, yee-haw, I say go for it. Yet if they are utilizing a port volume that is too large whereby that cam profile and cylinder head port volume dictate a peak hp in the 7000+ range (due to mismatched parts...or a misunderstanding of how to match the Dynamic to Static CR, Cam Profile, Cylinder Head Port Volume, then your engine is not running at peak performance. It may run well, but it is not running at maximum efficiency. Most will install a 285 or 290 cam with the larger heads...this typically dictates a peak 7000+ peak hp rpm.

To determine maximum efficiency we rally need more than just Tq/Hp numbers. We need Cylinder Pressures, Volumetric Efficiency, and Air-Fuel Ratio numbers.

The 236 heads on a normally aspirated stock 346 displacement engine requires 12:0:1+ plus Static CR to maximize the peak potential of those heads in a 3600 lbs car including driver.

Port Volume of a cylinder head has everything to do with peak rpms. If you dont understand this concept then you dont understand airflow velocity....and I know you understand airflow velocity.

I thought this thread's theme was about a few folks who purchased the 236cc head which hurt their performance and that one or two members said they thought they were getting a much smaller cc port(?) to begin with: this is the point I am making - most folks dont know they have to spin their engines to the 7000+ rpms to obtain peak hp: most folks just want to have fun never understanding there is more to building a performance engine than simply slapping on a set of heads.

If you dont mind rev'g your engine to 7000+ and you have a budget whereby you can repair things when they break, then I say go for it: just dont expect real performance under 4000 rpms.

As long as this lack of power under 4000rpms is disclosed to the consumer then all is well. It looks, according to this thread, that this information is not being disclosed to the consumer - so all is not well.

Is that the fault of the head porter...not always. We as consumers must be more educated. When we tell a speed shop what we want - we better understand what we are saying: because most speed shops are long on reputation and will give you what you ask for.

I still say, if you have a pair of the 236 heads then you should utilize Nitrous. The extra volume is perfect for the stuff.

If you are not going to do the Nitrous, Turbo, or Supercharger then the 236 heads are too large for a street engine on pump gas unless peak 7000+ rpm is your goal while anything below 4000+ rpms are inconsiquential: AND - you know this going into the purchase of these heads, then all is well.

Kevin'

rare bird

Has anyone measured the volume of their ported int. & ext. runners lately? They may not be the cc's you were told!

CHRISPY

You make several good points there but also remember that 12:1 comp is doable on pump gas (93-94 octane) with the right timing and coolant temps with an LS1/LS6 intake. Also cam design will play a huge factor in peak RWHP/RWTQ with heads that are in the 235cc range.

Also the LS1 and to a lesser extent LS6 intake choke off head flow and actually make the motor behave like it has slightly less compression due to the restriction.

MYBLKSS

iTrader: (1)

Just wondering if their were any more delvelopments? After already being robbed by JPR on a set of heads, I am in the process of looking for a new set and found this thread to be very helpful. I just really wish people were more honest and this process was more straight forward.

KGSloan

i didn't get my intake and exhaust runners cc'd. i did flow and cc the chambers before they went on the new motor. they flowed right on, 311cfm @.600". however, the compression was about a half point lower than what i was told. it was actually around 10.5:1 instead of the 11:1 i was told. i fixed that though

btw, the new motor made 440rwhp and 390rwtq with these heads and a g5x3 camshaft. also made 300rwtq at 3000rpms. this was with less than 100 miles on the shortblock. so, the heads are still performing fine.

LS1derfull

I think Kevin is correct in theory on all of this discussed subject(Who do you work for? You are very sharp) But i will say that LS1 is a different animal in respect to the peak power rpm. Regardless of cam duration or port volume, peak power is made between 6000 and 6600. My reflection on this is that its total runner length that is consistent between most LS1's and it must play a role in this. "Big cams" trade off torque at 2k to 3.5k, but fatten torque dramatically above this range. Min. cruise rpm is moved up with larger cams, but thats about the only downside to them, when big N/A power is desired.
I care most about track performance, so give me 250cc ports if they give me 3mph more than 225cc heads. When any decent running LS1 has 350+ ft. lbs above say 2500rpms, how can you lose gaining extra power of bigger cam/head and still shift below 7k?

Cary@Perf-Induction

iTrader: (1)

rpm, peak torque and horsepower have more to do with runner length and average cross sectional area than it does with just intake port volume. The only problem is that everyone will take a different side to what the next person thinks. Out of all the different ls1 and ls6 style ports that we have done, there has been absoluely no benefit to a small (220cc) port over a 235 cc port. the only difference was on an engine dyno where the 2000-3000 numbers were a little limp, but ran like hell over 3000, which is where most full throttle passes happen. Remenber that the intake port in most manifolds are smaller than most ported heads, so you will still have high airspeed through the manifold into the port of the head. which will pack the port even after the valve is closed. I feel the larger port (235) is just fine, even on a bone stock ls1. I've seen it with my own eyes. It doesn't take a blower or nitrous to make it work either. A lot of you guys out there have much larger ports than you would even think, if you knew exactly what they were, you probably would have been sceptical to even run them.

J-Rod

Good discussion thus far.

A couple of things. We have a set of AS heads on Tommy's car it made 503/455 on a stock bottom end 346 w a G5X3 & 4.10 gears. Below are the numbers Jay gave me the numbers on the heads. According to him they are 225CC.

My understanding is some of his newer heads are slighly bigger ~235CC. Jay in the past only basically did work in the bowl, and did basically nothing in the runner. I think he has changed that slightly along with going to CNC, and thus has some higher flow numbers, but also has a bit more runner volume. I have included our raw numbers, plus the numbers with the intake in place.


Intake No intake LS6 FAST
.050 - - -
.100 69 - -
.150 - -
.200 155 152 154
.250 - - -
.300 212 204 208
.350 - - -
.400 259 243 251
.450 280 260 269
.500 301 272 280
.525 - - -
.550 313 281 290
.575 - - -
.600 323 293 299
.625
.650
.700

Exhaust
.050 - - -
.100 - - -
.150 - - -
.200 117 117 117
.250 - - -
.300 160 160 160
.350 - - -
.400 206 206 206
.450 213 213 213
.500 222 222 222
.525 - - -
.550 228 228 228
.575 - - -
.600 231 231 231
.625 - - -
.650 - - -
.700 - - -



As I said, some real good points in this thread thus far.

Although many of you may disagree, if you go back and read the cam thread we actually touched on this. Big ports with lazy airflow often need smaller faster lobes to get the velocity required to make the port work. I think this one of the reasons LPE heads work so well with the LPE packages is that they have a bigger port and work well with LPE's smaller cam designs.

Now, on the subject of port design and port volume. All things being equal (which they never are) if both ports have the same flow and one has a smaller volume, you'd normally pick the smaller port to keep up velocity.

One thing to keep in mind here is that you can trick a flow bench and take material out of certain parts of the head which will show big flow numbers but not lead to making any power. There are other ways to cheat on a bench too. But I digress...

Taking flow numbers or dyno numbers from one shop to another is really pointless as the variance between can often be big. In many cases with proper calibration it can be close, but too often it isn't. You best bet if you want to compare heads is to not only flow them on the same bench, but also test them on the same car/combo, or ideally same engine dyno. I know most folks don't have the time or resources to do this, but its realy the only way to make a really fair assessment.

I'm glad to see someone else talking about DCR. We have touched on that in some other threads, yet folks seem to still be totally wrapped up in static compression perhaps we can get a thread going on that to get folks to start thinking dynamically rather than statically.

Mike K.

so more and more people are cc'ing and getting 235 + CC's... hmm who woulda figured??? There are currently two things that sell heads

1. small runner
2. big flow #s

Without these two things a head is not going to sell which is why every head is advertised to have both a small runner and big flow #s.

What is sad is that when heads are cc'd they often come out alot different than the advertised specs. What we need which is impossible in any business community is some honesty. If we had that people wouldn't be going to the dyno scratching there heads wondering why they put out so much less hp.

Lesson to be learned if you dont wanna get f*cked like I did. CC and flow your heads before you put them on the car. There is only 1 real way to know and that is to check.