If I still had the pic of my graph overlayed with a similar setup on a car with Trickflow 215 heads id post it up but I dont. I made right at 35 more lbft of torque at 3k with my $350 stock L92 heads and stock LS3 intake than that car did with $2000+ TFS 215 cnc heads and a fast 102 setup...

 

Look, before this becomes a huge pissing contest, im not trying to say L92 heads are better than cathedral heads...im simply showing that rectangle port heads can make good low end even without a "perfect specd" cam for them. 350lbft at 3k on a stock 6.0L is pretty damn good torque for stock heads...and I dont think anyone can argue that it sucks. This is just another case of ls1tech BS run rampant...one person posts up that something sucks and bandwagon pours the cold to it. Im just trying to help the OP see all angles factually...non-biased.

 

It's not a 346ci LS1. Someone even posted up my build thread titled "376ci Iron Block"...does that make it more realistic? Will you believe the facts now rather than accuse people of dishonest work?

 

And thats my current problem right now.

 

I didnt accuse anyone of dishonest work...its done every day...most every shop that doesnt have a dynojet but gives out "dynojet equivalent numbers" are doing this.

The fact that you are 376ci makes it more believable, however im still skeptical about the ls1 intake and that much torque. Sorry, ive just seen too many in person blow goats and kill horsepower and torque on cars. Here locally, my tuner, and good friend, has a dynojet that is said to read lower than most dynojets. I personally think it reads accurately compared to higher reading "friendlier" dynos. There is a Superflow dyno 2 hours away that I have been on before and it reads higher than my tuners dynojet normally, then they give out their "dynojet corrected numbers" and your talking 40-50 hp difference. Im very skeptical of shops and dynos. My tuner is also a hay and cattle farmer who's garage and dyno is in the middle of the hay farm and he makes his living tuning and farming. He'll tell you "it is what it is" and let the numbers break your heart if they do, or make you happy. thats why I contend all this L92/LS3 heads dont make low end power or pull up top bullshit, b/c I see otherwise on a weekly basis as I loaf and help work at the garage on my off days. Special cam specs arent needed, anything that works for cathedral ports works for rectangle ports. See it every week...and I did it my self... The G5X3 cam I run was spec'd long before rectangle port heads came out. As far as them not pulling up top, thats a load of ****. My car runs damn good. Actually better than my old Z28 that was cnc heads, fast 90/90, and TREXv2.

 

Just playing devil's advocate here.....I'll post a dyno graph just for reference since I know it ruffles ol' Bozz Hawg's feathers(had to jab you there buddy ), but it's to prove a valid point IMO.

6.0 LQ9 bottom end, LY6 heads, LY6 intake, 230/238 112+2 cam, 1x7/8" headers, 3" true duals, no a/c and an U/D pulley.



That said, on a 4" bore or smaller I prefer a cathedral port. On a 4.030" bore I still prefer a cathedral, but I will use a small bore square port head as well if that's what the customer wants.

The whole "square port heads don't make velocity" is annoying and I understand Bozz Hawg's frustration with it. To determine velocity, you have a given amount of CFM at a given amount of lift for a given valve diameter. That said, not all square port heads are created or ported equally.

Question for you guys that keep talking about velocity...

If you have a 2.04" valve in a cathedral port head that flows 320cfm at .600" valve lift versus a 2.16" valve in a square port head that flows 370cfm...which has more velocity?

 

I always vote cathedral for bores smaller than 4.030 as well.

now if you want to spend a little more coin and go for some small bore ls3 heads that changes the equation.

 

At 85% valve throat area
Cathedral - 276 ft/sec
Square - 285 ft/sec

 

The valve shrouding is the issue I have... Second being how freaking picky they are on cam selection.

 

valve shrouding, get the small bore sl3 heads with smaller valves, OR get the small bores with the different valve angle and locations, problem solved.

 

OR! Go cathedral. LOL

 

absolutely, however I will say this:

when I was talking to Pat G (and others as well) about heads for my 408 I was recommended to go with the PRC 260cc small bore ls3 heads over the trickflow 235's. Granted both those heads are over $2400, but they are both way better than a factory ls3 head with even larger runners.

 

I use 91% for my calculations, but it would still have the square port head on top.

I got 118cfm/sq" of throat area for the cathedral and 121 cfm/sq" of throat area for the square port head.

Not many realize that a good square port head that doesn't have some massive 2.25" intake valve has higher efficiency, and more airspeed in the throat than a comparable cathedral port head.

Where these heads get mucked up is when they're put on the wrong short block with too little bore diameter, and cam timing.

 

Flow numbers, average velocities, discharge coefficients, and whatever else you want to extrapolate from the flowbench are one thing, but 80ft-lbs of torque is another. Again, my point is the cathedral port heads tend to make better overall power across a broader RPM range, which in my opinion, is king in a streetcar.

 

I think you extrapolating data from a car with a messed up clutch is foolhardy.

Your beating your chest about velocity and cathedral port heads have more, then I disprove that myth and you're saying it's not relevant?

 

Jst figured I would post up, I made peak power @6,500 with my rectangle port setup. The "porting" on my ls3 intake consists of cutting out the bridges only. This is a great read and lemons I am going to pm you as I have done questions for you!

My dyno graph and thread https://ls1tech.com/forums/dynamomet...454-425-a.html

 

I'd be interested in hearing your opinion on a cam for a stock bore LS1 running something like the BSP small bore LS3 heads in a light car (2800 lbs) with a lower of gear (3.73-4.10) and a T56.

 

What intake manifold?

 

What's the velocity at .300" and .400" if the cathedral head has a 2.08" valve and the square port head has a 2.16" valve, and they both flow the same amount of air?

Which head would then make more power on most combinations when using a stock style, long runner intake?

 

233@.300" & 293@.400" respectively for the square ports in this equation. 76.89cfm/sq"@.300" & 96.69cfm/sq"@.400".

TEA TFS 235 with a 2.08" has 235@.300" & 293@.400".

Square port flows more everywhere else after .550" by a small margin.

I just knew you'd come rain on my parade LOL! Notice my comment though about cathedral port on a bore smaller than 4.030" though. I still believe in that ol' tall lanky port trust me.

Not all square ports flow like this but neither do most cathedral port heads flow what tea tfs heads flow either. I think they're both great choices when used within their intended purposes.