L92 600 Crank HP

[Dave B]

300-291 .
Sorry I have new phone and was using speak into feature.

[Dave B]

She had 1-7/8 headers on dyno.
I made her 1-3/4 with 7 deg divergent x3" collector and that picked up her 60 ft from 1.47 to 1.41 with no other changes.
Can't port heads so I epoxy them about 1/2 shut and pick up the airspeed.
I put longer ratio rockers on 4 outer cylinder to help the piss poor intake dist. This all raised rpm in the engine and she now running in 6.40s and gained 6 mph. I also got rid of that cam like you stated that has 17 degs of overlap.
But again if you want 600 hp you better work on above 6500 rpm not below.

[Dave B]

Op on the headers for what you are doing I would look at 1-5/8 to 1-3/4 step header. Isn't a 550 hp sb on the planet that needs 1-7/8 headers or 2"

[Bill Chase]

Those intakes have horrible distribution and runner sizing and taper. You will need someone that really understands intake manifold porting if you want to get it straightened out. Your 4 corner runners will look waaaayyyyy different than 4 center. If you don't get after your setup I'm going to say 540 - 555 hp will be allot more of a reasonable expectation.

I wasn’t aware of the bad rep the dual planes had. I’ve been running them on all my street SBC/BBC setups for years. I always chose to give up top end hp for more tq and hp earlier down low where a street car lives most of its life.

The original sbc/BBC were designed with Siamese port layout, and enjoyed 50 years of development/testing with dual plane intake manifolds. It's likely that the 1970 lt1 high rise dual plane enjoyed a year of factory development, the aftermarket had most of the hard work done for them. The ls designed from a clean sheet, symmetrical port layout. Zero factory development with dual plane intake manifolds. And any aftermarket dual plane available at best got 6-8 weeks of testing and research, most of that centered around core box, mold development for maximum profit per part. If you take a look at most of the huge leaps in performance over the years, it usually follows OEM. And has gotten worse in recent years. Companies devote less and less resources to testing and research, more on advertising. The big money for LS stuff is centered around EFI use. Plan on paying a professional a good deal of money if you want the carbureted dual plane to work on your LS engine.

[Dave B]

Exactly Bill
Ls l92 is barely 400 hp from factory. It takes serious changes to make 500 hp. 600 takes some serious changes!!! We worked hard on low tension ,thinner ring package. We worked windage area hard. Those heads flow decent air if you work with above 6500 rpm. You want to make better average power across the board imo you better get rid of some area and make better radius and shape improvements.

[MD383]

Op on the headers for what you are doing I would look at 1-5/8 to 1-3/4 step header. Isn't a 550 hp sb on the planet that needs 1-7/8 headers or 2"

I have an aftermarket front end and the only headers that are supposed to fit without having to make a new set from scratch are 1 3/4”.

[Walter R. Malik]

I have an LQ4 with cnc ported #821 heads, 387 cid, (4.020" x 3.812"), with a much larger cam, (257/266@.050" - .730"/.710" valve lift), which dyno'ed at 687 horsepower using 1 7/8" headers and a 2 plane intake manifold ... A Holley 2-plane, 300-133 , dual-quad intake with 2 Edelbrock 750 carbs.
With a bit smaller cam & carbs, I believe this would be great on the street and probably be well over the 600 horsepower mark.

With 8 separate O2 sensors in the headers, the distribution was not bad.

[MD383]

I have an LQ4 with cnc ported #821 heads, 387 cid, (4.020" x 3.812"), with a much larger cam, (257/266@.050" - .730"/.710" valve lift), which dyno'ed at 687 horsepower using 1 7/8" headers and a 2 plane intake manifold ... A Holley 2-plane, 300-133 , dual-quad intake with 2 Edelbrock 750 carbs.
With a bit smaller cam & carbs, I believe this would be great on the street and probably be well over the 600 horsepower mark.

With 8 separate O2 sensors in the headers, the distribution was not bad.

Solid roller I’m assuming. Impressive, especially with the dual carb dual plane intake! That’s a big cam. If I get a stroker kit then that’ll help. I don’t want to over cam this thing and make it sluggish down low but I need to make the target.

[Bill Chase]

Exactly Bill
Ls l92 is barely 400 hp from factory. It takes serious changes to make 500 hp. 600 takes some serious changes!!! We worked hard on low tension ,thinner ring package. We worked windage area hard. Those heads flow decent air if you work with above 6500 rpm. You want to make better average power across the board imo you better get rid of some area and make better radius and shape improvements.

The more I have immersed myself into learning about airflow, and induction for my own personal curiosity, I have realized I am not interested enough to devote 20 years, and countless tens of thousands of dollars to learning. If I want to make power I pay a professional to spec parts. Assembly, wiring, basic mechanic work I can handle. You guys have made the costly mistakes and learned.. I would be a fool not to utilize your services. On this board I have got great advice from Chad Speier, as well as Mike Jones, and everything purchased from them has done exactly what they said it would and more. I didn't have to waste money and time buying the wrong parts. I try to save a buck when I can. But for specifying a naturally aspirated combination. I am out of my element. Being an industrial maintenance technician at a tier one automotive supplier has opened my eyes to just how much I do not know. Most folks don't have a clue just how many people, pieces of equipment, shipping firms, and various other entities are involved in the production of a simple 1.5" 3/8-18 grade 5 bolt.

My point is, the fact that professional motorsports people can market and sell the parts they do on such a small scale for the prices they do is amazing, it has to be a labor of love. They damn sure ain't doing it to get rich, the margins just aren't there. And the fact that they come here and share their knowledge with knuckleheads like me is just plain awesome

[Dave B]

Op
The best thing you could do is add some stroke into your deal like Walter eluded too. You can make that head work better and bring your peak area down. Trq benefits will be huge with that weight and gear. That 3.625 stroke or shorte really needs to be upstairs to shine. Good luck with your project and don't over think it or it will never get done. My daughters first effort made 540 hp and ran like 450 hp at track. She researched stuff pretty thoroughly. But until you do this awhile ,most things you read fly out the window. Have fun , if it doesn't cut the mustard then stay after it

[Walter R. Malik]

I have an LQ4 with cnc ported #821 heads, 387 cid, (4.020" x 3.812"), with a much larger cam, (257/266@.050" - .730"/.710" valve lift), which dyno'ed at 687 horsepower using 1 7/8" headers and a 2 plane intake manifold ... A Holley 2-plane, 300-133 , dual-quad intake with 2 Edelbrock 750 carbs.
With a bit smaller cam & carbs, I believe this would be great on the street and probably be well over the 600 horsepower mark.

With 8 separate O2 sensors in the headers, the distribution was not bad.

Solid roller I’m assuming. Impressive, especially with the dual carb dual plane intake! That’s a big cam. If I get a stroker kit then that’ll help. I don’t want to over cam this thing and make it sluggish down low but I need to make the target.

NO, Bullet Hydraulic Roller camshaft ... limited travel "Johnson" HYDRAULIC roller lifters; ST2126LSR were almost $1,000.00,
with Harland Sharp 1.7/1 adjustable rocker arms.
That crank is an "offset ground" O.E.M. stocker with Honda size journals.

This engine was originally built for a Holley "Hi-Ram", tunnel ram type intake manifold with 2 "Custom" Holley 1050 Dominator carbs.
That combination, (all the rest was the same), made 752 horsepower @ 7,400 RPM. That inlet combination was changed for more testing.
A cam for a lower RPM range would have made it very street-able with the smaller inlet system.

[MD383]

Change of plans on the build after talking with some people and reading the comments. I’ll just cut some weight on the car to compensate for less hp. No big deal. I’m looking at cans with the following durations 230/238, 234/236, and 236/248 on 109-110 LSA’s +4 maybe? I don’t want a mild steady lope cam but I also don’t want a pig down low when I’m on the street! Looking for a hot street setup. When I look into cams in the mid 230’s duration I’m seeing cams starting around 3500 RPM but they’re all on 113 LSA’s. If I get them ground on a 109 or a 110 +4 since I’m carbureted won’t that have it come in maybe 800 RPM earlier? I always thought 4 degrees was around a 400rpm difference in the curve. 3500 is too high for street use to me even with a manual and that sounds like more of a max effort strip car.

Here’s the thing. I’m used to larger cams in smaller cubic inch engines with first gen SBC’s but I’ve never ran an LS. For example, I have a 327 with a 250@50 on a 104 LSA with 11:1 compression on the street with 4.11’s and I’m fine with it. Also have a 383 with a 236/242 on a 110 LSA with 10.5 compression. LS efficient headflow clearly don’t need as much duration to make power.

[Dave B]

Alot of the higher ls - lobe sep angles of 113 and above keeps people out of trouble on ptv clearance. Alot of guys cut their decks down on ls stuff to get some compression back . I do some things quite a bit different on sparkplug boss ,then I need to mill head pretty hard. 600 is very doable if the effort is put in every detail. That being said, I still have not ran across alot of 370 inch ls deals that broke 540-550 hp with hyd roller cams and factory heads without quite a bit of effort.

[RW TECH]

Don't do the dual plane intake, use the Edelbrock Victor Jr or the Holley 300-131 instead.

Unported 823 heads with LS9 exhaust valves & stock LS3 intake valves make 585 HP on a COPO 350 NA with a 226°/236° @ .050" cam with 525" lift (ASA Cam), and they make 640 HP on a COPO 396 with a 233°/276° @ .050" cam with .630" lift (LS Stage 3 Cam).

Unless you already own them, I wouldn't spend money on the roller rockers. Stock rockers are excellent and they're inexpensive. You can see stock, out of the box rockers in action here:
https://www.facebook.com/share/v/4JVxRg ... tid=oFDknk

[Dave B]

The copo engine is 4.125 bore and Chevy performance heads, not factory turds. Plus that Hi ram will kick the crap out of the those junk vic Jr style intakes. The blocks are considerably better than factory. Like comparing apples to atom bombs.There is a reason those engines are pricey. You can't compare copo results to your factory type pieces. You will be highly disappointed!!!