LS7/LS3 build questions

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08-13-2021, 05:44 PM

sgilbert1967

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LS7/LS3 build questions

Hey all,
Long term member who can usually read what he needs and not bother anyone. Built a 98 Camaro SS 6.0L successfully for my wife with 228r basically and stall she put 18k on it, lol.
Built a 402 stroker for a 69 Camaro topped wirh ported LS3 heads and a Ported OD LSA blower, that is still working good for him.....but Im in over my head for what I'm going to try to do for myself...

Due to MY imminent unavailability, it's finally time to pull the old Dinosaur out of my personal 67 Camaro replacing it with something more modern, durable and mainstream to get worked on when I'm not around to do it....problem is...

No offense at all I love the LS, I am going to it but this car hasn't seen under 700hp since the first few of the over 30 years I owned it, purchased from my uncle when I was a kid and will be left to my grandson.

It's currently a home Built for boost BBC with a home retrofit of a discontinued Oval port Street tunnel ram converter to sequential MPI and home built reverse top 102mm tb adapter welded in ( fits under cowl hood) with an F1A-94 procharger. I was going for port velocity here and tunnel ram to give nothing anywhere as I truly drive the car, Thru a 4l80e with billet stall and out the back with a 1200hp Worm Gear Aluminum 9inch and 3.25 gears.

It deploy a custom hyd roller ramp that helps with a little take up on a solid pressure fed roller lifter( morel), hybrid setup...she doesn't roll over at 6300rpm like most BBC heh...just getting started big bore, short stroke, long rod.....

I use the MS3 Pro Ultimate with their TCU connected via Canbus and a Rasberry mini PC driving a 10.1" 2k screen along with running the tuning/logging software...several custom touches to my tune from injector phasing to using RPM vs Turbine VS Output shaft for TC and boost/timing per gear ect ect...even a 3 way valve with a PWM output using the pressure differential between the filter and impeller for a vacuum source to overcome one of the Tial bypass valve for boost control, can't get to zero but I can get to 4psi that way...

Why all the back story, I see a lot of people not get the help they look for because they aren't honest with what they want and need in my case even come to expect...

I want, I need to swap this thing over to an all aluminum LS setup near zero maintence or at least maintence they can find help with. I'll probably dumb the engine management down with a Terminator X Max setup ect to make it plug n play for em....

I want an all aluminum setup because if I have to loose all that power at least I'll be taking 200-300lbs off the nose at the same time, which should make the entire combo more consistent and sure-footed.

It's on old muscle car I don't care about corners, I really just want it to be predictable on the street or track......

My thoughts were a 5.3L Gen 4 block resleeve ( or bore to 3.902-5 for a 383/Cathedral setup initially) up to the 4.155 area to unshroud valves with plenty of area for the fire ring to clamp on using a 4.00 stroke because it's cheaper and it should with a resleeve have a good stable BDC and thrust angle....keeping ring pack down far enough for boost in the event I make it long enough lol.....gonna miss boost....

The block was partially to satisfy the need to accommodate LS7 heads ( or available intake as I can easily fit that tunnel ram style FAST LSX looking one), if I haven't learned anything in my years it's invest in the best head you can and build around them....to ME those 12 Degree valves and the entry angles from the intakes I've looked at ( will probably go a 4500 EFI carb style intake with 4500 TB and injectors because if nothing else come on its a 67 Camaro) seems to be very effective. An LS with that LS7 top end just looks like it belongs better in the old car too...

Once I started looking sweet Jesus good lord you guys have the world as your Oyster for selection to much selection in fact, but I am trying to maintain at least 650hp with a durable valvetrain that has manners ( current BBC cam is 233/247 602/612 115+4 and it cleans up quick cruising locked in at 1600-2000rpm depending on 58-74mph), I assume bigger inch and the compression these run NA will help that as well...

Aside from choice, Jesus christ prices are literally BATSHIT...4k for heads from the big guys and $3550 for a block...good lord i could build a 2000hp BBC for that much at least max out my F1A-94 or 850+ HP NA but it's still a big heavy leaky Dinosaur 🦕 lol.....

Then I watch the test where Speedmaster does pretty good ( really almost zero difference between heads in the LS3 anr LS7 test) and their LS7 heads are dirt *** cheap and in-stock lol, so I'm like screw that drop ship those to a porter what he gets he gets out of em with some work and a good valve job...it all gets cloudy here....
1. What's the deal, ive used everything from stock to AFR BBC heads currently Brodix, im 2 hrs from them. Why not buy the literally $350 head and pay the porter to work em over ( I don't need as much flow as the 495ci Holder test and they did well), kind of think of them as a P head blank casting the porter takes out how he wants on a smaller engine may not need a ton of work. Similar to the -11 of the day it's a porters head ( positive spin on it ).
2. They list them and I asked again today at 60cc they claim not a typo and 15 degree valve angle again they claim not a typo...was this the same head tested, if the valves are 15 but the runner 12 that would seem to gonna be hard on the short side....They have a matching intake I guess....
2. What's the deal with 1.8 ratio on LS7? Can you not just use 1.7 or are these individually mounted with no base and you have to use 1.8 LS7 specific rockers? And I guess one needs to keep it under .650 if you do?
3. Why the low lift ( I do see the stock port dies after .650) capability on most advertised LS7 heads of around .615? Is this assuming you have stock pistons and can't clear it? A function of contacting walls? Overall weight of a valve that was designed to be titanium so the seemingly small 1.30 spring pocket selection can't control a .650 lift at SS valve weight?
4. DO 6 Bolt heads bolt to 4 bolt blocks and the extra is just there using I assume a 4 bolt gasket?
5. I think I know the LS7 head forces obviously LS7 intakes but does it have a different exhaust pattern? Will standard LS3 swap headers work? 1 7/8"?
6. The 800lb gorilla in the room might be will the non mid bore specific $4k LS7 heads aka the cheapo Speedmasters 2.20/1.60 ( or i guess the head porter might can set them up smaller if required ), hit the bores in a 4.065 LS3 block at 415ci? Is there still any benefit to the entry angles after you shrink the bore down or does one simply pick a really good LS3 or Cathedral searching for torque when forced under 4.125 due to budget constraints.....

I'd really like to reverse myself this time and not skimp on short block, go ahead and do the sleeved 434ci setup for 93 with all the gains you get from that and put the cheapest LS7 top end that will work on it, if I live then I can boost later or upgrade heads if not they are golden with an engine that should start, require little maintence and not leak...

It's just very hard to go this far back in power and that's the only reason I'm even looking at the headache of sleeved blocks and LS7 top ends vs a 415ci and whatever the flavor of head is best for like a 479-11 comp cam size, similar to what I have 233/247 650 ish or 238/250 111+3 kinda range..
I started out determined to get 700 durable horsepower the hours of reading doesn't seem to support that as a realistic goal but dang id like to hang on to at least 650hp....so the car still runs 10s at least ( id like it dead nuts reliable low 10s for them so it's just legal and stable).

Jumping back into anything other than the most cookie cutter gap and boost is overwhelming in both options and pricing, it's hard for the old timer to pay Big M and Big Chief head prices to make 650hp....haha but I just want them to have something anyone can work on several years from now.....the car has had a BBC in it over 30 years and I've modernized it as best I can but it's time, however I still want the best bang for the buck and it looks like pretty much all the quick NA cars run LS7 top ends and they look sinister too...

Thanks to anyone that reads this,lol I never got pithy typical long winded grey beard...

LS7/LS3 build questions

LS7/LS3 build questions

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