ez2cdave

I just picked up a 2000 Z/28 hardtop with a 4L60E and I want to make a daily-driver "sleeper" out of it with decent mpg, but a broad torque range (400 - 450 RWHP ). Yes, the 10-Bolt rear will be going "bye-bye", and the Torque Arm, SFC's, etc. will be addressed, too !

Reliability, "Stealth", longevity, mpg, and lack of oil consumption are highly important.

I'm looking at a Stroker, but the "combinations" are messing with my mind . . . I know that I will be going "all forged", even though this is a street motor.

I am trying to decide the "H-Beam" vs. "I-Beam" connecting rod issue . . . Thoughts ?

These are the combinations I'm considering :

LS2 Block :
4.000" Bore X 3.900" Stroke = 392 - 398 ci ( + .030" or less is OK )
4.000" Bore X 4.000" Stroke = 402 - 408 ci ( + .030" or less is OK )

LQ4 / LQ9 Block: ( The extra 60 lbs. doesn't bother me )
4.000" Bore X 3.900" Stroke = 392 - 398 ci ( + .030" or less is OK )
4.000" Bore X 4.000" Stroke = 402 - 408 ci ( + .030" or less is OK )

LS3 Block :
4.065" Bore X 3.900" Stroke = 405 ci
4.065" Bore X 4.000" Stroke = 415 ci

I am favoring the 3.900" Stroke to reduce piston rock, decrease oil consumption, and to get the Wrist Pin out the the Oil Ring Land.

HEADS : "CATHEDRAL" or "RECTANGULAR" Port Heads ???

This is my BIGGEST question . . . I really need HELP on this area !!!

I have been thinking about CNC ported L92 / LS3 heads from Scoggin-Dickey, but am worried they might be "too large" for a street motor and "lazy" at low rpm. Heads are an area where I have very little technical knowledge, so I need all the help I can get !

CAMSHAFT : I have been looking at the Lingenfelter (LPE ) GT-11 Cam, but I would like to get Patrick G. to optimize a cam, based on my specific motor.

Thanks, in advance, for you input !

Baconz28

I'm no expert but torque is not all in the heads. I think your cam is really where it's at no matter if you using 243 heads or ls3 heads. Budget plays a big role too but you never mentioned that.

lil john

TFS 225/235 for Cat. heads TFS LS3 4 the 4.0+ bore size 408-416. This is where all the power is made.

aussie-revhead

Hi mate, I am also building a 415 sleeper (LQ4/LQ9 bored to 4.065") and I recently learned that my production line CNC ported LS3 heads flow less than stockers with a valve job at all points below 0.550" (up to 30cfm!! less), they are equal between 0.550 and 0.650 and the CNC heads only pull clear at 0.700. So be careful when buying heads, check all flow points not just the commonly shown peak flow. I dont think velocity is as large a concern with 400+ cubic inches, of course its important but not as much as it is with a 346 ci motor.

ez2cdave

My budget is not as high as I would like, but $6000 - $7000, for the long block, sounds about right.

I have no intention of spending $2000 apiece for cylinder heads. That's why the L92 heads appeal to me . . . Big flow at a low price, only $850 each, CNC ported.

https://sdparts.com/details/scoggin-...enter/sd8804-1

I want a dynamic compression of 8.5:1, for pump gas, on the street.

I'm concerned that the large ports might be sluggish in street driving.

ez2cdave

These are the heads I've been looking at . . .

https://sdparts.com/details/scoggin-...enter/sd8804-1

aussie-revhead

Same idea as me, LS3 heads flow heaps and are great value, but why so low on the comp? My stocker LS1 has 10:1 .....

SinisterWS6

Flow numbers don't mean everything.

Figure out what size block you want to use as your foundation and go from there.

You could easily attain your results with any of the blocks you named off, including the LS1 the car came with. Wouldn't really need to build a stroker either. Good H/C/I set up runs 420-450rwhp easily. Stroker obviously would make this easier.

H beam rods are budget friendly as far as reliable power rating goes. For 545 bucks, the Callies pieces have been ran way past their rated limit and are a steal honestly.

Oil consumption is more or less related to the factory pcv system, its junk.

whatsa347

iTrader: (6)

Ballistic speed makes small bore ls3 heads, they would be a torque monster on a 408. That's what I would run if I was building an NA motor.

ez2cdave

I want a Dynamic Compression Ratio of 8.5 : 1 . . . The Static Compression Ratio will probably be 11:1 +/- .

ez2cdave

This article comparing Cathedral & Rectangular port heads is interesting.

http://www.gmhightechperformance.com...d/viewall.html

Baconz28

I also have a 2000 z28 but with a 6 speed. It's go be naturally aspirated. 6.0 block bit with ls3 internals. Basically a iron ls3 but without the aluminum cost. I think I'm go have a nice street car combo with ls3 heads btr springs ls3 intake 92mm nick williams throttle body with a custom cam from brisn tooley. It's a big split cam 227/240 on a 113+3. I know I said it already but I think it's in the overall combo and a good choice of a cam to get what you want just not spending 3 grand on a set of aftermarket heads.:-)

ez2cdave

The 346 LS1 would never be able to deliver the "numbers" without having a fairly radical cam.

I am looking for a smooth idle ( or barely noticeable ), as this is a stealth / sleeper project and a true daily driver ( 40-50 miles a day )

By upping the cubes to 392 - 408, a far less aggressive cam profile would be needed. Also, with more torque on hand, deep rear end gearing wouldn't be necessary. That would help my mpg and not sacrifice any top end speed, as a tradeoff would occur with a lower ring & pinion.

I have read about oil consumption problems, in stroker motors, being caused by the pistons rocking at the bottom of the bore, caused by the increased stroke length. Also, it negatively affects engine longevity.

ez2cdave

Agreed . . . That set of CNC'd L92 heads is only $1700 for the PAIR, assembled with Manley S.S. valves.

ez2cdave

The way I am leaning is an iron LQ9 block w/ 4.030" bore, with L92 heads, all forged internals, and a Patrick G custom cam.

I am still "on the fence" on the issue of the stroke . . . 3.900" vs. 4.000".

Baconz28

Pat G did a similar setup awhile back 6.0/L92 heads. The car put down like 465 to the tire with a y pipe exhaust. True duals would help also.

SinisterWS6

Honestly you can "smooth" out an idle a lot in the cam grind, tune, and how loud you like your exhaust.

I would seriously have to differ with you on a "radical cam" needed to make 400-450rwhp. Most of the time people compensate poor heads with a bigger camshaft. Or the cam is way too big in the first place. A properly designed cam can be tame as a kitten. I daily drove a stock cube cam only MS3 6 speed with 3.42's for 3 years, no problems LOL. Mid 230's duration cam's in a LS1 with good heads have made 430-450 with DD quality. Overlap is usually thought of in terms of how radical a cam is, not just duration figures.

Unless your building a stump puller type engine not meant for a sports car, you will most likely end up with some what of a gear change different from the factory size you have now.

Piston rock isn't much of a problem with LS style engines. Properly designed pistons for the rod and stroke, accurate bore, and awesome ring packs we have now help eliminate this problem. I mean if your really asking about H beam vs I beam "issue", which I wasn't aware there was an issue, only in terms of material and power handling abilities, piston rock should be at the bottom of your list of things to think about. I think your concerning yourself with shorter deck height issues of the past than anything.


Chevrolet did produce an engine known as a LY6, essentially a 6.0 iron block with LS3/L92 heads on it out of the factory. You can usually pick one of those up as a entire pull out unit for around 2,000. Also another good starting point to use as a build. A lot of your hard parts are already together, your just swapping out some components.

SinisterWS6

And then he swapped back to Cathedral port heads and picked up more power all over the power band.

If you want a serious recommendation, ask the guys that have built both style of engine (your going to talk to pat G, ask his opinion) and you'll get your answer. I've built both, and nagged other people to death who did LOL. I'd take rectangular heads on a 7000+rpm strip motor, cathedral heads for a street/strip car (or small-med bore aftermarket LS3/7 heads, TSP, MAST). Choice is really budget dependent. Nice thing about LS3 heads is the intake is dirt cheap LOL. If your not going ***** out though, I don't think either decision you make on heads will really matter. Either way, it'll be fun to drive.

If you want more of a torquey street motor, go 4" stroke. Get off the fence, its not a pleasant place to sit. You'd have a nice 408.

Good luck on whichever route you decide to take!

lil john

1000-1200 to get bare L92 heads ported no parts.
TFS LS3 heads bare 1800.
oh yeah you still have to buy heads i have a bare set 175.oo ea. from 08.

ez2cdave

What was your gas mileage with that setup? "MS3" ? Did you mean "LS3" ?

Piston rock is a factor in any stroke over 4", from what I've read online.

"Shorter Deck Height issues of the past" ? Don't all of the production LS motors have a 9.240" Deck Height ? I'm worried about Compression Height issues, oil consumption, and longevity, even with a 4" Stroke.

The rod "issue" is a question of strength vs. weight (I-Beams are usually lighter ).

LY6 - I have considered that, but the static compression is only 9.67:1 and I would be getting a cast rotating assembly. It also retains the stock 3.622" stroke.