RJE

Hey guys, I'm building an NA LS3 for my bracket race car. The car is a big tire, (32x14.5x15) four link car. The engine consists of a new aluminum 6.2 block, 4in forged crank, 6.125 H beam rod with ARP bolts, DSS racing domed 4.065 pistons, GMPP cnc LS3 heads with BTR 660 spring kit, Bullet 257/265 dur 650/650 lift cam, CID 4.5 4500 intake, and I'll be running a 1150 dominator carb on 110 race gas. The CR calculates out to 13.75 with the heads milled to 64cc. I'll also be running a methanol carb in the summer for cooling purposes. This is my first LS engine, and I know there really good, but wanted to hear what everyone thought the power output might be before I put it on the dyno. I'm trying not to set myself up for disappointment.

RJE

G Atsma

Why a distributor? Coil on plug is more efficient with nothing mechanical to break.

RJE

Well, first off I already had the MSD 7AL ignition. So no need to spend money on something that already works well, and I've been racing for over 20 yrs and can't remember a distributor issue, but I can remember a coil giving up.

Randy

Kawboom

If the chart I have found on the Net is anything to go by, your head flow is going to be your limiting factor. The GMPP heads flow about 365CFM on the intake side for your cam lift. The general rule of thumb is 1CFM = 2HP, so you will max out this head combo at 730 horsepower at the crank.

Doug G

Was guessing 750 +/- until the above post.

Che70velle

iTrader: (6)

Don’t cut yourself short. I’ve seen many LS engines make more than 2hp per cfm, especially with a carb. I’d say your about right with the 750, assuming the carb is right.

Kawboom

It's not impossible, but those flow numbers are only about 10% better flow than stock LS3 heads that came on corvettes Camaros and police cars with 430hp. The LS3 crate engines were rated at 525. Eventually you saturate the head.

Che70velle

iTrader: (6)

True. But that’s a low compression, small cam engine with a plastic intake and smallish TB. 365 CFM is capable if setup right in full-on race mode, which the OP here is shooting for. Induction is on par to get enough air on the engine. The CNC porting on these castings opens them up some which will help with saturation. Carb will cool the air charge by adding fuel into the stream up high. The L92 casting is a very capable head, and ported it’s even better, for big numbers. Outcome here will be interesting. Hopefully the OP posts results.

RJE

Thanks for the input guys. I was thinking and hoping for around 750 in good weather on race gas. Hopefully I'll be getting it to the dyno this month and see for sure. The plan is to dyno it with gas dominator and the alcohol dominator and get a tune up for both. If any of you are familar with alcohol carbs you know they can make some more power over gas, but there a pita in cold weather, that's why I swap in the winter. On my previous engine in my sig I only fell to a 5.59 in 90 deg weather on alcohol vs a 5.51 on race gas in 50 deg weather, but we'll see soon enough and I'll post the results.

gametech

iTrader: (1)

I hate to be captain obvious here, but you still need at least 1 coil for a distributor setup. If you are in fact using the 1 coil, it has to do 8x the work of a normal ls coil. Just a new parameter to add to your math.

ZONES89RS

iTrader: (25)

I’d say 650ish at the flywheel. Maybe 670

Doug G

I have always went with 2.2HP per CFM "capable".

365 x 2.2 ...803. "possible"

Lots more go into it than that though.

G Atsma

So would you rather the ONLY coil you have quit? Or ONLY one of eight? I KNOW what my answer would be....
The horse and buggy worked great UNTIL those newfangled gas engines showed up.....

Che70velle

iTrader: (6)

Gary, I often see you over here giving folks crap about carbs and distributors. Back before electronic distributors showed up, and we had to set the points in a distributer, I would agree with you all day, but electronic distributors are crazy reliable. Way more reliable than a GM crank sensor. I’ve lost a few GM crank sensors, but never once have I had a single problem with a MSD distributor, or even an Oem distributer. MSD ignition boxes on the other hand…I’ve burnt up more of those stinking things than I can count. Mallory ignition distributors…different story also. I’ve lost the electronic eye in one of those before also. Speaking of coils…of all the years I’ve tinkered and worked on and around any engine, I’ve never once seen a coil go bad in person, and I’ve ran coils at extreme levels way up over 8k rpm for hours and hours. They are resilient pieces of equipment and last virtually forever. I look at your post above this way….with 8 coils on my engine, which I have several of…not knocking it at all…I have 8 times the chances of losing a coil, than I do with a single coil ignition setup.
I can relate to your horse and buggy comment however. I love horses and think they are awesome, but when I’ve ever been asked to go horseback riding I always reply “No. That’s why God invented ATV’s”.

G Atsma

Good stuff Scott, for which I do thank you! I always feel a bit more educated after reading your reply to any post of mine.
HOWEVER (LOL!!) .... IF a coil is gonna fail, would you rather it be one of eight? OR the only one on the whole engine??
You know I had to razz ya man.... enjoy the weekend!

RJE

My buddy has a 377 LS3 with stock heads that makes 660 hp, and he could stand to have a bigger cam.

RJE

Ok, got the engine finished and ran it on the test stand to check for leaks and break it in. I'm very happy, it fired immediately, and was super responsive. Going to get it to the dyno in the next week or so hopefully, and I'll post the results.

Randy

vht

Every bit of 750 I bet.

RJE

Ok, got to the dyno today and the uncorrected numbers are 683 hp @ 7000 rpm and 581 tq @ 5500 rpm. The weather was 84 degs 77% humidity 29.89 baro and the DA was 2068 ft. I was having an issue with my vac pump, so once I get that sorted out it should make a little bit more.

Randy