Bearden4242

I have a destroked ls3 (4.065x3.268) 340ci sitting in a car that weights about 3.1k, 6spd, 3.73 gears, stock 243 heads, revs 7.5k+, 10.5 CR. It is used in autocross and road race. I like it cause its unique but it doesnt perform the way I want. I want more low end torque and for the torque not to fall off around 4.5k.

Option 1. Move to 4.10 gears with ls3 upper (heads+intake), 11.0 CR. This option gets me more mechanical torque and better top end with the ls3 heads, but I will lose some with the rec ports. Will the gain in gearing be nullified by the rec ports?

Option 2. Move to 4.10 gears and get my 243's cnc/ buy aftermarket, 11.0 CR? Seems to be the best of both worlds if I keep the 340ci

Option 3. Keep the 3.73 gears and build a 402ci (4x4) rev to 6.3ish in 3.1k car, ls3 upper, 11.5ish CR. The extra displacement will help with low end, but again will it be nullified by the taller gear and rec ports. I'll have good top end still

Option 4. Same 402 scenario but with cnc 243's/ aftermarket heads? Again best of both worlds.

This all has a budget, but I would like to hear what all of you have to say. I'm not chasing a peak power number, mostly average power and torque that you can feel pulling you.

Thanks for any and all your replies

Che70velle

iTrader: (6)

HioSSilver

iTrader: (8)

You need more gear for a 7500+rpm engine than 3.73. With shifting at 7500 rpm you should never be below 5500 rpm.

What clutch you running?

Tuskyz28

243s on top of a 402ci is another idea i would consider if i was you.

G Atsma

Tusky, I think your post is covered in Option 4, unless I'm missing something

Bearden4242

Would option 1 OR 2 acceptable with the 4.10 gear change?
Sorry I considered posting it there but figured since I was adding gear ratio and it turning into a partial driveline subject posting it here would work

Bearden4242

My thoughts too, this is why I want to move to 4.10's if I keep the 340ci.

I'm running a ls7 clutch/t56 magnum lightweight flywheel

Bearden4242

Mentioned it. This would be ideal but also the most expensive

Bearden4242

You're not

Nick V.

iTrader: (1)

Go ahead and swap to 4.10s in your current setup and then see what you feel.

Bearden4242

I'm leaning towards this as well. Only problem is part of my focus is 2nd gear. 4.10 is fine with the 340, can get to 79mph @7500. I dont think I want to spin the 402 stroker that high so I would stick with the 3.73 can get 73mph @6500 in 2nd

HioSSilver

iTrader: (8)

for what you're doing that clutch is way to heavy. Completely wrong for what you're doing no matter if it's the 340 or a 4xx motor.

what top speeds do you run and how tall is your tire. You may want to move to a 4.30 gear or even 4.56. It's a 7500+ rpm engine, utilize mechanical leverage.

maybe autox you might get below 4500rpm on tight turns but on a road course you never should. That should be a great engine for what you're doing.

what intake are you running?

Bearden4242

Do you have clutch suggestion?

Depends on the track but 150-160 would be the most. In autox I have hit 70-80(2nd gear) but its rare. Tire is 335x30x18 so 25.91". In my basic knowledge I think the engine makes a great platform as well. Trying to figure out how to optimize it all though.

Currently ls6 intake but plan to upgrade to a dorman ls2

HioSSilver

iTrader: (8)

Omg.........those intakes are **** for what you're doing. You need a msd or maybe even a sniper on that engine with a 102 or 105 tb.

How bout telling us everything about the car. We don't even know what kinda car/engine/trans you have. The devil is in the details.

Spec and qtr master both have some nice 7.25 clutches that would work much better in that situation and really smooth up high rpm shifts.

Bearden4242

79 camaro/ ls3 destroked to 340 (4.065x3.268)/ t56 magnum close ratio. Stock 243 heads 10.5 CR, LS6 intake, 3100lbs

I will definitely be considering a smaller clutch.

I have seen some msd air forces used. My approach to the dorman ls2 was based on these

https://bangshift.com/general-news/tech-stories/ls-intake-better-factory-trailblazer-ss-dorman-ls2-factory-replacement/


https://www.hotrod.com/articles/20-l...ifolds-tested/

HioSSilver

iTrader: (8)

All the factory intakes have runners way to long to be spinning to 7500+. You're probably leaving 50hp on the table at 7500 rpm....including the dorman. That's if everything else is working together.

What cam you running? Ever had it on a dyno?

Bearden4242

Looks like I'll be looking for a msd or similar short runner intake.

Cam was a btr ls1/2 stage 3 231/242 @.050 .617/.593
Open 5/55 close 45/7 112+2 LSA only dyno I have is with this cam. It was a "conservative" pull to 7000ish I since turned up rev to 7.5.

I had it recammed after with a 221/223 @.050 .578/.557
CL 106/114. 110 LSA. Open 4.5/45.5 Close 36.5/-2.5.
It needs a new tune since cam, decided to wait till I decided what to to with heads intake etc. Could be placebo but even though it runs rich since cam swap it seems to run stronger.

HioSSilver

iTrader: (8)

That thing is way down on power for whatever reason. It should be easily over 400 as it sets.

big hammer

Bearden4242

That's how I feel. Seems like it might be close to that now with the cam swap without the retune.

Couple clutches I'm looking at are McLeod, RAM, SPEC, and Ace Racing. All dual/twin disk. Trying to keep some of that cost down. Would love a quartermaster but $$$

Also 4.33 gears will allow me 75mph 2nd gear @7500. Think I will go with that.