Spec Carbureted Engines

[64GunPilot]

Which intake are you running? If I recall, the 305 runs out of air at about 4500-5000 RPM.
You might talk to Sean (Storm Trooper #15) about his experience with his 3rd Gen.
Sean did the 5.3 LS conversion on his car last year. Big change was that the LS uses about
1/2 to 2/3rds the fuel as the 305 and the torque is better across the RPM range.
Trying to recall if he changed diff gears too, he can tell you.

A couple months late on this answer, but as far as the intake, its the Vortec to TPI intake thats on the car now. I've been looking at the 5.3 LS engines out there. Trying to figure out how much going the LS conversion route costs in total. T56s are not cheap, and I'd have to buy all the LS1 accessories, intake, and exhaust manifolds per the rules.

I have a spare Vortec 350. I think I am going to build it per the spec carb rulebook, and then maybe use it in another non-daily driver project and dyno tune it (more emphasis on the tuning than hp/tq numbers). But then, if my 305 starts to have troubles, I can just pull that Vortec as my backup engine since it'll be spec. Thats the thought right now anyways. I just wish the spec engines could run roller cams since thats what I already have.

[Supercharged111]

Sean's 3rd gen still runs (ran?) a T5 at least as far as Hallett.

[39PitCrew]

A couple months late on this answer, but as far as the intake, its the Vortec to TPI intake thats on the car now. I've been looking at the 5.3 LS engines out there. Trying to figure out how much going the LS conversion route costs in total. T56s are not cheap, and I'd have to buy all the LS1 accessories, intake, and exhaust manifolds per the rules.

Talk to Sean, he can tell you costs. And probably give you some ideas on
where to get stuff on a tight budget. I think he actually used the truck block
(LM4?) and accessories brackets because they are readily available at
the pick-a-part yards. And they make more power than you can use.
He runs a tail pipe restrictor to get the HP/TQ numbers down to avoid
penalty weight.

[64GunPilot]

I found this $800 for turn key with accessories, harness, ect. Would need accessories, intake, and exhaust from LS1. So maybe $1250 for all of it. Then getting the trans to bolt up probably needs a bellhousing and crossmember. Yea. Ill definitely get with someone who has done this before. My career in HPDE pre CMC license, will definitely be running the 305 vortec TPI. As long as it lasts, im gonna run it.

https://dallas.craigslist.org/ftw/pt...791509649.html

Looking at the spec carb route, the intake, carb, cam, ect is gonna be over $1000 and that doesnt even include the rebuild. But the engine would be fresh vs 150,000 miles on the 5.3 LS.

[Supercharged111]

Screw an iron block at that price. Run what you have until it holds you up. In the meantime find a real deal on an LM4 aluminum block 5.3. If you're savvy you can convert a truck harness yourself to save a buck. We also passed an RCR to allow cheap aftermarket accessory mounts instead of the ripoff prices CL fiends are demanding. I found myself a $225 LM4 at the pull and pay some time back, hoping to find a spare without a hole in the block at some point. I've hunted down the LS1 rack, k member, steering shaft, plastic tank, etc but just know the swap process, at least on a 4th gen, is fairly involved. The early early LS1s had return lines, so hunting down those rails will be a necessity for that 3rd gen. Not an overwhelming asspain, just something to consider. It's more than a motor and mounts to get that thing in there.

[64GunPilot]

Ive read that the L33 is the best 5.3. Its aluminum and heads are pretty much the same as the LS1 castings.

[Pranav]

Ive read that the L33 is the best 5.3. Its aluminum and heads are pretty much the same as the LS1 castings.

The L33 is a great motor, but you'r spending more money for a hotter motor that will be hard to restrict down to the 260/310 level

Stock 5.3s are easily getting 260hp and just under 310 torque (mine is a weirdo at 262/305), while in most cases LS1s with their better flowing heads and hotter cams are restricting at 260hp and are ending in the 290s on torque.

Stick with an LM4 or LM7, cheaper and a better fit for the class, plus with a stock cam your valvetrain is under less stress.