New LS1 Owners - Newbie Tech - Building First 403 LS Car - What can expect?

I am starting first build on 2001 Camaro - all previous experience on a 69 with old MKIV 427. Found good looking car with high miles and in need of upgrade.

Looking at LPE 403 short block with AFR 225 Heads, reusing LS6 manifold, TB, MAF and possibly injectors. Looking for recommendations on cam. This is to be a daily street driven car and looking for decent (>23 mpg) on highway. New engine gets long tube headers, Y pipe and cat back system as well.

Planning 9 inch Moser rear with 3.90 set and rear suspension upgrades, frame connectors etc, car is 6SP. Wondering what transmission mods recommended if use drag radials on weekend.

Any help appreciated. Lastly, having drag raced the 69 for many years find it hard to believe minimal mods needed to make the Gen IV cars so fast.

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Old Car - 69 with 13:1 427, AFR CNC Heads, CC solid roller,Jerico 4 speed (8 mpg downhill with tail-wind)

New Car - want something can actually drive and A/C works

Uhm... in short terms, a NASTY sounding idle and sub 11 second 1/4 times at well over 120 mph. It'll be a blast aye? :cheers:

well, I'm going to disagree with the guy above me.

Your streetability and idle will depend on what cam you choose. The LS6 intake and ESPECIALLY a stock throttle body is really going to hold you back. If you can swing a 90mm tb and intake, do it. Making a streetable 500rwhp is attainable while keeping good gas mileage. Going to PM you the name of a couple good custom cam grinders... at least give one a call.

As far as the trans, the T-56 is pretty stout, you should just need a good clutch upgrade.

+1^ you might have to rebuild the tranny if it has alot of miles, six speeds inc. is my choice.

Thanks for advice on the intake & TB - any pointers on injectors? I got the PM on cam recommendations and will follow-up with both. While going fast is fun, I need something that can be driven without too many issues.

As to runnint 10's, it took a lot of horsepower and time & suspension to get the 69 there. I don't see any way the 403 could be even close to the old 427 as the heads installed flow way better than anything you can find off the shelf for LSX - especially on exhaust side. (>300 cfm)

I'd be happy with a daily ride going into mid-11's without N2O.

you could make that motor run 10s easily with solid heads and a nice chunky cam shaft...you can probably make great streetable power thanks to your 400+ ci...
look up Robert56, hes a local guy made great numbers with a 408 (i believe) using a stock LS6 intake and a MILD cam...

i have a feeling youll suprise the shit outa ur self with that 403 and AFRs... i say throw a decent sized cam in it and youll have your self a stout daily driver

you could make that motor run 10s easily with solid heads and a nice chunky cam shaft...you can probably make great streetable power thanks to your 400+ ci...
look up Robert56, hes a local guy made great numbers with a 408 (i believe) using a stock LS6 intake and a MILD cam...

And enough N2O to knock out a herd of elephants. LOL!

Seriously though he did make some good N/A numbers.

Yeah streetability is an issue if you want a DD (which it seems you want). A decent mild cam should still be a blast. For injectors, i'd say maybe 42# ones, with a walbro fuel pump, and you should be set for whatever.

i run a vrx5 cam and it sounds amazing, the torque curve is flat from 3500 to 6000+ since your engine is a 402 and mine is a baby 383 i would say that using the same came wont represent any issues for a daily driver. i also still get 28+ mpg at 65-70 in 6th on t he highway. If you could swing it i would say pick up a fast 92. your going to have a amazing set up so why not add all of the parts at one time.

obviously you will need to upgrade the drivetrain. I would also suggest you call tony mamo and discuss your goals with him. I believe he would recommend the AFR 205s for your application. The smaller intake ports will increase induction velocity and give you better low end torque.

In my experiance, you will not want to DD this thing. my "mild" 346 got old real fast. I love the trans am, but on a tuesday morning i didn't appreciate all the vibrations and noise. I now drive a Dodge ram 1500 ($1100 DD) and leave the bird in the garage during the week.

Another thing to consider is keeping the milage of the parts you are about to spend so much money for. The top end of my motor (AFR w/ ported fast 90/90) costs $4,500. The money spent on the truck was well spent considering I am not putting additional wear and tear on, what i affectionally call 'the race car.'


At the end of the day, you want to be able to enjoy your car. It is much more enjoyable to be able to drive it when you want instead of being forced to drive it on every occassion. I have really started to enjoy my car alot more now that it i don't drive it everyday.

Drivetrain upgrades was a lesson learned with Gen I car. With a 6SP, figure either a 9 inch or S60 iw all that will last with any reliability. Was also planning to use GW links and torque arm. Their Geh I products are the best.

As for DD, I am looking for reliability, power and fun. I have other options for getting to work that are rather boring. I'm not a kid anymore and am looking to try to have a little fun along the way.

I had not considered the AFR305's for this application but will study the flow numbers again. I really liked the LPE L92 head option but the intake manifolds options don't look good there. Their intake flow was very high, exhaust a little challanged.

My dealings with old BBC's have showed me that exhaust flow capabilities are just as important as intake. The Gen IV heads flow like crazy on intake but appear a little low on exhaust. I suspect your pal tony has figured out how to increase his in the 205's.

I just finished up my build a few weeks ago. Let me tell you its a blast to drive around town. I have great driveability and was still able to hit the 500hp mark. I would def. recomend getting a Fast 92 Combo or you will be leaving a lot on the table. I used Delphi 42lb injectors which came out to somewhere around 48lb's.