Eric94GT

Hi all, new member, new (to me) car this summer- LT1 Trans Am. I'd like to understand the pros, cons and path to building up the motor. I'm not looking for something wild, 400ish hp is my goal. I don't intend to race it and I typically cruise and don't top 4k when shifting so torque and drive-ability are key. I'd like the extra power just for occasional fun as well as to personalize the car.

Is there a quintessential guide or progression of proven mods and parts?

Thanks,
Eric

Injuneer

Welcome to Camaro Z28.com!!!

400 HP at the flywheel, or at the rear wheels?

Eric94GT

Hi Fred. You raise a great question. However the 275hp I have now is measured, I'd like to be at 400. 350 at a minimum.

I'm assuming the 275 is net hp but not rwhp, is that correct?

Injuneer

Factory HP ratings are measured at the flywheel. It's based on putting the engine on an engine dyno, with ALL the accessory equipment, stock intake, stock exhaust.

With your T56 manual trans, you will see about 13% loss through the drivetrain. For example your 275 HP factory engine is probably making about 240 HP at the rear wheels. An engine making 400 HP at the flywheel will make about 350 HP at the rear wheels.

To pick up 125 HP at the flywheel, you are either going to max out the "bolt ons" and use a relatively aggressive cam. That will not make it street friendly, and will not be compatible with shifting at 4,000 RPM (an unrealistic limit, even for a stock LT1).

Best bet would be to opt for a basic port job/matching cam on your stock LT1 heads. Mild head porting, coupled with a mild cam can easilly net you 400 HP at the fluywheel, and keep the torque healthy on the low end. You have to make sure the person that specs your cam is aware of the specific requirements.

Here are two outfits that can accomplish that:

http://elliottsportworks.com/

Advanced Induction - LTx Performance Parts

To support the heads/cam, you would need:
-cold air intake
-52mm throttle body
-at least 28 #/HR injectors
-bypass throttle body coolant
-long tube headers
-3" catback exhaust, or dual exhaust
-mail order PCM tune

After you get the HP, you need to make sure it reaches the rear wheels. Your stock drivetrain should be adequate. Then you make sure the tires hook up.... tubular lower control arms, tubular panhard rod, LCA relocation brackets, adjustable torque arm - chassis mount preferred with your manual trans. And to make sure the chassis maintains it's integrity, subframe connectors. And some sticky tires.

If you are more interested in going around corners fast, rather than in a straight line, look a larger front and rear sway bars, and upgraded springs and shocks.

raroz28

At this years dyno day back in June, the majority of LT1's were head/cam cars. At the wheels, guys were putting down between 320-385. 320 being the very low end and I think that person had a 306. Obviously this is not the norm and these cars had poor tunes or other issues.

Bolt ons/ported heads/cam you can expect around 350-380 and with a highly aggressive cam and good tune 400 rwhp give or take a few. The LT1 that made the most power that day was a 97 Trans am that put down 429.

Eric94GT

Thanks, Fred, I really appreciate the time you invested in your response.

(Now I know what "LE1" and "LE2" means when I see it in threads.)

Sounds like the matched heads/cam route is the way to go. Some questions if you don't mind:

1. Does the motor have to be pulled to work on the heads? Seems like the heads are wayyyy back in the firewall.
2. I'd prefer to be smog compliant to pass DMV muster. To that end I was intending to keep the original exhaust manifolds, (new) single cat and Flowmaster cat-back. At least for the first pass at this. Is this a deal breaker?
3. Regarding cold air induction, I have a Ram Air hood and plumbing. This is not stock as I don't believe Ram Air was available unless it was an SLP Firehawk or the '96 WS6. Please see pics below. Is what I have useful or for show?
4. I'm thinking I need to replace the electronics (coils and wires) as they are original - 20 years old. To phase this because I can't do it all at the same time, what do you recommend for progression of upgrades?

Thanks!

Injuneer

That looks like the Suncoast hood and airbox. I have an SLP hood and airbox, and they are basically identical to the 96/97 WS6 Ram Air hood, except the airbox does not have the "PONTIAC" and "Ram Air" logos cast in the cover. I cut the center grid out of the airbox cover and opened it up to the max area. I also have the Fernco 3" sewer pipe connector that is smooth, and replaces the corrugated tube between the MAF sensor and throttle body - $6 including the stainless steel clamps, at any hardware box store.











This is a factory WS6 airbox:

Injuneer

To answer the other questions:

1 - It's tight, but you can do the heads and cam change with engine in the car.

2 - There are headers available with all the emissions connections. Some are CARB-EO emissions certified. I have a set of AS&M mid-length headers, that are a good alternative to long tubes. They can be set up to allow the use of the factory cat. You are legal if you don't relocate the cat(s) or change the number of cats. My AS&M's are modified to allow a true dual exhaust setup. Keeping the stock manifolds would really hurt the HP.

4 - If anything in the ignition system is original, it will likely need replacement - spark plugs, plug/coil wires, and coil. Start with the plugs and wires. The ignition control module can also fail due to heat soak. Even if you haven't had a problem, it's a good idea to space the bracket off the driver's side head:

4th Gen LT1 F-body Tech Articles

Eric94GT

That's a nice looking machine and with 800/800 at the wheels must be a gas to drive.

My ignition is all original except for the Opti. That was just replaced with the upgraded GM unit this spring.

Suggestions for replacement? MSD?

Good to know I can do headers without DMV problems, I'll have to look into that some more.

The links you provided yesterday were really great, I learned quite a bit. The video on the CNC machine doing the heads was cool :-)

Thanks Fred.

raroz28

If you ask me the LT1 is a piece of cake to work on.

You can easily do heads with the engine in the car. People with stock manifolds have to deal with getting those rusty hard to reach bolts out of the head. I replaced my manifolds with headers before I replaced my heads but when I did my heads I was easily able to remove all the bolts from the heads and pull the heads right out.

The worst part about working on the heads/cam is the coolant mess that gets made. Take your time getting the coolant out cleanly and it makes the job a lot less painful.

raroz28

If you have a new genuine GM Opti leave it alone. It is the best distributor for the car. The MSD sucks. The only thing you can do better is what Fred has done.

Eric94GT

No plans to mess with the new GM Opti but wondering what brand wires and coil?

raroz28

Stock coil is fine don't waste money on an aftermarket.

For wires I have used MSD, Taylor, and most recently I got a set of blue streak racing wires from Jegs for 30 shipped to my house. See if they're still available - I think they're great. Great fitment and they measured what they were supposed to measure when I put the ohm meter on them.

Why have I gone through so many sets of wires? I have burnt them all up. The MSDs went on when I first put headers on ten years ago and I found them almost impossible to route without being near heat. So I bought the Taylor OTVC wires and those were pretty good with staying out of the range of heat. Those wires I replaced simply because I just got new exhaust put on, a new cam and plugs so I figured I'd replace the wires too. I retained a few of the OTVC brackets and ran the new wires through them to keep them away from header primaries that are unavoidable if you try to do a stock routing, esp with BBK headers.

Edit: These are the wires I got. http://www.jegs.com/i/Blue-Streak/343/10033/10002/-1

Chimera96

Eric94..

IMHO, I would route plug wires exactly like stock in the brackets & looms. Not a easy job but doable. You will need to do it from underneath, through wheel wells and from above. Remove the starter for better access passenger side

get a quality set of wires specific to LT1. I like Magnacore but also hear good reports of Taylor & MSD. Use dialectic grease on boot ends. FWIW I had no problems putting 8.5mm plug wires in stock looms/brackets

on headers...check with your state's emission regulations and get "compliant" headers if smog testing is a concern. Here in California it is strict, WI may be easier.

Injuneer

The 800HP/800lb-ft is at the flywheel. The TH400 trans contributes to a ~21.8% drivetrain loss, putting it at 625 HP at the rear wheels. And the nitrous isn't really usable on the street.... no traction, even with the 315 drag radials. Doesn't really matter.... it just sits in the garage any more.

The LTCC coil per cylinder setup is nice, and the wire routing with the AS&M's becomes extremely easy and clean.... never burned a wire. This isn't an LTCC, but it uses the 8 LS1 coils, and as you can see from the date on the photo, it was done before the LTCC was even available: