The Car:
-'94 Z28 Auto Convertible with 140k miles, owned for 12 years.
-Engine is bone stock, except for an SLP Cold Air intake.
-Also recently purchased (used) BMR tubular Kmember and lower control arms.
-Aftermarket aluminum driveshaft
-Engine is currently on the stand, waiting me to develop a plan (and obtain funds) for rebuilding.


Goals:
-Modest increase in HP, say 50-100
-Reliable and Durable. No racing, just want a solid Z28 with a little more power that I can rely on for years.

What I'm thinking about:
-Standard Engine overhaul, with a few upgrades.....possibly new cam, lifters, rockers...Edlebrock intake, 58mm TB....????
-Upgrade ignition, maybe MSD all around or converting to distributor-less system (I've replaced my Opti-Spark twice and have had all around frequent problems with the ignition system's reliability)
-Long Tube headers
-Possibly delete the A.I.R. just for the sake of getting it out of the way and ease of installation of headers
-Eventually an upgraded rear end, and sub-frame connectors (mainly due to this being a convertible)

Questions/Suggestions?:
-I've never done a complete engine rebuild on this scale before, am I on the right track with my ideas? What other kinds of simple things can I do to the engine?
-If I put an upgraded Cam in, what other parts should I upgrade as well, to ensure the engine runs correctly? Will I need new valves/rockers/lifters/etc...? What Cams (and other components) would you recommend? I've seen Comp Cams all over the place, how are they?
-What ignition setups are the best for reliability?
-Are there any modifications I will have to make for the Long Tubes to fit? Can I keep the stock Cat-back exhaust system?


I appreciate any and all suggestions that you all can give! This site is awesome and has helped me out a lot over the last few years! This is going to be a loooong (and in the end, expensive!) rebuild, but it will be fun!!! I will post some pictures soon!

 

Whats your budget? You will eat through the stock transmission easily. I would say do a stock rebuild or maybe a 355 with some head work and a cam, stall converter, and suspension. That should wake it up.

 

if the cylinders are not out of round you may not need pistons. considering the miles I'm gona say you will need to have it bored over and invest in some pistons. if your doing that you may as well go 30 over for a 355. also up your compression to 11.5. with reverse flow cooling the lt1 likes high compression, take advantage of it. look over elliotts port works and consider using him for heads intake and cam. man is a magician with the lt1.

 

Stock rebuilds of high mile motor can get very costly. If you need to bore the cylinders grind the crank, resize the rods and do a valve and guide job you can hit $2500-$3000 just in machine shop and parts cost. With higher miles stock rebuilds it almost always cheaper to get a remanufactured motor then to rebuild one.

Think of this way. They are set up to do 50-100 engines at a time. When you have a machine shop do yours they are making 1. That means you have to cover all the costs of setting up the machines for all the different processes. In most cases it take longer to set the machine up then it takes to machine the parts. In some cases it is even cheaper to buy New engines then it is to have a high mile motor rebuilt.

If you are talking about name brands call their tech support on every non-stock part. You have very modest goals I think Comp Cam will tell you a perfect fit and what needs done to support it. I would also call the header manufacture. Long tube headers always give you the best Dyno numbers BUT those number are always at the engine max RPM. If your going to be street driving and staying mostly under 4000 RPM mid lengths would be a better choice but don't take my word on it, call the manufacture. The last thing you want is to build a miss matched engine. It is easy to add parts that give the best dyno numbers but they can hurt how you car preforms under 3000 RPM.

IMO 50-100 HP is just bolt-on easily done with headers, Cam and a tune. It should be very dependable and even get decent MPG.

Green arrow had a thread on converting the Opti? Also I think I have read the GM performance Opti is about the best in terms of reliability but I just read that somewhere, no proof here.

 

I have seen some used LS1's with computer cheaper than that machining cost in the previous post. And the HP is already higher in the stock LS motor. Maybe sell your LT1 and get some headers. This is what I have been thinking instead of upgrading my LT1.

 

Well, I was considering getting a remanufactured engine as an option, but I haven't really sat and crunched the numbers. Any places you can recommend to find one? Honestly, I think I wanted to do a rebuild on this engine just for the challenge and the experience...but you're right, the cost will definitely add up quick.

What exactly does a 355 consist of? Just bored out with new pistons and cam?

How difficult is an LS1 swap? I've seen some threads on this site for them, but haven't looked at them yet. Would there be any additional changes besides harness/computer?

I don't have any set budget yet, this is probably going to be a little-by-little project and end up dragging on for a long time. But I have no time-crunch, my wife and I each have a reliable vehicle in the meantime, so this is going to be like my "Tim Taylor hotrod" project.

Thanks for the great advice so far!

 

I think for the modest amount of HP gains you want, the rebuild is not worth it. You can easily get that type of hp with a good intake and exhaust system, a cam, and a tune.

You already have a good running engine. Assuming there's no leaks, worn parts, and etc, why not make a 383 stroker out of it? The concept is the same as making it a 355.

Chevy 383 Stroker Engines. Not a lot of info, but it's a good starting point.

Which, of course, should answer your 355 question... you're simply raising the cubic inch displacement. Right now, you have 350 cubic inches of displacement (that's what 5.7L means, just a conversion to be honest).

You're basically changing out the cam, the crank if you're going for 383 (not sure if you change it for a 355), perhaps bore out the pistons if need be, and I think that's pretty much it. The LT1 is a very popular engine to modify, and because it's closely related to the famed 350SBC, there's many people that have swapped it in older cars, or beefed it up for their engine swap, not to mention it's the same engine that's in the Corvette, Caprice 9C1, and Impala SS so there's a lot of information out there that will help you out. All you have to do is search.

You now have 2 ideas that could possibly work for you... you can go full out and build a 383, or you can just do something small and do a 355. Either way, look up how to do them, the benefits of both, and then decide what you want to do.

Just remember that you need to beef up the trans to handle the extra horses and the burnouts, doughnuts, etc that you will probably want to do. This probably means to make sure your rear end will also handle the power, so you may want to look into that as well for better gearing.

 

If you're looking for something to drive around town, that's not going to see track time, a 355 is in your ball park or a reman'd engine with goodies. A 383 is nice, but you'll have a good amount of money in that and will eat up your fuel mileage.

Whether you opt to rebuild yours or buy a reman'd one, upping the compression (assuming you can put 91 or 93 oct. in it), installing a bigger cam, bolt ons, getting a tune, and having head/intake work done will easily put you over your goals.

Depending on whether you have an A4 or M6 and how often you plan on burning tires, you may be okay on the trans and rear end. But it would not be a bad idea at all to have them rebuilt or replaced because of their higher mileage.

 

140k is not that many miles. are you seeing blow by or going though oil? check your compression and go from there. you can get it up to 325hp pretty easy, cai, long tube headers, good 3 in cat back, good computer tune. to go more add cam, 1.6 roller rockers, intake and head work. its easy to spend 4k.

 

Before I pulled engine, it was not running. It finally quit in the fall of '12, then it had to sit untouched in my driveway for a year (I got deployed overseas). Before it died, the ignition was getting weaker and weaker, I was burning through starters and usually took a small prayer to get it to turn over.

Also, my oil pressure was getting very low, not even hitting the halfway mark at higher rpm, and BARELY off the bottom at idle. I ran Seafoam through a few times, thinking it might free up any gunked up oil passages. No change. Also there is oil leaking from a couple different points. Not sure if theres any blow by, how can I check?

If I stick with rebuilding this engine (vice getting a reman'd) I'll probably keep it more basic and try to keep as many original parts as I can, and go with better cam, tune and headers. 383 would be awesome but I don't think Im going that route. We'll see what happens when its torn apart.