OK, I have an '84 Z28. It is mostly stock (exception of a K&N air filter and stainless steel exhaust). It has a 5.0 Liter H.O. 305 L69 engine in it.

I'm looking for mods. I hear rumors hear and there that there are great mods to increase HP to my motor and I was wondering who knew them and what they were.

I'm not interested in building a dragster. But since I want to rebuild this motor, I thought if there were some good mods for it, that would be the time to drop them in.

Thanks!

 

One of the biggest restrictions on that motor is the stock manifolds along with the y-pipe. Get yourself some headers. That's run around $300 or medium priced ones.

 

Here's what I did, Maniac:
1) Installed an XE262H cam, along with requisite valve springs on a 106 to 108 degree intake centerline.
2) Headers & cat-back exhaust
3) Edelbrock Performer manifold.
4) very important: New heads. Buy yourself some used Corvette heads, then port and polish them. Keep the original valve sizes. Put the original head gasket on as a template, and scribe the original bore onto each combustion chamber face. Grind out a relief around the intake valve up to this scribe line, but not past it. Next, mill the heads to get 56cc of combustion chamber. Use a .015" steel head gasket to yield a 9.75:1 compression ratio, or thereabouts.
5) CAREFULLY bring each and every piston up to top-dead center. Mask off everything but the relief that lines up with the intake valve. When I say mask off, I mean MASK OFF THE WHOLE ENGINE. You'll mask off the engine eight times. It's about a half-hour per piston. Using a die grinder with an aluminum carbide cutter, slightly enlarge the piston flycut to clear the bigger 1.94 inch valve. It dont take much! Since these engines were never balanced to better than 5 grams per piston, and you'll be removing less than a gram each, you wont throw off the balance by much. Just be sure to remove the same amount of material from each piston. Again, with the aluminum shavings flying everywhere, be sure to clean off everything before removing the masking and re-taping for the next piston. Step #5 is necessary to clear the bigger valves, if you plan on bumping your valve lift up beyond .476", and revving to 6500 RPM.

6) Buy a looser lockup-style torque converter such as a Neal 2700 RPM unit, or (if you like big bucks) a precicion industries 3200 RPM lockup converter. Beware that your transmission might not have the 30-spline count input shaft. It depends on the year of transmission and the exact build date. My old 700R4, a July, 1984 build, had a 30 spline input shaft. However, I exploded it and now have a 1988 transmission.

7) Build a cold-air induction system. Use dryer duct and pull cold air from the underside of the car, in front of the radiator. Gut your dual snorkel air cleaner of the baffles.

With the new heads, the cam, exhaust, and torque converter, your car will go from 15.4 @ 90 MPH to 13.7 at 101 MPH.

I know, I've done the same thing.

 

Daniel,

What happened to your webpage?

 

ws6transam,

As for the trans mission, my Z28 has the stock 5 speed manual. I'm not an expert, but the manual shift lacks a torque converter if I recall....

If I'm right, what needs done to a manual shifter for those kinda changes? Anything?

Thanks!!

 

Your right. No torque converter for the T5! I didnt see anything on your original post that mentioned the type of transmission so I just assumed automatic, and figured that you'd discount that bit of 'free' advice in cases of a manual transmission. What kinds of updates for your transmission? Well, I'd start with a 'world class' transmission swap for one thing. 300 horsepower wont be very easy on that T5. You'll need as much beef as you can get. OTOH, you could start saving for a T56 swap and just ride that T5 for as long as it lasts. If you are careful on the shifts you should be able to make it last a long, long time.

--Dan

Sitting bull, my website was KILLED off by a hacker who threw a tantrum and destroyed the IST server where it used to reside. I'm now working on resurrecting it at this location:

http://www.ws6transam.org

It's nowhere near done though as there were close to 300 links and over 90 Megbytes of files and pictures.

At least it's alive though, with about 250 broken links

 

Yeah, I forgot to list the manual tranny....

Thanks for all the info. I had a pretty good idea that if a car built to push 190HP factory suddenly went up to pushing ballpark of 300HP that it would rip the crap out of that original transmission....

I'm intending on rebuilding my Z28 (body and engine) once I get a garage to call my own. I figure in the mean time, I should find out what all can be done to make this all it can be. I like the L69 engine and since I've heard there's great mods for 'em, might as well ask.

Thanks!

 

well, i know you probably wont get the gains that I did when I did the exhaust on my LG4. I did Edelbrock headers, 3" y-pipe, 3" hi-flo cat, and a 3" SLP cat-back. Doing this alone dropped me 8 1/2 tenths. So, I went from a bone stock 17.38 to 15.11 with the exhaust, "DR" rods, "G" hanger, bumped timing, and 3.73 gears. All together, I pain $230 for all of it. I know the L69 has a far better exhaust than my LG4 did, but if I were you, i'd expect some serious gains from it.

 

See sig for mods.

I love the way it runs. Haven't had a chance to see what the improvement is over the tweaked stock 16.85 at 5800' Bandimere, but I suspect substantial.

I'd recommend the same for you without reservation.

 

Mmmmm, Bandimere. I have some good stories (and about 300 pictures) from Bandimere speedway, summer of 1987. I remember the "Jolly Rancher" wheeliemobile doing these quarter-mile long wheelies, showering sparks the whole way. They set about thirty grass fires along the edge of the strip, and crews had to rush down the strip with fire extinguishers putting them out!

I dont think anyone who HASNT been to Bandimere can appreciate what it means to do 16.85 at that altitude. I think that at the time, the "top eliminator" top-fuel E/T for the mile-high nationals(which was Joe Amato, I think) was just under 250 MPH. Don Garlits was in the 240 MPH range, after running 279 MPH only a month earlier at low altitude.

My ride at the time was this 1968 Chrysler New Yorker with a 10.25:1 stock 440, factory rated at 510 ft.lbs. I bought the car for ninety bucks and it didnt have any rust! 'Course, the 6 miles per gallon kind of sucked, but I had to back way off on the timing because all I could buy was this 89 octane crap. Had I known then what I know now, I would have yanked out that old cam and cranked up the duration and narrowed the LSA to alleviate the spark knock

Sorry, I've gone off topic, but I couldnt help myself. I'm a storyteller at heart I guess

 

Well as far as exhaust goes, I recently had a little work done in that.

When I bought my Camaro, the guy recently had the exhaust repair by Midas or Minieke....

This last summer I took it to a shop that replaced my cat and from the cat back installed custom bent stainless steel. The muffler is a custom made muffler from their shop. I believe the pipes from the cat back are 2.5 in. with 3 in. tails.

After this work was all done, MAN did things open up a LOT. I'm not sure how the car was supposed to run out of the factory..... But, after this exhuast was done I could take the car on a straight away and punch it to 55MPH in 2nd gear and 85 in 3rd gear. I was stunned, this was a huge boost to anything I've ever felt out of this Z28!

I have yet to take it to a drag strip to see what it can do....

 

Take it to the strip and you'll probably be rewarded with a 15.1 second time slip at 91 to 93 MPH. That's none too shabby for an otherwise stock 305!

Put on some Spohn lower control arms if you want to really make it launch, BTW. Just beware your clutch!