I Just bought a 1991 Z28 305 with a t-5 and i was wondering what are some good bolt on products to get some more power. the car has a full exhaust except headers, a MSD coil, new plugs and wires and everything else is stock. where should i go from there? any good bolt ons or more involved suggestions would be appreciated. Thanks

 

How much are you willing to spend? Is the car a daily driver or can you afford to have it out of commision for a week or so? How mechanically inclined are you? Do you just want bolt ons, or do you want to dive into the motor?

I would most definitely start with headers as the stock manifolds are the biggest bottleneck on your car.

 

You're going to get more answers, faster, if I move this to the TPI board (which I'm doing now). Also, do a search, the mods are pretty common.

Best wishes to you.

 

i Agree with 82Z28
I would start off with some headers
Theres very few upgrades you can do to a 305. The cam in it is really small. YOu could get an Lt1 cam but its essentially the same size. Get an open element breather if possible. i have a throttle body so im not sure of what you can and cant do to a tune port

 

with tpi as far as intakes you can go k and n drop in or cold air induction for some extra hp

 

high flow runners are prolly like $700 and not gonna give you much of an increase

 

it is a daily driver but i could afford for it to be out of commission for a while if need be. im pretty mechanicly inclined and i am very willing to dive into the motor. i was looking at roller rocker arms, any suggestions? but i would also like some more basic bolt ons.

 

I'll concur that a nice set of headers would be a great improvement!

 

The 1.6 rocker arms work very good on my 1991 305 TPI, they are easy to instal. I also recommend headers.

 

what brand rockers would you reccomend and will i have to change anything else to make them work?

 

It all depends how much you want to pay, or what quality you want.

Comp cams 1418-16 Steel roller tip are around $170-$190.

Comp cams 1618-16 Chromemoly steel ful roller are around $325-$335.

Comp cams 1016-16 Aluminium full roller are around $350.

You do not have to change anything else.

I would stay away from cheap ebay aluminium rocker arms.

 

You are incorrect. He has a 5-speed car and it all ready has the bigger LT1 size cam. It is the 305 TPI automatic cars that have the peanut cam.

Personally, I recommend 3.73 gears, cut out the airboxs, descreen the maf, airfoil, grind out the bumps in the plenum, and install some headers, also on a 5-speed car a set of underdrive pulleys will probably work nicely.

 

I disagree with descreening the MAF as that has will cause problems with the MAF reading air coming into the engine.. It has been covered before.

I think you should start with regular maintenance items like:
-Full Synthetic oil (Mobil 1, Valvoline, Amsoil, Royal Purple, etc.) and good filter (k&n)
-K&N air filters in the airbox
-Spark plugs and wires and cap&rotor (accel or msd or any other good brand)
-New fuel filter
-Replace Oxygen Sensor (3 wire sensor if you are getting headers so that it gets warm enough to function properly, otherwise a 1 wire sensor will do just fine..)

Then a few other misc. things to do:
-Throttle body coolant bypass (keeps air that enters the engine cooler)
-Cut the airboxes (the stock airbox is good enough for TPI engines, no need for a "cold air intake" ex: those cone filter type intakes.. useless.)
-Throttle body airfoil
-Install a cooler thermostat so your engine runs cooler

A little more advanced things to do:
-Port the plenum & intake manifold (you could also get a used set of bigger runners like AS&M, that's what I did and it still does the job right)
-Rebuild heads (1.6 Roller Rockers, port and polish, etc.)
-Bigger cam
-Headers
-Install posi-traction carrier in rear (if you don't have it already) and put 3.73's (biggest performance improvement for acceleration that you will feel!) This will require new speedometer gears in the tranny, which cost potentially up to 70$ depending on what you currently have in there..
-Once all these mods are done, you will want to give your car a better tune to make the most of all these mods (off the shelf chips do NOT even come close to the performance of a custom tuned chip made by yourself if you know what you are doing..)

Other things you can but shouldn't do for emissions reasons, and will need you to re-tune your computer:
-Remove AIR (Smog pump) and gut the catalytic convertor
-Remove EGR valve and block off
-If you have 9th injector, remove & unplug, and block off

Other suggestion is weight reduction! Less weight will let your car accelerate, handle and brake faster.. Examples of things to reduce weight with: remove ac (personally this is not needed in Canada except for maybe a few hot days in summer but to each his own, plus I have t-tops), hitachi mini starter, aluminum water pump, aluminum intake manifold, headers, remove smog&air&9th injector (very small but everything helps), etc..

That's all I could think of for now!

 

the can has new plugs and wires, im doing full synthetic oil and other basic tune up parts and i was planning on trying to make my own kind of ram air set up by doing this https://www.thirdgen.org/ramair has anyone every done anything like this and is it worth it? thanks

 

I have had mine descreened for 15 years now and it causes no issues only improved airflow. I can data log my car all day and confirm for you it causes no issues. When these cars first came out it was one first mods to do along with gutting the air boxes. I always laugh when I hear people making these ridiculous arguments about how it's going to hurt your car and the MAF readings. More airflow always helps performance.

 

when you say to gut the air box what exactly do you mean?

 

It refers to the lower airbox. The area where the air filters sit. There is a bunch of plastic in their that can be cut out to open up the airflow. Here is a pic of mine cut out. Now go take a look at yours and you will see what I mean.

 

As I said, I disagree with doing this "mod" for various reasons. It's very likely that in the last 15 years your car has not been damaged from it, but I doubt you gained anything from cutting out screens since the MAF is not even the restrictive part of the system, unless ofcourse the rest of your system flows more than 517CFM.. -->

Stock TPI Bosch MAF sensor w/ screens -- 517.8 cfm
Stock TPI Bosch MAF sensor w/o screens -- 658.4 cfm ..

Now, CFM flow aside, there are very good reasons why it is probably better to just leave it alone (even if you know what you are doing on how to cut them out, along with the fins, properly) as there is evidence that suggests and maybe even proves that it does mess with the MAF readings. -->

http://www.gmtips.com/3rd-degree/dox...maf-screen.htm

This site explains why the whole hype about this "free mod" was just hype, unless you have a massively modified TPI engine/intake.

While I do agree with you that, in theory, more airflow generally improves performance, but I do not think that most TPI engines (especially stock ones) will net any HP gain from more airflow in this particular part of the system as it is not the bottleneck of the system.

 

I don't think you are going to gain much from a rocker arm swap. Maybe a few hp. I would go and find a set of headers and matching ypipe. Also, the ram air idea should work good too. You could always look on ebay and buy a cold air induction kit too. A good chip can help. I heard Ed Wright from Fastchips makes good chips. I would get it set to use a 160 degree thermostat and to turn fans on much earlier too. Tuning makes a big difference on these cars.

 

If you insist on rockers though. I have heard that Comp magnum roller tip rockers will clear the centerbolt valve covers. Some rocker arm brands out there will not clear your stock valve covers though.

 

what does tuning exactly intail?

 

data logging and or custom chip burning.

 

That is why i suggested you order a pre-tuned mail order chip from Fastchips or Pcmforless. They are supposed to be a little better than say Hypertech or Jet chips.

 

umm 91 is MAP car....has no MAF to descreen

 

Yes 91-92 used SD (speed density) TPI systems. I just wanted to clarify that descreening the MAF isn't worth it, for anyone reading this thread.

 

I will be rebuilding my 305 in a few months.. It is the same as your car.. 1991 305 TPI with the T5.. I will be doing a new comp cams computer controlled compatible .510 lift cam, Keith Black 10:1 compression pistons, headers and a Y pipe from flowtech and new 24 Lb/ Hr injectors. However the car is getting dyno tuned after this. I also will be adding new roller rockers from Procomp Electronics. I dont know if anyone has heard of them but my father and I have been using them for years now and have never had a problem with their products. Thats just what I'm doing. Hopefully it will be around 300 HP. I do know for a fact the 90-92 TPI cars with the MAP sensor setup( also called Speed Density) is VERY tempermental when it comes to cams and such. I would suggest having your car properly tuned if doing a cam or anything. True dyno tuning is much better than just ordering a chip from a website. Anyways.. All the best with your project! hopefully I gave you a few Ideas

 

Yep, 91 is SD so I guess he has no MAF to descreen. But I disagree and it is worth doing. That is just our "opinion" based on nothing of value. Not a fact.

 

Guys...please agree to disagree about the screens. That particular topic has been one of much contention for years.

nhslacrosse2...I would buy some used SLP or Accel runners, port the plenum, and get some headers (1 5/8 primaries will be easy to install), but I understand Dyno Don's are the best (they are 1 3/4 primaries).

 

No worries I was merely passing on info from what i've read on the net from various sources, which in fact may or may not be right for all I know. Although I would recommend anyone interested in doing it to do their own research and come to their own conclusion, rather than doing something based off of someone's opinion, such as mine or burnout88's... I apologize if I've come off harsh, wasn't the intent

 

Can someone elaborate on how much those roller rocker arms helped? Is there even a appreciable difference?

 

"Theory says if you replace a stock 1.5:1 rocker arm with a 1.6:1 rocker, valve lift will increase throughout the lift curve. Let's take a small-block cam with a max valve lift of 0.450 inch with a 1.5:1 rocker arm. Install a 1.6:1 rocker and the max valve lift jumps to 0.480 inch. That's a healthy 0.030-inch increase in valve lift."

http://www.chevyhiperformance.com/te...ers/index.html

 

I have a 91 1le w/ a 305 lb9, she's already got shorty headers, underdrive pulleys, jacobs elec ignition and it runs pretty good but looking for a little more w/o going into the motor or boost. 3/8 stud on these motors correct? Do they need self aligning ones or no?

 

3/8'' stud, self aligning.

 

In theory, they're said to give a 15-20 HP gain if you get just the roller tip rockers. If you go to the full blown full roller rocker there's probably even more HP unleashed there. I belive they just work on the principle that they cut down on drag, friction, and a parasitic load put on the engine by moving 2 surfaces past each other that dont have a bearing. Also they wear less. I have a comp cams 1.6:1 set on on my 91 305 TPI and I can say that I felt a difference, no doubt about that but its not like all of sudden you're driving a rocket ship. I've also heard that they can actually screw up your cam geometry potentially causing problems which is why im getting rid of my 1.6:1 set and replacing with a full roller 1.5:1 set when I do my cam swap.

 

I have an 89 Camaro, That had a 305 tbi, I dropped in a tbi 305 off of a 93 caprice. rebuilt the heads, and changed out the gaskets, sensors(temp,intake,oil.) As they tend to do it overheats. I want to put a 3 core radiator, new fan switch, new thermostat, and chip. What should i do? What can i do to restore this project to its old self. Dont really care for horsepower, just want to restore it, maybe add a few new parts. Its my daily driver. My goal is to repaint it and have it look and run as stock as possible. Chevy ****ed up on designing the heads. Two exhaust ports side by side. Would headers relieve some of the stress?

 

correction (overheated)

 

Does anyone know of a thread that will help a 92 z28 350 do 5 seconds 0 to 60..lol