I was hoping that somebody can give me some advice on where to look for an explanation for my lack of power. The engine is a 305 tbi in a 88 gmc 1/2 ton auto, It has good compression,new wires,plug's,cap,roter,pcv, air filter etc. The timing is at 0o and approx 30o advance.
I don't expect this engine to pull like a pro stock but at the moment it has approximately the same power as an old ford pinto I used to have. What am I missing?? Are these motor's just naturally wimpy or is there something I'm not seeing.
The computer isn't throwing any codes , The vacuum is good ,it start's and run's all right (a small miss when it get's to operating temp,which I think might be a small leak in the EGR valve,).
Any and all help would really be appreciated.........SR

 

ive got the same engine, it's comeing along pretty good, my mod's are in the sig, ill be getting it dyno'd in a few weeks so ill be posting again with what gain's iv'e seen. Im hopeing to have over 200hp but if I don't oh-well, ill get their for sure when I put the World s/r torqure heads on when I get them flowed/ported and polished and also my edelbrock intake. You can make power it just take the normal crap like heads, headers. intake, cam and so on. Best of luck

 

Well it could be because it's in a heavy truck. Which auto do you have the OD or TH400(4L80)?

 

a good place to start would be to check out the ultimate tbi 1 & 2 in the tech articles. it is a series of simple and cost effective mods that will help boost performance a little and give you better mileage. also check out the DIY AFPR, it is a good way to help you tune your engien to deal with upgrades.
after that the regular hot rod stuff always helps, exhaust system, custom chip, aftermarket intake......you get teh idea.
it does not take a lto to boost the factory rated 170hp to over 200 to be honest. just look aroudn here at how many guys have done it with simple stuff with otu spending a lot fo money.

later
tim

 

IROC22: The truck has a 3 spd auto, I thought it was a turbo 350 but I could be wrong
NJSPEEDER: I'll check out the thread's you suggested. Maybe a few litle thing's combined will help it out. Hell it couldn't be much worse, right now it accelerates like an electric golf cart.
The typical hot rod part's would no doubt help as well but I want my somewhat limited speed part's budjet to go toward's my 89 Formula TPI.
Thank's for the suggestion's.......SR

 

I have a 93 chevy silverado with a 305 tbi and it to is slow. I ran a 17.9 at 72 mph. I put a thottle body spacer, jet chip, KN and pulleys on and it ran a 17.23 at 75 mph. I do not drive it that much anymore since I bought a 88 formula with a 350 tpi. Since I drive my car more it makes my truck feel even slower.

 

Can I see some dyno printouts? A stock 5-speed L03 F-Body should be putting down around 145rwhp, give or take some margin of error for state of tune and drivetrain loss. Are you telling me there are (many) people on here who are putting down 170rwhp??? I find that incredibly hard to believe, but I am open to looking at dyno printouts or even just the data...

 

170hp is what the factory rates the engine at. gm started giving rear wheel hp ratings in teh early 70's.
my personal result was running 84.9 mph when my car was dead stock at a little over 3500lbs. it calculates out to liek 165 at the wheels.

later
tim

 

Its not rearwheel horsepower its still flywheel horsepower.

 

That 165hp you calculated was flywheel HP, not rear wheel HP. I still insist that it is NOT that easy to get an L03 from 170fwhp to 200fwhp. I'm inclined to say it's impossible without opening at least the top end of the thing. Maybe with a cam but you'll have to do some tweaking of the TBI and its surrounding systems first, aka not "with simple stuff" as you stated...feel free to prove me wrong, though! It's a learning process that way.

 

Thank's Guy's I think I'll just do what "FAHQ" is doing and drive my firebird more and my truck less...... In the winter when their is 3' of snow and the Firebird is parked the truck feel's downright peppy.........lol.................Thank's again for the suggestion's.........SR

 

no, the formula i use is for rear wheel hp. (.00427*mph)(.00427*mph)(.00427*mph)(vehicle weight)= rwhp +/- 5%
that woudl be the correct number for a car that was very low mileage at teh time and rated at 170hp since gm has been releasing rwhp numbers as the rating since 70 or 71.

to find 30 hp you can think of it as seeing another 3-4mph in trap speed. an open element, ultimate tbi mods, diy afpr, and shifting at 5000rpm you can see that gain. total cost is maybe $50 if you get another tb from a junk yard to avoid downtime while prepping it.

later
tim

 

It's still fwhp, but what it is now (started in 1973) is SAE net rating which is the engine as it would be in the vehicle; with all the accessories and such. Gross ratings were previously how they measured hp and it was about 50-80hp depending on what application.

The 4L80 is the new name for an old TH400. GM used it as a cost effective tranny right up until 93 I believe. Not the hot lick for acceleration.

Freeing up 30hp from a stock engine is easy. It's so choked from the factory.

 

No they havent , all horspower rating are taken at the flywheel not the rearwheels. That 170 hp rating is from the flywheel. Period

 

I know all of that , my point was that he keeps saying GM used rearwheel numbers when that isnt not even remotely true.

 

i don't know where the info came from saying GM uses RWHP for its ratings, but thats absolutely untrue. It always has and always will be a flywheel rating. SAE net is still flywheel, just with all accessories and a full exhaust to simulate how its like in a car. No stock TBI 305 on this planet has 170 rwhp and never will, its all at the flywheel.

 

Engines are currently rated at flywheel horsepower (SAE). Although some current Chevy engines put out that amount of horsepower at the rear wheels (LS1) they aren't rated at the rear wheels, just way underrated. Ford overated their figures in the mustang cobra which caused some trouble for that big dumb blue oval.

 

yeah it seemed to be more of an estimated #, since the intake wasnt up to par to make the horsepower numbers they claimed.