I just bought a 92 z28 with 305 TPI auto. I'm assuming my car has 2.73 gears and the 205 horse motor. My question is what is the difference between the 205 hp 305 and the 230 hp 305?

 

Well, I'll take a crack since nobody else has. Many will tell you that the auto trans/305 TPI got the peanut cam (milder cam) but we've seen enough anecdotal evidence on this board that the 91-92 305 TPIs ALL got the hotter L-98 cam (just like the 350 and 305 TPI/5-speed engines), despite the fact that every shop manual and piece of documentation says they should not have.

Seems the HP differences were due mostly to exhaust system (single cat vs. dual) and slight differences in chip programming. The 20 or so HP difference seems to be slightly overstated between the auto and 5-speed cars at least for 91 and 92.

 

the 205 horse 305 has the "peanut cam" the 230 horse 5 speed 305 has the l98 cam... and the performance is nearly identical to the L98

 

Like Damon said, ALL 90-92 305 TPIs received the L98 cam. This isn't anecdotal though, more than a few people have dissassembled would be peanut cam SD TPIs only to find the L98 cam part number stamped on it.

And somebody looked ti up in the GM parts computer and it lists the L98 cam as the replacement for all TPI cars.

And ALL SD 305 TPI bins have the same fuel curve. If they had different cams they would have changed it.

The power difference is entirely made in the exhaust. The A4/.73 and M5/3.08 cars came with the small TPI style exhaust manifolds and 2.25" cat and catback.

When i swapped to dual cats with the big outlet manifolds i went from 15.0 @ 90 to 14.8 @ 93. There's your 25hp, and that was still a 2.73 car

 

"the 205 horse 305 has the "peanut cam" the 230 horse 5 speed 305 has the l98 cam... and the performance is nearly identical to the L98"


Define identical performance. 345 lb-ft from a 305? All those two engines have in common is the cam and the restrictive intake, the potential of the two is worlds apart. Not tryin to start a fight, just clarifying.

 

i agree. i havent driven a stock 305 that can perform like my stock l98

 

Thx -- I've been trying to make this point over on the Ontario Board.

RP.

 

Nobody said the 305 has 345 ft-lbs of torque. He just said that they have nearly identical performance. The 5-speed gear ratios are much better suited to the TPI's power band than the 700R4, with it's mile wide ratio gap between 1st and 2nd gear. Couple that with the fact that the majority of the 5-speed cars got better rear end gears, and it's not so hard to see why a 5 speed 305 with only 15 less horsepower (and a scoche less weight) can run close to an L98 automatic.

 

thank you jim....ed you said that the cam is the same and the only difference is in the exhaust...why is the redline on a 305 auto 5 grand and the 5 speed car is 5,500?....

l98's run 14.6-14.8....my 305 5 speed ran a 14.7
id say thats pretty identical

 

14.7???????????bull ****!!!!!!!!!!!!!!!!!!!!!!!!!!!!
for a stock 5 speed 305???????
lol

 

whats the bull****...the fact that my completly stock 91 lb9 ran a 14.7 or that fact that your slower?...please im so tired of people like you....
theres guys on here that have run 3 tenths faster then i have...but you know everything right....the next thing that your gonna say is "ohhh you have a lb9 i that it was an l03"...then ill say "you cant read very well because its the first sentence in the first post"

dont call bs if u have no clue what your taling baout

 

Thats not bull! My 87 LB9 auto ran a 15.8 and with a cam change ran a 14.8. If I had the better gears ie 3.42 with the G92 or even the 3.08s I'd have been well into the 14's. As is I'm running 14.0x's outa the same car, stock stall and 2.73's.

 

14.7 outta a 5 speeed SD 305 is perfectl reasonable.

Isnt there a guy on here in the 13's with a bolt on one ?

 

Its a shame guys. I love the fact that no one here gets along or wants to belive what can easly be done and proved. No one belived me that my LB9 auto 85 would run and where near 14. Well when it came down to it i ran a 14.7 and i only have minor, very minor ad ons. Its possible guys that some people take better car of a car then some, in which cases power for these taken care for cars may be better then that of an uncared vehical with same specs. So unless you all plan on throwing up the BS flag because your car isnt doing the same thing, remember no two snowflakes are alike, just like cars man no two are identical.

 

the thing is that my car is auto 305 and runs 15.4's

 

In true stock form, my L98 ran 14.30s with 155,000 miles on the clock. I know mine is far from the same as a fresh one. I believe there are a couple of people on here who have ran almost 14.0s and I believe BigMike92Z ran high 13 in a stock L98. Although the 5-speed 305 is impressive, and I do easily believe it ran a 14.70. Usually the trap speed is a 3-4 miles per hour behind. So the L98 is capable of being faster, for those with an l98 that have trouble breaking at 14.50, or even faster may have traction problems.

Just my opinion, I'm sure I'll catch some flames from someone....

 

nope your right on the money...the l98 will run 14.50's traction permitting...i dunno about the 3 mph faster though...my buddys l98 ran a 14.9@92 and a half....mine was 14.7@93 and a half....ive seen some 14.5-6 at 93 aswell

 

But is your car a SD Car ?

Even if it is, Just Because your car is slow dosent mean anything.

 

AHAHAHAAAAAAAHAHAAA.....its not BS buddy. Jus cuz your car is a snail...lol.

 

F-crazy, that l98 is not healthly. Or either your at a high alitude.

Don't take that has being mean, only what I believe. I believe a weak l98 should pull some 95-96mph, while the healthy ones should run 97-98. I've seen many do this so that's my reasoning. Even mine which I consider somewhat weak pulled a 96mph in stock form. That's paper airfilter... and all.

Most l98s should run atleast 95-96 mph, especially the SD systems in the later models. I've always seen them run better.

But, what I've seen and what you've seen are completly different, so I'm not expecting you to agree with me.

 

sorry about the comment i didnt know
my 1991 z28 auto runs 15.6 and its all stock can i drop a second with hooker catback,hi flow cat, and hooker short headers?

 

the guys car is in ontario and im not sure of the altitude...i do agree that the l98's should run faster.....although the fastest one ive seen was a 88 roc that ran a 14.6@96 or 97 i forgot