Almost a year ago, I bought a 1991 305 TPI (speed density) with 700R4. I ditched the automatic shortly after and have a T-5 now. But with the 2.73 gears, I'm having hard time keeping up with 305 auto TBI cars (though I usually pass them in 3rd gear ).

So I'm trying to find a decent cam for my application. AFAIK, the automatic cars were given a weaker cam and were rated 195hp. With the stock cam for an M5 engine, I should gain cca 20hp. (1991 stock M5 cam: 202/207, .404/.415, 114.5)

I would like to go just a tad bigger on the duration but more on the lift. Would the ZZ3 cam be too radical? (208/221, .474/.510, 112deg) Should I go somewhere in between? I want to keep the car legal and fun, I don't want to turn it into a race car or anything. Just want to cruise around with adequate power, not 190 horses.

I'll be adding Hedman headers and Y-pipe in the fall so that will help too.

Thanks ahead for your input, guys.
Lou

 

Your 305 is either rated at 215-235 hp... Its only in 86 that they received those stupid weak cams only giving them 190 hp... Your biggest problem is in your rear gearing... You are actually better off replacing the gears in your rear than doin a cam, it will cut down your expensives by at least half!!!!!

 

Hmm, so you're saying that 91-92's automatics did not receive the weaker cams? Nice. So I do NOT need a new cam, that's good!
Though, how can a new rear end be cheaper than a cam? Last time I checked, rear ends were hundreds of dollars, cams go for a hundred or so. Am I missing something.

I like the highway mileage so I'd like to stick with my 2.73's.

Thanks for the info.
Lou

 

Like you I have the 2.73's in my '91 Trans Am. And they suck. Gas mileage isn't something to write home about either.

Anyway my point, I bought a complete 3.42 posi rear end for $300 locally. Plus the speedo recalibration gears and rear end oil, it is close to $350 total. A cam swap is $100 for the cam, then add a new timing chain/belt ($?), you might as well get new springs ($100 or so) and gaskets and stuff ($100) so already you've hit $300. And unless you got some nice heads to go with this cam, btw would set you back at least $600 more, they still won't give you the bang for the buck that gears give you. People told me to expect .6-.7 reduction in times going from 2.73's to 3.42's. That's 7 car lengths difference!!!!!

 

yes i agreed with the cam question, i have a 91 auto 305 tpi and it had the same cam in it as the 5 speed ones

 

so its only 1986 with the weaker cam?? I have an 87 305 tpi

 

According to this technical article, the weaker auto cam lived until 1987.

Lou

 

sig has cam that I used in my 305

 

I'm pretty sure there is a glitch in that... the 88/89 M5 305 and 350's got the same cam, but *I BELEIVE* the 88/89 auto 305's still had a slightly weaker cam. The 90's and up, both motors, had the same cam.....

... maybe I'm wrong, but the 305 that was in my 89 LB9 auto felt like a the one that was in my 86 LB9 auto (10088155), while my current 88 M5 formula is a beast by comparison. If the 89 auto 305 got the same cam that was in my current 88 305, I would have noticed a lot less of a diference. Yes, some due to the slushbox 700r4, but not the very destinct diference that is plainly obvious to me. I could easily be mistake though as I don't know the complete history of the 89 305 in question, maybe it got an 86/87 motor at some point for all I know.

 

1986-1989 Auto LB9's got the crap cam. 88 and 89' manuals got the L98 cam, 90-92 all got the l98 with the exception of the L03

 

In 1987 they first started the factory roller cam, so something had to change from 86 to 87!!! 86 is the weekest cam... I am in the process of redoin my timing set and all and am finding this out in the process!!! Anyway, I never said buy a new rear end, I said get new gears for it!!! I am gonna see about buying 3.73s and replacing my 3.23s in my current posi rear!!! Gears will run you anywhere from $165-350, something like that!!! Depends what all you get... I know they are just as much as a cam, but you dont have to pay for all the labor to tear the whole motor apart and get everything else replaced...

 

Yes,

1986 = flat tappet version of the peanut.
1987-1989 = roller verion of the peanut.

 

gm *** the peanut cam is older than that. this cam comes from the early 80's as a flat tappet version

 

Well that is'nt very thirdgen specific is it .

 

so 305 autos dont have a peanut cam? Then why does the manual make 230 and the auto make 205? (using upper 90's hp figures). The 350 had 245, that means that if all the Z28 cams are the same, the 350 gained 40 hp just from displacement...doesnt seem right. The 305 auto HAS a peanut cam...everyone tells me

 

 

I think the 87-89 LB9 had different cams for M5/A4 but 90+ had the same cam. look in the tech data section and look how they list them, 87-89 are listed seperate with different hp figures but 90+ has both A4/M5 listed as one

the 230hp was the G92 cars

 

i know for sure my 91 305 tpi auto had the 350 cam in it, i just took it out 2 months ago and cross checked it, and its not the g92, i agreed that the g92 is the 230, if iam not mistaken it had the dual cats

 

dual cats ads 20 hp?.........

 

The autos/non-G92 305 TPIs would pretty obviously be underrated at 205hp if they indeed have the better cam. Probably making all of the 215-220hp the previous single cat better cam TPI car made...

 

if i have more than 205 hp, why does it take so long to get up to 60mph? The engine is quite fine with 80k on it

 

Dan that would be a valid argument if you had another thirdgen to compare it with, we all know these things arent the fastest cars made.

 

You need higher numercally rear end gears!!!!!

 

Yeah dan get some 3.42s and feel yourself fly to 60 in no time

 

it has a posi rear end that didnt originally come on the car so im guessing it doesnt have stock gears...what is the procedure to find out my gears, something about counting the revolutions of the tire to the driveshaft

 

Mark the rear and mark the pinion.

Spin it slowly and count how many turns it takes to spin the wheels once.

2.77 turns equal 2.77 gear

Little over 3 turns equals 3.08 gears

Can pull the cover and count the teeth, you might end up having to unless u can verify some other way if the rear was swapped in from another car anyways.

As far as the cam selection goes I would personally check out some of the new Comp stuff.

Keep it in the 210-220 rangish and you should have something that is a step up and still civil for mileage/street fun. Do watch out for lift if u have stock heads. I'm not sure how much you can get away with, with stock heads and springs on a 305.

later
Jeremy

 

If the rear is out of the car, 3.8TransAm is correct.

If you have it in the car, put your tranny is 3rd, go up to 70mph and look at the tach. If it's between 2500 and 3000 you have 2.7x gears.

If you're referring to another procedure, I don't know.

All SD TPI cars have the L98 cam. My car has a single-cat exhaust and is an auto. See the stock dyno numbers in my sig. So obviously the 210hp figure for single cat cars is underrated. And the slow 0-60 is because of the crappy 2.73's found on most automatic cars.

 

where is your sig?

 

Whoops!

 

That translates to how much at the crank?

 

not much.....