89Formula2

I'm currently thinking of a few mods to wake up the 305 tpi on my 89 Formula and shed some weight. It's a good, rust free, daily with 117k miles. I don't want to put a cam in it due to not wanting to open up the engine right now. Let me know what you guys think. Just wanting to know if I'm missing anything.

Currently catless with a 3 inch exhaust, stock manifold. AIR system disconnected, pump not removed yet. Not sure what my hp gains would be with the following list.

Future mod list:
1.6 self aligning roller rockers (Stud size is 3/8?)
Headers and Y-pipe from Dougs
Underdrive pulleys
Larger runners from AZSpeed

Some possible weight savings.
Aluminum driveshaft
Aluminum water pump
Powermaster 9526 mini starter
Remove air pump

Komet

Do the headers and mini starter while you're removing the air pump and skip the rest while you begin the hunt for a 350.

Aaron R.

If you are wanting a more powerful car you should go out and buy a late model Honda Accord or a minivan. Trying to make your 1980s technology perform to modern standard is like sending tax dollars to Ukraine (i.e. completely wasting your money).

blacksunshine'91

iTrader: (10)

Shill. What does that have anything to do with him trying to add some HP to his car?

Aaron R.

Sorry, I thought I made that clear enough.

Trying to add some HP to his 1980's 305 would be a waste of money. Like sending tax dollars to corrupt politicians in Ukraine.

89Formula2

Two things that I probably should have said from the beginning. 1. I'm not swapping the engine. I am not trying to make this a 400hp screamer. 250hp at the crank is all I'm really shooting for, 275 would be great, but I'm sure I'd have to drop in a cam for that to happen. 2. My mission for this car is what Jay Leno referred to as "Mildly massaging". Make everything a bit better. A bit more power, a bit less weight, better brakes, etc..

Komet

You should mildly massage the 305 out of the engine bay.

Gently pamper it into the ocean.

Caress its cylinder bores with salt water as it lives out a new, better life as a coral reef.

blacksunshine'91

iTrader: (10)

Weakening Russia's military without losing any U.S. military personnel lives is worth it.

Tom 400 CFI

Uh oh...not PRC!!




I used to think that. I did! I "mildly massaged" my 305 to 14.5's@95. Then? I wanted more, and you probably will too. My car had a sbc 400 in it when I sold it, so, a lot more.

In the short term, the headers that you have planned, runners, base porting and some other "free mods" should get you to ~250.

Fast355

iTrader: (2)

I disagree, ALL of the planned modifications will go right on a 350 later and can make the 305 run very nicely. I have run nitrous on a couple of small blocks as well. Best bang for the buck performance modification there is, no pun intended.

Fast355

iTrader: (2)

While you are wasting your time doing that, I will put the 305 into the 12s and even 11s without removing the short block.

Fast355

iTrader: (2)

I have had no problems getting into the 11s with a 305 using 80s technology TBI. Its a small block Chevy and there is a ton of power to gain doing minimal work.

Komet

Your skill and experience make that claim seem more simple than it is. Rockers, pulleys, runners, and headers are going to put a TPI 305 in the 14s, same as a stock 350. IMO it's better to keep stock together and happy than to spend a thousand dollars on 20hp while L31s sit dormant in the yards, ripe for the picking.

Fast355

iTrader: (2)

I have had a stock TBI 305 run low 15s and a stock TPI 305 run mid-low 14s, that work should put a decent running 305 into the mid 13s. What he is intending to do is a lot more than adding 20 HP. I have never not gotten 10 hp bolting on roller rockers. The rockers, headers and exhaust alone will be a 30-40 hp gain. Putting a stronger aluminum driveshaft is never a bad idea. The under-drive pulleys will add about 6-8 hp back to the tires and allow the engine to rev up more easily. Runners will not make a huge difference to the 305, but it will gain some power over torque peak.

TylerSteez

iTrader: (3)

Would probably just do headers/exhaust and a better ratio rear end for now. Not much you really can do to improve the stock 305 if you don't want to open it up. anything you do eventually do to the 305 would be better off being done to a 350 or larger displacement engine.

Tom 400 CFI

In what? A go-kart? An engine swapped '84 Rabbit? An Ariel Atom?

No STOCK 3rd gen is going mid/low 14's with a STOCK 305. NONE. This fantasy land stuff doesn't help the OP.

Tom 400 CFI

Is it stronger (than a steel one?)? I've never read that or seen it tested, anywhere.

blacksunshine'91

iTrader: (10)

Not sure if it's actually any stronger, but it is much lighter. That equals less rotating mass. Plenty strong for our cars, especially a 305.

Tom 400 CFI

Yeah, either drive shaft is way stronger than strong enough for a 3rd gen.

The rotating mass isn't a meaningful reason to swap it, either. First, it's way too small a diameter to have a meaningful amount of rotating inertia, steel OR aluminum. Second, it doesn't accelerate all that much over the course of an acceleration run (compared to other rotating parts).

TylerSteez

iTrader: (3)

that’s always been my take on it as well. lighter is better but rotating mass is negligent due to its rpm being determined by vehicle speed and rear end ratio. its heavier mass would have an absolutely very minuscule affect on vehicle speed. it’s also a small diameter so whatever mass is theoretically not getting slung far from its center of rotation

Fast355

iTrader: (2)

The critical RPM is higher if you go with something like a LS1 shaft or custom shaft. Aluminum driveshaft does make a difference, about 5-8 ft/lbs across the whole rpm range on a chassis dyno. Driveshaft weight eats into power more than heavier wheels and tires because it spins at 3x the rpm of a wheel/tire combination. I went from a 2-piece steel shaft with a carrier bearing to a 1-piece aluminum in the old G20 van and it picked up 2-3 tenths consistently and it was in the 15s at the time.

Fast355

iTrader: (2)

A STOCK LB9 305 with the L98 cam has NO PROBLEM going mid-low 14s in a STOCK 3rd gen. It is not fantasy land stuff. I had a stock head, stock cam L03/Automatic/2.73 car run 14.50s with merely traction and headers.

Fast355

iTrader: (2)

Here is a stock steel vs aluminum shaft on a LT1. Just grab a stock LS1 aluminum driveshaft, FWIW. It will operate much more smoothly especially if a deeper gear is put in the rear-end.

Drivetrain Modifications #1 (ws6.com)

Fast355

iTrader: (2)

Underdrive pulleys and 1.6:1 rockers will help regardless if they are on the 305 or go on a 350 later. The underdrive pulleys add about 8-10 hp and tq as do the rocker arms and equally as much through the curve. I had a stock head, stock cam 305 TBI make 204 hp at the tires through a 700r4. Headers, exhaust, 1.6 rockers, underdrive pulley, chip tuning.

Aaron R.

What does this mean, to operate "more smoothly"? My steel driveshaft seems very "smooth"...

What do you mean by "critical RPM"? It's a 305, so I'm not understanding what this phrase even means in this conversation.

This all sounds like new speak, or just throwing out phrases to sound intelligent.

Tom 400 CFI

SHOW US.

Fastest stockity stock, stocker I could find was an "HO" 1LE which did 14.8 in MT. That's not mid 14's, that's not low 14's and that's 'cause a STOCK 305 3rd gen won't go mid or low 14's.

The OP don't have an "HO" LB9, and he don't have a 1LE car, so "mid 14's" is not in the discussion or relevant, for him.

Instead, the OP likely has the 305 3rd gen that most have; a low-mid 15 second car.

Tom 400 CFI

This stuff is all over the place....I can only guess that's b/c it's not based on actual objective data. It's hard to parlay whimsical dreams and wishful thoughts, into good advice for the OP.....

Underdrives are great; they give "some" power -not much, but some. I think ^those^ numbers are wishful thinking on a 4500 RPM motor. They improve gas mileage, slightly (probably an unmeasurable amount)....but they cost $2-300 bucks, which quite a lot for the gains. I've bought, had and currently have UD pulleys, but I bought them used for cheap and that is the only way that I would buy them.

Same with the Drive shaft. I got one for free when I worked at a salvage yard decades ago. But the "gain" from one isn't worth the money. Balance your stock drive shaft if you want that 1.1hp. Very, very few people on here care about, or need to care about the drive shaft's critical speed.

Fast355

iTrader: (2)

Critical RPM is where the shaft has a tendency to fail. If someone were to go from a 2.73 to a 3.73 gear that would drastically lower the vehicle speed for the driveshaft critical rpm.

I thought a steel driveshaft was smooth as well, until I upgraded to a GM 3.5" aluminum shaft.

Fast355

iTrader: (2)

They are not wishful thinking. its not the 1.1 hp I care about. It is the average torque gain and that was substantial enough to notice in ET and normal driving.

Underdrive pulley is the same. It reduces accessory load across the whole RPM range. I also had a truck I short belted to run only the alternator and water pump that gained 2 tenths consistently. The engine reved more quickly, hit the stock converter harder, 60' times were better and it just ran quicker.

Tom 400 CFI

LOL...."2 tenths". Copy that, man. As you were.

Aaron R.

I understand critical RPM being the failure point. I just don't understand how that has anything to do with improving performance of the OP's stock 305. Are you suggesting that his steel driveshaft is going to fail behind that stock 305?

I still don't understand how an aluminum driveshaft drives "smoother". I understand it feeling "different" or "less weight", but I still don't understand "smoother" and how that helps the OP. Please explain the physics of this steel vs aluminum becoming "smoother".

Fast355

iTrader: (2)

Why do I need to explain something you can easily google? Google Driveshaft Critical RPM and you will find all the information you could possibly want on the subject. The physics of why the aluminum shaft operates more smoothly than the steel shaft has to do with the diameter of the shaft, thickness of the shaft, the material it is constructed out of and vibration harmonics resulting from the overal combination. The aluminum shaft is less failure prone than the stock shaft. I have calculated the numbers in the past and the stock steel shaft has a critical speed of around 5,000 rpm. Anything over 5,000 rpm is dangerous with the stock steel shaft, regardless of if you balance it or not. Using a P245/50R16 tire and 2.73 gears that is about 140 mph. When you change to a 3.23 gear as I did on the 91 I owned, the critical speed drops to 118 mph. That is the reason the 1LE cars have a larger aluminum shaft. As far as smoother, the aluminum shaft absolutely is smoother. Any driveshaft has what is called a half wave resonance RPM. The half wave resonance RPM is much lower than the critical rpm of the shaft. When the shaft is operating near that RPM range it will transmit vibration that feels like continually running over a rumble strip. Before I knew any of this, I had a 91 Camaro 5.0L with a 3.23 geared rear end from a 4th gen in it. That rumble strip happened between 65 and 75 mph with the stock shaft. I had the shaft balanced and it still felt the same. After much research, I found the GM bulletin on the LT1 F-cars and I replaced the stock shaft with a LS1 shaft. After the LS1 shaft swap the vibration was gone. Turns out the larger diameter aluminum LS1 shaft has a half wave RPM that is close to 1,500 rpm higher than the stock 3" steel shafts. Unless you are running like 150 mph with a 3.23 or 3.42 gear, you will never run into the RPM the half wave occurs at with the LS1 shaft. Driveshaft critical speed is actually why GM speed limits most of their vehicles where they do. It is not tire speed ratings, it corresponds with critical driveshaft RPM and preventing the driveshaft from coming apart and pole vaulting the vehicle.

I will also throw out there that the 3.5" LS1 Aluminum shaft calculates to having 2x the torsional yield strength as the 3" steel shaft. The steel shaft is around 2,500 ft/lbs and the aluminum shaft is over 5,000 ft/lbs. The 5" diameter shaft in my Express van calculates to over 10,000 ft/lbs torsional yield strength. The larger diameter the shaft is made, given the same wall thickness material and length, the higher rpm the critical rpm as well as the more torsional force it can withstand.

Tom 400 CFI

Yeah, come on, Aaron! This is obviously a great mod with high value, that the OP should definitely do! Right? I mean, he's got a car that won't go 140, and can't send more that ~900 lbs down the drive shaft....so....lots of upgrade value there, man.

Fast355

iTrader: (2)

I got my LS1 shaft for $50 and it made it made a difference. The underdrive pulley I used came off a factory 4.3 CPI engine. It was 6.5" diameter instead of the 8" on my L05. You act like he has to shell out $1,000 for a driveshaft. My L03 had no problem getting to 140 mph, to each their own I guess. The L05 in my van would run 110-120 mph in stock form. The LB9 has more power than my L05 had.

A stock L03/Automatic sends about ~1,500 ft/lbs through the driveshaft. Not enough to hurt it, but well over what you claim. 255 x 3.06 x 1.9. The LB9 makes similar torque down where the converter stalls, it would be about the same.

Tom 400 CFI

My god...this stuff is RICH.

I'll bet that shaft made a difference! 1.1 hp's worth!

Did I say $1000 anywhere? Please quote where I said that so that it can be fixed right away.

But wait....the best is yet to come!....

O.K., sure, there is the converter, so we're still 1000 lbs short of the engineered limit of the shaft (if your figure is correct). For sure, he should definitely replace it as a first mod. Oh, yeah.

I wonder if there has been an epidemic of broken drive shafts in stock or stockish 305 3rd gens?....

Tom 400 CFI

That's weird. The site that you linked above, says this:
"The stock shaft has a critical speed with stock 3.42 gearing of 153 MPH."
Whaa.....tha??

6-8 hp, 8-10 hp, 118 mph, 153 mph, 1.1hp, but (a whopping!) 5 lbs!? (different pulls, would be my guess). Who knows WHAT'S going on in Van-Land!

Aaron R.

So I took your advice and Googled it (well, DuckDuckGoed it since I dont need Communists using my search history for anything) and clicked on the first driveshaft link I found, an automotive driveshaft shop in Tulsa specializing in..... driveshafts.
https://www.driveshaftsoftulsa.com/b...el-driveshafts

This custom driveshaft shop said the opposite of your post. It actually says this:
"The other downside to aluminum shafts is that they do not reduce the amount of vibration or noise. This will result in drives that are not as comfortable and can even be distracting to drivers."

There was also some other interesting tidbits of information that APPEAR to debunk or at least disagree with your previous post, so at a minimum this whole aluminum driveshaft idea for the OP is questionable at best.

But hey, maybe he plans to push that little old 305 to 140+ mph on a regular basis and that aluminum driveshaft is the performance upgrade he has been seeking this whole time.

Fast355

iTrader: (2)

I disagree with their point on aluminum shafts causing more vibration, comparing a smaller diameter steel shaft to a larger diameter aluminum shaft. GM powertrain engineers have taken steels shafts out of almost everything. NVH and EPA mileage are two reasons they have done so. Look under just about any truck, SUV or van made in the past 20 years and you will find a 5" diameter aluminum shaft. The material itself may be weaker, but the overall construction is stronger.

If the aluminum shaft increased vibration, GM would not have had a TSB and free aluminum driveshaft replacements on LT1 cars that had a steel shaft.

They also leave out the fact that if a front u-joint were to fail, the aluminum shaft is more likely to crumple when it jams into the pavement rather than pole vault the vehicle or break the u-bolts and knock the rear end out from under the car. I have seen steel shafts do both.

Tom 400 CFI

On a stock 305 3rd gen?

Fast355

iTrader: (2)

What does it matter? The 3rd gen and 4th gen have the same steel driveshaft. The bulletin is for installing a 3rd gen 1LE shaft into a 4th gen.

Years ago, I actually discovered the LS1 shaft fit in a Syclone as well. It is the exact same length.

Tom 400 CFI

Just trying to under stand how "dire" this problem is, that you'e seen. It sounds serious. At this point, I'm wondering if all 305 3rd gens should have a recall issued to replace dangerous, pole-vaulting steel shafts, with safe-T-aluminum? So...you seen steel shafts pole vault a 305 3rd gen? Or break the u-bolts? Or seen a 305 3rd gen break a drive shaft at all?

I think what's happening here, is that we're making a problem, where there isn't one. 305 3rd gens don't break their drive shafts. I've had steel, I've had aluminum. I've tooled on both as hard as my wimpy 305 could tool; clutch drops, neutral drops, roll backs, WOT F-R, F-R, F-R,....no drive shafts ever broke. I think the OP should focus on mods that'll make his car go faster, first, and 1.1hp mods, probably isn't going to do that for him.

Fast355

iTrader: (2)

If I own a 3rd gen again, the LS1 shaft will be one of the first things I put in the car and for more than one reason. The aluminum driveshaft is stupid cheap, smoother and the reduced rotating mass is noticeable in both acceleration and braking. GM put aluminum brake drums for the same reason on many vehicles. That 1.1 hp mod had an ~8-10 ft/lbs gain on the initial acceleration. I actually want another TBI car in the future. I want a 5spd car. It will get ported 113 aluminum heads, full roller rockers, a cam, headers, complete 3" exhaust, 454 throttle body and an EBL. Eventually it would also get a T-56 swap and a 4.10 geared 4th gen rear end. That is how you put a TBI 305 car in the low 12s.

Tom 400 CFI

Mmm...
all of that makes total sense.

Fast355

iTrader: (2)

You do realize Matt Walters 305 was in the low 12s with 113 heads and an old 280 Magnum cam? Of course you don't because you think you know everything.

I had a L30 305 make 280 rwhp with stock 059s and over 300 rwhp with Etec170s milled to 60cc on it with a 218/218 @ 0.050 flat tappet cam and the stock L30 dished pistons. That was also using the stock Vortec truck intake manifold. Same engine with the 059 heads, the GMPP 330hp 350 HO Vortec Q-Jet manifold and a Q-Jet ran a 12.50 @ 112 mph on 2.2s 60' with P245 street rubber in my 1980 Corvette with a 3,000 rpm stalled Powerglide and 3.07 gears. I had a free TH250 in that car for a while after I broke the planetary set in the powerglide but it really did not change the 1/4 mile. I later pulled that engine out of the Vette and put it into a Tahoe. The L30 in the Vette had more power than it had gear, I had it to the 6,500 rpm limiter in the MSD box on night messing around. Somewhere around 165 mph.

You seriously under-estimate the power a modest 305 can make. A factory stock B4C TPI 305/5spd car was clocked at 150 mph and the 350 car only ran 153 mph. That was in an instrumented, detailed police test of the cars.

Komet

Ah, so the 350 car was faster? I was confused, here I was thinking the 350 would be faster with its more cubic inches and greater displacement.

Fast355

iTrader: (2)

So a whole 3 mph in top speed means that I need to run out, tear apart a good running car for a whole 15 hp more. Try again, I have put a 305 TBI car deep into the 11s, quicker than most L98 350 cars out there. I could spend less money on a good running 305 car doing bolt ons and get much more out of it than a stock 5.7L car.

I know for a 100% fact, that you can get more than that reworking the air boxes and adding scoops to force air into the OE airbox. These made a substantial difference on the TPI 350 car I built and tuned. .

Camaro 85-92 TPI Ram Air Boxes - Hawks Third Generation (hawksmotorsports.com)Camaro 85-92 TPI Ram Air Boxes - Hawks Third Generation (hawksmotorsports.com)

My 83 G20 had a Camaro LT1 1LE elbow and Moroso LT1 CAI drawing in air from the front wheel well when it was TPI. That intake system was good for over 400 hp. The stock 3rd generation air filter boxes are horribly restrictive by comparison, but atleast they can be addressed and cool air funneled into them easily.

Aaron R.

I smell clay bar residue.....

Tom 400 CFI

Hey LOOK! ....A SQUIRREL!

Tom 400 CFI

As a smart guy I know once said: I don't know everything....but I know more than you!

I've seen plenty-a-305 go 12's. What's that got to do with the price of bread? That has absolutely nothing to do with the discussion that was happening about pole-vaulting 305 3rd Gen's. As you were, my man.

dmccain

iTrader: (2)