What's a decent redline for a 305 stock (forget about powerband, I'm just wondering what it'd blow up at)? People are saying 5800? Mine has a redline of 4800 on the tach, and that's where it shifts

 

I had mine past 6K for about a minute trying to blow up my 305 and it didn't die. I just held the gas pedal to the floor.

 

The maximum useful rpm is generally what knowledgeable people use as a redline. With a 305, due to its weak cam, heads and exhaust system, that is no more than 4500 rpm.

 

I swapped a TPI 350 cam (and new springs) into my TBI 5.0 Formula and tried to clean up the heads (years ago when I was "learning" as fast as my wallet would allow) and the car would run to about 5500 (I won't swear it made much power there, but it didn't seem to drop off much either) and I used to power shift it against a 5800 rpm limiter (shift light at 5600, limiter at 5800). I'd not run it so hard now (if I were doing that again) that I've got a better background in this stuff (this was 11 years ago or so), but it went 60k before I finally spun a rod bearing (at 158,000 miles). So, though I don't recomend doing what I did, it did stay together for a good while (to answer your question).

But, Sitting Bull is correct:

"The maximum useful rpm is generally what knowledgeable people use as a redline. With a 305, due to its weak cam, heads and exhaust system, that is no more than 4500 rpm."

With my cam swap, I probably should have kept it to 5000 rpm.

 

Do our cars have rev. limiters?, and a couple days ago i missed a speed shift and it revved wayyyyyyyy up, is that bad to rev it that high for just a sec?

 

They don't have rev limiters. I had an MSD 6AL on mine with the limiter.

Over revving a motor can bend pushrods, float valves, and worst case, the valves can hit the pistons and be bent. This is assuming you over rev it enough to float the valves and such. So, it can be very bad, but you probably got away with it.

 

Well one time I finally got my carb tuned and I hit it off the line and she pulled HARD till I looked at the RPM gauge and it was reading 5500rpm and she was still pullin like a bear that was the only time I did that. I did hit 6000 once, I missed a shift

 

Actually valve float starts around 5,200 or so...you just cant hear it; its caused by weak seat presssures...the worst will be breaking the crank or if your lucky spining a bearing...the 305 "Redline" is as follows...remember this is for the lower end.

Block bore = 3.740”
Crank throw: 1.74” => stroke = 3.480”
Displacement = 305.8 cid


Maximum RPM calculation:
Mean piston speed < 3500 ft / min for cast crank & rods
(Mean piston speed < 3800 to 4000 for forged crank, heavy duty rods & main caps)
mean piston speed = stroke * rpm / 6
=> maximum rpm = 3500 * 6 / 3.48” = 6034 rpm
mean piston speed @ 6400 rpm = 3.48 * 6400 / 6 = 3712 ft / min



The 350 would be slightly lower due to the increased mass...the LB9 rotating assembly is very close to the LT1 assembly which is substantially lighter then the L98 assembly

 

So your sayin the max rpm for a factory 305 is 6000rpms before the crank goes out the pan right?. If valve float happens at 5200rpm then I must have better springs in my 305, I know the cam was changed.

 

well 6 grand before the harmonics start to cause havoc..a few missed shifts to 6k wont be much but floated valves but keep doing it and your gonna break the crank or spin some bearings at the very least..like i said about the float, itll start around 5,200 or so but you cant hear it untill around 5,800-6,000...even then you have to know it sounds like...think of the sound a revlimiter makes but only the motor still pulls SLIGHTLY, or the sound of a motor "breaking" up on the top end

 

There is NO WAY a stock LG4 305 3rd gen that is being driven on an actual roadway is going to hit 6000 rpm. It would take forever to get there and would fall apart somewhere along the way.

 

I have a '87 IROC with TPI, LB9 and a 5 speed.(215 hp version)
Redline on this application is 5500 rpms.
And it stops making power around 4800 rpms.
My '84 H.O. made power a little higher.

 

Come on guys, I shift at 5800 with no fears all the time...wait--I've got an LT1. I love rubbing that in Brant.

Anyway, my dad held the 305 to 5500 when we were buying it to make sure no high rpm misses or whatnot. Held it for around 3 seconds. I could've seen 6k, easily.

Sitting Bull: It doesn't take that long to get up there. My LO3 goes to 5k very quickly and isn't much different than an LG4. I'm just afraid to go that extra 1k because my motor has 140k on it.

 

Corey---I hate you. 'Nuff said. :P

 

I own a Camaro with an original LG4. Yes you can get it to 5500 rpm but it will crawl up there and just wheeze like crazy along the way. If it holds together to 6000 rpm, that will be one of very few times it does it. The stress load on the reciprocating assembly increases enormously from 5000 to 6000 rpm. That's why the factories use forged and stress relieved parts in V8s that are going to see that rpm range.

Like I said, with an LG4 305 the useable and sensible redline is 4500 rpm. Period.