what are the cam specs on the stock buick 350 1973 2bbl?

It would be nice to know for comparison to cam upgrades. Does anyone have that information I cant find it anywhere.

 

It's complicated.

Others here will offer you advice on what to 'upgrade' to.

 

I do not know how acurate this is but here is what someone claimed the 70 cam specs out at:

ad.dur. intake 282, exh .304 int.lift .3818, exh.lift .3984. This is 1970 315hp specs.

 

I like that....:laugh::laugh::laugh::grin: you don't need those specs anyway.

 

Wow, 282 duration ,that's pretty stout for a factory cam. Find it hard to believe. I was thinking more like 250.

 

Most likely that is the "advertised" duration not the duration at 0.050"... It must be WAY lower than that at 0.050" .

 

I would like to see what the same cam would do with more lift . maybe Gary would know. I think it just ups HP output some.

 

Believe it or not, all the stock cams were less than .400 lift. They were all asymmetrical lobes that didn't need to overshoot the lift in order to reach the 350's GSpot :Brow:.

They did this by increasing the ramp speed as the valve opens, and slowing it as it closed. This allows the valve to stay open for the maximum amount of time where the lift needs to be, making sure the cam lasts longer than 50,000 miles.

Stock Buick 350 heads don't flow past .400 lift for intake or exhaust. You have to port them to get them to flow up to .450 and hog them out to get past .500 lift.

The dynometer simulator shows petty increases in power when you bump the lift on stock cams, even to .500 or more lift. Why? Because everything that needs to happen is happening below .400 lift! ou:

Interestingly, when you decrease the lift below stock specs (as in a wearing camshaft scenario) petty decreases in power are also observed, up to a point.

This is all thanks to the engineering designed to maximize the flow within the .300-.400 area.

Duration is where it's at...

It is what determines the camshaft's symmetry and lobe intensity when dealing with stock lifts--which is to say, way, waaay milder than any aftermarket camshaft. Incidentally, the very thing that makes the camshafts last longer is exactly what makes them perform so well considering their size.

Aftermarket camshaft manufacturers have their work cut out for them to improve on existing engineering from OEM engineering teams. They certainly cannot improve on longevity, but power can be improved somewhat as long as you concentrate the powerband and cause the camshaft to wear out faster.

The brighter the fire, the shorter the life.

No one puts a stock camshaft back into an engine they're building for performance, so no one knows about the potential. Except for now...

The camshaft is engineered to accommodate vast changes in the engine's environment, from choked down emissions single exhaust catalytic converter 2v low comp engines with barely 175 flywheel hp to opened up, good flowing engines from intake to exhaust that produce in excess of 350 hp. Yes, you read that correctly.

Instead of changing the cam, change what's around the cam.

Otherwise, get an aftermarket early IVC cam to bump dynamic compression and efficiency if you don't want to change anything else.


Gary


P.S.-- yes, the stock cams had those durations at .006 lift, and around 190ish/210ish I/E durations @.050.

Like I said, they're complicated. The asymmetry of the lobes causes them to be at different LSA's and installed points at varying lifts. This is why they have extremely wide power bands and are flexible to their environments, while outlasting any other aftermarket camshaft design.

 

Gary, the duration specs on a 70 gs350 cam is kinda stout. What would more lift do(within reason) with slightly faster ramp profile say something 440-460 lift.

 

You could squeeze more out of it of course. Increasing the ramp profile would be done by increasing the durations @.050 and leaving the .006 durations alone. Bumping lift won't do much with the OEM lobe designs, though bumping lift on symmetrical aftermarket type grinds does, because it needs to in order to compensate for the weaker engineering.

If you port the heads to flow at higher lifts and then bump the lift on the OEM style lobes, you'll transform the engine, however...

This is what has been done on my roller grind 'Stock' camshaft when using heads that do not yet exist (hint hint).

Gary

 

When talking OE cams, per my GM parts catalog the 350 used the same replacement cam PN (1237736) from 68 to 74 with 2 exceptions, 71 5000 series (1237651) and 74 Calif (who cares). Could not find any specs in my 72 service manual. As Gary said duration would be at .006" lift as that's how it was done in the day.
It does list 1970 Hi comp and 1970 low comp on separate lines but gives the same PN. That leads me to believe at one time the 1970 hi comp did use a different number.

 

so all the SBB 350 stock cams were the same. Wow.

 

in my books the lift on a 350- 1970-1972 is 382-398. on one used cam the club measured the lift on a 455 stage 1 was 415-445, duration@.050 210-222. close to what Larry stated. of coarse the factory advertise duration was NOT measure at .006 .it was at .002 or .004 thousand can not remember.

 

No they were not the same over the years, there is just very little documentation of the camshaft specs available. I will ask Dennis Manner if he can find the specs.

 

duration @.050 on a stock 350 would be about 192-196 degrees, napa gave me the numbers long time ago and cant remember exactly, but I know the numbers at the time made sense. do not go by factory advertise numbers.

 

Of the three stock cams available now, you have two from Melling and one from Federal Mogul. I saw one from another manufacturer, but I think they used the Federal Mogul one...

The larger of the two from Melling is from years '68-'75, while the smaller one is from years '76-'80.

The Federal Mogul cam says it's for all years, but this is simply the replacement cam. The actual camshafts were a bit different over the years, varying slightly up to around '75 when they got pretty small to try and help out with emissions, though the differences weren't so much for 2v and 4v as they were for car weight and transmission used.

Even so, the differences were pretty small. Federal Mogul took cam sizes ranging from the earlier years when the cams were their largest and averaged them out and made their rendition of the 'stock' OEM camshaft. It is a bit larger than the one used in '68 and '69, but slightly smaller than the ones used in '70-'72.

It's interesting to note that the camshafts didn't start changing around until 1970. In '68 and '69, the camshaft was the same for all 350's, high and low comp, 2v and 4v.

The two from Melling have part numbers SBC-5 for the larger, and SBC-11 for the smaller, while the part number for Federal Mogul's cam is CS-647.

I know it shows 'SBC' in the part number which may make you think it's a chevy cam, but it's Buick 350 specific.

Here's the cam specs for the Melling cams:

SBC-5: produces less torque (about 10 ft. lbs.) than the Federal Mogul cam, but has a slightly higher powerband (but similar hp). This is Melling's GS-350 stock replacement cam.

276/297 @.006
191/208 @.050
.242/.252 lobe lift
.375/.391 @1.55 rocker
IVC @75*

SBC-11: is the smallest stock cam of the three. This is the one that would have trouble turning past 4200 RPM. This is Melling's general purpose '76+ cam.

241/261 @.006
172/182 @.050
.207/.216 lobe lift
.321/.335 @1.55 rocker
IVC @50*

It's important to note that the extremely low IVC point of 50* would indicate higher DCR for the 8:1 pistons, meaning that even this tiny cam would have a much better matchup to the low compression than the SBC-5 would.

Federal Mogul: my personal favorite of the three, this cam produces the most power of all stock cams, with a more reasonable IVC point matched up to 'high comp' pistons and a well rounded powerband. Federal Mogul shows this as the one and only replacement cam for all Buick 350's, ranging from the late model, low comp 2v engines choked down with emissions and single exhaust to the earlier high comp 4v higher flowing engines. This cam in a cleaned up environment with a high flow intake and large tube headers produced 396 ft. lbs. and 353 hp.

270/293 @.006
189/208 @.050
.243/.253 lobe lift
.377/.392 @1.55 rocker
IVC @71*

All LSA's and install points vary per cam. They show a retarded position @.006 while showing advanced @.050. All retard/advance positions are built into the cams, and the stock timing gears have zero retard/advance built into them. I don't know what it was in the past, but this is how it is now.

All one would have to do is just make sure the compression matches the IVC point as closely as possible, and put the thing together using the stock timing gear set. The camshafts and timing gear sets are matched up as sets so there is no guesswork or extra hassle in building, and are guaranteed to have proper valvetrain geometry.

You use stock valve springs and dampeners (that you don't have to swap out after break-in...) that will rev to 6000+ RPM with the gentle lobe intensities. Used with a set of Crower camsaver lifters, and you have maximum valvetrain longevity.

You can also get away with using the milder oils that are common today, with less ZDDP, though it is still recommended to use a higher content than overhead cam engines. Around 950-1050 ppm should do the trick. The 'high mileage' synthetic oil from Mobil 1 is supposed to have 1050 I think, and you can get it all day long at Wally World.


Gary

 

Correct. I think it was .002 and this would change things a little, though not really enough to make much difference outside of a few degrees and less than .1 DC point in terms of finding the proper install point.

It can matter when you're splitting hairs, but even I draw the line somewhere :laugh:

TA's rendition of the stock Stage1 455 cam sits at .406/.441 lift and 210/224 @.050 with a 113* LSA I think. Pretty close. But then they scalp the .006 (or .002) durations to tighten up the lobe intensities over the stock cam, which gives more power and lower RPM (a little), at the cost of camshaft durability. Coupled with those high pressure springs, and you might be able to squeeze 60k-80k miles out of it.

I realize this is fine for people who don't use their 1970 GS 455 as their daily driver... :grin:

I believe all TA's cams are symmetrically lobed also. This would make a big difference between the actual OE camshaft and the aftermarket one (OE being the better one).


Gary

 

Gary, tell us more about symmetrically lobe cams, the bad and or the good. thanks

 

With smaller cams (lower lifts and shorter durations), causing the lift side of the lobe to be angled a bit steeper creates a faster lift/ramp profile, which causes the valve to open faster, while on the closing end of the lobe the distance between lifts is increased so that the valve closes slower. This permits the valve to stay open longer with shorter lifts and durations, maximizing the time spent open within the desired window of operation. It also creates a gentler closing for the valve seats. The valvetrain doesn't need as much spring pressure to operate and maintain stability within the operating range of the camshaft. This creates a gentler environment for the entire valvetrain which results in less wear over longer periods of time.

This also creates a wider window for dynamic airflow to take advantage of gas movement past partially open valves dependent on engine RPM and airflow restriction/demand. In other words, the more the engine is restricted, the lower the RPM powerband and less power; while the opposite is true for a freer flowing--albeit higher velocity--environment.

This is of course true for all camshafts, but is more prominent with asymmetric lobe designs with gentler ramp profiles.

The only real 'bad' aspect about it is that aftermarket parts vendors sell less parts over time, which hurts profits. Another potentially 'negative' effect is the engine won't make as much power as larger cams take better advantage of higher flowing heads. For a street driven car driven daily though, this is about as good as it gets when everything is considered using basically stock components that have been massaged for optimum performance.

As camshafts get larger, the lobes tend to become more symmetrical, since the need for asymmetric lobe design wanes, because there's simply less time and distance between events for it to really matter. You could still gain from asymmetric lobe design with larger cams if the camshaft radius was increased.

Gary