Open chat thread for Buick 350 Camshafts

Whoever engineered that stock camshaft didn't just pull numbers out of thin air. The numbers are there for a reason. I find it of particular interest where the valve timing events are located in relation to the piston, at .006 and .050 lifts, and what happens inside the engine while the air is flowing at lower RPMs and then begins to rev up past 2500-3000...things start to change, based on the airflow and time it takes for air to bleed by lower lift openings.

The cam could be optimised a bit for more specific parameters, though the way it is now is great for a very wide range of applications, ranging from rock bottom low compression to 10.5:1.


Gary

---------- Post added at 08:10 PM ---------- Previous post was at 07:50 PM ----------

The cam listed at Sealed Power that I'm speaking of is called the 'GS Buick 350' camshaft on some sites that purvey it. According to some research I've done, the cam is actually a little bigger than the '68 and '69 stock camshafts.

Mismatching head porting with compression/camshaft is (I would imagine) a common mistake with the 'bigger is always better' mentality that is running rampant.

Stock heads with only runner cleanup work, mild guide boss contouring, and exhaust runner polish would do wonders in an otherwise stock environment. Using those "Stage1" valves (1.92 int/1.55 exh) in this same scenario will improve power as well, since by using a stock camshaft the lift won't be increased, yet the flow WILL increase due to the increased size of the airflow curtain around the valve--without the negative effect of reducing velocity (which is the real reason why ported heads 'kill' an engine that doesn't have a camshaft/compression optimized to support them).

This 'large valved, stock cammed' environment would also increase the 'blowby effect' from .006 lift to .050 that I spoke of earlier, increasing the RPM that would be needed to offset it. What this does is essentially widens the power band even further, all without changing to an aftermarket cam.

The aforementioned head work could be done by a backyard amateur. It doesn't take experienced porting knowledge to run a deburring tool inside some runners and give them a good cleaning. Just some basic mechanical inclination (which the person is surely to have in the first place by working on any engine/car). Look at some pictures of untouched and cleaned up heads. Notice the casting imperfections that need to be smoothed over. Notice the sharp, abrupt edge on the valve guide bosses that can be rounded off a bit (more experience is a plus here for optimal contouring, though a simple smoothing over the sharp edges would still be a benefit in any case).

Use a rough sanding wheel for intake and exhaust for cleanup, then use a fine sanding wheel for exhaust after it's cleaned up to get it as smooth as you can. Same for exhaust manifolds (if you use them) as far down in as you can go on the intake side of them that fits to the heads, then same with exit port.

Sand and polish the combustion chamber on the heads as smooth as you can to help eliminate hot spots for detonation.

It's not complicated (though will be a bit time-consuming), and will provide big benefits.

Gary

 

A hydraulic roller version of the stock cam would make for a very spirited 350! LOL

 

Imagine what a stock cam would be if Buick still made the 350. Today's profiles in roller cam .

 

Imagine no longer. One's in the works by yours truly.

It will go nicely with those aluminum heads and fuel injection. :TU:

Obviously, it'll be larger...quite a bit larger...but will last a very long time and will be pretty mild in roller terms. A 'crate motor' wouldn't be out of the question with aluminum heads, aluminum intake with fuel injection, shorty headers, roller cam, hyper pistons, smooth idle, great vacuum, good gas mileage, good power, and a 200,000 mile limited warranty.

Gary

 

200,000 mile warranty? Does that cover turbocharged engines. We can run it against a Cadillac CTS-V

 

I'm thinking N/A engine. With the parts I mentioned earlier, the engine wouldn't need anything other than regular oil changes and tune-ups for a very, very long time. With hyper pistons and a roller cam, engine wear would be practically non-existant when well maintained.

Ever tear down a well maintained factory 350 after 150,000 miles? Wear is minimal, and can be freshened up and put back together for another 150,000 miles. This is with a flat tappet stock cam.

I have complete confindence that stock flat tappet cam would last 200,000 miles easy before needing replacing. I've known people who've had over 300,000 miles on one (low comp engine) and it was still going strong.

Regularly maintained oil is the secret. Plus the (stock) Buick 350 is just engineered to last.


Gary

 

Here's my rendition of a Buick 350 "Stage1" stock camshaft:


GF 199-18H "Stock Stage1 Cam" Theoretical

I took the stock cam's specs, increased lobe lift by .010" on both I/E,
increased duration @.050 by 10* for both I/E, decreased duration
@.006 by 10* for both I/E, which tightens the lobe intensities by 20*
for both I/E and makes IVC @.050 the same as the Crower level 3 cam,
which gives a better matching compression pattern when this cam
is installed 'straight up' (installed @66* IVC@.050), with the same
dynamic stroke of 2.95" as the Crower level 3 cam.

I left the camshaft's LSAs and centerlines the same as stock camshaft,
which gives a similar asymmetrical lobe design, but with more spunk,
better vacuum, better gas mileage, with minimal impact on
longevity. Camshaft should give an extra 200-300 RPM on power band
over stock cam, while being able to retain stock valve springs.

Camshaft designed for 66* IVC installation, which puts the asymmetrical
lobes at 3.25* advance install @.050 and 1.75* retard @.006, same as
stock camshaft.

For best results, install stainless steel swirl polished "Stage1" valves
for better flow @ low lift while retaining velocity, along with runner/bowl
cleanup and exhaust polish on both heads and exhaust manifolds.

Use of a small stall will be of benefit, though not completely necessary.

Enjoy.

GF

.392/.408 @ 1.55 lobe .253/.263

260/283 @.006 116/112.5 I/E 114.25 LSA
1.75*R

61/65 lobe intensity

IVO is 14.0 BTDC ( - indicates ATDC)
IVC is 66.0 ABDC
EVO is 74.0 BBDC
EVC is 29.0 ATDC ( - indicates BTDC)
Overlap is 43

199/218 @.050 109.5/116 I/E 112.75 LSA
3.25*A

IVO is -10.0 BTDC ( - indicates ATDC)
IVC is 29.0 ABDC
EVO is 45.0 BBDC
EVC is -7.0 ATDC ( - indicates BTDC)
Overlap is -17

Power Range (Shift Point): 1500-4400 (4900-5100) "1500-5000"

Wide power band, with HP peaking around 4400-4600 RPM, fading
slowly to 5100 RPM, then nose diving somewhere around
5300-5600 RPM.

Peak torque should be around 3300-3500 RPM, with a very wide
torque curve, particularly from 1800 to 4800 RPM. Main torque
focus will be between 3000-4500.

For use with premium pump gas:

Static compression ratio of 10.14:1.
Effective stroke is 2.95 inches.
Your dynamic compression ratio is 8.00:1 .
Your dynamic cranking pressure is 158.97 PSI.

Static compression ratio of 9.81:1.
Effective stroke is 2.95 inches.
Your dynamic compression ratio is 7.75:1 .
Your dynamic cranking pressure is 152.55 PSI.

Static compression ratio of 9.48:1.
Effective stroke is 2.95 inches.
Your dynamic compression ratio is 7.50:1 .
Your dynamic cranking pressure is 146.16 PSI.

For use with regular pump gas:

Static compression ratio of 8.51:1.
Effective stroke is 2.95 inches.
Your dynamic compression ratio is 6.75:1 .
Your dynamic cranking pressure is 127.24 PSI.

Static compression ratio of 8.18:1.
Effective stroke is 2.95 inches.
Your dynamic compression ratio is 6.50:1 .
Your dynamic cranking pressure is 121.02 PSI.

Static compression ratio of 7.85:1.
Effective stroke is 2.95 inches.
Your dynamic compression ratio is 6.25:1 .
Your dynamic cranking pressure is 114.85 PSI

 

To show the difference larger valves can make, I'd like to illustrate a few points:


Valve size comparison

Valve curtain standard valves I/E: 1.875/1.505 .469/.376

Valve curtain "Stage1" valves I/E: 1.92/1.55 .480/.388

Percentage increase from standard to "Stage1" I/E: 2.29/3.09

Numbers to multiply/divide by for percentage I/E: .9771/.9691 (97.71% I/E 96.91%)

Which is to say that if these size valves are used, the stock standard size valves are equal to 97.71% on intake and 96.91% on exhaust. This doesn't sound like much, but check this out:

Take the 'small' Crower level 2 camshaft as an example:

202/210 I/E @.050
.434/.436 I/E valve lift

Using these "Stage1" size valves, the increase on flow and duration will make the camshaft behave as though it was a bit larger. How much larger?

Simply take the .9771 for intake and .9691 numbers as division into the cam numbers.

202 duration becomes about 207, 210 duration becomes about 217; .434 lift becomes about .444 lift, .436 lift becomes about .450 lift. So the Crower level 2 camshaft now behaves as if it had these specs:

207/217 @.050
.444/.450 @1.55

Suddenly these small numbers don't look so small anymore, the camshaft behaves as though it was a bit larger, though no velocity on flow has been sacrificed, and the camshaft is otherwise unaffected (physically) which means it still wears the same.

Larger valves would be particularly useful on Buick 350 heads with low lift profiles in this regard, including the stock camshaft or other mild grinds.

Y'all can use these numbers for figuring out combinations you want with existing off the shelf cams or custom cams so you can get an idea which valves to use.


Happy hunting.


Gary

 

Gary, Not certain what you are calling valve curtain. Please explain.

Never mind, I looked it up.

When I do my calculations I work on the throat diameter. That is the restriction. You can put a 5 inch valve in and NOT increase flow if you have the same throat diameter.

The bigger valve will only allow more flow up to a certain lift point. After that the throat becomes the restriction. What the bigger valves allow you to do is increase the throat diameter to increase flow through out the entire lift range. The larger valves also have cut down stems to increase flow thru the throat area.

 

I'm glad you brought this up Steve, since I assumed people would know that if they wanted greater flow past a certain point, they would know to open the runners up more (including CSA and throat). For purposes of this example, however, I was referring more to low lift, mild cams. It may not hurt to open the throat up a bit anyway, though when using low lift cams, the valve won't be moving up much past stock lift (which is to say pretty darned low when compared to some of the 'performance' cams out there).

I don't recommend putting in the "Stage1" valves without any port cleanup and some contouring, at least.

Stock lift @1.55 is .377/.392 I/E. The "Stage1" stock cam I recommended is .392/.408 I/E. All within legal 'stock' parameters. I'd say much past this and increasing the throat would be a benefit. Remember that Buick used these 'Stage1" valves in the 350 over the years, just not all at the same time: they either went with larger exhaust or larger intake, not both at the same time.

This is the beauty of the larger valves in a 'stock' environment. They give better flow, maintain good velocity (at low lifts), and give the illusion of running a larger camshaft, while not having to do so. The valve can be any diameter, but if it only lifts so high, the charge flowing past it will maintain the same velocity. It's the volume of charge that it increases (up to a point, like you said) as long as the valve meets or exceeds the throat's capacity to feed it. Open the throat too much, and you begin to lose velocity and the valve again becomes the restriction...but then you have a head that flows beyond what the camshaft needs and will hurt performance when using that cam.

I think contouring is far more important than simply opening things up. While both go hand in hand together, for mild applications, it's best to remove as little material as possible, just enough to make sure everything's contoured well.

It's just something to think about. I know putting larger valves in will be an increased expense, and it would just be cheaper to buy a larger cam, but larger cams wear more. So, this is just another idea to chew on for those of us who like to think outside the box, if you will.

There's more to it than better performance over stock valves too. It's increased longevity since the valves are lighter and will make the vavle train more stable, even with the use of stock valve springs. They'll allow the engine to rev higher before valve float too. Stainless steel, undercut, swirl polished valves will flow more innately due to the design. With less material in the stem that 'outweighs' the increased material in the valve head, the valves weigh less, yet are stronger and provide a longer service life. Less weight = ease of valve opening and closing, easier on the seat, and requires less spring pressures.

So with stock springs and low lifts with cams that have less valve intensitites, will last a very long time and be very easy on the head seats. (I realize there's some redundancies here, as added emphasis)

Though it's more expensive, it'll create a very long lasting and surprisingly peppy 'stock' engine. Remember those stock racer guys (as you well know) are getting in excess of 375 HP out of their 600 RPM smooth idling, .392/.408 lift cammed engines with UNported heads...

...of course though their compression is high, matches the camshaft properly, and the durations and LSA's match the application. What a concept, huh?

Big Valves: it's not just for big cams anymore. :laugh:

Thanks for your thoughts! And as always, when you talk, I listen. Your smooth idling Buick 350 isn't going up against Ford and Pontiac big blocks in the finals for nothing. :TU:


Gary

 

A larger valve with a larger seat diameter will allow a better angle between the throat and the outside of the seat.
This moves the airflow direction away from the underside of the valve head and more towards the opening between the seat and the valve edge.
As a result there is more airflow with the same size throat and a larger valve.

Yes. However the max lifts involved in the discussion are around .400" where the curtain area does not exceed the throat area.

Paul

 

I think the amount of improvement would not be measurable or very minimal by just installing the larger valve and not opening the throat. Depends on how much "blending" is done.
Seems like when I did these same calculations several years ago, with the stock throat size , the throat became the restriction at about .380 lift. I'll have to look for my notes on this.

 

I just went through this with a cnc ported straight six head where a 2.02 intake valve showed a slight improvement at low lifts over a 1.94 valve with the same throat diameter. There was no difference in flow past .400" lift.

This was more of an FYI or an addition to your info. No argument intended.

Here's the interesting part. I went with the larger 2.02 valve to increase the shrouding between the valve and the adjacent combustion chamber wall.
I then pulled the chamber wall back to the cylinder bore scribe line where the spark plug hole is.
This created an exit guide from under the head of the intake valve that will swirl the incoming charge.

The port flow was doubled from the stock flow at .100" to .500" valve lift.

I'm sure your right about throat area = valve skirt area at .380" lift. I was just ball parking the figure at .400"

Paul

 

Paul,
Found my notes. It was lower lift than the .380 I guessed.

With the stock valve and throat size what I call the equalized point is .35 lift on intake and only .238 on exhaust.
With the stock valve and the throat cut to the dia. of the bottom of the seat it moves to .375 int, .285 ex.
Here's where it gets funny.
With the big valves and the throat cut to the dia. of the bottom seat it is .372 intake and .282 exhaust. It appears the increased area of the larger valve cancels the greater area in the throat. If I explained that correctly.

You also have to remember that more flow area available at low lift is not going to help that much because the piston is moving very slowly or not at all when the valves are starting to open and near closing. At TDC and BDC the piston is not drawing any air while it dwells at top and bottom.

Granted at 5000 rpm these events are quit different and port flow is much more than area.

How did your port flow double?? That sounds like way more than it could be possible.

 

Most cams don't typically open and close @TDC or BDC (mild cams don't for sure)...

There's plenty of movement going on between .050 and .006, particularly with cams that have low lobe intensitites (which mild cams tend to have), much less between .050 and .400 where the real action is taking place.

According to flow bench marks I've seen on Buick 350 heads, stock untouched heads don't flow past .400 on intake, and only gain about 2 CFM from .400 to .500 on exhaust. Simple runner cleanup, guide boss contouring, mild throat work (mostly just blending and smoothing) then smoothing turn radiuses a little, and polishing exhaust won't move those numbers much higher, as I've seen benchmarks with heavily ported heads that had modest gains from .400 to .450 on intake, peanut CFM gains from .450 to .500, and nose-dived after that. Exhaust tended to be about .050 higher than intake.

Obviously it just depends on how the heads are ported as to what sort of results will be had, but the point is mild touch-up and blending won't move the flow numbers much past .400, if at all.

Put the throat wherever it needs to be, but larger valves will definitely be a help with mild cams. Performance isn't the only benefit they afford, as I mentioned earlier in at least one post.

The cam that's in your engine right now (Crower level 3) has timing events that may reinforce your descriptions, though cams that are milder (which is what I'm talking about) will see plenty of air movement (past the valves) past TDC and BDC.


As always, thanks for your thoughts, Steve! You too Paul! You guys rock!


Gary

 

My point is the valves open NEAR TDC and close NEAR BDC when the piston is hardly moving and the valve barely open. When the piston is moving fastest (midstroke) the valve is NEAR peak opening and the flow is needed the most then.
Any flow increase is good, but the most bang for the buck is at midstroke. Like you said they don't flow well after .400" lift so that's where they need help most.
I've heard it said " you're tripping over dollars to make cents"

 

Gary thanks for your reply

Steve

Thanks for posting your notes.

Just for fun I took a look at the Ford 300 six ported head sitting here.
With the 2.02 intake valve the equalized point is .354.
With the 1.94 intake valve it would have been .368.

The smallest diameter of the throat is 1.69" and is .350" down from the center of the valve seat.
Looking into the throat you will see a fairly good funnel shape from the seat to the smallest throat diameter.
This gives the airflow plenty of opportunity to turn towards the opening between the valve head and seat
and the resistance to airflow past the edge of the valve head is reduced by some significance.
As a result you get better airflow without increasing cross sectional area of the throat and you get the benefit of higher velocity. I know you understand this but just posting it anyway.

The reason for the ability to double airflow on this head is because the stock bowl area is terrible and the stock port flows are very low.
The stock intake flow on a previously tested head was 32.7 @ .100" up to 101.5 @ .500"
The ported head showed 59 @ .100" and 204 @ .500"
The story is similar on the exhaust side.

I wished I'd taken a picture of the stock port but here is a picture of a finished port.

 

The only place they're near is TDC @.050. At .006 they're much farther out, moreso with mild cams.

At BDC, valves are starting to open and close way before and after. Your Crower level 3 cam's exhaust valve starts to open at .006 @ 76.5* before bottom dead center, and is at .050 @46* before bottom dead center. Intake valve starts to close at 33* @.050 after bottom dead center, and is at 66* @.006 ABDC, for examples.

Indeed sir, they need help since they only flow well up to .400, hence the increased valve size! :TU:

As long as the throat and CSA can feed the larger increase (which they will all the way up to almost .400 even in stock form), power increases will be realized since with low lift the velocity of flow won't be sacrificed, like it is when the valve opens further up.

It's not a day and night difference, but I feel pretty confident the difference will be felt, even with a stock camshaft. Putting in the "Stage1" stock camshaft I suggested or one similar to it would show even more improvement.

The whole point to this entire thing is large valves benefit low lift cams as well as high lift cams, providing the larger valves are accommodated for optimal performance.

Even Buick put in larger intake valves for more performance using stock camshafts in some years and with some 350s.

This isn't to say that if someone doesn't use larger valves that their engine will suck, obviously. With larger valves though, you can have a 'larger camshaft' without the larger camshaft.

It'll be more expensive, sure. All this has already been discussed earlier.

Not picking on you Steve, you know I respect you. I'm enjoying this opportunity for discourse. Peace bro.



For reference:

Crower Level 3

.446/.468 @ 1.55 lobe .288/.302

276/281 @.006 66/61 lobe intensity

IVO is 30.0 BTDC ( - indicates ATDC)
IVC is 66.0 ABDC
EVO is 76.5 BBDC
EVC is 24.5 ATDC ( - indicates BTDC)
Overlap is 54.5

210/220 @.050 108/116 I/E 112 LSA
4*A

IVO is -3.0 BTDC ( - indicates ATDC)
IVC is 33.0 ABDC
EVO is 46.0 BBDC
EVC is -6.0 ATDC ( - indicates BTDC)
Overlap is -9



Gary

 

Gary,
Should your IVO number @ .006 be -33?

Theres no doubt the bigger valves help across the board, I'm just saying it's minimal at extreme low lifts. I don't see any down sides to using them.

I've never heard Buick used a larger valve on the intake side, what years did they do that? I knew they went up on the exhaust around 75.

Paul,

I was thinking Chevy 6 not Ford. Ford ports are horribly small. Now I see how you doubled the flow. Great job. I think the Chevy 6 has better ports more like a small block. What type of car are you running that in?

I'm not angered by these discussions and hope no one else is either. This is how we learn and improve the breed.

 

Negative number represents after top dead center, so the '-3' you see for IVO @.050 means 3* ATDC.

It opens at 30* @.006 before top dead center.

The 33* is after bottom dead center @.050, then moves to 66* ABDC (where the dynamic compression is generally calculated and shows the dynamic stroke as well).

Air has mass (particularly when it's infused with fuel), so there is a bit of momentum going on before and after TDC and BDC, even though the piston isn't moving much there (and is even reversing directions while the valve relating to the stroke is still open). This helps with dynamic gas movement throughout the combustion cycle.

The fact that the piston is moving slower on the lower 'half' of the stroke than it is on the upper 'half' indicates part of the reason why the valves are opening and closing so far away from BDC--so you're not too far off the mark with your logic.

At very low lifts it wouldn't matter where the peak lift was when comparing durations @ particular lift, though raising lift keeps the valve open longer in the desired range, which is ideal for higher RPM, larger port size (and less velocity) applications--though velocity will increase as RPMs go up of course, as more air demand gets placed on the runners/CSA/throat etc.

This is where larger valves help at these lower lifts, flowing more air while maintaining velocity.

Also to consider is the very wide lobe intensities on milder cams (and the stock cam). There's more time (duration) between .050 and .006 in these instances, and with the relatively short peak lift, a gentler slope from .050 on up. This would not only make the cam and lifters last longer, but would enhance the amount of time the cam exists at (and near) peak lift, without such a sharp point when compared to higher lifts with similar durations.

This may be considered splitting hairs in terms of performance, since the performance gains may not be jaw dropping, but the longevity would see much enhancement (which can't readily be seen) so it's more subtle and less attractive to some who may be more interested in lopey noise, in the respect that having added performance doesn't necessarily have to come at the cost of longevity.

Then there's the pricetag. It's not cheap having a Stage1 conversion done professionally. You may be able to get it done cheaper elsewhere and do all the port/polish/contouring/blending yourself, which will cut down on costs of course, and it may not be attractive to those who feel it's unnecessary or out of budget limits.

It's just an option, and isn't a waste of time for those who may want to consider it as an alternative. :TU:

It was later on, I think in '77 and '78 or something. I don't remember exactly, and I'm not 100% certain on the validity of the source, so admittedly, this may just be something that was done with the 'stock racers' and their class rules.

I do however remember (Denny Manner I think it was? Not positive) saying that the increased exhaust valve size was more for emissions and that it didn't really improve power much, unlike the increased intake size.

So THAT is a whole other consideration...and may explain why those guys in Kentucky use the (even larger) 1.94 intake valves and retain the stock size 1.5 exhausts? Something to think about.

In any case, the best bang for the buck is to simply use the stock valves and massage the heads a bit. Most of the cost will just be your own time and elbow grease.


Gary