What cam to use in a 318

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At the point the exhaust vavalve opens, the cylinder pressure is still 70PSI to 120PSI. That exhaust exits past the barely open exhaust valve at supersonic velocity for a fraction of a moment until the valve opens more and the pressure has bled off. This high pressure and velocity in a tuned exhaust eventually causes a negative cylinder pressure about the time the intake valve opens.
With a tuned intake there can be a slight pressure increase as the intake valve lifts off the seat. This is very minor as compared to the exhaust when considering a NA engine. Basically the best we can consider in a NA intake manifold is atmospheric oressure of 14.7 PSI. Therefore opening the intake as much as possible is generally beneficial.
As per David Vizard, the flow is pretty much area ruled until the valve lift gets to or exceeds 0.25D. At 0.25D of the valve the area of the valve head and the area of the circumference of the seat at said lift are the same. Once you get the valve open farther than 0.25D lift, the port takes over as the controlling factor instead of the seat area between the head and valve. With this a 1.9" intake valve is at 0.25D lift at 0.475". A cam that only allows 0.425" to 0.44" valve lift remains restricted in flow by the seat, not the port flow capability. With this example of intake valve diameter, a cam profile combined with a rocker ratio to give intake valve lift of 0.500" to 0.510" gets the valve out of the way to allow the port to limit the flow. Now this is not much in degrees of crank rotation or milliseconds, but does improve the engine performance noticably. You have not affected cam duration by more than a couple of degrees at 0.100" to 0.200" lift and not changed overlap at all with a higher ratio rocker, so idle quality and low speed driving are not effected.
Getting the exhaust seats cut or ground to 40° greatly aids blowdown and the strength of the exhaust pulse tuning. Using the 40° seats on the street allows you to use less exhaust timing and possibly a single pattern cam for more low speed torque, which is what low speed driving around town entails.
For the race crowd that may be ready to come unglued on my comment, yes at high lift 50° and 55° seats do provide higher flow. Another advantage in a high RPM engine is the steep valve angle allows the valve to wedge into the seat better, preventing valve bounce and thus promoting better seal.
A street engine that normally putz's around town and a race engine are two different animals for design criteria.

How many 50 and 55 degree valve jobs have you tested?

It can’t be many or you’d know that lift doesn’t make a pinch of **** difference in what seat angle you use.

I know you read that and heard it, but it ain’t true.

Anything less than a 45 degree seat is losing power.
 
I'll never understand why Mopar guys still use 3/8 valves. What's the length of those valves by the way?
The length is fairly close to the Chev and Ford valves. The advantage of the LS valves is low cost and the 8mm stems keeps the weight down. 8mm is about 0.002" more than the Magnum valve stems but I bet the Chev cost less. You could install Magnum valve guides and hone them to get valve stem to guide clearance just right, kind of along the line of file fit rings.
The next important topic is spring installed height. On the early Ford 289 heads (my 1966) the installed height is 1.65", so the Chev beehive springs will not work. Most of the later SBF heads are 1.78" to 1.79" installed. Close enough to the Chev 1.8" installed height.
My understanding is the SBM are pretty much using the 1.8" installed height or very close.
So using the Chev valves gives a bit larger valves depending on the heads (other LS have 2.0"I and one has 1.61"E valves) at a pretty reasonable parts cost with the rest of the parts included. You could purchase new valves and then grab 4 matching LS heads on a Pick n Pull sale day from low mileage engines and take the springs, retainers and locks. Probably sell the heads for more than you paid. Get the springs checked and use the best 16.
 
How many 50 and 55 degree valve jobs have you tested?

It can’t be many or you’d know that lift doesn’t make a pinch of **** difference in what seat angle you use.

I know you read that and heard it, but it ain’t true.

Anything less than a 45 degree seat is losing power.
You are correct that I have not tested. But I follow David Vizard and he has probably forgotten more **** than you ever shovelled up in the back yard.
You want to argue, go argue with DV!
I knew that comment on using 40° seats would give somebody a wood, and I did make comment on the difference. I guess you got your wood before reading that far.
 
You are correct that I have not tested. But I follow David Vizard and he has probably forgotten more **** than you ever shovelled up in the back yard.
You want to argue, go argue with DV!
I knew that comment on using 40° seats would give somebody a wood, and I did make comment on the difference. I guess you got your wood before reading that far.


Ok, that’s what I thought. You are talking out your *** like an expert when you aren’t.

Worship DV all you want. The dumb *** still thinks a radius on the intake seat makes more power because his flow bench told him so.

He’s also the clown that was promoting 30 degree seats for “low lift” heads. He was wrong about that dumb **** too.

My testing says you both don’t know ****.

Rather than running your mouth, why not go test it and PROVE me wrong.

I won’t hold my breath.
 
Ok, that’s what I thought. You are talking out your *** like an expert when you aren’t.

Worship DV all you want. The dumb *** still thinks a radius on the intake seat makes more power because his flow bench told him so.

He’s also the clown that was promoting 30 degree seats for “low lift” heads. He was wrong about that dumb **** too.

My testing says you both don’t know ****.

Rather than running your mouth, why not go test it and PROVE me wrong.

I won’t hold my breath.
Well bomb, you are welcome to your opinion and your dumbass attitudes.
Keep enjoying pissing in others korn flakes.
I will go with what DV teaches. What your learning curve reveals to you is your property. The years of experience DV has accrued tells me he may have learned a few things. Consulting for F1 teams like McLaren and Cup Car teams indicates his knowledge may be valueable than yours.
While your wood is still stiff from this topic I suggest you go accost your wife.
 
Well bomb, you are welcome to your opinion and your dumbass attitudes.
Keep enjoying pissing in others korn flakes.
I will go with what DV teaches. What your learning curve reveals to you is your property. The years of experience DV has accrued tells me he may have learned a few things. Consulting for F1 teams like McLaren and Cup Car teams indicates his knowledge may be valueable than yours.
While your wood is still stiff from this topic I suggest you go accost your wife.


I’m glad you bought his line of bullshit.

I’m not pissing in your corn flakes. I’m telling you the Truth and you don’t like it. Well boo hoo.

I have never liked blind following anyone. You can test just like I do. But don’t do that. Your idols will come crashing down.

Keep posting nonsense and I’ll keep correcting it. And I have the testing to back it up.
 
Well, yes to a point. If swapping out the cam it costs no more to order what your engine really needs. The other things I propose as options. If valve to piston clearance is determined to be adequate, higher lift rockers can be installed quickly and easily provided the appropriate valve springs were installed with the cam.
The head upgrades is another minor matter that can be done down the road, possibly as a recondition is required. This narrows the costs difference, which makes the upgrades more affordable. Using readily available Chev valves, springs, retainers and locks also keeps the costs closer.
Just presenting thoughts that someone may find useful.
have you priced machine work lately? and lead times??

i don't know where you are, but in my neck of the woods it's pricey and the lead time is tremendous.

anyway for the type of work you're describing, you'd be in aftermarket head territory-- or darn near.
 
have you priced machine work lately? and lead times??

i don't know where you are, but in my neck of the woods it's pricey and the lead time is tremendous.

anyway for the type of work you're describing, you'd be in aftermarket head territory-- or darn near.
No arguements there junkyard. Other things to consider are where are those heads produced and developed. I realise many companies are doing the design work in the US but having the castings done in China due to costs, and then doing machining in the US. Some saving but even CNC machining local is more expensive.
They can have the parts cast, machined and assembled in China at considerable saving to the designer, who pockets most of the savings.
Then there is the knockoff "stuff" of questionable quality. Some may be built well, but the design has been stollen.
I am trying to stay away from Chinesium and recycled Yak turds crap. China is an unfriendly aggressor state, so I prefer to not support their economy where possible. That has become difficult.
Look to Europe and their previous dependency on pootlerstan oil and gas. This enabled tsar bedpan to invade Ukraine. Consider the leadup to WW2 and Neville Chamberlain's appeasement to Hitler and his Nazis. IMHO it is better to back away from China now.
Then there are those people who race vintage and must use vintage castings. Another example would be people that want a Concours or Concours appearing vehicle. And then there are stuborn arses like me that want to use what I have and learn. Kind of my reduce, reuse and recycle ethic.
Not trying to convince anyone my way is better, just my preference. How others chose to spend their hard earned happy cabbage or do things is fine with me.
As to your mention of where I am located, central to a bit northern Alberta, Canada. I have to take parts 100 miles or a bit more for machining and leave them. Then drive back to pick them up, so 400 to 500 miles. Most parts we get all come from the US with currently an exchange rate of 1.4 and then most likely shipping. On top of that we have the left dishonourable prime peckerhead of Canada, daesh dustbin turdo. He and his guvment are spending money like rabid babboons, so raise taxes to get their greedy hands on more money. I firmly believe they skim a little graft off in the process. If parts are shipped by mail, Canada Customs and Border in collusion with Canada Post collect duty, which you must pay to pick up your shipment. If you refuse they send your order back. You can appeal or request to reduce the duty, but that takes months and you have paid the duty. For antique repair parts there is not supposed to be duty charged for US made parts. Thieving Feds n Heads!
So yes I am very familiar with machining and parts costs. I would have to check a performance parts supply store in Edmonton on the cost of Edelbrock or AFR heads, but $2,000 likely will not cover the cost. $3,000 is more likely, especially when I would have to drive 400 km or 250 miles return to pick them up. 87 gasoline is between $1.47 and $1.52 per liter. There are 3.785 liters per gallon US.
 
Of all people you should know ...
Just say on the mild side ..
Also because cam numbers still make my head spin... I've tried and tried and tried to understand them
I've never understood at what point an "RV" cam isn't an "RV" cam anymore. Or where one starts being an "RV" cam. It's just such a vague description. I think 3/4 cam is more specific. lol
 
I've never understood at what point an "RV" cam isn't an "RV" cam anymore. Or where one starts being an "RV" cam.
I always thought people generally meant cams with decent idle, vacuum and didn't mess with idle-2500 rpm torque (power) that much, whatever that maybe for your engine probably around 200-215 intake duration.
It's just such a vague description. I think 3/4 cam is more specific. lol
People like to categorize/generalize.
 
I've never understood at what point an "RV" cam isn't an "RV" cam anymore. Or where one starts being an "RV" cam. It's just such a vague description. I think 3/4 cam is more specific. lol
look, alls i know is that the law states you can drink while underway in an RV as long as you're behind the sink. which begs the question: can you mount the sink to the dashboard?
 
Turk,
When you LEARN how an air bleed works, & how a HP number is produced, then you might be able to preach to others, most of whom are more knowledgeable than you...which wouldn't be that hard gauging from the BS you spew on this website.
And how many patents do you have???????
 
Turk,
When you LEARN how an air bleed works, & how a HP number is produced, then you might be able to preach to others, most of whom are more knowledgeable than you...which wouldn't be that hard gauging from the BS you spew on this website.
And how many patents do you have???????


I have as many patents as you do. So who cares.

The Taylor book covers how bleeds work.

Evidently Urich didn’t read that book. Because he is wrong. Since you don’t test and blindly follow anyone who writes a book you’ll always be wrong.
 
Not knocking DV but he's just one of many engine builders out there none of them agree 100% or know a 100% of anything and anyone can have patents, it's not a good argument for or against anything.

But the talk of his patent got me interested what they were, these are what I found.



Patents by Inventor David Vizard
David Vizard has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
  • Internal combustion engine

    Patent number: 6615795
    Abstract: The present invention seeks to provide further methods to generate swirl and reduce cross flow in spark ignition internal combustion engines having two inlet and two exhaust valves per cylinder head, without the use of additional moving parts.
    Type: Grant
    Filed: March 1, 2002
    Date of Patent: September 9, 2003
    Inventors: David James Martin, David Vizard
  • Internal combustion engine

    Publication number: 20020185105
    Abstract: The present invention seeks to provide, inter alia, further methods to generate swirl and reduce cross flow in spark ignition internal combustion engines having two inlet and two exhaust valves per cylinder head, without the use of additional moving parts.
    Type: Application
    Filed: March 1, 2002
    Publication date: December 12, 2002
    Inventors: David James Martin, David Vizard
  • Exhaust mufflers for internal combustion engines

    Patent number: 4577724
    Abstract: An exhaust muffler comprises a closed chamber, an inlet pipe leading into the chamber, an outlet pipe leading from the chamber, two spaced bulkheads dividing the chamber into first and second buffer compartments separated by an intermediate compartment containing a glass fibre pack, three pass tubes extending through the bulkheads and across the intermediate compartment, two of the pass tubes forming continuations of the inlet and outlet pipes respectively and having flared open ends in the buffer compartments respectively, and a parabolic noise reflector located opposite the open end of said two pass tubes in such manner as to reflect down the pass tubes a proportion of the noise generated by gases flowing along the pass tubes.
    Type: Grant
    Filed: June 18, 1984
    Date of Patent: March 25, 1986
    Assignee: Shelburne Incorporated
    Inventor: David Vizard
  • Exhaust mufflers for internal combustion engines

    Patent number: 4467887
    Abstract: An exhaust muffler comprises a closed chamber, an inlet pipe leading into the chamber, an outlet pipe leading from the chamber, two spaced bulkheads dividing the chamber into first and second buffer compartments separated by an intermediate compartment containing a glass fiber pack, three pass tubes extending through the bulkheads and across the intermediate compartment, two of the pass tubes forming continuations of the inlet and outlet pipes respectively and having flared open ends in the buffer compartments respectively, and a parabolic noise reflector located opposite the open end of said two pass tubes in such manner as to reflect down the pass tubes a proportion of the noise generated by gases flowing along the pass tubes.
    Type: Grant
    Filed: November 30, 1981
    Date of Patent: August 28, 1984
    Assignee: Shelburne Incorporated
    Inventor: David Vizard
 
Thanks for all the input we're a bit off rails but that's ok. Lots of cam recommendations from different perspectives. After looking at my intake and considering the heads I am going t upgrade my exhaust and most likely go with the 272 .455 [email protected] single pattern grind. with the magnum head 1.6 rockers that should work out to around [email protected] and .485 lift. Am waiting to hear from Oregon Can to see if my core can accept that profile, they were pretty sure it could since we were starting with a mopar cam to begin with.
 
the correct answer is, continues to be and will always remain: 3/4 race cam

IMG_20240430_120609_01.jpg
 
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