Is valve shrouding a concern in a 318 w/ 2.02 & 1.6 valves

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racerdude5

racerdude5

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Do I need to worry about valve shrouding in a 318 that is .030 over when putting Edelbrock Performer RPM heads or any other heads that have a 2.02 intake and a 1.60 exhaust?
 
I've never heard the terms, here, in which you speak sire... Unless your banging the piss out of that motor, 2.02/1.6 is for number dropping in conversation that are designed to get a 'wow bro' reaction..
 
Woods74 said:
I've never heard the terms, here, in which you speak sire... Unless your banging the piss out of that motor, 2.02/1.6 is for number dropping in conversation that are designed to get a 'wow bro' reaction..
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Lol I'm so confused. Valve shrouding is when the valve opens and is so close to the cylinder wall that it is detrimental to the flow of the cylinder head.
 
Again, in the 6 years I've been on here regularly, never seen this topic being a problem or being discussed...

It's kind of one of those, 'it is what it is' type of things, how would you change it if you could? Why? Do you secretly believe yo should do the 1.88/1.92 heads?

I sure do... Not so secretly. Your gonna need all the help with torque you can get! :D
 
I really don't think it is necessary to notch the bores either, just pointing out that they did do that in that particular build.
 
I have heard, although not speaking from experience, that on a stock bore 318, notches may be necessary and a overbore should be alright.
 
I've run 2.02's / 1.60's on standard bore 318 for years with no problem....
 
I have done it several times. If done incorrectly, it will lose power over the 1.88 valve.

It also depends on lift. If I get close to .500 lift NET, I lay out the gasket line around the cylinder, then lay out where the valve is. Then you blend OUT to the line and DOWN about .100 or so. Do it for every cylinder.

If you are running some ancient deal with .450 lift you can get by with out the notch. I can tell you, that on a flow bench you can see the difference with the notch. And on the dyno. And in your time slip.
 
racerdude5 said:
Do I need to worry about valve shrouding in a 318 that is .030 over when putting Edelbrock Performer RPM heads or any other heads that have a 2.02 intake and a 1.60 exhaust?
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NO!

And never worry about valve shrouding. While you want to avoid it for best performance, there's more than just a few factory examples out there in the world that have a bad case of valve shrouding but yet, the engine makes ridiculous power.

Oh! Almost forgot! David Visards has a good book on porting heads that has a topic on this issue. While the book is not an in depth technical book with hard to understand jargon, it is certainly worth the price of reading.
 
Dartboy52 said:
I only know what I read in this article. From the article:

"Though the 2.02/1.60 valves clear a 318s bores with ease, we machined out the combustion-chamber walls near the head gasket line adjacent to the valves to minimize shrouding...The idea is to enhance flow..."
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Read the whole thing, if you bored it I wouldn't worry about.

Our plan was to find flow by porting the heads and upping the valve diameter to 2.02/1.60 with a set of Milodon street valves. The valve spacing on all small-block Mopars is the same, so these valves will fit in the 302 castings the same as with any 318/340/360 heads. Valve shrouding isn't any more of an issue than with other small-block Mopar heads, since as part of the valvejob the chambers were cut concentric to the valve out to near the line of a Fel-Pro gasket. This makes the chamber quite a bit wider than the 318's stock 3.91-inch bore in the area adjacent to the valve. To address this, the bores were chamfered (notched) to minimize shrouding by the shelf left where the chamber meets the bore. Contrary to popular misconception, 2.02-inch intake valves fit the 318's bores without a problem; in fact 2.08-inch intake valves won't hit.
 
yellow rose said:
I have done it several times. If done incorrectly, it will lose power over the 1.88 valve.

It also depends on lift. If I get close to .500 lift NET, I lay out the gasket line around the cylinder, then lay out where the valve is. Then you blend OUT to the line and DOWN about .100 or so. Do it for every cylinder.

If you are running some ancient deal with .450 lift you can get by with out the notch. I can tell you, that on a flow bench you can see the difference with the notch. And on the dyno. And in your time slip.
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rumblefish360 said:
NO!

And never worry about valve shrouding. While you want to avoid it for best performance, there's more than just a few factory examples out there in the world that have a bad case of valve shrouding but yet, the engine makes ridiculous power.

Oh! Almost forgot! David Visars has a good book on porting heads that has a topic on this issue. While the book is not an in depth technical book with hard to understand jargon, it is certainly worth the price of reading.
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All tho it sound like i'm contradicting my self! I would have to agree on both of then statements!:burnout:
 
The combo is probably gonna be a 318 .030 over, standard stroke. At least 10.5:1 compression, 15:1 is ideal. Comp 294S solid lifter cam kit with Brodix B1BA or Indy LA-X heads. Finally, some large tube headers and small block chevy hilborn injection manifold with 2 3/16 or 1 7/8 stacks.
 
racerdude5 said:
The combo is probably gonna be a 318 .030 over, standard stroke. At least 10.5:1 compression, 15:1 is ideal. Comp 294S solid lifter cam kit with Brodix B1BA or Indy LA-X heads. Finally, some large tube headers and small block chevy hilborn injection manifold with 2 3/16 or 1 7/8 stacks.
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Then I would agree with whoever said why not a 360? They are cheep and around everywhere. I like the biggest bore I can get.
 
Valve Shrouding is a very, very real thing. How detrimental will it be on a 360 intended head, with 2.02 valves, on a 3.94 bore. Is yet to be seen.
The only real way is to have them bench flowed on a 3.91+.030 or .040 (whichever you do) pipe. I have seen heads with oversized valves that were supposed to flow 300 cfm, be choked down to 230 cfm on a stock bore block.

you don't necessarily need to bore notch the cylinder, but it may be worth your time now to have them flowed NOW, and to then have the valve un-shrouded on the cylinder head side if needed. (have done this several times)

I don't want to insult anyone that has never heard of this, or assumes it will be fine, but this is exactly how engines that make *** hp on paper, go together, and somehow only make 2XX HP, and can't get out of their own way. Then we all stand around and wonder what went wrong.

I'm also hoping the CR swing of "anywhere from 10.5:1 to 15:1" is a misprint...or we have much greater concerns to walk through than valve shrouding....
 
Johnny Pace said:
Valve Shrouding is a very, very real thing. How detrimental will it be on a 360 intended head, with 2.02 valves, on a 3.94 bore. Is yet to be seen.
The only real way is to have them bench flowed on a 3.91+.030 or .040 (whichever you do) pipe. I have seen heads with oversized valves that were supposed to flow 300 cfm, be choked down to 230 cfm on a stock bore block.

you don't necessarily need to bore notch the cylinder, but it may be worth your time now to have them flowed NOW, and to then have the valve un-shrouded on the cylinder head side if needed. (have done this several times)

I don't want to insult anyone that has never heard of this, or assumes it will be fine, but this is exactly how engines that make *** hp on paper, go together, and somehow only make 2XX HP, and can't get out of their own way. Then we all stand around and wonder what went wrong.

I'm also hoping the CR swing of "anywhere from 10.5:1 to 15:1" is a misprint...or we have much greater concerns to walk through than valve shrouding....
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Our testing agree.

I have seen it many times. Valve shrouding is real. It can hurt HP.
 
I did this on the head and bore on my 440 in my 72 satellite, just used the cometic gasket as outline.
 
Valve shrouding is a real concern. I watched my uncle who was a well known NHRA Stock/Super Stock engine builder back to back test a 1.88 vs. a 2.02 intake valve on the same port and same head with the trick valve job and back cuts on the flow bench on a 4 "bore. The 2.02 lost flow... because of the shrouding. It will be more on a 318...

It will work as long as there is not any interference but it will not be optimal.

On my factory iron head 360's I always ran 1.88's or 1.94's good enough for low 10's
 
I already have a 318 block and crank. I need 15:1 compression, but I don't know if I can afford the custom pistons though... :/ So you can reduce valve shrouding by running smaller valves or by reworking the combustion chamber and notching the cylinder walls? How much space do you need between the cylinder wall and the valve to avoid shrouding?
 
Are you gonna lose a few hp compared to 360/340 bores probably but not enough to worry about especially if your going 450 or less hp. You can notch it if you want to try to gain some back.
 
racerdude5 said:
I already have a 318 block and crank. I need 15:1 compression, but I don't know if I can afford the custom pistons though... :/ So you can reduce valve shrouding by running smaller valves or by reworking the combustion chamber and notching the cylinder walls? How much space do you need between the cylinder wall and the valve to avoid shrouding?
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How do you figure you NEED 15:1? I can tell you as the compression ratio goes up, the tuning window gets smaller. I will not go over 13:1 for anyone unless you have a track record with me of being able to tune compression that high.

And then, you posted a comp cam. How did you get that cam? You don't want that find and 15:1.
 
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