Can the valve angle be changed on a set of heads? I wonder how much it would help to go from the standard 15° to the C5R angle of 11°

I think it would help on a smaller bore motor to have a shallow valve angle especially with bigger valves.

What do you think?

John

 

whomever knows the answer to this... can u explain it ? <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> I didn't realize that valves were angled (I'm still learning alot about engines....)

 

I believe it would be possible. It would require welding of the existing valve guide holes and valve seat pockets. Then redrilling and remachining of both. Due to the cost and complexity of this operation it wouldn't be worth it. You'd be better off buying the C5-R heads and a custom manifold.

Shane

 

The valve angle is in relation to the block deck surface. If the valves were perfectly inline with the cylinder bores they would have a 0° angle. The valves on a LS1 head are tilted toward the middle of the motor 15° using the deck as a reference.

Think of a tube coming straight out of the center of the cylinder bore. Now tilt it back towards the middle of the motor 15°. That is the angle of the valve. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by horist:
<strong>whomever knows the answer to this... can u explain it ? <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> I didn't realize that valves were angled (I'm still learning alot about engines....)</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The valves are angled in relation to the bore centerline. If you drew a line straight up through the center of the bore, the valves on an LS1 are tilted 15 degrees from that line. On most gen I small block chevys, it was 23 degrees (on some high performance heads it is 18 degrees.) The C5-R head goes even further with an 11 degree valve angle.

Shane

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by XtraCajunSS:
<strong>I believe it would be possible. It would require welding of the existing valve guide holes and valve seat pockets. Then redrilling and remachining of both. Due to the cost and complexity of this operation it wouldn't be worth it. You'd be better off buying the C5-R heads and a custom manifold.

Shane</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I thought maybe the valve guide holes could be drilled out and sleeved. I guess you'd have to worry about dropping a sleeve in your heads then. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

The one thing is you could save alot of money in cores, porting, and a new intake over the C5R heads. The return for the extra work may not be worth it though.

I wonder what type of flow you could gain from this?

Just something interesting to think about. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

John

 

I think the main benefit of a smaller valve angle is to produce a smaller combustion chamber not to improved flow

LAter <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

in theory the shallower valve angle would be better for better power but the cost factor would render it moot. you would need shaft rockers new pistons besides the machining of the head cores. it would be easier to go C5R and a custom manifold. it just shows that when theory meets reality things become cost prohibitive.

Jay

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by XLR8NSS:
<strong>Can the valve angle be changed on a set of heads? I wonder how much it would help to go from the standard 15° to the C5R angle of 11°
John</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">John,
FWIW, on a SB or BB old school Chev, we have 'angle milled' the heads in the past. Not needed though on those particular engines today though with all of the excellent Dart/Brodix type heads around now. Why did we do that?
1. To decrease the valve angle, as you said.
2. Smaller comb' chamber (= higher comp')
3. The intake port has a more vertical alignment, meaning the intake manifold can be more vertical (= flow)
Down sides:
1. Intake manifold needs angle milling.
2. thicker intake gaskets are needed.
Different pistons if you are close to piston to valve clearance (our race engines usually are!)
3. Alters valvetrain geometry.
4. end up having heads that only fit with that manifold, those pistons, etc, etc.
5. Cost$$
6. A lot of work for only marginal gains (Thats Pro Stock racing though)
Go with the C5R heads if thats what you are REALLY after, as someone else suggested!!!
Cheers. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Great discussion!

Since I'm going with an iron block(smaller bore) and the C5R heads are way outta my price range I was trying to think of things that could be done to help a set of 6.0L heads flow just that little bit more. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

This seems to be cost prohibitive, as stated before, for the minimal gains that may be seen.

I'm going to see what type of head AFR comes out with in a year or two. They will/do have some being tested on cars soon from what I could gather but, it may be a while before we ever see them. The numbers I've heard for them sound nice. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

John <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

The intake port, should theoretically raise up in relation to the valve when changing from 15* to 11* valve angle. This is hard to package as far as getting a intake manifold to bridge and seal the 2 heads. This raised port is where the most gain in air flow lies, this would allow for straighter angle to the back of valve. The bend in intake ports is where much flow is lost in conventional heads. I am sure there are intakes to work with C5R 11* heads but the port angle is probably a compromise to keep reasonable hood clearance with Corvettes.

 

Yep, raised runners and shallow valve angles. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> That would be nice.

I'm putting the 422 I'm getting into a '99 Silverado so hood clearance for a custom intake shouldn't be a problem. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

LS1derfull - you don't happen to know the plenum volume and runner sizes on the truck intake do you? I think it is going to limit the motor in the upper rpm range and I might try to put on a LS6 manifold. What do you think?

Thanks

John

 

John i dont have Volume sizes of truck intake, but my experienced opinion of the truck intake is that its large and because of its runner lengths and approaching angle of ports to head, it has the most potential of all the GM manifolds. Runner volume can be adjusted at cylinder head, if the truck man. leaves you short volume wise.
I think its the "Tunnel Ram" of LS1 motors. The work and testing i just performed with my heads and LS6 intake showed me that manifold does neck down at the exit of port, there is meat to grind open if need be. Let me know what you end up doing.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Will Race 4 Food:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by XLR8NSS:
<strong>Can the valve angle be changed on a set of heads? I wonder how much it would help to go from the standard 15° to the C5R angle of 11°
John</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">John,
FWIW, on a SB or BB old school Chev, we have 'angle milled' the heads in the past. Not needed though on those particular engines today though with all of the excellent Dart/Brodix type heads around now. Why did we do that?
1. To decrease the valve angle, as you said.
2. Smaller comb' chamber (= higher comp')
3. The intake port has a more vertical alignment, meaning the intake manifold can be more vertical (= flow)
Down sides:
1. Intake manifold needs angle milling.
2. thicker intake gaskets are needed.
Different pistons if you are close to piston to valve clearance (our race engines usually are!)
3. Alters valvetrain geometry.
4. end up having heads that only fit with that manifold, those pistons, etc, etc.
5. Cost$$
6. A lot of work for only marginal gains (Thats Pro Stock racing though)
Go with the C5R heads if thats what you are REALLY after, as someone else suggested!!!
Cheers. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Angle milling of SBC heads upto .200" only yields 1-1.5deg of valve angle change. If you weld the intake side of the face by the same amount you will see 3.5 deg of angle change. This is where the original "rollover" heads came from.

The advantage of shallow valve heads is that the valve opens down the centre of the bore rather than towards the bore keeping it unshrouded. The small comb. chamber that results allow high CR without large domes restricting airflow and flame travel.

Shallow valve angle heads must have raised intake ports as the air still has to make the turn through the short side. As any head porter who has a flow bench will tell you it is easy to get the air to flow across the roof and out the back of the valve....it is hard to get it over the floor and over the short turn....velocity is so much higher here...then chuck in the high swirl of a LS1 port and you are pulling out your hair....get it right and <img border="0" alt="[Camaro]" title="" src="graemlins/camaro.gif" /> If he hasn't got a flow bench or doesn't know how to use it <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" />

<small>[ June 20, 2002, 04:48 AM: Message edited by: HOWQUICK ]</small>

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by HOWQUICK:
As any head porter who has a flow bench will tell you it is easy to get the air to flow across the roof and out the back of the valve....it is hard to get it over the floor and over the short turn....velocity is so much higher here...then chuck in the high swirl of a LS1 port and you are pulling out your hair....get it right and <img border="0" alt="[Camaro]" title="" src="graemlins/camaro.gif" /> If he hasn't got a flow bench or doesn't know how to use it <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" /> [/QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Howquick,
Very true. On our 'old' school Chev race engines, we did that years ago to max out the early heads. Like I said, not needed anymore! What you said about someone who either hasn't got a flow bench or doesn't know how to use it, oh yeah! I have a friend who just got himself a secondhand flowbench, albeit the smaller Superflow model, and now he thinks he knows most of it! We have had ours since the 80's (that long ago?) and we are still learning...It never stops IMO. Would not recommend angle milling to anyone, too much effort, too little gain..
Cheers.

<small>[ June 20, 2002, 05:24 AM: Message edited by: Will Race 4 Food ]</small>

 

Ozzy guys - Agree with what you have said but as a further note have you found that heads with a lesser valve angle seem to make more power per cfm easier like Holden v8 heads. We've found the holden v8's seem to get higher V.E's with less work than say SBC 23deg. If you agree I would love no know "your" theories as to why ?
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
Thanks in advance .

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by VAP:
<strong>Ozzy guys - Agree with what you have said but as a further note have you found that heads with a lesser valve angle seem to make more power per cfm easier like Holden v8 heads. We've found the holden v8's seem to get higher V.E's with less work than say SBC 23deg. If you agree I would love no know "your" theories as to why ?
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
Thanks in advance .</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Hi VAP,
Damn, us Aussie guys are crammin in here!
Have never had experience personally with a serious Holden V8, only street stuff. However, Chev V8's, lots , but only did I think three engines with the angle milling deal, a LONG time ago.... It did Marginnaaalllyyy improve Hp, but in all honesty. we were chasing whatever we could get. Once the new generation dart & brodix heads came out, didn't do it at all then. Theories? See my post above! Cheers <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />