LA heads-Magnum valves?

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dartjack

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Been following the posts for quite a while. I haven't (or don't remember) seeing anyone having discussed/tried magnum valves in an LA head. If the guides have to be replaced anyway why not go for lighter parts? Would the length be the same? The valve springs might present a problem. If the spring seats have to be machined it could be done whem the guides are installed. Also would the rocker arm geometry be the same?
 
I never tried it, but it shouldn't be a problem for a GOOD machine shop. The slightly larger valves (over OEM LA 1.88/1.60) would move the seats out and up for better flow and the guides would naturally need to be made thinner to accomodate them. I don't recall if Magnum valves are shorter than LA valves, but Comp Cams sells Magnum valves that are standard Magnum length as well as +.100". The closer you can get to the original LA valve stem height, the less problems you would have and probably have a wider spring selection to choose from. I've been using beehives on LA heads that meet my spring pressure needs and they provide plenty of rocker arm clearance, among other benefits.
 
magnum valves tend to cost more, more then say some 11/32 stem +.100 over standard chevy stuff.

do the 11/32 +.100 350 valves instead.

I run them in my j heads, work great cost less and are lighter still than stock 3/8
 
my opinion is cost, as in...how much for the porting and staying with stock valves w/vj as opposed to buying new valves, new locks, and a lil more than the regular valve job due to extra cutting/throat cutting and then the necessary bowl/seat blending to get the numbers ramm has.

thats where im coming from on one hand.

perfect example here.

run of the mill machine shop installed big valves in a friend slant head and did a minor blend.....he then brought the head to me and we flowed it for fun right after i flowed a stock head.........the big valve head flowed 2 cfm less than the stock head. we were both amazed and taken back... i then took another slant head that i had simply bowl blended with the stock valves 'did it 9 yrs ago with a black and deck drill when i had almost no clue about this stuff....and that head went 9 cfm more than the big valved/run of the mill machine shop seat blended one he brought me.
lol

the 318 head in my thread flows 210/177 cfm, with around 200/156 @.500
see what im saying?
 
toolmanmike said:
Lots of questions. It can be done but is it necessary. How much better would a Magnum valve flow in your opinion?
Click to expand...

They flow quite a bit better actually. The only reason I went this route is , I had the guides and the stock Magnum valves already this=FREE. I would have gone with Chevy valves had I not had these "lying around". In fact I am just finishing up a set of "J" heads right now using Chevy 2.02/1.6 valves that flow around 244 cfm FWIW. J.Rob
 
I've got a bunch of mag valves and hardware also. Are the valves the same length? How would you get the depth correct using old school seat grinding? Maybe cut to correct spring height? It will be on 596 castings.
 
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