Intake/Exhaust valves

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Engnbldr on ebay.


They should help significantly, in general there is no downside to larger valves until you run out of room in the bore. And that advantage is at lower lifts, which means that they help power even with a stock or mild cam. You don't need a big cam to take advantage of the greater flow.

You will need to have hardened seats put into the head on the exhaust side, so be sure to budget for that too.

If you can have the machine shop run a 'bowl hawg' (75 degree cutter) into the port after cutting the bigger seats that will help significantly too.
 
I put stock 318 valves in my slant head. 1.78 and 1.50.
 
robertob said:
Engnbldr on ebay.


They should help significantly, in general there is no downside to larger valves until you run out of room in the bore. And that advantage is at lower lifts, which means that they help power even with a stock or mild cam. You don't need a big cam to take advantage of the greater flow.

You will need to have hardened seats put into the head on the exhaust side, so be sure to budget for that too.

If you can have the machine shop run a 'bowl hawg' (75 degree cutter) into the port after cutting the bigger seats that will help significantly too.
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2x on engine builder valves off ebay... and as stated have them run the cutter into the bowl and then blend the bowl and port match to the gasket.

you marks friend in signal hill?

RustyRatRod said:
I put stock 318 valves in my slant head. 1.78 and 1.50.
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im still worried about the stands splitting from the spacer...
 
There's no way that can happen. They don't act as a wedge. They sit straight down and fit perfectly into the stand. They aren't that tall at all.
 
Yeah 318 valves are not for amateurs. But I think Mike Jeffrey sets up his heads with longer valves, you might call and ask him what he does. The problem with the stock length valves is you can't get much more than .500 lift, which is cool for me but the big power guys might not like that limit. Not sure how much lift you can get before you run into rocker geometry issues though. Beehive springs would help with that.
 
robertob said:
Yeah 318 valves are not for amateurs. But I think Mike Jeffrey sets up his heads with longer valves, you might call and ask him what he does. The problem with the stock length valves is you can't get much more than .500 lift, which is cool for me but the big power guys might not like that limit. Not sure how much lift you can get before you run into rocker geometry issues though. Beehive springs would help with that.
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2 questions, please:

1. Just what is the lift-limit (you said not much over .500") for stock valves/retainers? I'm assuming the retainers run into the valve guide bosses or the valve-guides, themselves, at some point, limiting the amount of lift possible, and....

2. You said :"rocker geometry issues though. Beehive springs would help with that." How could valve spring configuration (beehive???) affect rocker arm geometry?

I am confused about that. Just trying to understand this...

Any info will be appreciated.:hello2:
 
Hey Bill,

I can only report on what I found with my head and talking to others, Doc or someone else might have more info. But here's what I meant:

Bill Dedman said:
2 questions, please:

1. Just what is the lift-limit (you said not much over .500") for stock valves/retainers? I'm assuming the retainers run into the valve guide bosses or the valve-guides, themselves, at some point, limiting the amount of lift possible, and....
Click to expand...

Yes, stock there is not much clearance between the retainer and the top of the seal (maybe enough to run .450 lift? I don't know.) Running positive seals helps. I had my machinist cut my guides down to have enough clearance to get .500 lift and he told me that I could not go much further without making the valve guide so short that it would not support the valve properly. That's why people want to run longer valves.

2. You said :"rocker geometry issues though. Beehive springs would help with that." How could valve spring configuration (beehive???) affect rocker arm geometry?
I am confused about that. Just trying to understand this...
Click to expand...

Sorry that was not very clear - I was talking about if you use longer valves - if the angle between the rocker and the valve gets crazy the edge of the retainer hits the bottom of the rocker. Some guys on SS.org ran into that problem. The beehive springs have retainers that are a smaller diameter, which gives more clearance.
 
I haven't really played with these yet - but the retainer is the least of your worries when you go with longer valves and yes, a beehive would help with that interference. but that's not the big problem. The geometry with a shaft mounted rocker system will be off with longer valves because the valves tip slightly towatrds the shaft centerline. So the longer the valves, the less distance between the shaft and the valve tip. that's the bigger issue. I don't know the angles on the slants so I can't say how bad that would be. But - the fix for that is to move the shaft centerline. Sometimes that can be addressed with rocker support blocks or just shims if it's not a high rpm engine.
You also get to the point where the port can't flow what the valve can anyway - which makes it all a moot point. The ports suck.
 
robertob said:
Hey Bill,

I can only report on what I found with my head and talking to others, Doc or someone else might have more info. But here's what I meant:



Yes, stock there is not much clearance between the retainer and the top of the seal (maybe enough to run .450 lift? I don't know.) Running positive seals helps. I had my machinist cut my guides down to have enough clearance to get .500 lift and he told me that I could not go much further without making the valve guide so short that it would not support the valve properly. That's why people want to run longer valves.



Sorry that was not very clear - I was talking about if you use longer valves - if the angle between the rocker and the valve gets crazy the edge of the retainer hits the bottom of the rocker. Some guys on SS.org ran into that problem. The beehive springs have retainers that are a smaller diameter, which gives more clearance.
Click to expand...

Thanks for the explanation. Now, I understand it all.
 
moper said:
The ports suck.
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And they still suck after a port job, which is the reason that the forced induction engines are a good way around this problem. Trying to make horsepower with a normally-aspirated slant six is like trying to run a marathon with a piece of duct tape over your mouth... breathing is just too restricted.

Of course, everybody doesn't want, or need to go tens or even twelves, and if you can be happy with a fourteen second car, the smart thing to do is build a normally aspirated engine that has a good cam, high compression, plenty of carburetion and a nice set of headers, and avoid the complexity and tuning issues that always come with a turbo or supercharger. Probably not as cheap, but waaaay easier, and that's surely worth something!

A fourteen-second car can be a lot of fun!!!
 
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