Valve Springs again

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Coyote Jack

Coyote Jack

Member #55, I'm old
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I am looking at ordering a roller cam and springs. I want to give the manufacturer as much info as I can. So I need to know the following. These numbers should be what the factory put in. I am pretty sure on a couple of them, but would like conformation. Also, how much pressure can stock adjustable rockers take? These are stock 340 "X" heads.

The factory specs needed.

Valve length
Valve diameter
Spring installed height
Spring diameter


Jack
 
It's been a few yrs. since I did my X heads but if I remember right the factory installed ht. was 1.68" and the spring diameter was 1.37" O.D. There are things that can cause a variance in the installed ht. such as if the valves have been ground very many times, new seats installed, non standard length valves used, non stock spring retainers and locks. For that reason it's best to measure rather than take it for granted that your 40+ yr. old heads are exactly the way they came from the factory.

The valve stem o.d. is 3/8" and I think the stock length was 4.90"

Not sure how much pressure stock adjustable rockers can take but I've heard they are pretty stout. I still wouldn't go over 300 lbs. open to be safe.

Is this a solid or hydraulic roller?
 
A few things to think about:

1. Stock rockers will never be able to handle solid roller spring pressures. If you are 250#’s on the seat, you are probably in the neighborhood of 600#’s open right?? That would crush those rockers in a hurry. You will need GOOD aftermarket rockers (not cheap-O's).

2. A roller spring with that kind of pressure will NOT fit in a stock head without some serious work, so all the stock spring installed height, stock and spring diameter become a mute point. Most springs of that size are about 1.55” in diameter.

3. Most rockers have a HECK of a time clearing a 1.55” spring in a small block Mopar…lots of extra work to make them fit.

4. Using a solid roller cam with stock heads is a big mismatch of parts. Kind of like using 2.76 gears for an 1/8 mile drag car…it’s just out of place. Stock heads don’t flow enough air to take advantage of what a solid roller cam can do…not bashing, just thought you should know.
 
I'm not to worried about the heads not flowing enough as this is a blower engine, so it's force fed. The rocker gear not being good enough does worry me though. I am trying to do this on the cheap. More things to think about. Thanks guys.

Jack
 
I'm confused....you just said "blower engine" and "cheap" in the same sentence..........:sign6:
 
The problem is compounded by the blower. The springs have to close the valve against the boost. It's nothing on low boost setups but if you're making more keep that in mind.
 
flyfish said:
I'm confused....you just said "blower engine" and "cheap" in the same sentence..........:sign6:
Click to expand...

Yeah, I know what you mean. The blower setup will not be cheap. But I am hoping to build the basic engine on the cheap. So far, so good but this valve train is becoming a problem.

Jack
 
moper said:
The problem is compounded by the blower. The springs have to close the valve against the boost. It's nothing on low boost setups but if you're making more keep that in mind.
Click to expand...

From looking at the setup I want to run I am looking at 8 lbs of boost. The springs shouldn't need to be to stout for boost pressure. But a roller cam's requirements are driving the spring pressures up.

Jack
 
What about running a hydraulic roller? You can make good power with them too and they don't require as much spring pressure. What blower do you have in mind?
 
fishy68 said:
What about running a hydraulic roller? You can make good power with them too and they don't require as much spring pressure. What blower do you have in mind?
Click to expand...

It will be a roots 6-71. Right now if I buy new it looks like it will be coming from Dean's Blowers.

Jack
 
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