340 xhead spring shimming, height and pocket question(s)

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They should give you the o.d. And I.d. Of the spring in the description. You have the retainers and o measure?
 
Thanks, wasnt sure if there was more than just od/id to make sure retainers fit? Yes I have verniers to measure.
I have someone helping me with spring situation. Thanks!
duster 344 said:
They should give you the o.d. And I.d. Of the spring in the description. You have the retainers and o measure?
Click to expand...
 
4spdragtop said:
Heres a screen shot of Summits PSI recommendations for SFT cams.
Agree? Disagree?

View attachment 1716052191
Click to expand...
I think that is pretty much the spring you get plus or minus a few pounds, if you buy a set of ProMaxx or other heads that is setup from the factory for a FT cam. That doesn't mean that they are optimum for every FT lobe. I'm sure there are agressive lobes that would want more spring.
I'm going through this as well. I think the Comp tech is covering his rear end recommending a spring that is 140-ish on the seat and 390 at .550" lift. For a standard length valve, there aren't any springs that can support that, but I'm sure that guys have been running similar cams on OEM heads for decades.
 
What I found out from comp was, the spring rate has to be high enough for a more aggressive cam. Prevent valve float at higher rpm, your running solid lifters. Lighter then recommended springs could through your valves a bit. Depends on what rpm’s your going to be using. Some of the old racers I heard used to set up the valves that way to get extra lift in the stock class
 
When I called Comp, I was 8th in line lol. So I "kinda" get why he was in a rush, BUT it's not like I was window shopping, at least spend 10 minutes on phone to help. I get the cya part, he said exact same thing as you mentioned. Too aggressive for 942. Once I mentioned or tried to mention the installed height I got and increased psi, he just talked over me and said 942 arent recommended. Basically end of discussion lol
gzig5 said:
I think that is pretty much the spring you get plus or minus a few pounds, if you buy a set of ProMaxx or other heads that is setup from the factory for a FT cam. That doesn't mean that they are optimum for every FT lobe. I'm sure there are agressive lobes that would want more spring.
I'm going through this as well. I think the Comp tech is covering his rear end recommending a spring that is 140-ish on the seat and 390 at .550" lift. For a standard length valve, there aren't any springs that can support that, but I'm sure that guys have been running similar cams on OEM heads for decades.
Click to expand...
When I saw the cam for sale I jumped on it asap and figured I would "work around" the particulars lol. If I didnt grab it asap it would have been sold lol.
I probably chose a bigger cam than I should have, but I wanted something healthy. Everything you said makes sense, so here we are in the rabbit hole lol.
Thanks for chiming in guys.
Cheers
duster 344 said:
What I found out from comp was, the spring rate has to be high enough for a more aggressive cam. Prevent valve float at higher rpm, your running solid lifters. Lighter then recommended springs could through your valves a bit. Depends on what rpm’s your going to be using. Some of the old racers I heard used to set up the valves that way to get extra lift in the stock class
Click to expand...
 
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