596 heads spring installed height too low

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Dusterguy

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I run in problem. I bought comp cams 282 mechanical flat tapped camshaft and comps recommend 986-16 springs to use whit this cam. whit this spring it should to install to 1.750" and get 132lbs seat pressure.

Now i measure my heads and i get 1.650" install height. (whit my old locks and retainers, dont know them brand) Heads are machined to double springs and i have teflon type seals. Also have Crane roller 1.5 rocker arms.

I think i have to increase install height, am i right? If so, how i do it?? I have no idea. This is my first engine build..

Sorry bad english. Thanks.
 
First, the springs don't affect the installed height. Vice-versa, your springs require the 1.750" installed height so they don't bottom out ("closed coil") when the cam is at max lift.

I assume you measured the installed height with the rocker assembly out. 0.100" is a tremendous difference. Only a few things affect that - the length of the valves, how the valve seats in the head (do you have hardened seats?), and any shims under the springs. It is a bit tricky to measure the spring length installed.

It has been a while since I installed and checked my springs. I used a vernier caliper, with the plunge end sitting on the top of the shim under the spring. I adjusted shims to get the height correct. I forgot the shim increments (maybe 0.005" thick?).

I expect whoever assembled your heads would have checked the spring heights. That is a normal part of the job, since they must shim the springs. One guess is that you are checking with the rockers and pushrods installed and the pushrods are holding the valves open. Maybe they are too long. You could tell by looking at the hydraulic lifters. Are they pushed way down?
 
I dont know if i have hardened seats. There was 1 shim in bottom of every intake valve spring. Also dont know what is purpose of that.

I measured the installed height whit heads out of engine, no rocker things when measured. i have read that 1.650" is stock install height. and i know springs itselfs dont affect installed height. But if i put spring lets say 1.800" istall height, seat pressure is not what it should be, right?

Where to get retainers that raise installation height? Is there possible that the rocker arm hitting retainer, because retainer is longer?
 
you need to take your heads to a machine shop and have your spring seats cut deeper. take springs retainers and locks so they can set it up for you. that spring psi @ 1.650 will be to much.
 
Some aftermarket manufacturers make retainers and locks that can each add .050" installed height, but not for every application. I can't think of anyone who makes + .050" locks for multi-groove OEM valves. Most are for aftermarket single groove. You would still need retainers that fit the springs.
 
is there eny internet link i can watch where to buy retainers that increase installation height. Heads are ported is there material enough to remove 0.100" ?
 
I think what you are going to run into is the rocker will hit the retainer if you use the taller retainers and then you're into lash caps and rocker shaft shims just to make it work. It may just be easier to use the 26986 beehive springs with the right retainers and locks at you 1.650 installed height. They can take a little more lift before coil bind so if you are opening the valve to 1.15 you've got .090 clearance at max lift.
 
moper said:
I think what you are going to run into is the rocker will hit the retainer if you use the taller retainers and then you're into lash caps and rocker shaft shims just to make it work. It may just be easier to use the 26986 beehive springs with the right retainers and locks at you 1.650 installed height. They can take a little more lift before coil bind so if you are opening the valve to 1.15 you've got .090 clearance at max lift.
Click to expand...

That is maybe best to do. So what will be my seat pressure with 26986 springs (1.650")?

SpecsOD: Top 1.065" Bottom 1.415"
ID: Top .650" Bottom 1.000"
Seat Pressure: 123 lbs @ 1.750''
Open Pressure: 284 lbs @ 1.175''
Coil Bind: 1.060"
Spring Rate: 280 lbs/in
 
It's 280lbs per inch, or 28lbs per .100. So if the spring is 123lbs at 1.75, then it's going to be 151lbs at 1.65.
 
Ok. Thanks. Final question, is there eny negative things if i use those springs, i mean because theyre sligtly more seat pressure@1.650"?
 
the shims were there because the old springs werent giving the required pressure to control the valve/lifters at the expected rpm. there is room to lessen the hight depending on lift vs spring max compressed hight before coil bind/stacking in order to get more pressure from the spring.

the new springs dont need the shims, they do need at least 1.70 height, much less height/more psi will more than likely hurt the cam upon break in. imo

isky makes a +.050 or +.060 retainer for the 3/8 stem valve and common chrysler dimensioned retainer.
 
No negatives as far as I'm concerned. 20lbs won't make a difference on the seat. The 986s are 322lbs per inch for spring rate and is a much heavier spring at max lift. Generally not running enough seat spring pressure with a modern fast rate lobe is worse than running too much because the valve can become uncontrolled on the opening and clsoing ramps. If you are really concerned use the outer springs only of the 986s to break in the cam (which would be normal for a dual spring flat tappet application anyway), then replace them with the 26986s.
 
Im gonna get those single springs, it is most easy way.

Thanks for help to everyone!
 
Your best option is to use Crower 68405 springs. These are for FT cams, about 130 lb @ 1.650" ht. Pontiacs have a low installed ht, & the 68404 & 68405 are used a lot on those engines.
From memory the 282S cam has 236* @050, so is going to want about 130 lb on the seat.
 
Bewy said:
Your best option is to use Crower 68405 springs. These are for FT cams, about 130 lb @ 1.650" ht. Pontiacs have a low installed ht, & the 68404 & 68405 are used a lot on those engines.
From memory the 282S cam has 236* @050, so is going to want about 130 lb on the seat.
Click to expand...
If his spring pockets were machined he could throw some 995's in and have roughly 130 seat and 340 open
 
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