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Discussion Starter · #1 ·
i am changing from the hot cam to the 846 along with the 383 stroker....my ? is i am running 1.6 rr's...can i still use these or do i need to change to 1.5's...thanks jd
 
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Discussion Starter · #3 ·
What is the capacity of your valve springs compared to the lift specs on the cam using 1.6 rockers? With the stroker, will you be decreasing the deck height?, and what type piston will you be using? To keep about the same compression ratio, piston clearence to valves should be ok, unless you are increasing it measurably.
 
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Discussion Starter · #4 ·
Your question doesn't address all the parameters. You can run 1.6's if the springs you choose can handle the lift.
 
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Discussion Starter · #5 ·
ok i got the specs on the springs im running now...gmpp part # is 12551483
installed height is 101# @ 1.78"
solid height is 1.22"
rate pounds per square inch..332
i'm thinkin i should be ok running the 1.6's
what do you think?...thanks jd
 
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Discussion Starter · #6 ·
Nope, you will need more spring. That cam with 1.6 rockers will have .543 I / .563 E lift, and I am guessing that they will want to see close to about 125-130 lbs of seat pressure.
 
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Discussion Starter · #8 ·
Check with the guys running LT4 heads, but I believe you are going to have to machine the seats to take the springs you need. I know a couple guys that went with the Crane 10308 double spring kit. A little homework for you, since crane makes that cam for GM, go to cranes web site and look up that cam, they will have info on suggested springs as well as other stuff, to go with that cam. Then see if you can match up the proper springs specs with theirs, and check comps or others available out there and see if a set will work with your current seat size and height to avoid machine work. Don't know what Karl Elwein is running on his LT4 heads, but he will be a wealth of information!
 
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Discussion Starter · #9 ·
Here is a link to the cam card, LINK

I'm pretty sure I used the spring that they mention. But set up at 160# seat due to machine shop recommendation. Also due to the 1.6 rocker ratio, because the cam card is really talking about 1.5 ratio.

That cam is a torque MONSTER
You'll love it.

Karl
 
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Discussion Starter · #10 ·
Here's a few things I learned this week about LT4 heads...

<UL TYPE=SQUARE><LI>The spring pockets can be enlarged to 1.550" without any problems. This is a common size cutter that about any machine shop will have. This size gives you lots of spring options.

<LI>With stock LT4 valves, you can use springs that need an installed height of up to 1.820" with standard retainers.[/list]

jdhall,
The springs you list would definitely NOT work with 1.6 rockers. They would be at coil bind on the exhaust side (installed height minus solid height = .560"). Also, that wouldn't be enough seat pressure...

According to Karl's 'details' on the Top ET page, he's running Comp 977 springs. These would have a seat pressure of 155 lbs at 1.850" installed height and 177 lbs at 1.800" installed height.

I'm getting my LT4's setup with Comp 987 springs. 138 lbs at installed height of 1.750" and 328 lbs at .550" lift. <These are 'after break-in' figures; the figures are higher on the new springs.> Coil bind at .600" lift.

LMK if you have more ?
I've been researching this LT4 crap for some time... ;)
 
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Discussion Starter · #11 ·
ok i can see im gonna have a problem with running the 1.6 rr's unless i get my heads cut to accept the springs...so my next question is since i would have to get all that done with with heads in order to run 1.6 rockers...could i use the spring i have on the heads now and 1.5 rr's without having to do any cutting on the head...and would i have more bottom end torque that way or by just installing the "hot cam" back in the new engine with the 1.6's cause i know they will work with the hot cam...thats what i was running before but im hunting more bottom end versus mid to top
jd :D
 
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Discussion Starter · #14 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by Karl Ellwein:
Combination Motorsports might have a spring you can use. Might give them a call.
Karl
<HR></BLOCKQUOTE>

With the 'splash' of info they presented on a camaro forum regarding these springs, I'll state a SHOULD/BETTER instead of MIGHT.


BTW, the Hoosker quote: "I'm getting my LT4's setup with Comp 987 springs. 138 lbs at installed height of 1.750" and 328 lbs at .550" lift. Coil bind at .600" lift.", doesn't add up, unless you meant the 328# was at .500" lift. I believe it to be a typo.

Also, Karl, that seat pressure seems 'borderline' for hydralics to me. :(
 
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Discussion Starter · #15 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by TAKN2XSS:
Also, Karl, that seat pressure seems 'borderline' for hydralics to me. :(<HR></BLOCKQUOTE>
I agree. I think 160lb seat is too much really for hydraulics, but the guy I've been having set up my heads has been pushing me for more spring pressure. So to get away from that, I'm going solid only from now on.
 
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Discussion Starter · #16 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by TAKN2XSS:
BTW, the Hoosker quote: "I'm getting my LT4's setup with Comp 987 springs. 138 lbs at installed height of 1.750" and 328 lbs at .550" lift. Coil bind at .600" lift.", doesn't add up, unless you meant the 328# was at .500" lift. I believe it to be a typo.<HR></BLOCKQUOTE>

What part doesn't "add up" for you...?
The 987 springs have 310 lbs at .500 lift (1.250") and 328 lbs at .550 lift (1.200"). Page 306 of Comp Cams Catalog, Valve Spring Chart By Installed Height.

1.750" IH minus .550" lift equals 1.200" spring height; maybe that's it... Subtraction, not addition... ;)

These figures checked a bit higher on a spring tester at the machine shop, but that is expected before the springs "break-in".
 
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Discussion Starter · #17 ·
What part doesn't add up for you?

That page, like some others, has errors. The page I recommend is 303. BTW, if you insist of pg. 306, note the note that says recommended max lift of .500" for that spring. Pg. 303 is the better of the two, IMO. Even that page isn't perfect, but more accurate. Course, it's your choice.


Another BTW, there is no 'break in' specs. The specs listed for any spring is for new springs.
 
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Discussion Starter · #18 ·
Hey TAKN2XSS,

I'm not trying to start a pissing contest here, but I don't understand how you can say page 303 is better / more accurate than page 306... :confused:

I have personally compared the listed spring loads at various checking heights with my machine shop. I suggest you and anyone else swapping springs do the same...

<BLOCKQUOTE>quote:</font><HR>note that says recommended max lift of .500" for that spring <HR></BLOCKQUOTE>

Yes, I can read. I also know that the 986 springs are recommended for the 306 cam (.510 & .540 lift with 1.5's). Max lift of 986 spring = same .500" figure. How do you reconcile? Measure... 987's use same outer spring and a stiffer inner spring, which yields a slightly higher overall rate.

<BLOCKQUOTE>quote:</font><HR>BTW, there is no 'break in' specs. The specs listed for any spring is for new springs <HR></BLOCKQUOTE>

Once again, I never listed any 'break-in' specs. The given specs are what the springs should be at the given IH. There IS a break-in procedure recommended by Comp. Before you do it, measure the spring rate and they will probably be higher at the given check figures.

I'm not working strictly in 'theory' here and regurgitating #'s from a book...
We measured...
 
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Discussion Starter · #19 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by Hoosker:
Hey TAKN2XSS,

I don't understand how you can say page 303 is better / more accurate than page 306... :confused:
<HR></BLOCKQUOTE>

Scott, the figures just don't add up cuz there is too many errors/discreptancies on that page.

I have personally compared the listed spring loads at various checking heights with my machine shop. I suggest you and anyone else swapping springs do the same...

I have.


Yes, I can read

:confused: I didn't question whether or not you could. It is more of what you do with the info you've read. I meerly stated to note what I did, to point out another of several errors/discreptancies on that page. CC does however use that .500" figure for several springs when listing a given 'open load' pressure in their specs. (installed hgt. + .500")

Once again, I never listed any 'break-in' specs.

That is what I got out of the following quote: "These figures checked a bit higher on a spring tester at the machine shop, but that is expected before the springs "break-in"." You allowed for 'break-in' cuz you figured the springs were stronger than (what you considered accurate) specs. :shrug: There is no allowance for 'break-in'. :(

The springs won't 'check a bit higher', if the correct spring specs are used, but you are entitled to use whatever specs you prefer.


The given specs are what the springs should be at the given IH. There IS a break-in procedure recommended by Comp. Before you do it, measure the spring rate and they will probably be higher at the given check figures.

I'm not working strictly in 'theory' here and regurgitating #'s from a book...
We measured


So have I (measured/checked). :shrug: I do on any springs I touch. What is the point of buying an expensive/quality spring tester, if you're not gonna use it. I don't know what else to add to what I already stated. Break-in procedure does not relate/refer to break-in specs. ??

I'm not trying to start a pissing contest here...

No need, I did state it was your choice (to use whatever specs you figure will fit your needs). :another shrug:
 
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