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fastsc92
05-03-2005, 09:56 AM
I've been running an average size cam for a little over a year now (.493 lift). When I swapped cams i was sure to degree it and I also had to machine a new keyway, ect ect. I installed the correct pushrods and everything has been fine, without even the slightest irritation. When I originally swapped, I just purchased new stock springs and was still running the stock stamped rockers. The stock springs may handle my .493 lift cam, but they just seem too weak for me. At high rpm's it feels like they float the valves. An upgrade is in the very very near future along with some RR's. So here are my questions:

I'm not exactly sure which springs to get. I've done some research and it seems that there are mixed opinions. Some people say to get the Comp. 942, and others say to go for the 986's. I'm looking for something that I can bolt in, and not have to machine the heads. I'm willing to shim if nessesary. I'd like to retain the stock spring cups and the stock retainers and locks if thats possible. I measured the stock OD on the springs and it comes in around 1.430". There are a few springs that will fit in that range. The 942's are a single spring, and the 985, 986, 987's are all double springs. I want something that can handle some lift, and I want something that isn't going to be weak at higher rpm's, and have the correct seat pressure, ect. Hopefully someone can give me some insight so I can make a choice. I'll try to list the specs below.

942 Single
OD- 1.437
ID- .974
Seat Load- [email protected] 1.700
Open Load- [email protected] 1.200
Coil Bind- 1.125
Rate (lb/in)- 339

985 Double
OD- 1.400
ID- .700
Seat Load- [email protected] 1.750
Open Load- [email protected] 1.250
Coil Bind- 1.150
Rate (lb/in)- 333

986 Double
OD- 1.400
ID- .697
Seat Load- [email protected] 1.750
Open Load- [email protected] 1.250
Coil Bind- 1.150
Rate (lb/in)- 296

987 Double
OD- 1.400
ID- .697
Seat Load- [email protected] 1.800
Open Load- [email protected] 1.200
Coil Bind- 1.150
Rate (lb/in)- 344

Slysc
05-03-2005, 11:12 AM
I think I had told you previously that I was running the comp cams 942 springs. Since then I have found that they are a poor choice. They require significant shimming and they floated on me and bent all my valves (slightly).

I started researching and found that the springs I think are the very best for our application are the Comp cams behive springs part number 26918. It is a beehive spring made for the LS1/LS6 motors but the specs and dimentions are perfect for the 3.8 SC. They will run 7000 + rpm with .600 lift but with only 130 lbs. of spring load. Plus because if their shape, they are lighter and they dampen the harmonics of the spring to keep them from bouncing n stuff. However, they do require different retainers. You would need the 783 or 774 retainers to go with them. A set of 12 springs is $140 something at Summit and a set of 16 retainers is around $60. I was going to run them but my machine shop had already ordered me a set of conventional springs for $90 that would accomodate my stock retainers and I decided to save the money and just go with the ones they ordered.

I'll attach an article from MM&FF talking about these springs.

Slysc
05-03-2005, 11:16 AM
The specs on the 26918 is:

1.055" outside diameter at the retainer
1.290" outside diameter at the base
.660" inside diameter at the retainer
.885" inside diameter at the base
130 lb seat load @ 1.800"
318 lb @ 1.200
1.085" coil bind
313 spring rate

XR7 Dave
05-03-2005, 12:01 PM
Good luck getting a 1.8" installed height on stock valves. :cool:

Slysc
05-03-2005, 12:28 PM
I've got small block chevy valves so the 1.8 works well. I guess I don't have a suggestion for stock valves.

fastsc92
05-03-2005, 01:06 PM
Well, thats why i posted on this subject. I am running stock valves and I'm looking for an upgrade. I've heard that the 942's are tight in the stock spring cups. The 985 and 986's are what I'm leaning towards. But, as I stated before, I have little knowledge on this subject and was hoping someone could help me out. Thanks guys

sizemoremk
05-03-2005, 01:34 PM
Catwithboost sold me the 986 springs for the stock valves, for a .531/.339 lift cam (212/220 duration and 112 LSA).

Cmac89 is also running this cam and valvetrain combo...
He said everything fit nicely without modification, but I know he was having fuel delivery probelms last I checked with him. Now he is having probelms with his MAF/injectors, so as soon as he gets that worked out, he may be able to say how he likes the setup....

Take care!

BlackbirdSC
05-03-2005, 02:17 PM
I highly doubt any double spring will fit in the stock spring cups. I don't have anything handy here at work, but I believe the spring cups won't take the .700"ish ID of the double springs.

Running alot for seat pressure isn't a bad thing. It's actually a good thing. Although, to keep from bleeding the lifters down, you'd want to keep it under 150# or so. But, with the heavy hydro roller lifters, you need at least 110# closed for any performance app. From what I remember when I redid my one set of heads, the stock springs had about 105# closed (used which is about 10% less than a new reading) and 220# open (.440" lift) with a .030" shim. That's not a good fit for anything over 5000 rpm. If using the stock 8mm bolt for the rockers, stay under 350# open pressure.

To sum up..

Closed pressure 110-150 130-140 ideal
Open (stock 8mm bolt) 280-350 300-320 ideal

A Crane 96803 is a single spring and would be a near drop in, I'd recommend a .060" shim to up the pressure. The main advantage of the Crane spring over the Comp is the lower coilbind height. So it can be shimmed to get the closed pressure up. It could be shimmed to an open height of 1.100" with the absolute minimum (.060") clearance to raise the pressure another 10-15# or so.

96803 Single
OD- 1.437
ID- .974
Seat Load- [email protected] 1.700 ([email protected] w/shim)
Open Load- [email protected] 1.200 ([email protected] w/shim)
Coil Bind- 1.037
Rate (lb/in)- 330

With stock valves/installed height, it's pretty slim in spring choices. At least with a SBC valve you could get offset locks to move it up or down .050".

However... you could get Crane 99943 retainers which are list as +.100" installed height. How that compares to stock, I don't know. But I'd think it at least would raise it .060" if not the full .100". That should get the installed height to around 1.750"-1.800". But without machining the heads to run a different spring cup and dual springs, that doesn't buy ya much.

Good luck,
Steve

P.S. I run SBC valves, around 1.800" installed height and a Pioneer Performance single spring. I believe it came out to 130-135# closed and 280# open on the exhaust and 300# open on the intake. Don't have any problems with valve float to 6000 rpm on an inverted flank intake lobe (.552" lift) and still fairly steep exhaust lobe (.536" lift but more duration for slower ramps).

Rich Thomson
05-03-2005, 02:48 PM
I had done alot of reaserch last year before installing a 520 lift cam with stock heads. I verified the 942 spring will work and is was an exact fit for the SC heads. I have stock valves and no shims were used. You will have to get hardened pushrods to hold upto the high closed seat pressure. I used the Ford 1.73 roller rockers and RM-7808-16 5-16" Pushrods 7.195" (1993-97 350 LT1) hardened steel. Check your valve lash and shim as needed. Replace all the lifters when installing the new cam. http://www.mn12performance.com/mn12how-to/cam-heads-intake/DSC00055.JPG

I will dig out and repost my tech findings later tonight. Dr. Fred turned me onto the 942 springs and I did the extra homework to verify no problems before installing them on the stock heads.

After reading this post if you are confused don't feel alone. After a month I finally caught on to the math and then understood it :)

----e-mail from 4/04----

After spending much time going back over the numbers again and verifying the data I have come to the conclusion the 942 spring will work. The Comp Cams coil bind number of 1.125" is incorrect. I verified the coil bind myself on a set of 942 springs. The real 942 coil bind is 1.070"! The factory Spring coil bind is 1.110". I recalculated the total lift from the numbers again.

I have a theory why Comp Cams lists the 942 spring coil bind at 1.125" when the actual coil bind is 1.070". The damper spring has a coil bind of .929" which does not seem to be an issue until you consider the retainer that Comp recommends for it. The retainer and cup each have .100" height which is .200" less coil spacing. Now Comp lists the recommended steel retainer for the 942 spring as 768 or 747. 768 & 747 retainers have an OD of 1.400" with a spring step of 1.030" and 1.050" which on a 942 spring would cause coil bind. The stock retainer has a spring step OD .915" and the same for the spring seat cup. The damper spring ID is .935" when installed in the 942 spring. The numbers I figured are below.

Damper spring coil bind .925"
Retainer and Seat cup .200"
=========================
Coil Bind 1.125"

The damper spring fits over the stock 3.8L retainer and seat cup so the actual damper coil bind on a stock head is .925" which is not an issue when considering coil bind.

So actual 942 spring coil bind of 1.070" plus .060" gives a minimum open height of 1.130".

1.65" - 1.13" = .520" max lift so don't try any cam bigger! Now you know where the 520 lift cam comes from!

Comp Cams 942 springs.

1.437 OD w/dampner

1.039 ID

132lb @1.65" Valve Closed seat load (stock head is 1.65")

301lb @ 1.15" Valve Open Load (stock is 1.18" height)

1.070" Coil Bind (stock is 1.110")

339lb rate spring

1.65” installed height

-.520” lift cam

===========

1.13” Valve Lift Total

-.070” Coil Bind Clearance

===========

1.060” Coil Bind Min @.070” clearance

AGAIN @ MIN .060" COIL BIND


1.13” Valve Lift Total

-.060” Coil Bind Clearance

=========================

1.070” Coil Bind Min @.060” clearance


The factory allowed for a .070" coil bind clearance. Using the recommended .060" - .100" spring travel rule to avoid coil bind.

CMac89
05-03-2005, 03:47 PM
Catwithboost sold me the 986 springs for the stock valves, for a .531/.339 lift cam (212/220 duration and 112 LSA).

Cmac89 is also running this cam and valvetrain combo...
He said everything fit nicely without modification, but I know he was having fuel delivery probelms last I checked with him. Now he is having probelms with his MAF/injectors, so as soon as he gets that worked out, he may be able to say how he likes the setup....

Take care!
I didn't have any problem at all installing the 986's. They fit in nicely. I havent had the car tuned/running good enough to see the performance of them though.

I would suggest you do some research to see if the 987's will work because they have the highest spring pressure.

I highly recommend this valve spring here at LSM eng (http://www.lsmeng.com/Springs.html) . The L1000 annihilator is the greatest valve spring ever.
specs:

Triple coil
ID-.635"
OD

CMac89
05-03-2005, 03:50 PM
Catwithboost sold me the 986 springs for the stock valves, for a .531/.339 lift cam (212/220 duration and 112 LSA).

Cmac89 is also running this cam and valvetrain combo...
He said everything fit nicely without modification, but I know he was having fuel delivery probelms last I checked with him. Now he is having probelms with his MAF/injectors, so as soon as he gets that worked out, he may be able to say how he likes the setup....

Take care!
I didn't have any problem at all installing the 986's. They fit in nicely. I havent had the car tuned/running good enough to see the performance of them though.

I would suggest you do some research to see if the 987's will work because they have the highest spring pressure.

I highly recommend this valve spring here at LSM eng (http://www.lsmeng.com/Springs.html) . The L1000 annihilator is the greatest valve spring ever.
specs:

Triple coil
ID-.635"
OD-1.680"
closed-440lbs
open-1260
bind-1.140"

Now thats a monster. We run those valve springs on our race cars. our redline moved up 800 rpm after we put those on and got 4 tenths better ET.

fastsc92
05-03-2005, 04:50 PM
Thanks for all the info guys. Its very informative. Once again though..its a toss up. Some say go with the 942's and others have the 986's. I basically just want to make sure they are a good upgrade over stock and won't float with the lift I have now. Granted its not super high, but I'd like to swap cams again maybe later.

Rich, I'd be interested to hear a lot more about your findings. I've always heard talk about the 942 springs, but recently I see many people going with the 986's. Did you have to get new retainers and/or spring cups? I'm already running a set of comp pushrods (7.195") And when i did swap out the cam last year I got some new lifters.

So my main concerns are that they fit into stock retainers and cups, and that I can get close to the installed spring height. I will shim if needed, but I'd like to stay away from that. I dont want to be stuck buying a set of springs and have them hardley better than the stockers......

I'm interested to know the installed height on these heads....but i don't have the valve covers off to measure that. If i knew that height then I'd have a little more information to work with as well as the stock spring specs.

Rich Thomson
05-03-2005, 07:27 PM
I have already added to my origional post. I cannot comment on the bee hive spring since it was not available at the time I did the engine. The 942 spring fits perfect you would mistake them for stock springs if you did not know. Stay away from spring rates that are 350lb (open) and higher as the 8M size bolt and pedistal mount will only tolerate so much stress before something breaks. In the pic below this pedistal broke due to stress caused by high spring rates. The 12.9 grade stud broke and damaged the pedistal mount. The excessive load will also cause accelerated wear to the cam and lifter as shown in the picture I posted above. That cam and lifter had 10k on it before I pulled the engine apart. So always replace the lifters when installing a new cam. These two surfaces wear together and a used lifter with a new cam is bad engine building technique.

Rich

http://www.mn12performance.com/mn12how-to/cam-heads-intake/DSC00034.JPG

sizemoremk
05-03-2005, 08:37 PM
I thougt it was OK to re-use roller lifters if they weren't scored or anything...

Does this mean I nee new lifters too??? I got me a cam on the way...

CMac89
05-03-2005, 08:42 PM
I thougt it was OK to re-use roller lifters if they weren't scored or anything...

Does this mean I nee new lifters too??? I got me a cam on the way...
You can reuse the lifters there's no problem there. I hope you got the 7.200" pushrods though because the stock ones will be too short. Atleast they were on my motor.

Rich Thomson
05-03-2005, 08:58 PM
I thougt it was OK to re-use roller lifters if they weren't scored or anything...

Does this mean I nee new lifters too??? I got me a cam on the way...

Roller tappet cams don’t require any break-in. You can use roller lifters over again on a new cam if they are in good condition. You do not know the condition of the rollers until you pull the rockers off. This picture shows the wear that the cam and lifter have on each other. The lines are wear grooves. You can rebuild your engine anyway you want I am just one person offering some answers to your questions. New lifters are about $100

http://www.mn12performance.com/mn12how-to/cam-heads-intake/DSC00055.JPG

fastsc92
05-03-2005, 10:28 PM
Great information Rich. I already have been running this cam for a little while with the correct pushrods from Comp. The cam works great. Rich, I'm glad someone was able to do some research about the stock heads and stock valves and springs. So it appears that you'll only get the advertised coil bind if you use the retainers listed for those springs... correct? But in our case we'll only see a max coil bind of 1.070", right?

It looks like the 942's will suit me well. I'm now concerned about the benefit of double springs vs single springs. The 942's and 986's are so close to each other and they both have their trade off's. I'm going to try to call Comp's tech line tommorrow and talk to Matt again and see what he thinks about the situation.

The 942's have a little less of an installed height (1.700) so that will make things a lot closer on the stock heads and easier to deal with. It it an issue that the stock springs provide more room for coil bind over the aftermarket springs?, or does that not really matter because they can support higher RPM's much much better...?

942's have a little less closed seat pressure as advertised and a higher pressure when open than the 986's. However, as you measured the pressures in a stock head situation, the numbers seem very reasonable. So it appears that these springs in a stock situation will only support a max lift of .520. This number isn't as high as i'd expect, however it will match this cam very well.

As long as they work with stock hardware, and give good higher rpm reactions, I'll be happy. Right now you can just feel their weakness when the car reaches 5k with the stockers.

sizemoremk
05-03-2005, 11:40 PM
Let us know what the comp cams guy says!

Also Rich, thanks for the input! Mine look good, no wear marks yet, so I think I'm good to go!

Thanks!

BlackbirdSC
05-04-2005, 10:08 AM
The question I have about the double springs is where the inner spring rides. If it's on the flat of the spring cup and retainer, it will be fine. If it's up on the step, it will break the inner spring.

Years ago, people were running a Crane double spring because it looked like it could handle .600" lift or close to it at stock installed height. When my old boss went to work for Crane in R&D for cam & valvetrain, he checked into why they were breaking. I think it was an 868 or 838 spring. Anyway, what he found was the inner spring was not seating and was coil binding well before the outer spring did. Once the inner springs broke, the outers only had like 70# closed and 180# open which quickly led to valve float and failure of the outers as well.

A double spring is better than a single of equal pressure because of the harmonics of the springs. A single spring will have a harmonic (usually tuned to very low or very high rpm) and a damper will be used to try and settle it. In normal driving, the harmonic is set at an rpm that the engine never stays at. With a double spring, the harmonic of the springs will be such that when one spring 'flutters' the other is not. So it makes the spring more controlled and stable. Oh.. another reason for the above Crane double spring failing... he found 1 case where it broke at sustained high rpm. Yup... it was held right at the major springs harmonic speed and it broke. I think it was like 5600 or 5800 rpm.

That's why there's so many spring 'types'. Different springs will have the major harmonic tuned different. For instance, a Nascar spring will have the harmonic tuned to a low rpm, like 3500-4000 or something. That works perfect for them since they run 6500-9500 all the time. But, for a street car, it would be a very bad choice since that's at an rpm level many cars see for extended periods of time.

Before the time of EECs and electronic rev limiters, the factory used 'controlled valve float' for rev limiters. Find a typical mid 70s car that's still bone stock and put a brick on the gas pedal. It'll never see 5000rpm. It's not because anything's wrong, that's the valves floating as intended. It'll run like that until the valvetrain fails.

All springs have a harmonic. Any spring manufactured that says their springs don't is lying.

fastsc92
05-04-2005, 10:42 AM
Wow, very very interesting information. Thanks Blackbird......

92bird
05-08-2005, 06:08 PM
I've been running comp cams 942 springs in my SC for over 4 years now with absolutely no problems, and I have Fred's .520 lift cam.

It accidentally saw 7k rpms a few times while doing a burnout (limited slip gave out, one wheel peel, DOH!)

No damage at all.. I routinely rev it to around 5,500 and all is well.

Jeramie