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OK, so just when I think I have things figured out...it turns out that I don't. I finally settled on a cam for my 406, now I'm trying to figure out how to make it work.

I chose the XE274H after a bunch of dyno simulations. To make things easier on myself, I figured I'd go with a complete kit (includes springs, retainers, and locks) Turns out that the kit springs are 1.254" in diameter...and my 492 heads are cut for larger springs. That doesn't seem like it's going to work without some pocket reducers or something. No problem, I figured I'd just skip the kit, buy the springs and make sure to get larger diameter ones. I also figured I'd reconsider the cam and put the Voodoo cam I was considering back in the running as well since the kit thing was out the window. The Voodoo cam recommended springs are also 1.254", so same problem there.

So...I'm trying to find larger diameter springs to work with either the XE274H or the Voodoo '103 cam. After staring at the Jegs and Summit webpages for a couple of hours, now I'm completely lost.

I did some measuring last night. The spring pockets are cut to 1.500", the springs that are on there currently are 1.450" OD (widest measurement I got), and they have an installed height of 1.750". The current retainers have an OD of about 1.380" (It seems odd to me that it would be smaller than the spring, but...its not that much smaller...and they were working, so...)

Questions:

1) The spring in the XE274H kit (981) is listed at 105lb closed, 295lb open. Should I be more concerned about matching the open or closed figure? I can get in the ballpark, but...not identical. Similar story on the Voodoo cam.

2) What does the different spring do to my redline? Seems like the spring would be crucial for this, yet I don't see anything in the catalogs to indicate that.

3) How come the spring rates are wildly different, yet the open and closed specs aren't off that much? Shouldn't they go hand-in-hand?

4) Is there really any difference between an advertised spring diameter of 1.500 and 1.450...or is it just different manufacturers' terms for the same thing?

5) Can I reuse my existing locks and retainers with new springs? Should I be concerned about them being 1.380" and not 1.450"...or is that the proper size for a 1.450 (1.500?) spring?

6) For my (relatively mild) application, do I really need to worry about anything aside from coil bind, installed height, and being +/-20% with the open and seat pressures from the cam's recommended spring?

7) If the cam and the spring need to be matched so closely, how do people buy preassembled heads that have the right spring for their cam?
 

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well I'm no expert but why not get the spring pocket reducers and buy a complete kit and be done with it...it, IMO, seems like it would be the easier way to go with somewhat guarenteed results...


Now if do mix and match parts having too little spring presure will I suspect lower your upper RPM limits and lower the valve float point too. Again I'm not an expert but I would think you would be better off with a little too much pressure then too little...

Question if the springs you are looking at have too little spring pressure could you not shim them to get the required spring pressure? You will then have to re-verify coil bind with the shimed spring...but that would allow you to get the pressure you need...just my 2 cents worth (not sure its worth that much):)
 

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69NovaSS said:
well I'm no expert but why not get the spring pocket reducers and buy a complete kit and be done with it...it, IMO, seems like it would be the easier way to go with somewhat guarenteed results...
Yeah, I may just do that too...I was thinking that after I re-read what I had posted.

I would like to learn a bit about how this stuff is supposed to work though.
 

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I went with the 274H and the 981-16 recommended springs on mine. I set the installed height myself and used mostly .015 and .030 shims to get the correct height. I would think if you went with that set-up with the bigger pockets you would use these also to get to where you want to be.

http://store.summitracing.com/partd...4294856995+4294856899+4294788546&autoview=sku

The only thing I don't know is these are .060 which would have been too thick for my installed spring height, but maybe not for your's since the pockets have been cut?

I'm just speculating here.:)
 

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my camels were ported etc in the early '80's. cut for the big springs etc etc etc... i used the "beehive" springs. never had a problem, this was a thousand years ago... the spring locater do-hickies sound good ta me, but i never used 'em, don't know if they had 'em or not "back in the day" :rolleyes: :D :D

i set my height also with assorted thickness VSI inserts... measure, measure, measure ;)
 

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Why don't you just call the cam vendors and get their recommendations for a complete cam, springs etc. for your particular heads. They have been through all this many times over and can probably save you a lot of guess work. They can answer all your questions and tell you all the specs for pocket size, install height, recommended retainers, keepers etc. Why not get it right from the horse's mouth so to speak? Just a suggestion.
 

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DriveWFO said:
Out in the barn here, we set our installed height using some washers and a ruler.

I think your on to something there. Why waste all that money on precision measuring tools when you can save it for NOS.;)

Hey Patman, here is a pic of the pockets on my new heads. They measure out at 1.550 and the springs are 1.460. As you can see the pockets dia. is much larger than the springs.



Sorry typo, the spring dia. should say 1.260
 

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I dont know what type of heads you have but I was reasearching this for myself and the spring locators are not necessary unless you have aluminum heads. If the springs move around they could score the aluminum heads but iron heads are no problem.
 

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Lot's of questions but you may be over analyzing the problem.

You might want to measure the ID of the springs and the OD of the guide boss at the base. If you look at spring shims they don't locate by the OD. They locate at the ID.

Also you won't find answers at Summit or Jegs.

Go to the Comp Cams web site and download the catalog PDF. You'll find all the springs dimensions and specs there.

Spring rate is the rate of change between open and closed. If you just look at pounds you don't know the rate. You need to know pounds at installed height (closed) and pounds at full lift (open) since lift and installed heights vary just knowing pounds in not enough.

Free height and coil bind height are very important specs also.

Here's an example of how two springs could have the same open (300) and closed (105) pounds but different rates:
 

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Discussion Starter #12
Thanks for the info everyone...

These are cast iron heads, so I don't need to worry about the springs galling the aluminum. Someday if I'm real lucky I'll have to worry about that problem.

I completely forgot about the ID of the spring being able to locate it...that makes sense...and I did not measure that. Hafta do that before I...

...call the cam manufacturers and ask them for advice! Golly! What a smart idea! Now why didn't I think of that? :)

Paul, thanks for the spring rate info. I get it now...guess I was just looking at too many numbers that night. Good advice about going to the cam catalog PDF instead of the stores' pages, I'll peruse those too.

Pat
 

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Kinda on the same topic, when do you guys replace springs? Im running a set that come advertised with 200 seat pressure and my handy moroso tester reads 160 at the seat (valve moves at 160). Now they have read 160 since i first checked them at about six passes, motor has 28 passes now with 160 at the seat. My Q is should I worry about swapping them? Im running a nice street solid roller with about 580 lift, im thinking i should be able to get a couple seasons out of these springs, but I dont like taking chances either. Whats a good point to replace roller springs? Thanks

PS: my search didnt come up with anything about replacing springs
 

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63IIPost said:
Kinda on the same topic, when do you guys replace springs? Im running a set that come advertised with 200 seat pressure and my handy moroso tester reads 160 at the seat (valve moves at 160). Now they have read 160 since i first checked them at about six passes, motor has 28 passes now with 160 at the seat. My Q is should I worry about swapping them? Im running a nice street solid roller with about 580 lift, im thinking i should be able to get a couple seasons out of these springs, but I dont like taking chances either. Whats a good point to replace roller springs? Thanks

PS: my search didnt come up with anything about replacing springs
first off. you can and should shim the springs to get the required seat pressure. Just make shure they don't bottom out at full lift. If a spring looses 20lb or more, i'd replace them.
 

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63IIPost said:
Kinda on the same topic, when do you guys replace springs? Im running a set that come advertised with 200 seat pressure and my handy moroso tester reads 160 at the seat (valve moves at 160). Now they have read 160 since i first checked them at about six passes, motor has 28 passes now with 160 at the seat. My Q is should I worry about swapping them? Im running a nice street solid roller with about 580 lift, im thinking i should be able to get a couple seasons out of these springs, but I dont like taking chances either. Whats a good point to replace roller springs? Thanks

PS: my search didnt come up with anything about replacing springs
You mention advertised seat pressure but you didn't mention what your installed pressure was when you put them in or what height you installed them at.
Seat pressure is relative to the height of the spring when installed. The seat pressure should be listed at an installed height. If you didn't install your springs to spec height then it may have been 160lbs from the beginning. This also means the open pressure is less than you think.
 

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Thanks guys

Im inclined to think my measuring tool is off.

When I mocked/assembled them I used a starrett spring testing tool at the installed height spec (1.850 in this case) then shimmed the springs to the spec height. I didn't calibrate the moroso on car spring tester during the assembly so im inclined to think there is some error in the reading. Oh by the way the springs did read 200 at installed height when I installed them, hence my concern. So Im going to remove a spring and recheck in the bench spring tester so I know where im at. Ill also recheck the installed height. Thanks
 
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