roaddawg

I have a lg4 that i am going to put a zz4 cam in what valve springs should i use btw the heads are 081s

RB83L69

Look at Comp 983 with the correct retainers and stuff

I would not recommend anything GM has to offer

DM91RS

I'm trying to understand about installed heights and cam lift limits.

How does one calculate the .510 lift of the ZZ4 with this spring concerning coil bind?

CCA-983
Specifications:
* Single spring, no damper
* Inside diameter: .836 in.
* Seat load: 105 lbs. at 1.700 in.
* Open load: 310 lbs. at 1.200 in.
* Coil bind: 1.150 in.
* Rate: 410 lbs.


Also does the extra lift over .500 hurt anything with this 1.25 dia. spring as has been posted in the past. Or....am I concerning myself with something unnecessarily?

Thanks

DM

AJ_92RS

At 1.7" installed height, those springs won't work for lift over .500"

The installed height of 1.7" - 1.15" at coil bind = .550"
Subtract the .060" for coil clearance and you're left with .490"

BTW, what is the OD of those springs? I have yet to see it published anywhere, including Comp Cams website.

RB83L69

I'm sorry, I fat-fingered the part #.... should have been 986

The 983 coil-binds at .550" from its installed height, which is a good .100" shy of where you'd like for it to be for that cam.

DM91RS

AJ_92RS I have not seen the dia. of those springs either. always assumed them to be 1.25.

Quote"
RB83L69 I'm sorry, I fat-fingered the part #.... should have been 986 " Quote

I'm sorry if I'm fat headed...I want to get this right for this next engine and this needs to sink in better.

With this spring:
CCA-986
* Seat load: 120 lbs. at 1.750 in.
* Open load: 280 lbs. at 1.250 in.
* Coil bind: 1.150 in
one would have a safe lift max of .540?

With this spring:
CCA-987
* Seat load: 121 lbs. at 1.800 in.
* Open load: 388 lbs. at 1.200 in.
* Coil bind: 1.150 in
one would have a safe max lift of .590?

Am I correct with these fiqures?

The reason for asking is if I choose to run 1.6 rockers on the ZZ4 cam the exh. lift will be up to .544 and the 986's which I had at first chosen looks to be just out of range by .004.

Does this matter?

RB said if I can correctly remember was to err on the larger side if there's any question in choice. The prices are exactly the same so that is not a factor.

Thanks for the help
Darrell

AJ_92RS

Yes

Yes

As far as which to go with, that's a little out of my league. The second spring would be the stronger of the two (obviously), but that's doesn't mean it's always needed.

IIWY, I'd call Comp Cams and ask them. They'll be able to give you the best answer.

DM91RS

Thanks AJ..

Glad to see that my calculations were correct. Now I'll find out about the pressure diff's.

DM

RB83L69

Your calculations agree reasonably well with the ratings that they give those 2 parts.

Since that isn't a particularly aggressive cam, the 986 should work fine, if set up at 1.700" - 1.750" installed height (typical for stock heads and valves). You can bring them to that height range easily with offset keepers to increase it, or shims to lower it.

DM91RS

Thanks RB...now to finish my parts list.

DM