Knewsom62

1995 Z28 rebuilding currently and looking for valve springs for the CC503 cam. PAC1218 seem to fit the bill but im not sure if they are direct drop in for the LT1, meaning they can reuse the retainers and locks.

If the PAC1218 is not a direct drop in the I am looking at the Lunati 73925K5 kit. However it's springs are acceptable to a max lift of .630. Will this be too much spring for the CC503 with 1.6RR and risk damage or will I be fine?

Don't crucify me, it's my first build ever so any help would be great. Thanks yall

350 groundpounder

iTrader: (5)

I have the pac 1218s in my lt1. They have been great for 30k miles with a custom cam with .533 lift.
You can't go wrong with the double valve spring set you listed either. I would go double valve spring on any cam that's pushing high lift or aggressive lobes.
The CC503 is mild , the pac 1218s would handle that cam easily.

Knewsom62

ate the Pac1218s complete drop in replacements or did 6oi have to buy retainers and locks? If you had to buy them what did you get? Thanks man

350 groundpounder

iTrader: (5)

Here ya go. I always use new, cheap insurance on your build. Zoom in to see part #'s

BALLSS

Get the Lunati kit, period. the 1218 will need different retainer but I believe uses the 7 degree lock (stock)

350 groundpounder

iTrader: (5)

1218's use a 10 degree, zoom in on picture posted above.
Don't count out the pac 1218s , rock solid spring. The lunati double springs are good but have had reports of failures and not just a few reports.
Also when buying springs keep an eye out for big spring company names like, comp cams, lunati, Pac and do your research as to where they are having their springs made currently to avoid Chinese or Mexican made sub par products. I'm not saying all products and springs from these countries aren't quality but do your research.
Everything I have researched about Pac has brought back excellent american made high quality control reviews and its why I choose them in my engine builds.

ACE1252

From my understanding, PAC used to make the comp beehive spring. They switched to a different company and that's what gave the comp beehive a bad name as they started breaking springs left and right after they moved away from PAC.

My email thread to/from PAC in 2019 on a 1518 replacement......


Good morning. We have 1218, 1218x, 1219 and 1219x. All the springs would work great.

I think the 1218x would be your best choice and near the same spec rates. They bump up slightly with the “X”. But the “X” will provide better performance over a longer period. All your hardware will work with this spring as well. I hope this helps.

Kind regards,

Danny Hester
Technical Sales Representative


From: Eric Rorrer

PAC,

I bought a set of PAC-1518 springs around 10 years ago and am looking to replace them after around 30K miles as a preventive measure.

I don’t see the 1518s for sale anymore.....but the PAC-1218X/19X caught my eye as the closest thing to the 1518 series. Are both a drop in replacement for the 1518s? I’m looking to reuse my existing retainers and locks if possible.

For reference, my retainer hardware is as follows(car is a ‘96 Z28...LT1, CC503 cam)....

CCA-4705-16 – locator

CCA-795-16 – retainer 10*

CCA-614-16 – valve lock 10*

My cam lift with 1.6 rockers is 0.536/0.544”, so the reduction to 0.600 or 0.625” max lift should not be an issue for me....I think the 1518s were good for around 0.650” if I remember right.

Thanks,
Eric R.

350 groundpounder

iTrader: (5)

Those 1518s were supposed to be some nice springs too. I will be looking to replace my 1218s since they have 30k on them right now. Im definitely sticking with PAC.

Knewsom62

I got the Lunati kit, now the cylinder head shop is asking for More information than I have. He said something about a VC number or spring tension for the CC503 at the closed position. I know it has a install height or 1.78" but when we have it at 1.78" the spring with retainers is pushing 160lbs. is this ok for the cam? I don't want any damage to the valvetrain and of I need to order different springs then I will but I think these should work fine. Any help?

350 groundpounder

iTrader: (5)

That's why the pac beehives would have been better for that cam. I would use double springs for a much more aggressive cam profile than the cc503. That being said, if you find out that its too much spring pressure a machine shop can machine down the area where the spring sits to reduce spring pressure and raise spring height.

Knewsom62

is this something i need to talk to comp cams about or does anyone have any info on that spec?

350 groundpounder

iTrader: (5)

160 is pretty high for a cast core cam. They say 120-145 is the range you want to be in. That being said the time you get a few thousand miles on the springs pressure will drop a little.
Then you have the old saying-Too little spring pressure is always worse than too much.
Maybe someone with extensive experience will comment, if not call around for a definitive answer.
I always choose billet core cams so I don't worry if pressure is a little higher than normal.

BALLSS

Can you provide any of these failure reports?

Never have heard of one but like any valve spring they can fail. Typically the reason is operator error though (wrong installed height)

I bought my Lunati springs from Lloyd Elliott who highly recommends them, especially over single spring bee hive types.

MuhThugga

So, the Lunati spring has a seat pressure rating of 153lbs at 1.810". At 1.780", I'm getting ~165lbs of seat pressure, and with .536"/.544" of lift, the open pressure is ~368/371 lbs. The other thing to look at is with the relatively low lift of the camshaft, the valve spring will be .144"/.136" from coil bind at full lift, which isn't ideal and you may run into issues of spring surge since I don't believe those springs have a damper.

Looking at the 1218, you would have 130lbs at 1.800" installed height, and ~297/300lbs of open pressure, which is much more manageable for a cast cam core. Those pressures will also be much easier on the lifters and the rest of the valvetrain. Also, the 1218 reaches coil bind at 1.200" as opposed to Lunati's 1.100, so you would be within .114"/.106" of coil bind, which is more palatable.

At a minimum, I would call Comp and verify the cam can be run with the Lunati's spring pressures, but I personally recommend returning them and getting the 1218s or a spring with similar specs.

350 groundpounder

iTrader: (5)

Thanks for the better in depth explanation Muh Thugga. Can't go wrong with the PAC 1218 on this set up.
******, I'm not gonna dig up all the stuff I have read and seen over the yrs. I agree sometimes it's installation error for sure, but I have seen and heard of too many issues with them to trust them in my motor. That's just my opinion. Some have great success with products and some don't. Product choices are so highly debatable. And many times a seller will push a certain product because they are a retailer of that product. I research every product I put in my car from many different sources to gather a honest opinion on it. Im certainly not discrediting your opinion on the lunati springs, and I'm sure you have way more automotive knowledge than I do. Just IMO the PACs are better for the cc503 application.

Fast355

I have used Pac1218s in low reving Vortec 350 applications. Prefer a dual spring for anything approaching 6,000 rpm. Friend of mine had a Summit low lift LS truck cam with the Pac1218s in a 6.0L. Floated the valves at 6,200. Swapped in BTR dual springs and it sings past 6,500 now.

BALLSS

350

No offense taken...although I have never heard of the Lunati failures for the springs we are talking about. Comp 918's fail and I am a member of the 2 piece 918 club. IMHO the majority of spring fail is operator/installer error other than the Comp 918 debacle when they switched spring manufacturing offshore

OP

your cam should have come with a "cam card" which details its specs, including recommended valve spring. If you can't find the card than contact Comp for one. Unfortunately because its a comp cam it would recommend 26918 or the lighter 26915 springs which I would never put in a lawn mower let alone a SBC

Lloyd Elliott has forgotten more than any of us will ever know about cams, valve train components. He advised the Lunati kit for me after my 918 broke. I do have a different cam, Comp 466 XFI though but it is the same spring spec as the Comp 918

If you can set the Lunati up at 1.800 installed height the open & seat pressure would be fine although at 1/75 IMHO they would be fine with the 503 cam. They are a direct replacement spring for a Gen 2 LT1 motor

If you use a bee hive spring, you should check them minimally every 10k mi...which means pulling it and doing a pressure test and closely look for any cracks. IMHO very tedious maintenance for a street car. a single spring breaks and engine damage typically is massive vs a double spring where the valve won't drop if just one of the springs breaks

350 groundpounder

iTrader: (5)

The added safety net of a double spring is definitely a benefit. My pac 1218s have 29k on them now, I better check pressure on them before spring comes.

ACE1252

Seems like overkill. The stock LS series is beehive right? I think they expect those springs to go 100K+ without breaking or cracking. If you are tracking it every weekend, winding it out at every opportunity, then it makes more sense.

350 groundpounder

iTrader: (5)

Yeah i was thinking 30-50k is a good range to check spring pressure with a mild cam and beehives. I may report back to this thread when i get mine checked at 29k in the next month or so.