Hi all,

I need some advice with spring selection for my build which I'm currently assembling. Its a short cam, high lift big valve combo.

Currently it has a baby cam due to government inspection limitations. I will probably go a size or two larger. I also have a TVS 1900 but that is a project for when the driveline is better sorted.

This is my valvetrain:

• Cam Lunati 20080720 262/270; Duration @ .050 (Int/Exh): 211/219; Gross Valve Lift (Int/Exh): .507/.515 (0.575/0.580 with 1.7 rockers);
• Lifters HyLift Johnson 2148 with snap-ring;
• Pushrods BTR 5/16 0.080 wall 7.6" long set using Straub half lift method;
• Rockers 1.7 Scorpion;
• Intake Valve solid SS 2.08 + 0.100 long 127 grams; and
• 1.8" install height.

I got the PAC1218's right at the beginning of the build but I think they are now just too soft for the 1.7 ratio rockers and the 127 gram 2.08" valve. I'm not worried about selling them on to a LS guy.

Some springs I have shortlisted:

• PAC1211x beehives 384 lb/inch, 130lb @ seat, 353lb open at 0.580 lift - I can install at 1.750" which gives 150lb seat, 372lb open;
• BTR Platinum Duals (by PAC, 12905) 392 lb/inch, 160lb @ seat, 387lb at 0.580". 1.3" retainers are another $45. Very popular with LS crowd and also sold by a few different lables;
• BTR Max Pressure Duals (by PAC) 450 lb/in, 150lb @ seat, 422lb at 0.58", same as platinum's, recommended by BTR for use with roller rockers.

The 1211x I can get local while the duals I would need to order. Cost is around the same.

I have stuck with 1.3" ls duals as the retainer is very small and install height is 1.8". Price is good too.

Whats the best spring? I would like to have room to grow without collapsing lifters etc. Current setup only really needs to be stable to max 6500 but short block is good to 7000.

I'm interested what has worked for others? Im especially interesting in hearing from other 1.7 ratio rocker and 2.08 valve aficionados.

 

Install the spring recommended by the cam or a spring with similar seat pressure. If the manufacturer can not provide you with specs for a higher lift ratio, you will need to do a lot of calculations and measuring.

You'll need to check piston to valve clearance and for coil bind. You'll need to make sure the bottom of the spring retainer doesn't hit the top of the valve stem at max lift.

Once you know those numbers, you can see if a particular spring will work with your combination.

 

Personally I am running 1.55 duals on 2.02s.

Boost will affect your pressures as well.

I would not run a Beehive in that application.

I just swapped to a Lunati Bootlegger.

232/244 @ 0.050
.554/.554 (.627/.627 w/ 1.7)

I am at 150 seat and about 450 open.

 

Thanks Fast355, what lifters are you running? Any noise, ticks?

How many miles/passes?

Thanks!

 

Lunati have two recommended springs with the PAC1218 the stiffest. I think the next Lunati spring up the ladder is almost identical to the second spring I listed.

 

Rhoads V-Max. They sound like a well oiled sewing machine or a tight lash solid. But that is by design because of the high bleed down for less duration at lower engine speeds.

 

Thanks!
What rpm do you shift at or max rpm is it stable to?

 

Not sure what it would be stable to but no doubt it could run atleast 6,200. It has a bit more spring pressure than specified by Lunati. With the smaller cam I was shifting at 6,000. With this cam I am probably not going to spin it any higher either. If I spin it higher it will only be 6,100 rpm or so. The intake manifold and header choice somewhat dictate the RPM I run in. The marine MPI ported dual plane will only work effectively to around 6,000 or so. Works GREAT for off-idle and midrange torque though. The tri-ys also do not work as well as 4:1 headers on the top-end but work exceptionally well in the low-midrange.

The spring Lunati specs has 3 lbs more seat pressure and 50 lbs less open pressure. Negating the pressure increase from the lift of the 1.7 rocker I actually have about 15 lbs more open spring pressure than called for. Lunati 73925-16 This is the 1.3" od double spring Lunati calls for. The 1.55 springs end up a little more aggressive in the spring rates for a comparable spring. The 1.7 rocker actually puts more pressure on the lifter than a 1.5 would.

 

I will also say that while I prefer the dual springs. I put together a Vortec 350 on the cheap that went into a Street/Strip 1978 Camaro. Stock vortec heads with the PAC1211x springs installed at 1.72". It had another Lunati Bootlegger 232/244 @ 0.050 cam with .554" lift. That one has shifted at 6,500 for 2 seasons at the track. Those vortecs still have pressed in studs and self aligning 1.5 rocker arms.

 

I just checked the Lunati Lobe spreadsheet and the Moonshine lobes are more aggressive than the Voodoo lobes I have.

I'm leaning towards the second option using the BTR/TFS/Lunati etc. polished PAC 1905. I can get these and other required parts for about $200 from summit with shipping.

The various kits run a little more, have longer delivery times and have 0.500" stem seals (I have 0.530").

Do you think I need the stiffer spring of the third option? Maybe for future mods. Are there any draw backs of this option do you think? I think they are about the same rate as your springs.

 

Whats the coil bind specs? Check to see how far they are from bind at the installed height you set them up at

that cam has alot of lift for duration with that rocker, and a fairly big valve. Rpm wont be too high tho with 211 deg. I would normally go 150 seat and closer to 400 open. The beehives should handle it. I like the dual springs tho, never really used behives much.

 

For the duals at 1.8" install coil bind is 1.015" for the 392 lb/in spring and 1.080 for the 450 lb/in spring.

Behive is much closer especially if installed at 1.750".

I think I'm just past a beehive. The intake valve is 127 grams, I weighed a 2.02 at 117 grams. They are much heavier than LS valves.

I'm trying to decide between the 392 or 450 lb/inch duals so I can order them today.

I think the 392 lb/inch would be fine except that monster 2.08 valve at 127 grams. I was truly surprised when I threw it on the scales.

If there is no draw backs with the 450 spring and the rest of my valvetrain I may as well just run them.

 

Either one sets you up abit further from bind than i’d like but should be ok.
If you have decent lifters the extra pressure wont hurt. Max duals setup at 1.75 would be bit better for coil bind clearance but would give you 170 lbs seat pressure. While your valve is rather heavy the duration of the cam is small so your setup should be done by 6000-6200. Either spring would handle it imo. If you plan on bigger cam or blower down the road, i would want that max dual spring. I would set them up at 1.75” height. 170 lb seat 420’s open pressure will control that valve with most reasonable cam lobes to 6800-7000 rpm. With blower boost the bit extra seat duration would be nice.

 

Orr this is very good and succinct advice. Thank you.

You make a good point about shimming the springs. The dual springs both allow this option for the combo to grow while still good for reasonable lift.

I went ahead and ordered the Max Pressure spring, I ordered it under TFS-16306-16 from Summit for $149 as it was in stock ready to ship. For now I will just install at 1.8 as they are more spring than I need at present.

I'm still getting my head around running this spring, but everything I have read about this spring in its various guises (AFR 8019, BTR Max Pressure, TFS 16306 etc.) indicate it is the correct spring for me to run and will allow me to grow the combo later.

If I had a much lighter intake valve I may be tempted to run the 392/lb/inch spring. But I'm sure we have all been in the scenario before when we purchased something which just was not quite up to the job and regretted it. In the end there was $39 difference and not really worth taking the chance.

My main concern was the lifters with these spring loads, but Fast 355 is running 150/450lb rhoads FB lifters which possibly come from the same place as mine and these springs I understand are the standard HR spring fitted to TFS LS1 heads and from what i can tell those guys frequently just run LS7 lifters and shift at 7k.

Orr and Fast 355 thanks for your help with this, parts are on their way.

 

Yeah i’ve run 165 lbs and 415 ish open on my 383, with a afr 195 head and afr 8019 spring. Good stuff
i’ve run 190/450 on morel hyd lifters

 

I thought I would pop back in and update this.

I ended up going with the 450lb PAC duals as planned.

BTR do all parts as a kit for the LT1/4 with 0.500 seals, but this was out of stock, and I needed 0.530 seals so ordered the parts separately.

I nearly went a 1.46 PAC spring with similar rate, but even lightweight retainers are about 30 grams.

I got the springs from Trick Flow under pn 306 I think. BTR retainers and comp locators ( BTR locators on some weird special order which never materialised).

The BTR retainers seem to be +0.30 compared to the comp 787.

I compared the BTR retainers to comp 787 for 11/32 beehives 16 vs 12 grams.

The duals vs my PAC beehives 95 vs 75 grams.

So about 10g increase in effective mass over beehives.

Not much weight difference considering the massive jump in spring rate. And how much heavier would a 1.46 spring and retainer be?

See pics.

I also had a closer look at my lifters, nice units.









Typo

 

Those are tiny dia am I seeing this right?
May be too late but ever considered using a 8mm valve? Now would be the time to do it.

 

They are 1.275" and what comes on TF LS, 11R heads etc. and upgrade on AFR SBC heads. 7,000+ rpm HR springs. Have a look at what the SBF and LS guys are doing with them.
They are nice looking pieces. You can get them in a full kit for about $230.
As you can see they are nearly as light as the beehives but have about 45% more spring rate.
If I went again yeah I would consider 8mm valves, but I have saved so much weight with this spring setup, 14 g in retainer alone vs 1.46" I have offset the heavy valve already.
Time will tell soon how they run.


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