Yellow Bullet Forums banner
1 - 20 of 38 Posts

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #1 ·
Just setting up some 3128 T&D Rockers on my Brodix -3Xtra heads. I’m pretty sure I have the stands shimmed as close as I can get it to perfect.
But, the rockers look pretty damn close to the retainer to me. I realize that the rockers don’t move up and down like a regular rocker does on the stud when the pushrods flex at rpm, but I figure there must be some minimum clearance to keep the retainer from kissing the rocker body at high rpm, no?
Or am I being paranoid?
The pictures below might not be the best angle, but it’s not much more than what you can see there. Intake and exhaust respectively:
Automotive lighting Automotive design Automotive mirror Motor vehicle Automotive exhaust

Automotive tire Coil spring Tire Tread Automotive exhaust
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #3 · (Edited)
Cam specs are 286/300 @ .050”, .836”/.816”. Pretty sure I need a triple spring for that.
To use lash caps I would have to change the locks (which isn’t a big issue) but I will most likely need a new set of stands from T&D, or at least some longer bolts, since I’m using a thin (.040”) and thick (.080”) shim under the intake stand as is.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #7 ·
Thanks guys. I’ve read and re-read the T&D instructions to the letter, as well as anything else I could get my hands on. My kit came with the .750” tool, so I followed the instructions and subtracted half the difference between .750” and the lift on the intake and exhaust, respectively, from the required amount of shim. That’s my understanding of what you need to do, based on the instructions, which leave a lot to be desired, tbh.
I had to make do with the shims I had, which were only .080” and .040”, so I’m not saying it has precisely the right amount of shim, although I was pleasantly surprised that it was close.
I’ll post up the numbers later, as I wrote them down but left them in the garage.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #8 ·
Looks like you have +.05 locks. Are these longer valves than came with the heads?
You don't need any where near a triple spring but that's another subject.
How are you setting up the stand height? Stand height dictates rocker geometry and rocker geometry is all that matters. It looks to me like you need more shim...more stand height but that may not be the case. Use the tool and follow the instructions to the T. Don't "guess". Do NOT use lash caps to correct a geometry issue.
Thanks for your advice.
I’m not sure what locks I have. Those are the same locks and retainers that came on those heads when I bought my original motor from Shafiroff in ‘08. The springs are new CC #948 springs, which I ASSumed I needed, since that’s what came on those heads as well.
I’m happy to change the springs and retainers, if someone can tell me what would work with those specs?
The valves are longer than stock Chevy length valves: the intakes are +.350” and the exhaust .100”, iirc. Spring installed height is 2.10”, as specified, and that required the intake springs to be shimmed, but not the exhaust, which were all very close to 2.10”
I did follow the instructions supplied by T&D, and I did use the tool they sent, which was the .750”, although as I said, I couldn’t get the exact height I needed, as the kit only came with two thickness of shim (.080” and .040”).
I really have no intention of using valve lash caps.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #9 ·
I run 9000 rpm, 1200 lbs open with .950" lift with a small diameter PAC dual spring.
Wow, what diameter spring is that? I have no intention of turning my motor more than 7500.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #10 ·
I have T&D rocker stands also, but with Dart 355 cc heads, and triple springs.. I would not use the taller stands, unless you have taller valves than what the heads were manufactured for. The taller stand brings roller alignment with the valve problems. Same goes for lash caps, unless you have Ti valves. The little tool supplied with your set gets you your correct height. With a .040 and a .080 shim, you are raising the stand .120. There are .125 taller and .250 taller stands available. They swap out stands, as long as the engine has not been run. Your best bet is to call Sheldon @ T&D. Taller stands do not automatically mean longer stand bolts, as the taller stands are raised in the area above the bolt.
Make SURE you are using the absolute longest stand bolts your heads allow without bottoming out in head. With triple springs you want as much thread attachment as possible. They have many different length bolts available for this.
Advise you print their Parts page for reference as to what's available in bolts, but stand bolts must be flanged style.
I'd measure the retainer clearance with a wire gauge before you call Sheldon. Have exact information written down before you call.
Thanks. I’m starting to wonder if I need is some different locks to reduce the retainer height compared to the valve stem tip? That would then give me some additional clearance between the retainer and rocker. I haven’t checked to see what retainer locks I have.
The only problem that would cause is that the exhaust springs installed height might have to be slightly less (say, 2.05” vs 2.1”), although that might not even matter? I say that because I don’t have any shims under the exhaust springs, so I can’t drop them any deeper into the spring pockets.
Starting to think I don’t need these damn bigass springs, period, based on what you guys are telling me.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #11 ·
Just checked the original build sheet from SRE. Those are indeed +.050 locks. Well spotted, Mr. Foxwell(y).
 
  • Like
Reactions: scott foxwell

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #15 ·
PAC has quite a few 1.50" duals with those specs. Certainly nothing you need.
If you go to a smaller dia. spring you'll need new retainers.
Do you have a spring p/n for what's on the heads? It would be good to find a more reasonable spring that fits your retainer. The PAC 1324 is a 1.625 spring that is good for .850" and will install @ 2.00". If you don't mind buying new retainers, you have lots of options in the 1.50-1.55 dia range.
The springs I have now are Comp #948: 1.645 diameter, 686 pounds per inch spring rate. They’re good for .910’ lift @ 2.1” installed height, so I’m thinking if I reduce the installed height to 2.05, by changing the locks to standard height, I should still be able to use the springs and retainers I have now and that should give me sufficient additional clearance between the retainer and the rocker, no?

What do you think the minimum clearance between the rocker body and the retainer should be?

I wouldn’t mind changing the springs, but these are brand new ones I just bought a few months ago, and I would need to change out retainers as well.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #18 ·
I know you say your not gonna rev this eng over 7500 but things happen with power adders, you may also want to look at the installed height from coil bind to set these up, your coil bind is 1.130in + min gap for coil bind .055in + cam lift .836in = 2.02in installed height. New seat pressure would be 386 & open will be 950-960. Ex would be slightly different but alot closer .
Set up at 2.100 is way off on intake side .134 and ex would be .154 and a bit excessive to coil bind and you may get spring surge .055-.065 in from coil bind controls the valve more, you hiccup with nitrous from floatin valves or one sticking open your gonna hear a BOOM and see you hood move. Dropping your installed height may also fix your clearance issues on the retainer
Thanks,

I hear you on the over revving. I’m going to put a 7600-7700rpm chip in the limiter and shift it at 7200-7300 to make sure it doesn’t overrev, but I would like to stay off the limiter on nitrous for sure.
Are you saying that I can and should drop the installed height down from 2.1” with this spring, or that I should change out the springs?
I always ASSumed that the more clearance you had from coil bind the better? I learned something new tonight. Thanks for this.
I had no idea that I had way too much spring in this thing. I’m not a fan of using stiffer springs than necessary, and I know that a lot of people err on the stiffear side, which is just more stress on the valvetrain and robs a bit of power.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #19 ·
Personally I don't think you need near that much spring pressure. I would take the inner spring out and see what you have at your minim installed height. You'll need a spring scale to do that. Don't rely on advertised coil bind. Put one of your springs in a vise with the retainer and squish it till it coil binds, then measure it. I agree with Saviour68 on how to go about it. Find your actual c/b, add .05" for clearance, then add your net lift (gross lift - lash) and that would be your minimum installed height. IMO if you have 280 seat and at least 800 open, you should be good to go. You should be running no less than a 7/16 x .165 pushrod. Straight wall on the ex, single taper on the intake. Minimum between the rocker...would like to see .06" but I think once you get this all sorted out you'll have plenty.
Don't take this the wrong way but running the wrong spring just because they're new isn't a very good reason. ;)
Thanks again for all the advice. It is greatly appreciated.
I don’t actually have a lot of faith in comp springs, although I previously ran a set of these 948s in my old 565 without any issues.
I was thinking I needed this stiff of a spring due to running stainless valves?
I don’t have a problem changing the springs out, and would much prefer to run the right spring, and from what I read, PAC and PSI makes better springs?
I’m certain I can get .06” clearance just by changing the locks to standard height, but now I’m thinking I need to change the springs and installed height to optimize coil bind as well?
Thanks for the advice on pushrods. Believe or not, my previous setup was running these springs with .080” wall 3/8 diameter pushrods. I was planning to run 7/16 .165“ wall tapered P/Rs on the exhaust and at least a .135” 3/8” dia on the intake. But it looks like I need less spring and more pushrod?
Thanks again for the advice.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #22 ·
As most have said your over springed with a big dia. triple, a smaller dia double with the correct spring rates are possible but you already have your springs.
The spring info all manufacturers list are a starting point and a way to verify there spring rates ,coil bind, etc. IMO start with the coil bind 1.130 add your lift .836 and then .050-.060 for spring gap which comes up with your installed height which is how most quality spring manufacturers suggest to do. Set up at those gaps at full spring compressoin the gap would be in the middle of the spring and the ends will slightly be touching. Better spring control , when your running big gaps in the spring it could lose control of the valve easier causing spring surge/bouncing.
I dont know your cam supplier but they should have given you a spring rate or required spring pressure to control the specifics and their lobe design.
Is this a stainless valve or titanium?
You will likely need the other keepers as well as Scott has stated if using these spring which should be done before any height measurements to set up springs.
Thanks. I had no idea I had too much spring. These are the springs that came on the heads when I got the motor from SRE in ‘08. I had bought these as a replacement set. The cam in that 565 motor was slightly smaller than the one in my new 582, so up until now I was actually thinking it might not be enough spring.
Both cams are custom SFO cams ground for SRE. I have both cam cards, and there’s no mention of recommended spring on either card.
The longer valves that Brodix installs in the 3XTR - O heads is what calls for a 2.10” installed height.The +.050 “ locks obviously add to that.
I’m running stainless 2.35 intake and 1.88 exhaust valves.
I was looking at the PSI DR425R dual coil spring which is 1.625” dia, 622# rate and has a seat pressure of 305# @ 2.05” installed height. Coil.bind on that spring is at 1.1”
So taking your approach of coil bind plus cam lift plus .060 clearance:
Intake valve: 1.1 + .836 + .060 = 1.996”.
Exhaust valve: 1.1 + .816 + .060 = 1.976“
So, by that method, a 2.00” installed height should be close to what I want, IF that spring is the suitable for my cam specs.
Do I have the calculus right?
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #24 ·
I have run the DR425R springs at 2.030" and 1.985" with .800" net lift on 2 engines and no issues. 150-160 grams intake weight. Get the optional polished ones if you want a little more potential life. Still a big diameter spring at 1.625"
Thanks. That’s very helpful. I know it’s still a bigger diameter spring, but I think I’ll be okay on clearance once the retainer moves down and away from the rocker.
Actually, I think that just changing the locks with these springs and retainers would get me the clearance I need, and that would put my installed height closer to where it needs to be.
So I’m thinking for now I’ll get a spring pressure tester and take Scott’s advice and pull the inner spring out, check coil bind and then calculate installed height from that and then see what seat pressure I have at that installed height and then decide whether I need to change out the springs and retainers now or not.
I’ll report back on here what I find out.

Thanks again to everyone for your advice, which is greatly appreciated.
 
  • Like
Reactions: scott foxwell

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #27 ·
I've done several engines with big stainless valves and the pressures I quoted above, running in the mid to upper 7K range with no issues. Your 2.35 intake won't be a problem at that rpm. PAC and PSI are about the only springs I use these days. Comp gets their springs from several different suppliers. I wouldn't think their big triple is a bad spring so If you can get what you need out of it, I'd run it for now. If and when they give up the ghost, cross that bridge then. I would get an on-the-head spring checker so you can keep track of your pressures. Get a baseline when they're new and monitor any changes.
Pushrods are way important and way overlooked. The bigger the better. It's common where more spring pressure is added to try and control a problem caused by too-small of a pushrod so yes, bigger pushrods can lead to less spring pressure. You don't want the pushrod to be a secondary spring in the system.
Thanks very much for this, all of which makes total sense to me.
I think I’m going to run the springs I have now, with the inner spring removed, if that doesn’t drop the seat pressure below 280# at the correct installed height, per my previous post.
I’ll order an on-head spring pressure tester as well.
Thanks again for taking the time.
 
  • Like
Reactions: scott foxwell

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #31 ·
If you have inner spring locators that center up on the guides instead of outer spring cups that center up in the recess of the head castings, you might want to consider that. Removing inner springs could cause springs to move around?
Thanks. That’s a good point. But I do have spring cups that have an outer lip.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #32 ·
Yes looks like your math is correct IF you change springs. If using the ones you have know already adj that formula to set correct spring height AFTER you drop the retainer height with differnt locks. Also you may want to get some finer shims to get your spring height correct preferably .050-.060 ranges , the spec you posted was good on the intake but leave your exhaust about .084in if both were set at 2.00.
Soooo get the spec height close as possible to needed because the extra adds to your .050-.060 in a +/- way.
Okay. Thanks. So, you’re saying I should shim the exhaust spring a bit more to keep the spring gap at max lift as close to .050-.060” as possible, correct?
I’m planning to order some more shims as well, so that I can get the installed height correct.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #33 ·
"In the past, greater clearance was highly recommended, but current performance engine builders prefer a tighter clearance to coil bind as this helps dampen spring oscillation at high rpm which improves spring life and valve control. But this demands attention to detail."

How to Set Up a Cylinder Head (dartheads.com)

This was just a quick search on coil bind.

Have you asked the cam grinder what they recommend for a spring at your lift and RPM? Weights of components affect it also.
Thanks for the link. I’m going to watch that. I’ll also send SRE an email and ask them what they think I should use for springs. After all, much has changed since they built my original motor back in ‘08.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #38 · (Edited)
That is a very informative video. BTR is an awesome company and Tooley is a very knowledgeable, stand up guy. Years ago I bought an LS3 cam kit from another vendor and that kit came with what I suspected was a BTR spring kit, with no literature except a cam card, and what appeared to be the wrong Ti retainers.
So after trying to contact the vendor, I called BTR and Brian himself answered the phone and he took the time to listen to me, then asked me to email him some pictures, which I did, and he then emailed me back to confirm that they were his springs, which the vendor bought in bulk and relabeled. He also confirmed that I had the right retainer. At that point I had not spent a dollar with BTR, but since then I’ve ordered a couple of cams from him and a bunch of other stuff. Anything I need for LS parts I buy from them, and they have been nothing but awesome people to deal with.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #41 ·
Anywhere between .05 and >.100 off c/b is going to be fine. Your actual coil bind within that set is going to vary anywhere from .010-.020 so fighting for .010-.020" of c/b is really a waste of time. Just keep it under .100 and anything under .05 you're going to want to measure every spring. That's not necessary.
Thanks, I will follow your advice on that. I’m thinking I’ll shoot for 2.02 on the intake and 2.015 on the exhaust, or as close as I can get to that.
I’ve ordered the new retainers and some extra shims, although I have a bunch already. I’ve also ordered a spring rate measuring tool, so that I can see what the difference is without the inner spring.
I’m hoping to have that stuff by Wednesday and then I can start setting it up to see if these springs can work or if I need some other springs.
I also pulled all the springs off one head today and I put one in the vise and measured coil bind and it was right at 1.09” so you’re right about C/B not being as stated by comp (1.13”).
 
  • Like
Reactions: scott foxwell

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #43 ·
Did you check the coil bind in the vise with a retainer installed?
Some spring companies show a c/b with a safety margin factored in. That's why I always measure.
No sir, I took the retainer off and put the spring by itself in the vise and clamped it until there wasn’t any space left between the coils.
 

· Registered
2000 Camaro SS, BBC, TH-400
Joined
·
201 Posts
Discussion Starter · #45 ·
Kinda thought so, You have to use the retainer. That inner step compresses the inner spring another .100".
Ah, that makes sense. I’ll try it that way tomorrow. Thanks.
 
  • Like
Reactions: scott foxwell
1 - 20 of 38 Posts
Top