I was doing a oil change and always cut open my filter and this time the oil seemed darker than usual and was seeing more silver metallic flecks than usual. I always get some from my titanium retainers. So I decided to pull one of my valve covers and a immediately saw a chuck on metal on a magnet I installed on the bolt heads at the oil return holes in the head. Upon closer observation I found the intake outer spring on my #6 cylinder was broken in 2 places! The spring still is managing to keep the valve closed and lash is still amazingly spot on where I tested it. All parameters were check when I set them up including coil bind. The car ran fine with no indication anything happened. Matter of fact it actually was running better than usual. The car gets babied around town but has seen dyno time. There is only about 1700 miles on this engine and about 400 miles on this last oil change. I suffer a fairly nasty backfire about a year ago when my adjustable distributor rotor (For phasing) came lose while driving. I am at a loss as to what happened. I will check my cylinder with a bore scope but I think I got luck there as the valve appears to still be functional enough even with the broken spring. I have a screen in the valley so I should be able to recover on small pieces that may have made it by the magnets. I checked the oil pan with a bore scope and found nothing in the pan. Everything else looks fine, shaft rockers look good, lash caps are all in place including for that cylindrical. I check off seat pressures back in 8/19 and everything looked OK then. The retainers look good as well with no evidence of rocker interference. I am running the AFR 8001 PAC Racing Springs with a coil bind spec of 1.150". My installed height versus max lift difference is 1.233". The lash was set cold at INT-.0.014 and EX-0.016 per Com Cam recommendation. Seems kind of tight to me. The hot lash on the cam card is INT-0.018" and EX-0.020".

Any thoughts?

I was thinking about changing to a 1.6 ratio rocker to tack some stress off of the valve train. The power is up too high in the RPM range. I will sacrifice some top end to fatten up the bottom end some.

 

H-m-m-m-m.
How do you figure 1.6 rockers will take some of the stress off the valvetrain? If anything, changing the ratio to a higher number ADDS stress. Its been said that in some cases the 1.6 ratio destroys the valveguides. I have not seen that, but very likely.

If GM wanted 1.6 ratio in the SBC, seems like that would have been done, just like the BBC.

To me, swapping to 1.6 rockers is a cheaters way of getting more valve lift instead of installing the proper lift cam to begin with. Its like an after-thought. I bought a 480 lift but I wish I had bought 490 for example.

If you are no longer interested in a screaming engine and want more low-end grunt, just pull the timing cover, chain, sprocket and advance the cam two degrees.
It may come out to four degrees depending on your crank sprocket set-up.

 

i am running 1.7 ratio rockers.

 

Why??????????????????????????????

And how can you run over 700 lift with 11:1 pistons w/o interference?

 

Well.......there Ya go ! Be kind to those springs.

 

that is how we built the engine. I don’t know how he did it but he did. Now I am thinking dropping the ratio to 1.6 and replacing the springs. I still don’t think the spring should have broken. It was operating within specs.
A few pulls on the dyno should not have broken it. Maybe it was just a bad spring.

 

That's a LOT of lift for a street engine.......and 1700 miles is pretty damn good even with a PAC spring.
The 1.6 rocker idea is sound....but you will need to re-check geometry....this is important, in fact re-check the geometry right now to see if it was correct....
Fatigue breaks springs and that can come from cycle life or resonance......improper geometry can cause the valve train to pick up frequencies it normally would not.
I would also go to the new tool steel retainers......titanium is not the hot tip for the street......
Is this a shaft rocker setup or standard?

Jebby

 

Hey, thanks for the reply, I personally set up the rocker arms and the 3/8 push rods were custom sized and order from Tend to assure adjustment screw was at the optimum location for proper oiling when after setting up lash. The rockers are a T&D shaft mounted system that were setup using the T&D gauge for proper rocker to valve geometry which basically works out to be a 90 degree relationship between the rocker and valve a 50% lift which minimizes the rocker roller tip travel across the valve tip and maximizes valve lift.

I will probably will have to purchase new push rods if I go to 1.6 ratio rockers. Hopefully I wont have to mess with shimming the stands. That was the biggest challenge with getting the geometry correct initially.

I will contact AFR to see if they sell the steel retainers.

 

I would think its a bad spring. What does your engine builder think? The springs shouldnt break unless they arent up for that lift. Big blocks run 1.7 rockers so I wouldnt think its the ratio. If coil bind hasnt broken it then you are just having a bad spring.

 

I have parted ways with the engine builder. One of the reasons why I had to completely go through the valve train and properly set it up. I will recheck bind. AFR recommends as a rule of thumb that there be a 0.06” gap between the coils at full lift. I will double check.

 

Not necessarily so...... .737 lift on the street is a lot......even with a PAC spring (Some of the best in the industry and I had a pretty close relationship in Michigan with). It is just fatigue/cycle life......
The winner of the Hot Rod Fastest Street car deal about 10 years ago (C3 Vette with a Big Block) was running in the mid 7's for lift and had breakage issues......just a lot of miles with a lot of lift. On the street, about .680 is where the threshold is IMHO.......all of those old SB 2.2 NASCAR engines that are in street cars now are all .670/.680......
The spring is more than capable of handling the lift......but nothing out there can do it continuously mile after mile and add idling to that.
Used to be that titanium retainers were the only real game in town until Crower and Comp got wise with tool steel and profiled the hell out of them to save weight with 10x the lifespan. Less money too.....
You may get away with the 1.6 without changing the shims but you can bet the pushrod will be a bit different.....probably .025 shorter.....just have to check it.
The other thing is maybe this cam has aggressive ramps......this will wear out a spring in short order when putting around on the street.

Jebby

 

I don't know if high performance valve springs are customarily bead blasted, but bead blasting springs will put some compressive stress into their surface and reduce fatigue failure risks.

 

I am thinking after rechecking my installed height/coil bind measurements and everything looks OK, Should I just replace the spring and see how it goes? Go with another spring manufacturer? Changing ratios is going to cost some serious money. New rockers, push rods, springs retainers.....etc.

 

You will not find better springs than PAC.....
You should call them and tell them what you are doing.....they sell micronited polished springs....
Or maybe they have released something new.
Give them a buzz.

Jebby

 

Called RacingSprings.com and spoke with a very nice gentleman named Matt. Gave him my installation specs and he said everything regarding the spring install and operating RPM sounded well within the capability of the spring. He also recommended the 1300 series as you mentioned for extra peace of mind. I am going to send them the broken spring to see if they can determine the cause. He figures it may have been an imperfection or "occlusion" in the metal itself. He also said stick with the titanium retainers but check them out for wear.

 

It's easy 4 inch stroke SBC's require 15cc dished pistons in my case to get down to 11.7. I had custom wisco made for. 800 lift 2.10 1.625

 

Imo 1.150 and 1.233 is way too tight. That's why I use. 200 longer valve stems

 

I am right at the recommended installed spring height. If I were to go with longer valves or remove shims (If I had any) then I would be taller than the recommendation. Basically I have a lot of lift and as a result of this and the car sitting for long periods, I probably need to change out the springs preemptively on a schedule. I have about 6 years on them.

 

PAC is an outstanding company that I used to be in close contact with when they started in 06-07.......they want your business and they know springs. I have seen their Spintron setup and they used to send me videos of NASCAR Mopar stuff at 10,000 rpm with still frame photography......after I saw these, my whole mind set about valve springs changed. It wasn't just about the setup anymore......it was about frequencies and harmonics....you would **** if you saw some of these videos.....the spring looks liquid, distorted.....almost impossible for it to be happening, but it does. PAC was one of the first to design better cleaner wire springs that last longer without so much pressure.
In the 90's and 00's even....you had to use the stiffest springs possible as their pressure diminished dramatically after just a few runs on an .800 lift engine.......basically they picked up where Dick Maskin from Dart left off and used better manufacturing techniques to make a better spring.......this was a win-win as lifter were exploding everywhere and it was accepted in Drag Racing to break a lifter during an event. Pressures over the nose dropped dramatically and the hot street engines now last MUCH longer........
Which puts us where you are and your .737 lift deal.......it's a lot......but if you want to fix it the easiest and cheapest way.....the 1300 spring is the ticket. Simply not a better spring readily available out there. Still some $$$$ but think of how much longer they will last.....and the price of new T&D arms......
I am so glad to hear that they want to help and want you to send your spring to them.......every customer is R&D to them, and they will help especially if they learn from it.....and that is the way it should be.

Jebby

 

What is your seat pressure