Well, in the process of looking over the car this week and getting ready for the race today, I pulled a valve cover and found yet another broken spring, and while I haven't looked real hard yet, it appears that I might have a slightly tweaked valve....I swear, this thing has been a valve spring eating machine....I couldn't get it to keep the rocker adjustments set or for that matter keep the lock nuts tight, found that was a spring issue so changed springs and has been great up until now. No warning, nothing. Fortunately I honestly think it happened while I was moving it around in the shop, since I checked it after the last time I had the car out and it was good.
So what I'm going to do at this point is call it a season for now. Starting to get warm here anyway and had already planned for my cylinder head guy to get it and work on the heads anyway. We had also planned to change cams, as the one I've got makes great power, but it is a pretty intense part, and we decided it's too aggressive on the lobes, which is leading to my issues with springs. He's already got a different cam in mind, which should be somewhat easier on the valve train than this one is, and he feels the profile will make better power overall anyway. We're gonna tweak it a bit as well, since I made the switch to methanol, so it's more alky friendly. Head work will include more work on the ports, bigger intakes and smaller exhausts, chamber work (including softening a bit more), and a few other things.....I get parts at cost and only thing I pay for is parts, all labor is free....even the dyno will be free I just need to supply the fuel....
So for now I'm on hold for racing, but should have a better piece when done, and a new dyno sheet to work from for the converter and such....
This drives me crazy but at least we're going to address some of the issues I've been having, namely valve train stuff.....
Just curious. How aggressive? It over 900?
I don't remember the lobes, but they are very aggressive. Yes over .900. .986 intake, .936 ex if I remember correctly.
640 or 670 spring? Those Pacs?What do you figure about an 890 or so? Ya it will give you time to regroup. Well at least nothing went to the first floor.
Thats what I love about my Bullet 55mm blower cam, .810 ex and .800 int. Springs, lifters and rockers live forever. 380 on the seat for pressure
Ya i have a good friend of mine. Ya his is in about the same situation as yours. 820 CI and eats springs like there is no tomorrow. Titanium rod motor. Constantly hammering out bearings too.
LOL Was offered for what he called "The White Elephant" for 15K complete less the splits. hurry up and I'll load the ** for you. No thanks....
Thats a lot of lift. How big is your motor? What kind of times do you run with it?
Well, I couldn't just let this go. So I went out to the shop and decided to leak it on that cylinder and pull the spring to see what's up. Good news is it leaks the same as it did before, no change. The flakes I saw were from the spring only, zero damage to the retainer or seat. Looked at the others while I was there and we're good. So installed a spare and we'll see how it goes. I'll start it up tomorrow and see how it sounds.....
Original springs were PAC 1248's. 332 @ 2.1, I've got them just short of 400 for my cam. 950 open. Running PSI now because the rockers kept coming loose. Running PSI 1248's, bit different seat and open pressures, different frequency. Haven't had to touch the adjustment since I installed them. This was the first issue since the swap. Cam is a 55mm custom Comp Cam.
38 Fiat, engine is a 665" 12* engine.
So I'm feeling a little better now, and will reconsider taking it out again, although it's not going to be many more times as I'm still pulling the engine and taking it to Charlotte. Lash didn't even change. I do think it broke while moving it around the shop because that's all the damage I can find. Looked in the cylinder with my scope as well, no witness marks on the piston from valve hitting....I guess I dodged a bullet here, had that happened at 7500+ it would have gotten ugly quick........
FWIW, my cam is .830ish lift, 12* heads, Ti valves, my 1.500 PAC springs (325# seat 975# open) last 100+ passes, 82-8400 RPM shift. I do have some very stout Manton pushrods, 1/2" int, 9/16" exh. Never broke a spring.
The Blower Shop XR1
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2017 Bradenton Heads Up Madness
Open Outlaw Champ
2018 PDRA T/D #5
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2020 Retired From T/D Competition....
2020 Bradenton NMCA Hemi Shootout Winner
2021 getting back into bracket racing with a Gen3 Hemi powered 87 Cutlass.
Proper warm up is critical to valve spring life.
Bob Kamp: "NEVER turn the engine over 2500 rpm until you have at least 140 degrees water temp, for a roller spring."
"Despite the high cost of living, it remains popular."
If you are using the 1248's installed at 2.100 you have coil bind going on! Assuming you have .986 lift.. It's the wrong spring, you need the 1249's which install at 2.200
2.100 at max 900
2.200 at max 1.000
PAC/PSI same spring different box
No, they are not. The PSI is slightly different diameters on the springs, also different frequency...spoke long and hard with them before making the change. They are definitely not the same spring.....
I might have been mistaken on the part numbers, I remembered with the last combo I had I was running the 1248's.....I'll have to look on the box if I can find it for these....I'm 10000000% certain I'm not at coil bind, closest I have is at .070", measured......
Lift is not the killer (unless coil bind). The ramp profile is what works the spring so hard.
I am almost afraid to bring up my experience as people will call BS. I worked closely with a cam grinder and we were running .985 lift w 1.85 rockers on intake and put over 300 runs on the springs. PAC 1249s @ 2.200 setup. I run a pretty aggressive rocker, but it minimizes the aggressive ramps getting the valves open, so the springs live longer.
Jeff Taylor is my engine builder. He is a ring sealing FREAK. We just went into the engine for freshening after 5 years. Used Power adder pistons (thicker skirts, less piston rocking due to collapse), and GRP Pro Mod style rods. Probably could have gotten away w .005 overbore, but decided to go clean with .010.
I know my cam is part of the issue. When Joel helped spec it, he decided to go with a somewhat aggressive lobe in an effort to help breathing....it's been hell on my valve train since. When I take it to him this summer, along with the work on the heads we're going to put a different cam in it. Still plan to run a ton of lift, but changing lobe profiles to help settle things down some....That should help a lot
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