Unreal

Springs are very application specific. There is NO way a single spring would work for me or my setup. The problem is people think dual vs single is an argument at all. It isn't. That is like saying a truck vs a sports car. Well, for what? To tow or to road race? Both different purposes for different applications.

Duals can be junk, unstable, and unreliable, or the opposite. Same with singles. A single may not control a valve at 9k RPM. All the high HP high RPM >8k+ motors I've seen run a good dual. Not a $220 cheap dual, but $500-800 a set PAC setups, or similar. There is a huge difference between some random "gold or platnium" china made spring and a high end PAC spring, and even the PAC springs have a HUGE range. So whenever I see someone saying single controls better than dual, or anything like that, it is silly because that is such a broad statement is useless.

Someone can just as easily pick the weakest lightest application single PSI spring, vs a properly spec'd PSI dual, show how horrible the PSI single is and go around preaching how bad singles are for valve control, because it was the wrong spring for the job. Just looking at PSIs catalog, they have 5 1500 single springs, and then a TON of dual springs, and the other series don't even offer single, but dual offer triples. It is all about the correct spring for the correct job. For my setup I needed a solid 450-460lb spring because of the boost and cam profile I got, so I got the appropriate dual spring for that application. A "popular .660" spring would float like crazy. Plus anyone rating springs by max lift is so far off the mark. That is just something to use to market to people who don't know better.

Les-10

Point taken & makes plenty sense. Unable to get in contact with Cam Motion today but will be 1st thing Monday.

Thanks

Dan_the_C5_Man

Springs don't care about human opinions. The fact is there are a lot of old-school engine builders that, by default, still recommend dual springs, when a modern single beehive spring would be just as well suited (or better) for the task.

Look at the track record Katech has with the PSI single springs - the cams they spec with that spring are more agressive than the one the OP is looking at.

Clearly you shouldn't discount a manufactures recommendation, but you don't need to shut off the logic center in your brain and blindly follow it either.

How many people here run non-Mobil 1 oil in their cars? It's the same thing, there can be more than one right answer.

Michael_D

With Mamo heads, that cam will satisfy your goals. I would want a greater duration split with the oem exh port.

MTPZ06

Dan pretty much summed up my thought process...

big_mike_eu

Awesome!! Aside from the P&P heads and exhaust valves (+ springs) everything else is stock. I wasn't sure how much the stock intake and exhaust systems will restrict power.

I'm glad to hear that I am not alone on this journey haha I am also looking at the stage 3 cam. I sent Cam Motion an email this morning with few more questions, probably won't hear back until Monday

Thanks Mordeth I'm glad to hear I'm headed down the right track. In your opinion how do you think the stage 3 would differ from the speced stage 2 cam (http://www.cammotion.com/camshafts/l...246-117-5-3-5/)

Everyone else feel free to pitch in on this

Thanks Michael Unfortunately for now I will have to keep the stock heads which only received the WCCH stage 2 with port and polish without mill. I'm still getting familiar with the LS platform so this might be a dumb question, how would greater duration split affect overall behavior?


One of the questions for Cam Motion is why they decided to offer the dual spring vs other alternatives. I was just curious as to the thought behind it. I know its a hot topic and would love to share the response with everyone here hopefully on Monday. All you guys are way more knowledgeable on these engines than me so I want to be mindful and share any findings and useful info I come across along the way to help the community.

Something that was brought to my attention, slightly off the main topic, aftermarket cams seem to have higher lift on the exhaust what is the reasoning behind that? Just curious to learn more about the LS

Unreal

Call Cam Motion and ask them. If you trust them enough to design a cam, design cam lobes, and spec you a cam, you should trust them enough to provide good guidance on what springs/parts work with their cam. If something doesn't work, it has stablity issues, etc then it is on him. If you start piecing together parts, and not following his advice, then it is all on you. Just like if you want to run a Katech cam, run their proven tested setup.

My point was dual springs, single springs, etc etc doesn't matter without getting into the details. His dual springs could be crap or the best thing around, but people saying run a single because singles are more stable are basing that off testing of a completely different combo, with a different cam and parts. Odds are the singles would work great for this setup, but I wouldn't go against his advice. If you don't like it or don't trust it, then abandon that path and just go with a test tried proven setup like the Torquer 110 with the PSI springs/etc.

big_mike_eu

Totally, I trust them. What you are saying makes perfect sense. If they designed the set up, they should stand behind their product. I asked about the springs more from an educational stand point. Likely I will end up going with their recommendation. The only question I have in my mind is if I should step up to their stage 3 cam, given that their recommendation already seems to be a solid choice. I will be in touch with them on Monday for sure

Michael_D

LS7 intake port is amazing. Exh, not so much. The added duration on the exh side is needed to augment the intake. Good rule of thumb is at least 20 deg more exh duration with an untouched exh port. WCCH; you can get away with less, but I'd still want 15 deg more, at least. Mamo does crazy magic with his port work, hense a much lower split needed. I do not believe anyone can match what he does with those TF castings.

You will want headers with any of your options when running over 220 intake duration.

Standard springs have a natural resonence that can create instability. A beehive does not, nor conical. This is not a big issue, unless the engine will routinely cycle through this. It's usually at a paricular RPM. For drag race, not an issue, as the engine is typically WOT and shoots through the resonance range quickly. With a street car, or road race, the RPM will pass through the resonence range all the time. That's why the beehive is more desirable, if the build will allow them. There is generally a reason for spring failure. They just don't fail without reason (unless the quality is low). I would always prefer a beehive over a dual, if the buid will allow it. PSI or PAC are both good choices. Don't go cheap with springs and retainers.

Apocolipse

Lower lift exhaust opens and closes the valve slower.

big_mike_eu

Thanks Michael, this is very educational for me. I will consider your advise on the headers. Makes total sense considering the LS7 intake vs exhaust port flows you just explained. If I am to stay with stock headers temporarily (this project was not really planned) am I looking at any other drawbacks aside from hp?

Thanks Apocolipse! Makes total sense. I guess applying the same logic as with piston speed/stroke/rpm. Less distance to travel in same time period due to lower lift

Apocolipse

That is corrrect. It has also been hypothasized that exhaust lift is less important than intake lift when it comes to making power due to the pressure in the combustion chamber reducing as the valve is opening more.

I did 0.649" intake 0.630" exhaust on my custom spec cam for that reason. Circle track racers have used a lower ratio rocker on the exhaust side for this reason (lower acceleration and lift) which has proven to be very beneficial.

phipp85

I did. I retarded it 4 degrees using a different crank gear that had multiple keyways cut into it. I already had it otherwise I would have just bought a entire new adjustable timing set.

Michael_D

You may experience more of the typical, undesirable effects of reversion if you have too much cam and an exhaust system that can't evacuate the exh port. Just keep in mind that the header primary should pull on the port and it needs velocity to do that. If it's undersized it'll choke, oversized and it'll slow the pulse too much... yin/yang thing....

Exh valve lift should never be more than what's needed. You need enough to evacuate the cylinder, but if you go too far, exh port velocity will be reduced during the valve overlap stage and will lose some pulling action on the intake port. Too much exh lift will also exacerbate reversion (as well as wrong seat/valve angle)....

BigVette427

My bad, I didn't take the time to articulate the points that I was intending to convey, well enough. I really only meant to infer valve springs for the levels of cam that Mike is considering, which is around the same level of the popular 116 cams pioneered by Katech. AHP offers a similar 116 cam and will set it up for the BTR duals or PSI 1511's, either way.

I'd also suggest that you defer to your cylinder head guy for their opinion and suggestion on valve springs for your setup. I think the real reason why Cam Motion suggested the .660 duals was not so much because the cam specs necessitated a dual valve spring, but more so in part because with the valve springs they offer (I want to say their valve springs are made by PAC?), their comparable 1.290" beehive is like a 1200 seires PAC comparable spring, and they do not have a 1500 series beehive to offer along the lines of the PSI 1511's. PAC is part of Peterson Spring and as best as I can tell, PSI was just founded by former Peterson Spring executives. I know there is lineage on that family tree, just not certain what the extent of the relationship is.



Interesting yes, but the GM LS7 cam uses both .591" for both intake and exhaust lift. Which is all the more so interesting given the disparity in the size of the intake/exhaust valves, as well as the disparity of the CFM flows in the cylinder head between the intake and exhaust side.

I believe this is much along the lines in how AHP describes the intent of their "high-velocity street porting" option on their LS7 heads. Would be interested in seeing the exhaust side CFM's flows on that, if anybody has those.

I think a cam along the specs of the Katech Torquer 116 approaches the threshold on how far you can go on the GM LS7 exhaust manifolds. I love the way my motor with a comparable 116 cam runs in my 2012 with GM LS7 exhaust manifolds, and CA required 4 cats. I'm sure headers would wake it up even more but I wanted to maintain OE appearance. I'll likely go with the Corsa x-pipe (14331) with the 3rd and 4th cats omitted, but that will have to be for another day.

Unreal

I completely agree use a single if possible, but my point was using one spintron test, of a different setup, with a different cam, with unnamed, who knows how setup duals, and concluding duals=bad, singles=good is becoming far to common here. If the cam vendor is saying to use his duals, spec'd for his cam, I would go with what he says, but ask him if the 1511/1516s are an option. If he says yes, do them, they are great springs. If he says he rather you use his duals, do that. I don't know if I would call that his opinion anymore than someone saying using singles is there opinion, as no one has tested the singles on this cam, except maybe Kip.

big_mike_eu

Thanks for all the good info guys. It's been really hectic the past couple of days. I haven't had a chance to speak with Cam Motion yet. Hopefully I will get some time later this afternoon to give them a ring. I'll let you guys know how what they said

Undy

Mike, you remember the "eductor effect" when you pumped them bilges, don't you?

Michael_D

big_mike_eu

Hi guys, just wanted to share an update. Cam Motion got back to me yesterday. In summary, I will be moving forward with the cam they recommended for me. I plan on placing the order this afternoon.

Regarding the springs (as promised I would share their response), they said the double spring set up they recommended adds the extra security in case one of the two breaks. If one was to choose a beehive spring instead, the PSI 1515ML would be a suitable replacement.

I will try to reach out to AHP today regarding the Ferrera valves. Do you guys know if they have a representative here on the forums?