4thGenCamaroZ28

I have an LQ9 with 243 heads and a Summit 8707 cam, I used their Sum-174004 Springs which have a seat pressure of 130 lbs and open pressure of 320 lbs. The cam description says it pulls strongly to 7000 rpm with as little as 150 lbs spring pressure. It doesn't seem to, it seems to drop off around 6400 and the manifold vacuum goes to 95 kPa.
I'm a little suspicious because their dual spring kits say in the description that it will pull strongly PAST 7500 rpm.

And to confirm I have a LFA, which is basically a fourth gen LQ9 with an aluminum block and 243 heads. It has a Summit 8706 cam with their SME-174003 dual springs and it pulls to 7500 rpm no problem, These two engines are built nearly identical. Same intake manifold, same air intake, same headers, same injectors, etc. The dual springs have 140 seat pressure and 380 open pressure.

Focusing on valve springs only, could the problem be the 174004 springs?

Che70velle

iTrader: (6)

I get that we are talking springs here, but intake and TB choice will dramatically affect operating rpm limits. What intake and TB are you using here?

4thGenCamaroZ28

TBSS, 92mm tb.

Two engines same build specs except the cam and springs. The 8706 is the turbo version of the 8707. 8707 with smaller springs won't rev.

Che70velle

iTrader: (6)

Are the tunes exactly the same?

4thGenCamaroZ28

Close but no.

MuhThugga

I think you answered your own question. The springs have 130lbs of seat pressure and the cam requires 150lbs of seat pressure. Chances are that it requires more open pressure than what the beehive is providing, too.

Abs

did you get this figured out?

Also, how do the cams compare, and which do you prefer? I am thinking about using one in my 04 ls1 gto. M6, stock 3.42 gears.

4thGenCamaroZ28

I know this is late.
Did I get this figured out?
Well as you can see here people can't comprehend a post. I said I built two engines nearly identical yet I still get questions about are they both the same. This is based on the other post where I asked the same question and it went way off topic. I deleted that one and this was a second attempt.
I called Summits tech support to ask why they say that one springs description says it will rev past 7500 rpm. Their response? What bottom end am I running because you don't want to run a stock bottom end at those rpm's.

Doesn't really answer the question about valve springs does it?


I called back and spoke to another person. Have you spoken to anyone at Summit recently?

Jake Wade

Alrighty then. You feel better now after that rant?

The Summit reviews have to go through a second party DEI group for approval.

Abs

Diversity, Equity, and Inclusion, eh?

gametech

iTrader: (1)

Since the OP decided to beat this dead horse some more, I think it deserves pointing out that MuhThugga gave a clear. concise answer to the original question. I have no idea why someone would need to solicit advice from internet forums and customer support to understand why a spring that is 20lbs under minimum spec is not letting the cam rev to what it is advertised.

4thGenCamaroZ28

Well, because it came in a kit that consisted of the cam and springs. I know, I'm so stupid for running a cam kit with springs that are 20lbs under minimum spec for the cam they come with.
https://www.summitracing.com/parts/s...tcombocontents
See, read the "camshaft manufacturers description" The kit above say it pulls TO 7000 rpm

This kit https://www.summitracing.com/parts/sum-8707-1ds says it pulls PAST 7000 rpm.

gametech

iTrader: (1)

The first link in your last post does indeed explain why you have a gripe with Summit. Surprised to see a "kit" put together with mismatched components. It also leaves out the spec about needing 150lbs of seat pressure in that description. The original links you put in the previous posts give the specs that show the mismatch, so I had no idea why you put those parts together. This makes more sense now.

Abs

I've actually seen people ask @Summitracing about this on various platforms. I don't think I've seen a good answer though.

@Summitracing does the 8707 cam require 150lbs of seat pressure to rev out to 7k rpms? If one of your spring kits with the .600 lift springs with 130lbs of pressure were used, what should be the expected result?

4thGenCamaroZ28

I already tried. Like I said they want to talk about your rotating assembly and fuel system being able to rev out. about the valve springs or why the description says what it says. And it's said that for 4 years at least.

In early 2020 I talked several times to the guy who was the engineer for the pro LS line of cams. One of these was a conference call with a guy I think named Mike from Trick Flow. Apparently the double springs are made by Trick Flow, he said they will rev past 8500, said I'll never float valves with those. I'm only saying this because I'm not the type of person to just jump to one conclusion and go off on their tech support. And I don't feel comfortable calling this guy now because the reason I talked to him is because he emailed me and offered his number for the problem I had back then.
Yea, I know this is the internet and this will be questioned. I don't have the phone transcripts so you either believe me or don't post on here questioning me about it. @Summitracing WILL NOT either reply, or provide any useful information. I will put money on that.

Threadzy

I just ordered the same cam kit. 8707 with the recommended springs. Wondering now if I should return the single springs and get the double? @Summitracing

grinder11

iTrader: (1)

At the risk of sounding like Mr. Obvious, Summit certainly needs to change the nomenclature if they've been misrepresenting this kit, and for years, as good to 7,000+ rpm. The open pressure may (or may not) be OK, but the seat pressure, per their own specs, is not. Muh Thugga gave good info, and Che70velle brought up some good points. IMHO, people tend to focus more on max lift pressure than seat pressure. Seat pressure is just as important, maybe even more so. You could probably, hypothetically, design a spring that would have 100lbs of seat pressure, but have 500lbs of open pressure. It would still suck. I understand your frustration, trust me. I have a total cluster going myself. There are some smart people on here, in this very thread, that can help you. But insulting them will get you nowhere. I wish you well. If I were you, I'd be calling someone at Summit, perhaps a department manager, and point out the discrepancy in specs you have discovered. If you do get thru to someone who can actually help, if you must vent, do it constructively. If you accuse them of being too stupid to "comprehend" you, a hangup is sure to follow. Best of luck to you, my friend.

Summitracing

Hey folks,

We've reached out to our internal team that developed these cams for clarification. As soon as we have an update we'll be sure to let you know.

grinder11

iTrader: (1)

IDK if you ever got this sorted, but if not I'll soon have a brand new set of PAC duals for sale, NIB, never run. If they'd work for you, I'll give you a Helluva deal on them. LMK....

4thGenCamaroZ28

I think when (not if) @Summitracing internal team finds that they sold me a cam kit with the wrong springs I should be getting the right ones for free. I mean this thread that I started seems to have put this in motion.