JimMueller

iTrader: (9)

When tuning on the street it really feels like the power is falling off huge between 6000 and 7000 RPM. I requested Patrick G spec the cam based upon shifting at 7200RPM. No dyno yet.

- Block decked .020
- PRC 5.3L heads requested to be milled to 59cc, found they were 62cc (even though it appears they already took .020 off based upon the bolt boss thickness) and milled another .020 off to reach 59cc
- Cometic .040 gaskets
- stock rockers shimmed .020 (I think?) for wipe pattern
- Cadillac Racing lifters
- Cam is a 22x/23x .6xx/.6xx, 110+2, LSK lobes, degreed in using ICL method
- I'm not sure what else is part of the equation

7.400 pushrods, 3/8"x.080 wall, were chosen based upon how it felt as well as using a Crane pushrod length checker. I'm just wondering if somehow we got the measurements wrong and that would account for the fall off up top. I have a Comp Cams pushrod checker at my disposal, but I'm not sure what preload to use for the Caddy lifters. Any guesses what range I should be in and/or a good pushrod length checking tutorial?

JPH

iTrader: (2)

i would say shifting at 6700-6800k tops with that cam, and power falling off by 6400k. these motors want preload, you need between .080-.100 working the best for you. if you don't have enough preload, rpm would be affected. i used a 228/232 on a 112 one time, and it fell of at 6000k. patricks profile should rpm a little higher, depending on what valve springs you are using.

JimMueller

iTrader: (9)

Valvesprings are PRC Platinum duals.

JPH

iTrader: (2)

u got good valve springs, work on your geometry/preload. you need to be more specfic when you say 6000-7000k. try to pin point it, to a certain rpm, that will help.

JimMueller

iTrader: (9)

Is there something else I can log which will show the relative amount it's falling over, like Delivered Torque?

Tony Mamo @ AFR

iTrader: (13)

I would think the chassis dyno would be the best tool here. Im sure you could gain access to one and for less than $100 get a few pulls on it to see what exactly is going on. Trying to use the SOTP method is not going to work although it seems it certainly alerted you to a potential problem.

How much seat and open pressure are those springs? What is the spring rate?

LSK lobes need some stout pressures to keep the roller glued to the cam lobe...

My advise is to hit the dyno so you can post the gragh....lets see whats really going on

Tony

LS1curious

7200 rpm with that ICL. Hmm not really happening.

Tony Mamo @ AFR

iTrader: (13)

Good call....

Neither the duration, the LSA, or the ICL is condusive to that RPM....

Mid 230's on the intake lobe and at least a 113 ICL (or even 114) with little or no advance would have been better suited for that job. Or a 112 with even more duration might have done it. Also, airflow is at a premium here (as is valvetrain weight and stability) and the entire package from the CAI to the exhaust tips would need to be optimized to allow the engine to hang on like that with a hyd. roller.

That small a cam on a 110 probably peaks in the low 6000's and is falling off a cliff by 6800

Once again however....why bother guessing when a dyno gragh is worth 1000 words as they say.

Tony

LS1curious

Having dynoed this camshaft before I have no problem saying its out steam at 6300. In fact most of the stuff out there is. I have found some ways to get the ls6 intakes to go to 7k but I ain't giving that info out.

RE AND CHERYL

iTrader: (31)

Throw it on a dyno, but based on the cam your running I would expect it to be loosing power way before 7k. I'd probably shift at 6500 at the latest.

Re'

JimMueller

iTrader: (9)

I'll see if I can get a couple of pulls at one of the local dyno's sometime soon. Seat/open pressure is supposed to be 155/410 on the PRC duals. I don't think I've seen the 'spring rate' term used with valvesprings, but max lift is supposed to be .660. I have a Ray Mac Racing LS1 rev-kit (http://centralfloridastreetcars.com/...revkitside.JPG) instead of the plastic lifter trays.

Regarding the cam design, I don't know what to say. Pat has a good reputation and I told him I wanted to shift at 7200 to take advantage of mechanical gearing, but I also wanted to lower my torque curve for autox/RR. The cam doctor specs are here: https://ls1tech.com/forums/showpost....59&postcount=6

Tony Mamo @ AFR

iTrader: (13)

Pat is a bright guy (and a good friend). Looks to me like he designed it more towards the autoX application which in fact it would be spot on for.

The larger issue here is your request was unrealistic....in a sense almost at the opposite end of the spectrum. One is aimed at high RPM power and the other is concerned with low RPM TQ to help explode a car out of a slow corner. Kind of like asking for a cam that will turn 7200 and idle like a stocker. The reality is a combination like that doesn't exist....not until our beloved LS1's have V-Tec.....LOL

Regards,
Tony

JimMueller

iTrader: (9)

It didn't need to make great power above 6K, but I am hoping it doesn't fall off horribly. I'm heading to the dyno today and have another scheduled next week if I need to change pushrods.

I think I have the math right, but obviously it still needs to be checked. I'm not clear if the base circle is different between intake & exhaust on a LSK cam. Maybe those threads which indicated the exhaust was different had different lobes.

StockPR+RockerShim-(StockGasketCompressed-NewGasketThickness)-HeadMill-BlockMill+Preload+((StockBaseCircle-BaseCircle)/2)

I come up with 7.4 before compensating for the base circle. The change in the base circle radius is .0785, so from a math perspective I come up with a 7.4785" pushrod, which I would round down to 7.475. If that is the case, what symptoms may I notice from a pushrod that is .075 too short?

JimMueller

iTrader: (9)

OK, here's 3 pulls from today at Norris Motorsports. We didn't feel it fall over at all on the dyno These are by no means completely tuned, just a baseline and some quick adjustments.

Pull 1: Baseline. Low timing but logging wrong PID to determine where to adjust. AFR was set ~12.5 below torque peak and about 13 above. VE isn't quite polished yet to yield what I command. 3-4* of constant KR at WOT.

Pull 2: Set commanded AFR to 13 across the board and this time we could see what was going on with the spark. 19-25* from 2400->4400. 3-4* of constant KR at WOT.

Pull 3: Put in some mid-to-upper 20's advance values to get in the ballpark. Temporarily altered max KR table.

Pull 1

Pull 2

Pull 3

Thoughts.... I like the curves, but I'm hoping theres more in it with just tuning. I'll run a tank of 104 to confirm the KR is false. Assuming it is I'll have to decide how I want to deal with it.

Rays C5

I'd like an answer to this also.I would think the dreaded "sewing machine sound which is what I'd like to get rid of.

JimMueller

iTrader: (9)

The top-end is a little rough with smoothing=0, but not jagged like I'd expect with a valvetrain issue. So I'm wondering if the math above is wrong, or what other factors would cause a 7.4" pushrod to work correctly if the math says it needs another .075. Can there be that much tolerance?

-Joseph-

iTrader: (12)

It would be easier, quicker and most important: more accurate to just use a pushrod length checker. I've never been a fan of calculating pushrod length by measurements (that the setup is "supposed" to be). You're also missing a few calculations such as valve depth and possible slight valve tip length differences from a stock head. I've also seen lifter total length differences between Comp lifters and OEM lifters as an example that needed different pushrods just by a lifter swap.

JimMueller

iTrader: (9)

I got a late start on it today and will try again tomorrow since I have to replace a knock sensor also. My measurement today was 8.5 turns, so 8.5*0.050=0.425+6.800=7.225+.060=7.285.

Any tricks to keeping the bottom section of the checker from turning?

LivingCanvas

iTrader: (4)

-Joseph-

iTrader: (12)

That sounds way too short, are sure the lifter is on the basecircle of the cam? What I do is turn the motor over by hand (clockwise) until the intake rocker is closing, then bring that piston to TDC and that cylinder will have both lifters on the basecircle of the cam. That where you need to check lifter length and preload. I've had to pull the rocker off to make that adj. on those pushrods, isn't there measurement lines on it that indicate how many turns?