Forcefed86

iTrader: (4)

Response will be down for sure, but I don't think i'll have any issues spooling the 1.32 T6 on the trans brake. On my previous 370" motor I was seeing 1.4:1 back pressure wise around 20lbs and a 6500 rpm peak. 224/224 @ 113 .610 lift cam.

The 4.8 should see quite a bit less so I think I can go semi aggressive on the cam. Not really sure how aggressive I can go on the 4.8/LS6 intake combo though.

.boB

iTrader: (1)

Pro-Comp parts are cheap off shore copies of real performance parts. I wouldn't use anything they sell. No room for that junk on my car. Never buy cheap parts, they're too expensive.

http://www.coloradospeed.com/speedmaster79-ezp-88.html

I'm an old Ford guy. But with Ford engines, anything close to .600 lift gets roller tip rockers. At those lifts with stock type rocker arms, you tend to get a lot of side loading of the valve stem. And that leads to faster wear on the valve guides.

Maybe the LS engines are different. But from what I'v read, they're pretty much the same. YMMV.

truckdoug

iTrader: (26)

i dunno, some that crap is ok. the less moving parts the better.
but the rockers are notorious

mOtOrHeAd MiKe

iTrader: (8)

226/230 .605"/.608" 113+3 on LXL lobes is what I am going to run in our junkyard turbo 4.8L; I will likely be pair this with a set of stock 241s. I might lightly hand port them if I am feeling froggy.

My main goal will be to avoid having to run high boost numbers generated from a restrictive intake path - I'd rather have improved flow. I can only handle so many "how much boost?" questions - just once I would like someone to walk up and ask about CFM or calculated air flow.

Forcefed86

iTrader: (4)

http://garage.grumpysperformance.com...-cam-lca.2782/

Looking at this article with Vizard's opinions you pick LSA first. He says there is only 1 LSA that will give optimal power output. Which is dictated by Cubic inches and valve size. Then plan the rest of the cam. Article says when the head flow is high in relation to the engine size (as it is in a 4.8) be conservative on duration and moderate on overlap. Then try to go for as much lift as can be achieved without mechanically compromising valve train reliability. I believe this is why the Triple 12 cam (and other JFR cams like it) work so well. They are on a tighter LSA with low duration and moderate lift.

So i was looking at the 111 LSA cams with 600ish lift and 220 or under duration and came up with diddly (besides the texas speed grinds). Ideally I'd like to try something like that. But I was considering the 1.8 rockers with a smaller/cheaper cam.

mOtOrHeAd MiKe

iTrader: (8)

I remember reading that a long while back - it means so much more now. It is interesting to see how a set of stock small valve 4.8L heads (1.89" IIRC) influence the LSA vs. a stock 2.00" valved head as it relates to the chart.

I really want to get my hands on some SLP 1.85 rockers and jam some Straub trunion bushings into them. I believe those would help amplify a smaller cam.

Less is definitely more. I always try to build the best N/A engine possible, then add a power adder. Boost will hide any mistakes.

If I get some time I am going to look at some if the classic Turbo Buick grinds because those were smaller engines with dinky valves. I wonder how right or wrong they are?

Forcefed86

iTrader: (4)

The OEM Buick head flowed like garbage. So you have low head flow VS cubes making a tight LSA optimal.(105-108 range) Where the LS has a great flowing head relative to the cubes making wider LSA’s optimal? Then add boost and it throws another wrench in. I’ve also heard you add 1.5* to you optimal NA LSA per atmosphere of boost. So if 111* is optimal NA, at 30lbs of boost 114* LSA would be optimal. Which we see a lot of on the “stage” cams in the 220-230* duration range on LS stuff.

I’m not totally sure that cam theory works on an LS engine either. Figure I can stick some 2.02/1.60 valves in any old gen1 SBC head and it won’t flow near what a small valve LS LS head does. So going solely off valve diameter doesn’t seem right to me. If that article was geared toward gen1 SBC/BBC heads I’d almost think you’d have to skew the table for an LS head since they flow so much more, even with smaller valves. So a better flowing head would push the “best” LSA to the right a bit so maybe 112 would be better…? Tough call. I did find it interesting they said to error on the tight side since going 1-2* too tight does very little to your “in power” range but going 1-2* too wide has a large effect. That said, I’m sticking to my guns with the 111* LCA. Playing with a JY motor I don’t have much to lose, and I like the idle chop.

Forcefed86

iTrader: (4)

So the 1.8 rocker thing is happening. Bought a summit set new ($370 rockers) in the classifieds for $215 shipped. I’ve read the total durations aren’t really changed but since the ramp is increased it “acts like” another 4* or so of duration plus the added lift? That sound about right? So now I’m looking at .575” or less lift. This opens up some of the smaller duration stuff.

Keep going back to this summit cam. Anyone know of something similar for less? ($373)

https://m.summitracing.com/parts/cca...make/chevrolet

216/222 @ 111 .561/.566 Would give me right at .600 lift on the exhaust side with the 1.8 lifters.

Any reason this wouldn’t work?

Spring suggestions? Was looking at the $164 PAC1219’s rated to .625 lift. I was thinking they would be lighter than a dual spring setup and better maybe?

Other option is the $229 BTR spring kit rated at .660 lift. Which I’d have to shim. Anyone know how much lighter the BTR “light weight” steel retainers are VS stock? Titanium worth it for $80 on something I’ll be revving to 7k ish at 25-30lbs of boost?

mOtOrHeAd MiKe

iTrader: (8)

I'd wait for something used to come up. If only because $215 + $373(ish) is going to be more than a custom grind from Cam Motion ($450?). You will probably find a nice used cam in the classifieds here or at Performance Trucks for $150.

The only thing I would validate is the ramp rate. This thread covers the concept: https://ls1tech.com/forums/generatio...-oem-cams.html

As an option PSI 1511ML springs should work.
https://www.briantooleyracing.com/62...e-springs.html

But, shimming dual springs would work better. Heck, do what I am planning and find a nice low mileage set... and shim away! These things have lots of life in them. I wouldn't spend the money on a few grams off the tip of a junkyard engine - unless they were included in the sale.

Darth_V8r

iTrader: (4)

The approach I always use is to figure out what valve events I want. The LSA will simply calculate itself out. As will the durations

Forcefed86

iTrader: (4)

Thanks for the input! Def. not cost effective with the 1.8 rockers. I just thought it was a good deal and jumped on it. I like the idea of a roller tip since I’ll be revving this thing pretty high. Suppose I can go over .600 now anyway with the roller tips?

The TSP 5.3 high lift cam is a 212/218 @ .600” and I can get it on a 111 LSA for another $15.

Would be a .635 lift with baby duration.

TSP's dyno testing on a "Stock" 5.3 shows a 17hp/7.6tq increase with this grind over the .550 lift version. Would bumping it up to .635 be pushing it too far?

Forcefed86

iTrader: (4)

A guy with a stack of dyno sheets taller than he is doing nothing but cam testing is pretty hard to argue with. I'm not saying he is right. (like I'd know the difference) But his experience makes me lean towards his point of view pretty heavily.

mOtOrHeAd MiKe

iTrader: (8)

Your lobes/effective lift might look like this:
____
|....|
|....|
|....|
/.....\



I think the problem is with where the flow on the 706s is going to stall (I have never seen a flow test past .600" lift). Which out of boost is going to make the cam a bit less desirable to putt around in. But, I have no doubt lots of stock long block LS1s have run cams like what you are proposing (the heads flow the same as the 706s), it is just that .9L that makes me leery.