GNCLONE

yeah, the search button and I are good friends.....anyway.....

True of False
A carbed setup will run better on a lobe separation of 109 or 110 or 111. EFI needs more like 114 or 116 for less reversion?

If someone did NOT want to pull the heads off to check for piston/valve clearance they would go conservative with cam choice. duration, lift, or both?

The LQ9 has flat tops so .525 lift ?or can I get away with .575 or even .600 lift?

I know to get new valve springs, but otherwise the stock valvetrain is good to 500 horse and 6500 RPM?

The Comp "Thumpr" cams - all show and not so much go? I couldn't care less what the exhaust sounds like.

thanks for the help

3pedals

iTrader: (3)

My opinion is that the carb setups will favour the narrower LSA's, like 110 or even tighter.
I honestly can't say what will fit into the LQ9 without flycutting, but I can say that the effort to do so will pay off with the ability to run EXACTLY the right cam.
I beleive the BEST cam , is 1 that a pro specs for you, I called Bret Bauer, and am really happy with my dyno results, there are certainly others who can help you, and it is TOTALLY worth the extra $50!
I know a guy with a stock, carbed LQ4, that installed the MutherThumper, and it runs GREAT, BUT it also NEEDS a 3500 stall, so you need to know that.

ZONES89RS

iTrader: (25)

The tighter lsa works better for carbs as well as bring power In faster In general, but the average EFI tuner does not have a good ability to tune fuel injection on a tight lsa. If your heads are not milled, the trex may clear, but a sure fire way is always check ptv.

pairof69s

i would also like to hear more discussion on this, as I would like to find a cheap Ls6/Ls2 cam to replace my stock LQ9 cam......I already have her tore down, So I would hate to button it all back up with that weeenie *** cam in it.....just wonder if that wide LSA would make it a bitch to get the carb tuned.?

GNCLONE

Super Chevy hopped up a stock LQ9 in a 2009 issue. They put (what I consider) a BIG cam in that thing - never mentioned reliefs in the pistons.

The Modus Operandi for a lot of people is to keep buying cams and experimenting. I am too poor and too lazy to do this!

How do I get ahold of Bret Bauer?

3pedals

iTrader: (3)

Bret Bauer Racing - (607) 738-5939
Sometime not the easiest to get ahold of, probably need to leave a message.

EDIT: I just read that you have an 1800-2000 stall, I think you should be running a cam similar to the GM HOT cam (218-230 @ .050"), but maybe with some modern aggressive lobes, and .625"ish lift. Let a Cam GURU sort out the exact valve events.

Barrett

speedtigger

iTrader: (16)

Short intake runner length is the reason for the narrower lobe center on camshafts designed for single plane intake manifolds. You will notice that the LS factory fuel injection intake manifolds have very long runners. Dual plane carburetor intakes have medium length runners. Single plain intakes have the shortest runners. This has much to do with the choice of lobe separation.

The general rule is: Long runners improve low RPM engine power. Mid length runners bolster mid-range engine power and short runners benefit high-RPM engine power.

Narrow lobe center camshafts capitalize on increased valve overlap to improve the diminished low and mid RPM torque characteristics of short runner intake manifolds. What happens is hot exhaust rushing out of the cylinder during the exhaust cycle creates a vacuum in its wake. This vacuum creates an increased pull on the intake port during the overlap cycle at TDC. This increased pull helps improve the low end and midrange power of the short runner intakes (single plane carb intakes).

Two things also should be considered:
Lack of free flowing exhaust can destroy any gains associated with a narrow lobe separation camshaft.
And, narrow lob center camshafts used with short runner intake manifolds will likely prefer a more advanced intake valve closing event.

One last thing. A dual plane carb intake will not have the same need for a narrow lobe center as a single plane. I would speculate that a dual plane would enjoy a 112 LCA.

GC99TA

iTrader: (30)

Lots of good points have already been mentioned by some knowledgable and respected members. So I have just a few minor things to add. Don't be overly concerned with lift numbers when it comes to PtoV clearance. Your tightest points with regard to PtoV clearance will occur just before and/or just after TDC (roughly 10* before till 10* after) when the valves are just off their seats and the piston is at or near TDC. Your highest lift points are typically reached when the piston is very low in the cylinder, and the intake valve is chasing the piston down the bore. Obviously the opposite is true on the exhaust side, but the principle of when highest lift occurs is still the same; only the chasing reverses roles. That is why duration and LSA are much larger considerations than lift.

Also, it is entirely possible to check your PtoV clearance with the heads in place. It may not be quite as accurate as the tried and true solid lifter and clay method, and requires additional tools, but some information is better than none. Here's what I personally do (disclaimer: I am not an expert, only a hobbiest):

1. Using a piston stop installed in the spark plug hole and degree wheel, find true TDC. Its a must (at least on big valve heads; LS3/L92) to first remove the rocker arms for the cylinder you are working on so there is no valve interference with the piston stop tool during the TDC finding process. Precision during this step isn't absolutely critical, but if you do it correctly right now, you'll be set up to later check the phasing of the cam. Once TDC is determined you can set your pointer to your degree wheel.

2. Next air up the cylinder in question with compressed air and swap out the valve springs for light weight checker springs. The purpose of the light weight springs is to keep from collapsing the plunger in the hydraulic valve during the clearance checking process.

3. Next reinstall the intake rocker only, but replace it's pushrod with an adustable lenth push rod. This pushrod should be set to zero lash so that it is neither compressing the lifter (shouldn't be able to) or articulating the rocker. You can check to be sure the rocker isn't being articulated at all with a dial indicator. Now you are set up to check your clearance on the intake side.

4. Start by rolling the motor to around 10* BTDC. I will then manually push the intake valve down until it contacts the piston. I measure the clearance by inserting a feeler gauge (really a stack of) between the valve tip and the rocker arm. I keep progressively adding more thickness to the stack until I have taken up the clearance I created between the valve tip and the rocker arm. One word of caution; the feeler gauges should freely slide between the valve tip and rocker tip without articulating the rocker backward and slightly compressing the lifter. The sum of the stack of feeler gauges that take up this clearance should also be reflective of the piston to valve clearance at this point in the cycle.

5. Now I repeat the process on the same valve in 5 degree increments until I reach 10* ATDC or until the clearances are widening and not tightening. The specific valve events, LSA, ect of your cam will determine when this occurs. I record the numbers at each interval and obviously the tightest clearance you find IS your clearance number. Obviously this same process is then repeated on the exhaust side.

So......some things that MAY be wrong with the method I described above. Well, the first thing is, it may not take into account for valvetrain deflection since the actual force of a real valve spring isn't taken into account. Another thing may be if too much clearance is "forced" between the valve tip and rocker and the rocker isn't detected slightly compressing the hydraulic lifter. Finally is whether or not an "actual" zero lash condition is properly set with the adjustable pushrod. But that would be a variable with the solid lifter and clay method too.

I will leave you with this. On the LS1 in my TA, I ran the clay test and the method I describe above back to back. I found the clay method to give me results that showed approximately .005 more clearance that the method I described above. So, I personally feel my "heads on" method is slightly conservative in it's results. Again, let me say that I am not a professional mechanic, engine builder, engineer, or otherwise qualified to say this is the "right" way to do things. I'm just a weekend hobbiest that likes to race and break parts. Take all of the above for what it's worth .

NemeSS

iTrader: (127)

Contact PatG on here. He is a sponsor and has many proven custom grinds.
He can have a cam cut to your specific needs. Or another good cam grinder and also a sponsor if Geoff at EPS.

streetknight2

iTrader: (10)

I called Texas Speed to ask their recommendation for this same thing. LQ9, carb, etc. Didn't want to cut pistons. They recommended their Tsunami cam on a 111 LSA.

I believe another member is running this same setup in a cutlass, I'm sure you've read the thread, but here's a link.

https://ls1tech.com/forums/carburete...arbed-lq9.html

GNCLONE

Thanks for all the helpful info. I knew you guys would have sound advice.

Fbodyjunkie06

iTrader: (10)

Duration numbers, lift numbers and lsa numbers are all just that, numbers.

Valve events are what matter, and the valve events dictate what the other numbers are.

The intake lobe duration is really what dictates the engines operating range, and the LSA plays more of a factor in what the torque curve looks like whether it is peakier or broader as does the ICL. More advanced ICL or LSA will make torque come on sooner and peak sooner where as a more retarded ICL or LSA will make torque later and broader across the rpm band.

In a boosted engine or nitrous engine the exhaust lobe really dictates the valve events as you are forcing air into the motor and how and when it gets out to get more new air in is more critical than getting the air in since it is being forced...follow?

In a N/A motor the intake lobe is a lot more critical to dictate rpm range and powerband. This doesn't mean the exhaust isn't as critical as it plays it's part also.

Hope this helps.

Joye227

I am also running a Texas Speed tsunami camshaft in an LQ9. 317s milled .020 and no PTV issues.

RabidStreetRacer

iTrader: (1)

Just got my Thumpr cam in the mail yesterday! Should have dyno numbers in the next month or so.

My build: 1994 2 door Silverado sport side
2000 5.3 LM7
Stock pistons/rods
Thumpr Cam 554/537 on 109 LSA
Heads rebuilt with 45 degree cut on valves, milled 0.015 and LS6 springs
2" LT headers with duel SLP loutmouth mufflers
Edelbrock Performer RPM intake
MSD 6LS ignition
Holley 750 cfm Carb
4L60E with Shift kit and corvette servo

GNCLONE

Okay, I have been processing all I have read. I know a lot more about cams now than I did a week ago! But now more questions.

I run a dual plane Performer RPM and have very high engine vacuum. I think a really tight LSA is not really necessary for this combo. Furthermore, because I am choosing to run the stock valvetrain (except springs) I will expect power from idle to 6,000 or so - consequently, I can't really use a high lift, super long duration cam. I won't be revving to 7,000 or 7,500.

So, because this engine is naturally torquey (6.0 D/P), to I capitalize on this with a cam offering torque, or do I instead look for more HP?

thanks again.

speedtigger

iTrader: (16)

I ran a dual plane for a while and it made very good power. Tests I have seen show that the dual plane manifold beats anything you can buy for an LS motor below 5000 rpm.

It is my opinion that you don't need any type of custom grind. I think an off the shelf cam in the 220s duration at .050" with a 112 LSA on 108 ICL is going to run great for you. And, there are lots of cams out there in that range.

I would also not go crazy on lift either. I don't think any gains in power over .600" lift worth the double valve springs and additional stress.

ZONES89RS

iTrader: (25)

Sounds like hot cam territory.