critter

iTrader: (9)

Man, you do find the neatest stuff

J-Rod

Bink was nice enough to send along his copy of the Camshaft Reference Handbook by Don Hubbard which I have been going through (thanks Bink).

Here is something I found interesting on page 38:

The subject of maximum valve lift has many facets. Valve lift in rocker arm engines is the result of the cam lift times the rocker ratio. Mild cam profiles (low duration) don't have enough cam rotation angle to build much lift coming off the base circle before it gets to max lift. The larger duration in the cam profile desing (the more the rotation angle) allows you to build higher lift before you must start closing the valve.

Quite often, engine technicians are confused when they flow modified cylinder heads on a flow bench and they find that flow (at low pressure drops) stops increasing at .500 to .550 valve lift. They question the benefit of using .600, .700, or .800 valve lift. Some people just say "more is better", so go ahead and use the most lift you can get.

One way to look at it is if you run higher lifts, you get to .550 lift quicker and exceed it longer then if you just try to reach .550 as the maximum lift. This way, you will flow maximum flow longer. It is usually poor cam design practice to dwell the tappet or valve at maximum lift or any other lift point because it causes acceleration to change rapidly and forces within the valve train can become violent and excessive.

Realize that the flow bench is steady flow but the engine is making pulsed flow. The piston is what forces most flow to happen and it has maximum velocity located in the range of 70 to 75 degrees from TDC depending on the stroke to rod length ratio. Best engine power usually requires that the intake cam lobe centerline (where max lift occurs) be timed around 105 to 110 degrees from TDC. This is 30 to 40 crank degrees away from the point of maximum piston velocity. This is the main reason why higher maximum lifts work better powerwise because at highest piston velocity , the valve is sufficently open to flow the volume neededeven though max piston velocity is not occuring precisely at max valve lift. There is enough valve lift to produce all the flow that theport can handle.

It is important to consider how much valve lift you have when the piston reaches maximum velocity because that may sometimes help you tune for your best power.

racer7088

Jrod

""2. MEASURE the AIRFLOW of the port in question at a known standard of FLOW DEPRESSION, finding the peak LAMINAR FLOW Air Flow point. (NOTE: I always preferred 1.5" of H2O, which is Holley's standard, and I was always comparing to entire system flow-through. This equates to 21.3" of water depression at Sea Level, but most flow at the arbitrarily chosen 28" of water.) Whatever, everyone needs to agree on a standard, then a cross-reference can be used for the rogues.""

28 inches is not an arbitrary drop. I would look at all further information with some scepticism if this guy doesn't know why 28 inches is a standard right now.

Ed Curtis

Always the troublemaker huh Erik???

BTW... Have you tested the AFR LSX at 40 in/h2o yet???

Ed

J-Rod

Always good to hear from you guys.

Hey, if the guy is wrong, then he is wrong. I'd rather have folks know if some of the internet "experts" are wrong, or if they are passing bogus info. I post this stuff up to invite comment and discussion, so I would consider this a positive.

The author may have made an error in syntax, or he may just be flat wrong, but its good for folks to understand things better.

Other than that one comment, what do you think about the rest of his comments. Also, I know some folks use 25", some folks use 28", and some folks use something else, and then correct it to the 28" standard.

Cstraub

iTrader: (1)

Mr. Miller is an "interesting" guy. I have spoke to him a couple of times concerning rocker arms. . .I will leave it at that.
Calculating lift. . .many "events" have to to be taken into consideration. . .it took me years to gather the figures needed to "match" camshafts to engine combos, nevermind the $$$ it took to have the software written. So I won't go into detail but with CFM/valve area/ and max rpm you have a good starting point to calculate lift.

I have made it no secret that I feel the lift on these LS1's is to much. The engine enjoys probly one of the best production cylinder heads ever produced. By using moderate lift and split ratio rocker arms on these cars more "useable" power can be made.

Chris

etperformance

So, assume excellent flow #'s on LS1 heads, all bolt ons, automatic, etc., how would a cam with specs of say 232/236 .595/.601 on 114 perform at the track N/A and small bottle with 3:73 gears, 28" tires, 3800 stall?
What would change if the sam car changed cam size to 244/248 .612/.615 on 114 +2. I want to see if your stuff adds up in the real world. No flame intended.

BigTex

iTrader: (16)

Where does intake orifice flow and plenum design come into play?

This thread is full of guys trying to come up with proper cam duration based on head / intake flow numbers taken from a single intake runner and port. It seems that the intake design and opening would not be challenged by flowing only one port. Under real operating conditions, can the entire intake track support those flow numbers with all 8 cylinders trying to feed the system?

Cstraub

iTrader: (1)

ET,
Without combination, airflow, and intended operating range I have no idea what the change would be. 1st cam may be way off, 2nd may be optimal. . .or vice versa.

Tex,
You are right on. . .most will not spend that kind on money on a camshaft though. There are a few custom benches that will flow a head while on an engine. These are as close as you can get to real life. Very high end engine builders flow the entire cylinder range when figuring camshaft specifications. Multiple lobes on a single shaft are still common, but not as common as years past.

Chris

etperformance

My intended use for this car is specific to the 1/8 mile dragstrip. I trailer it in case I break it. I can tell you that my current camshaft makes 405.9 / 410.9RWTQ, with the max HP being in the upper RPM range. I guess you need all of the pieces of the puzzle. I have no idea my head flow numbers, but I use the bottle, and was just wondering, based on this discussion, if I were wasting my time with the cam swap. The motor is torn down anyway, and the cam is not really costing me anything. I guess that is the only reason I even read this 36 page post. Actually, I am more confused than anything at this point. Maybye I'll just stick it in the car, and let the track do the test.

BigTex

iTrader: (16)

Thanks for the quick reply Chris. Just guessing, I would think the complete intake path will be more of a restriction than most good exhaust systems. Now lets say we have the ideal 80% ratio when looking at head flow vs exhaust flow (with intake and pipe); in simple terms this would "generally" call for a single pattern cam. Given the restricted intakes currently used on the LS1 with the availability of a fast free flowing exhaust, wouldn't that require crutching the intake lobe?

If that thought holds water, what would the end result be if you stuck with a single pattern cam, but put some restriction back in the exhaust to even out the flow ratio?

DenzSS

ET,

Before you do anything, you really need to gather some data. You can't match anything without knowing what the pieces are.

Chris would need at least your cylinder head flow numbers as well as the intake/exhaust characteristics, your bore and stroke, and your desired RPM range.

DJ_951

This is a great learning thead, a little over my head, but so was changing cams 3 years ago. Now I have changed 3 on camaro's. I'm on my 8th (V-8) camaro. In stead of making them faster I would purchase faster production camaro's or atleast not as tired. I have worked my way up to a '99 M-6 with SLP lid & bellows plus '98 SS muffler. (2.75") I just sold an old camaro from the collection and have $2500 for mods.

Don’t need cats
Daily Driver (maybe winter)
Car has 50k, run for another 100k
Won’t see a quarter mile track, ok maybe a few times for fun, street tires 275/40-17
Won’t run open exhaust, don’t really want that loud of an exhaust also no full length headers, clearance and other daily driver issue’s (I think)
Think sleeper just a plain pewter ‘99Z w ZR-1’s and T’s
Doing once, next project is the old ’75 camaro

Will need for any mods: Frame connectors $260
LS6 Intake $465.99
ASP pulley $189.99
Z06 MAF $149.99
Total $1065.99 $1434.03 left to spend or so

Please help me pick the best package:
A: Z06 cam kit w/ oil pump and timing chain $650.00
MAC’s w/ off road y-pipe ceramic coated $689.99
HPP3 (used) to raise rev. limit $200.00
Total: $1539.99 over but ok

B. TR224 kit w/ oil pump and chain $904.99
MAC’s off road y-pipe & cat (delete) $289.99
Tunning (cheap) $400.00
Total: $1594.84 over but ok

C. Z06 cam kit w/ oil pump and chain $650.00
MAC’s off road y-pipe and cat (delete) $289.99
3.73 gears $250.00
HPP3 (used) to raise rev. limit $200.00
Total: $1369.97 like in budget
Thanks

Sorry read a lot, still learning with low posts

Cstraub

iTrader: (1)

Tex.
The LS1 engine suffers like most Honda heads, it has really good exhaust. Honda's cams are crutched most being 6 to 12 degrees more duration then the exhaust. 80% in my opinion is not ideal. I like exhaust to be in the 72 to 75 range. Which to some is still high. You are 100% correct when you say the intake lobes need to be crutched on an LS1. You are going in the right direction. In fact the only single pattern cam I have grown for this engine series is a TEA headed blower car. My shaft and 3 others are all going to be run on it. . .mine being the smallest and the only single pattern.

In most cases these engines do not need crutched duration on the exhaust.

Chris

BigTex

iTrader: (16)

Interesting. I recently bought a new set of TEA 6L stage 2.5 heads (not installed). The exhaust flow on them is 279 @ .600. After reading these cam discussion threads a few times, I'm re-thinking everything.

racer7088

""Always the troublemaker huh Erik???

BTW... Have you tested the AFR LSX at 40 in/h2o yet???

Ed""

Ed,

I'm not causing trouble just trying to edumicate some people!

I still haven't even seen these new AFR heads and we have ten sets on order or something. Maybe Chuck cancelled on them but I've been up to my eyeballs in race engines and this week will go back to regular stuff. I'd love to see one of the new AFR deals for real. We have all their other heads.

Cstraub

iTrader: (1)

Tex,
That was why Denzss started this thread, as to get people to think about choices. Ed Curtis called the camshaft the "Brain of the engine" in one of our discussions years ago. . . he is right.

Chris

critter

iTrader: (9)

Chris,

What additional hardware (besides the head) do you want when figuring that ratio - intake, radius on head, pipe on exhaust, etc?

With intake and exhaust pipe, the typical vendor's head here is probably closer to 90% ...

Cstraub

iTrader: (1)

Carl,
If you are after every bit of power, it is my opinion you should flow the induction system you are using and the exhaust manifold that will be on the car. Now to take it a step further, optimum intake lengths can be calculated and exhaust primary lengths can be calculated for air pulse tuning. . .this further increases the "potential power". For this I need port lengths.

Food for thought Carl, with an exhaust port flowing 90% of what the intake side is, does it make sense to think an efficent engine needs camshaft duration and lift on the exhaust that exceeds the intake?

Chris
PS. Anyone read the rule changes in NHRA Pro Stock. . .no more light ceramic composite rods. . .wonder why?

critter

iTrader: (9)

Yeah, I guess if it was the grocery getter, we wouldn't really care, eh? But thanks for the reply. I was guessing that is what you would do. But it does say that we have our priorities wrong in F-Body land.
Of course. We have very limited choices for intakes. I would have built my headers if my car were a max effort car. Actually, I just realized that this is the first set of headers I have ever bought. Anyway, I suspect that very few guys here have custom headers, but we should if we are serious about power.
Not to me. My cam has more area on the intake for that reason, but perhaps more by luck than sense. My technology was 30+ years old, so I am doing a lot of refershing and learning. I started to buy parts too early but got lucky and did the right thing on the cam.
That puzzles me. I understand how light rods reduce HP loss to inertia, but if everyone runs them the playing field is level ...