aaronz28

I've got the LT1 in my 327 now and it was originally a 327-365. I've come to the conclusion that the LT-1 probably makes more torque from 1500-3000 but I'm mainly concerned with 3500 and up, which is really where I'd guess both cams are the best.

Would I notice a difference from 3500 on up with the 30-30 as opposed to the LT-1? By the way, this is an otherwise stock 11 to 1 327 with 4speed, 3.73 gears, and 2 1/2 manifolds through stock mufflers.

Thanks

Aaron

SWCDuke

blackray

I have a 64 original 327/365 with 11:1 compression and 4.11 posi. You can see pictures of it on http://www.midyear.org (just click members then search all) and it is the first car on the first page in front of a B-17 bomber. I took out the 30-30 cam and had a special Comp Cam ground to match the 30-30. My goal was to have this engine produce the advertised hp/torque published in 1964 for this engine using state of the art cam shaft geometry/materials. On the engine dyno with single point ignition it came in at 367hp and 361 lbft of torque. HP peaked at 6,200 and torque at 3,800. Motor Trend did a road test on the 64 Fuelie coupe in 64 and recorded 1/4 mile time of 14.2 / 100mph. I took this 40 year old car to the track (my very first timeat the tree) and turned a 14.3 / 96.6 mph. It is too original to race but I have the record to prove it is possible. If you have a good engine shop they can work with you and the folks at Comp Cam to get you exactly what you want in performance. Based on my experience make sure you match the intake, ignition and final drive parameters up with the cam you're going to use.

Hope you always are enjoying the ride!

Brian

SWCDuke

There is an empirical formula that uses quarter-mile trap speed and weight to compute peak power. ET is more a function of traction and gearing.

Your trap speed of 96.6 is in the range of road tests from the sixties, which were typically 95-100 for SHP/FI engines, so you have no indication of increased power. I turned 14.4/102 back in the mid sixties with exhaust cutouts. My 340 HP SWC has a 3.08 axle, and I went through the lights in second gear, which is why the ET is high relative to MPH.

Your quoted power doesn't mean much unless you ran the engine with both cams and have back to back comparison data. There is variation in dyno calibration and some dyno operators like to see high numbers to "keep the customer happy." Also, torque bandwidth is the best measure of engine performance. Absolute numbers depend on dyno calibration and correction conditions. Lot's of games can be played, but the torque bandwidth will be about the same regardless of dyno calibration and correction factors.

This idea that current aftermarket cams are somehow better than the OE cams is a myth. The SHP cams, particularly the LT-1 cam lobes, which have very unique acceleration profiles show that Chevrolet engineers had a very keen insight into head flow characteristics and valvetrain dynamics in the late sixties, when the LT-1 cam was designed.

The question in the thread boils down to another issue, and I'll phrase it as a question:

For the SHP class engines, what is the component that has the biggest effect on top end power? Hint: It's NOT the cam!

Duke





[Modified by SWCDuke, 6:50 AM 6/25/2004]

ctjackster

ahh, back to cam dynamics 101 with Prof. Duke!

as for the question, I'd be guessing the exhaust side of the equation is what limits the top end power on my 65 L76, not even getting into the fact that I have the permormfance-defeating-but-sounds-faster side pipes on mine . . .

Crazyhorse

Solid lifters ! I remember you mentioning this before and my first vette was a 65 327/365 with the solids(which I didn't even know at the time), it always blew people away when I gave them a ride and cranked up the RPM's with the hooker sidepipes

I miss that experience, I think I'm going to put solids in the 66 one of these days.

Dave McDufford

Going back over my classnotes, for top end power, I believe it is headflow.

Dave

Crazyhorse

oops I replied too soon thinking about rpm' s

SWCDuke

Dave gets the gold star!

With the SHP cams the OE machined heads are choked at high revs. Even with the excellent head work that was performed on Dave's heads, they were choked at the top end, so more cam would have little effect on top end power while killing low end torque.

Despite choked heads, power kept climbing all the way to 6500, and the computed Mach index was 0.556. This is about as high a Mach index as you see at peak power for any engine, and it indicates that the cam is well matched to the inlet flow characteristics of the heads by getting the most out of them.

Power probably would have began rolling off 67-6800, dropping ever more rapidly above 7000.

The basic system engineering rule for a high performance Chevrolet V-8 is massage the heads for peak power and select the valve timing to achieve acceptable torque bandwidth.

Some of you may want to go back and review the dyno data that Dave posted a couple of weeks ago. More important than the actual measured values is the shape/bandwidth of the torque curve - 78/80 percent at 1600/2000 and it was still 86 percent at the redline.

It would be interesting to test Dave's engine with the 30-30 cam. Engine Analyser predicts marginally more SAE gross power, a bit less peak torque, and about 20 percent less torque on the bottom end. In the car with an exhaust system the 30-30 might produce less peak power because exhaust back pressure is going to have a more harmful effect due to the 30-30 cam's greater effective overlap relative to the LT-1 cam.

With headers an open exhaust the 30-30 cam will make somewhat more top end power in the 6500-7000 range. With the backpressure from an exhaust system, even with headers, its close to a dead heat at the top end, but the 30-30 just kills the torque curve at the bottom end.

The holy grail is a flat torque curve!

Duke





[Modified by SWCDuke, 9:05 AM 6/25/2004]

Solid LT1

The 30-30 will run to higher RPMs than the LT-1 but, for 3500 on up the "140" off-road cam will outperform either! That being said, I wouldn't use a factory grind in any performance engine but, would get a modern profile cam. For a street car a 327 likes the high 230@050 and a 350 will go to the low 240@050 range in a solid lifter cam (use a 4-6 degree larger exhaust lobe for most heads unless you have a really good exhaust port flow.) I like Comp Cams "tight lash" series and Ultradyne (Harold is now at Lunati Cams) solid profiles.

aaronz28

The idea that new cams are better is not necessarily a myth.

I believe there are a couple of things that really prove new designs to have the advantage. One big thing is tighter LSA. This really isnt' a new practice, just more accepted on aftermarket cams and ultimately makes the engines much more responsive. I know that a wider LSA helps vaccuum, bleeds off a little pressure, and broadens the torque curve, but there are ways to select cams for applications and still be ok in the vaccuum and detonation depts.

The big improvement in todays cams are the ramp speeds. Modern cams are hitting .050 duration figures similiar to early designs however seat to seat or .020 timing is much less, almost 20-30 degrees in some cases and the .200 duration figures are larger. This means higher cylendar pressure, faster and quicker fuel/air charges entering the chamber and ultimately increased horse power and more importantly torque bandwidth. Especially in a street motor. And all this doesn't have to be hard on parts.

I had a 1969 Z some time ago that I fooled with. That thing ran like crazy, and when I pulled it apart, found that it had a comp cams 292 hydraulic magnum cam, and a 350 crank in the 302 block.

I put the 327-350 cam in it,and it didn't come close, so I went to the stock 30-30 and was much better but still not close to the 292. I eventually tried the LT-1 cam and was not impressed either. I wound up putting the 292h back in and that thing was awesome. When I eventually restored the car, I redid the motor as a 302, put a Lunati cam in it, which was 224-232 at .050 with 500 lift and to this day, that little SOB killed the 350 and any other motor i've ever built using factory cams and I still put a crapload of miles on it.

With that lunati cammed 302, I ran against my buddy's councours 69Z and there was no contest, from a dead dig, and even from a 50mph stomp. And both cars were geard the same, stock heads, stock exhaust, same transmission, the only difference was the cam and slighly stiffer springs. When I sold the car, noone would believe that it was a stock Z, so I put the 30-30 back into that motor, and it had vintage vibe like nothing, but didn't perform anything like the Lunati did. And I'm talking about from 1500 on up through 7000 which is where I would shift it when I was in my crazy mode.

Now I still agree that choking an engine with unported heads and poor exhaust kills the top end, but my guess is that in the early 60s, the materials and technology weren't available or at least as resonable costs to design and build cams in the fashion they are doing today. Not to mention that you could have had a Granny wind up driving her Fuelly SWC to the grocery store so those cars and cams had to please the masses. I'm sure there was a fair amount of marketing involved in the engineering of those motors as well.

You can't tell me that Duntov didn't know that putting the 30-30 cam on a 110 wouldn't have made it feel a heckova lot stronger. Hell, Isky cams was doing that exact thing at the same time and those cams seem a ton stronger and a 40 year old ISKY grind is hardly modern cam technology.

To me there is something great vintage about 60's and 70's technology which is why i would ultimately like to keep either the Lt-1 or the 30-30 but I'm 100% that a new designed cam with faster ramps, ( shorter seat to seat duration and longer .050 duration) will outperform the stock grinds all day long.

I know of two people now that replaced their LT-1 cam with the Lunati (harold grind) 401A3Lun cam. It is harolds "LT-1 replacement cam" his seat to seat numbers are like 28 and 30 degrees less than the LT-1, the .050 numbers are similiar but slightly smaller, and the .200 figures are about 3 and 5 degrees larger. Lift is almost identical and it is on a 112 LSA. Both folks said that cam was like adding 50 cubic inches to the motor. More torque, faster accelleration, and harder and longer on the top end than the LT-1 and all with stock valve train, stock rams horn manifolds, and only setting lash about once a year at best.

I hardly doubt anyone would see those results on any desktop dynoor simulation program but I'm pretty positive you'd see hugely impressive results on the dyno.

Just my $.02


[Modified by aaronz28, 12:18 AM 6/26/2004]


[Modified by aaronz28, 12:28 AM 6/26/2004]


[Modified by aaronz28, 12:32 AM 6/26/2004]

aaronz28

and just incase anyone wants to know,
I don't work for any cam company LOL. I've just been on a research hunt and I ask questions that I really like to get peoples opinions and life experiances on.

I don't find the DD2000 or any of those programs helpful becasue there are simply too many variables that can change the outcome.

SWCDuke

Acceleration characteristics are limited by valvetrain dynamics issues. More acceleration requires higher spring force which reduces valvetrain reliability and durability. You can't have your cake and eat it too.

Duke

aaronz28

I agree, but the Stock Valve train isn't the limit of vlave train reliability. I know of several folks who have broken stock valve train under daily use as well as people who have used aftermarket stuff and had no problems.

In my cases, both using the 292h and the lunati, i had a ton of miles on the motors, never had to check valves, and they performed great and the motors are still going with well over 50k on them by now.

if switching from stock springs to aftermaket springs to accomodate higher lift cams and more aggressive ramps meant that the motor was gonna fall apart, then I'd totally agree with you regarding stock cams and valve train, but that isn't the case. Well at least not any more. Maybe 10 or 15 years ago, but I am confident that you can use any of the new Comp, Crane, Lunati or whatever you choose, and be much more useable on the street, unless you are really after the way these cars performed originally.

I'm not stating that the LT-1 or any GM cam isn't an excellent choice, I just know from personal experiance of using several different cams, that some of todays not so radical cams really outperorm the old stuff in every regard. And I discovered that these results are far more realistic than any simulation program can generate.

I still love the sound of these babies, I just think that like anything, technology has become so advanced that it shouldn't be unthinkable that after 40 years, billions of dollars of research, and probably another billion dollars worth of broken stuff, that engineers and designers might have developed something better than they were able to come up with in the old days.

I think the biggest problem people have with broken parts and unusable and unstreetable cam choices is that people often pick the next bigger size than what is reccommended to them just becase they think it will make them more power. Every single time i've gone against the tech reccommendations of various cam companies, i've been unhappy. And every single time I let them direct me in the correct direction, i've been more than pleased.

I'm not saying that everyone should go out and yank their GM cams and replac them with new stuff, but unless you are after dead stock factory performance which is an awesome goal and something that I value very highly, then I think there is serious power to gain both in torque and HP by using a modern cam designed to work propoerly with your given application. And yet this will be something that will be just as reliable as usable over the next 100,000 miles as the OE stuff.

Dave McDufford

The Crower cam we looked at, in my opinion, made a couple of lb/ft more torque than the LT-1 at certain rpms (Duke does not agree). However, the additional cost of the components required to make this power reliably was about $1,500. It simply did not seem worth it.

From what I can tell the limitation on a SBC is the heads. Even with aftermarket heads, there is only so much air you can move on a SBC even with an instantly opening .750 lift cam, particularly if you want it fit under a small block vette hood. With my stock looking engine (461 intake, Holley 2818, 2 ½ ram horns, 327 block), the LT-1 cam was about as good as it was going to get.

Out of curiosity I looked at building a small block 427 (aftermarket block) but even with $2,000 heads it ran out of air fairly quickly (from what I could tell).

Similar to your point regarding people who do not take the cam advice and go with a larger cam I decided to listen to the experts. Duke Williams, John Hinckley, Wally Knoch and others designed engines and worked for the automotive companies as professional engineers for their entire careers. I believe they know what they are talking about and they all say the same thing.

Let’s agree to disagree.

Dave

aaronz28

Dave, just for curiousity, I'd be happy to know the specs on that crower cam you were looking at. And also what means you used to determine how it would compare to the LT-1. I'm assuming that it was a hydraulic roller.

And I respect the beliefs of those who have been around and have much more knowledge that I do, however I know what my own experiances are and that is why i'm always on this research for knowledge.

Thanks

Aaron

66427-450

well, there are several different definitions of "great" and "awesome" when it comes to cams. for my '66, i value power from 4500-up, and will gladly give up some low RPM power, or power band width, to get it. but hey, we're all different, and i respect those that want more power down low, it suits their needs so more power to them.

the point is, you can't win an argument, or persuade someone to agree on what constitutes "a great cam", if their goals, or values are significantly different from yours.

like Dave said, the best is to agree to disagree...... and




[Modified by 66427-450, 3:04 PM 6/26/2004]

Dave McDufford

It was the Crower 00466, the specs are on the Crower site. We ran it using a couple of different simulation programs. Duke runs them better than I do.

FYI, he was within 5 hp of my peak power, underestimated low end torque but said the program was low before the dyno run, and was high on midrange torque but I think that was caused by the carb problem (secondaries) I was having during the run.

Dave

aaronz28

Well considering that the Crower you selected is hydraulic and like 20 or more degrees less duration at .050 and even smaller duration at .020 than the LT-1 which is a Solid flat tappet as we know and still making the same or slightly more power, confirms exactly what I'm trying to say about modern cam design.

Every cam company i've spoken too says that you can make more power and torque with a solid flat tappet than you can with a hydraulic roller anyway. The advantage of the hydraulic roller is never having to adjust lash and loosing a little friction, plus being able to run much more agressive ramps, which isn't the case with the small cam you had selected.

That Crower cam you mentioned is much smaller than the LT-1 and that is amazing that it would make the same power across the curve and it would definately be more responsive because it is so much smaller plus it is on a 110 LSA as opposed to the 114 or 116 that the LT-1 is on.

That 1500 bucks additional for the roller conversion would paid for itself in one summer worth of gas mileage. LOL But even with a flat hydraulic cam I'd bet you'd be in the same ball park.

Rollers only really take the advantage because of the aggressive ramps that can be achieved with them where a flat tapped would walk right off the cam. With comparable ramps, roller vs flat tappes is only worth about 5% worth of friction loss according to every cam manufactuer I've spoken too.

Anyway, I know we will always agree to disagree and I'm certainly not looking for an argument, just trying to justify my own beliefs and thoughts for my own cam selection based on what the folks here have learned.




[Modified by aaronz28, 10:33 PM 6/26/2004]

mrg

I too was going to go with a different cam instead of the LT-1 I installed in my 327. It was either going to be the Comp XE 262 or 268 grind. From what I gathered in reading Comp Cams literature and in some questions I had emailed to Comps Cams their proprietary cam grinds seem to be pretty aggressive with respect to lift. This seems to be across the board with their cams whether hydraulic, solid, or roller lifter grinds. The aggressive cam lobe profile and the tight 110 LSA of the Comp cam didn't strike me as being conducive to durability and reliability for the sake of a few extra horsepower. Those cam designs of yore weren't exactly in the 'stone age'. Somebody had to write the book .. ! ..

John