clearrun

Does anyone have the cam specs for a 67' 427 / 390 HP engine? I believe the designation was L-36.

clem zahrobsky

cam# 3883986 dur @ .050 214/218, lobe seperation 115, open/ close spec @ .050 lift, intake open -3 closes 37, exhaust opens 49 closes -11, lift .461/.480 :chevy


[Modified by clem zahrobsky, 3:01 PM 5/15/2003]

clearrun

Thanks Clem for the quick response !! Just bought engine analyzer software and am anxious to try some combos and compare to stock. :hurray:

StrayDog

Ancient tech, the L36 cam was designed in 1965 , before computers......., actually a Comp cam mild XE 252 , has more lift , fater ramps, higher vacum than the L36..much improved throttle response...............inadition to more streetable tourque & HP ...............if you have 3.08 go with XE 262 , 3.36 or better XE 268, all cams mentioned are high lift short duration quick ramps, (compuetr designed)..........& wiil clear stock pistons ...example the XE 262 1300/5600 RPM >>6000 redline 500 /515 lift.............take this advice from someone who has rebuilt a L36 (Now 433 cu in) .30 over & gotten rid of the old tech......I am not a NCRS dont drive my Vette & wax &polis all the time but a driver /cranker who actually drags the 1/4 mile in my 66 big/block,,,but have been a(NCRS) member for 18 years.......The cast iron L36 intake wieghs 70 pounds ..thats next & then MSD ignition ,,,then.............................. :crazy: ...........you will be very pleased.....The Dog is & worked for me :steering: :seeya :auto: WOOF WOOF :flag :party:


[Modified by StrayDog, 12:01 PM 5/17/2003]


[Modified by StrayDog, 12:03 PM 5/17/2003]

SWCDuke

QUOTE]Ancient tech, the L36 cam was designed in 1965 , before computers


[/QUOTE]

Chevrolet had both computers and the Optron well before 1965. Their
understanding of valve train dynamics back then was excellent, and it shows if you take an accurate lift crank angle diagram and reverse engineer an OEM cam to determine their design parameters such as valve acceleration.

Though I don't research BB cams, I have NEVER found a SB cam that outperforms the LT-1 cam in terms of torque bandwidth, and it has some very clever design features such as asymmetrical profiles to set the valves down on the seats more gently than they are lifted off the seats - something that aftermarket cams do not incorporate to this day. The aftermarket typically builds several cams off the same blank, which is why they offer several durations with the same lobe center angle. This is done to economize manufacturing cost, not performance. Chevrolet cams are all built off custom blanks for each cam, so the designs weren't compromised by using a single blank for multiple finished cams. The manufacturing volume justified special tooling to cast the blank for each specfic design.

Computers don't design cams - people do. Good design starts with understanding valve train dynamics. Computers just make the calculations easier than running them by hand.

OEM cams are also easy on the vavletrain, but the BB valvetrain is more problematic than the SB valvetrain, so more rapid than OEM valve acceleration could result in poorer valvetrain reliability.

"Computer designed cam" is just marketing hype. The evidence that I've gathered over the years indicates to me that the OEM designs are superior for the intended applications, and the manufacturing accuracy of OEM cams is superior to most mass marketed aftermarket cams.

Duke

StrayDog

not to initiate :cuss or :mad but the 21 st century enginering has made a difference, in all auto motive tech, cams ect>>>> the ZO6 puts out honest 405 HP..not inflated HP , the 1/4 miles times & reflect such as well as throttle response gas milage effeciancy ect..........Example>>>..Electronic ingnition is far superior to points...........mono rear springs also are state of art& superior (model a springs on C2) & flow rates etc on modern heads.........not to start a :rant: , I was just advising my 2 cents & what has worked for me. not initiating the NCRS/ :cuss ( wax um, clean tire threads, not drive um&never go 1/4 mile)>>>>My opinion === ONLY without question the way to go,AGAIN only,my opinion & my 2 cents, IE>>> dont spend the big money on ancient tech, if available go with the 21st century>>>>>>>>>>>>> :thumbs: My opinion :eek: The Dog :nopity DRIVE HARD & ENJOY ,Modern tech makes your C2,,,more enjoyable driveable ,dependable , more Hp & Torurque
.................................

[Modified by StrayDog, 3:43 PM 5/17/2003] :steering: :auto: :party: :thumbs: :seeya


[Modified by StrayDog, 3:45 PM 5/17/2003] :seeya :flag


[Modified by StrayDog, 3:48 PM 5/17/2003]

SWCDuke

The modern small block has much better flowing heads and manifolding, symmetrical runners with port injection, better valve train geometry, and electronic control of the fuel and spark with knock sensors to allow the engine to run at the ragged edge of detonation all the time, so power and fuel economy are optimized across the entire operating range, The superiority of the modern small block to vintage engines is inherent its entire architecture and detail design.

The LS1/6 have relatively short duration high acceleration cams made possible by the better valvetrain geometry without excessive spring pressure, and the LS6 is even more aggressive than the LS1, but requires light weight hollow stem valves to keep the valvetrain together with OEM reliability.

You could not use these aggressive lobes on a vintage engine and expect the valvetrains to live.

If you do enough simulations using more than one program and test a lot of cams, the conclusion is that there's nothing magic about current aftermarket cams relative to the vintage OEM cams, especially if you stick with cams that will work with the OEM springs. A fast action cam that requires a stiffer spring might make better torque bandwidth or more top end power depending on the duration and overlap, but at the likely expense of valvetrain durability.

Duke

clem zahrobsky

the cam companies learn from GM because now they market the LS-1/6 "beehive" shaped valve springs because if the weight savings in the valve train to allow higher RPM without valve float. :chevy


[Modified by clem zahrobsky, 5:08 PM 5/17/2003]

Vetterodder

IMO, matching the cam to the car and it's intended use is more important than whether it happens to be old tech or new tech. Considering all of the variables like car weight, gearing, etc. as well as personal preferences such as a smooth idle and best low rpm power or a desire for a "bad boy" idle and the most high rpm power, I don't see how any one cam could be the best choice for everyone. I love my XE-274 but only because it's well suited to my particular car and to the way I use it. I have no doubt that 95% of other owners would hate it.

I also think "new tech" may have some advantages over "old tech" but that's never stopped me from recommending L79 and LT1 cams. If I actually believed that new is always better than old, I sure as hell wouldn't be driving around in a 38 year old car. To me, the single best advantage after-market cams have over factory cams is the huge selection which allows us to get as close to ideal for our particular application as possible.

Kid_Again

...yeah, straydog, i wouldn't be so quick to trash that L36 cam...as far as the more aggressive newer designs, if you don't have better valvetrain components to follow that more agressive profile, you won't get the return you expect....computer design is just another marketing tool, it's the brains behind the cam design that makes the difference...i suspect that, if you kept your L36 cam (assuming it was in good shape) and just went to roller rockers, you'd be in hog heaven......i ain't no engineer but i try to read as much as i can and from what i read, it's tough to beat the 390hp cam as far as hydraulic cams go...maybe somebody can run a comparison on some dyno software and post the results


[Modified by Kid_Again, 4:35 PM 5/18/2003]

JohnZ

Not aiming at anyone in particular, but I spend a fair amount of time on other boards that are much more oriented toward mods (like "big" cams, roller setups, aftermarket heads, etc.), and what I see every day on those boards leads me to believe that most (not all) guys who buy "big" cams from Comp Cams, Crane, Lunati, and the rest of them buy cams that make their cars sound "nastiest" at cruise-ins and have "big numbers" they can BS about. Most of these guys are also the ones who complain all the time about wiped lobes, shattered roller needles, bent pushrods, broken rockers and springs, bent rocker studs, and spend their whole life trying to find a carb/ignition/converter stall speed/gear setup combination that will make their cars driveable back and forth to work and school with their "big" cams.

It's hard to beat proven GM factory-stock performance cams and valvetrains that work, are completely reliable and streetable without experimenting, and don't require monthly engine teardowns to keep them running. Pure race cars are one thing, street-driven cars are another.
:cheers: :steering:

Kid_Again

...even i see that kind of craziness down here in frog pond...put in a big cam, not enuf....put on a 900 cfm double pumper, not enuf....trash the vacuum advance and go with a custom mechanical advance distributor....and they're never happy with the car...."gee, i cry when i start the car in the garage and the plugs look awful, think i'll go to a hotter plug" :rolleyes:

...i think straydog's got a decent combo and i almost stayed with the L36 cam but i love to wind 'em up...i don't think the profile leaves any excuses for a good hydraulic, streetable profile...JMO.......

...straydog, just don't tell me your goin' to a double pumper :eek:....

...at LEAST you have oval ports




[Modified by Kid_Again, 6:15 PM 5/18/2003]

StrayDog

Kid Again, I have endlebrock alum oval port heads..........& to answer your question, alredy have a 750 Holley Double Pumper......my 427 pulls very strong to 6000 rpm(.need to update my signature).......next 1/4 mile..oldies day at the drags July 10th....last year with L36 cam best ET 13.7 @ 102 mph (2.6, 600 foot time no traction)........308 rear gears , the XE cam has raised my tourque curve , looking for better traction & hopefully 13.2 :party: :steering: not trashing L36 cam , just stating my opinion.>>>>>>>>> wanted a cam with more lift, short duration & quicker ramps to take advantage of my large valves 2.19 " intake & breathing ability of my heads,,,,,,,,,,,,, :steering: :seeya


[Modified by StrayDog, 9:48 PM 5/18/2003] :flag


[Modified by StrayDog, 9:49 PM 5/18/2003]

64BB

with all of these numbers floating around, can someone tell me: what was the original cam that gm put into the L-36 390 hp engine???

clearrun

Duke,
I have been reading your posts on cam designs engineering for four years. I am not a mechanical engineer, but the points you make sound convincing to me. I am just starting to use engine analyzer to try and learn something on my own. A couple of points that I would like to bring up are:

- When GM designed the L36 cam it was done to match vavle train components and technology available then. They had to ensure that their engines would last under all kinds of driving conditions.

1. I drive my 67' less than 1500 miles a year, usually in the cruising mode and in warm weather. I don't care about gas milage and I love to tinker with the engine as much as I like to drive it.

2. The highest octane gas I can get on the street is Sunoco 94, so one of my major concerns is pre-det. That was not a concern for GM.

3. I love to listen to a good muscle car idle and have no power accesories, so vaccuum is not a concern. There is something about a 67' BB with that hood and side pipes that does not equate in my mind to a pickup truck idle that an L-36 has

4. Bottom line is that I want as much horsepower and performance from a stock looking L-36 engine that I can buy today while running on pump gas and without wasting my $$ on the wrong parts. Based on lot's of reading and recommendations from this forum, I think that the best way to spend my $ are on head work, and a higher performance cam. I am doing runs right now to understand what cam might be best and I do not intend to go over board. But considering the time and effort I have put into the car and engine so far, and the fact that I have a specific application as opposed to GM that was trying to design for all conditions I think I should be able to find a better match than the stock cam.

5. Comp Cams steered me away from Stray Dog's recommendation of XE cams because they are designed to create higher cylinder pressures for lower CR engines. If I keep the 10.25:1, I was told that I should not use the XE cams because of pre-det concerns. I will be looking at all of this in my Engine Analyzer rune.

Thanks again for your informative posts. I read them all !

clem zahrobsky

the part # is in my post above 3883986. there was also a 3904364 cam listed for these engines. i think it was the same cam:chevy

SWCDuke

I can't speak specifically about the L-36 cam. My research has focused on reverse engineering the SB mechanical lifter cams to understand their design philosophy and uncover the design tricks they used - like asymmetrical lobes.

GM has rigorous durability tests that all production engines must meet, both in the dyno cell and test driving in cars, so their cams feature modest acceleration and modest valve spring pressure to assure long term durabililty.

I understand the desire to "upgrade" the L-36 to yield more of a SHP character. One way to to this is to install the L-72/71 mechanical lifter cam, and pocket porting the heads would be a good idea to get the most out of the top end.

Chevrolet mechanical lifters cams are very difficult to model for the simulation programs, because their published specs don't really relate to real world timing. Their duration numbers are often speced at some unspecified value above the base circle and can include a good amount of the clearance ramps, which is not a reflection of when the valves open and close. The only way I found to develop accurate cam files for the LT-1 and 30-30 cams was to take lift-crank angle diagrams, and the timing number I use for DD2000 and EA don't look anything like published specs.

As a general guidance, if you want to use an aftermarket hydraulic lifter cam keep the duration at .050" lifter rise to about 230 degrees with a lobe center angle of no less than 114. This is the same LCA as the the L-79 cam with a little more duration. The centerline of the L-79 is 110 inlet and 118 exhaust. The exhaust is phased fairly early because of the SBs restrictive exhaust port, which only flows about 65% of the inlet. I don't know the ratio of exhaust to inlet flow for the BB oval port heads.

Maybe if Clem, or someone else has the flow ration data I can come up with a closer recommendation, and Clem might have some good recommendations based on his BB experience.

Duke

SWCDuke

Read the first response (Clem) to the original post.

Duke

clearrun

Duke,
If GM did not specify those cams in a standard manner, isn't it likely that the published L-36 specs are also not useful. Seems to me that somone must have taken a degree wheel, a dial indicator and did the measurements on these cams installed in the engine somewhere along the line in the last thirty years. You could install a solid lifter and make the same measurement on any hydraulic cam. That is all it would take correct ??

Goodname4ID

Kid_Again mentioned just trying roller rockers for increased performance...

Which roller rockers fit under my stock L36 valve covers??? Anyone have experience with putting 1.6 roller rockers under their stock valve covers please tell me about it.

thanks,
:steering: