L79flight327

Duke: Agree and understand...i apogise my prio post was not consise. (6am no coffee) 😏 I was able to find the basic lift and duration for the L46/962 on sumit racing or jegs web sites but they dont provide the actual valve events like actual intake closing and inrake valve at .50 like you find on a cam card. As shown in my OP all the cams have simular lift and duration. The actual valve timing events is what i am after....for the L46/962...

jimh_1962

I am running:
L79 Nostalgia Plus Cam: 229/236 .468/.462 LSA=112 Intake CL = 108
Intake Open 30 BTC / Intake Close 66 ABC
Intake Duration = 276 degrees / 229 @.50
Exhaust Open 78 BBC / Exhaust Close 26 ATC
Exhaust Duration: 283 degrees / 236 @.50
LSA = 112 degrees

I interpret these events to indicate:
1) L79 Plus Cam is Advanced 4 degrees since LSA-ICL = 4
2) Overlap seat to seat = 56 degrees (30+26)

With flat top pistons. Its 10.5:1 and runs fine with normal 91 octane gas.

L79flight327

Duke: Enjoyed reading your tuning seminar at lunch today...

For those like me that may be interested in the L82 or other OEM cams , Crane Cams has a Muscle Car cam catalog with many of the the original GM performance camshafts including the L79 and the L82. The L82 is Crane Cam Part Number 11-3896962. I am new to the forum and file attachments but hopefully the L82 cam card is attached to this post, If not the cam card reads:

@ .50 events:
Intake: Open (3) ATDC / Close 47 ABDC Max lift 115 degrees Duration 224
Exhaust: Opens 45 BBDC / Closes (1) BTDC Max lift 113 degrees Duration 224

@ .004 events:
Intake: Open 27 BTDC / Close 85 ABDC Max lift 115 degrees Duration 292
Exhaust: Opens 74 BBDC / Closes 34 ATDC Max lift 113 degrees Duration 288


Crane Cams recommended their 100132 Grind 278 H10: 222/222 .465/.465 LSA 110 Intake 105 2000 to 5800

The L79 intake closes at 101 ABDC
The L82 intake closes at 85 ABDC
The Crane 278H10 intake closes 68 ABDC
The L79 Nostalgia Plus intake closes at 66 ABDC
The Comp 268H intake closes at 60 ABDC
The ISKY intake closes at 48 ABDC.

Does the earlier the intake closes make more compression thus more torque?

SWCDuke

About ten years ago when I was in the process of designing a couple of custom cams for the Special 300 HP configuration. I wanted to use a lobe from the L-46 cam, but Crane didn't have the lobe masters at that time, but apparently they do now. The cam card lift is correct, but both POMLs should be 114.

The card states that it was used on the LT-1. Obviously this is incorrect. The IPOML is 4 degrees later than the L-79 cam because the 350 has a longer stroke, which is why I recommend moving it back to 110 on 327s.

Retarding the IPOML shifts the torque curve up the rev scale, or given the same valve timing a longer stroke will produce more low end torque and peak torque arrives a little sooner.

The valve spring recommendation is stiffer than necessary. With minimum installed height to allow .090/100" coil bind clearance the F-M VS-677 valve springs, which are identical to the '67-up OE 3911068 valve springs, pumpup speed will be at least 6500. Seat force is a little over 80 pounds and about 200 open.

My recommendation is to buy the F-M L-46 cam and I believe it's still in the GMPP catalog since it's still used in the 350/290 HP crate engine, but I'm not sure who actually manufacturers it now for GM. Before they went bankrupt about a decade ago I believe Crane did supply the old OE grinds to GM.

BTW that "L-79 Nostalgia Plus" cam is nowhere near the OE L-79 cam and the manufacturer is hoodwinking customers by equating it to a the real L-79 cam.

Be careful about various cam specs. There are multiple ways to measure and often the full context is not revealed, so comparisons are often apples and oranges.

The L-46 cam, advanced four degrees on a 327, will provide a relatively flat torque curve and linear power curve and a decent idle at 750 with just a slight lope - an excellent combination of low end torque and top end power with a properly configured spark advance map.

There are literally hundreds of different SB cams available in the aftermarket, and you can spend the next year trying to analyze them from published data, and most likely you will just tie yourself up in a knot.

The factory cams are very good and the L-46 is probably "best" due to it's refined lobe dynamics and torque bandwidth for a high performance sports car engine that has the convenience of hydraulic lifters.

Duke

turbodave231

Duke,
Question: I am installing the L-46 cam in a 385 cubic inch engine for my 64.

Would you still advance it 4 degrees so IPOML is at 110? or would you leave it at 114?

My "Cheater" engine is an 870 block with 461 massaged heads and the 365 intake and carb. Scat large journal crank turned down on the mains, scat I beam rods and Icon Forged pistons.

L79flight327

Duke: Thanks for your patience and explaining the why. I have noticed the cam timing is reported in different ways by Crane, Comp, GM and others. I have also noticed that different sources report conflicting information as well. I was racking my brain trying to understand why you kept recommending to advance the L46 cam to 110 IPOML like the L79 when I was staring at the Comp Cams L79 cam card which reports the IPOML (intake center line) as 114 (see attached) . Took some research to figure it out Comp got it wrong. Crane reports it as 110 (attached). I am an engineer as well and really wanted to learn more about valve timing as part of my desire to change the driving experience in my car. I guess I better stick to designing roads and drainage systems. Do you know the difference between mechanical engineers and civil engineers? Mechanical engineers design weapons... civil engineers design targets..

Jackfit

Hi, I had my engine (original L-79 300,000 miles) rebuilt with a Comp Cam x256.....Dyno at 350 HP and 380 lbs torque , 9.5 compression pistons . original rods and crank , intake , carb. That cam or X262 or X 268 with Hydro lifters and stock intake will work really well.

I have put 75,000 miles on the engine with this comb in the last few years....still very happy....good power low and high , max torque at 3,600 rpms...

My car with a M-20 wide ratio and 3.70 rear was able to stay with C-5 and C-6s on European country roads with out a problem...and hit speeds over 110 easy...this is a completely stock car , except for the engine rebuild..well 5 rebuilds....

My point is don't get too extreme....stable idle important.....

Jack

SWCDuke

Assuming the engine has a 3.75" stroke or thereabouts, leave the IPOML at 114 deg. ATDC. (I only recommend advancing it on short stroke engines - 327/302/283) Use a standard (non-adjustable) OE replacement truck roller chain. It's made by Cloyes and sold under a number of different brands. The Cloyes/NAPA part number is C-3023K/103023. The +/- 4 degree adjustable set is C-3023X/103023X, and I think both cost about 30 bucks.

Duke

SWCDuke

It looks like what Comp calls an "L-79" cam is actually ground retarded four degrees from the OE inlet POML. This is a primary reason why I only recommend F-M replacement cams. They are all manufactured to the original GM specs... no monkey business.

I don't know why Crane recommends such stiff springs. As I've said before, careful installed height of the OE springs will yield lifter pump up speed of at least 6500, and with massaged heads a L-79 cam or L-46 cam advanced four degrees will make useable power to the lifter pump up speed on a 327.

If you want to gain more insight about how to design valve timing, search for threads started by me and download and read the "Tale of Two Camshafts" article. It chronicles the design and testing of two camshafts I designed for what I call the "Special 300 HP" configuration about ten years ago.

I've heard that joke about civil versus mechanical engineers before, but it's been awhile, and it made me laugh. I'm of the former type.

Duke

65tripleblack

Exactly. But to make things even worse, the cam is installed 4 degrees retarded, which lowers DCR even further. Advancing the cam increases DCR. You don't want to hear this but the best GM cam for this engine is the 929 (327/300). I don't recommend the Nostalgia Plus cams. First of all, you'll need spring pockets opened and screw in valve studs. More importantly, I don't trust the reliability of an aggressive flat tappet cam. One more thing: today's gas is not "crappy". Today's 93 PON octane is equivalent to about 97 RON from the sixties. Further, the absence of lead is keeping the engine and especially the spark plugs cleaner.

The best things you can do without spending a ton of money. Be aware that you will not be anywhere near 8.0:1 DCR without either replacing the pistons, decking the block and/or milling the heads:

1. Reset the cam timing to 4 degrees advanced.
2. Use the thinnest possible head gaskets that you can find. I believe that steel shim gaskets can still be found with compressed thickness of .018"
3. Program your distributor with the most aggressive spark advance as possible. With your engine's anemic SCR, you can easily use the spark program from the 1964-65 L76/L84 engines.

Use an online calculator to determine the engine's DCR. Ideally, you want a DCR somewhere between a conservative 8.0:1 and an aggressive 8.75:1.
http://cochise.uia.net/pkelley2/DynamicCR.html
A link to the calculator is near the bottom of the page.

Here are some numbers for you, just for purposes of comparison, of how a very healthy 327 should be. These are from an engine that I built about 4 years ago:

Static Comp Ratio (SCR): 11.35:1
Dynamic Comp Ratio (DCR): 8.65:1
Cranking cylinder pressure (dry, WOT, 3 cranks): 225 psi +/_ 5 psi

This engine uses 20 degrees initial advance, with another 15, all in by 2300 RPM, plus 14 degrees vacuum advance. This engine has aluminum heads, runs 160 degree coolant temp, and does not detonate on 93 PON fuel.

GearheadJoe

Do you have any photos that show the size of the rod clearance notche you had to make at the base of the cylinders in that '870 block? And which Scat I-beam rod did you use (Pro Stock or Pro Comp)?

I'm asking because I built my 383 using a 1967 3892657 block that already had the cast-in clearance notches that were added for a 350 stroke. Even so, I had to grind another .050" or so to make the notches clear my Scat Pro Comp rods.

Some people have asked me whether they could use this same rod to make a 383 out of an '870 block, and all I can tell then is that it would involve grinding away more material than I had to remove from my '657 block. I've never talked to anyone who actually did this.

Apparently it worked out for you, so I'm interested in your feedback.

L79flight327

That DCR calculator is very interesting...It will calculate valve events based on LSA, Intake Center Line, and advertised duration to determine the Intake closing point. I plugged in my engine and several of the cams being discussed L46/82, Crane 278H10, Comp 268H, and of course the ISKY cam that is in the car:

L46/82 intake closes at 85 ABDC, the calculator predicts 80 ABDC, Advanced 4 degrees you get 76 with a DCR = 6.5

Crane 278H10 intake closes at 68 ABDC, the calculator predicts 64 ABDC, a DCR = 7.27

Comp 268H intake closes at 60 ABDC the calculator predicts 60 ABDC, a DCR = 7.48

ISKY intake closes at 48 ABDC the calculator predicts 52 ABDC, a DCR = 7.89

Looks like the ISKY cam that is in the car makes the most DCR. Sounds like a cam change will result in a loss of torque but perhaps better idle and vacuum...

SWCDuke

There is no universally accepted "inlet valve closing point" for calculating DCR, so unless the cam data uses the same timing assumptions, you can't compare. If you are using various online DCR calculators, they won't give consistent answers. It's just a rough guideline, not a go/no-go criterion.

Also the DCR calculation has NOTHING to do with LSA or POML. It's based on SCR and inlet valve "closing point" - whatever that is, period, and DCR tells you NOTHING about idle behavior.

You're reading way too much into these calculations.

Duke

65tripleblack

The Isky has the best IVC event based on your SCR compared to the other three cams; however, it uses way too much exhaust duration and too narrow an LSA. So if you're unhappy about the idle quality then you must replace the cam. A cam change, if properly designed, will give you both more torque and better idle quality. You need a cam with short duration, 110-112 degree LSA, roughly 205/215 durations, and, if you use an aftermarket cam, higher lift than GM. If you want a "Safe" cam, then use the GM "929".

DCR is the primary criteria used to determine how much cylinder pressure (torque) is developed in an engine. It is the primary means of determining how much power you're leaving on the table when designing your engine. It is light years more meaningful than what guys call "compression ratio" (Static: SCR) because SCR by itself is absolutely meaningless since SCR must be matched to the camshaft's IVC event. The combination of SCR and IVC event yields DCR. Once that is established, then lift, duration and LSA should be designed as required based on exhaust and intake efficiency, idle quality expected, and RPM range anticipated.

All of that being said, it sounds like your DCR is not too far off the mark. Did you say that this cam is installed 4 degrees retarded? Did your calc run with the cam advanced, retarded?

That Isky is ground with a narrow LSA, and way too much exhaust duration, which is why it has such poor idle quality. If you can't live with the idle quality, then there is nothing you can do short of changing the cam. Based on your needs, the 929 cam will give more torque and a smoother idle as well as being more suited to your current configuration. If you want to take advantage of the aftermarket, then I can recommend one of theirs, either off the shelf, or custom ground. I assume that you don't want to go with a hydraulic roller, and, frankly, I don't think that you need one.

Kerrmudgeon

I used that 350-350 hydraulic cam from GM for years in my 331. I really liked it and it made more power in my opinion than the 327-350 one. BUT, I was running 11.5 to 1 comp. stock pistons.......

65tripleblack

The 962 is a good match for your SCR. It has slightly more lift and duration than the 151 cam.....................sorta' like your avatar.

wesmigletz

Here is a 62 870 Block with a 3.875" stroke Callies crank. IIRC, the rods are SJ oliver.

L79flight327

65 trippleblack:

I am open to suggestions... that is why I have reached out to you guys who have more real world experience with these cars and engines. I have always enjoyed fixing things and like to understand how things work. I have learned a lot about my car over the last 8 years. Unbeknownst to all of you, this forum has taught me a lot including how to tune a Holley, setting timing curves etc.

I am not happy with the idle of my car. It is very very loud and very choppy. It will idle at 750, the whole car shakes and it makes 11 inches of vacuum. It has side pipes, so I picked up some 2.5 exhaust manifolds and bought the "quiet side pipes" . My car is still much louder and choppier than any other side pipe car I have seen. I am in Florida , I see side pipe C2's at the weekly car show all the time. Please don't misunderstand me, I like louder than stock exhaust. I designed custom baffles for my 1984 Nighthawk 700S and I have custom exhaust on my "other 327" my daily 2005 Sierra 1500. I have always suspected the cam that is in my 66 is not appropriate, but until I put a degree wheel on it last week ...I never knew what I had... now I do. I want a car that provides good performance, I want to get shoved back in the seat when put my foot down! I also want a quieter and better idle.The ISKY is responsive and has good torque, but based on what I hear from you guys and Crane and Comp, I have concluded my suspicions were correct...their is a better cam for this car than the ISKY that is in it. So please tell me more about what hydraulic flat tappet cam you think would work well and why.


PS: I have started assembling what I am going to need to swap the cam. Can someone point me to an intake gasket that will fit my GM 3890490 Winters Intake manifold. .All I seem to be finding is a Fel-Pro MS 9617 and that one does not look right to me. Eklers, Covette Central etc list one that does not look right either.

Thanks!

65tripleblack

For your needs, I recommend the GM 327/300 "929" camshaft, and lifters. The lifters must be replaced along with the camshaft.

FelPro 1204 will work for you.

MikeM

[QUOTE=L79flight327;
I am open to suggestions... that is why I have reached out to you guys who have more real world experience with these cars and engines.

I am not happy with the idle of my car. It is very very loud and very choppy.

It has side pipes, so I picked up some 2.5 exhaust manifolds and bought the "quiet side pipes" .

So please tell me more about what hydraulic flat tappet cam you think would work well and why.


Thanks![/QUOTE]


Put the factory grind L 79 cam in it and forget it and you'll be happy. That cam was designed by GM engineers that knew more about what works in a SBC on the street than anyone. And that includes driveability, reliability and performance. I've run the L 82 cam as well but just never liked the way the thing performed. No need for all this aftermarket hocus pocus in your application.

I've never heard aftermarket side pipes that were quiet. Even the GM pipes were noisy with a hot cam in the engine.