ry57pont

Going to order my parts today to assemble the 327. i am going to use the edelbrock e-street aluminum heads and the L-79 cam (intake dur &.050 229 exh @ .050 236) it is the comp cams Nostalgia version (K12-671-4) what are the advantages /disadvantages to using the 1.6 rocker vs the 1.5? any help is greatly appreciated, Thanks!!

Bluestripe67

I think your concern should be relative to piston to valve clearance. Don't the heads come complete? What pistons are are you running? Some of our better engine tech guys may respond for details. Dennis

ry57pont

no, the heads still need rockers, the pistons are flat tops.

MikeM

Go straight to the horse's mouth and ask Edelbrock if their head flow will benefit from the extra lift.

claysmoker

What's the rest of your combo? Intake? Heads? Drivetrain? Exhaust?

I doubt any PV clearance will exist with 1.6, but always check it.

karkrafter

Correct me if I'm wrong...aren't 1.6 rockers really more of a tuning tool? I mean it makes a smaller cam, bigger...


If you want a bigger cam and the mill is apart...why not just put a bigger cam in to begin with?

ry57pont

factory winters aluminum intake, 4 spd and 3.36 rear. 2.5" factory manifolds, side exhaust.

i am not looking for max HP with this combo, but just thought for a couple bucks more maybe i was getting "something for nothing" by installing the higher ratio rockers.

claysmoker

Don't waste any money on 1.6's.

In fact, that cam is going to disappoint you with the drive train you have as the low end won't be great. All you're buying is something that may sound cool and won't be much fun to drive around town.

tbarb

I take it this starts as a 300hp engine. Have you run your specs through a compression ratio calculator. A flat top piston motor with that cam and ??cc heads with a 3.36 gear. Also, have you compared the comp cam specs to the Federal Mogul exact replacement L-79 camshaft.

I think the L-79 is a nice motor but be careful you don't go down the road of $$$ then more $$$

Powershift

I have not been impressed with Comp Cams products and their long term reliability. I see a lot of failures. Even Crane is not immune, but I think is a better product. Consider using one of the "factory" L79 cams from Federal Mogul or similar OEM supplier. FWIW.

Larry

ry57pont

no i have not done any calculations, i have a GTO with a similar setup (but more gear) and it drives OK, but maybe i am not comparing apples to apples. the e-heads are 64cc but i have not done the comp ratio yet. i may have been too concerned about idle than drive ability. maybe i should re-think the cam choice?

another factor is time, if i dont get a motor together by the end of the month, i wont get back to it until fall, so i was trying to build one by internet research. prob not the best way to do it i know.

Pop Chevy

The exhaust manifolds are the choke in the system. No sense putting more in if you can't get it out .

jimh_1962

I have a similar setup using N+L79H cam. I was able to use 1.5 rockers without any clearance issues. Sounds good and pulls fine. Though using 461X heads and performer EPS and Edelbrock 600 CFM carburetor.

Also .030 Speed Pro Hypereutectic flat-top pistons and steel forged crank.

MikeM

A STOCK L-79 cam will work fine with that 3.36 axle with the wide ratio. Still okay with a close ratio transmission.

A STOCK L-79 cam works well with either the flat top or OEM dome pistons.

I have no idea with the hot rod version of that cam like you bought.

The 1.6 ratio rockers will for sure put a little more strain on your valve train.

jimh_1962

http://www.compcams.com/Company/CC/c...?csid=110&sb=2

Intake Exhaust
RPM Range:
1800 to 6200
Valve Lash:
Hyd.

Hyd.
Valve Timing:
0.006
Duration:
276

283
Lobe Separation:
112°
Duration @ .050" Lift:
229

236
Intake Centerline:
108°
Valve Lift:
0.468

0.462
Lobe Lift:
0.312

0.308
Valve Timing @ 0.006


Nostalgia Plus™ Cams are designed to mimic the sound of the great engines of the past while improving performance by applying today’s design techniques. Capture the essence of the factory muscle cars of the '60s & '70s. These cams use lobe profiles that are slightly less aggressive than Xtreme Energy™ profiles but have excellent area under the curve for outstanding power.

63 340HP

The engine models at 350 Hp at 6000 and 350 tq at 4200.

The heads can perform a bit better with more lift, and more dynamic compression.

Flattop pistons will net static compression of about 9.45:1 with zero deck height and a typical 0.047 gasket. If you can get the deck height to get the pistons out of the bore a few thousandths, or use a thinner head gasket, it will help compression. Shoot for .040 to .045 quench. The gain from squeezing the compression is only a few Hp, but the better quench will help cut detonation.

Dynamic compression with the 9.5 static and that cam is only 6.86:1. This is a little low for under 2500 rpm torque, a possible concern at the 65 mph cruise rpm. Adding 1.6 rockers gain about 4 Hp at 6000 rpm, but lose more torque below 2500.

A slightly smaller more modern cam like the 268H gains almost 30 tq at 2500, while losing only about 5 Hp at 6000. The tq gain is from closing the intake valve earlier and the resulting dynamic compression of about 7.11:1. It has a little less overlap with the lobe profile, less lope, but better overall usable power. If you have vacuum accessories the modern cam helps at idle, about 15"g compared to the nostalgia cam at about 12.5"g.

These models are with EA3.2. The hp is likely optimistic. The better low rpm tq prediction with then more modern cam is typically spot on.

Years ago I specified a 350 with the 268H and the owner wanted an Engel version of the L79. He ended up using Rhodes lifters to gain back some tq, running a wide ratio t10 and 3:23 gears. The idle sound may be the decider, as it was in this case.

Good luck.

ry57pont

as i understood it with aluminum heads they are a little more forgiving with detonation due to better heat dissipation, or is it all based around compression? Thanks again for all the great info

JRRHINO

I would like to second this, go with the real deal L79 from F/M and return the other one.

63 340HP

It, detonation resistance, is based on compression and quench. Aluminum cools faster to minimize hot spots that can promote detonation, and in that regard they are more forgiving than iron.

The L76 and L79 cams have low dynamic compression because GM needed to bleed off chamber pressures at low rpm to prevent iron head detonation. They also ran much higher static compression, and tempered detonation with slow spark advance curves. The combination of higher static compression and the long duration cams still placed dynamic compression around 7:1.

Aluminum heads can resist detonation with higher compression, and modern chamber designs can also better handle more compression with today's pump gas. 10:1 static, and 7.5:1 and even 8:1 dynamic compression is reliable with 91 octane pump gas, and good aluminum heads. Dynamic compression improvements develop better combustion and torque, throughout the operation range of an engine, limited by detonation where the aluminum heads help. Not exploiting better static and dynamic compression with aliminum heads is leaving power and economy on the table.

MikeM

I don't know about all this high fallutin' theory and desk top dyno stuff. I just know the OEM L 79 cam will make a big improvement in a 327 with flat top pistons. Certainly more compression is helpful.

I'd also go with the stock OEM L79 cam for reasons driveability, durability and performance over one of these "nostalgia" type cams.

I keep hearing about all this "modern" technology stuff on flat tappet camshofts. What do we know today that we didn't know yesterday that makes any appreciable difference for a street driven car using OEM heads. Even though many use aftermarket that flow much better/differently, cam grinders way back knew how to grind a cam for modified stock or even aftermarket heads.

Well, one thing we know is these cheater cams with stiff valve springs will wear cam lobes, pull rocker studs, float valves into pistons and break other parts along the way if pressed to the limit.

I was where I am describing years ago. You can take it or leave it.