wallifishrmn

What was the duration on the stock 71 LT-1 cam? Did the Lt-1's come with a 30/30 cam? If not which vets did. How much more radical is the 30/30 versus what was in the LT-1 if they didn't come with a 30/30 cam. What is the advantage of the 30/30 cam? I don't know much about cams so any info is appreciated.

Thanks

OzzyTom

I'm not familiar with the 30/30 cam you refer to...
Here's a list of small block cam specs though....

http://www.geocities.com/MotorCity/D...ec.html?200720

70-72 350 LT1 mech p/n 3972178
242 / 254 @ 0.050 with 0.458" and 0.485" lift I/E respectively

Gordonm

There has been a lot of development in cams since the late 60s and early 70s. I would not run one of these older style cams. The newer ones will provide more power and torque over the older style cams. They were long duration and low lift cams. The modern ones are shorter duration with higher lift and more aggrssive ramps for better performance.

OzzyTom

Another issue you should be aware of, if not already.....
zinc/phosphorous content in oil available now has been reduced dramatically to help reduce emissions (reduced Zn/Ph prolongs life of catalytic converters).

However, Zn/Ph is an essential lubricant for metal to metal contact surfaces, especially the high load interface between cam lobe and lifter. With higher performance cams, with increased ramp rate and lift and more spring tension, the lack of Zn/Ph can lead to premature wear.... Lots of tales of woe regarding wiped cam lobes.

This is why all new car engines and many guys rebuilding older performance engines now fit a roller cam... the roller lifter rides over the cam lobe with minimal frictional load, and even allows much more aggressive ramp rates to get the valve open and held at higher lift for a longer duration. This provides a very noticeable increase in torque and power without sacrificing driveability or endurance.

Also, it is essential that you match your cam with the rest of your motor components: Heads, compression ratio, intake manifold and exhaust system all need to be taken into consideration in selecting the ideal cam for the desired use of your car.

69autoXr

The LT-1 cam is not the 30-30 cam. The "30-30" refers to the lash settings of the cam, but if I remember correctly (can't access the geocities page at work), the 30-30 cam was used in the solid lifter 327's in 63-65 and also is the 302 Z-28 cam. I could be wrong though, like I said I can't get to the page to see the specs right now.

30-30 had more intake duration and lift, and I think tighter lobe separation. It was more of a high-rpm cam, even more so than LT-1, for the shorter stroke engines. I would guess that the duration was shortened for LT-1 to go along with the greater displacement and make more low-end torque.

v2racing

Crane used to make a copy of the 30/30 cam. They called them there B;ueprint Muscle Car series and were supposed to be exact copies. It had 256 duration@.050 and 485 lift. It was used in the 365 and 375 horse 327's, the Z28 302, and according to them and all I have ever read the 1970 LT1. Comp has a replacement cam too but it's specs are different. 246 and .489. They call for it in the LT1 also.

Lobe center from Crane was 114 and is what I remember it being but geocities says 112. They also call out a different cam for the LT1. I don't know for sure who's right.

We use to use the original 30/30 cam a lot in small blocks we built in when I was in high school in the late 60's and very early 70's (71). It used to cost $39 with lifters retail from the Chevy dealer.

gkull

People who are stuck in the 60's think that old hot rod crap is great.

I owned and drove those cars when they were still new. I just sold my 67 Charger R/T 440 magnum a few years ago. Even mildly hot rodded but very stock appearing was a toad compared to my 434 small block vette.

v2racing

I couldn't agree more with the fact that performance parts have come a long way. I have often said that people remember the old muscle cars as being much faster than they were. I worked at a muscle car lot in 72 and 73 and I drove about everything that was ever built back then and I am pretty sure nothing I drove or owned would keep up with my 80 with it's 406 in it.

I might add they felt very powerful because they handled so bad and their tires were junk, not to mention they wouldn't stop. It made them a handful to drive. In my racing, record runs I made were uneventful easy rides and didn't feel that fast. It was just the oposite for the old musclecars.

69autoXr

Crane made both the 30-30 and LT-1 cams in the Blueprint series. They were number 967251 and 969551 respectively.

v2racing

I am corrected!

larrywalk

Having run both the 30-30 and the LT1 cams way back when, I also degreed both cams, recording lift every 10 degrees throughout their rotation and plotted the results...

Comparing the two, the exhaust lobes were virtually identical, however, the intake lobe on the LT1 was shorter by 10 deg on the opening side, but had virtually the same closing profile as the 30-30 cam, and had the SAME CLOSING point as the 30-30. Because the intake lobe of the LT1 cam was now smaller than the 30-30, there was less overlap effectively increasing the lobe separation angle by 2.5 degrees to 116.5 from 114 degrees. This had the effect of making the LT1 cam nearly as lazy at low to mid-range rpm as the 30-30 cam due to the late closing of the intake, but not being as strong above 3,500 rpm due to the shorter duration and lower lift, even with the larger displacement of the 350 LT1.

Currently in my 327 L76 at 11.1:1 CR, I'm running an Isky cam (with 30-30 lash), having the same lift and duration as GM's 30-30, but with a 108 degree lobe separation angle. The overall performance is notably better, but it's not usable below 2,000 rpm for general driving. Idle quality and economy suffer a bit, but idle sound quality is great!

To do it again, I'd pick another solid lifter cam having a shorter intake duration of approximately 244/254 degrees, but ground on 108 or 110 lsa, NOT the wide 114 or 116.5 lsa of the stock cams which hurt mid-range torque.

69autoXr

I think the LT-1 number was discontinued at some point though, as the catalog pdf I have from Crane only lists the Z-28 number.