fotyfobravo

Does anyone have complete CAM specs for: ???

70 LS5 / 454

74 LS4 / 454

Reason I ask......I just rebuilt my 74 from the crank up....everything!
I used a new Comp XE268h and between "the wife" and the AUTO transmission.....I CANNOT get it to idle smooth enough to please them both. I expected a "slightly rough" idle......it is just too rough.

Thinking about going with a Stock GM 70 model or the 74 model camshaft.

HELP !

BigBlockk

Well the '70 LS5 was 214/218 degrees duration on the intake/exhaust and .461/.480 inch on the lift respectively. Lobe centers were up there to get a smooth idle. Something like 115 degrees.

Crane makes blueprinted muscle car camshafts. These are all the original specs but with modern ramp rates.

BigBlockk

Later.....

TheSkunkWorks

BigBlockk has the lift specs correct for that '70-72 LS-5 cam # 3883986.
"Advertised" duration @ 0.008" lobe lift is 268 I / 274 E.
According to the valve timing events: ILCA 114*, LSA 115.5*, Adv 1.5*.

Sorry, don't have the specs on the other one, but it's the '73-74 454 hydraulic # 353040.

BigBlockk

Sorry about that. I should have put 214/218@.050" lift.

This place may be of some help.

http://www.geocities.com/MotorCity/D...00/cmspec.html

BigBlockk

Later.....

FRSTR90

I've got a 75' C20 454... I believe they were the LS4's. If I am correct that it is an LS4, its not a bad set up. The nature of the engine is pretty smooth. Has plenty of torque in 3/4 ton truck and will easily light the tires. I've always wondered how they were in a vette!

The only problem with the engine is that it pretty much falls flat on its face after around 4000-4500RPMs. As of right now, the truck has around 14,000 original miles and is unmolested. I think with a good set of heads, headers, intake, and carb, the engine would be a great compromise between smoothness and performance.

HamadUP

I got the same 268H cam in my '71 LS5 and the idle is not that rough, just slightly more than the stock cam, I set the idle speed to 800RPM and it seems the TH400 is OK with that. If yours is too rough then there may be a problem of some other sort.

Ganey

Ls-5 214/218 @ .050 .461/.480 115 Ls

Ls-4 210/210 @ .050 .440/.440 115 Ls

akfox1

How much advance are you running? Check the timing first, as this should not be too rough.

mayberg

Concentrate on the auto - the wife will come around.

73 LS-4

As far as an Ls-4 in a vette goes, they run ok in stock form, nothing overly impressive. They won't pull much over 5k with a stock cam. they idle well and are very docile on the street(read easy to drive). They do make a lot of bottom end torque which makes them fun to drive around town with. In fact if you drive both my 69 and my 73 around town without really getting on either one of them, you would assume the 73 was a faster car. It's actually quite the contrary however. Once the bigger cam and ported heads with bigger valves come into play on the 69 it runs all over my 73. Don't get me wrong the LS-4 can be made to run well with bolt ons and some good tuning, more then one c5 has been outrun by my slow vette. The 73's actually have argueably(sp?) the best large oval port heads as far as flow numbers(049's), they just have the smaller valves, so they don't take advantage of it.


Pat Kunz

fotyfobravo

Stock setting calls for 10' BTDC.

I worked on it tonight and got some improvement!

Currently set at 18' at idle with the vacuum plugged.
Shows 35' at 2800 rpm - vacuum plugged.
Looks like about 50' total timimg at 2800 rpm with vacuum hooked up.
I have switched to the (1765?) vacuum advance can ... as it only shows 11 - 12 inches vacuum at idle.

Keep any suggestions coming.....still learning some here.