Crane made a cam #967601 which was a blueprint cam for a mid 60's 327 engine that was rated at 350 HP, i.e., more HP than cubic inches displacement. Specs are below. I note one main difference between the 967601 and the LT1 stock cam is that the 967601 has int/exh duration of 222/222 whereas stock LT1 cam is 279/276 int/exh.

Seems obvious that going to shorter duration cam might make more HP, lift is about same for 967601 v. stock LT1 cam. What's wrong with that proposition ?

CRANE 967601:

Camshaft, Hydraulic Flat Tappet, Duration 222/222 at 0.50, Lift .447/.447, Chevy, Small Block, Each --- ** Cam Style: Hydraulic monotonous tappet ** Basic Operating RPM Range: 2,200-5,200 ** Intake Duration at 050 in Lift: 222 ** Exhaust Duration at 050 in Lift: 222 ** Duration at 050 in Lift: 222 int./222 exh. ** Intake Valve Lift in company with Factory Rocker Arm Ratio: 0.447 in. ** Exhaust Valve Lift by means of Factory Rocker Arm Ratio: 0.447 in. ** Valve Lift along with Factory Rocker Arm Ratio: 0.447 int./0.447 exh. raise ** Lobe Separation (degrees): 114 ** Intake Valve Lash: 0.000 in. ** Exhaust Valve Lash: 0.000 in. ** Computer Controlled Compatible: No ** Grind Number: 3863151 ** Quantity: Sold singly. ** Notes: Meets minute 1-A since pilot applications.

 

You're getting caught up in the numbers game. You're correct that the 327/350 cam has 222/222 dur., .447/.447 lift. This is all at .050 tappet lift. And, as you noted, is a hydraulic flat tappet cam. In reality, the 327/350 cam is around 306/306 duration at .006 lift

The LT1 cam you mention may have the numbers you quote, but not at .050 roller lift. Remember this is a hydraulic roller cam. The .050 #'s for the LT1 are closer to 203/210 duration, I'm not sure of the actual lift #'s.

I'm not sure what brought up this comparison, if you have an LTx car, don't swap these cams. The 327/350 cam is nearly 50 years old in design and reflects the technology of its' time. There are many other grinds that would benefit you, some of those from Crane, as well.

 

I totally agree!

Jake

 

Thanks alot, I'm still learning after all these years.

You're seemingly suggesting that the cam in my 1993's stock LT1 is a roller cam. That's good news if true, let me go look at the GM service manuals I have - if I check a diagram showing the lifters, that ought to answer the question.

 

It was noticing that the 65 327's had more HP than cubic inches, whereas the LT1 is a 350 but only puts out 30HP. I figured the cam may have had something to do with it, since the 2.02 camel humper heads were used on other engines having less than one HP per cube.

Stock LT1 intakes are 1.94's, pretty close to 2.02's, so I don't think it was heads alone that was responsible for the more HP than cubes in the 65's.

If they were getting more HP than cubes with a stock engine 40 years ago in a N/A engine with standard cooling, he ! !, I should be able to get more HP than cubes too , especially with the reverse cooling.

 

This info you're going by is somewhat correct. The main difference being that they measure horsepower differently now than what they did in the 60's. Case in point, GM has a 350ci/ 290 hp crate engine
that uses a 222/222 @.050 dur., hydraulic flat tappet cam that runs about .450-.460 lift. This Cam is pretty much the L82 cam from the 70's and is equally out of date, but if you look at this, this crate engine is a 350 (larger than the 327) and puts out 290hp(compare to 350 rating for the 327). I'm pretty sure that by today's methods, the 327/350 would be more like 327/260. If you were to lower the 327 compression to equal the 350, I'm certain the horsepower would go down even more.

And there's a reason they made the LTx heads and stopped using the old "dubbl-humps". The LTx's are better. Just as the LSx heads are more advanced than the LTx's.
Hope this helps.

 

Yes, your engine came with a roller camshaft. The advances made in camshaft design has dramatically improved since the mid-sixties.

Unless you're building an all original engine, steer clear of the earlier cams. Much better cams are readily available.

One other point, No, shorter duration cams don't make more horsepower. There are a lot of variables involved here, but, generally speaking, a shorter duration cam keeps torque strong down low in the RPM band at the cost of higher RPM horsepower.

As a general rule, longer duration cams do just the opposite, they move the torque curve up the band and make better high RPM horsepower but at the cost of off-idle throttle response and low RPM torque.

Torque's what you feel when you're pushed back in your seat as you hit the throttle. Horsepower, on the other hand, is a mathematical calculation determined by torque and RPM.

Jake

 

Thanks a bunch guys. Roller rockers make even more sense for the LT1 since it has a factory roller cam. I'm thinking gm# 12370839. Spring change is in order too, need to find a good quality tool for that, the one I currently have is for when the heads are off.

Bob is right above about the compression, that's a major factor. Increasing valve lift a little with the 1.6's should get more air in there, giving a higher dynamic comp ratio, just how much though can only be a guess but even a tenth of a point would probably be meaningful. Need to max out the volumetric efficiency on the intake side. I've already got a freeflowing intake duct/box, my eye is on the TB lately, want to find a suitable single butterfly that maybe all I need to do is fabricate an adapter plate for the plenum for. The ones on the GM Ramjets look nice, need a junker to toy with, to see if I can get the TPS, linkage etc. correct. Or maybe I'll just leave it be, but the thought is there...