Max

I am going to replace my stock LO3 cam this spring. I have read a lot of cam selection articles and even spoken with tech at GMPP and Crane Cams. I have narrowed down my choices to a few. I would like to get the best bang for the buck and the perfect match for my application.

As you can see in my signature my 305 is now carbed with a Holley SA 670. I have also replaced the rear gears which are now 3.73 It also has a very free flowing exhaust.

Which would provide the best bang for the buck with my set up:

LT4 Hot cam kit including 1.6 roller rockers springs etc.
Duration at .050" tappet lift (intake/exhaust) is 218/228; and maximum lift with 1.6 rocker ratio (intake/exhaust) is 525/525. Valve lash is zero/zero and lobe centerline is 112 degrees.
$500 Approx.

LT4 production cam 1996.
Duration at .050" tappet lift (intake/exhaust) is 203/210; and maximum lift with 1.6 rocker ratio (intake/exhaust) is 476/480. Valve lash is zero/zero and lobe centerline is 115 degrees.
Cost for just the cam?

Hydraulic Roller cam for 5.7-liter H.O. 350 ZZ3 & 4 engines. Duration at .050" tappet lift (intake/exhaust) is 208/221
maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 474/501. Valve lash is zero/zero and lobe centerline is 112 degrees.
Cost for just the cam?

Crane Cams PowerMax H-266-2
Hydraulic Lifter Camshafts for Emissions Controlled Vehicles without Computer

Good idle, daily usage, off road, towing, economy, good low and mid range torque and HP, 2400-2800 cruise RPM, 8.5 to 10.0 compression ratio advised. (50 state legal, pre-computer, C.A.R.B. E.O. D-225-18) Basic RPM 2000-5000

Degrees Duration @ .050 Int./Exh. 210 / 216
Degree Lobe Separation 114
Gross Lift Int./Exh. .440 / .454
$260 Approx.

Would it be most cost effective to replace just the cam or is the Hot cam package the best deal and would that cam work well with my set up? Any help in selection will be appreciated.

Cronic3rd

Talk to comp cams. THe have a whole line of roller cams for gen 2 blocks and will be able to recommend a cam for you. a cam master kit runs like 500 bucks for a flat tappet. I'm not sure what they run for a roller design.

Sitting Bull

The LT1 roller cam is the one you want. Get one off eBay for $50. None of the others are right for your engine.

Max

I'm not too worried about low end torque. The car already spins the tires leaving the line and I'm thinking that each of these cams would produce somewhat more torque at idle than the orig. LO3 cam. As long as I don't end up with less torque at idle I'm happy.

What I am really looking for is maximum midrange torque. I want to maximize power output from about 1500 - 5000

I'm not really after high end horsepower because I dont like to run my engine up over 5000 RPM.

The x factor in this case is the stock conveter. I think it kicks in around 1400 RPM. However I understand that the more torque an engine has the higher the stall speed becomes as a result.

Does anyone have experience with these cams and a similar setup?

Sitting Bull

You are wrong thinking those cams won't make low end torque any worse--they will!

Max

What do you think about these for my set up? Lift figures are all based on 1.5 to 1 rocker arm ratio.


LT1 Production Cam 95-97
201 / 208 .447" / .459"

LT 4 Production Cam
203 / 210 .446" / .450"

Crane Powermax Cam 2031
208 / 214 .438" / .452"

Crane Powermax PN 109821
214 / 222 .488" / .509"

five7kid

iTrader: (14)

What heads are we talking about here?

Max

The heads are stock on LO3 305. Cast Iron. That's about all I know about them.

Sitting Bull

Stay away from the Crane cam, it is too big.

But you MUST get a set of 081, 416 or 610 heads and port and polish them according to the instructions at the end of my sig. Why? Because those L03 heads are swirl port and have cast-in restrictions. These other three castings don't have the casting restrictions and can be made to flow like Vortecs. It will require some effort on your part but ALL really good things do, don't they?

And they can be used on a 350 when you're tired of the 305.

The LT1 cam is the best choice by far for a couple of reasons.

- You won't have to machine the spring seats in order to create enough clearance for its lift. That means you save even more money.

- It can be had for a measely $50.

xxwarrior36xx

I have to agree, that is too much lift for your 305. If you haven't ported the heads ALOT you won't get the right flow. I would go with the lt4 cam personnaly. That seems just about right and will rev to about 6000 which your internals should be able to handle. THis is just my opinion

Sitting Bull

I think that what he has quoted as specs for an LT4 cam are actually just a variation of the LT1 cam. There are at least three diifferent grinds of LT1 cam but they are all very similar.

The only LT4 cams I've seen have lift in the .500 range, which is just too much for his engine.

five7kid

iTrader: (14)

The reason I asked: This discussion is silly if you're sticking with those heads. Any of those cams will be a waste if the heads aren't replaced. Porting won't help.

Vader

I don't think the net lift is a biggest factor in killing the low end torque, but the necessarily longer duration that goes with those lifts. Keeping a wider LSA and minimizing overlap will usually provide teh better low RPM torque.

The Bull is right. A cam improvement isn't a bad idea at all, but those heads are already a restriction. A better cam probably won't provide the kind of improvements you anticipate until you do something about the ports and valve sizes. You will probably get a little betterflow and cylinder charging with a decent cam, but you'll get a lot more overall with a better pair of heads - even factory castings. You could theoretically weld up and port those castings, but your results wouldn't justify the effort.

Max

Thanks for the help so far.

The LT4 cam specs I showed you were calculated using a 1.5 to 1 rocker ratio instead of the 1.6 to 1 rocker ratio that they are normally based on. That's why the figures are differant than what you usually see listed for the LT4 cam. I want to reuse as much of my current valve train componentry as possible to keep the cost down. Which means I would be re-using the stock 1.5 to 1 ratio rockers arms.

It sounds like you guys argee that the duration of LT1 or LT4 cams would be a good match for my combination. It also sounds like you are more concerned about the high lift that the LT4 cam possesses. Would you expect a loss in efficiency because of the bore size of the 305 or the design of the stock LO3 heads or something? I thought as long as the intake duration and overlap was not too much for your combination that the more lift you produce the more power you get.

Is there a law of diminishing returns with respect to the amount lift generated in an application like mine?

Sitting Bull

Like Vader says, it is not so much the lift as it is the increased duration the cam lobe must have built in in order provide it. Moreover, when you get above about .460 lift, you must have the heads machined for taller valve springs. That just makes cams with .470 or higher lift a greater expense.

The problem with LO3 heads are cast-in swirl vanes in the pockets under the valves, and a push rod intrusion into the intake runner. This restricts the flow too much to fixed with a grinder.

Thus we recommend you get a set of 305 castings ending in 081, 416 or 601, and work from there.