Is this the correct book for small blocks?

rumblefish360 said

@Dale Davies

Since your quoting me….

Paragraphs are an excellent idea. ;)


Why? Making use of an LA cam in a Magnum is an upgrade in .1 already which should have you seriously reconsidering the exact cam specs being used. Going to a 1.7 rocker further exaggerates the issue.

To bring in one more item, the total lift of what ever the value may be, at what point does the head stop or stall at flowing air?



This is not exactly true depending on the valve lift.
Any cam change should have fresh new springs to match what’s the valve is lifted at.

Absolutely, LS not being absolute. OAL valve length should be considered carefully.

Dumb move using used valve springs. New ones are cheap and fresh OOTB

And your mentioning used valve springs, retainers, locks and valves from a junkyard?

A worthy investment for their accurate ratio over LA rockers.
Has anyone tested Magnum rockers?
How much power is the rocker worth even at the same ratio?
How much power is the added ratio?
Isn’t it easier to get a cam ground at the desired lift rather than exploit it via a rocker ratio?
A Cam intensity is increased with a change in rocker ratio. Is there not a lobe available to match or exceed a rocker change?
At what point is the valve opening speed to much or of no more benefit?

What size are Magnum valves stems?

Why do LS valves wear less and again you’re buying cheap used parts over fresh springs retainers and locks? Saving money at what other expense?

Reshaping the port floor is a bad idea? No laying it back?

A quite from his second post FWIW


As I stated above, the post suggestions will do the trick.
Zero need for anything above.

Thanks

Click to expand...

Yes, I did think that would get someone excited.
1: Upgrade rockers. The idea with this is to gain a bit of lift without having to replace the cam.
2: may... spring upgrade. The reason I stated MAY require a spring upgrade is that the stock springs may be adequate, but should be verified.
3: LS valve springs. The idea is to compare the stock spring installed height and lift before coil bind and compare to the LS beehive springs.
4: used springs. A low mileage Chev will most likely have good springs in it. As any time you are doing repair or modification on your vehicle, the parts must be inspected. Used springs from a low mileage salvage vehicle will be fine provided they pass inspection.
5: used springs, retainers and keepers. Again inspection of the parts. If no damage or wear they should be perfectly acceptable to use. A bunch of this is low buck performance. Most of us have our budgets pinched more so these days than previously.
6: roller rockers with higher ratio. Semi inexpensive with only the valve covers requiring removal. Now valve to piston clearance at 10° BTDC for the exhaust and 10° ATDC for the intake must be checked. Depends on which ratio is chosen and how much the calculated increase in lift they will provide. About 10° BTDC and ATDC is close to the point of closest approach of the piston and valves.
7: Magnum valve stems. I do not know for certain what the Magnum valve stem diameter is. The guys involved with UTG Mission Impossible were talking about the LA valves being heavy with 3/8" valve stems. SBC and SBF are 11/32" except the 221 and 260 SBF which had 5/16" stems, but much smaller valve head diameters. DV measured a used 318 LA intake valve at 118g. My used 289 intake valve that had been ground once is 113g. A new Melling 1.9 LS intake valve is 96g.
8: LS valve wear. This is according to DV who has a lot of experience with cylinder heads. He shows a used valve they plan to use in Mission Impossible, bigger head diameter and lower weight.
9: port floor generally a dead area. Yes some contouring can help in the right place. Short side radius is the big one on that topic. Outside that the port floor will give minimal gain and can actually lose flow. Generally a bit of filling on the port floor reduces cross sectional area and moves airflow up into the active area. This increases flow speed and port energy. That is getting a bit past quick cleanup and bowl work for inexpensive and quick performance boost.

There are things that can be done inexpensively on a budget for a street cruizer and then there is the step up a notch or two to more bracket or race modifications.
To replace the cam will generally require the removal of the radiator and possibly evac and recharge the air conditioning to remove the condenser. All I relate can be done without that.