Valve spring shims what's the thickest I can use

[geoffinbc]

Well suit yourself. I know people have had valve float issues with stock cams and stock springs. So be warned. Just because GM uses it to 6000 RPM doesn't mean it is the best way to get there. Springs go along way in valvetrain stability and lifespan. Especially if you like to go wide open often.

It sounds like your are trying to justify not spending a little extra cash. But it will go along way in terms of performance and reliability. You've gone this far, another hundred into the project for new stronger springs sounds like a good investment to me.

[Joseph Upson]

Well suit yourself. I know people have had valve float issues with stock cams and stock springs. So be warned. Just because GM uses it to 6000 RPM doesn't mean it is the best way to get there. Springs go along way in valvetrain stability and lifespan. Especially if you like to go wide open often.

It sounds like your are trying to justify not spending a little extra cash. But it will go along way in terms of performance and reliability. You've gone this far, another hundred into the project for new stronger springs sounds like a good investment to me.

Actually justifying spending more cash under the circumstances where I have parts that may be appropriate for use. It is apparent from my observation that everyone believes the right way to do something is to spend money on assurance without the burden of proof under the assumption you can't go wrong that way. Having done that in the past and realizing thousands of dollars later that spending without planning or justification can be just as bad, I make it a point to evaluate first.

Higher performing springs would be my preference, but having had at least one high performance spring break under average use and no original equipment spring failures, well hopefully you get my point. As mentioned before they are low on the priority list, I have the shims and if they will prove to be beneficial at the moment that would be the best approach.

I'm not aiming for the moon just spring pressure a little above stock which I should get without a problem.

I've also had a high volume oil pump ruin an engine.

One important thing I can say about original GM parts is this, dependability has been much greater for the original parts than for the aftermarket parts that I have purchased over the past 20 yrs.

I do appreciate your input, and although I'm on a budget even If I were rich we might still be having this conversation because of priorities, if I don't need it for my purposes I don't want to buy it. That's how garages are filled because it's just hard to throw away good parts.

[geoffinbc]

Yea I am not a fan of HV pumps either. Even stock pumps provide way more volume than needed and will also feed mild race motors. I have 30 PSI of pressure at idle on SAE 30 in the middle of summer. Really you only need 10PSI. So that there tells you how much the pump is working.

But like I said earlier see what Crane and Comp specs for springs on a cam of similar specs. They both sell 60* camshafts so take a look.

What are your specs anyway?

[Joseph Upson]

Dur. 212 208
Valve lift: .468 .454
Lobe sep 114
Roller cam int -6 BTDC 38 ABDC
Exh 40 BBDC -12 ATDC

I'll look into the cam spec comparison for spring tension, since I'm using twin turbos with a cam that was cut for turbocharging and higher rpm it's likely my redline will be above the 6500 rpm rating. According to Desktop Dyno it's right about 6500 as indicated but the high flow of two turbos might take it higher.

That high volume oil pump nearly sprained my wrist when I primed it with a drill, that's a lot of horsepower being lost over the rpm range.

[Joseph Upson]

The closest comparison I could find was a 4.3L cam with about .040 more lobe lift than my cam, the 3.8L and LSx series cam specs were not listed I guess for competitive reasons they want you to call about those. The spring listed for all the 4.3L cams you could veiw the specs for were double non behive with a max open pressure of 310 at 1.2 open.

A general comparison of the beehive springs showed about a 14lb pressure increase per .050 increase in lift so maybe I'll gain about 12lbs by adding the .050 shim. I calculated about 1.272 open height with my cam so by the 4.3L spring recommendation that would be about 284lbs however the 4.3L has a heavier valve train than the 60 degree V6. I believe the valves and lifters are heavier at least I recall the roller lifters for the 60 degree engine being smaller when I compared them years ago.

Not sure how much spring load savings that would translate into. The valves being splayed also help in reducing the amount of spring tension needed by the amount of sine(angle) times the weight of the valve since it's not being lifted at a 90 degree angle.