Hi Gang....I have 69 350/300 base that I'm doing the valve guide seals in. The heads are on the motor and in the engine bay. I found a spring oil shield that was cracked and decided to replace the valve springs as so many have when they get to this stage. The motor has 27k original miles. The original upper valve seals have disintegrated and the lower umbrellas are brittle. I'd like to replace those with positive stop seals.
My question is should I just replace my springs with a stock replacement and matching retainer...getting rid of the stock retainers....or go to a stiffer spring? I've read that going a step up to the z28 spring or the 350hp spring can be an option but I'm wondering if there's any real benefit and if it affects the valve train at all. Thank you, Brian.

 

Keep it stock there is no power gains

 

Thank you sig…

 

The only reason to go to stiffer springs is to eliminate valve "float" where the valves aren't closing quickly enough at high rpms. Everything has a downside and in this case it's that the Z springs will put a lot more pressure on the rockers, push rods, lifters, and camshaft lobes. Camshafts have a recommended spring pressure in the specs: using the lightest spring rate for the materials taking into account the lobe shapes so that the valve will close at the expected RPMs. When you start using something outside the specs you decrease performance (w/lighter springs) or increase wear (w/heavier springs).

 

GM Parts Catalog circa 1983. All small blocks from 1967 to 1972 used part #3911068 valve spring. That includes 302's and LT1's. So, just use the stock valve spring for your 1969 350. I believe the factory tachometer red line for those engines is 6500 RPM.

 

OP
seems, in Your situation, a stiffer-stronger spring will not benefit your use; but will hasten wear throughout valvetrain. Particularly hastening wear at potentially trouble-prone interface between cam lobe & lifter face.

? by 'stiff umbrella' do you mean a thin rubber cup or cone that clasps onto valve stem itself, while positioned just below retainer; but also rides stem up-down as valve opens-closes" AND that it does Not clasp onto top of head's valve guide ? OR a rubber seal wth a small spring around seal's circumference; all of which intended to firmly clasp onto top of head's valve guide ?

If YES, I do not recall GM installing Either of those as OE in base ZQ8 350/300; IIRC, GM installed Only the square-sided O-rings on those motors. Quite true umbrellas/shedders can be & are retrofitted.

A direct replacement OE equivalent spring available from Many sources for very little money. FYI: For reference purposes, the OE GM Installed Height typically 1.700" and spring (closed) seat pressure about 80 psi.
Do Not skimp on valvetrain Quality ! You can download catalogs from Many suppliers such as Melling which details virtually all specs for Hundreds of different springs for almost any make and model
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Direct Replacement Spring (X=with damper)
Melling P/N RV-880-X (very inexpensive)
1.700" IH, ~ 80 psi at IH aka seat pressure
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Popular, 1'st step up, hi-po, so-called 'Z28' drop-in spring
Melling P/N RV-943-X (relatively inexpensive)
1.700" IH, ~110 psi at IH aka seat pressure
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suggest do Not attempt to band-aid badly-worn valve guides / valve stems with Teflon-lipped seals of any design. If stems demonstrate any serious wobble, you'll need to ask your local auto machine shop if they can install K-Liner bronze thin-wall liners (or equivalent liners); many can, others don't have the tooling. The K-Liner course is Both cost-effective and highly-effective. So, if you already have lotsa stem wobble, but then shove stronger springs onto that, it'll only get worse and that much quicker.
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Once you truly resolve any valve seal/valve guide wear, your valvetrain can benefit by scrapping the heavy stamped steel umbrellas and any heavy valve rotators the stamped umbrellas are often topped with.

 

Thank you gentlemen.
I’ve decided to go with the near stock Edelbrock spring kit and umbrella seals along with rubber rings.
Thank you for your input. Especially part numbers. Melling…what a great source. The car runs great as is and doesn’t see very high rpm for extended periods so it’s definitely smart to keep it that way.

 

Edelbrock P/N 5802 IS stock, IS direct equivalent to OE 80 psi spring. Same as RV880

Next step up is Edelbrock P/N 5803 and that's same as a 'Z28' spring, Same as RV943, and at 110 psi on seat, it is Thirty-Seven Percent More stiff/stronger than stock OE spring

Doubt 5803 offers you any practical-usable benefit; although will create more pressure and stress on lobes & lifter faces. Probably ain't gonna accelerate diddly; except cam wear.

*bet dollars to donuts Edelbrock ain't in the spring manufacturing biz.