InfinityOlds

Hey Guys,

I'm in the middle of working over the top end of the motor right now and could use some advice on valve springs. I've still got the factory originals and I need to replace the stem seals. The engine is a 1965 low-comp (9:1). The current springs are the originals - so they're due for replacement regardless.

I'm planning to install a turbo next year and I've seen mixed information on whether I should upgrade the valve springs or stick with stock. Some resources I've seen say that the pressure from the turbo shouldn't impact the valve springs, but I'm not sure I buy that. I'm planning to run up to 10 lbs of boost.

From what I can tell the stock springs are ~75-80lbs at the seat. It looks like the Edelbrock ones are essentially stock replacement (~80 lbs).

I also came across these three options, all comp cams which I've seen highly recommended:
https://www.compcams.com/single-oute...1-080-i-d.html
http://www.northernautoparts.com/part/cm-995-16
https://www.summitracing.com/parts/cca-994-16

The first option seems a little too large in terms of OD but it says they're for Olds... so I'm guessing I'd have to run those with new larger retainers.
The other two options seem like overkill for the factory cam.

Any thoughts/recommendations?

I did come across this rule of thumb calculation people use for blown small blocks: run springs with a seat value of the NA recommendation + valve area * boost pressure; so in the case of an Olds that would work out to 76+27.6 at 10 lbs, or about 105lbs. That would point me towards the first option I think...

OLDSter Ralph

We know what year and compression ratio, but not engine size (330 ? 425 ?). I would think you could use valve springs for a W-30 and shim to proper height and be over 105 pounds of spring pressure on the seat. Cam makers will have stuff. I am not a fan of anything CompCams and I would look at Lunati or others. Others will chime in on the subject.
........Just my two cents worth.

InfinityOlds

Good catch on the motor was posting in small blocks but didn't think to mention 330.

I suppose I could use shims on factory replacement springs, that could be a bit cheaper of a route.

Thanks for the Lunati recommendation I'll check out what they offer.

InfinityOlds

Looks like these Lunatis might fit the bill, and are about the right size so I can re-use the stock retainers so it'll only be twice the cost ($110 vs $60):
A little more force at the seat than I was speccing but I suppose that leaves me free to pursue more boost if I want to.

Not sure many will chime in! The Olds motors don't seem get a ton of blown love because of parts limitations and N/A power capacity. If I had a 67 or later I'd be doing a full tear down and high comp N/A build up, I figure this will be a bit different and fun. I appreciate the response!

OLDSter Ralph

You can just shim to increase to any spring pressure, you have to make sure you won't get coil bind when the valve is open at full lift. Use the "installed height" for the springs and cam you are using. People use different cam companies. Cutlassefi on this site might be a good source.

InfinityOlds

Duplicate post

InfinityOlds

Roger that. It's difficult to find factory specs on the originals but everything I've seen seems to indicate a set height of 1.67, and coil bind around 1.10. Looks like I have some calculations ahead of me. From early napkin math with stock springs I think I'd need a .15" shim to get to 105# vs stock 80, taking me pretty close to the bind limit, so I'm thinking upgrading is the good way to go rather than shimming that close to the bind.

OD it looks like 1.425-1.49 fit, although I can't seem to find the stock OD. I guess I'll need to head out to the garage and measure.

Seems like OEM replacements run about 1.44" & edelbrocks are smaller at 1.425. Anything double coil I'll need new retainers.

OLDSter Ralph

1.67" does sound like the installed height for the Oldsmobile W-30 springs. The "80 pound" springs are NOT the same springs as W-30 springs, so DON'T shim themto 105 pounds. There could also be a difference in the coil spring wire size that increases the pressure. Shim whatever springs you buy to the manufacturers installed height. PM Cutlassefi on this site, he will get you the springs you need.

InfinityOlds

Yeah I'm leaning towards getting the W-31 repro springs... at ~$105 for a set. Sent Clutlassefi a PM & maybe he'll steer me another direction, hate to bug him on valve springs. This is a bit of a trial mule; if it goes well I'll do a 350 build with aluminum heads and a custom turbo cam, and he's the guy I'd go to for cutting that since he cuts cams for all the Olds, even the 45 degree 330s...

Also, fwiw I got a measurement of 1.425" for the OD with my calipers on the low-comp 330. From what I can find online the stock springs for a low comp are 76-80 at the seat from factory, and W-31 are 120# at seat, I don't know about diameter but I don't think the valve seats are bigger.

That's the best my searching could pull up.