71OldscutlassS

Hello everyone!

I want to replace the Valve Springs on my sbo 350 with #7 heads. Currently just with Stock cam.

Which is a good set to use?

Edelbrock 5812?

Rockauto is listing some Melling Springs?

maybe a good to replace the valve seals too?

I red that there are different styles of seals, rubber or nylon.

I bet, the Springs have never been replaced and im tired of valve floating close to 5000 rpm.

Thanks for some help

olds 307 and 403

Pretty sure you are just making noise at 5000 rpm with a stock cam. Are you planning on swapping cams in the near future? I would think the Edelbrock springs would work fine with a mild cam.

71OldscutlassS

For sure, i know there is not much output at 5000 rpm with stock cam. I just want to get rid of that valce floating and i think its no mistake to replace 50 year old pretty sure worn springs.

in near future, my plan is to rebuild my current engine or get another olds 350 to rebuild.

but till this will happen, i will drive this engine on.

Since that valve springs arent that expensive, i think its worth it and cant be wrong to replace them.

OLDSter Ralph

Be sure to make sure they are shimmed to the correct height.

71OldscutlassS

Why do i have to shim something? Isnt out there a set which fits without shimming?

Does somebody know the specs of the stock valve springs for 1971 #7 heads?

I just hear that the #7A Heads on the exhaust valves have to be shimmed when the rotating spring retainer are replaced with solid retainers because the arent that high as the rotatibg retainers (valve pocket in the heads are deeper?)

OLDSter Ralph

Due to manufacturing tolerances, valve springs may not be at the spring pressure on the seat, which translates to open valve spring pressure not being high enough to keep valves from floating at 5,000 RPM. I would think the CSM would show what installed height that stock valve springs should be.

BillK

71,
I looked in three different sources that I have and all three show the valve spring pressure for a 71 350 to be 180-194 lbs at 1.270" That is also what Melling shows for their spring parts number VS720 The installed hgt is shown as 1.670"

71OldscutlassS

Hello everyone,

Today, i was able to install my new valve springs (Melling VS-720) in my #heads..

WOW!! What a difference!! The car runs very good now!

At WOT, its pulls straight to the shift point and theres no valve floating anymore!

Probably the best ~25 bucks i ever spent in this car 😃

what i learned during the installation:

the new VS-720 springs were a bit higher (1 millimeter, sorry for metric) than the old springs, so this tells me that theyre lost their strenght over the time of nearly 50 years and are worn.

The #7 heads use different spring retainers on intake and exhaust valve. The intake valve has a retainer which is able to spin, the exhaust valve has a solid retainer. Since the spinning intake retainer is a bit higher than the exhaust retainer, the valve pocket in the head of the intake spring is a bit deeper, so both springs have the same size. And i recognized that the exhaust valve springs have a second (damper?) Spring inside, the intake valve springs haven't. I re-used them with the new springs.

Can someone explain to me why the intake valve has a spinning retainer and the exhaust valve a solid one? And why the exhaust springs have this second damper spring and the intake springs not?

Thank you for some answers

Greeting from Austria

Bernhard

wrong thread sorry

olds 307 and 403

It was to increase valve and seat life, I believe. Later heads had them on both sides. Glad those cheap springs worked so well. I wasn't sure if different retainers needed to be used. This confirms these heads have different depth spring pockets.

71OldscutlassS

Ok, my valve float problem on my stock 71 350 is back since some time.

sometimes it appears @ 4900 rpm, sometimes at 5000 rpm.

I already changes the stock valve springs to Melling VS720's. This cure the problem for some time.

Im quite done with my knowledge. For my understanding, stock replacement springs should be good enough for stock cam/valve train.

Are the melling springs maybe Junk? Maybe theyre getting weak very fast?

Specs of Mellings VS720 are:

1.670 installed height with 80 lbs.
1.270 open height with 187 lbs.

Which are the same specs as the 71 CSM says.

Installed height is correct.

I have spring rotators only on the Intake valve and dampers (if i remember correctly) only on the exh. Valves.

what would you recommend to do? I cant really find other "stock replacement" springs with correct specs than these mellings, and since im not satisfied with them, i will not purchase them again.

im even not a valvetrain expert, so i dont know if i could use stronger springs with stock cam and valvetrain. On this engine, i want to keep everything stock, so i want to do no machining to heads.

I also have no comparison to another stock 71 350 sbo, so i dont know if its normal to have floating valves around ~5000 rpm.

engine is running very powerful (for a stock 350) till that point, i can best describe it as a mechanical scattering noise and sometimes backfiring through the carb until i let off the pedal. Right after lowering rpms its running normal again. So i guess it has to be valve floating.

so, i guess that im in need of some different (maybe stronger?) Valve springs.

Thanks for all thoughts about this problem!