2 sets of heads and once decision.

[BeepBeepRR]

I recently bought a set of heads from another member here in a package deal

Both sets of heads appear to have been rebuilt and both are very clean heads. I was measuring the valve springs with my micrometer. And the set I recently got have bigger valve springs but dont know if they are stock. Looking at them vs my 516 heads they are larger in diameter also they have the inner dampner. I have to install a cam anyhow and was wondering which set of heads you guys would use? but I think the 346 heads and springs would be better for a better cam than stock.. Am I right or wrong? edited.... poster corrected me. They are not both closed chamber... Only the 516 heads.

346 heads springs measure 39.23

516 heads springs measure 35.72 mm

 

[Demonic]

More like a inner damper, vs a true dual spring. Hard to fully tell without spring pressures and installed height. But definitely better than the small ones.

 

[33 IMP]

346 heads are closed chamber? Since when? I've never seen any.

 

[BeepBeepRR]

346 heads are closed chamber? Since when? I've never seen any.

My mistake... I, for some reason was thinking they were an earlier casting... They are 71 thru 73, I was thinking they were 67 but you are correct.

 

[Jerry Hall]

It's all about the spring pressures and what's required on your selected cam. Generally speaking the bigger springs will fit better with more than stock cams. I don't know which heads actually flow better, between the 346's and the 516's.

 

[R413]

Combination!! that’s what it’s all about.

How far down are your pistons?
How big is your cam?
how do you drive the car?

The bigger exhaust valve means ZERO cruising down the road at 2500 RPM. Doesn’t come into play until higher rpms, 4000+ maybe. You need the compression to be right.

What heads are on there now?

 

[beanhead]

Yes those are just dampers, not inner springs...I'd want to test (or have tested) the spring pressures at the installed height you measured. I'd also want to know the coil bind height and clearance to the guides. Then see how that info jives with the recommendations for the cam you intend to use.

 

[BeepBeepRR]

Im looking at the Summit K6400 to replace the cam that is in the 383.. It requires larger valve springs. Comp 911-16 plus retainers and keepers. The outer diameter of the springs on the 346 heads are really close to the outer diameter of the Comp springs.

Brand:COMP Cams

Manufacturer's Part Number:911-16

Part Type:Valve Springs

Product Line:COMP Cams Valve Springs

Summit Racing Part Number:CCA-911-16


UPC:036584270188

Valve Spring Style:Standard

Number of Springs Per Valve:Single

Outside Diameter of Outer Spring (in):1.524 in.

Coil Bind Height (in):1.200 in.

Damper Spring Included:Yes

Spring Rate (lbs/in):373 lbs./in.

Inside Diameter of Outer Spring (in):1.110 in.

Valve Springs Coated:No

Quantity:Sold as a set of 16.

In-Store Pickup:Choose In-store pick-up (OH, NV, GA, TX) on our web site.

 

[33 IMP]

The 346s will flow better than the 516s, even with the bigger exhaust valves swapped in. I would make the decision based on compression ratio, do you want the 1/2-3/4 bump from the closed chamber or not.

 

[BeepBeepRR]

Combination!! that’s what it’s all about.

How far down are your pistons?
How big is your cam?
how do you drive the car?

I dont know much about the engine.. I was rebuilt but I assume standard 1967 configuration... I do believe it has stock pistons but wont know until I pull the heads. The car is a long way from being drivable.

 

[PRHeads]

I would use whichever set of heads are better suited towards the overall scope of the build.

Then put appropriate springs on whichever set of heads that is, that are a good match for whatever cam you decide to run.

That being said, the springs that are currently on the 516’s look like the stock low-po springs, that basically aren’t suitable for any aftermarket performance cam.

The springs that are currently on the 346’s might be okay for the cam of your chosing, and could be installed on the 516’s if need be.
But someone really should check to be sure the pressures and heights are correct for the cam that’s been selected.

You know how there are often posts about cams going flat?
Many times it’s because these simple steps are not followed.

 

[BeepBeepRR]

The 346s will flow better than the 516s, even with the bigger exhaust valves swapped in. I would make the decision based on compression ratio, do you want the 1/2-3/4 bump from the closed chamber or not.

I understand its a trade off either way... Bigger exhaust valves on the 346 heads but open chamber vs the smaller exhaust valves with closed chambers. I would be happy with a stock cam Its not going to be a drag car... Just a driver.

 

[BeepBeepRR]

It just seems like every damn cam I find requires larger valve springs. Even at a close to stock grind.

 

[33 IMP]

I would pull the heads before i made ANY decision on parts. You have got to know where you are, before you start. Stock 67 pistons, maybe 10 to 1? Rebuilder pistons, way down in the hole, maybe less than 8 to 1? If you arent planning on changing pistons, your current pistons WILL decide what heads you can use, and what cam will work.

 

[BeepBeepRR]

I will pull the 516's very soon and find out where I am.. Thanks for all the good info guys..

 

[beanhead]

You need to check everything. You may need to have the spring seats cut and new seals installed to work with the aftermarket stuff- maybe.

 

[beanhead]

Bean, I think he's talking about the spring diameter, not the height. I could be wrong.

Pissjiggle! You're right. I edited, thanks.

 

[BeepBeepRR]

You need to check everything. You may need to have the spring seats cut and new seals installed to work with the aftermarket stuff- maybe.

Both sets of heads appear to be rebuilt. I was looking at a Summit K6400 cam and lifter set. But it says you need comp cams 911-16 springs. I was more curious about the existing valve spring size compared to the required valve springs of the summit cam.
The existing on the 516 heads are way smaller. The 346 heads are way bigger.. This is what got me to thinking they were after market valve springs. However, that may not be true if stock springs changed with each head year to year.

 

[moparedtn]

I got a set of used, original 516's sitting on a shelf if anyone wants them...

 

[Demonic]

It just seems like every damn cam I find requires larger valve springs. Even at a close to stock grind.

That's not a bad thing. If you can find the published specs for the Comp 911-16 springs, you could compare them to your damper springs if you had a spring tester. They look like factory HP springs to me, but age and time may have rendered them useless.