Some DOHC measurements, valves, springs, etc

[SappySE107]

This may be of use to those looking for aftermarket parts, or just curious for some odd reason. I am posting this here since I found a few text files I had from measuring my 60V6 parts.

Valve Spring
1.680" length
1.1705" OD Bottom
0.8435 ID Bottom
0.968" OD top
0.631" ID top

Retainer
0.9825" wide
0.430" tall
D 0.583
B 0.506
A 0.9825

Lifter
1.301" Inside width
1.375" Outside width
0.496" Spring depth

Cam
1036

1.743" lobe total
1.654" Lobe minus backside notch
0.089" depth notch

1.376" Base Circle diameter

1.057" Core

0.812" Distance between lobes (at the tip)

Cam
1038

1.745" lobe total
1.668" Lobe minus backside notch 1.692" Thinnest
0.077" depth notch 0.053" thinnest

1.376" Base Circle diameter

1.082" Core

0.478" Distance between lobes (at the tip)

[DreX]

Thanx for the research Ben. Good work.

[haasguy]

Ben,

Do you have any measurements off the '92 heads as far as the cc's go. After milling my heads down I'd like to see what compression ratio I'm at now.

[SappySE107]

54 cc, others have figured 55 cc.

[SappySE107]

More useless info since im looking at cam specs. Max lift with the retainer hitting the valve seal is .488. The stock springs can go under 1" before going solid, and nico had .060" shims so I guess its safe to go at least .970. That would also mean stock springs support a .430 lift. Im looking for good springs to not need shims.

Stock lifters weigh 77.1 grams empty. Filled with water it weighs 84.1 grams. Im gonna look for water weight to volume formulas and see what it is in there for the hell of it:P Ill weigh it with some 10W30 in a bit and edit this post. Area in the lifter is 7 cubic centimeters, that was easy. 1 gram = 1 cu cm

[SappySE107]

Ok, im going to bed soon, but i had some fun with the digital scale. Stock keepers (2) weigh 2.5 grams, and the cap weighs 13.2 grams. Maybe ill find some lighter caps. Been wondering about changing to a different lock/cap/valve setup anyway.

[DreX]

What about the 91-93 spings max cam lift posibility?? Since they are more stronger than 96+, then that could be a posibility upgrade for 96+ engines.

DreX

[SappySE107]

You should be able to run a .430 cam without shims and be fine. .400 is definetly fine, its between 430 and 400 that im not 100% on. They are stronger than the 96+ and the new GM part number, so I would use them for sure between the 2.

[pocket-rocket]

I wonder if .400 would be a bad thing with valve float. I guess if it hit, it could be considered something like a mechanical anti valve float tool, lol. All joking aside, I wonder how far a valve travels when the engine reaches valve float limits on stock parts if you kept a 7150 rpm limit.

[Corpse]

"I wonder how far a valve travels when the engine reaches valve float limits on stock parts if you kept a 7150 rpm limit."

I don't understand? When valve float occurs, that means the spring is not strong enough to meet the valve timing requirements.

So if you could have .700 lift without coil bind, it would be perfectly fine regardles of spring strength. Valve float is the opposite effect of the vavle being opened, when it is being closed, the valve float occurs if the valve spring is under pressured and the valve does not go as fast as the cam lobe. So, the valve does not close as fast as it should. Which means, a valve and piston could collide. Which is why you need stronger springs to support more lift at higher RPMs.

Coil bind and valve float of a spring are two majorly different factors that must be used with each other to detemine the capabilites of the spring. Whereas, coil bind is for max lift, alothough there must be a certain amount of clearance, the coils must NEVER touch or else the spring will fail. Valve float is regardless of lift although, the more lift, the more chance of valve float.

Valve float could occur with very little lift at high RPMS or very high lift at low RPMs. Valve float is just another term for under-rated springs that don't expand as fast as they have been contracted, due to low strength of the spring.

basically, you can Rev your motor as high as you want and the float will not occur until the valve is returning to be seated. Although, there may be a certain negligible amount that the valve is thrown down beyond the cam lift, due to the springs being under the necessary pressure. But, this is negligible to the amoutn of time the valve stays more open than it should be.

Also, 7150 RPMs is beyond stock internal limits, you should not go beyond 7000 RPMs or you will have connecting rod/bearing failures. You will get rod knock. EDIT: These are not my own words. GM states that All 660 motors use the same rods, which are rated up to 7K RPMS. Although, I know that there have been different rods used, GM doesn't, it seems.

-Dave

[Corpse]

Although, one thing I believe to be misleading, is how the 3.4 DOHC passed emission certification at 7K RPMS. Well, before it was detuned.

So, the bottom end may be balanced for over 7K RPMS but, I highly doubt it, due to the fact that the whole motor was detuned thanks mostly to GM's hydra-Matic division and there lack to be able to seriously beef up a transmission. And also probably due to manufacturing restrictions.

The 3.4 DOHC can be built up to be a crazy powerplant though.

-Dave

[SappySE107]

i thought 7500 was done on stock internals. It wouldnt be too hard to make this engine spin much higher. Im wondering what the valve spring rating should be for an engine with different cams, lifters, valves, and the springs. Along with finding info on determining correct intake/exhaust flow ratio on heads, info on valve spring pressure would be nice.

[jmgtp]

I believe it was Mike Smith (did tdc fiero swap) that spun up to 8k rpm on a 96 engine with shims. I think he was maxing power around 7400 though. I dont recall him ever reporting bottom end failures.

[pocket-rocket]

For some reason I thought valve float was where the spring did not keep the valve under enough tension when opened, letting the valve open more then the lift of the cam. EI .370 lift cam, say at 9k rpms (well say it's a Honda, lol), and the valve opens to say .400. That is what I thought valve float was. I do see what you mean what valve float is, so thank you for clearing that up for me.

[SappySE107]

That would be inertia and the ramp of the cam, and severely underrated springs.