Item Posts    Sort Order

L31 vortec heads info

 
Redbeast1
V-6 Camaros rule!
Posts: 45
Joined: 03/07
Posted: 03/15/07 08:23 PM

Does anyone know the specific differences between the varying Vortec head casting numbers ? The difference between casting numbers 12558060 and 12558062 for example.
I know the 8062 is a '98 L31 mexican head,
does the 8060 number apply to earlier dated '96 RPO L31 truck heads and are they mexican heads too ?
Also what the diff between these two stamped head casting numbers and the 10239906 heads ?
I know part 12529093 part number is a 'shipped bare head', but I don't know if it's stamped with this number.
Whats the differences between these heads and the "stock production vortec iron heads" - 885 ?  

Post Reply
oldbogie
I mow my lawn and find Chevys
Posts: 1195
Joined: 08/03
Posted: 03/16/07 12:48 PM

Your getting part numbers and casting numbers mixed up, not that you're the first to do that.

125508060 is a part number it can be made from either a 10239906 or a 12558062 casting. The difference between them is that the 906 uses hard seat inserts and the 062 uses induction hardening. Both or either makes a production L-31 truck head.

12529093 is the part number for the 12558060 head machined but bare.

Just to add to the fun GMPP has released part numbers 25534421 and 25534431. These are Vortec style heads with heavier casting thicknesses and 2.02/1.55 inch valves. They accept higher lifts without modification and feature a 180 cc intake for the 421 and 210 cc intake for the 431. These are complete ready to run heads, they are also available under a different P/N as machined but bare. The original Vortec "060" heads all use 1.94/1.50 valves with a 165-170 cc intake port.

Keep in mind that as ports and valves get bigger bottom thru mid RPM torque diminishes while top end horsepower goes up  both in the RPM range and in amount. So select based upon how the engine is used and where it runs (RPM wise) most of the time.

Bogie  

Post Reply
Redbeast1
V-6 Camaros rule!
Posts: 45
Joined: 03/07
Posted: 03/16/07 07:56 PM

Thanks for clearing that up Bogie.
I'm going for low end torque since my beast is a 4X4. I won't be gettin the 2.02 /1.6 valves or doing a whole lot of porting on these heads.
What would you recommend I have a machine shop do to these before I install them, - if anything. I've heard I can have the exhaust side ported lightly go get a little more power out of them. I don't want to lose any low end on these so I'll leave the intakes alone. I was also thinking about having the press-in 3/8 studs pulled and getting these tapped for screw-in studs.
I was going to have these cleaned & magnafluxed while they're at it.
Should I get the heads surfaced to make sure they're true ?  deburr & CC the chambers too.  

Post Reply
oldbogie
I mow my lawn and find Chevys
Posts: 1195
Joined: 08/03
Posted: 03/19/07 09:39 AM

Are you buying new or used heads?

If you want the best torque the 125508060 head is the best choice. Any porting usually (that means like 99% of the time) reduces torque and adds top RPM horsepower.

Replacing the press in studs requires the pedistal be machined down then the remaining hole is tapped, this is a maching operation best done by a competent shop. I like doing this and converting to guide plates which leads to replacing the self aligning rockers with conventional rockers and hardened pushrods. This reduces the work the valve stem and guides have to do which adds to their longevity.

Games you can play without porting are certainly more duration and lift with the cam, but this also reduces lower to mid torque and adds upper end HP. 1.6 rockers on a standard cam make the lift curve more robust, this tends to push the torque and HP curves up the rev range a little.

A big asset to lower end torque is small diameter long tube headers. 1-1/2 to 1-5/8s tubes 36 inches long will build a strong lower end torque curve. Tri "Y" headers are even better at this.

Bogie  

Post Reply
Redbeast1
V-6 Camaros rule!
Posts: 45
Joined: 03/07
Posted: 03/19/07 08:57 PM

I've already got these heads - new not used. Ordered part is the 125508060 you mentioned. stamped casting number is 125508062.
Based on your recomendations I won't be doing any porting on these so I don't lose low-end torque. I'll just have the machine shop do some deburring and light smoothing. I'm also going to have the studs tapped by a reputable machine shop before I get them installed.
I was also thinking of having the heads cc'd so I have accurate numbers on the combustion chambers. I know they can range from 64cc to 68 cc based on the imprecise casting process.

I'm also looking at Fel-pro head gaskets for these heads - 1014 type rated at 4.200 bore & .039 thickness. An alternative would be the 1003 type at 4.166 bore & .041 thickness.
(350 Gen-I SBC )
Will the smaller number compressed gasket thickness hurt low end torque in any significant way, in your opinion ?

I've already got 1-5/8 long tube headers installed on this truck. I couldn't afford the Thorley Tri-Y's I really wanted - maybe next time.  

Post Reply
oldbogie
I mow my lawn and find Chevys
Posts: 1195
Joined: 08/03
Posted: 03/20/07 10:50 AM

for how you're using this engine, I think cc'ing the chambers is overkill, as is anything else except putting in studs.

I don't know what rockers you're using, self aligning can be used without pushrod guides but they wear pretty hard on the valve guides and stems, though with stock springs this isn't too much of a problem, but with high lift cama and stiff springs changing these is a must. Non-self aligning rockers require pushrod guides and hardened pushrods but they work with high lifts and stiff springs.

The thinner the head gasket the higher the compression and conversley. High compression develops better power both torque and horsepower, but is cam and fuel limited. A short duration cam likes compression around 8 and a fraction to about 9.5. As the cam gets above 220 degrees @ .050 lift compression needs to move up toward 10 to recover lost bottom end torque.

Bogie  

Post Reply
Redbeast1
V-6 Camaros rule!
Posts: 45
Joined: 03/07
Posted: 03/20/07 08:35 PM

I hear what you're saying but I'm an overkill sort of dude. I looked at a few machine shops and for a $40.00 cost to cc the heads I figure I'll get it done and know what the actual combustion chamber volumes are. I'm a stickler for technical detail in case you hadn't noticed.
The studs will run about $100.00 to get tapped - not bad either to get them done right in my opinion. I know comp has a little neato tool for $28.00 to pop out the pressed in ones and acts as an accurate guide for the 3/8 tap.
I really don't want to practice making 3/8 taps on my new heads.
I'm thinking of going with the stock gmpp 1.5 self aligning rockers for now - part 12495490, and the stock springs and push-rods.

Once I get my cam installed ( comp part 12-239-3 )  218 intake duration at .050,  262 duration at .006 tappet lift. - I'll be looking at the upgrading the head's gear to comp's - Magnum 1.52 ratio Roller rockers - 1417-16, magnum hardened .080" walled pushrods 7372-16 and pushrod guides, and the 26915 beehive springs. So, you would recommend I go with comp's stainless steel valves as well ?

Comp still claims that there is an advantage in faster rpm response with their 1.52 roller rockers over factory non-roller rockers, and their web site lists a "15 to 30 hp gain over factory rockers" due to reduced friction and heat, maximum lift, and no flex over the stock stamped steel rockers. I know this is probably sales hype but the "less friction & heat" part makes sense to me. I'm not sure about the 'faster rpm response' claims. I also like the fact that most of this hardware is 8620 chromemoly steel, and should stand up to a beating.
What are your thoughts on this ?  

Post Reply
oldbogie
I mow my lawn and find Chevys
Posts: 1195
Joined: 08/03
Posted: 03/22/07 05:00 PM

I think you need to consider what you need to do to the engine with your budget. Now I have no idea what if any financial restrictions you have, but most guys are slicing cost against what needs to be done pretty close. So they can't afford to do unnecessary things and miss those of substance. But the magazines and the advertisements have folks running around doing the inconsequential at the cost of the consequential.

In that light, I'm concerned about what you’re doing versus what you need to be doing.

Your cam selection has a lift that is mighty close to what the 060 Vortec head will tolerate. I would recommend that you have the top of the valve guides relieved to insure that there is space at max lift for the bottom of the spring retainer to avoid collision with the top of the valve guide.

These type considerations need to come in advance of sweating a couple cc's difference in chamber volume, especially if you’re budget constrained. If you do the static compression math, you'll find the chamber variation affects compression ratio at about .25 of one percent. When one considers that flow in the intake manifold at WOT is 25% less for those cylinders drawing off the low side plane compared to those sucking off the high side, it's clear that .25% difference in compression ratio is well inside the noise level of all the problems needed to be solved. While the potential for slamming the spring retainers into the guides ain't a just “Whistling Dixie” kind of problem.

Going back to the vagaries of intake flow, it's amazing how much time, effort and expense goes into porting heads to get 230-250 CFM out of a port that connects to a manifold that can only deliver 170 CFM on that runner. Another example of doing the ineffective thing is grinding the forging flash off the sides of stock rods and putting a polish on in the hopes of adding strength to them. In nearly 50 years of blowing up engines, I’ve never seen one broken rod that I can point to and say forging flash on the side of the shank caused the failure. Yet lots of time gets used to shine these things up. So go figure? Besides, a stock “pink” rod no matter what you do to it will never be a racing component, at least not for long.

The effect of 1.52 roller rockers versus 1.5 factory rockers is negligible under 6000 RPM. You need some pretty stiff springs and lots of revs before there's enough flex and friction in the components to cause a loss of power. The valve springs getting tired will have a much larger effect much sooner that the rockers. You also have to appreciate the beating the guides and valve stems take with stiff springs, high lift, and high revs with self aligning rockers. This wears the guides and stems pretty hard which results in oil being pulled down the guides which contaminates the intake charge lowering octane rating of the fuel and coking the backside of the valves which disrupts and reduces flow into and out of the engine.

Bogie  

Post Reply
zman123
Everything in my driveway’s a Chevy
Posts: 537
Joined: 06/08
Posted: 09/06/08 03:57 PM

How much lift will stock 9906 vortec heads take without getting work done to them? They are "interim" heads to use while I figure out what's causing my Edelbrock RPM heads to keep sucking intake gaskets and causing oil consumption (a whole other story) the cam in the engine is the Edelbrock 2209 Roller .462/.469 lift at valve  

Post Reply
TO TOP