black89ws6

I have a pair of 081 heads off an 87 LG4. They came off a motor that had gotten some water in the crankcase. I took them to NAPA this morning to have them sent off to be hot tanked, magnafluxed. If they come back ok, I want to port/polish them and put them on my 89 LB9, and put in a zz4 cam.

I've done many searches, and have answered some of my questions, but I'd appreciate it if anybody who reads this can "proofread" my research and let me know if I am in error.

Issue # 1: Valve lift
The stock heads can handle up to .480" lift without machining, right? What specific machining do I need to ask them to do get .510" lift from these heads?

Issue #2: Valve sizes
These heads come with 1.84"/1.50" valves, right? I can get a good performance increase by having it machined for 1.94" valves. 2.02's would fit the intake, but because of valve shrouding in a 305's bore, it would not be a gain over 1.94's, in fact maybe even a loss of power, right? What about exhaust? Is it possible to fit a larger exhaust valve? Would it be beneficial, or not?

Issue # 3: roller lifters/springs
I'll need these heads machined so the zz4 springs will fit. To do that do I just take the springs and/or spring specs to the machinist? Will the stock roller lifters be able to take the pressure of these springs without collapsing?

Lastly, do I want screw in rocker studs with this sort of combo?

Can any machine shop that machines auto parts do these types of operations, or do I need to find a machine shop that specializes in these sort of things?

Thanks

Thanks

five7kid

iTrader: (14)

For #1: Have the valve guides machined for positive sealing valve stem seals. This reduces the height of the guide so the valve can open farther before the retainer hits the top of the guide.

#2: 1.94" intake is all the engine can use effectively. Some say 1.60" exhaust help as well, but you'll have to decide if the extra expense is worth it. The ZZ4 cam has more exhaust duration, so that makes up for the less than desireable intake/exhaust flow ratio typical with factory SBC heads.

#3: You shouldn't need the spring pockets machined for those springs. But, the operation for #1 is typically done with a tool that cuts both the guide and spring seat. Shouldn't hurt anything to do it even if not necessary. Stock roller lifters will handle those springs with no problem.

Lastly, either pin the press-in rocker studs, or have the heads machined for screw-in studs.

The typical competent machine shop should be able to handle all this work. Ask them if they've done it before (most likely, they have).

black89ws6

#1 You are awesome...you even answered the question I forgot to ask (valve stem seals). Regarding that, which ones are better, teflon or viton?

#2 Excellent! 1.94's it is. Will 1.60" exhaust fit? If it will fit, and it will help, I'll let the $$$ decide. If it won't likely help, I'll skip the hassle.

#3 I think, regarding the springs, I'll just send the springs in with the heads, and let the machinist determine what's necessary to make them fit.

thanks for your help :hail:

five7kid

iTrader: (14)

You'll find camps favoring each. Which probably means they're both good.

black89ws6

I guess that means I can't go wrong

I like that kind of choice. thx again