chevy1500z71

gm lightweight castings, smog heads, such as the 882, and 992, and im sure theres plenty more, all of them are known for large chambers, small valves, and low compression. but for me, with my budget it seems like a good head being that im boosted and need low compression and i have some that came on my motor that are setup nicely.

i read they are prone to cracking, but if they aren't already cracked, is it really common to have one crack on you? what is the cause of them cracking, high rpms? would 10+ pounds of boost greatly increase my chances of cracking one? have any of you actually had one crack on you or is it more of just a myth that these heads crack, or they are already cracked when people find them most of the time becasue they have been around for 20+ years.

i have a really nice set of 992s that came on my motor and im in desperate need of a large cc chamber with a zero decked motor, flat tops and 10+ pounds of boost. the heads already have good springs, stainless valves, rockers and screw in arp rocker studs. im wondering if it is worth my time and effort to do a little bit of porting on these heads and throw them on. i REALLY dont want to have any weak link on this engine, i want it to be bullet proof and made to handle the boost unlike my last 200k mile stock motor...

thanks in advance.

and the heads i have currently are stock tbi heads. so anything is an upgrade, or in these case, about the same with a larger chamber.

AlkyIROC

A good aftermarket iron head isn't very expensive and will be better than the majority of the factory heads. If you're spending enough to put a turbo on the engine, spend a little more for an aftermarket head.

bart91406

that is probably good advice on the aftermarket heads, but if you found a good deal on stock heads with good valvetrain you could run them for now, you could even experiment with porting without too much worry about ruining some high dollar heads.
As far as the cracking goes, most of the cracks I have seen are in the bowl areas, and can usually be seen, so you will need to disassemble these heads, check them over, and probably have them magnufluxed, and hopefully you can do this before you buy them, otherwise I would just go the aftermarket route.

chevy1500z71

im sorry, i left out some very key details. when i bought the truck a few years ago it had the blower. its a whipple tbi kit, i just had it completely rebuilt and its like new, so of course i will be re using it. i bought this motor for 1400$ with the heads and all, as a complete motor, down to the carb and intake that i wont even use. my budget is very low and i still need to buy a cam which will eat up most of my budget. i think im going to do a mild port job myself, just match the ports and clean out the flash and what not and call them good for now. i can always add some after market heads later when im out of school and working a real full time job, for now, i just need my truck running so i need to get this motor in my truck soon.

i found that the failure of these heads is heat, high temps is what cracks them, not power. so if thats the case, then that will be perfectly fine as this is a daily driver, not a race car.

i already have these heads in my garage, they have been through by a machine shop, stainless valves, isky double springs, 1.6 rockers. they are ready to go, it seems like a no brainier to use them since the compression ratio with these will be right on the money, but i was just scared shitless that id put them on and have them crack on me.

they are the heads that came with this motor, they are off the motor now becasue i wanted to see the pistons being that this was a used motor, 2 races on it, it showed little to no wear on any parts. and it was easier to paint the block without the heads... i can re use arp head bolts right?

Apeiron

Remember that those heads originally got a reputation for cracking when they were used in low-compression, low-power daily driver engines.

chevy1500z71

how do you know thats the case, i think there reputation for cracking comes from the performance enthusiast trying to get away with using a stock head, or for example, low forms of racing require large cc heads only which would be mostly lightweight smog heads. they have been around for 25+ years, if they are prone to crack, after being around for that long then they would have cracked already. if i were to overheat my motor, i bet they'd crack, or if i ran the motor really hard at high rpms all day like used it in a circle track car, then maybe they'd crack. but for daily driver, i think ill be fine, or at least i hope so.

Apeiron

Because almost every time you go to rebuild a 70s smogger truck engine, it has a cracked head.

chevy1500z71

becasue if they are prone to crack, which would be from thermal shock, like a water pump failure/overheating, sure enough they will becasue they are 25+ years old and have probably been overheated/abused a few times were a heavyweight casting would have survived and still been good today. the thing is, if they aren't cracked by now, im not going to worry about it.

ljnowell

Then why did you post asking the question in the first place, if you didnt want to hear the answer. Yes they crack. In fact, when you go to torque them down they may crack then. It happens. They are junk heads in every way. If you dont care, fine, but dont say you werent warned.

bart91406

I have seen a few of these heads crack, however if you have a set that is good, and already has good valves, then you should run them. It is not like that if they do crack it will cause catostrophic engine damage! What do you have to lose.
Anyway, even though I said I have had some of these crack, I have pulled them off of perfectly good running engines cracked. What I mean by that, is although they had a crack, it was not in a place that caused any ill affects on the motor.

ljnowell

So, wanting to build a High performance engine that is boosted to 10psi, and doing it with one of the single worst heads that were ever bolted to a small block chevy? Just doesnt seem to make much sense to me. Cracks aside, why would you want to handicap an engine right off the bat with those heads? Boost or not you will not see anywhere near the full potential of the engine with those boat anchors bolted to the block.

chevy1500z71

well, i posted this on a few different forums and every other forum gave me several much more positive answers before i even saw the responses on this site. im on a tight budget and after market iron heads will cost me at least 600$, theres no way i can do that. i know it may sound cheep to you guys, but i make 9$ an hour part time, 600$ is a fortune.

i just figured since i have them i could port em myself and call it good, what do i have to loose.

but now im not sure. hard decision.

how much am i handicapping them really? it could still make well past 400hp and 500 torque

bart91406

They will deffinitely reduce the power, but if you have a good set that do not need rebuilt, are tight on funds, and going to boost it anyway, than run them. You can always upgrade later, it is not like they will be permanitely attached!

I do not know why people have to be so opinionated on this subject. I could see if you had to either buy these, or had to spend money rebuilding them, then maybe aftermarket would be the better choice. But you already have a good set, so what is the big deal?

chevy1500z71

thanks for a reasonable response. your right, i have nothing to loose. but theres one thing, i want to get the cam for the heads im using and if i get a cam for these heads it will be a smaller cam then what i could use if i got better heads.