Hyper's are decent - many new cars use them. If you were going for big hp and/or boost/NOS they'd be worth the upgrade. But you'd probably want to consider a forged crank then also.. And stronger rods... and on and on.
CK5
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GEN 1 SMALLBLOCK QUESTIONS
- Thread starter 4xfrankie
- Start date
.040" is considered ideal quench. Anything more or less is not ideal and can contribute to problems like detonation. It's not a guarantee that it will magically make everything good, but quench has a large impact and it's easy to control, so no reason not to get it right when designing an engine.
Deck height (apparently properly called compression height) is simply how far into the bore the piston does or does not sit....so zero deck height means the piston top is flush with the deck surface. Then you add in gasket thickness.
Being stuck with components, if the valves hit the pistons, yes relieving them is the only way I'm aware of to fix that issue. Otherwise you'd reduce cam lift or change the pistons.
As mentioned before about the aftermarket heads...be careful sinking a ton of money into old factory heads. If you end up replacing valves, springs, pinning studs, surfacing, going with larger valves, and/or having to install hardened seats (i assume that's not an issue here, but it can be based on age of the heads) you can spend a significant amount of money on old-tech heads that are costing you power.
Summit lists all sorts of aftermarket heads, some are down into the $800 range now, complete. Screw in studs, new valves, springs, flat surfaces, no cracks, etc. If it's all about money, using stock heads probably makes sense. But if you can come up with a bit more money, aftermarket heads (or even Vortecs) are worth a fair bit of power, and generally have better components. Most testing I've seen shows about 25HP gain with Vortecs over older heads on mild/stock 350's.
Edit: BTW, in the hierarchy of piston material, it's cast->hyper->forged Hypers will hold up no problem. Anything beaten on bad enough will break, if your engine is detonating, the problem isn't the piston material.
I don't turn my engine really high (4000RPM) but I routinely hit the rev limiter there. It did detonate a bit before I got the timing and fueling right, no ill-effects on the pistons. Obviously I didn't run it hard like that, but what they were subjected to, they held up fine.Do I need big ports to make low end torque
Nope, that,s whenIgo 383ci ,going to find a 1 piece rear main seal block with provisions for a roller cam for that engine, but that's later. Right now I'm just using stock components for the bottom end., with the exception of the pistons/rings . The cast crank and the stock forged rods will be good for the power level I am shooting for.(350hp /400ft lbs of torque) Idon't expect to get that much with 882 heads ,but ,later on I'll find some vortecs.I am having this engine squared to the world with top notch machining, should last forever.
I'd run more compression if I thought I could find 91-93 octane everywhere with this expedition vehicle, but sometimes places like caseys is all your stuck with in small towns out in the middle of nowhere, and they only sell87 octane. I'd like to get some EdelbrockEtec or similar aluminum head ,they say all things being eqeul you can run a point more compression for agiven octane rating of fuel and get a lot more power as aresult..040" is considered ideal quench. Anything more or less is not ideal and can contribute to problems like detonation. It's not a guarantee that it will magically make everything good, but quench has a large impact and it's easy to control, so no reason not to get it right when designing an engine.
Deck height (apparently properly called compression height) is simply how far into the bore the piston does or does not sit....so zero deck height means the piston top is flush with the deck surface. Then you add in gasket thickness.
Being stuck with components, if the valves hit the pistons, yes relieving them is the only way I'm aware of to fix that issue. Otherwise you'd reduce cam lift or change the pistons.
As mentioned before about the aftermarket heads...be careful sinking a ton of money into old factory heads. If you end up replacing valves, springs, pinning studs, surfacing, going with larger valves, and/or having to install hardened seats (i assume that's not an issue here, but it can be based on age of the heads) you can spend a significant amount of money on old-tech heads that are costing you power.
Summit lists all sorts of aftermarket heads, some are down into the $800 range now, complete. Screw in studs, new valves, springs, flat surfaces, no cracks, etc. If it's all about money, using stock heads probably makes sense. But if you can come up with a bit more money, aftermarket heads (or even Vortecs) are worth a fair bit of power, and generally have better components. Most testing I've seen shows about 25HP gain with Vortecs over older heads on mild/stock 350's.
Edit: BTW, in the hierarchy of piston material, it's cast->hyper->forged Hypers will hold up no problem. Anything beaten on bad enough will break, if your engine is detonating, the problem isn't the piston material.
They've pretty well shot that theory down I think. Aluminum dissipates heat so well that you need higher compression to *equal* iron heads in power output.
Only real benefits to AL are weight savings and being easier to repair than cast iron. I'm running about 9.4:1 compression on mine (edit: mine are iron Vortecs) with 87, but I've also got a knock sensor just in case.
Only real benefits to AL are weight savings and being easier to repair than cast iron. I'm running about 9.4:1 compression on mine (edit: mine are iron Vortecs) with 87, but I've also got a knock sensor just in case.
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That's why I mentioned those summit heads. I had a couple of rocker studs pull out of some crap smogger heads. By the time I got screw in studs, along w/ the machining needed, the basics on them would have been almost 300 a head.... so $339 assembled and shipped was a much better deal... And I don't have a ton of miles on them, but so far they work.
You can get away with running un-leaded gas on old non-hardened seat heads. It is not optimal, but I have done it, and gotten away over 100,000 miles on an old leaded gas engine doing it. The average off-the-shelf flat top piston will have 4-valve reliefs, and a .20 inch deck to piston top clearance. With your #882 / 76cc heads this previously mentioned piston should put you in the 8.75:1 compression range. You will not have to worry about valves hitting the piston with the average off the shelf flat top piston. It would take a radical cam to do that, and not your average RV cam.
As already mentioned, anything more than pinning the rocker studs with this set of #882 heads, is not worth the money. You could put that money towards a better set of heads. To run an RV cam like I advised...you would have to use longer slot rocker arms, and pinned in rocker studs at minimum. As you can see from the responces you have gotten, ther is more to consider when building an engine than you would think.
As already mentioned, anything more than pinning the rocker studs with this set of #882 heads, is not worth the money. You could put that money towards a better set of heads. To run an RV cam like I advised...you would have to use longer slot rocker arms, and pinned in rocker studs at minimum. As you can see from the responces you have gotten, ther is more to consider when building an engine than you would think.
F-ingrob
Wheres the mud
i agree with this guy the heads are good just need a little work go with 1.60 roller rockers f your gonna go roller so you can get more lift to get more low end power cast rings are ok and break in faster molley rings take a long time cast pistons are fine if you going some what stock and your not going into high rpms to much hypereutectic pistons are fine and better than cast and will last longer as long as you dont run hot in temp
F-ingrob
Wheres the mud
also you should get the rotating mass balanced if your gonna be grinding on the rods
Yes, balancing is a given,on any rebuild ,regardless of grinding the rods or not. You have to when you replace the pistons.Forgot to mention that.
Will upgrade to 1.6 roller rockers,not going roller cam as of now. My machinist has informed me that you must use the right honing stones in the cylinders to insure proper/quick break in with the molly rings.I think the stock cast crank and the factory rods can handle the added power output as I upgrade the engine with better heads at a later date .However ,I want the added insurance and piece of mind of going hypereutectic pistons over cast.They don't cost that much more. I would get a whole forged bottem end if it was cost effective,even though I don't need it at this power level, I tend to be very hard on my equipment.
This is my first engine build,but I ain't scared! I am doing the most research I can , and truly appreciate the info that I get here from fellow chevy enthusiasts. The 882 heads are going to be used to break in the engine,and after that, I will upgrade to better heads and cam later on ,after the engine is driven and I know all is well with the short block, and I get more money . The next novice question I have is about the use of plasti -guage to measure bearing clearance-is it accurate?
Yes, plasti-gauge is just fine for your average street build. I used it every time on my engines with no problem. I just recently used plasti-gauge to get the clearance on an anti-cam walk button, for an engine I am building now.
GREAT, I really don't want to buy inside and outside micrometers and other tools till later. I do have feeler gauges to measure to ring end gaps ,and the like.Well, I think that about sums up all of my questions,thanks again for every ones input. Feel free to add anything that I might have missed.
Stomis
Professional Amateur
They've pretty well shot that theory down I think. Aluminum dissipates heat so well that you need higher compression to *equal* iron heads in power output.
Only real benefits to AL are weight savings and being easier to repair than cast iron. I'm running about 9.4:1 compression on mine (edit: mine are iron Vortecs) with 87, but I've also got a knock sensor just in case.
Do you have an article that supports that? Id be really interested in reading it.
Ive never heard that one before. I have read and heard all the theory that equal amounts compression iron heads will make more power given the exact same head design because the more even heat makes for a more even flame front, but I have never once heard that the 1-1.5 pts of compression you can pick up with aluminum heads will equal less power than what you're loosing in the more stable flame front.
This is what I could find that was a pretty good test: http://www.hotrod.com/how-to/engine/ccrp-0602-iron-versus-aluminum-cylinder-heads-test/
At least based on that article I'm incorrect about the material. Iron or AL of equal design make nearly identical power at the same compression ratio.
I wish they would have bumped the compression up a point and re-tested though.
AL advantages are weight savings and repair. No disadvantage. Not really going to go wrong with either one, UNLESS the AL is more resistant to detonation. I tend to think that not true either, if power output is the same. but would like to see that disproved too.
Stomis
Professional Amateur
This is what I could find that was a pretty good test: http://www.hotrod.com/how-to/engine/ccrp-0602-iron-versus-aluminum-cylinder-heads-test/
At least based on that article I'm incorrect about the material. Iron or AL of equal design make nearly identical power at the same compression ratio.
I wish they would have bumped the compression up a point and re-tested though.
AL advantages are weight savings and repair. No disadvantage. Not really going to go wrong with either one, UNLESS the AL is more resistant to detonation. I tend to think that not true either, if power output is the same. but would like to see that disproved too.
Its a blurred line IMO. Aluminum heads became a mainstay in a time when reverse flow cooling and chamber shape innovation were pushing the limits of detonation. I think the aluminum certainly aids in getting heat out easier but the reverse flow and chamber design is what made pump gas limits get pushed.
F-ingrob
Wheres the mud
aluminum heads build more power by running cooler as well as port design and chamber
you dont have to run higher compression to cast heads
hyper eutectic pistons are just fine they dont fall apart and forged pistons can be noisy and will wear the cylinders faster than stock pistons or hyper eutectic pistons
my machine shop/engine builder and good friend is Rescino Performance they race sprint cars and hold many track records that still have not been beat and have the record for the most wins in a race season not saying this to make it sound like they are never wrong but they should know what they are talking about
they built my motor and its a low RPM touque beast and has great low RPM horse power it made 384 at the tires with 492 torque on pump gas with hyper eutectic pistons
you dont have to run higher compression to cast heads
hyper eutectic pistons are just fine they dont fall apart and forged pistons can be noisy and will wear the cylinders faster than stock pistons or hyper eutectic pistons
my machine shop/engine builder and good friend is Rescino Performance they race sprint cars and hold many track records that still have not been beat and have the record for the most wins in a race season not saying this to make it sound like they are never wrong but they should know what they are talking about
they built my motor and its a low RPM touque beast and has great low RPM horse power it made 384 at the tires with 492 torque on pump gas with hyper eutectic pistons
Is it due to the fact that the hyper pistons expand more than forged, and so they run tighter in actual operating conditions?
