Heads and bores

[Guest Anonymous]

I've pretty much decided to go with my

350, but it has open chamber heads.

 

Anybody know of some good heads that I can get relatively cheap?

 

Are vortec heads off of the new trucks

(silverado, tahoe, Yukon, ect) any good?

How about Sportsman II heads?

I need something inexpensive but still good.

I can get the vortec heads from a near-by junkyard that has some new trucks that had been totalled.

 

I'm going to get the northern auto parts

street performance kit with the hyperuectic

pistons (what do forged pistons have on these anyway?)

 

Also, the block is in good enough condition to us standard Pistons/rings/bearings, because it only had 40k on it when the donor car was parked. Should I go with std bore or is another bore better?

[pparaska]

My opinions on these questions:

 

Heads: If you are on a budget and don't mind the 40-45 lb weight difference, get the Vortecs. But realize that they can benefit from a pocket porting and need better springs and some guide trimming for much more than stock lift/duration.

 

Forged vs Hypereutectic: If you are not going to turbo/supercharge or not do lots of Nitrous, then the Hypers are nice. Otherwise, the added toughness of Forged is worth the insurance.

 

If you can stay standard on the bores with acceptable size and taper after a clean-up honing, then stay there. The advantage to 5 cubic inches is negligible, and the block will be rebuildable later and worth more later if you sell it.

 

Hope that helps,

[BLKMGK]

Forged vs Hyper - I'll add my .04

 

Hyper pistons have more silicone in them and come from a different process - a casting that's struck if I recall correctly. As a result they end up being more "brittle" than a true forging - this is bad. They can run a tighter piston to bore clearance since they don't expand as much as forgings. This is a good thing!

 

The brittleness means that they do not have the detonation tolerance and cannot withstand the higher cylinder pressures that a true forging can. If you're not going into that territory this is a "throw away".

 

For these reasons these pistons are better for low to medium horsepower naturally aspirated engines. Medium being pretty high for a street car BTW so don't freak. Run NOS on them and you may find the ring lands in pieces - happened to somone I know running KB Hypers. Run a turbo or supercharger and if it detonates any you could again find pieces floating around. Also under very high cylinder pressures, even with correct mixtures, Hypers can have the silicone migrate out of the piston in what looks like blisters. This occured on a Turbo magazine project car and isn't something I'd expect from a modern Hyper piston to be honest.

 

Hypers are as popular as they are because they're cheaper and because of the tighter clearances that can be run. OEMs have switched to them due to this but the OEM pistons are supposedly not as good as the aftermaket ones. Mustangs with Hyper pistons trash them somewhat regularly when certain HP bounds are crossed. Tigher clearances help with emissions and with cold startwarmup "piston slap" - this is what the OEMs are after.

 

Lastly, note that some pretty fast turbo cars came with CAST pistons! The Buick GN is a good example and I'll bet the current Lightning has Hypers or cast pistons. Hyper pistons, so long as you know the limitations, are perfectly good. Having said that I ordered Forged for insurance. Watch the weight of whatever piston you order - some of the aftermarket forged ones weigh a ton

[Mike C]

BLKMGK makes some excellent points. The Buicks only have 4 bolts per cylinder and tend to blow head gaskets before breaking pistons. This is not true for the Typhoon/Syclone which have the small blocks 5 bolts per cylinder and they are always breaking pistons. The OEMs can't tolerate the slightly looser tolerances of forged pistons because of emissions on startup as well as noise requirements.

 

For my money I would run the forged pistons. The TRW forgings have a high silicone content and run tighter clearances than some others. I have several sets and have had no troubles with piston slap on startup.

 

As far as heads, spend the absolute maximum you are willing to. You can get the Vortecs new for about $400 a pair and buy an intake. If you go junkyard (Why at $400?)make sure and not get the Vortec 5.0 heads that have smaller combustion chambers. I don't like the reduced intake bolts in the Vortec heads as I know several people who have had leaky intakes. I would run the Dart SR with 2.02 valves as a cheap head, but honestly, for a couple hundred bucks more you could get a set of Trick Flow aluminum heads.

[Guest Anonymous]

I agree, the Hyper pistons are up to the task for normally aspirated motors. I have heard the same thing on a few turbo sites, that Hyper pistons don't like detonation much at all and will come apart if subjected to NOS or Forced induction.

If its a 400+ HP normally aspirated small block, then I'd have no problem running hyper pistons, chevy does in several of its crate motors with success. Bottom line, buy the best parts you can afford and build it with durability in mind and you'll be a happy camper with it.

 

Regards,

 

Lone

[Guest Anonymous]

I think I'll get the hyper pistons

and save 150 bucks, hehe.

 

Is a 4.8 vortec from a 2000

Silverado a good head??

[Lone Star 1]

The 2000 GM 4.8 L motor is an LS1 motor. I am not sure if they work older designed motors. But the 2000 4.8 L LS1 motor makes about 270FWHP.They are designed for FI.

[z ya]

I have some 64 cc fuelie heads, casting #291

for sale. These heads have had a fresh 3 angle valve job, comp cams springs,pocket

ported. They have no more than 10 miles on them. All work was done by Rex Hutchson

Racing in Sacramento,Ca. I want 250 for them

and you wold have to pay for shipping.

[Guest Anonymous]

If you still have those heads by the time I get around to that in my budget, I'll want them.

 

Well, I'm off to get my project car from Georgia.

[Guest jens]

I would choose the hyper pistons for a everyday car and forged for a weekend warrior. I have tried venolia racing pistons in a 4 banger. I had only 5 miles to work so it sounded like a diesel most of the time damn irretating and it used more oil than a 110000 mile engine because of the bigger tolerances then cold.