Hello fellas...Well I've got the stock 454 engine out, and was pretty close to just slapping in a new cam and intake and calling it good. But I've decide to go with an engine rebuild kit by Sealed Power out of Summit. I'm looking at the Hyper kit which states with .30 over bore and heads with 116.9cc will equal 10.37:1 compression. From what I was told in past posts...I'm at about 8:1 compression. My heads are stock "781's". Instead of .30 over I'm wanting to go a little more like .40 over. I will be using a Comp Cams XE274. I really want to take advantage of the heads if I'm gonna go with a re-build. I was wondering what things if any that I could change or do to help eliminate the chance of spark knock...other than racing fuel. Also I'm not sure what the difference is between the Hyper & Forged pistons. This car will be driven on the street but not daily. I really appreciate all the feedback I've received in past posts, and look forward to more. Thanks.

-Chaz

with the open chamber heads you should be able to run the 10.3:1 on quality pump gas.

Go with the .030 if you can, my 454 is .040 and there is a very limited piston selection out there.

hyper pistons are cast with higher silicon content, forged are forged, much stronger and durable, the way to go.

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I would bore it the minimum that the block requires so if you get a urge for more power there is block left. I polished my chambers and deshoured my valves to help flow but I have to run race gas. IF that is the stated compression I would measure everything. Every usually pistons listed compression is a bit high. Forged pistons are just that a chunk of aluminum forged or put under lots of pressure to form the piston. A hyper is a cast piston with a hypereutectic "above the saturation point" amount of slicone which make the pistons harder but also a bit brittle. If you really lean on it or get into detonation you will want forged. Hot street though will get by with hypers much better than cast. You want my opinion? If I was building a hot street big block I would do 2 things. 1. spend some good money on having the oval professional ported with big valves (I have $600 in mine). 2 Buy a scat 4.25 stroke cast crank (about 250 if you ($250-$300). You will never regret spending money on high flowing heads and the crank will up the cubes by 35ci. Speed pro even lists 2 hyper pistons for the crank one with about 9.5 and the other 10.2. You will spend a little more but it will run a whole lot harder. If you also consider what it will cost to get any crank work done it doesn't look so bad. As far as the heads remember what John Lingenfelter said "An engine with set of weak heads and the ideal camshaft will be a stone. But a engine with an excellent set of heads and a marginal cam shaft will still make great power" And he made some really awsome power with a oval ported 9.5 to 1 496 (4.310 bore 4.25 stroke). Just how I'd do it.

I second 80'427.

The three things that make power are cubic inches, high flow heads/intake/exhaust, and compression ratio. A good Scat cast steel crankshaft is the cheapest route to power without exception. Unless you're running stock exhaust manifolds, you're really missing a lot without upgrading your heads by porting them or replacing them with high flow parts. Assuming you're running headers and an intake like the Performer RPM, you're probably losing between 50 & 100 horsepower and even more torque if the heads are left stock! I made this mistake for years with BBCs, and let me pass on a lesson I wish I learned a long time ago. Going to honest high flow heads is like going from a V6 to a high performance V8. It's an unbelievable difference. You're a little on the radical side going above 10:1 with iron heads, but with aluminum heads this is no big deal.

If you're in sticker shock looking at $1000 heads, keep in mind that other than nitrous or forced induction, it's like adding two more cylinders to your engine and it's just as drivable.

Anyone with experience to the contrary please speak up, but this is my experience. I sure wish I understood this years ago.

Thanks for the replies....I was still wondering what could be done regarding potential spark knock...thanks again.

-Chaz

<font face="Arial,Verdana" size="2">Originally posted by Douglas Staley:
You're a little on the radical side going above 10:1 with iron heads, but with aluminum heads this is no big deal.</font>
I'm running iron heads with 11:1 compression and race gas. For the street (pump gas) I'd go no higher than 9:1. 9.5:1 would be pushing pump gas.


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<font face="Arial,Verdana" size="2">Every usually pistons listed compression is a bit high.</font>

I agree with that. Using the numbers from your combo, an undecked block (.020" piston deck height), a Fel Pro .039" head gasket and a piston with fairly massive 25cc domes you're still only at a true 9.75:1.

Those are some good factory heads! I'd pocket port them and unshroud the valves.

Also, have you checked into Northern Auto Parts rebuild kits? They are the cheapest and use quality parts.

You may also consider stroking it to a 496 or 505! The more cubes the better. http://www.nastyz28.com/ubb/biggrin.gif